Experimental Study on Smith-Purcel and Micro Wiggler Free Election Lasers

在没有实际辐射源的情况下，我们研究了一种可能的亚毫米波短毫米波相干辐射源。自由电子激光器(FEL)是一种具有频率可调特性的紧凑型相干辐射源。一种是Smith-Purcell自由电子激光器，另一种是微摆荡器FEL。Smith-Purcel FEL利用了存在于导电光栅表面附近的慢波与逝去波的相互作用。电子束必须在非常接近金属栅面的地方传播。微摇摆器自由电子激光利用了微摇摆器磁场中电磁波与束流模式之间的快波相互作用。电子束在摇摆器磁场中传输，我们构造了一台高达1 MV的紧凑型圆盘型静电加速器，电子注入由KrF准分子激光器的光阴极进行。电子束参数约为70keV能量，1a电流，3秒脉冲宽度。我们设计了用于100 GHz和300 GHz Smith-Purcel FEL的金属栅，但我们完全没有观察到辐射信号。其原因可能是在金属栅面附近传输的电子电流不足以产生Smith-Purcell自由电子激光振荡。对于微摇摆器自由电子激光器，我们设计了周期为8 mm、间隙为3 mm的永磁体微摇摆器。在微摇摆器中，我们安装了一个带有布拉格反射器的光波导谐振腔。电子束被小心地控制以通过波导谐振腔传播。目前，我们观测到了103 GHz的辐射信号，它将池塘的频率限制在设计频率上。我们继续研究这一辐射信号与腔性质的关系。

We study on a possible coherent radiation source in short millimeter wave on submillimeter wave region, where there are not practical radiation sources. Free-Election Lasers (FELs) can be compact coherent radiation sources with frequency-tunable characteristics.In this study, we experimentally study on two types of FELs. One is a Smith-Purcell FEL, and the other is a micro-wiggler FEL.Smith-Purcel FELs utilize the slow- wave interaction with evanescent wave, which exists near the surface of a conductive grating. The election beam has to propagate very close the metal grating surface. Micro-wiggler FELs utilize the fast-wave interaction between an electro-magnetic wave and a beam mode in a micro-wiggler magnetic field. The election beam propagates in the wiggler magnetic field.We construct a compact disctron-type electrostatic accelerator up to 1MV.The election injection is performed by a photo-cathode with a KrF excimer laser. The electron beam parameters are about 7OOKeV of energy, 1A of current, 3Onsec of pulse width.We design the metal gratings for 100GHz and 300GHz Smith-Purcel FEL.However, we have not observed radiation signals at all. The reason of this result may be that the electron current which propagates near the metal grating surface is not enough for Smith-Purcell FEL oscillation.For the micro-wiggler FEL, we design the micro-wiggler with permanent magnets with 8mm period and 3mm gap. In the micro-wiggler we install a wave guide resonator with Bragg reflectors. The election beam is carefully controlled to propagate through the wave-guide resonator. At present, we observe a radiation signal at 103 GHz, which cones ponds to the design frequency. We keep the investigation this radiation signal in relation to the cavity property.