Thermal emittance measurements for electron beams produced from bulk and superlattice negative electron affinity photocathodes
Thermal emittance measurements for electron beams produced from bulk and superlattice negative electron affinity photocathodes
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DOI：
10.1063/1.2756376
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发表时间：
2007-07-15
影响因子：
3.2
通讯作者：
Takeda, Yoshikazu
中科院分区：
文献类型：
--
作者：
Yamamoto, Naoto;Yamamoto, Masahiro;Takeda, Yoshikazu
下一代加速器需要极低发射度的电子束。具有负电子亲和势（NEA）表面的GaAs半导体光电阴极具有产生这种低发射度电子束的固有优势，理想情况下热发射度可低至0.1 π mm mrad。测量了两种不同的NEA光电阴极：体GaAs光电阴极和GaAs-GaAsP超晶格应变光电阴极的光电子热发射率。对于1.0 mm的射束半径，归一化均方根发射度分别低至0.20-0.29 +/- 0.02和0.15 +/- 0.02 π mm mrad。这些结果的比较表明，超晶格光阴极的光子激发能量高于带隙能量的热发射率最小化。
Extremely low emittance electron beams are required for next generation accelerators. GaAs semiconductor photocathodes with negative electron affinity (NEA) surfaces have an intrinsic advantage for generating such low emittance beams and the thermal emittance as low as 0.1 pi mm mrad is expected in ideal case. The thermal emittance of photoelectrons was measured for two different NEA photocathodes: a bulk-GaAs photocathode and a GaAs-GaAsP superlattice strained photocathode. The normalized root-mean-sqare emittances for the beam radius of 1.0 mm were as low as 0.20-0.29 +/- 0.02 and 0.15 +/- 0.02 pi mm mrad, respectively. A comparison of these results shows that the superlattice photocathode minimizes the thermal emittance for photon excitation energies higher than the band gap energy.