Plasma accelerator development using CO2 laser beat-wave.

我们尝试用CO2激光器获得300 ps上升、350 J输出的双线振荡激光，用于拍波激发等离子体波。利用双线激光在氢等离子体中激发出相对论等离子体波。这个项目的目的是通过这种等离子体波来加速注入的电子。(1)我们试图激发等离子体波的双线组合的10.6和9.6妈妈和10.6和10.3妈妈。前者的共振密度为1.1 × 10 ^<17>/cm ^3，后者为9 × 10 ^<15>/cm ^3。我们成功地在激光持续时间内通过隧道电离产生等离子体。(2)我们尝试了YAG激光汤姆逊散射测量等离子体波，这使我们能够获得时间分辨的等离子体波振幅。来自YAG振荡器的二次谐波光垂直于CO2激光器轴注入。侧面散射的YAG光通过光谱分析仪到条纹相机进行分析。对于单线激光注入，我们通过后向拉曼散射观察到等离子体波。激光上升后仅在300 ps内激发出等离子体波，其振幅达到2%的密度扰动，可使等离子体电子加速20 keV以上。(3)为了测量加速电子的能量，我们研制了一台磁场可变的磁分析仪，它可以检测0 ~ 30 MeV的电子。

We tried to obtain double line oscillation laser light from CO 2 laser of 300 ps rise and 350 J output for beatwave excitation of plasma wave. By using the double line laser we excited relativistic plasma wave in gas-puffed hydrogen plasmas. The purpose of this project is to accelerate injected electrons by this plasma wave.(1) We tried to excite the plasma wave both for double line combination of 10.6 and 9.6 mum and of 10.6 and 10.3 mum. The resonant density is 1.1x10^<17>/cm^3 for the former combination and 9x10^<15>/cm^3 for the latter. We succeeded to produce plasmas in the laser duration through the tunneling ionization.(2) We tried YAG laser Thomson scattering measurement of plasma waves, which enables us to obtain the time-resolved plasma wave amplitudes. A 2nd harmonic light from the YAG oscillator is injected perpendicularly to the CO2 laser axis. The side scattered YAG light are analyzed through spectrum analyzer to streak camera. For single line laser injection, we observed the plasma wave through backward Raman scattering. The plasma wave is excited only in 300ps just after the laser rise and its amplitude attains to 2% density perturbation, which can accelerate the plasma electrons more than 20 keV.We are now measuring the plasma wave excitation by double line injection CO2 laser..(3) To measure the accelerated electron energy, we developed a field variable magnetic analyzer, which can detect electron from 0 to 30 MeV.We try now to compare the electron energy spectrum with the plasma wave amplitude and its time dependence.