Reduction of transverse emittance in electron injectors caused by spacecharge effects
Reduction of transverse emittance in electron injectors caused by spacecharge effects
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空间电荷效应导致电子注入器横向发射率降低
DOI：
10.1016/j.nima.2014.11.068
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发表时间：
2014
期刊：
影响因子：
--
通讯作者：
K. Masuda and M. Yamamoto
中科院分区：
文献类型：
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作者：
A. Mizuno;K. Masuda and M. Yamamoto
我们报道了电子注入器中的空间电荷效应可以降低横向发射度。对理想直流加速连续光束发射度的降低进行了数值计算，并对降低的机理进行了解析讨论。阴极的束边效应和像电荷效应在r-r '相空间中产生特殊的非线性，本文对此进行了讨论，它们有助于降低阴极后的发射度。我们还展示了实际电子注入器的发射度降低的例子，如连续光束的SCSS热离子枪，以及脉冲光束的SPring-8射频光注入器和bnl型射频光注入器。对于脉冲光束，射频腔引起的聚焦效应也有助于降低发射度。这些减少只在束流电荷较低时出现。
We report that transverse emittance can be reduced by the space charge effects in electron injectors. The reduction of emittance in an ideal DC-accelerated continuous beam is numerically calculated and the mechanisms of the reduction are analytically discussed. Beam edge and image charge effects at a cathode produce a particular nonlinearity in r–r′ phase space, which is discussed in the paper, and they contribute to reducing the emittance immediately after the cathode. We also show examples of reduced emittance for practical electron injectors such as that in the SCSS thermionic gun with a continuous beam, and those in the SPring-8 rf photoinjector and the BNL-type rf photoinjector with pulsed beams. For pulsed beams, the focusing effects caused by an rf cavity also contribute to reducing the emittance. These reductions only appear when the beam charge is low.