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

在没有实际辐射源的亚毫米波区域，研究一种可能的短毫米波相干辐射源。自由选择激光器（FELs）可以是具有频率可调特性的紧凑相干辐射源。在本研究中，我们对两种类型的FELs进行了实验研究。一个是史密斯-珀塞尔自由电子束流，另一个是微摆动自由电子束流。Smith-Purcel FELs利用了存在于导电光栅表面附近的慢波与倏逝波的相互作用。选举光束必须非常靠近金属光栅表面传播。微摆动磁场利用电磁波与微摆动磁场中的波束模式之间的快波相互作用。选举光束在摆动磁场中传播。我们构造了一个功率高达1MV的紧凑型区型静电加速器。选择注入是由具有KrF准分子激光器的光电阴极进行的。电子束参数约为能量7OOKeV，电流1A，脉宽3Onsec。设计了100GHz和300GHz Smith-Purcel自由电子激光器的金属光栅。然而，我们根本没有观测到辐射信号。造成这一结果的原因可能是在金属光栅表面附近传播的电子电流不足以引起史密斯-珀塞尔自由电子激光器的振荡。针对微摆振自由电子激光器，设计了周期为8mm、间隙为3mm的永磁体微摆振。在微摆动器中，我们安装了一个带布拉格反射器的波导谐振器。选举光束被小心地控制以通过波导谐振器传播。目前，我们观测到一个103ghz的辐射信号，该信号向设计频率倾斜。我们继续研究这种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.