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RSS1999 Vol. 11, No. 05
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1999,
11.
Abstract:
A new high power microwave source,the axial acceletron is presented in this paper. Compared with the radial acceletron, an acceleration region is added after the diode/oscillator and radial acceleration is changed to axial acceleration.The bunching and radiation of the electron beam in the device are investigated. It is found that the electron beam may approach ideal bunching, each harmonic current of the beam may reach about 5.6 times of the initial direct current in the nonrelativistic regime. High power microwave pulses with tunable frequency can be generated by postaccelerating the electron beam and carefully designing the extraction cavity.
A new high power microwave source,the axial acceletron is presented in this paper. Compared with the radial acceletron, an acceleration region is added after the diode/oscillator and radial acceleration is changed to axial acceleration.The bunching and radiation of the electron beam in the device are investigated. It is found that the electron beam may approach ideal bunching, each harmonic current of the beam may reach about 5.6 times of the initial direct current in the nonrelativistic regime. High power microwave pulses with tunable frequency can be generated by postaccelerating the electron beam and carefully designing the extraction cavity.
1999,
11.
Abstract:
A well configured Xband multiw ave cerenkov generator is investigated experimentally, and microwave radiation is achieved through the expected physics mechanism. The microwave frequency ranges from 9.59GHz to 10.4GHz in the experiment. The measured radiation efficiency is higher than 10%, with a power level over 100MW.
A well configured Xband multiw ave cerenkov generator is investigated experimentally, and microwave radiation is achieved through the expected physics mechanism. The microwave frequency ranges from 9.59GHz to 10.4GHz in the experiment. The measured radiation efficiency is higher than 10%, with a power level over 100MW.
1999,
11.
Abstract:
Using a twodimension fully electromagnetic ParticleinCell(PIC) simulation，the relativistic magnetically insulated transmission line oscillator (ＭILO) designed by Phillips laboratory is studied. A power output of about 1.5GW at 1.1GHz can be generated with this source when input voltage is 500kV and input current is 60kA. In addition we have researched the effect of changing the parameter of MILO on the work performance of MILO is researched．
Using a twodimension fully electromagnetic ParticleinCell(PIC) simulation，the relativistic magnetically insulated transmission line oscillator (ＭILO) designed by Phillips laboratory is studied. A power output of about 1.5GW at 1.1GHz can be generated with this source when input voltage is 500kV and input current is 60kA. In addition we have researched the effect of changing the parameter of MILO on the work performance of MILO is researched．
1999,
11.
Abstract:
In the paper, the nonlinear theory of relativistic backward wave oscillator(RBWO) with variable couple impedance was built up, the relations of variable couple impedance RBWO efficiency with couple impedance change location and highlow couple impedance rate was numerically modeled and optimized using the nonlinear theory. A xband RBWO with a single step in the couple impedance has been designed and analyzed by use of an electromagnetic particleincell code and investigated experimentally, the preliminary experiment results show that the device efficiency is about twice of the uniform RBWO in the conditions of the same operating parameter.
In the paper, the nonlinear theory of relativistic backward wave oscillator(RBWO) with variable couple impedance was built up, the relations of variable couple impedance RBWO efficiency with couple impedance change location and highlow couple impedance rate was numerically modeled and optimized using the nonlinear theory. A xband RBWO with a single step in the couple impedance has been designed and analyzed by use of an electromagnetic particleincell code and investigated experimentally, the preliminary experiment results show that the device efficiency is about twice of the uniform RBWO in the conditions of the same operating parameter.
1999,
11.
Abstract:
Based on the motion of the single electron whose incident phase is φ0 in standing wave electric field under the small signal condition, the transittime effect of electron beam in π mode standing wave electric field in a multiplecavity resonator is investigated, the expressions of electron load conductance in a multiplecavity resonator are presented , and the effect of the cavity number N on transittime effect in a multiplecavity resonator is discussed.
Based on the motion of the single electron whose incident phase is φ0 in standing wave electric field under the small signal condition, the transittime effect of electron beam in π mode standing wave electric field in a multiplecavity resonator is investigated, the expressions of electron load conductance in a multiplecavity resonator are presented , and the effect of the cavity number N on transittime effect in a multiplecavity resonator is discussed.
1999,
11.
Abstract:
According to the latest experimental results of HPM effect on digital electronic devices, a relation between the HPM pulsewidth(PW) and the upset threshold(UT) of effect obiect is sumaried. The relation suggests that UT decreases with the increasing of PW as the other factors are fixed, wheras, there is a inflection region of UT while PW increasing. The UT changes slowly when the injecting PW is greater than the PW corresponding to the inflection region.
According to the latest experimental results of HPM effect on digital electronic devices, a relation between the HPM pulsewidth(PW) and the upset threshold(UT) of effect obiect is sumaried. The relation suggests that UT decreases with the increasing of PW as the other factors are fixed, wheras, there is a inflection region of UT while PW increasing. The UT changes slowly when the injecting PW is greater than the PW corresponding to the inflection region.
1999,
11.
Abstract:
The spontaneous emission is one important performance of an optical klystron (OK). Using the magnetic field data which were measured from OK on the storage ring of NSRL, spontaneo us emission and small signal gain of the electron beam with different energy spread in OK has been computed in this paper. The results illustrates that OK in storage ring of NSRL can satisfy the experimental requirement.
The spontaneous emission is one important performance of an optical klystron (OK). Using the magnetic field data which were measured from OK on the storage ring of NSRL, spontaneo us emission and small signal gain of the electron beam with different energy spread in OK has been computed in this paper. The results illustrates that OK in storage ring of NSRL can satisfy the experimental requirement.
1999,
11.
Abstract:
The Beijing FEL (BFEL) is a infrared FEL facility based on the rf linac. In order to improve its beam diagnostic system transition radiation has been used instead of the original phosphor target. Beam profile, size, relative position and divergence in transverse were obtained using optical transition radiation (OTR). The principle of transition radiation used for beam diagnosis and the setup for OTR measurement are described. Some preliminary results are presented．
The Beijing FEL (BFEL) is a infrared FEL facility based on the rf linac. In order to improve its beam diagnostic system transition radiation has been used instead of the original phosphor target. Beam profile, size, relative position and divergence in transverse were obtained using optical transition radiation (OTR). The principle of transition radiation used for beam diagnosis and the setup for OTR measurement are described. Some preliminary results are presented．
1999,
11.
Abstract:
High sampling frequency ShackHartmann wavefront sensor is used to measure the dynamic wavefront error in adaptive optics system. Its output signal must be processed by wavefront processor. In this paper, the method of real time processing for high sampling frequency ShackHartmann wavefront sensor was discussed. As an example, the results for 2900 Hz ShackHartmann wavefront sensor was given.
High sampling frequency ShackHartmann wavefront sensor is used to measure the dynamic wavefront error in adaptive optics system. Its output signal must be processed by wavefront processor. In this paper, the method of real time processing for high sampling frequency ShackHartmann wavefront sensor was discussed. As an example, the results for 2900 Hz ShackHartmann wavefront sensor was given.
1999,
11.
Abstract:
In this paper three wavelengths 266nm,289nm,308nm are used for experimental studies of simulation and measurements. Results of simulation show that the effects are larger for twowavelength DIAL but less for threewavelength dual DIAL, if spatial inhomogeneity of aerosol and gradient of backscatter ratio are larger.
In this paper three wavelengths 266nm,289nm,308nm are used for experimental studies of simulation and measurements. Results of simulation show that the effects are larger for twowavelength DIAL but less for threewavelength dual DIAL, if spatial inhomogeneity of aerosol and gradient of backscatter ratio are larger.
1999,
11.
Abstract:
The property of the LD pump source and Cr:LiSAF crystal laser were described. In the optimum collimating the pump light ,we get 41 mW output power, and profiles of pump source and laser output at different positions are studied.
The property of the LD pump source and Cr:LiSAF crystal laser were described. In the optimum collimating the pump light ,we get 41 mW output power, and profiles of pump source and laser output at different positions are studied.
1999,
11.
Abstract:
A diode sidepumped Qswitched Nd:YAG doubleslab oscillator designed for high power solid state laser has been demonstrated. Diode laser power was transferred by a trapezoidal waveguide plate into the slabs and the optical coupler efficiency was 90%. The oscillator was a convexconcave resonator. Highreflection mirror of curvature radius was 3.0m. A VRM of supergaussian was used for output couplers with curvature radius of 3.0m. The output is of single pulse energy 18.23mJ, pulse width 15.25ns and 100Hz repetition rates and beam quality factor. The output beam was a flat topped supergaussian beam.
A diode sidepumped Qswitched Nd:YAG doubleslab oscillator designed for high power solid state laser has been demonstrated. Diode laser power was transferred by a trapezoidal waveguide plate into the slabs and the optical coupler efficiency was 90%. The oscillator was a convexconcave resonator. Highreflection mirror of curvature radius was 3.0m. A VRM of supergaussian was used for output couplers with curvature radius of 3.0m. The output is of single pulse energy 18.23mJ, pulse width 15.25ns and 100Hz repetition rates and beam quality factor. The output beam was a flat topped supergaussian beam.
1999,
11.
Abstract:
Jitter of the laser triggered switch, feedback of the thyratron and output instability of the discharge pumped KrF laser as a frontend were discussed, and solutions were given.
Jitter of the laser triggered switch, feedback of the thyratron and output instability of the discharge pumped KrF laser as a frontend were discussed, and solutions were given.
1999,
11.
Abstract:
A femtosecond Ti:sapphire chirped pulse amplifier with multipass amplification was developed in this paper, new concepts on overcoming gainnarrowing and enhancing amplification efficience are also introduced. Pulses of 25fs duration with 36mJ energy have been produced at repetition rates of 10Hz only under 290mJ doubled frequency Nd:YAG laser pump, which corresponds to 1.4TW peak power．
A femtosecond Ti:sapphire chirped pulse amplifier with multipass amplification was developed in this paper, new concepts on overcoming gainnarrowing and enhancing amplification efficience are also introduced. Pulses of 25fs duration with 36mJ energy have been produced at repetition rates of 10Hz only under 290mJ doubled frequency Nd:YAG laser pump, which corresponds to 1.4TW peak power．
1999,
11.
Abstract:
Deep theoretical analysis and experimental study on diodepumped ring regenerative amplifier have been completed. The diodepumped ring regenerative amplifier has been successfully developed, output energy 0.35mJ, instability＜±5% and total gain 106 have been obtained.
Deep theoretical analysis and experimental study on diodepumped ring regenerative amplifier have been completed. The diodepumped ring regenerative amplifier has been successfully developed, output energy 0.35mJ, instability＜±5% and total gain 106 have been obtained.
1999,
11.
Abstract:
In this paper, the structure of UR90 with aperture output beam for a chemical oxygen iodine laser(COIL) and the properties of its geometry mode are mainly described. A beam quality of 3.2 times diffraction limit was achieved in the experiment when the COIL average output power was approximately 4kW in the case of magnification of 1.695, and then the property of the aperture output beam was analyzed.
In this paper, the structure of UR90 with aperture output beam for a chemical oxygen iodine laser(COIL) and the properties of its geometry mode are mainly described. A beam quality of 3.2 times diffraction limit was achieved in the experiment when the COIL average output power was approximately 4kW in the case of magnification of 1.695, and then the property of the aperture output beam was analyzed.
1999,
11.
Abstract:
The advantage of the single pulse selectors which is driven by high voltage and large current power MOSFETs is introduced. The characteristic phenomena are discovered when the electrooptic crystal is used as a fast electooptic switch and the problems and resolvents of making the drivers by MOSFETs are described. The experiments performed by our MOSFET drivers display that the time of leading and trailing edges of the optical switch are 5ns.
The advantage of the single pulse selectors which is driven by high voltage and large current power MOSFETs is introduced. The characteristic phenomena are discovered when the electrooptic crystal is used as a fast electooptic switch and the problems and resolvents of making the drivers by MOSFETs are described. The experiments performed by our MOSFET drivers display that the time of leading and trailing edges of the optical switch are 5ns.
1999,
11.
Abstract:
The principles and the experiment for temperature and OH concentration fields measurement by LIPF is mentioned in this paper. With a tunable KrF excimer laser, the fluorescence of OH was got in a methaneair flame at the pressure of atmosphere and the structures of the spectrum were analyzed. The instantaneous temperature in the flame was also given out by LIPF, the relative error is less than 3%. The fluorescence images of OH shows the direct images of densities and the temperature fields in quality.
The principles and the experiment for temperature and OH concentration fields measurement by LIPF is mentioned in this paper. With a tunable KrF excimer laser, the fluorescence of OH was got in a methaneair flame at the pressure of atmosphere and the structures of the spectrum were analyzed. The instantaneous temperature in the flame was also given out by LIPF, the relative error is less than 3%. The fluorescence images of OH shows the direct images of densities and the temperature fields in quality.
1999,
11.
Abstract:
In this paper, based on the analysis of advantages and disadvantages of the unstable resonator with a phase-unifying output coupler, the improving unstable resonator are designed. The numerical simulation results indicate that the improving unstable resonator overcomes disadvantages of that resonator and its far-field intensity focusing is better than the conventional resontor．
In this paper, based on the analysis of advantages and disadvantages of the unstable resonator with a phase-unifying output coupler, the improving unstable resonator are designed. The numerical simulation results indicate that the improving unstable resonator overcomes disadvantages of that resonator and its far-field intensity focusing is better than the conventional resontor．
1999,
11.
Abstract:
A special designation is reported to measure the loss together of absorption and deflection in NLO crystals in the cavity. The method has characters of high sensitivity to about 10 －4 and fast response time up to 100 nanoseconds. We consider it extensible to be applied in the studies of nondestructive and quick destructive detection of NLO crystals related to the irradiation of high peek power laser. The results of KTP、KDP、KD*P crystals in our experiment and also the comparison to others is shown.
A special designation is reported to measure the loss together of absorption and deflection in NLO crystals in the cavity. The method has characters of high sensitivity to about 10 －4 and fast response time up to 100 nanoseconds. We consider it extensible to be applied in the studies of nondestructive and quick destructive detection of NLO crystals related to the irradiation of high peek power laser. The results of KTP、KDP、KD*P crystals in our experiment and also the comparison to others is shown.
1999,
11.
Abstract:
The 3D and 2D numerical simulation of flow field for the Chemical OxygenIodine Laser (COIL) have been performed on the basis of gas and chemistry dynamical model, and the numerical results are consistent with those of the similare simulation in the references. The convergence of this simulation appears less than six orders of magnitude．
The 3D and 2D numerical simulation of flow field for the Chemical OxygenIodine Laser (COIL) have been performed on the basis of gas and chemistry dynamical model, and the numerical results are consistent with those of the similare simulation in the references. The convergence of this simulation appears less than six orders of magnitude．
1999,
11.
Abstract:
Hyperfine gain spectrum of a chemical oxygeniodine laser (COIL) is investigated experimentally. Six hyperfine lines are obtained in a COIL gain medium as well as an iodine absorption cell. Meanwhile, gain profiles and cavity temperatures are calculated.
Hyperfine gain spectrum of a chemical oxygeniodine laser (COIL) is investigated experimentally. Six hyperfine lines are obtained in a COIL gain medium as well as an iodine absorption cell. Meanwhile, gain profiles and cavity temperatures are calculated.
1999,
11.
Abstract:
Third harmonic generation of broadband Ti:sapphire laser was obtained with multicystal, this equipment can improved the efficiency and the accept band width. The efficiency curve, the temporal, and the spatial graph of the THG have been shown. The result was analysised with the broadband nonlinear equation. The accept bandwidth and the leaveoff angle were also studied．
Third harmonic generation of broadband Ti:sapphire laser was obtained with multicystal, this equipment can improved the efficiency and the accept band width. The efficiency curve, the temporal, and the spatial graph of the THG have been shown. The result was analysised with the broadband nonlinear equation. The accept bandwidth and the leaveoff angle were also studied．
1999,
11.
Abstract:
The manufacture technique of resonator mirrors of COIL with reflectivity higher than 999% and the tested results of the reflectivity have been reported in this paper.Furthermore, the experiment for laser damage of the samples manufactured by this technique has been done, the experimental results show that the resonator mirrors manufactured by our technique can fulfill the threshold requirement of COIL.
The manufacture technique of resonator mirrors of COIL with reflectivity higher than 999% and the tested results of the reflectivity have been reported in this paper.Furthermore, the experiment for laser damage of the samples manufactured by this technique has been done, the experimental results show that the resonator mirrors manufactured by our technique can fulfill the threshold requirement of COIL.
1999,
11.
Abstract:
Recently we have developed a multiple angle timeresolved system (MATRS) to detect scattering lights from laserproduced plasmas. In 1998, we have used the diagnostic systems mentioned above to investigate the scattering processes in plasma. These experiments were designed to enhance our understanding to scattering processes. 0.351μm laser light with about 70J at average intensities of (1～2)×10 14W/cm 2 were used to irradiate gold disks, CH disks and gold disks pasted CH foam. A lot of diagnostics were used to diagnosis the scattering behavior. The important result of experiments is the temporal behavior of the side scattering. The experimental results give us some information about electron temperature and density in the laserproduced plasmas.
Recently we have developed a multiple angle timeresolved system (MATRS) to detect scattering lights from laserproduced plasmas. In 1998, we have used the diagnostic systems mentioned above to investigate the scattering processes in plasma. These experiments were designed to enhance our understanding to scattering processes. 0.351μm laser light with about 70J at average intensities of (1～2)×10 14W/cm 2 were used to irradiate gold disks, CH disks and gold disks pasted CH foam. A lot of diagnostics were used to diagnosis the scattering behavior. The important result of experiments is the temporal behavior of the side scattering. The experimental results give us some information about electron temperature and density in the laserproduced plasmas.
1999,
11.
Abstract:
This paper describes the structure and princinple of a Xray picosecond framing camera. Also, the performance and critical techniques of camera are presented. 12 frame images of the laser produced plasma source are obtained with the camera．
This paper describes the structure and princinple of a Xray picosecond framing camera. Also, the performance and critical techniques of camera are presented. 12 frame images of the laser produced plasma source are obtained with the camera．
1999,
11.
Abstract:
In this paper, the Maxwell equations of Xray laser beam through stationary plasma was written as the equation in the form of timedependent Schr〖ＡＫo¨４〗edinger equation (TDSE), the generalized Huygens' integral was derived in terms of evolution operators from the viewpoint of quantum mechanics for the first time, and the analytical relationship of the electron density of plasma with the phase difference of the Xray through stationary plasma with gain and the same Xray through vacuum under the optical thin approximation (its diffraction effects are negligible)．
In this paper, the Maxwell equations of Xray laser beam through stationary plasma was written as the equation in the form of timedependent Schr〖ＡＫo¨４〗edinger equation (TDSE), the generalized Huygens' integral was derived in terms of evolution operators from the viewpoint of quantum mechanics for the first time, and the analytical relationship of the electron density of plasma with the phase difference of the Xray through stationary plasma with gain and the same Xray through vacuum under the optical thin approximation (its diffraction effects are negligible)．
1999,
11.
Abstract:
Optic thin film with high refractive index and high laser damage threshold was prepared from ZrＯCl2·8H2Ｏ with solgel process. The film was prepared with spin coating method. The structure, optical properties and laser damage threshold of the films were investigated. The influences of organic binder to the refractive index and the mechanic strength of the films were also studied. A minimum transmittance of less than 1% near 1064nm was obtained from the present ［SiＯ2/ZrＯ2］１０multilayer HR coatings, meanwhile a laser damage threshold of more than 16J/cm2 was achieved using high power laser at wavelength of 1064nm and pulse width of 2.5ns.
Optic thin film with high refractive index and high laser damage threshold was prepared from ZrＯCl2·8H2Ｏ with solgel process. The film was prepared with spin coating method. The structure, optical properties and laser damage threshold of the films were investigated. The influences of organic binder to the refractive index and the mechanic strength of the films were also studied. A minimum transmittance of less than 1% near 1064nm was obtained from the present ［SiＯ2/ZrＯ2］１０multilayer HR coatings, meanwhile a laser damage threshold of more than 16J/cm2 was achieved using high power laser at wavelength of 1064nm and pulse width of 2.5ns.
1999,
11.
Abstract:
Perdeuterated polystyrene (DPS) was used as the raw material. By emulsifying microencapsulation technique, high quality DPS hollow microspheres for inertial confinement fusion (ICF) with diameter from 150 to 450 μm, wall thickness from 2 to 15 μm were fabricated. The sphericity, concentricity and surface roughness were ≥99.5%, 95%~98% and ＜30nm respectively. This paper describes the fabrication process, and the main factors that influence the quality of the microspheres were studied also．
Perdeuterated polystyrene (DPS) was used as the raw material. By emulsifying microencapsulation technique, high quality DPS hollow microspheres for inertial confinement fusion (ICF) with diameter from 150 to 450 μm, wall thickness from 2 to 15 μm were fabricated. The sphericity, concentricity and surface roughness were ≥99.5%, 95%~98% and ＜30nm respectively. This paper describes the fabrication process, and the main factors that influence the quality of the microspheres were studied also．
1999,
11.
Abstract:
Physical equations, numerical methods and slide grids of laser ablative hydrodynamic instability in the code EUL3D are introduced. Simulation results of the EUL3D code are good agreements with those of the Takabe formula, the FAST2D code and the LASNEX code, and the experimental result of laser ablative RayleighTayler instability in Osaka University. The lower Atwood number stabilization due to the preheat is observed in simulation and a new growth rate formula is obtained. It includes the density gradient, the lower Atwood number and the ablative convection stabilizations, so it agrees well with all of 2D simulations．
Physical equations, numerical methods and slide grids of laser ablative hydrodynamic instability in the code EUL3D are introduced. Simulation results of the EUL3D code are good agreements with those of the Takabe formula, the FAST2D code and the LASNEX code, and the experimental result of laser ablative RayleighTayler instability in Osaka University. The lower Atwood number stabilization due to the preheat is observed in simulation and a new growth rate formula is obtained. It includes the density gradient, the lower Atwood number and the ablative convection stabilizations, so it agrees well with all of 2D simulations．
