Production of Low Energy Gamma-Ray by Inverse Compton Scattering using a Far Infrared Laser

1.低能量γ激光产生技术利用中空的丙烯酸光波导将红外激光传输到储存环隧道光束线前端的激光入射室，空气露点温度为-40℃。它的传输距离约为20m，传输效率达到80%。利用热释电传感器研制了束流轮廓监测器，并安装在离暗室上游2米处。利用该监测器对激光光轴进行了调谐，实现了点对电子束的相互作用。通过考虑前端管道中多种孔径限制的衍射效应的计算，估算出γ光的产生率为Nγ=1.1×10~(4)光子/秒，输出功率为118.8μm~2的2W FIR激光器。在9p(38)激光线上实现了高功率光泵浦的CO_2激光器的输出功率为234.5W，用于泵浦118.8μ毫米波的CH3OH。FIR激光器的最大输出功率约为1.6W，功率变化的±1%为…更多的实现了24小时的长期稳定。为了产生20 MeV的γ射线，研制了48μm和57μm激光的短波FIR激光器和硅光学材料。3.产生的γ射线的测量为了采取探测系统堆积和减少本底的措施，在10 mm厚的铅盒中安装了LYSO闪烁体。探测器前安装了吸收体和准直器系统。用^&lt；88&gt；Y的放射源进行了能量刻度，证实了储存的电子在逆康普顿散射过程中没有丢失。根据测量结果，我们估计每台2W FIR激光器的γ光产生速率为6×10~(-3)光子/秒。4.未来计划为了产生高强度的γ光，一项先进的计划正在进行中，新的光束线具有16米长的相互作用区。激光光束通过波导传输到相互作用区附近，以恢复由于激光的大发散而造成的有效截面的减小。完成了镜室的制造和安装，以及激光洁净室和波导系统的建造。在这条光束线中，γ射线的产生率预计将超过10^5光子/秒。较少

1.Technology of low energy γ-ray productionFIR laser was transported to the laser incident chamber on the beamline front-end in the storage ring tunnel by hollow acrylic waveguides into which dry air of -40℃ dew-point temperature was flow. Its distance is about 20m long, and 80% transmission efficiency was achieved. Beam profile monitor using a pyro-electric sensor was developed and installed at 2m-upstream from the chamber. By using this monitor, laser optical axis was tuned for the interaction point to electron beam. By the calculation considering the diffraction effect by many aperture limits in the duct of front-end, a production rate of γ-ray was estimated to be Nγ=1.1×10^4 photons/sec per 2W FIR laser of 118.8μm.2.Development of high-power optically-pumped FIR laser234.5W-output power of the pumping CO_2 laser was achieved at 9P(38) lasing line, which was used for pumping CH_3OH for 118.8μm lasing. Maximum output power of FIR laser was about 1.6W, and ±1 % of power variation was … More achieved for a long-term stability of 24 hours. To produce 20MeV range γ-ray, a short wavelength FIR laser and optical material of silicon for 48μm- and 57μm-laser were developed.3.Measurement of produced γ-rayTo take measures of pileup of detection system and to reduce a background, LYSO scintillator was installed in 10mm-thickness Pb-box. Absorbers and collimator system were installed in front of the detector. Energy calibration was done by using radioactivity source of ^<88>Y. It was confirmed that stored electrons were not lost during the inverse Compton scattering. From measurement result, we estimated γ-ray production rate at 6×10^3 photons/sec per a 2W FIR laser.4.Future planTo produce high intense γ-ray, an advanced plan is in progress at the new beamline which has a 16m-long interaction region. Laser beam will be transported to near the interaction region by waveguides to recover a reduction of effective cross-section due to a large divergence of laser. Manufacture and installation of the mirror chamber, and construction of the laser clean room and the waveguide system were completed. In this beamline γ-ray production rate will be expected more than 10^5 photons/sec. Less