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RSS2011 Vol. 23, No. 02
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2011,
23.
Abstract:
Based on the unified theory of coherence and polarization of stochastic electromagnetic beams and propagation law of the cross-spectral density matrix, and regarding Young’s interference experiment as a double-slit diffraction phenomenon, changes in the degree of polarization of Hermite-Gaussian(H-G) electromagnetic beams in Young’s interference experiment are studied in consideration of the finite width of the double slits, especially the effect of polarization, self- and cross-correlation lengths, mode order of incident H-G electromagnetic beams and obscure ratio of the double slits on the degree of polarization at the observation screen. It is shown that the degree of polarization at the observation screen increases with increasing degree of polarization at the double-slit plane and c
Based on the unified theory of coherence and polarization of stochastic electromagnetic beams and propagation law of the cross-spectral density matrix, and regarding Young’s interference experiment as a double-slit diffraction phenomenon, changes in the degree of polarization of Hermite-Gaussian(H-G) electromagnetic beams in Young’s interference experiment are studied in consideration of the finite width of the double slits, especially the effect of polarization, self- and cross-correlation lengths, mode order of incident H-G electromagnetic beams and obscure ratio of the double slits on the degree of polarization at the observation screen. It is shown that the degree of polarization at the observation screen increases with increasing degree of polarization at the double-slit plane and c
2011,
23.
Abstract:
In order to validate the energy law of similitude for conical nozzles under the irradiation of single laser pulse predicted by analysis, a numerical simulation belonged to the radiation gasdynamics scope is used to calculate propulsion performance parameters for a set of different nozzle sizes, and the effect of cone angle, generatrix length, the dimensionless factor introduced in theory, and incident laser energy on impulse and impulse coupling coefficient is gained, respectively. The energy law of similitude got by simulation is right, since qualitative conclusions are consistent with those derived by theoretical analysis and laboratory study in the scope that can be described by the analysis models. The results show that, impulse and impulse coupling coefficient firstly increase and the
In order to validate the energy law of similitude for conical nozzles under the irradiation of single laser pulse predicted by analysis, a numerical simulation belonged to the radiation gasdynamics scope is used to calculate propulsion performance parameters for a set of different nozzle sizes, and the effect of cone angle, generatrix length, the dimensionless factor introduced in theory, and incident laser energy on impulse and impulse coupling coefficient is gained, respectively. The energy law of similitude got by simulation is right, since qualitative conclusions are consistent with those derived by theoretical analysis and laboratory study in the scope that can be described by the analysis models. The results show that, impulse and impulse coupling coefficient firstly increase and the
2011,
23.
Abstract:
The kHz satellite laser ranging (SLR) system can effectively obtain a large quantity of observation data by laser emission at high repetition rate. Based on the kHz experiment at the Wuhan SLR station, the paper introduces the ranging method and the operation principle of kHz laser, and analyzes the influencing factors of echo detection in high repetition frequency. The experimental results show that the data quantity is increased by 1 to 2 orders of magnitude, and the single measurement precision is improved for the medium earth orbit and low earth orbit satellite tracking observations．
The kHz satellite laser ranging (SLR) system can effectively obtain a large quantity of observation data by laser emission at high repetition rate. Based on the kHz experiment at the Wuhan SLR station, the paper introduces the ranging method and the operation principle of kHz laser, and analyzes the influencing factors of echo detection in high repetition frequency. The experimental results show that the data quantity is increased by 1 to 2 orders of magnitude, and the single measurement precision is improved for the medium earth orbit and low earth orbit satellite tracking observations．
2011,
23.
Abstract:
A high average output power， high slope efficiency acousto-optical Q-switched 1 064 nm laser is reported with a laser diode (LD) endpumped Nd:YVO4 double-bonded crystal scheme. With the proper estimation of thermal lensing effects under intense pumping, the mode matching and thermally stable cavity parameters are discussed and optimized, and a stable high-power highslope efficiency output is obtained. At the highest repetition rate of 50 kHz and pump power of 46.8 W, a maximum average output power of 17.6 W is achieved with optical conversion efficiency of 37.6%, slope efficiency of 70.1% and pulse width of 513 ns. At the lowest repetition rate of 10 kHz, a maximum single pulse energy of 0.91 mJ and peak power of 46.2 kW are measured with pulse width of 19.8 ns.
A high average output power， high slope efficiency acousto-optical Q-switched 1 064 nm laser is reported with a laser diode (LD) endpumped Nd:YVO4 double-bonded crystal scheme. With the proper estimation of thermal lensing effects under intense pumping, the mode matching and thermally stable cavity parameters are discussed and optimized, and a stable high-power highslope efficiency output is obtained. At the highest repetition rate of 50 kHz and pump power of 46.8 W, a maximum average output power of 17.6 W is achieved with optical conversion efficiency of 37.6%, slope efficiency of 70.1% and pulse width of 513 ns. At the lowest repetition rate of 10 kHz, a maximum single pulse energy of 0.91 mJ and peak power of 46.2 kW are measured with pulse width of 19.8 ns.
2011,
23.
Abstract:
High efficiency extra-cavity third harmonic generation (THG) of 355 nm beam has been developed. A laser diode（LD） end-pumped, acoustic optical Q-switched Nd:YAG laser was used as the fundamental wave source. With an input pump power of 25 W, the average power of 6.2 W at 1 064 nm was generated with the repetition rate of 12 kHz. Using the extra cavity frequency conversion of three critical phase match LiO3O5 (LBO) crystals, 2.7 W third harmonic radiation at 355 nm was obtained. The optical to optical (1 064 nm to 355 nm) conversion efficiency was up to 43.5%．
High efficiency extra-cavity third harmonic generation (THG) of 355 nm beam has been developed. A laser diode（LD） end-pumped, acoustic optical Q-switched Nd:YAG laser was used as the fundamental wave source. With an input pump power of 25 W, the average power of 6.2 W at 1 064 nm was generated with the repetition rate of 12 kHz. Using the extra cavity frequency conversion of three critical phase match LiO3O5 (LBO) crystals, 2.7 W third harmonic radiation at 355 nm was obtained. The optical to optical (1 064 nm to 355 nm) conversion efficiency was up to 43.5%．
2011,
23.
Abstract:
Based on the plano-concave resonator, a new way to choose a branch of wavelength is reported. A laser with 9.3 μm single-line output is attained by using a high average power TEA CO2 laser and the existing optical coating technology. The single pulse energy and average power are basically the same as those of the original single 10.6 μm output. It is found that the laser spots attained by shooting the heat-sensitive paper with the same laser pulse energy at 9.3 μm and 10.6 μm are significantly different. A two-wavelength windows switching device is designed, which can realize free switching between 10.6 μm and 9.3 μm lasers at the same output power level on one laser. The switch position error is less than 5″, and the sealing performance meets the requirements.
Based on the plano-concave resonator, a new way to choose a branch of wavelength is reported. A laser with 9.3 μm single-line output is attained by using a high average power TEA CO2 laser and the existing optical coating technology. The single pulse energy and average power are basically the same as those of the original single 10.6 μm output. It is found that the laser spots attained by shooting the heat-sensitive paper with the same laser pulse energy at 9.3 μm and 10.6 μm are significantly different. A two-wavelength windows switching device is designed, which can realize free switching between 10.6 μm and 9.3 μm lasers at the same output power level on one laser. The switch position error is less than 5″, and the sealing performance meets the requirements.
2011,
23.
Abstract:
A novel multi-limit unsymmetrical iterative blind deconvolution (MLIBD) algorithm was presented to enhance the performance of adaptive optics image restoration. The algorithm enhances the reliability of iterative blind deconvolution by introducing the bandwidth limit into the frequency domain of point spread function (PSF), and adopts the PSF dynamic support region estimation to improve the convergence speed. The unsymmetrical factor is automatically computed to advance its adaptivity. Image deconvolution comparing experiments between Richardson-Lucy IBD and MLIBD were done, and the result indicates that the iteration number is reduced by 22.4% and the peak signal-to-noise ratio is improved by 10.18 dB with MLIBD method. The performance of MLIBD algorithm is outstanding in the images resto
A novel multi-limit unsymmetrical iterative blind deconvolution (MLIBD) algorithm was presented to enhance the performance of adaptive optics image restoration. The algorithm enhances the reliability of iterative blind deconvolution by introducing the bandwidth limit into the frequency domain of point spread function (PSF), and adopts the PSF dynamic support region estimation to improve the convergence speed. The unsymmetrical factor is automatically computed to advance its adaptivity. Image deconvolution comparing experiments between Richardson-Lucy IBD and MLIBD were done, and the result indicates that the iteration number is reduced by 22.4% and the peak signal-to-noise ratio is improved by 10.18 dB with MLIBD method. The performance of MLIBD algorithm is outstanding in the images resto
2011,
23.
Abstract:
Radiation forces of a focused partially coherent Gaussian Schell-model (GSM) vortex beam used to trap Rayleigh dielectric spherical particles with different refractive indices are analyzed, where the dependence of radiation forces and trapping stability on the correlation length and waist width is stressed and illustrated by numerical examples. There exist critical values for the correlation length and waist width of the GSM vortex beam. The particles with relative refractive index larger than one can be trapped by the beam with waist width less than critical width or correlation length larger than critical length, while the particle with relative refractive index less than one can be trapped by the beam with waist width larger than critical width or correlation length less than critical l
Radiation forces of a focused partially coherent Gaussian Schell-model (GSM) vortex beam used to trap Rayleigh dielectric spherical particles with different refractive indices are analyzed, where the dependence of radiation forces and trapping stability on the correlation length and waist width is stressed and illustrated by numerical examples. There exist critical values for the correlation length and waist width of the GSM vortex beam. The particles with relative refractive index larger than one can be trapped by the beam with waist width less than critical width or correlation length larger than critical length, while the particle with relative refractive index less than one can be trapped by the beam with waist width larger than critical width or correlation length less than critical l
2011,
23.
Abstract:
To avoid heat shocks in the operation, the choice of resonator expanding angle should be considered in the design of the supersonic chemical oxygen-iodine laser. The influence of the expanding angle on inner flow field of the laser has been numerically investigated based on a kilowatt laser experiment setup. To define a proper expanding angle which has the ability to keep constant pressure and temperature through the resonator, different angles have been analyzed in the view of flow parameters and chemical gain. The relationship between the nozzle height and expanding angle has also been studied. Numerical result shows that the proper expanding angle of the kilowatt is 4.5°.
To avoid heat shocks in the operation, the choice of resonator expanding angle should be considered in the design of the supersonic chemical oxygen-iodine laser. The influence of the expanding angle on inner flow field of the laser has been numerically investigated based on a kilowatt laser experiment setup. To define a proper expanding angle which has the ability to keep constant pressure and temperature through the resonator, different angles have been analyzed in the view of flow parameters and chemical gain. The relationship between the nozzle height and expanding angle has also been studied. Numerical result shows that the proper expanding angle of the kilowatt is 4.5°.
2011,
23.
Abstract:
Based on the Fokker-Planck equation, a theoretical computational model is established to describe the change with time of the energy distribution of conduction electrons in a dielectric material under the irradiation of short laser pulses. Using this model, the evolution of electron density in a dielectric material (taking SiO2 glass as an example) is calculated; with the critical plasma density damage criterion, the material damage thresholds are determined for various laser wavelengths and pulse durations. For laser wavelengths of 1 060, 800 and 532 nm, the obtained damage threshold curves of SiO2 are rather close to each other. The role of impact ionization and photoionization in material damage is also investigated. It is found that when the laser pulse duration is greater than 1 ps, i
Based on the Fokker-Planck equation, a theoretical computational model is established to describe the change with time of the energy distribution of conduction electrons in a dielectric material under the irradiation of short laser pulses. Using this model, the evolution of electron density in a dielectric material (taking SiO2 glass as an example) is calculated; with the critical plasma density damage criterion, the material damage thresholds are determined for various laser wavelengths and pulse durations. For laser wavelengths of 1 060, 800 and 532 nm, the obtained damage threshold curves of SiO2 are rather close to each other. The role of impact ionization and photoionization in material damage is also investigated. It is found that when the laser pulse duration is greater than 1 ps, i
2011,
23.
Abstract:
Using quasi-monochromatic light interference theory, the far-field interference pattern is calculated for the combination of 2×2 flat-topped Gauss ultrashort-pulse lasers, and the effect of phase difference (PD) and temporal partial coherence on coherent combination is discussed. The results show that when the line-width of the beams is less than 100 nm, the far-field pattern and peak light intensity hardly change for ideal wavefront; when the line-width is more than 100 nm, the interference effect weakens gradually. With phase difference, the periodic variation of far-field pattern will be destroyed by temporal partial coherence, and the interference effect gradually becomes weak as the increment of PD. Incoherent combination appears for PD beyond coherent length, while the combination c
Using quasi-monochromatic light interference theory, the far-field interference pattern is calculated for the combination of 2×2 flat-topped Gauss ultrashort-pulse lasers, and the effect of phase difference (PD) and temporal partial coherence on coherent combination is discussed. The results show that when the line-width of the beams is less than 100 nm, the far-field pattern and peak light intensity hardly change for ideal wavefront; when the line-width is more than 100 nm, the interference effect weakens gradually. With phase difference, the periodic variation of far-field pattern will be destroyed by temporal partial coherence, and the interference effect gradually becomes weak as the increment of PD. Incoherent combination appears for PD beyond coherent length, while the combination c
2011,
23.
Abstract:
Operation principle of holographic modal wavefront sensor was obtained indirectly by investigating the output response characteristics of the mode-biased wavefront sensor and by associating the holographic multiplexing method with mode-biased one. The theoretical analyses and summaries on the mode-biased wavefront sensor resulted in the construction of simplified model, and verification to theoretical results was achieved by numerical simulation for several Zernike aberrations. The numerical simulation shows that, output signals of the sensor have different relationships with the amplitude of different types of tested aberrations, which is consistent with theory. To detect the spots intensity in the focal plane, the tested and biased aberrations, for instance the defocus mode, were dynamic
Operation principle of holographic modal wavefront sensor was obtained indirectly by investigating the output response characteristics of the mode-biased wavefront sensor and by associating the holographic multiplexing method with mode-biased one. The theoretical analyses and summaries on the mode-biased wavefront sensor resulted in the construction of simplified model, and verification to theoretical results was achieved by numerical simulation for several Zernike aberrations. The numerical simulation shows that, output signals of the sensor have different relationships with the amplitude of different types of tested aberrations, which is consistent with theory. To detect the spots intensity in the focal plane, the tested and biased aberrations, for instance the defocus mode, were dynamic
2011,
23.
Abstract:
By expanding the window function of double-slit aperture into a finite sum of complex Gaussian functions and from the Collins formula, the approximate analytical propagation equation of Gaussian-Schell model (GSM) beams passing through Young’s double silts and ABCD optical system is derived. The validity region of the approximate analytical formula is given by comparing the results obtained from the analytical formula with those from the Collins formula. The effect of the spatial correlation length of GSM beams and the central obstruction ratio of Young’s double slits on the validity region of the approximate analytical formula is studied, and the application prospect of the formula is also presented.
By expanding the window function of double-slit aperture into a finite sum of complex Gaussian functions and from the Collins formula, the approximate analytical propagation equation of Gaussian-Schell model (GSM) beams passing through Young’s double silts and ABCD optical system is derived. The validity region of the approximate analytical formula is given by comparing the results obtained from the analytical formula with those from the Collins formula. The effect of the spatial correlation length of GSM beams and the central obstruction ratio of Young’s double slits on the validity region of the approximate analytical formula is studied, and the application prospect of the formula is also presented.
2011,
23.
Abstract:
An undersized humidity detecting system based on infrared spectrum absorption is introduced. A vertical-cavity surface-emitting laser is used as the light source and provides lasers at 1.854 μm which is a main absorption peak of water vapor. To cover all humidity condition, vapor density is detected via two different methods, which are switched by the system automatically depending on measure results. In low-density condition, the ratio of the second-harmonic to fundamental signal is used to eliminate the interference due to light power variation. A/D conversion with over-sampling and digital lock in amplification enhance the accuracy of signal processing, and with IEEE 802.11x protocol, automatic remote data acquisition is achieved.
An undersized humidity detecting system based on infrared spectrum absorption is introduced. A vertical-cavity surface-emitting laser is used as the light source and provides lasers at 1.854 μm which is a main absorption peak of water vapor. To cover all humidity condition, vapor density is detected via two different methods, which are switched by the system automatically depending on measure results. In low-density condition, the ratio of the second-harmonic to fundamental signal is used to eliminate the interference due to light power variation. A/D conversion with over-sampling and digital lock in amplification enhance the accuracy of signal processing, and with IEEE 802.11x protocol, automatic remote data acquisition is achieved.
2011,
23.
Abstract:
The change of chemiluminescence in visible range in the optical cavity flow field of HF laser for different flow rates of D2 was observed and recorded, and spectra of the chemiluminescence on the optic axis were measured using the spectrometer calibrated with 632.8 nm and 543.5 nm He-Ne lasers. The components of the gas in the optical cavity were analyzed theoretically, and the high order overtone spectral lines of DF molecule and spectral lines of D atom were computed. The comparison of the measured spectra of chemiluminescence and the spectral lines shows that, the chemiluminescence is formed by the radiation of excited F, He, D, N atoms and DF, N2 molecules, and the excited state of other particles. The colour formation of the chemiluminescence on the optic axis wa
The change of chemiluminescence in visible range in the optical cavity flow field of HF laser for different flow rates of D2 was observed and recorded, and spectra of the chemiluminescence on the optic axis were measured using the spectrometer calibrated with 632.8 nm and 543.5 nm He-Ne lasers. The components of the gas in the optical cavity were analyzed theoretically, and the high order overtone spectral lines of DF molecule and spectral lines of D atom were computed. The comparison of the measured spectra of chemiluminescence and the spectral lines shows that, the chemiluminescence is formed by the radiation of excited F, He, D, N atoms and DF, N2 molecules, and the excited state of other particles. The colour formation of the chemiluminescence on the optic axis wa
2011,
23.
Abstract:
A dual-beam laser Doppler velocimeter (LDV) with Janus configuration was put forward, in order to reduce the effect of vehicles vibration on measurement accuracy of the conventional dual-beam LVD. Theory analysis and simulation of the relative error of measurement show that the pitch angle can be calculated approximately by Janus configuration technique, and then the velocity can be compensated. The precision of the conventional dual-beam LDV is much affected by the pitch angle, whereas the Janus-based system is relatively insensitive to it. In Janus-based system, the relative error of velocity measurement is less than 0.2%, when the ratio between vehicle velocity in vertical direction and that in horizontal direction equals to 0.01 and the pitch angle is smaller than 10.
A dual-beam laser Doppler velocimeter (LDV) with Janus configuration was put forward, in order to reduce the effect of vehicles vibration on measurement accuracy of the conventional dual-beam LVD. Theory analysis and simulation of the relative error of measurement show that the pitch angle can be calculated approximately by Janus configuration technique, and then the velocity can be compensated. The precision of the conventional dual-beam LDV is much affected by the pitch angle, whereas the Janus-based system is relatively insensitive to it. In Janus-based system, the relative error of velocity measurement is less than 0.2%, when the ratio between vehicle velocity in vertical direction and that in horizontal direction equals to 0.01 and the pitch angle is smaller than 10.
2011,
23.
Abstract:
Laser induced breakdown spectroscopy (LIBS) has been used to analyze the concentration of potassium in compound fertilizer. Self-absorption was prone to appear in the formation process of plasma because of the high-content potassium in samples. The atomic spectral line 404.40 nm of potassium was determined as the optimized line by analyzing the excitation energy, transition probability and self-absorption of spectral lines. Experimental stability with different average numbers of pulses was discussed, and the results indicated that the average measurement of 100 pulses had a lower relative standard deviation. Nine samples were analyzed and seven of them were tested to establish the calibration curve of measured concentration of K2O. The linear fitting degree of the calibration curve was 0.989 and the measured concentration of K2O in the other two samples was well consistent with the corresponding reference concentration with an absolute error of less than 0.3%.
Laser induced breakdown spectroscopy (LIBS) has been used to analyze the concentration of potassium in compound fertilizer. Self-absorption was prone to appear in the formation process of plasma because of the high-content potassium in samples. The atomic spectral line 404.40 nm of potassium was determined as the optimized line by analyzing the excitation energy, transition probability and self-absorption of spectral lines. Experimental stability with different average numbers of pulses was discussed, and the results indicated that the average measurement of 100 pulses had a lower relative standard deviation. Nine samples were analyzed and seven of them were tested to establish the calibration curve of measured concentration of K2O. The linear fitting degree of the calibration curve was 0.989 and the measured concentration of K2O in the other two samples was well consistent with the corresponding reference concentration with an absolute error of less than 0.3%.
2011,
23.
Abstract:
The character and micro-process of cavitation erosion by laser-generated bubble near a rigid boundary in water have been studied with high speed camera system. The experimental results indicate that the main reasons for the boundarys erosion are the bubble collapse-generated shock wave and high speed liquid jet. When the dimensionless quantity, the ratio of the distance from the bubble to the boundary to the maximum radius of the bubble, is from 0.4 to 1.4, the first erosion to the boundary is from the shock wave and the second is from the high speed liquid jet because of the bubbles movement to the surface. When the dimensionless quantity is 1, the liquid jet is the decisive factor of erosion.
The character and micro-process of cavitation erosion by laser-generated bubble near a rigid boundary in water have been studied with high speed camera system. The experimental results indicate that the main reasons for the boundarys erosion are the bubble collapse-generated shock wave and high speed liquid jet. When the dimensionless quantity, the ratio of the distance from the bubble to the boundary to the maximum radius of the bubble, is from 0.4 to 1.4, the first erosion to the boundary is from the shock wave and the second is from the high speed liquid jet because of the bubbles movement to the surface. When the dimensionless quantity is 1, the liquid jet is the decisive factor of erosion.
2011,
23.
Abstract:
Starting from the coupled mode equations, the influence of modulation depth errors on the properties of apodized chirped fiber Bragg grating(ACFBG) is investigated theoretically by using a matrix method. The results show that the errors of low frequency distribution deteriorate the performance of ACFBG much more than the errors of high frequency distribution with the same amplitude level, and the errors of higher amplitude level lead to more performance degradation. Therefore, errors of both low frequency distribution and high amplitude level should be avoided in the fabrication of the fiber grating.
Starting from the coupled mode equations, the influence of modulation depth errors on the properties of apodized chirped fiber Bragg grating(ACFBG) is investigated theoretically by using a matrix method. The results show that the errors of low frequency distribution deteriorate the performance of ACFBG much more than the errors of high frequency distribution with the same amplitude level, and the errors of higher amplitude level lead to more performance degradation. Therefore, errors of both low frequency distribution and high amplitude level should be avoided in the fabrication of the fiber grating.
2011,
23.
Abstract:
Finite difference time domain (FDTD) method is used to simulate the incident light scattered by planar cracks with triangular cross-section on fused silica and Nd-doped phosphate glass surfaces. When the incident light is TE mode, the maximum electric field is in the glass. When the incident light is TM mode, the maximum electric field locates inside the crack. The maximum electric field enhancement located at output surface is much higher than that at input surface for both modes. Cracks under TE illumination lead to the maximum electric field when the incident light is totally internally reflected by the crack and by the surface successively. The maximum electric field on rear surface increases with either larger crack width or deeper crack depth.
Finite difference time domain (FDTD) method is used to simulate the incident light scattered by planar cracks with triangular cross-section on fused silica and Nd-doped phosphate glass surfaces. When the incident light is TE mode, the maximum electric field is in the glass. When the incident light is TM mode, the maximum electric field locates inside the crack. The maximum electric field enhancement located at output surface is much higher than that at input surface for both modes. Cracks under TE illumination lead to the maximum electric field when the incident light is totally internally reflected by the crack and by the surface successively. The maximum electric field on rear surface increases with either larger crack width or deeper crack depth.
2011,
23.
Abstract:
By constructing a wave-front distortion phase with random phase screen, the distortion correction effect of deformable mirror has been simulated and analyzed with the method of high-pass filtering. The variations of the correction effect with low frequency and high frequency phase distortions have been quantitatively analyzed. The influence of the correction location of deformable mirror has been also discussed. It is found that for a deformable mirror of given size, the quality of the corrected beam degrades obviously in far field with the percent of high frequency phase distortion increasing. In addition, the correction effect varies obviously with the mirror location.
By constructing a wave-front distortion phase with random phase screen, the distortion correction effect of deformable mirror has been simulated and analyzed with the method of high-pass filtering. The variations of the correction effect with low frequency and high frequency phase distortions have been quantitatively analyzed. The influence of the correction location of deformable mirror has been also discussed. It is found that for a deformable mirror of given size, the quality of the corrected beam degrades obviously in far field with the percent of high frequency phase distortion increasing. In addition, the correction effect varies obviously with the mirror location.
2011,
23.
Abstract:
Numerical simulations are conducted on the scheme of energetic proton-bunch driven plasma wakefield acceleration and the possibility of the selfinjection scenario in proton-bunch driven plasma wakefield acceleration by using a density transition of plasma with the help of 2D3V PIC code. The simulations show that enhanced selfinjection of electrons in the scenario is realized successfully. It is found that the number of trapped particles increases as the amplitude of density transition increases．
Numerical simulations are conducted on the scheme of energetic proton-bunch driven plasma wakefield acceleration and the possibility of the selfinjection scenario in proton-bunch driven plasma wakefield acceleration by using a density transition of plasma with the help of 2D3V PIC code. The simulations show that enhanced selfinjection of electrons in the scenario is realized successfully. It is found that the number of trapped particles increases as the amplitude of density transition increases．
2011,
23.
Abstract:
The principle of a photon sieve applied to soft X-ray spectroscopy is introduced, and the transmittance of the photon sieve is calculated. The diffraction pattern of the photon sieve is simulated and measured in visible light wave band. It is shown that the dispersive component has good single order diffraction properties, i.e. the third order and higher order diffraction can be suppressed effectively. The photon sieve applied to soft X-ray spectroscopy can realize self-sustaining easily compared with the conventional transmission grating and single-order diffraction grating designed before, and it might be employed widely for X-ray and extreme ultraviolet spectroscopic diagnoses.
The principle of a photon sieve applied to soft X-ray spectroscopy is introduced, and the transmittance of the photon sieve is calculated. The diffraction pattern of the photon sieve is simulated and measured in visible light wave band. It is shown that the dispersive component has good single order diffraction properties, i.e. the third order and higher order diffraction can be suppressed effectively. The photon sieve applied to soft X-ray spectroscopy can realize self-sustaining easily compared with the conventional transmission grating and single-order diffraction grating designed before, and it might be employed widely for X-ray and extreme ultraviolet spectroscopic diagnoses.
2011,
23.
Abstract:
Based on the third order aberration theory, the optical system of an EUV Schwarzschild microscope is designed for laser plasma diagnostics. The microscope works at 18.2 nm with the numerical aperture of 0.1 and the magnification of 10. The optical system is optimized to achieve the spatial resolution of 0.3 μm in the center field and about 0.4 μm in the field of ±1 mm. The influences of Schwarzschild system tolerances are analyzed in the aspects of system assembly, alignment and components fabrication. The results show that the optics surface irregularity is the main factor affecting imaging resolution; by improving the accuracy of system alignment, the deterioration of resolution, resulting from imaging distance tolerance, and the spacing and the curvature radius tolerances of objectiv
Based on the third order aberration theory, the optical system of an EUV Schwarzschild microscope is designed for laser plasma diagnostics. The microscope works at 18.2 nm with the numerical aperture of 0.1 and the magnification of 10. The optical system is optimized to achieve the spatial resolution of 0.3 μm in the center field and about 0.4 μm in the field of ±1 mm. The influences of Schwarzschild system tolerances are analyzed in the aspects of system assembly, alignment and components fabrication. The results show that the optics surface irregularity is the main factor affecting imaging resolution; by improving the accuracy of system alignment, the deterioration of resolution, resulting from imaging distance tolerance, and the spacing and the curvature radius tolerances of objectiv
2011,
23.
Abstract:
To diagnose the gas-puff pinch plasma at wavelength range from 0.3 to 0.5 nm, a space-resolved curved crystal spectrometer has been developed based on Mica(002) crystal with Bragg angel of 37°. In experiments carried out on the Yang accelerator, X-ray spectra in an absolute intensity scale were obtained from argon gas-puff pinch plasmas, which were recorded by a 30 mm×80 mm flat film. The measured wavelength was consistent with the theoretical value, and the He-like spectral resolution was 200 to 300 for the mica crystal spectrometer, showing its potential in the analysis of X-ray emission from a gas-puff pinch plasmas source.
To diagnose the gas-puff pinch plasma at wavelength range from 0.3 to 0.5 nm, a space-resolved curved crystal spectrometer has been developed based on Mica(002) crystal with Bragg angel of 37°. In experiments carried out on the Yang accelerator, X-ray spectra in an absolute intensity scale were obtained from argon gas-puff pinch plasmas, which were recorded by a 30 mm×80 mm flat film. The measured wavelength was consistent with the theoretical value, and the He-like spectral resolution was 200 to 300 for the mica crystal spectrometer, showing its potential in the analysis of X-ray emission from a gas-puff pinch plasmas source.
2011,
23.
Abstract:
With the development of optical systems for multi-wavelength and wide-angle range, there is a requirement of the antireflection coating with wide-spectrum and wide-incidence angle range. In this paper, the substrate is super-smooth ZF6 (rms less than 0.6 nm) glass and HfO2 and SiO2 are selected as high index and low index materials, respectively. The broadband antireflection coating is designed, for wavelength form 600 to 1 200 nm and incidence angle of 0° to 30°. The influences of refractive index inhomogeneity, error of refractive index and error of layer physical thickness on its transmittance are analyzed. Ion beam sputtering deposition of time-power thickness monitoring is used to manufacture the antireflection coating and the each layer thickness systematic co
With the development of optical systems for multi-wavelength and wide-angle range, there is a requirement of the antireflection coating with wide-spectrum and wide-incidence angle range. In this paper, the substrate is super-smooth ZF6 (rms less than 0.6 nm) glass and HfO2 and SiO2 are selected as high index and low index materials, respectively. The broadband antireflection coating is designed, for wavelength form 600 to 1 200 nm and incidence angle of 0° to 30°. The influences of refractive index inhomogeneity, error of refractive index and error of layer physical thickness on its transmittance are analyzed. Ion beam sputtering deposition of time-power thickness monitoring is used to manufacture the antireflection coating and the each layer thickness systematic co
2011,
23.
Abstract:
The effects of the period and amplitude of micro-waveness on KDP surface processed by single point diamond turning(SPDT) on the refractive index, thickness, and transmittance of single-layer anti-reflection (AR) coating were analyzed by the Fourier modal method. It is found that the optimal refractive index of the AR film is about 1.22, and the thickness should be 180 to 220 nm in order to ensure the transmittance of more than 99% in the optimal refractive index condition. The period and amplitude of micro-waveness on the surface of KDP crystal do not generally affect the values of the optimal refractive index and the reasonable thickness range of single-layer AR coating. Just considering the practical range of the period and amplitude of micro-waveness, the transmittance is not affected b
The effects of the period and amplitude of micro-waveness on KDP surface processed by single point diamond turning(SPDT) on the refractive index, thickness, and transmittance of single-layer anti-reflection (AR) coating were analyzed by the Fourier modal method. It is found that the optimal refractive index of the AR film is about 1.22, and the thickness should be 180 to 220 nm in order to ensure the transmittance of more than 99% in the optimal refractive index condition. The period and amplitude of micro-waveness on the surface of KDP crystal do not generally affect the values of the optimal refractive index and the reasonable thickness range of single-layer AR coating. Just considering the practical range of the period and amplitude of micro-waveness, the transmittance is not affected b
2011,
23.
Abstract:
Based on the mechanism of magnetorheological finishing, the dwell time function was solved by Jansson-Van Cittert algorithm to accomplish the kernel module design. Then the software modularization programming, modular testing and integration testing were conducted. A verification experiment was carried out on a crystal element with full aperture of 500 mm and the element’s surface achieved rapid and efficient convergence after the software controlled magnetorheological finishing. It is proved that the software could control the whole polishing process accurately.
Based on the mechanism of magnetorheological finishing, the dwell time function was solved by Jansson-Van Cittert algorithm to accomplish the kernel module design. Then the software modularization programming, modular testing and integration testing were conducted. A verification experiment was carried out on a crystal element with full aperture of 500 mm and the element’s surface achieved rapid and efficient convergence after the software controlled magnetorheological finishing. It is proved that the software could control the whole polishing process accurately.
2011,
23.
Abstract:
A technique based on contact pressure compensation is presented in order to quicken the convergence of surface of large-aperture optical components during the pre-polishing processes. The pad surface is conditioned to a specific shape using an innovative pad conditioning technique, and thus the non-uniform distribution of contact pressure will be engendered at the interface between workpiece and polishing pad. Combining with accurate polishing speed controlling, the uneven pressure distribution will make workpiece’s surface converge to the desired shape more quickly, which was verified by our experiments. The experiments also indicate that conditioning pad surface to convex can avoid excessive removal of workpiece edge region during the early stages of polishing process. Compared to the t
A technique based on contact pressure compensation is presented in order to quicken the convergence of surface of large-aperture optical components during the pre-polishing processes. The pad surface is conditioned to a specific shape using an innovative pad conditioning technique, and thus the non-uniform distribution of contact pressure will be engendered at the interface between workpiece and polishing pad. Combining with accurate polishing speed controlling, the uneven pressure distribution will make workpiece’s surface converge to the desired shape more quickly, which was verified by our experiments. The experiments also indicate that conditioning pad surface to convex can avoid excessive removal of workpiece edge region during the early stages of polishing process. Compared to the t
2011,
23.
Abstract:
Bismuth plating was obtained on copper substrate by using pulse electroplating in cyanide-free system. The optimal pulse parameters were determined by orthogonal test as follows: current density 5 A/cm2, frequency 600 Hz, duty ratio 1∶6, temperature 20 ℃. Furthermore, scanning electron microscope and scanning probe microscope were used to characterize the morphology of the bismuth plating, and X-ray diffraction was used to analyze the phase components. The bismuth plating has fine and uniform grains, with low porosity, good smoothness and free of cracks.
Bismuth plating was obtained on copper substrate by using pulse electroplating in cyanide-free system. The optimal pulse parameters were determined by orthogonal test as follows: current density 5 A/cm2, frequency 600 Hz, duty ratio 1∶6, temperature 20 ℃. Furthermore, scanning electron microscope and scanning probe microscope were used to characterize the morphology of the bismuth plating, and X-ray diffraction was used to analyze the phase components. The bismuth plating has fine and uniform grains, with low porosity, good smoothness and free of cracks.
2011,
23.
Abstract:
A double-nozzle emulsion particle generator is developed to synthesize monodispersed ICF capsules. The working principle of the generator, the key designed parts, and idea for it are described. With this set-up, the reliability of double-layer particle encapsulation is increased simply by adjusting the concentricity of the three-layer tubes at the nozzle. Initial experiments show that monodispersed double-layer emulsion particles can be easily synthesized, and the flow-velocity ratio of oil phase to water phase, at which double-layer emulsion particles would be formed, ranges from 0.3 to 15.0.
A double-nozzle emulsion particle generator is developed to synthesize monodispersed ICF capsules. The working principle of the generator, the key designed parts, and idea for it are described. With this set-up, the reliability of double-layer particle encapsulation is increased simply by adjusting the concentricity of the three-layer tubes at the nozzle. Initial experiments show that monodispersed double-layer emulsion particles can be easily synthesized, and the flow-velocity ratio of oil phase to water phase, at which double-layer emulsion particles would be formed, ranges from 0.3 to 15.0.
2011,
23.
Abstract:
Collisional effects on the kinetics of interactions between an ultrahigh intensity subpicosecond laser and a solid carbon thin foil are investigated in the scenarios of laser-driven particle acceleration and fast ignition by one-dimensional particle-in-cell simulations. It is found that collisional effects play an essential role in hot electron generation and transport in the early transient time by slowing down the return current which supplies resistive heating, compared with collisionless cases. Qualitatively, collisional effects reduce hot electron production and its maximum energy, and suppress energy transport. However, when recirculation (or refluxing) processes become the major transport mechanism in later time, the two cases have less difference.
Collisional effects on the kinetics of interactions between an ultrahigh intensity subpicosecond laser and a solid carbon thin foil are investigated in the scenarios of laser-driven particle acceleration and fast ignition by one-dimensional particle-in-cell simulations. It is found that collisional effects play an essential role in hot electron generation and transport in the early transient time by slowing down the return current which supplies resistive heating, compared with collisionless cases. Qualitatively, collisional effects reduce hot electron production and its maximum energy, and suppress energy transport. However, when recirculation (or refluxing) processes become the major transport mechanism in later time, the two cases have less difference.
2011,
23.
Abstract:
H-plane and E-plane tapered wedge-shaped severs were designed and analyzed by electromagnetic simulation software. The result shows that the matching of the E-plane tapered wedge-shaped sever is better, and the reflected electromagnetic wave mostly results from the place of the centralized electric field, i.e. the sharp end of the wedge-shape for both kinds of severs. A deformed sever is designed based on the E-plane tapered severed. The simulation and experiment results show that, the matching of the deformed sever is much better than that of the H-plane and E-plane tapered wedge-shaped severs near the cut-off frequency.
H-plane and E-plane tapered wedge-shaped severs were designed and analyzed by electromagnetic simulation software. The result shows that the matching of the E-plane tapered wedge-shaped sever is better, and the reflected electromagnetic wave mostly results from the place of the centralized electric field, i.e. the sharp end of the wedge-shape for both kinds of severs. A deformed sever is designed based on the E-plane tapered severed. The simulation and experiment results show that, the matching of the deformed sever is much better than that of the H-plane and E-plane tapered wedge-shaped severs near the cut-off frequency.
2011,
23.
Abstract:
Additional current density, which is a function of frequency, can be used to describe the effect of the ionosphere in the process of electromagnetic pulse propagation. In time domain, however, this effect can be expressed in two terms: current density and conductivity. Their time-domain expressions were derived in differential equation forms, which are the functions of ionosphere parameters and the electric field exerted. These current and conductivity were used directly in the high altitude nuclear electromagnetic pulse (HEMP) calculations, for which these computations need to be held in time domain to simulate the HEMP stimulation and propagation in the ionosphere simultaneously. As an example, three cases of the stimulation and propagation of HEMP exploded at a height of 100 km were cal
Additional current density, which is a function of frequency, can be used to describe the effect of the ionosphere in the process of electromagnetic pulse propagation. In time domain, however, this effect can be expressed in two terms: current density and conductivity. Their time-domain expressions were derived in differential equation forms, which are the functions of ionosphere parameters and the electric field exerted. These current and conductivity were used directly in the high altitude nuclear electromagnetic pulse (HEMP) calculations, for which these computations need to be held in time domain to simulate the HEMP stimulation and propagation in the ionosphere simultaneously. As an example, three cases of the stimulation and propagation of HEMP exploded at a height of 100 km were cal
2011,
23.
Abstract:
A T-junction plates-inserted waveguide-based power combiner is experimentally investigated, which is compact, easy to fabricate and has high power handing capacity. It consists of two overmoded rectangular waveguides which are connected vertically, and two perpendicular linearly polarized microwaves at 9.50 GHz and 9.60 GHz can be transmitted separately to realize incoherent power combining. Cold test shows that both channels of the combiner realize single-mode transmission effectively, and the transmission losses located at the joint are less than 0.4 dB. Hot test verifies the combiner’s GW level power handling capacity.
A T-junction plates-inserted waveguide-based power combiner is experimentally investigated, which is compact, easy to fabricate and has high power handing capacity. It consists of two overmoded rectangular waveguides which are connected vertically, and two perpendicular linearly polarized microwaves at 9.50 GHz and 9.60 GHz can be transmitted separately to realize incoherent power combining. Cold test shows that both channels of the combiner realize single-mode transmission effectively, and the transmission losses located at the joint are less than 0.4 dB. Hot test verifies the combiner’s GW level power handling capacity.
2011,
23.
Abstract:
Based on the theory of HPM propagating in mixed-atmosphere, studies are conducted on the phenomenon and principle of self-focusing/defocusing of the narrow HPM beam propagating in ionospheric plasma. The nonlinear propagating equation, and focusing/defocusing parameters have been derived with nonlinear heating effects being considered. The dependence of beam width on the frequency and intensity of HPM has been illustrated in the presence of magnetic field. Simulations show that the lower ionosphere mainly represents a defocusing medium. The divergent phenomenon occurs for L-wave, R-wave, O-wave and X-wave. And the angle of divergence is the maximum for R-wave and the minimum for L-wave. But the difference will decrease with the increase of the frequency of incident wave. Defocusing effect
Based on the theory of HPM propagating in mixed-atmosphere, studies are conducted on the phenomenon and principle of self-focusing/defocusing of the narrow HPM beam propagating in ionospheric plasma. The nonlinear propagating equation, and focusing/defocusing parameters have been derived with nonlinear heating effects being considered. The dependence of beam width on the frequency and intensity of HPM has been illustrated in the presence of magnetic field. Simulations show that the lower ionosphere mainly represents a defocusing medium. The divergent phenomenon occurs for L-wave, R-wave, O-wave and X-wave. And the angle of divergence is the maximum for R-wave and the minimum for L-wave. But the difference will decrease with the increase of the frequency of incident wave. Defocusing effect
2011,
23.
Abstract:
In most HPM devices, multipactor discharge causes gas ionization and breakdown, and yields plasmas on surface. It would induce the shortening of output HPM pulses, and seriously deteoriate the performance of HPM devices. The metal two-sided multipactor discharge was theoretically analyzed and numerically simulated. Firstly, the dynamics equations, resonant phase, focusing phase, collision potential were introduced and analyzed in theory. Depending on material characteristic of secondary emission, the susceptibility curve of two-sided multipactor discharge was discussed. Secondly, using Monte Carlo method simulating the initial emission energy and angle, the susceptibility curve of two-sided multipactor discharge was studied and discussed compared with the theoretic results. And the relatio
In most HPM devices, multipactor discharge causes gas ionization and breakdown, and yields plasmas on surface. It would induce the shortening of output HPM pulses, and seriously deteoriate the performance of HPM devices. The metal two-sided multipactor discharge was theoretically analyzed and numerically simulated. Firstly, the dynamics equations, resonant phase, focusing phase, collision potential were introduced and analyzed in theory. Depending on material characteristic of secondary emission, the susceptibility curve of two-sided multipactor discharge was discussed. Secondly, using Monte Carlo method simulating the initial emission energy and angle, the susceptibility curve of two-sided multipactor discharge was studied and discussed compared with the theoretic results. And the relatio
2011,
23.
Abstract:
A power dividing horn for the offset parabolic cylindrical reflector antenna (OPCRA) is proposed. When the horns constitute an array, the grating lobes can be suppressed to －28 dB because of the improved aperture field. Compared with the OPCRA using conventional pyramidal horn array feed, the aperture efficiency of the OPCRA fed with power dividing horn array, which is simulated by FEKO, is improved from 68% to 80%. And the gain of the OPCRA can also be increased by 0.7 dB．
A power dividing horn for the offset parabolic cylindrical reflector antenna (OPCRA) is proposed. When the horns constitute an array, the grating lobes can be suppressed to －28 dB because of the improved aperture field. Compared with the OPCRA using conventional pyramidal horn array feed, the aperture efficiency of the OPCRA fed with power dividing horn array, which is simulated by FEKO, is improved from 68% to 80%. And the gain of the OPCRA can also be increased by 0.7 dB．
2011,
23.
Abstract:
The construction features of separated function radio frequency quadrupole(SFRFQ) accelerator are presented, which include the structure of diaphragms electrodes, integral split ring supporting system, cooling system, tuning system and their manufacturing engineering. The analysis with 8753ES network analyzer proves that the tuning system works successfully to tune the SFRFQ frequency at 26.07 MHz as required by the whole acceleration system without significant quality factor declining. The Roentgen spectrum test at high power proves that the inter-vane voltage can reach higher than the design value of 70 kV. Beam commissioning was carried out to accelerate the O+ ions from 1.03 MeV to 1.65 MeV, which demonstrates that the mechanical design of SFRFQ accelerator can satisfy the e
The construction features of separated function radio frequency quadrupole(SFRFQ) accelerator are presented, which include the structure of diaphragms electrodes, integral split ring supporting system, cooling system, tuning system and their manufacturing engineering. The analysis with 8753ES network analyzer proves that the tuning system works successfully to tune the SFRFQ frequency at 26.07 MHz as required by the whole acceleration system without significant quality factor declining. The Roentgen spectrum test at high power proves that the inter-vane voltage can reach higher than the design value of 70 kV. Beam commissioning was carried out to accelerate the O+ ions from 1.03 MeV to 1.65 MeV, which demonstrates that the mechanical design of SFRFQ accelerator can satisfy the e
2011,
23.
Abstract:
This paper mainly analyzed the characteristics of nuclear physics experiments and their requirements for analog-digital converter (ADC). Based on technical index comparison of three ADC chips, ADS8472 was selected as the acquisition chip, which has 16 bit resolution and successive approximation register (SAR) framework, with differential and integral nonlinearities of ±0.50 and ±0.65 least significant bit, respectively. According to the actual circuit applications, the architecture of the pulse amplitude acquisition and analysis system was introduced, and its working principle was described. With linear power supply chip, fluctuations of the fan-out voltages were all less than 1 mV after a long-period (72 h) full-load test.
This paper mainly analyzed the characteristics of nuclear physics experiments and their requirements for analog-digital converter (ADC). Based on technical index comparison of three ADC chips, ADS8472 was selected as the acquisition chip, which has 16 bit resolution and successive approximation register (SAR) framework, with differential and integral nonlinearities of ±0.50 and ±0.65 least significant bit, respectively. According to the actual circuit applications, the architecture of the pulse amplitude acquisition and analysis system was introduced, and its working principle was described. With linear power supply chip, fluctuations of the fan-out voltages were all less than 1 mV after a long-period (72 h) full-load test.
2011,
23.
Abstract:
The RF phase control loop of the rapid cycling synchrotron (RCS) of China spallation neutron source (CSNS) is designed with an FPGA-based digitalized control system. It should be able to control the RF phase to follow the beam synchronous phase when the RF frequency is rapidly sweeping during the acceleration, which is important for the rapid acceleration and the stabilization of the beam during the acceleration cycle and for the minimization of the beam loss level. This paper presents the design and the experiments of the phase control loop system which uses an FPGA development board from ALTERA Co.. Both the desk experiments and the low-power ones with an assembled RF system show that, the phase control loop can run stably with the control error smaller than 1°, satisfying the design re
The RF phase control loop of the rapid cycling synchrotron (RCS) of China spallation neutron source (CSNS) is designed with an FPGA-based digitalized control system. It should be able to control the RF phase to follow the beam synchronous phase when the RF frequency is rapidly sweeping during the acceleration, which is important for the rapid acceleration and the stabilization of the beam during the acceleration cycle and for the minimization of the beam loss level. This paper presents the design and the experiments of the phase control loop system which uses an FPGA development board from ALTERA Co.. Both the desk experiments and the low-power ones with an assembled RF system show that, the phase control loop can run stably with the control error smaller than 1°, satisfying the design re
2011,
23.
Abstract:
Impacts of backstreaming ions on the focus of single-pulse and multi-pulse high-current relativistic electron beams were studied by solving the envelop equation. The result indicates that smaller integrated spot size could be achieved by shorten the focal distance in single pulse machine, while in multi-pulse machine, electron beam pulses would be disrupted after interaction with the long ion column. The feasibility of using foils to block the back streaming ions mechanically was also studied by both numerical simulation and experimental methods. Simulation of foil expansion after interaction with electron beam shows that although the expansion is considerable during a time scale of 1.06 μs, there is still enough material to stop the ions. Faraday cup experiment at Dragon Ⅰ linear induct
Impacts of backstreaming ions on the focus of single-pulse and multi-pulse high-current relativistic electron beams were studied by solving the envelop equation. The result indicates that smaller integrated spot size could be achieved by shorten the focal distance in single pulse machine, while in multi-pulse machine, electron beam pulses would be disrupted after interaction with the long ion column. The feasibility of using foils to block the back streaming ions mechanically was also studied by both numerical simulation and experimental methods. Simulation of foil expansion after interaction with electron beam shows that although the expansion is considerable during a time scale of 1.06 μs, there is still enough material to stop the ions. Faraday cup experiment at Dragon Ⅰ linear induct
2011,
23.
Abstract:
Both theoretical analysis and Monte-Carlo simulation on induced radioactivity in the copper measuring probe irradiated by proton beams with energy of 11 MeV and intensity of 50 μA have been demonstrated. Saturated activities of various kinds of radioactive nuclides obtained by these two methods were compared. The comparison indicates that the Monte-Carlo method conducted by software FLUKA can provide good simulation accuracy and complete consideration in nuclear reaction, and both the direct and indirect radioactivity under different irradiation time can be calculated simultaneously. The method can also provide accurate analysis and prediction on the induced radioactivity in different measuring probes under proton irradiation, which will provide a reference for design, exchange and dispos
Both theoretical analysis and Monte-Carlo simulation on induced radioactivity in the copper measuring probe irradiated by proton beams with energy of 11 MeV and intensity of 50 μA have been demonstrated. Saturated activities of various kinds of radioactive nuclides obtained by these two methods were compared. The comparison indicates that the Monte-Carlo method conducted by software FLUKA can provide good simulation accuracy and complete consideration in nuclear reaction, and both the direct and indirect radioactivity under different irradiation time can be calculated simultaneously. The method can also provide accurate analysis and prediction on the induced radioactivity in different measuring probes under proton irradiation, which will provide a reference for design, exchange and dispos
2011,
23.
Abstract:
A Mobley type bunch compressor is adopted to enhance proton intensity at the Li target hence neutron flux for the Frankfurt Neutron Source at the Stern-Gerlach-Zentrum(FRANZ). At first the micro bunches in one proton macro bunch are successively deflected by a RF chopper located at the front focus of the compressor with various angles, whereafter pass through an optimized magnetic bending system in different trajectories, and finally arrive at the end focus of the compressor, i.e. the target, simultaneously. The chopper cavity consists of a pair of opposite plates serving as a bunch deflector, connected with an inductive winding in series to stimulate resonance at 5 MHz. To design such a chopper, a scaled model is constructed to start with. Theoretical analyses of its RF properties are acc
A Mobley type bunch compressor is adopted to enhance proton intensity at the Li target hence neutron flux for the Frankfurt Neutron Source at the Stern-Gerlach-Zentrum(FRANZ). At first the micro bunches in one proton macro bunch are successively deflected by a RF chopper located at the front focus of the compressor with various angles, whereafter pass through an optimized magnetic bending system in different trajectories, and finally arrive at the end focus of the compressor, i.e. the target, simultaneously. The chopper cavity consists of a pair of opposite plates serving as a bunch deflector, connected with an inductive winding in series to stimulate resonance at 5 MHz. To design such a chopper, a scaled model is constructed to start with. Theoretical analyses of its RF properties are acc
2011,
23.
Abstract:
The pollution on electron gun ceramic insulation of electron cooler restricted the operation of electron cooler at HIRFL-CSR main ring. To cool and accumulate ion beam well, the pollution was cleared and a new oxidecoated cathode was assembled. The processes of cathode replacement, vacuum chamber baking-out, and thermal decomposition of coating binders and alkaline earth metal carbonates, and cathode activation are presented. The electron gun perveance of 10.6 μＡ/V1.5 was attained under the heating power of 60 W. The typical surface temperature of oxide-coated cathode that is calculated through grey-body radiation is 1 108 K which shows a comparable result to the experimental measurement 1 078 K. The perveance growth of electron gun during the electron cooler operation is also explaine
The pollution on electron gun ceramic insulation of electron cooler restricted the operation of electron cooler at HIRFL-CSR main ring. To cool and accumulate ion beam well, the pollution was cleared and a new oxidecoated cathode was assembled. The processes of cathode replacement, vacuum chamber baking-out, and thermal decomposition of coating binders and alkaline earth metal carbonates, and cathode activation are presented. The electron gun perveance of 10.6 μＡ/V1.5 was attained under the heating power of 60 W. The typical surface temperature of oxide-coated cathode that is calculated through grey-body radiation is 1 108 K which shows a comparable result to the experimental measurement 1 078 K. The perveance growth of electron gun during the electron cooler operation is also explaine
2011,
23.
Abstract:
A numerical simulation has been conducted using the particle-in-cell with Monte Carlo collision (PIC-MCC) method to model charge-exchange (CEX) xenon ions in the plume of ion thruster. A parallel particle simulation code has been developed by using the Compute Unified Device Architecture (CUDA) for graphic processor unit (GPU). The random number is generated by the parallel Mersenne Twister pseudorandom number generator algorithm. The full approximation storage-algebraic multigrid method (FAS-AMG) is used to update the electric field. In an axis-symmetric(r-z) coordinate, the average ion current flux is 4.5×10-5 A/m2 at z=0 m, and GPU’s result agrees well with CPU’s. Compared with a single CPU Intel Core 2 E6300, 16-processor GPU NVIDIA GeForce 9400 GT represents 4
A numerical simulation has been conducted using the particle-in-cell with Monte Carlo collision (PIC-MCC) method to model charge-exchange (CEX) xenon ions in the plume of ion thruster. A parallel particle simulation code has been developed by using the Compute Unified Device Architecture (CUDA) for graphic processor unit (GPU). The random number is generated by the parallel Mersenne Twister pseudorandom number generator algorithm. The full approximation storage-algebraic multigrid method (FAS-AMG) is used to update the electric field. In an axis-symmetric(r-z) coordinate, the average ion current flux is 4.5×10-5 A/m2 at z=0 m, and GPU’s result agrees well with CPU’s. Compared with a single CPU Intel Core 2 E6300, 16-processor GPU NVIDIA GeForce 9400 GT represents 4
2011,
23.
Abstract:
A simple and effective short linear cavity erbium-doped fiber laser was presented. The laser consisted of an optical circulator (OC), a segment of self-made high concentration erbium-doped fiber co-doped with Bi3+Ga3+Al3+(BiGaAl-EDF), a uniform fiber Bragg grating (UFBG), and a wavelength division multiplexing(WDM). By using the OC as an all-reflection mirror and the UFBG written directly in the G652 fiber as a partial-reflection mirror and a wavelength selector, a stable wavelength oscillation with a center wavelength of 1 544.31 nm and a side mode suppression ratio (SMSR) of about 57 dB is achieved at room temperature. The impact of the length of BiGaAl-EDF on the laser’s output characteristic was analyzed. With a 12 cm long BiGaAl-EDF as the gain medium
A simple and effective short linear cavity erbium-doped fiber laser was presented. The laser consisted of an optical circulator (OC), a segment of self-made high concentration erbium-doped fiber co-doped with Bi3+Ga3+Al3+(BiGaAl-EDF), a uniform fiber Bragg grating (UFBG), and a wavelength division multiplexing(WDM). By using the OC as an all-reflection mirror and the UFBG written directly in the G652 fiber as a partial-reflection mirror and a wavelength selector, a stable wavelength oscillation with a center wavelength of 1 544.31 nm and a side mode suppression ratio (SMSR) of about 57 dB is achieved at room temperature. The impact of the length of BiGaAl-EDF on the laser’s output characteristic was analyzed. With a 12 cm long BiGaAl-EDF as the gain medium
2011,
23.
Abstract:
The resonance mechanism and characteristics of surface plasma in the anisotropic metal film with a periodic array of sub-wavelength holes are investigated under external magnetic field adopting the anisotropic model and full-vector 3-D finite-difference time-domain (FDTD) method. There are two resonance modes: localized waveguide resonance from the period rectangular hole array and photonic crystal resonance from the periodic structures. It is found that both the resonance modes shift towards shortwave region with the increasing of the applied magnetic field; the peak of the photonic crystal resonance shifts towards long-wave region, while the peak of the waveguide resonance transfers to short-wave region. In addition, the enhanced transmission effect might be controlled by adjusting the m
The resonance mechanism and characteristics of surface plasma in the anisotropic metal film with a periodic array of sub-wavelength holes are investigated under external magnetic field adopting the anisotropic model and full-vector 3-D finite-difference time-domain (FDTD) method. There are two resonance modes: localized waveguide resonance from the period rectangular hole array and photonic crystal resonance from the periodic structures. It is found that both the resonance modes shift towards shortwave region with the increasing of the applied magnetic field; the peak of the photonic crystal resonance shifts towards long-wave region, while the peak of the waveguide resonance transfers to short-wave region. In addition, the enhanced transmission effect might be controlled by adjusting the m
2011,
23.
Abstract:
A high sensitive radiochromic film has been developed by using poly (vinyl butyral) as the base and using acetylene-type compounds as the organic dye material, and was tested with the J-2.5 proton electrostatic accelerator, with proton energy of 2.0 MeV, irradiation fluence of 1.0×1010 to 1.0×1012 cm2. The tests of radiation effects show that, the color of the radiochromic film changes from pink to blue, and the optical density decreases along with the increase of the focus spot distance. Absorbance spectrum analysis shows that, the peak in the visual region locates around 660 nm. There is a linear relationship between absorbency and proton-flux for irradiation at the same proton energy. The response of the film can be measured immediately after irradiati
A high sensitive radiochromic film has been developed by using poly (vinyl butyral) as the base and using acetylene-type compounds as the organic dye material, and was tested with the J-2.5 proton electrostatic accelerator, with proton energy of 2.0 MeV, irradiation fluence of 1.0×1010 to 1.0×1012 cm2. The tests of radiation effects show that, the color of the radiochromic film changes from pink to blue, and the optical density decreases along with the increase of the focus spot distance. Absorbance spectrum analysis shows that, the peak in the visual region locates around 660 nm. There is a linear relationship between absorbency and proton-flux for irradiation at the same proton energy. The response of the film can be measured immediately after irradiati
2011,
23.
Abstract:
Amplification without inversion (AWI) is discussed in a lambda three level system where a coupling field interacts with two separate optical transitions between two ground state hyperfine levels and an excited state level. Both electromagnetically induced transparency (EIT) and spontaneous radiation induced coherent dip are obtained, and AWI is observed in the EIT window by tuning the excitation frequency of the coupling field to satisfy certain conditions. The results show that, there is energy transfer between EIT and spontaneous radiation induced coherent dip, and when AWI is observed, there is no population inversion between the ground state hyperfine levels and the excited state level, but population inversion between the two ground state hyperfine levels.
Amplification without inversion (AWI) is discussed in a lambda three level system where a coupling field interacts with two separate optical transitions between two ground state hyperfine levels and an excited state level. Both electromagnetically induced transparency (EIT) and spontaneous radiation induced coherent dip are obtained, and AWI is observed in the EIT window by tuning the excitation frequency of the coupling field to satisfy certain conditions. The results show that, there is energy transfer between EIT and spontaneous radiation induced coherent dip, and when AWI is observed, there is no population inversion between the ground state hyperfine levels and the excited state level, but population inversion between the two ground state hyperfine levels.
2011,
23.
Abstract:
This paper studies the parallel numerical simulation of interaction between intense laser and hydrogen clusters. Based on 1D hydrogen atom cluster model and particle-particle algorithm and PIC method, a parallel system and strategy was designed with hybrid MPI and OpenMP programming and the speedup was ideal. The relaxation time constant was also introduced to effectively handle the process of particle collision. The results of the simulation were in fairly good agreement with experimental results, which shows that this parallel computing system and model is stable and feasible.
This paper studies the parallel numerical simulation of interaction between intense laser and hydrogen clusters. Based on 1D hydrogen atom cluster model and particle-particle algorithm and PIC method, a parallel system and strategy was designed with hybrid MPI and OpenMP programming and the speedup was ideal. The relaxation time constant was also introduced to effectively handle the process of particle collision. The results of the simulation were in fairly good agreement with experimental results, which shows that this parallel computing system and model is stable and feasible.
2011,
23.
Abstract:
A pulsed X-ray radiographic source based on inductive voltage adder (IVA) and rod-pinch diode (RPD) is developed at the Northwest Institute of Nuclear Technology. The X-ray spot size of RPD is a critical parameter to evaluate the spatial resolution performance for radiography. Using thick pinhole imaging technique, two-dimension images of the RPD X-ray spots have been measured. A pinhole with 0.2-mm-diameter was designed and an image acquirement system based on a lutetium-oxyorthosilicate-crystal scintillator, a lens and a CCD camera was established. The magnifications of the pinhole and the lens are about 5 and 0.34, respectively. The spatial resolution of the pinhole imaging layout is 2.0 lp·mm-1 at the modulation transfer function (MTF) of 0.5 for 0.5 MeV X-ray. Through the restoration
A pulsed X-ray radiographic source based on inductive voltage adder (IVA) and rod-pinch diode (RPD) is developed at the Northwest Institute of Nuclear Technology. The X-ray spot size of RPD is a critical parameter to evaluate the spatial resolution performance for radiography. Using thick pinhole imaging technique, two-dimension images of the RPD X-ray spots have been measured. A pinhole with 0.2-mm-diameter was designed and an image acquirement system based on a lutetium-oxyorthosilicate-crystal scintillator, a lens and a CCD camera was established. The magnifications of the pinhole and the lens are about 5 and 0.34, respectively. The spatial resolution of the pinhole imaging layout is 2.0 lp·mm-1 at the modulation transfer function (MTF) of 0.5 for 0.5 MeV X-ray. Through the restoration
2011,
23.
Abstract:
The quantification of margins and uncertainties (QMU) method is analyzed, which is used to assess the radiation hardness of the electronic system. In order to use the QMU method, a procedure based on Monte Carlo method and SPICE circuit simulator is proposed to evaluate the margin and uncertainty of the system’s output. The radiation hardness of a power supply system is assessed, and the assessed results are in good agreement with those obtained experimentally．
The quantification of margins and uncertainties (QMU) method is analyzed, which is used to assess the radiation hardness of the electronic system. In order to use the QMU method, a procedure based on Monte Carlo method and SPICE circuit simulator is proposed to evaluate the margin and uncertainty of the system’s output. The radiation hardness of a power supply system is assessed, and the assessed results are in good agreement with those obtained experimentally．
2011,
23.
Abstract:
Optimization methods of edge linking and linear fitting are researched to improve the efficiency and accuracy of the industrial computed tomography (CT) image processing system. For edge linking, the linking mode is decided by the size of the gap between edges. The smaller gap is linked with a line and the bigger gap is linked with an optimal path calculated by fuzzy theory. For linear fitting, feature points of the contour are obtained, and then an improved method of set intersection operation for line recognition is adopted to fit the feature points. The application proves that the optimization methods are effective and feasible.
Optimization methods of edge linking and linear fitting are researched to improve the efficiency and accuracy of the industrial computed tomography (CT) image processing system. For edge linking, the linking mode is decided by the size of the gap between edges. The smaller gap is linked with a line and the bigger gap is linked with an optimal path calculated by fuzzy theory. For linear fitting, feature points of the contour are obtained, and then an improved method of set intersection operation for line recognition is adopted to fit the feature points. The application proves that the optimization methods are effective and feasible.
2011,
23.
Abstract:
The effects of gamma irradiation on collector current and Early voltage of silicon-germanium (SiGe) heterojunction bipolar transistor are investigated. After 104 Gy(Si) total dose irradiation, increases of the collector current and Early voltage are observed. Besides, both the threshold voltages and the breakdown voltages of the emitter-base and the collector-base junctions decrease. All the changes are thought to be mainly due to the reduction of effective carrier concentrations in the emitter and collector regions caused by radiation-induced defects.
The effects of gamma irradiation on collector current and Early voltage of silicon-germanium (SiGe) heterojunction bipolar transistor are investigated. After 104 Gy(Si) total dose irradiation, increases of the collector current and Early voltage are observed. Besides, both the threshold voltages and the breakdown voltages of the emitter-base and the collector-base junctions decrease. All the changes are thought to be mainly due to the reduction of effective carrier concentrations in the emitter and collector regions caused by radiation-induced defects.
2011,
23.
Abstract:
Simulations and experiments have been done to find out the suitable circuit parameters, with which the pre-pulse flowing from the Blumlein pulse forming line during the charge cycle can reset the magnetic cores in the double-pulse induction cavity adequately. By the circuit simulations, a new modulus, named “the maximum reset pulse-width”, has been proposed to mark the reset ability of pre-pulse. The veracity of the modulus has been proved by the experiments. By adjusting the load of the Blumlein line according to the requirements of the modulus, the auto-reset problem of cores of the linear induction accelerator cell using “cable delay” double pulse power system can be solved with the least effect on the primary pulses.
Simulations and experiments have been done to find out the suitable circuit parameters, with which the pre-pulse flowing from the Blumlein pulse forming line during the charge cycle can reset the magnetic cores in the double-pulse induction cavity adequately. By the circuit simulations, a new modulus, named “the maximum reset pulse-width”, has been proposed to mark the reset ability of pre-pulse. The veracity of the modulus has been proved by the experiments. By adjusting the load of the Blumlein line according to the requirements of the modulus, the auto-reset problem of cores of the linear induction accelerator cell using “cable delay” double pulse power system can be solved with the least effect on the primary pulses.
2011,
23.
Abstract:
This paper described the structure parameters and working principle of the spiral generator, and analyzed the influence output characteristics of spiral generator’s three loss factors: switch resistance loss factor, spiral generator resistance loss factor and transmission line between adjacent coaxial capacitor leakage loss factors. Spiral generator’s loss factors were determined by structural parameters, through experiment and research, the paper gave the structural parameters of spiral generator as output effect relation, and the transmission loss factor and the adjacent resistance electric leakage coaxial transmission loss factor and the structural parameters of the empirical formula. It provides experimental data for constructing circuit model of spiral generator and technical refere
This paper described the structure parameters and working principle of the spiral generator, and analyzed the influence output characteristics of spiral generator’s three loss factors: switch resistance loss factor, spiral generator resistance loss factor and transmission line between adjacent coaxial capacitor leakage loss factors. Spiral generator’s loss factors were determined by structural parameters, through experiment and research, the paper gave the structural parameters of spiral generator as output effect relation, and the transmission loss factor and the adjacent resistance electric leakage coaxial transmission loss factor and the structural parameters of the empirical formula. It provides experimental data for constructing circuit model of spiral generator and technical refere
2011,
23.
Abstract:
A new method for calculating the neutron sensitivity of the slot-collimated fission detector system based on analytical formula is presented. The analytical formula of the neutron sensitivity was achieved through educing the numbers of fragments and the fragments acquisition probability of PIN detectors by the methods of integral and Taylor expansion. The neutron sensitivity was also measured on a D-T accelerator. The theoretical results derived from the formulas are consistent with the experimental ones with the deviation is less than 10%．
A new method for calculating the neutron sensitivity of the slot-collimated fission detector system based on analytical formula is presented. The analytical formula of the neutron sensitivity was achieved through educing the numbers of fragments and the fragments acquisition probability of PIN detectors by the methods of integral and Taylor expansion. The neutron sensitivity was also measured on a D-T accelerator. The theoretical results derived from the formulas are consistent with the experimental ones with the deviation is less than 10%．
2011,
23.
Abstract:
According to pulse driver and its load parameters, the designed specifications of 1.2 MV/70 ns are calculated for induction cell of inductive voltage adder (IVA). Considering the current efficiency and vacuum line insulation, the mechanical dimensions of cores are chosen. The pre-annealed amorphous cores with remanence ratio of 0.5 measured by experiments is produced, and the number of magnetic toroids is determined as no less than 6. The measured peak permeability of cores with flux density changing rate up to 30 T/μs is consistent with that derived by saturation wave model. The equivalent magnetization inductance and eddy loss resistance are respectively estimated as 7.3 μH and 139 Ω. By the empirical formula of critical breakdown field and the numerical analysis of electric field, th
According to pulse driver and its load parameters, the designed specifications of 1.2 MV/70 ns are calculated for induction cell of inductive voltage adder (IVA). Considering the current efficiency and vacuum line insulation, the mechanical dimensions of cores are chosen. The pre-annealed amorphous cores with remanence ratio of 0.5 measured by experiments is produced, and the number of magnetic toroids is determined as no less than 6. The measured peak permeability of cores with flux density changing rate up to 30 T/μs is consistent with that derived by saturation wave model. The equivalent magnetization inductance and eddy loss resistance are respectively estimated as 7.3 μH and 139 Ω. By the empirical formula of critical breakdown field and the numerical analysis of electric field, th
