Palacios-Serrano G, Hannon F, Hernandez-Garcia C, Poelker M, Baumgart H
Department of Electrical Engineering, Old Dominion University, Norfolk, Virginia 23529, USA.
Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA.
Rev Sci Instrum. 2018 Oct;89(10):104703. doi: 10.1063/1.5048700.
Nuclear physics experiments performed at the Continuous Electron Beam Accelerator Facility (CEBAF) at the Jefferson Lab require a DC high voltage photogun to generate polarized electron beams from GaAs photocathodes. The photogun uses a tapered ceramic insulator that extends into the vacuum chamber and mechanically holds the cathode electrode. Increasing the operating voltage from nominal -130 kV to -200 kV will provide lower beam emittance, better transmission through injector apertures, and improved photocathode lifetime. This desire to increase the photogun operating voltage led to the design of a triple-point-junction shield electrode which minimizes the electric field at the delicate insulator-metal-vacuum interface and linearizes the potential across the insulator, thus reducing the risk of arcing along the ceramic insulator. This work describes the results obtained using COMSOL® electrostatic-field simulation software and presents the high voltage conditioning results of the upgraded -200 kV CEBAF photogun.
在杰斐逊实验室的连续电子束加速器装置（CEBAF）上进行的核物理实验需要一台直流高压光电子枪，以便从砷化镓光电阴极产生极化电子束。该光电子枪使用一个延伸到真空室并机械固定阴极电极的锥形陶瓷绝缘子。将工作电压从标称的-130 kV提高到-200 kV将提供更低的束流发射度、更好的通过注入器孔径的传输以及更长的光电阴极寿命。这种提高光电子枪工作电压的需求导致了一种三点结屏蔽电极的设计，该电极可使脆弱的绝缘体 - 金属 - 真空界面处的电场最小化，并使绝缘子两端的电位线性化，从而降低沿陶瓷绝缘子产生电弧的风险。这项工作描述了使用COMSOL®静电场模拟软件获得的结果，并展示了升级后的-200 kV CEBAF光电子枪的高压调节结果。
