High-voltage testing of a 500-kV dc photocathode electron gun

Nagai, Ryoji; Hajima, Ryoichi; Nishimori, N.; Muto, T.; Yamamoto, Masahiro; Honda, Y.; Miyajima, Tsukasa; Iijima, H.; Kuriki, M.; Kuwahara, Makoto; Okumi, Shoji; Nakanishi, Toru

doi:10.1063/1.3354980

Cited by 28 publications

(15 citation statements)

References 20 publications

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“…An inverted gun design [16] reduces the amount of metal biased at high voltage, and if field emission occurs, the electrons are less likely to strike the insulator due to the orientation of the electrostatic field lines. Segmented insulators [9] successfully shield the insulator from field emission and a recent demonstration indicates successful operation at 500 kV [17]. Field emission coatings [18] once seemed promising but unfortunately, serve to trap gas which is liberated during high voltage processing.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of niobium as candidate electrode material for dc high voltage photoelectron guns

BastaniNejad

Mohamed

Elmustafa

et al. 2012

Phys. Rev. ST Accel. Beams

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The field emission characteristics of niobium electrodes were compared to those of stainless steel electrodes using a DC high voltage field emission test apparatus. A total of eight electrodes were evaluated: two 304 stainless steel electrodes polished to mirrorlike finish with diamond grit and six niobium electrodes (two single-crystal, two large-grain, and two fine-grain) that were chemically polished using a buffered-chemical acid solution. Upon the first application of high voltage, the best large-grain and single-crystal niobium electrodes performed better than the best stainless steel electrodes, exhibiting less field emission at comparable voltage and field strength. In all cases, field emission from electrodes (stainless steel and/or niobium) could be significantly reduced and sometimes completely eliminated, by introducing krypton gas into the vacuum chamber while the electrode was biased at high voltage. Of all the electrodes tested, a large-grain niobium electrode performed the best, exhibiting no measurable field emission (< 10 pA) at 225 kV with 20 mm cathode/anode gap, corresponding to a field strength of 18:7 MV=m.

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Section: Introductionmentioning

confidence: 99%

Evaluation of niobium as candidate electrode material for dc high voltage photoelectron guns

BastaniNejad

Mohamed

Elmustafa

et al. 2012

Phys. Rev. ST Accel. Beams

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“…One is discharge on the insulator's ceramic surface caused by field emission generated from a central stem electrode. We have employed a segmented insulator with rings to protect the insulator from the field emission [10]. Although emission from the reverse side of the rings may still impact the insulator directly, its maximum surface electric field is less than one-third that of the stem electrode.…”

Section: Introductionmentioning

confidence: 99%

“…We could ramp up the voltage to 550 kV and demonstrate the application of 510 kV for 8 h without any discharge. The details of the HV conditioning without the cathode electrode are described elsewhere [10].…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation of an optimum configuration for a high-voltage photoemission gun for operation at≥500 kV

Nishimori

Nagai

Matsuba

et al. 2014

Phys. Rev. ST Accel. Beams

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We demonstrated the generation of a 500-keV electron beam from a high dc voltage photoemission gun for an energy recovery linac light source [N. Nishimori et al., Appl. Phys. Lett. 102, 234103 (2013)]. This demonstration was achieved by addressing two discharge problems that lead to vacuum breakdown in the dc gun. One is field emission generated from a central stem electrode. We employed a segmented insulator to protect the ceramic insulator surface from the field emission. The other is microdischarge at an anode electrode or a vacuum chamber, which is triggered by microparticle transfer or field emission from a cathode electrode. An experimental investigation revealed that a larger acceleration gap, optimized mainly to reduce the surface electric field of the anode electrode, suppresses the microdischarge events that accompany gas desorption. It was also found that nonevaporable getter pumps placed around the acceleration gap greatly help to suppress those microdischarge events. The applied voltage as a function of the total gas desorption is shown to be a good measure for finding the optimum dc gun configuration.

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“…Another group [13] recently built such a device and successfully tested it to 550kV. Our design is shown in Fig.…”

Section: Insulatorsmentioning

confidence: 96%

Design considerations for a high voltage DC photoemission electron gun at Cornell University

Dunham

Smolenski

2010

2010 IEEE International Power Modulator and High Voltage Conference

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At Cornell University, we have designed and built a DC photoemission electron gun that is capable of operating above 500 kV and up to 100 mA average current. Such a gun is the best choice as a high average power driver for an RF linear accelerator. High brightness photoemission guns must fulfill a difficult set of requirements in order to provide the types of beams needed for new x-ray light sources, including XHV vacuum properties, robust HV insulators, stable power supplies, electrode materials and preparation to reduce dark current, and electrode conditioning. In this paper, we will discuss these requirements, how to meet them, and the difficulties encountered along the way.

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High-voltage testing of a 500-kV dc photocathode electron gun

Cited by 28 publications

References 20 publications

Evaluation of niobium as candidate electrode material for dc high voltage photoelectron guns

Evaluation of niobium as candidate electrode material for dc high voltage photoelectron guns

Experimental investigation of an optimum configuration for a high-voltage photoemission gun for operation at≥500 kV

Design considerations for a high voltage DC photoemission electron gun at Cornell University

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