High brightness and high polarization electron source using transmission photocathode with GaAs-GaAsP superlattice layers
High brightness and high polarization electron source using transmission photocathode with GaAs-GaAsP superlattice layers
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DOI：
10.1063/1.2887930
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发表时间：
2008-03
影响因子：
3.2
通讯作者：
N. Yamamoto;T. Nakanishi;A. Mano;Y. Nakagawa;S. Okumi;M. Yamamoto;T. Konomi;X. Jin;T. Ujihara;Y. Takeda;T. Ohshima;T. Saka;T. Kato;H. Horinaka;T. Yasue;T. Koshikawa;M. Kuwahara
中科院分区：
文献类型：
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作者：
N. Yamamoto;T. Nakanishi;A. Mano;Y. Nakagawa;S. Okumi;M. Yamamoto;T. Konomi;X. Jin;T. Ujihara;Y. Takeda;T. Ohshima;T. Saka;T. Kato;H. Horinaka;T. Yasue;T. Koshikawa;M. Kuwahara
为了产生高亮度、高自旋极化的电子束，GaAs极化电子源的光阴极必须具有点状发射机制。为此，必须使光阴极上的激光光斑尺寸最小化，这通过将注入激光的方向从光阴极的前侧改变到后侧来实现。基于这一概念，20 kV电子枪的透射光阴极包括一个GaAs-GaAsP超晶格层的活性层。该系统在760- 810 nm波长范围内产生的光斑直径为1.3μm。极化电子束的亮度为<$2.0 × 107 Acm −2sr−1，相当于降低了的亮度<$1.0 × 107 Am −2sr−1V−1。到目前为止，达到了77%的峰值偏振。在3μA的引出电流下，观察到的电荷密度寿命为1.8× 108 Ccm −2。
In order to produce a high brightness and high spin polarization electron beam, a pointlike emission mechanism is required for the photocathode of a GaAs polarized electron source. For this purpose, the laser spot size on the photocathode must be minimized, which is realized by changing the direction of the injection laser light from the front side to the back side of the photocathode. Based on this concept, a 20kV gun was constructed with a transmission photocathode including an active layer of a GaAs–GaAsP superlattice layer. This system produces a laser spot diameter as small as 1.3μm for 760–810nm laser wavelength. The brightness of the polarized electron beam was ∼2.0×107Acm−2sr−1, which corresponds to a reduced brightness of ∼1.0×107Am−2sr−1V−1. The peak polarization of 77% was achieved up to now. A charge density lifetime of 1.8×108Ccm−2 was observed for an extracted current of 3μA.