Clayburn N B, Brunkow E, Burtwistle S J, Rutherford G H, Gay T J
Jorgensen Hall, University of Nebraska, Lincoln, Nebraska 68588-0299, USA.
Department of Physics, Illinois State University, Normal, Illinois 61790-4650, USA.
Rev Sci Instrum. 2016 May;87(5):053302. doi: 10.1063/1.4946995.
A small, novel, cylindrically symmetric Mott electron polarimeter is described. The effective Sherman function, Seff, or analyzing power, for 20 kV Au target bias with a 1.3 keV energy loss window is 0.16 ± 0.01, where uncertainty in the measurement is due primarily to uncertainty in the incident electron polarization. For an energy loss window of 0.5 keV, Seff reaches its maximum value of 0.24 ± 0.02. The device's maximum efficiency, I/Io, defined as the detected count rate divided by the incident particle rate, is 3.7 ± 0.2 × 10(-4) at 20 keV. The figure-of-merit of the device, η, is defined as Seff (2)IIo and equals 9.0 ± 1.6 × 10(-6). Potential sources of false asymmetries due to detector electronic asymmetry and beam misalignment have been investigated. The new polarimeter's performance is compared to published results for similar compact retarding-field Mott polarimeters, and it is concluded that this device has a relatively large Seff and low efficiency. SIMION(®) electron trajectory simulations and Sherman function calculations are presented to explain the differences in performance between this device and previous designs. This design has an Seff that is insensitive to spatial beam fluctuations and, for an energy loss window >0.5 keV, negligible background due to spurious ion and X-ray production at the target.
描述了一种小型、新颖的圆柱对称莫特电子偏振仪。对于20 kV金靶偏压且能量损失窗口为1.3 keV的情况，有效谢尔曼函数Seff或分析能力为0.16±0.01，测量中的不确定性主要源于入射电子极化的不确定性。对于0.5 keV的能量损失窗口，Seff达到其最大值0.24±0.02。该装置的最大效率I/Io定义为检测到的计数率除以入射粒子率，在20 keV时为3.7±0.2×10(-4)。该装置的品质因数η定义为Seff(2)IIo，等于9.0±1.6×10(-6)。研究了由于探测器电子不对称和束流未对准导致的虚假不对称的潜在来源。将新型偏振仪的性能与已发表的类似紧凑型减速场莫特偏振仪的结果进行了比较，得出该装置具有相对较大的Seff和较低效率的结论。给出了SIMION(®)电子轨迹模拟和谢尔曼函数计算结果，以解释该装置与先前设计在性能上的差异。这种设计的Seff对空间束流波动不敏感，并且对于能量损失窗口>0.5 keV的情况，由于靶上产生的杂散离子和X射线导致的背景可忽略不计。
