One kind of instantaneous electron beam emittance measurement system based on the optical transition radiation principle and double imaging optical method has been set up. It is mainly adopted in the test for the inte...One kind of instantaneous electron beam emittance measurement system based on the optical transition radiation principle and double imaging optical method has been set up. It is mainly adopted in the test for the intense electron-beam produced by a linear induction accelerator. The system features two characteristics. The first one concerns the system synchronization signal triggered by the following edge of the main output waveform from a Blumlein switch. The synchronous precision of about 1 ns between the electron beam and the image capture time can be reached in this way so that the electron beam emittance at the desired time point can be obtained. The other advantage of the system is the ability to obtain the beam spot and beam divergence in one measurement so that the calculated result is the true beam emittance at that time, which can explain the electron beam condition. It provides to be a powerful beam diagnostic method for a 2.5 kA, 18.5 MeV, 90 ns （FWHM） electron beam pulse produced by Dragon I. The ability of the instantaneous measurement is about 3 ns and it can measure the beam emittance at any time point during one beam pulse. A series of beam emittances have been obtained for Dragon I. The typical beam spot is 9.0 mm （FWHM） in diameter and the corresponding beam divergence is about 10.5 mrad.展开更多
A measurement system was developed to measure the electron beam spectrum of the Beijing free-electron laser based on the optical transition radiation (OTR). This paper describes the system, which consists of a 32-chan...A measurement system was developed to measure the electron beam spectrum of the Beijing free-electron laser based on the optical transition radiation (OTR). This paper describes the system, which consists of a 32-channel high resolution of 0.02% OTR detector, especially the spectrometer. The OTR an-gular-distribution pattern at the focal plane has two apexes, but the two apexes are smoothed out due to the electron beam energy distribution. The energy spectrum can be measured if the magnet energy resolution is higher than 0.7% to distinguish the electron beam energy distribution.展开更多
Laser plasma accelerators （LPAs） have made great progress, achieving electron beam with energy up to 1 GeV from a centimeter scale capillary plasma waveguide. Here, we report the measurement of optical transition ra...Laser plasma accelerators （LPAs） have made great progress, achieving electron beam with energy up to 1 GeV from a centimeter scale capillary plasma waveguide. Here, we report the measurement of optical transition radiation （OTR） from the capillary-based LPA electron beams. Transition radiation images, produced by electrons passing through two separate foils （located at 2.3 m and 3.8 m away from the exit of the LPA） were recorded with a high resolution imaging system, respectively. Two magnetic quadrupole lenses were placed right after the capillary to focus and collimate the electron beams. Significant localized spikes appeared in the OTR images when the electron beam was focused by the magnetic quadrupole lenses, indicating the coherence of the radiation and the existence of ultrashort longitudinal structures inside the electron beam.展开更多
Atmospheric radiative fluxes are evaluated for the line-by-line model of spectral lines in considering the atmosphere as a weakly nonuniform plane layer and altitude profiles of its parameters are taken from the model...Atmospheric radiative fluxes are evaluated for the line-by-line model of spectral lines in considering the atmosphere as a weakly nonuniform plane layer and altitude profiles of its parameters are taken from the model of standard atmosphere.Concepts of molecular spectroscopy are combined with the local thermodynamic equilibrium for greenhouse gases and with information from HITRAN data base for parameters of radiative transitions.In addition,the energetic balance of the Earth allows one to determine the radiative flux from clouds.As a result,the algorithm is worked out for evaluation of the atmospheric radiative flux toward the Earth depending on its composition.We below concentrate on the change of atmospheric radiative fluxes as a result of doubling of the concentration of CO2 molecules.It is shown that the change of the global temperature in this case according to the above algorithm in 5-6 times exceeds that followed from climatological models which are based on old spectral data,rather than those from HITRAN data base.These codes ignore overlapping of spectral lines of atmospheric radiators.展开更多
基金Supported by National Natural Science Foundation of China(10675104)
文摘One kind of instantaneous electron beam emittance measurement system based on the optical transition radiation principle and double imaging optical method has been set up. It is mainly adopted in the test for the intense electron-beam produced by a linear induction accelerator. The system features two characteristics. The first one concerns the system synchronization signal triggered by the following edge of the main output waveform from a Blumlein switch. The synchronous precision of about 1 ns between the electron beam and the image capture time can be reached in this way so that the electron beam emittance at the desired time point can be obtained. The other advantage of the system is the ability to obtain the beam spot and beam divergence in one measurement so that the calculated result is the true beam emittance at that time, which can explain the electron beam condition. It provides to be a powerful beam diagnostic method for a 2.5 kA, 18.5 MeV, 90 ns （FWHM） electron beam pulse produced by Dragon I. The ability of the instantaneous measurement is about 3 ns and it can measure the beam emittance at any time point during one beam pulse. A series of beam emittances have been obtained for Dragon I. The typical beam spot is 9.0 mm （FWHM） in diameter and the corresponding beam divergence is about 10.5 mrad.
基金Supported by the National Natural Science Foundation of China (No. 19875029)
文摘A measurement system was developed to measure the electron beam spectrum of the Beijing free-electron laser based on the optical transition radiation (OTR). This paper describes the system, which consists of a 32-channel high resolution of 0.02% OTR detector, especially the spectrometer. The OTR an-gular-distribution pattern at the focal plane has two apexes, but the two apexes are smoothed out due to the electron beam energy distribution. The energy spectrum can be measured if the magnet energy resolution is higher than 0.7% to distinguish the electron beam energy distribution.
文摘Laser plasma accelerators （LPAs） have made great progress, achieving electron beam with energy up to 1 GeV from a centimeter scale capillary plasma waveguide. Here, we report the measurement of optical transition radiation （OTR） from the capillary-based LPA electron beams. Transition radiation images, produced by electrons passing through two separate foils （located at 2.3 m and 3.8 m away from the exit of the LPA） were recorded with a high resolution imaging system, respectively. Two magnetic quadrupole lenses were placed right after the capillary to focus and collimate the electron beams. Significant localized spikes appeared in the OTR images when the electron beam was focused by the magnetic quadrupole lenses, indicating the coherence of the radiation and the existence of ultrashort longitudinal structures inside the electron beam.
文摘Atmospheric radiative fluxes are evaluated for the line-by-line model of spectral lines in considering the atmosphere as a weakly nonuniform plane layer and altitude profiles of its parameters are taken from the model of standard atmosphere.Concepts of molecular spectroscopy are combined with the local thermodynamic equilibrium for greenhouse gases and with information from HITRAN data base for parameters of radiative transitions.In addition,the energetic balance of the Earth allows one to determine the radiative flux from clouds.As a result,the algorithm is worked out for evaluation of the atmospheric radiative flux toward the Earth depending on its composition.We below concentrate on the change of atmospheric radiative fluxes as a result of doubling of the concentration of CO2 molecules.It is shown that the change of the global temperature in this case according to the above algorithm in 5-6 times exceeds that followed from climatological models which are based on old spectral data,rather than those from HITRAN data base.These codes ignore overlapping of spectral lines of atmospheric radiators.
