The large gap case for HV insulation in vacuum

Spolaore, P.; Bisoffi, G.; Cervellera, F.; Pengo, R.; Scarpa, Fabrizio

doi:10.1109/94.625353

Cited by 36 publications

(6 citation statements)

References 10 publications

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“…It is found that the BDV is proportional d 0.5 to 0.6 , where d is the gap length, which is similar to that 0093-3813/$26.00 © 2011 IEEE predicted by "clump theory" [3]. It is also consistent with data by INFN [5], which can support extrapolation of the 10-50 mm gap data for longer gap > 100 mm and BDV > 500 kV. The Weibull plot of the BDV without field concentration is shown in Fig.…”

Section: A Vacuum Gap Insulation Criteriasupporting

confidence: 82%

“…High-voltage vacuum gap insulation between electrodes has been studied experimentally [3]- [5]. Basic data on breakdown of vacuum gaps up to 50 mm between copper electrodes from [4] were used for the design of the accelerators of the JT-60U NBI, but recent studies have shown that increased vacuum gaps in the accelerator are necessary to obtain stable operation at 500 kV [6].…”

Section: Introductionmentioning

confidence: 99%

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1-MV Vacuum Insulation for the ITER Neutral Beam Injectors

Tanaka

Hemsworth

Kuriyama

et al. 2011

IEEE Trans. Plasma Sci.

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The ITER is an international project which aims to develop an experimental reactor as a step to realize fusion energy. To inject 33 MW of 1 MeV D 0 neutral beams for heating and current drive in ITER plasmas, D − ions are accelerated to 1 MeV. The electrostatic accelerator consists of five acceleration stages, and each acceleration gap has to withstand 200 kV. Gaps between the accelerator and the vacuum vessel, which is at ground potential, must sustain voltages up to 1 MV, and high-voltage vacuum insulation is a key issue. A minimum gap length of > 900 mm was selected for the 1-MV insulation distance. Development of a high-voltage bushing (HVB) which is a bulkhead and a feedthrough between the gas insulated HV transmission line and the beam source in vacuum is ongoing. The HVB consists of a stack of five large bore ceramic rings (1.56 m diameter), each 0.29 m in height. The five-stage insulation concept was applied to both the accelerator and the HVB for better voltage holding with multiple short gaps compared to fewer longer gaps. R&D on a single-stage HVB ceramic ring with the associated electrostatic screens was carried out, and voltage holding of −203 kV dc for 5 h was confirmed.

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Section: A Vacuum Gap Insulation Criteriasupporting

confidence: 82%

Section: Introductionmentioning

confidence: 99%

1-MV Vacuum Insulation for the ITER Neutral Beam Injectors

Tanaka

Hemsworth

Kuriyama

et al. 2011

IEEE Trans. Plasma Sci.

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“…This is probably because the cathode surface field becomes lower when the vacuum chamber is used as a cathode, resulting in less field emission and less microdischarge activity over a smaller anode area. This polarity effect seemed to play an important role in a study where 500 kV was applied between two electrodes with a 15-cm gap under a vacuum pressure of 5 × 10 −6 Pa without additional gas [24]. The voltages of the two electrodes were AE250 kV with respect to the grounded vacuum chamber.…”

Section: High-voltage Insulation In Vacuum For Large Gapmentioning

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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“…[4] were carefully done, and the underlying physics is sound. Based on the models for what is happening physically at the anode [5], it might be expected that a very low Z, high thermal conductivity anode would perform very well, leading to the possibility that beryllium may be a very good anode material.…”

Section: Field Emission and The Cathode-anode Gapmentioning

confidence: 99%

DC photoemission electron guns as ERL sources

Sinclair¹

2006

Nuclear Instruments and Methods in Physics Research Section A:

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The large gap case for HV insulation in vacuum

Cited by 36 publications

References 10 publications

1-MV Vacuum Insulation for the ITER Neutral Beam Injectors

1-MV Vacuum Insulation for the ITER Neutral Beam Injectors

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

DC photoemission electron guns as ERL sources

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