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RSS2003 Vol. 15, No. 03
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2003,
15.
Abstract:
Based on the explosive emission model, the self-consistent and 2.5 dimensional electromagnetic particle-in-cell MAGIC code was employed to simulate the dynamics of the particles, including electron and proton, in a planar magnetically insulated ion diode for highpower pulsed ion beams. Time-dependent diode characteristics, spatial and phasespace distributions of the charged particles, as well as the distribution of the net charge density and the electric field in the anode-cathode(AC) gap are presented at a diode voltage of 300kV and a double intensity of the critical magnetic field. The results show that the extracted ion current density is five times larger than the single species limited ion current density according to Child-Langmuir law. The virtual cathode forms in the vicinity of
Based on the explosive emission model, the self-consistent and 2.5 dimensional electromagnetic particle-in-cell MAGIC code was employed to simulate the dynamics of the particles, including electron and proton, in a planar magnetically insulated ion diode for highpower pulsed ion beams. Time-dependent diode characteristics, spatial and phasespace distributions of the charged particles, as well as the distribution of the net charge density and the electric field in the anode-cathode(AC) gap are presented at a diode voltage of 300kV and a double intensity of the critical magnetic field. The results show that the extracted ion current density is five times larger than the single species limited ion current density according to Child-Langmuir law. The virtual cathode forms in the vicinity of
2003,
15.
Abstract:
This paper presents a new method for measuring the timing jitter of micropulse with high sensitivity. Using the traditional four-stripline beam monitor which has been used to measure the electron beam position and electron charge, and by comparing the phase of the induced signals with the reference signal, the phase jitter, also the timing jitter are obtained.
This paper presents a new method for measuring the timing jitter of micropulse with high sensitivity. Using the traditional four-stripline beam monitor which has been used to measure the electron beam position and electron charge, and by comparing the phase of the induced signals with the reference signal, the phase jitter, also the timing jitter are obtained.
2003,
15.
Abstract:
It’s very important to get information on beam profile for researching of accelerator. Measurement technology of beam profile of the highcurrent shortpulse electronbeam such as Faraday cup array, Multiwire method, bremsstrahlung radiation, cerenkov radition and optical transition radiation are reviewed in this paper.
It’s very important to get information on beam profile for researching of accelerator. Measurement technology of beam profile of the highcurrent shortpulse electronbeam such as Faraday cup array, Multiwire method, bremsstrahlung radiation, cerenkov radition and optical transition radiation are reviewed in this paper.
2003,
15.
Abstract:
Amorphous hydrogenated silicon carbide(aSiC:H) films were prepared by the reactive sputtering method,which were irradiated by high energy neutrons.Using resistivity,Raman scattering,and infrared transimissing spectroscopy,the authors investigated the neutrons irradiation effects on the structure and properties of a-SiC:H films.There were superfluous carbons in the films.It is found that the increase of irradiation doses results in the increase of SP-2C=C bonds in a-SiC:H films,i.e.the carbons in the films tended to graphitization.In general,the graphitization of carbons led to the decrease of resistivity sharply,but the decrease of resistivity in this paper was smooth .The phenomenon can be interpreted according to the model that the carriers were trapped by the defects.
Amorphous hydrogenated silicon carbide(aSiC:H) films were prepared by the reactive sputtering method,which were irradiated by high energy neutrons.Using resistivity,Raman scattering,and infrared transimissing spectroscopy,the authors investigated the neutrons irradiation effects on the structure and properties of a-SiC:H films.There were superfluous carbons in the films.It is found that the increase of irradiation doses results in the increase of SP-2C=C bonds in a-SiC:H films,i.e.the carbons in the films tended to graphitization.In general,the graphitization of carbons led to the decrease of resistivity sharply,but the decrease of resistivity in this paper was smooth .The phenomenon can be interpreted according to the model that the carriers were trapped by the defects.
2003,
15.
Abstract:
The plasma wave nonlinear effect of IonChannel Electron Cyclotron Maser (ICECM) is investigated. Using these methods of fluid theory and self nonlinear theory, the micromechanism in ICECM are analyzed. Studies find that the longitudinal focus is intensified and the beamwave interact efficiency is remarkably increased. Numerical calculations show that , for middle ion density and the electron beam of 1.5kA and 1MV, the scattering wave frequency and the output power in ICECM system can achieve 280GHz and 200MW respectively.
The plasma wave nonlinear effect of IonChannel Electron Cyclotron Maser (ICECM) is investigated. Using these methods of fluid theory and self nonlinear theory, the micromechanism in ICECM are analyzed. Studies find that the longitudinal focus is intensified and the beamwave interact efficiency is remarkably increased. Numerical calculations show that , for middle ion density and the electron beam of 1.5kA and 1MV, the scattering wave frequency and the output power in ICECM system can achieve 280GHz and 200MW respectively.
2003,
15.
Abstract:
This paper presents an estimate method on radiationinduced charge effect from LC4007A and LC4007B device in lowdose space environment. According to the result, on the basis of MILSTD 883C, Test Method 1019.4, 60Co irradiation plus 25℃ annealing can provide effects of oxidetrip charge on MOS device response in space that is estimated significantly less conservative than MILSTD 883C, Test Method 1019.4. The possible phenomena of oneweek hightemperature anneal in MILSTD 883C, Test Method 1019.4 detecting interfacetrip related failures in MOS devices were discussed.
This paper presents an estimate method on radiationinduced charge effect from LC4007A and LC4007B device in lowdose space environment. According to the result, on the basis of MILSTD 883C, Test Method 1019.4, 60Co irradiation plus 25℃ annealing can provide effects of oxidetrip charge on MOS device response in space that is estimated significantly less conservative than MILSTD 883C, Test Method 1019.4. The possible phenomena of oneweek hightemperature anneal in MILSTD 883C, Test Method 1019.4 detecting interfacetrip related failures in MOS devices were discussed.
2003,
15.
Abstract:
Aiming at the triplet quadrupole system of 9 MeV traveling wave ＬＩＮＡＣ used for customs container inspection system, this paper analyses that the influences of beam focusing characteristics between quadrupole and skew quadrupole system. Along with analysis of focusing parameters, the errors of manufacture and installation are made for triplet quadrupoles. Finally, the method of choosing parameters and the reasonable tolerance requirement are described theoretically. Calculations mentioned above are accomplished by using the beamdynamics program TRANSPORT.
Aiming at the triplet quadrupole system of 9 MeV traveling wave ＬＩＮＡＣ used for customs container inspection system, this paper analyses that the influences of beam focusing characteristics between quadrupole and skew quadrupole system. Along with analysis of focusing parameters, the errors of manufacture and installation are made for triplet quadrupoles. Finally, the method of choosing parameters and the reasonable tolerance requirement are described theoretically. Calculations mentioned above are accomplished by using the beamdynamics program TRANSPORT.
2003,
15.
Abstract:
This paper reported the results of the investigation of a 200kV/100kA low jtter low prefire probability ring rail field distortion switch. Its jitter was less than 2 ns when its working voltage was larger than 70% of selfbreakdown voltage. When its working voltage was greater than 85% of selfbreakdown voltage its jitter was less than 1ns if the mixture of Ar, N2 and SF6N2, SF6Ar in which the percentage of SF6 was less than 50% was used as dielectric. Its maxium derivation of selfbreakdown voltage was less than 4% of selfbreakdown voltage. It is a multichannel switch and the number of discharging channel was more than 3. The results of selfbreakdown and triggering experiments working with Ar, N2, SF6 and SF6N2, SF6Ar mixtures were introduced．
This paper reported the results of the investigation of a 200kV/100kA low jtter low prefire probability ring rail field distortion switch. Its jitter was less than 2 ns when its working voltage was larger than 70% of selfbreakdown voltage. When its working voltage was greater than 85% of selfbreakdown voltage its jitter was less than 1ns if the mixture of Ar, N2 and SF6N2, SF6Ar in which the percentage of SF6 was less than 50% was used as dielectric. Its maxium derivation of selfbreakdown voltage was less than 4% of selfbreakdown voltage. It is a multichannel switch and the number of discharging channel was more than 3. The results of selfbreakdown and triggering experiments working with Ar, N2, SF6 and SF6N2, SF6Ar mixtures were introduced．
2003,
15.
Abstract:
Xray is always returned to visible light for detection by scintillator in high energy radiography systems. The system spatial resolution is affected by scintillator thickness, material and energy of the input X photons. This influence is analyzed theoretically and the calculating model is built. For providing the parameters to optimize the design of the system, the relation between the scintillator spatial resolution and the scintillator thickness, material and energy of the input X photon is calculated. The increasing of scintillator thickness will reduce the spatial resolution while the increasing of input X photon energy will raise it. The spatial resolution of BGO is higher than that of CsI:Tl with same thickness.
Xray is always returned to visible light for detection by scintillator in high energy radiography systems. The system spatial resolution is affected by scintillator thickness, material and energy of the input X photons. This influence is analyzed theoretically and the calculating model is built. For providing the parameters to optimize the design of the system, the relation between the scintillator spatial resolution and the scintillator thickness, material and energy of the input X photon is calculated. The increasing of scintillator thickness will reduce the spatial resolution while the increasing of input X photon energy will raise it. The spatial resolution of BGO is higher than that of CsI:Tl with same thickness.
2003,
15.
Abstract:
The experimental apparatus of coaxial water capacitor was set up in microsecond charging condition. Some experiments were done in this device, the voltage of breakdown of coaxial capacitor is measured with positive and negative pulse voltage to charge. Comparing the experimental results with the calculating results, the error of the negative breakdownvoltage is larger and the error of positive breakdownvoltage is less than about 20%. Furthermore, when the resistivity of the water drop to 5MΩ·cm from 13MΩ·cm, the breakdownvoltage of the coaxial water capacitor did not change approximately. The results of experiment are analyzed and are important in design of water dielectric Blumlein pulse forming line with microsecond charging.
The experimental apparatus of coaxial water capacitor was set up in microsecond charging condition. Some experiments were done in this device, the voltage of breakdown of coaxial capacitor is measured with positive and negative pulse voltage to charge. Comparing the experimental results with the calculating results, the error of the negative breakdownvoltage is larger and the error of positive breakdownvoltage is less than about 20%. Furthermore, when the resistivity of the water drop to 5MΩ·cm from 13MΩ·cm, the breakdownvoltage of the coaxial water capacitor did not change approximately. The results of experiment are analyzed and are important in design of water dielectric Blumlein pulse forming line with microsecond charging.
2003,
15.
Abstract:
Plasma characteristics of an RF ion source were investigated by emission spectroscopy. The RF ion source, applied in ZF200keV neutron generator, is an orbicular discharge RF ion source coupled with inductance. The spectral line intensities of the first three atomic lines in hydrogen Balmer series in different moment of RF ion source plasma, were measured with calibrated optical multichannel analyzer. Some plasma parameters in relevant time, including electron temperature, hydrogen atom density and hydrogen ion density, were calculated and analyzed using partial local thermodynamic equilibrium theory.
Plasma characteristics of an RF ion source were investigated by emission spectroscopy. The RF ion source, applied in ZF200keV neutron generator, is an orbicular discharge RF ion source coupled with inductance. The spectral line intensities of the first three atomic lines in hydrogen Balmer series in different moment of RF ion source plasma, were measured with calibrated optical multichannel analyzer. Some plasma parameters in relevant time, including electron temperature, hydrogen atom density and hydrogen ion density, were calculated and analyzed using partial local thermodynamic equilibrium theory.
2003,
15.
Abstract:
Beams emittance is a very important parameter of the RFinjector, it is growth due to RF field space charge effects and so on. The analytical expression of beams emittance in RF injector has been given in this paper, it shows that beams emittance is various in RF injector. The dependences of beams emittance at the exit of a 1+1/2 cell photo-cathode injector on field strength, initial phase, beam size, bunch length and charge, etc are researched respectively using SUPERFISH and GPT programs. Beams emitance of less than 2πmm·mrad can be obtained by appropriately choosing these parameters.
Beams emittance is a very important parameter of the RFinjector, it is growth due to RF field space charge effects and so on. The analytical expression of beams emittance in RF injector has been given in this paper, it shows that beams emittance is various in RF injector. The dependences of beams emittance at the exit of a 1+1/2 cell photo-cathode injector on field strength, initial phase, beam size, bunch length and charge, etc are researched respectively using SUPERFISH and GPT programs. Beams emitance of less than 2πmm·mrad can be obtained by appropriately choosing these parameters.
2003,
15.
Abstract:
The damaged spot of copper film mirror irradiated by pulsed Nd:YAG laser is analyzed using an optical microscope. The periodic damage ring is found at the laser irradiation spot, the average spacing of these rings is about 45μm. The damage ring can be observed obviously only in the periphery of the laser spot under lower laser energy density； as laser fluence increases, the periodic damage rings cover the whole laser spot； under higher laser energy density, the whole film is damaged and the rings disappear. A Fresnel diffraction model is used to explain the appearance of these rings. The laser beam is diffracted by the aperture in the optic path, laser intensity distribution at the copper film mirror becomes periodic rings and damage ripple pattern forms instantly with the laser ablatio
The damaged spot of copper film mirror irradiated by pulsed Nd:YAG laser is analyzed using an optical microscope. The periodic damage ring is found at the laser irradiation spot, the average spacing of these rings is about 45μm. The damage ring can be observed obviously only in the periphery of the laser spot under lower laser energy density； as laser fluence increases, the periodic damage rings cover the whole laser spot； under higher laser energy density, the whole film is damaged and the rings disappear. A Fresnel diffraction model is used to explain the appearance of these rings. The laser beam is diffracted by the aperture in the optic path, laser intensity distribution at the copper film mirror becomes periodic rings and damage ripple pattern forms instantly with the laser ablatio
2003,
15.
Abstract:
Effect of pH value on the scatter particles in KDP crystal was discussed in this paper. The results showed that scatter particles have different size and density at different growth pH value. It can be seen from the results that the scatter particles are larger and have lower density at high pH value comparing with those at low pH value. The reason can be attributed to that at different pH value the existence of ligand of Fe is not the same, which caused the impurities formed on the moving steps are not same. It is these kinds of impurities formed by ligand of Fe caused the inclusions in KDP crystals.
Effect of pH value on the scatter particles in KDP crystal was discussed in this paper. The results showed that scatter particles have different size and density at different growth pH value. It can be seen from the results that the scatter particles are larger and have lower density at high pH value comparing with those at low pH value. The reason can be attributed to that at different pH value the existence of ligand of Fe is not the same, which caused the impurities formed on the moving steps are not same. It is these kinds of impurities formed by ligand of Fe caused the inclusions in KDP crystals.
2003,
15.
Abstract:
Based on the discussion of the law of the interaction between opticfield and fluidfield, this paper uses the physical model of highenergy laser beam crossing through the two dimension supersonic free shot flow. We obtained density map and OPD map of fluid field and far field distribution of laser beam. We discussed: the disturbance of the fluidfield caused by radiation heating and the changing of laser beam intensity after the beam passing through the fluid field and propagating 2km in the still atmosphere. The results show that there's a distinct influence of fluidfield on opticfield. Also we got that in studying the interaction of supersonic free shot fluidfield with highenergy laser we can neglect the radiation heating when the air is not ionized．
Based on the discussion of the law of the interaction between opticfield and fluidfield, this paper uses the physical model of highenergy laser beam crossing through the two dimension supersonic free shot flow. We obtained density map and OPD map of fluid field and far field distribution of laser beam. We discussed: the disturbance of the fluidfield caused by radiation heating and the changing of laser beam intensity after the beam passing through the fluid field and propagating 2km in the still atmosphere. The results show that there's a distinct influence of fluidfield on opticfield. Also we got that in studying the interaction of supersonic free shot fluidfield with highenergy laser we can neglect the radiation heating when the air is not ionized．
2003,
15.
Abstract:
To insure reliable and accurate measurement results of mirror angular displacement for COIL resonator, indirect measurement was found using electronic autocollimator. Measurement results show that thermal radiation is main reason of mirror angular displacement and results in the beam spot drift for COIL. Adopting measures, the mirror angular displacement and the beam spot drift are obviously reduced. Experiments verify that the measurement method is reasonable and reliable.
To insure reliable and accurate measurement results of mirror angular displacement for COIL resonator, indirect measurement was found using electronic autocollimator. Measurement results show that thermal radiation is main reason of mirror angular displacement and results in the beam spot drift for COIL. Adopting measures, the mirror angular displacement and the beam spot drift are obviously reduced. Experiments verify that the measurement method is reasonable and reliable.
2003,
15.
Abstract:
The concept of coherent coupling of optics and mechanics is presented here and its mechanism is analyzed. The coupled wave theory of nonlinear optics is adopted to establish nonlinear dynamics model describing generation and evolution of coherent acoustic wave in optical materials. The stress induced by SBS process is calculated in steady state case and the damage threshold theory for transparent materials is presented to study the dependence of damage threshold on Stokes laser fluence.The research shows that the SBS induced stress would cause material breakdown which most probably happens in the entrance surface of pump laser, and the Stokes laser does not play an important role in the damage thresholds in steady case. Finally, the future work is outlined to promote the study on coherent
The concept of coherent coupling of optics and mechanics is presented here and its mechanism is analyzed. The coupled wave theory of nonlinear optics is adopted to establish nonlinear dynamics model describing generation and evolution of coherent acoustic wave in optical materials. The stress induced by SBS process is calculated in steady state case and the damage threshold theory for transparent materials is presented to study the dependence of damage threshold on Stokes laser fluence.The research shows that the SBS induced stress would cause material breakdown which most probably happens in the entrance surface of pump laser, and the Stokes laser does not play an important role in the damage thresholds in steady case. Finally, the future work is outlined to promote the study on coherent
2003,
15.
Abstract:
Taking advantage of a module of impacted sectioned surface discharge source, the changes of resistance, inductance and energy deposition efficiency of the circuit under various experimental parameters including charging voltage, capacitance and gas pressure have been studied. The framing photographs of discharge plasma channel under different conditions have been obtained. The effect of the discharge plasma movement on energy deposition efficiency has been analyzed and the measures for improving the deposition efficiency have been given.
Taking advantage of a module of impacted sectioned surface discharge source, the changes of resistance, inductance and energy deposition efficiency of the circuit under various experimental parameters including charging voltage, capacitance and gas pressure have been studied. The framing photographs of discharge plasma channel under different conditions have been obtained. The effect of the discharge plasma movement on energy deposition efficiency has been analyzed and the measures for improving the deposition efficiency have been given.
2003,
15.
Abstract:
With the combination of CCD imaging unit and traditional multiimage camera to measure far-field distribution of laser output, the reconstruction algorithm for focal spot of high power solid state laser output was described. The geometric cores of these focal spots was abstracted to center these spots by virtue of edge computational kernel applied in the field of image processing, nesting algorithm for focal spot reconstruction is put forward. It can precisely center these spots even if they are saturated partially and instantly reconstruct original focal spot, which makes it feasible to provide realtime data for laser control.
With the combination of CCD imaging unit and traditional multiimage camera to measure far-field distribution of laser output, the reconstruction algorithm for focal spot of high power solid state laser output was described. The geometric cores of these focal spots was abstracted to center these spots by virtue of edge computational kernel applied in the field of image processing, nesting algorithm for focal spot reconstruction is put forward. It can precisely center these spots even if they are saturated partially and instantly reconstruct original focal spot, which makes it feasible to provide realtime data for laser control.
2003,
15.
Abstract:
Through the study of the effect of the static wavefront distortion of optics elements in the multipass amplification system, the phase RMS gradient meeting the demand of the focusing is given, which is about 0.007λ/cm. The maximum phase error value of the optics elements that the system allowed is also shown. And the addinglaws of wavefront phase by the laser beam transmission program is also checkd. As the result, this paper provides some references for the study of Shenguang facility about the elements demands.
Through the study of the effect of the static wavefront distortion of optics elements in the multipass amplification system, the phase RMS gradient meeting the demand of the focusing is given, which is about 0.007λ/cm. The maximum phase error value of the optics elements that the system allowed is also shown. And the addinglaws of wavefront phase by the laser beam transmission program is also checkd. As the result, this paper provides some references for the study of Shenguang facility about the elements demands.
2003,
15.
Abstract:
In experiment, three systems were designed to measure the energy distribution of the laser beam in the far field. Under the same conditions, the far field of the laser beam was measured independently by three instruments: long focus lens, rattle pair and multipleimage cameras. After compare and analyze the results, a new system was put forward in which a long focus lens with a pair of smallangle wedge was used. It only needs corresponding data processing for a focalspots line which was on the focal plane. The new system satisfied requirement for aberration and predigested image data processing.
In experiment, three systems were designed to measure the energy distribution of the laser beam in the far field. Under the same conditions, the far field of the laser beam was measured independently by three instruments: long focus lens, rattle pair and multipleimage cameras. After compare and analyze the results, a new system was put forward in which a long focus lens with a pair of smallangle wedge was used. It only needs corresponding data processing for a focalspots line which was on the focal plane. The new system satisfied requirement for aberration and predigested image data processing.
2003,
15.
Abstract:
According to the working principle of the holographic lens, two of the most important parameters, focusing characteristics and diffraction efficiency, were analyzed in this paper. And the factors, which influence the two parameters, were discussed. Furthermore, the author discussed the proximate analysis methods, which was used in the numerical calculation process. The advance of the holographic lens used as a sampler was also discussed.
According to the working principle of the holographic lens, two of the most important parameters, focusing characteristics and diffraction efficiency, were analyzed in this paper. And the factors, which influence the two parameters, were discussed. Furthermore, the author discussed the proximate analysis methods, which was used in the numerical calculation process. The advance of the holographic lens used as a sampler was also discussed.
2003,
15.
Abstract:
The finite-difference time-domain method is used to research the rule of the electromagnetic pulse coupled to the cavity with different kinds of holes on it. The coupling effects of EMP on square, rectangle hole，multi-hole and the rule of EＭＰ having different polarized direction coupled to rectangle hole are described. Computational data indicate: (1) The energy coupled to the square hole of EＭＰ is less; (2) When the polarized direction of the incident wave are parallel to the short side of the hole, the energy coupled will attain the maximum; (3) The hole area being the same, the energy coupled to the multihole are less than that to the single hole.
The finite-difference time-domain method is used to research the rule of the electromagnetic pulse coupled to the cavity with different kinds of holes on it. The coupling effects of EMP on square, rectangle hole，multi-hole and the rule of EＭＰ having different polarized direction coupled to rectangle hole are described. Computational data indicate: (1) The energy coupled to the square hole of EＭＰ is less; (2) When the polarized direction of the incident wave are parallel to the short side of the hole, the energy coupled will attain the maximum; (3) The hole area being the same, the energy coupled to the multihole are less than that to the single hole.
2003,
15.
Abstract:
The EMP radiator is the key part of the portable measurement equipment of electric field shielding efficacy . In this dissertation a plan of a small-sized EMP radiator is provided, and the radioactive near field emitted by radiator is analyzed by the finitedifference timedomain algorithm. It is demonstrated that if the high voltage pulse generator produces voltage pulse of he form of double exponential function, the waveform of nearfield produced by the EMP radiator will be double exponential waveform. The nearfield parameters accord with measurement equipment requirements. So the plan of EMP reaiator is feasible.
The EMP radiator is the key part of the portable measurement equipment of electric field shielding efficacy . In this dissertation a plan of a small-sized EMP radiator is provided, and the radioactive near field emitted by radiator is analyzed by the finitedifference timedomain algorithm. It is demonstrated that if the high voltage pulse generator produces voltage pulse of he form of double exponential function, the waveform of nearfield produced by the EMP radiator will be double exponential waveform. The nearfield parameters accord with measurement equipment requirements. So the plan of EMP reaiator is feasible.
2003,
15.
Abstract:
The operating process of the multiwave Cerenkov generator with a resonant cavity is simulated when being filled with He gas at various density by PIC method. The generation mechanism of the plasma and its effects on the output microwave are analyzed. The results reveal the plasma is produced owing to the collision ionization of the He gas filled in the tube by the relativistic electron beam and its avalanche ionization effect. Due to the improvement of the beam transporting and bunching by the ions tunnel, the starting oscillation time can decrease as well as the energy conversion efficiency be enhanced when increasing the He gas density in a certain range; increasing the He gas density further can result in adverse effects, even induce pulse shortening phenomenon.
The operating process of the multiwave Cerenkov generator with a resonant cavity is simulated when being filled with He gas at various density by PIC method. The generation mechanism of the plasma and its effects on the output microwave are analyzed. The results reveal the plasma is produced owing to the collision ionization of the He gas filled in the tube by the relativistic electron beam and its avalanche ionization effect. Due to the improvement of the beam transporting and bunching by the ions tunnel, the starting oscillation time can decrease as well as the energy conversion efficiency be enhanced when increasing the He gas density in a certain range; increasing the He gas density further can result in adverse effects, even induce pulse shortening phenomenon.
