Development of Polarized Electron Source for Linear Colliders by Using Superlattice Photocathhode

利用超晶格光电阴极研制直线对撞机偏振电子源

• 批准号: 04640315
• 负责人: OMORI Tsunehiko
• 金额: $ 1.6万
• 依托单位: National Laboratory for High Energy Physics (KEK)
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1992
• 资助国家: 日本
• 起止时间: 1992 至 1993
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-04640315/
• 关键词: Linear Collider; JLC; Superlattice; Polarized Electron; Photocathode; Modulation Doping; Charge Limit; ソニアコライダー

We achieved 715 polarization of photoemission from the ALGA-As-GaAs superlattice in early 1991. The study described below has been performed to proceed the fruits further aimed to apply the superlattice in future linear colliders (JLC for example).We have studied the spin depolarization during the diffusion of electrons in the conduction band. The superlattice is p-doped to achieve negative-electron-affinity, which is necessary to use the superlattice for a photocathode. We applied lower acceptor concentration in most part of a superlattice, on the other hand normal(5x10^<18>/cm^3), or even higher, concentration near the surface. We have found this type of modulation doping improves both polarization and quantum efficiency of a photocathode.We have studied that how polarization depends on the total thickness of the superlattice. The extrapolation to zero thickness gave a polarization of -75%. We tested sample which has various surface conditions. Non of them showed significant improvement of the polarization. We have concluded there was no source of large depolarization near the surface. Therefore the polarization of electrons exited in the conduction band was -75%.We have tested large charge-extraction from a superlattice. This test was performed at SLAC as a part of the Japan-SLAC collaboration. The result was successful ; 2.3x10^<11>electrons were extracted in 2.5nsec. No charge Limit of the photochatode material was observed. The resultant number of electrons was limited by Space Charge Limit of the gun. This result is very encouraging becaouse the charge Limit phenomenon is supposed to be the most serious problem of a photocathode gun in a future linear collider.

我们在1991年初从ALGA-As-GaAs超晶格中获得了715偏振的光电发射。为了进一步将超晶格应用于未来的直线对撞机（例如JLC），我们进行了以下研究。我们研究了电子在导带扩散过程中的自旋去极化。超晶格是p掺杂的以实现负电子亲和势，这对于将超晶格用于光电阴极是必要的。我们在超晶格的大部分区域采用较低的受主浓度，另一方面，在表面附近采用正常浓度（5 × 10 ^<18>/cm ^3），甚至更高的浓度。我们发现这种调制掺杂可以同时提高光电阴极的极化率和量子效率，并研究了极化率与超晶格总厚度的关系。外推到零厚度给出了-75%的极化。我们测试了具有各种表面条件的样品。它们中没有一个显示出极化的显著改善。我们已经得出结论，在表面附近没有大的去极化源。因此，在导带中激发的电子的极化是-75%。我们已经测试了从超晶格中的大的电荷提取。作为日本-SLAC合作的一部分，在SLAC进行了该测试。结果是成功的;<11>在2.5纳秒内提取了2.3x10^电子。没有观察到光敏材料的电荷极限。所产生的电子数受到电子枪的空间电荷极限的限制。这一结果是令人鼓舞的，因为电荷极限现象被认为是未来直线对撞机中光阴极电子枪最严重的问题。

项目成果

Y.Kurihara: "Mott Analyzer to Measure Electron Spin Polarization(in Japanese9" Bussei Ken Dayori. 33-3. 42-43 (1993)

Y.Kurihara：“用于测量电子自旋极化的 Mott 分析仪（日语 9”） Bussei Ken Dayori. 33-3. 42-43 (1993)

Y.Kurihara 他10名: "Depolarization of Photoemission at the Surface and Interior of AlGaAs-GaAs Superlattice" Nuclear Instruments and Methods in Physics Reseach. A131. 393-397 (1992)

Y. Kurihara 和其他 10 人：“AlGaAs-GaAs 超晶格表面和内部的光电子去极化”，核仪器和物理研究方法 A131 (1992)。

T.Omori etal.: "Development of Polarized Electron Source Using AlGaAs-GaAs Superlattice" Int.J.Mod.Phys.A(Proc.Suppl.)(Proc.15th Int.Conf.High Energy Accelerators, 1993). 2A. 157-159 (1993)

T.Omori 等人：“使用 AlGaAs-GaAs 超晶格开发极化电子源”Int.J.Mod.Phys.A（Proc.Suppl.）（Proc.15th Int.Conf.High Energy Accelerators，1993）。

栗原良将: "モット散乱を用いたスピン偏極度測定装置" 物性研だより. 33-3. 42-43 (1993)

Yoshimasa Kurihara：“使用莫特散射的自旋偏振测量装置”来自固体物理研究所的通讯 33-3 (1993)。

T.Omori: "Polarized Electron Source by Superlattice Photocathode(in Japanese)" Bussei Ken Dayori. 33-3. 19-22 (1993)

T.Omori：“超晶格光电阴极的偏振电子源（日语）”Bussei Ken Dayori。