Email alert
RSS2008 Vol. 20, No. 08
Recommend Articles
Display Method:
2008,
20.
Abstract:
A designed pulsed power modulator are experimentally studied in single pulse mode and in repetitive mode, respectively. The measured maximum secondary charging voltages of the Tesla transformer are 370 kV and 300 kV in single pulse mode and repetitive mode (50 Hz), respectively. The charging operation of Tesla transformer can be steadily carried out and the modulator’s highest output voltage through a 100 Ω resistive load in single pulse mode is 330 kV with 7 ns duration and 2 ns rise time. The cooling system and gas blowing system are unnecessary and unadopted experimentally in repetitive mode when the number of pulses in a batch is less than or equal to 300. As a result, the volume and weight of the modulator system is reduced. In the range of 300 pulses in a batch, with the increase o
A designed pulsed power modulator are experimentally studied in single pulse mode and in repetitive mode, respectively. The measured maximum secondary charging voltages of the Tesla transformer are 370 kV and 300 kV in single pulse mode and repetitive mode (50 Hz), respectively. The charging operation of Tesla transformer can be steadily carried out and the modulator’s highest output voltage through a 100 Ω resistive load in single pulse mode is 330 kV with 7 ns duration and 2 ns rise time. The cooling system and gas blowing system are unnecessary and unadopted experimentally in repetitive mode when the number of pulses in a batch is less than or equal to 300. As a result, the volume and weight of the modulator system is reduced. In the range of 300 pulses in a batch, with the increase o
2008,
20.
Abstract:
A magnetic pulse compression system which does not contain external remagnetization circuits commonly used in magnetic compressors is presented. Principle of operation for the compressor is described. Simulation of pulse compressor working on a 500 Ω resistive load illustrates that in order to realize the desired pulse, 6 ms and 500 ns magnetization period would be required for cores of saturable pulse transformer and magnetic switch, respectively. The one-stage compression system delivers a -18.5 kV, 70 ns pulse width across a 200 Ω load with a fall time of 40 ns and a repetition rate up to 500 Hz. To improve the matching, the inductor in parallel with load is replaced with a fast-recovering HV diode. The experiment shows that the pulse voltage reverse amplitude and damped oscillation d
A magnetic pulse compression system which does not contain external remagnetization circuits commonly used in magnetic compressors is presented. Principle of operation for the compressor is described. Simulation of pulse compressor working on a 500 Ω resistive load illustrates that in order to realize the desired pulse, 6 ms and 500 ns magnetization period would be required for cores of saturable pulse transformer and magnetic switch, respectively. The one-stage compression system delivers a -18.5 kV, 70 ns pulse width across a 200 Ω load with a fall time of 40 ns and a repetition rate up to 500 Hz. To improve the matching, the inductor in parallel with load is replaced with a fast-recovering HV diode. The experiment shows that the pulse voltage reverse amplitude and damped oscillation d
2008,
20.
Abstract:
The beam kicker system is a key part for beam extraction and injection in ring-like accelerator, which works under high voltage and huge current. This paper introduces the kicker control system based on ARM + DSP + FPGA for CSR project in Lanzhou, which has nanosecond timing precision. ARM mainly completes the control signals with the network communication, and the time control precision for the beam kicker system is performed mainly by FPGA and DSP. The sequence control signals through the optic fiber transmission, synchronous to kicker power supply the voltage to assign uses the signal isolators and ferrites to suppress the disturbance pulses. Scene test has proved that this system can meet beam kicker control’s request and work safely and stably. The control system has extracted and in
The beam kicker system is a key part for beam extraction and injection in ring-like accelerator, which works under high voltage and huge current. This paper introduces the kicker control system based on ARM + DSP + FPGA for CSR project in Lanzhou, which has nanosecond timing precision. ARM mainly completes the control signals with the network communication, and the time control precision for the beam kicker system is performed mainly by FPGA and DSP. The sequence control signals through the optic fiber transmission, synchronous to kicker power supply the voltage to assign uses the signal isolators and ferrites to suppress the disturbance pulses. Scene test has proved that this system can meet beam kicker control’s request and work safely and stably. The control system has extracted and in
2008,
20.
Abstract:
The formation and evolution of oxygen vacancies in ZnO white paint during exposure to less than 200 keV protons were investigated in terms of photoluminescence spectroscopy and X-ray photoelectron spectroscopy (XPS). The decreases of lattice oxygen and Zn vacancies which are respectively shown by XPS and photoluminescence spectroscopy, indicate that oxygen vacancies of ZnO white paint increases under the proton irradiation. The double ionized oxygen vacancies can trap electrons in the conductive bands to become the single ionized oxygen vacancies, leading to that the singly ionized oxygen vacancies gradually become the major defects induced by the proton irradiation. Proton irradiation leads to increase the amount of oxygen vacancy, and oxygen vacancy can trap electrons to form color cente
The formation and evolution of oxygen vacancies in ZnO white paint during exposure to less than 200 keV protons were investigated in terms of photoluminescence spectroscopy and X-ray photoelectron spectroscopy (XPS). The decreases of lattice oxygen and Zn vacancies which are respectively shown by XPS and photoluminescence spectroscopy, indicate that oxygen vacancies of ZnO white paint increases under the proton irradiation. The double ionized oxygen vacancies can trap electrons in the conductive bands to become the single ionized oxygen vacancies, leading to that the singly ionized oxygen vacancies gradually become the major defects induced by the proton irradiation. Proton irradiation leads to increase the amount of oxygen vacancy, and oxygen vacancy can trap electrons to form color cente
2008,
20.
Abstract:
Radiography is one application of the hard X-ray derived from ultra-short ultra-intense(US-UI) laser-matter interactions. Experiments about hard X-ray production from US-UI laser interaction with high-Z metal targets, on SILEX-Ⅰ laser facility at National Key Laboratory of Laser Fusion have obtained radiographs. The radiograph receivers were sandwich detectors with scintillation layer and film and with scintillation and CCD. Radiograph’s quality and resolution vary obviously because of different scintillator thickness and magnification ratio. This radiography technique not only can be the basic method for investigating the advanced X-ray imaging source, but also can be the detection system for studying laser-solid target interactions.
Radiography is one application of the hard X-ray derived from ultra-short ultra-intense(US-UI) laser-matter interactions. Experiments about hard X-ray production from US-UI laser interaction with high-Z metal targets, on SILEX-Ⅰ laser facility at National Key Laboratory of Laser Fusion have obtained radiographs. The radiograph receivers were sandwich detectors with scintillation layer and film and with scintillation and CCD. Radiograph’s quality and resolution vary obviously because of different scintillator thickness and magnification ratio. This radiography technique not only can be the basic method for investigating the advanced X-ray imaging source, but also can be the detection system for studying laser-solid target interactions.
2008,
20.
Abstract:
Based on Stillinger-Weber(SW) potential and “x-section” model, femtosecond laser ablation of monocrystalline silicon was simulated using molecular dynamics method. Snapshots of ablation process were obtained which showed that the emergence and development of internal defects caused a slice of silicon to be removed from the bulk. Traces of atoms in different sections of ablated material were compared which described the characteristics of atoms under states of liquid, solid and gas. Laser-induced stress wave whose velocity was 8.18 km/s was also observed.
Based on Stillinger-Weber(SW) potential and “x-section” model, femtosecond laser ablation of monocrystalline silicon was simulated using molecular dynamics method. Snapshots of ablation process were obtained which showed that the emergence and development of internal defects caused a slice of silicon to be removed from the bulk. Traces of atoms in different sections of ablated material were compared which described the characteristics of atoms under states of liquid, solid and gas. Laser-induced stress wave whose velocity was 8.18 km/s was also observed.
2008,
20.
Abstract:
Scintillator arrays are used in radiation image detection generally. A relative correction method was proposed based on the severe photoresponse nonuniformity of scintillator arrays. The attenuation distribution of the detected object to γ-ray could be detected via background image, reference image and radiation image on the condition that the light source parameter，CCD camera parameter and optical system parameter were all unknown. The justification experiment was performed and the outcome showed that the influence of both the photoresponse non-uniformity and the inherent distribution of radiation source could be eliminated．
Scintillator arrays are used in radiation image detection generally. A relative correction method was proposed based on the severe photoresponse nonuniformity of scintillator arrays. The attenuation distribution of the detected object to γ-ray could be detected via background image, reference image and radiation image on the condition that the light source parameter，CCD camera parameter and optical system parameter were all unknown. The justification experiment was performed and the outcome showed that the influence of both the photoresponse non-uniformity and the inherent distribution of radiation source could be eliminated．
2008,
20.
Abstract:
Cut-off energy of proton accelerated in experiment on SILEX-I is estimated, according to the front mechanism and rear side mechanism of interaction between ultrashort ultra-intense laser and solid target. The estimation according to the rear side mechanism agree well with experimental data. Meanwhile, the maximum proton energy accelerated in interaction of short laser pulse with solid targets on SILEX-I is also calculated: 11 MeV for the rear side mechanism and 2.0 MeV for the front side mechanism. Besides, the influence of prepulse to accelerating field is estimated by Multi2005 code and it can be neglected when signal-to-noise ratio is better than 108∶1.
Cut-off energy of proton accelerated in experiment on SILEX-I is estimated, according to the front mechanism and rear side mechanism of interaction between ultrashort ultra-intense laser and solid target. The estimation according to the rear side mechanism agree well with experimental data. Meanwhile, the maximum proton energy accelerated in interaction of short laser pulse with solid targets on SILEX-I is also calculated: 11 MeV for the rear side mechanism and 2.0 MeV for the front side mechanism. Besides, the influence of prepulse to accelerating field is estimated by Multi2005 code and it can be neglected when signal-to-noise ratio is better than 108∶1.
2008,
20.
Abstract:
In order to increase the pumping efficiency of pyrotechnically pumped laser, a method was presented to increase the burning rate and improve the irradiance ability of pyrotechnic agent. The new compositions were designed to replace Al-Mg alloy powders by pulverized Mg powders partially. When mass ratio between Mg and Al-Mg was 1∶1, 2.1 times burning rate and 2.4 times radiant intensity were achieved for poles, 2.4 times burning rate and 2.55 times radiant intensity were achieved for pellets, and the spectrum efficiency of poles and pellets were improved ratherish. A model was built to analyze burning rate after detonation. Calculational results according to the model were that, 2.3 times burning rate than that of Al-Mg powder as the reducing agent was achieved when mass fraction of Mg was
In order to increase the pumping efficiency of pyrotechnically pumped laser, a method was presented to increase the burning rate and improve the irradiance ability of pyrotechnic agent. The new compositions were designed to replace Al-Mg alloy powders by pulverized Mg powders partially. When mass ratio between Mg and Al-Mg was 1∶1, 2.1 times burning rate and 2.4 times radiant intensity were achieved for poles, 2.4 times burning rate and 2.55 times radiant intensity were achieved for pellets, and the spectrum efficiency of poles and pellets were improved ratherish. A model was built to analyze burning rate after detonation. Calculational results according to the model were that, 2.3 times burning rate than that of Al-Mg powder as the reducing agent was achieved when mass fraction of Mg was
2008,
20.
Abstract:
To achieve the simulation for IR detection of spatial targets, analysis and analogy calculation of the temperature field of the target in spa is needed. One of the most important boundary condition is the surface material natural parameters of targets. Bidirectional reflectance distribution function(BRDF) method to measure target surface reflectance is studied and the BRDF measuring spectrum and laser reflectance feature platform is built. Thermal parameters of some typical thermal control coating on spatial targets are measured. The measuring tests indicate that the reflectance of white paint coating SR107 is 0.785 while the input angle is 0°. The tests also show that the reflectances of OSR，F46 and polyimidethinfilm are greater than 90%．
To achieve the simulation for IR detection of spatial targets, analysis and analogy calculation of the temperature field of the target in spa is needed. One of the most important boundary condition is the surface material natural parameters of targets. Bidirectional reflectance distribution function(BRDF) method to measure target surface reflectance is studied and the BRDF measuring spectrum and laser reflectance feature platform is built. Thermal parameters of some typical thermal control coating on spatial targets are measured. The measuring tests indicate that the reflectance of white paint coating SR107 is 0.785 while the input angle is 0°. The tests also show that the reflectances of OSR，F46 and polyimidethinfilm are greater than 90%．
2008,
20.
Abstract:
Based on Boltzmann distribution law which is the derived distribution characteristic of electrons by potential energy in a conservative field from Boltzmann integrally differential equation in equilibrium state, the distribution functions of volume charge density and the velocity of electron pulse system in the externally supported unequal-potential space are achieved from the perspective of statistical physics by solving Poisson’s equation. And the qualitative analysis of the dynamic variation characteristics of the two parametric distributions indicates that a higher external potential will restrain the unwelcome space charge effects which cause electron pulse broadening and energy spread. The physical mechanism of the optimization effect of higher electric field in the vicinity of the
Based on Boltzmann distribution law which is the derived distribution characteristic of electrons by potential energy in a conservative field from Boltzmann integrally differential equation in equilibrium state, the distribution functions of volume charge density and the velocity of electron pulse system in the externally supported unequal-potential space are achieved from the perspective of statistical physics by solving Poisson’s equation. And the qualitative analysis of the dynamic variation characteristics of the two parametric distributions indicates that a higher external potential will restrain the unwelcome space charge effects which cause electron pulse broadening and energy spread. The physical mechanism of the optimization effect of higher electric field in the vicinity of the
2008,
20.
Abstract:
The optical diagnostics of annulus-flat water switch in “Qiangguang-Ⅰ” facility was carried out utilizing optical framing camera and fiber sensor. The images of the discharging channels and the irradiance intensity signal during charging stage were acquired. The experiment results showed that the average breakdown electric field of annulus-flat water switch was about 190 kV/cm, several discharging channels were observed at the same time, the streamers appeared like bush and their velocity was about tens of cm/μs.
The optical diagnostics of annulus-flat water switch in “Qiangguang-Ⅰ” facility was carried out utilizing optical framing camera and fiber sensor. The images of the discharging channels and the irradiance intensity signal during charging stage were acquired. The experiment results showed that the average breakdown electric field of annulus-flat water switch was about 190 kV/cm, several discharging channels were observed at the same time, the streamers appeared like bush and their velocity was about tens of cm/μs.
2008,
20.
Abstract:
The primary power supply of repetitive pulsed intense current accelerator charged by capacitance of energy store is studied. The principle of primary power supply circuit and its time diagram of switches are presented. The circuit is analyzed and some expressions are got, especially, the usable voltage scope of capacitance of energy store, and the correlation between the parameters of circuit and time delay, which is between the turn-on of the charging circuit of capacitance of energy store and the circuit of recuperation. The time delay of 256×256 lookup table is made with the instruction of theory and the simulation of the actual parameters of circuits. The table is used by the control program to control the repetitive operating of the actual pulsed intense current accelerator. Finally,
The primary power supply of repetitive pulsed intense current accelerator charged by capacitance of energy store is studied. The principle of primary power supply circuit and its time diagram of switches are presented. The circuit is analyzed and some expressions are got, especially, the usable voltage scope of capacitance of energy store, and the correlation between the parameters of circuit and time delay, which is between the turn-on of the charging circuit of capacitance of energy store and the circuit of recuperation. The time delay of 256×256 lookup table is made with the instruction of theory and the simulation of the actual parameters of circuits. The table is used by the control program to control the repetitive operating of the actual pulsed intense current accelerator. Finally,
2008,
20.
Abstract:
A model based on the open-circuit voltage formula of the PV-type detector, which is derived from the driftdiffusion model under the steady-condition approximation, is used to calculate the responses of PV-type HgCdTe detector under laser irradiation, in which the temperature change of detector is taken in to account. The calculation results agree well with the experiment results under weak laser irradiation; when the laser intensity is higher, the calculation results show notable deviation from the experiment results, in which the output of detector decrease rapidly when the laser begins to irradiate and increase rapidly when the laser stops to irradiate. The results suggest that when the laser intensity is higher, the hot carrier effects can’t be negligible and the model used here is n
A model based on the open-circuit voltage formula of the PV-type detector, which is derived from the driftdiffusion model under the steady-condition approximation, is used to calculate the responses of PV-type HgCdTe detector under laser irradiation, in which the temperature change of detector is taken in to account. The calculation results agree well with the experiment results under weak laser irradiation; when the laser intensity is higher, the calculation results show notable deviation from the experiment results, in which the output of detector decrease rapidly when the laser begins to irradiate and increase rapidly when the laser stops to irradiate. The results suggest that when the laser intensity is higher, the hot carrier effects can’t be negligible and the model used here is n
2008,
20.
Abstract:
The efficiency of Nd:YAG laser raster scanning conditioning of optics was investigated. The existence of intensity and pointing fluctuations of laser beam would lead to descending of laser conditioning efficiency. It was also found that the fluctuation influences were modulated by beam overlap space and raster scan patterns. The effect of laser pulse fluctuations on conditioning efficiency is much less in triangle lattice pattern than that in square lattice pattern. Conditioning procedure could be optimized according to this work.
The efficiency of Nd:YAG laser raster scanning conditioning of optics was investigated. The existence of intensity and pointing fluctuations of laser beam would lead to descending of laser conditioning efficiency. It was also found that the fluctuation influences were modulated by beam overlap space and raster scan patterns. The effect of laser pulse fluctuations on conditioning efficiency is much less in triangle lattice pattern than that in square lattice pattern. Conditioning procedure could be optimized according to this work.
2008,
20.
Abstract:
A mathematic model of the laser diode array(LDA) side-pump composite crystal Nd:YAG/YAG disk laser is set up：LDA fast axis is upright to disk face and micro lens collimate the fast axis. Far-field divergence angle of the slow axis is calculated and simulated，the result shows：far-field divergence angle of the slow axis has approximately Gaussian distribution. Study shows that more diodes lead to better pumping intensity distribution; the least absorption coefficient of laser medium, the best pumping intensity distribution; the smaller distance between diode and laser medium, the worse pumping intensity distribution. The phenomenon can be observed from the experiment with different absorption coefficient of Nd:YAG/YAG ,the pumping intensity distribution becomes better when there is 0.6%
A mathematic model of the laser diode array(LDA) side-pump composite crystal Nd:YAG/YAG disk laser is set up：LDA fast axis is upright to disk face and micro lens collimate the fast axis. Far-field divergence angle of the slow axis is calculated and simulated，the result shows：far-field divergence angle of the slow axis has approximately Gaussian distribution. Study shows that more diodes lead to better pumping intensity distribution; the least absorption coefficient of laser medium, the best pumping intensity distribution; the smaller distance between diode and laser medium, the worse pumping intensity distribution. The phenomenon can be observed from the experiment with different absorption coefficient of Nd:YAG/YAG ,the pumping intensity distribution becomes better when there is 0.6%
2008,
20.
Abstract:
A detecting module for measuring power density of mid-infrared laser is developed using room temperature HgCdTe photoconductor detector. The module is consisted of optic filter attenuator, HgCdTe detector, amplifier, analog to digital converter, and signal processor. The temperature characters of the HgCdTe detector are analysed, and the responsivity self-adjusting model of detector with temperature is established. The module is suitable for power density measuring of mid-infrared laser when the working temperature is －30~40 ℃, with measurement uncertainty less than 20%．
A detecting module for measuring power density of mid-infrared laser is developed using room temperature HgCdTe photoconductor detector. The module is consisted of optic filter attenuator, HgCdTe detector, amplifier, analog to digital converter, and signal processor. The temperature characters of the HgCdTe detector are analysed, and the responsivity self-adjusting model of detector with temperature is established. The module is suitable for power density measuring of mid-infrared laser when the working temperature is －30~40 ℃, with measurement uncertainty less than 20%．
2008,
20.
Abstract:
If the angle between the orientation of the interference fringes and the detector’s coordinate axis varies, the four quadrant units may detect different intensity distributions because of their quadrant characteristics, and the intensity of each quadrant unit may have different phase according to the principle of vector superposition of the cosinusoidal interference fringes. Two detected signals from the four quadrant units, whose phase difference is 90°, could always be found by rotating the detector. When the period of interference fringes changes, the corresponding orthogonal signals by rotating the detector are also detected. Theoretical analysis and numerical simulation validate this method’s feasibility and practicity. Compared with the traditional method, this method has advantag
If the angle between the orientation of the interference fringes and the detector’s coordinate axis varies, the four quadrant units may detect different intensity distributions because of their quadrant characteristics, and the intensity of each quadrant unit may have different phase according to the principle of vector superposition of the cosinusoidal interference fringes. Two detected signals from the four quadrant units, whose phase difference is 90°, could always be found by rotating the detector. When the period of interference fringes changes, the corresponding orthogonal signals by rotating the detector are also detected. Theoretical analysis and numerical simulation validate this method’s feasibility and practicity. Compared with the traditional method, this method has advantag
2008,
20.
Abstract:
For improving the beam quality, the application of cube corners reflector was studied. The cube corners reflector was used as the cavity mirror, with use of the quasi-phase conjugation characteristics of the cube corners, the wave-front aberration of resonator cavity was restrained. The element side length of the cube corner array is optimized for the actual resonator configuration. The experimental results show that the cube corner array was effective in improving the far-field beam quality. When the element side length of the cube corner array is 4 mm, the far-field of laser output obtains the seven times diffraction limits.
For improving the beam quality, the application of cube corners reflector was studied. The cube corners reflector was used as the cavity mirror, with use of the quasi-phase conjugation characteristics of the cube corners, the wave-front aberration of resonator cavity was restrained. The element side length of the cube corner array is optimized for the actual resonator configuration. The experimental results show that the cube corner array was effective in improving the far-field beam quality. When the element side length of the cube corner array is 4 mm, the far-field of laser output obtains the seven times diffraction limits.
2008,
20.
Abstract:
For the gas concentration measurement system based on the tunable diodelaser absorption technique spectroscopy (TDLAS), a state-space strategy has been proposed. The proposed strategy formulates the gas concentration distribution through the state equations, and measures the absorption spectroscopy distribution through observation equations. Further, it coherently treats the uncertainties of the statistical model of the system and the noisy nature of the measurement data. The performance of the proposed framework is evaluated with favorable results．
For the gas concentration measurement system based on the tunable diodelaser absorption technique spectroscopy (TDLAS), a state-space strategy has been proposed. The proposed strategy formulates the gas concentration distribution through the state equations, and measures the absorption spectroscopy distribution through observation equations. Further, it coherently treats the uncertainties of the statistical model of the system and the noisy nature of the measurement data. The performance of the proposed framework is evaluated with favorable results．
2008,
20.
Abstract:
In order to make the grazing incidence XUV flat-field spectrograph’s size shorter for the convenience of use, a ray-tracing code is set to research the influence of the concave grating’s parameter on the spectrum imaging when the incident distance is 155 mm and the focusing surface is still flat. It is found that for the concave grating with curvature radius of 5 649 mm and 1/1 200 nm nominal spacing of the grooves, the angle of incidence is 87.5°, when the incident distance is 155 mm, the focus parameter is -21/R and the coma-type aberration parameter is 4.655102/R2, a better imaging effect within the wave band of 12 ~ 40 nm is realized.
In order to make the grazing incidence XUV flat-field spectrograph’s size shorter for the convenience of use, a ray-tracing code is set to research the influence of the concave grating’s parameter on the spectrum imaging when the incident distance is 155 mm and the focusing surface is still flat. It is found that for the concave grating with curvature radius of 5 649 mm and 1/1 200 nm nominal spacing of the grooves, the angle of incidence is 87.5°, when the incident distance is 155 mm, the focus parameter is -21/R and the coma-type aberration parameter is 4.655102/R2, a better imaging effect within the wave band of 12 ~ 40 nm is realized.
2008,
20.
Abstract:
3D simulation scene is obtained according to formulae of target and background luminance and 3D graphics software. Based on the simulation scene, tracking and identifying process of dynamic laser beam pointing system is studied. Several errors in tracking and aiming process and effects of scale and target imaging attitude in the scene on process are concerned. The construction of 3D scene and image process methods are proved correct by comparing simulation results with theoretic results of the tracking error of moving top of head edge. Head edge tracking is studied and enough tracking precise is achieved for laser beam pointing system.
3D simulation scene is obtained according to formulae of target and background luminance and 3D graphics software. Based on the simulation scene, tracking and identifying process of dynamic laser beam pointing system is studied. Several errors in tracking and aiming process and effects of scale and target imaging attitude in the scene on process are concerned. The construction of 3D scene and image process methods are proved correct by comparing simulation results with theoretic results of the tracking error of moving top of head edge. Head edge tracking is studied and enough tracking precise is achieved for laser beam pointing system.
2008,
20.
Abstract:
In the spectrometer, a cone, used to mount eight multilayer-mirrors, was combined with a central collimation device to obtain the required angles of multilayer-mirrors. Therefore the system could be collimated easily as a whole. 3-D model of the spectrometer was created and its finite-element analysis was completed by using ANSYS. Static analysis results show that the biggest distortion on the collimation device is 0.016 mm in the direction of y axis, which is the effect of gravitation and might be eliminated by increasing the thickness of the part. Besides, model analysis could identify some noises that should be avoided in operational environment. Those all are theoretical foundation for spectrometer’s precision.
In the spectrometer, a cone, used to mount eight multilayer-mirrors, was combined with a central collimation device to obtain the required angles of multilayer-mirrors. Therefore the system could be collimated easily as a whole. 3-D model of the spectrometer was created and its finite-element analysis was completed by using ANSYS. Static analysis results show that the biggest distortion on the collimation device is 0.016 mm in the direction of y axis, which is the effect of gravitation and might be eliminated by increasing the thickness of the part. Besides, model analysis could identify some noises that should be avoided in operational environment. Those all are theoretical foundation for spectrometer’s precision.
2008,
20.
Abstract:
In order to compensate for the nonsphericalsymmetric heat flux in the hohlraum, auxiliary heating is usually applied to the outside wall of the hohlraum during the cooling process. A one-dimensional heat exchange theoretical model has been proposed in the indirect-drive target, to analyze the required auxiliary heat flux. With a two dimensional axi-symmetric model, the auxiliary heating mechanism has been simulated by FLUENT code. The optimum heat flux which is 635 Ｗ/m２ has been obtained as the heaters around the outside of the hohlraum about 1.3 mm above and below the mid-plane. The result is in good agreement with the theoretical model．
In order to compensate for the nonsphericalsymmetric heat flux in the hohlraum, auxiliary heating is usually applied to the outside wall of the hohlraum during the cooling process. A one-dimensional heat exchange theoretical model has been proposed in the indirect-drive target, to analyze the required auxiliary heat flux. With a two dimensional axi-symmetric model, the auxiliary heating mechanism has been simulated by FLUENT code. The optimum heat flux which is 635 Ｗ/m２ has been obtained as the heaters around the outside of the hohlraum about 1.3 mm above and below the mid-plane. The result is in good agreement with the theoretical model．
Measurement of growth kinetics of KDP prismatic faces with laser-polarization-interference technique
2008,
20.
Abstract:
The normal growth rate of KDP prismatic faces was measured in real time using laser- polarization- interference technique. Effect of supersaturation control on the real time measurement of dead zone of KDP prismatic faces was studied. It was found that the birefringence variation with temperature affected the dead zone curve. The dependence of face growth rate and dead zone on supersaturation was studied with solutiens of different impurity antents and different saturation temperature. The growth kinetics was further discussed with C-V model and K-M model. The relationship between optical quality and growth rate was discussed. It is considered the dead zone related to traditional temperature-decreasing method and the linear zone related to rapid growth method, respectively, should be confi
The normal growth rate of KDP prismatic faces was measured in real time using laser- polarization- interference technique. Effect of supersaturation control on the real time measurement of dead zone of KDP prismatic faces was studied. It was found that the birefringence variation with temperature affected the dead zone curve. The dependence of face growth rate and dead zone on supersaturation was studied with solutiens of different impurity antents and different saturation temperature. The growth kinetics was further discussed with C-V model and K-M model. The relationship between optical quality and growth rate was discussed. It is considered the dead zone related to traditional temperature-decreasing method and the linear zone related to rapid growth method, respectively, should be confi
2008,
20.
Abstract:
Laser beam automatic alignment systems are used to precisely adjust beam lines automatically in the high power laser facility. Based on a laser prototype facility requirement for aligning the cavity mirror, the edge characters of light are quantitatively analyzed by image processing the laser image in aligning cavity mirror of high power laser system. Combined with the light transfer qualitatively analysis of measurement optical system for aligning cavity mirror, the consistency of different curve edges and the circular degree of the laser images are used for quantitatively estimating the azimuth of cavity mirror. When nearly completing the cavity mirror, the circular degree of the laser image is 12.222, and the consistency of different curve edge for one page laser image is 99.62%.
Laser beam automatic alignment systems are used to precisely adjust beam lines automatically in the high power laser facility. Based on a laser prototype facility requirement for aligning the cavity mirror, the edge characters of light are quantitatively analyzed by image processing the laser image in aligning cavity mirror of high power laser system. Combined with the light transfer qualitatively analysis of measurement optical system for aligning cavity mirror, the consistency of different curve edges and the circular degree of the laser images are used for quantitatively estimating the azimuth of cavity mirror. When nearly completing the cavity mirror, the circular degree of the laser image is 12.222, and the consistency of different curve edge for one page laser image is 99.62%.
2008,
20.
Abstract:
The large-aperture interferometer can not be regarded as shift-invariant linear imaging systems since for it has different forms of point-spread function at different field positions. It is necessary to revise the calibration of system transfer function by the method of subaperture stitching. The large field is divided into many isoplanatic regions and the transfer function of each isoplanatic region is measured by standard phase step. Then the revised system transfer function can be expressed as the weight average of the transfer function of each isoplanatic region, whose weight depends on power spectrum of the actual test surface at the corresponding region. The experiment shows that the difference between the revised system transfer function and the zero-field transfer function is large
The large-aperture interferometer can not be regarded as shift-invariant linear imaging systems since for it has different forms of point-spread function at different field positions. It is necessary to revise the calibration of system transfer function by the method of subaperture stitching. The large field is divided into many isoplanatic regions and the transfer function of each isoplanatic region is measured by standard phase step. Then the revised system transfer function can be expressed as the weight average of the transfer function of each isoplanatic region, whose weight depends on power spectrum of the actual test surface at the corresponding region. The experiment shows that the difference between the revised system transfer function and the zero-field transfer function is large
2008,
20.
Abstract:
Magnetic ICF glass targets were prepared by electroless plating technology in which magnetic Ni-P coatings covered the surfaces of ICF glass targets. The effects of mass density of main salt, mass density of reducer, mass density of complexant, temperature and pH value of electrolyte on deposition rate of Ni-P plating and bath stability were studied. Then an optimum process of electroless plating on ICF glass targets, in which mass density of main salt NiSO4 is 30 g/L, mass density of reducer NaH2PO2 is 30 g/L, mass density of complexant Na3C6H5O7 is 50 g/L, temperature is (40±2) ℃ and pH value is 10, has been obtained.
Magnetic ICF glass targets were prepared by electroless plating technology in which magnetic Ni-P coatings covered the surfaces of ICF glass targets. The effects of mass density of main salt, mass density of reducer, mass density of complexant, temperature and pH value of electrolyte on deposition rate of Ni-P plating and bath stability were studied. Then an optimum process of electroless plating on ICF glass targets, in which mass density of main salt NiSO4 is 30 g/L, mass density of reducer NaH2PO2 is 30 g/L, mass density of complexant Na3C6H5O7 is 50 g/L, temperature is (40±2) ℃ and pH value is 10, has been obtained.
2008,
20.
Abstract:
Many parameters of plasma, such as electron temperature and ion density can be calculated according to the voltage-curren characteristics curve measured by Langmuir probe. A plasma scanning power system and a data acquisition system are applied in this experiment which could acquire, save, analyze and display data in real time. The data acquisition system is a virtual instrument system, composed of three sections as data acquisition, analysis and results display. It is used to acquire the Langmuir probe’s current and voltage signals, as well as analyse and process them. The entire testing process finishes in time of ms level. Compared with meanual test, Langmuir probe test based on data acquistion system could gain more accurate data in a larger voltage range(-100~100 V). Moreover, it can
Many parameters of plasma, such as electron temperature and ion density can be calculated according to the voltage-curren characteristics curve measured by Langmuir probe. A plasma scanning power system and a data acquisition system are applied in this experiment which could acquire, save, analyze and display data in real time. The data acquisition system is a virtual instrument system, composed of three sections as data acquisition, analysis and results display. It is used to acquire the Langmuir probe’s current and voltage signals, as well as analyse and process them. The entire testing process finishes in time of ms level. Compared with meanual test, Langmuir probe test based on data acquistion system could gain more accurate data in a larger voltage range(-100~100 V). Moreover, it can
2008,
20.
Abstract:
The stress and adhesion of YbF3 thin film deposited by thermal evaporation have been investigated. The stresses of singlelayer YbF3 thin films at different technical conditions have been evaluated by using a Veeco interferometer. In our experiment, residual stress of YbF3 thin film is tensile. Thermal stress seems to be the main contribution to the residual stress. Deposition method affects the stress of thin film. The stress relaxation is observed in air. The stress of YbF3 thin film increases after heat treatment．
The stress and adhesion of YbF3 thin film deposited by thermal evaporation have been investigated. The stresses of singlelayer YbF3 thin films at different technical conditions have been evaluated by using a Veeco interferometer. In our experiment, residual stress of YbF3 thin film is tensile. Thermal stress seems to be the main contribution to the residual stress. Deposition method affects the stress of thin film. The stress relaxation is observed in air. The stress of YbF3 thin film increases after heat treatment．
2008,
20.
Abstract:
The relation of sampling principle to secondary phase sampling problem is analyzed. Based on Fresnel diffraction principle, the computation method for non-focal position is deduced, a new method, the equivalent source field method, is proposed to rebuild the source field to reflect the phase board encountered by the propagating field. As a results, phase boards as many as possible could be inserted into the transmitting path of the field with second phase factor, and still the accurate output field could be got. Comparing the out field intensity obtained by the equivalent source field method with using the light field analysis formula based on the Fresnel diffraction principle, the result shows that within 100 mm defocus distance, the relative error between the two is less than 10-13, so t
The relation of sampling principle to secondary phase sampling problem is analyzed. Based on Fresnel diffraction principle, the computation method for non-focal position is deduced, a new method, the equivalent source field method, is proposed to rebuild the source field to reflect the phase board encountered by the propagating field. As a results, phase boards as many as possible could be inserted into the transmitting path of the field with second phase factor, and still the accurate output field could be got. Comparing the out field intensity obtained by the equivalent source field method with using the light field analysis formula based on the Fresnel diffraction principle, the result shows that within 100 mm defocus distance, the relative error between the two is less than 10-13, so t
2008,
20.
Abstract:
As one of the most important feartures of CCD, linearity can have great influence on data analysis especially in the region of quantitative calculations. The experimental research on the linearity slope and nonlinear scale of scientific optical CCD related to the application in the ICF field is comprehensively carried out by the maximal deviation method, which shows that the system gain of CCD is dependent on the type of ADC(analog to digital converter) but not on its readout rate and the nonlinear scale is less than 1% when the count is less than 15% of full scale. The calibrated data will be used as the basis of quantitatve calculation and analysis related to our ICF research.
As one of the most important feartures of CCD, linearity can have great influence on data analysis especially in the region of quantitative calculations. The experimental research on the linearity slope and nonlinear scale of scientific optical CCD related to the application in the ICF field is comprehensively carried out by the maximal deviation method, which shows that the system gain of CCD is dependent on the type of ADC(analog to digital converter) but not on its readout rate and the nonlinear scale is less than 1% when the count is less than 15% of full scale. The calibrated data will be used as the basis of quantitatve calculation and analysis related to our ICF research.
2008,
20.
Abstract:
Numerical simulations are conducted on the THz radiation excited from the laserplasma interaction with the help of 2D3V PIC code. A new scheme using multiple laser pulses to enhance the THz radiation is proposed, and the effects of pulse number(1~4) and interval on the radiation power and frequency are investigated. With an incident laser with four pulses irradiaton, THz radiation with power of 7.16 MW is obtained. which is 6 times of that with a single pulse laser irradiation. The pulse width of THz radiation is about 330 fs, and the total enrgy is 1 μＪ．The results show that an incident laser with multiple pulses can enhance the radiation obviously, and with the laser pulse number increasing, the amplitude of the electrostatic wave increases synchronously, which makes the THz radiati
Numerical simulations are conducted on the THz radiation excited from the laserplasma interaction with the help of 2D3V PIC code. A new scheme using multiple laser pulses to enhance the THz radiation is proposed, and the effects of pulse number(1~4) and interval on the radiation power and frequency are investigated. With an incident laser with four pulses irradiaton, THz radiation with power of 7.16 MW is obtained. which is 6 times of that with a single pulse laser irradiation. The pulse width of THz radiation is about 330 fs, and the total enrgy is 1 μＪ．The results show that an incident laser with multiple pulses can enhance the radiation obviously, and with the laser pulse number increasing, the amplitude of the electrostatic wave increases synchronously, which makes the THz radiati
2008,
20.
Abstract:
A fast semi-empirical and semi-analytical method for shielding efficiency (or coupling efficiency) estimation of slot with large length-width ratio is presented. The method is based on coupling theory of small holes and Green’s functions of rectangular cavity excited by magnetic current. The result of the method matches well with that obtained by Micro-Stripes software and the measured result. The relationship between slot position, slot number, cavity volume and the shielding efficiency is analyzed. Calculation result shows that the shielding efficiency will degrade by 6 dB when adding a similar slot, and that when keeping slot length unchanged, shielding efficiency will increase by 1 dB when the length-width radio is two times larger and that the shielding efficiency will rise when the
A fast semi-empirical and semi-analytical method for shielding efficiency (or coupling efficiency) estimation of slot with large length-width ratio is presented. The method is based on coupling theory of small holes and Green’s functions of rectangular cavity excited by magnetic current. The result of the method matches well with that obtained by Micro-Stripes software and the measured result. The relationship between slot position, slot number, cavity volume and the shielding efficiency is analyzed. Calculation result shows that the shielding efficiency will degrade by 6 dB when adding a similar slot, and that when keeping slot length unchanged, shielding efficiency will increase by 1 dB when the length-width radio is two times larger and that the shielding efficiency will rise when the
2008,
20.
Abstract:
With the 2.5D full electromagnetic particle-in-cell code, an S-band inductively-loaded wide-gap cavity relativistic klystron amplifier is proposed and investigated. The effects of the washers/rods parameters on intense relativistic electron beam modulation are given. Simulation results show that wide-gap cavity can extend beam/cavity interacting duration and increase the efficiency. The increase in potential energy of wide gap can be prevented by the washers/rods return current structure. Making use of a 500 keV, 6 kA electron beam, about 4.5 kA modulation current and a microwave with power of 1.2 GW and efficiency of 40% are obtained.
With the 2.5D full electromagnetic particle-in-cell code, an S-band inductively-loaded wide-gap cavity relativistic klystron amplifier is proposed and investigated. The effects of the washers/rods parameters on intense relativistic electron beam modulation are given. Simulation results show that wide-gap cavity can extend beam/cavity interacting duration and increase the efficiency. The increase in potential energy of wide gap can be prevented by the washers/rods return current structure. Making use of a 500 keV, 6 kA electron beam, about 4.5 kA modulation current and a microwave with power of 1.2 GW and efficiency of 40% are obtained.
2008,
20.
Abstract:
The thermal distortion effect of resonator mirror in high power gas lasers was investigated. In terms of the method of time discreteness, a 3D physical optic loaded model for folded confocal unstable resonators in negative branch and ANSYS models for thermal effects was used to couple the fast-varying cavity modes and slow-varying physics to mirror distortion. We sloved the interaction between the thermal distortion of mirror and cavity modes. It was shown that, in 16 s running, the change of beam quality was less 1.5 times of diffraction limit for Si mirror, while that is 4 for SiO2 mirror. It is concluded that Si mirror works well than the SiO2 mirror in this kind of designs.
The thermal distortion effect of resonator mirror in high power gas lasers was investigated. In terms of the method of time discreteness, a 3D physical optic loaded model for folded confocal unstable resonators in negative branch and ANSYS models for thermal effects was used to couple the fast-varying cavity modes and slow-varying physics to mirror distortion. We sloved the interaction between the thermal distortion of mirror and cavity modes. It was shown that, in 16 s running, the change of beam quality was less 1.5 times of diffraction limit for Si mirror, while that is 4 for SiO2 mirror. It is concluded that Si mirror works well than the SiO2 mirror in this kind of designs.
2008,
20.
Abstract:
A coaxial reflex triode oscillator for high power microwave generation is proposed and studied by numerical simulation. In the proposed oscillator, a small cylindrical conductor is added on the cathode along the centreline. Thus electric gradient is formed in the interaction region. This is benefical to the reflection of electrons between the real and virtual cathode. For an electron beam of 590 kV and 19.1 kA, by optimizing of structure parameters, the efficiency can reach 15% at an output power of 1.7 GW at 3.62 GHz. Preliminary analysis of the physical mechanism shows that microwave generation comes mainly from the oscillations of the reflex electrons．
A coaxial reflex triode oscillator for high power microwave generation is proposed and studied by numerical simulation. In the proposed oscillator, a small cylindrical conductor is added on the cathode along the centreline. Thus electric gradient is formed in the interaction region. This is benefical to the reflection of electrons between the real and virtual cathode. For an electron beam of 590 kV and 19.1 kA, by optimizing of structure parameters, the efficiency can reach 15% at an output power of 1.7 GW at 3.62 GHz. Preliminary analysis of the physical mechanism shows that microwave generation comes mainly from the oscillations of the reflex electrons．
2008,
20.
Abstract:
This paper has introduced the development of the transverse bunch-by-bunch measurement and feedback system, including the experiment of damping the coupled bunch instability. Some key technologies on the system have been introduced: the vector calculation module as a signal processing module used to adjust the phase of the feedback signals, the feedback kicker cavity and the notch filter used to filter the DC component and revolution frequencies component in a signal and save the feedback power. The result of the feedback experiment is mentioned: the instability oscillation was damped when the feedback system was on.
This paper has introduced the development of the transverse bunch-by-bunch measurement and feedback system, including the experiment of damping the coupled bunch instability. Some key technologies on the system have been introduced: the vector calculation module as a signal processing module used to adjust the phase of the feedback signals, the feedback kicker cavity and the notch filter used to filter the DC component and revolution frequencies component in a signal and save the feedback power. The result of the feedback experiment is mentioned: the instability oscillation was damped when the feedback system was on.
2008,
20.
Abstract:
The RF design of a 201.25 MHz, 750 keV RFQ injector is described. A four-rod structure is chosen for the RF design. The essential parameters are obtained from the beam dynamics design. The structure parameters, including the height, width, thickness, distance，shape of supporting arms, radius of outer cavity, are optimized by numerical simulation. When the inter-electrode voltage is 80 kV, the peak power loss is 115.95 kW, the dipole factor is 1.004 and the field flatness is within 3.5%. The result of the RF structure design satisfies the physics requirement well.
The RF design of a 201.25 MHz, 750 keV RFQ injector is described. A four-rod structure is chosen for the RF design. The essential parameters are obtained from the beam dynamics design. The structure parameters, including the height, width, thickness, distance，shape of supporting arms, radius of outer cavity, are optimized by numerical simulation. When the inter-electrode voltage is 80 kV, the peak power loss is 115.95 kW, the dipole factor is 1.004 and the field flatness is within 3.5%. The result of the RF structure design satisfies the physics requirement well.
