Breakdown Oscillations of the ISIS H<sup>−</sup> Penning Ion-Source Hydrogen–Cesium Discharge

Tarvainen, O.; Abel, Robert; Lawrie, Scott; Faircloth, D. C.; Macgregor, John; Morais-Sarmento, Tiago; Wood, T.

doi:10.1109/tps.2019.2940830

Cited by 5 publications

(7 citation statements)

References 40 publications

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“…Further details are reported in Ref. 9. It is evident from the figure that the duration of the transient is reduced by an order of magnitude with the improved power supply circuit, which allows reducing the FETS discharge pulse length from 2.2 ms closer to…”

Section: Breakdown Transient Suppressionmentioning

confidence: 91%

“…The pulsed discharge power supply with its negative voltage terminal connected to the cathode is operated in current regulated mode; i.e., the discharge voltage VD (cathode-anode potential difference) is a free parameter, adjusted by the cathode and source mounting flange providing electrical and thermal isolation between the two. Recent experiments 9 have revealed that the cesium (Cs) coverage of the cathode surfaces is above 0.5-0.7 monolayers, corresponding to the predicted minimum of the work function, most likely close to the 2.1 eV work function of Cs. Therefore, following Ref.…”

Section: Qualitative Model Of the Beam Current Droopmentioning

confidence: 99%

“…It has been hypothesized that the breakdown oscillations are due to Cs dynamics causing the surface work function and electron emission from the cathode surfaces to fluctuate periodically. 14 However, recent experiments 9 with the ISIS H − Penning ion source have revealed that the breakdown oscillations are primarily driven by the discharge power supply and its auxiliary circuits, whereas Cs dynamics have a smaller effect on the transient. This is demonstrated in Fig.…”

Section: Breakdown Transient Suppressionmentioning

confidence: 99%

“…The origin of the beam current droop is described hereafter, whereas the model of the breakdown oscillations is presented elsewhere. 9 In short, the difference between the discharge breakdown voltage and the steady-state discharge voltage leads to an ignition transient, i.e., the discharge current fluctuating periodically with a diminishing amplitude for 100 μs (order of magnitude) before the cesium-hydrogen plasma reaches a quiescent equilibrium.…”

Section: Introductionmentioning

confidence: 99%

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Extending the pulse length of the ISIS H− Penning ion source

Tarvainen

Abel

Lawrie

et al. 2019

Review of Scientific Instruments

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The ISIS Penning ion source can routinely produce a 55 mA beam of negative hydrogen ions in 250 μs pulses at 50 Hz repetition rate. Extending the beam pulse length to 2 ms requires eliminating the 15%-30% droop of the current observed in long pulse operation and benefits from the suppression of discharge breakdown oscillations otherwise forcing to prolong the pulse length to 2.2 ms or longer. The droop can be compensated by ramping the discharge current during the pulse, whereas the discharge oscillations are suppressed by modifying the ancillary circuit of the pulsed arc power supply.

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Section: Breakdown Transient Suppressionmentioning

confidence: 91%

Section: Qualitative Model Of the Beam Current Droopmentioning

confidence: 99%

Section: Breakdown Transient Suppressionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Extending the pulse length of the ISIS H− Penning ion source

Tarvainen

Abel

Lawrie

et al. 2019

Review of Scientific Instruments

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“…Most of the sputtering damage is believed to occur during the first 100-200 µs of the discharge pulse when so-called breakdown oscillations result in drastic fluctuations of the discharge voltage and current. The breakdown oscillations can be suppressed by improving the discharge power supply and its auxiliary circuits, which presumably leads to reduced sputtering damage [36]. The formation of the macroscopic flakes is thought to be related to the thermal cycling of the cathode and hydrogen embrittlement of the metal.…”

Section: The Isis Penning Hion Sourcementioning

confidence: 99%

Negative hydrogen ion sources for particle accelerators: Sustainability issues and recent improvements in long-term operations

Welton

Bollinger

Dehnel

et al. 2022

J. Phys.: Conf. Ser.

Self Cite

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High brightness, negative hydrogen ion sources are used extensively in scientific facilities operating worldwide. Negative hydrogen beams have become the preferred means of filling circular accelerators and storage rings as well as enabling efficient extraction from cyclotrons. Several well-known facilities now have considerable experience with operating a variety of sources such as RF-, filament-, magnetron- and Penning-type H- ion sources. These facilities include the US Spallation Neutron Source (SNS), Japan Proton Accelerator Research Complex (J-PARC), Rutherford Appleton Laboratory (RAL-ISIS), Los Alamos Neutron Science Center (LANSCE), Fermi National Accelerator Laboratory (FNAL), Brookhaven National Laboratory (BNL), numerous installations of D-Pace (licenced by TRIUMF) ion sources used mainly on cyclotrons and, most recently, the CERN-LINAC-1 injector. This report first summarizes the current performance of these ion sources in routine, daily operations with attention toward source service-periods and availability metrics. Sustainability issues encountered at each facility are also reported and categorized to identify areas of common concern and key issues. Recent ion source improvements to address these issues are also discussed as well as plans for meeting future facility upgrade requirements.

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A review of diagnostic techniques for high-intensity negative ion sources

Tsumori

Wada²

2021

Applied Physics Reviews

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Plasma and beam diagnostic methods for high-current-density negative ion sources are reviewed. The pulse laser–induced photodetachment method was widely used to measure negative ion density in the ion source plasma. The method was used to understand fundamental processes of negative hydrogen (H−) ion formation and destruction in hydrogen plasmas. Species composition and plasma parameters in H− ion sources can be estimated from optical emission spectroscopy data, while electrostatic probes are utilized to obtain local plasma parameters in the ion source. Plasma transport toward the extractor is studied by combining a laser beam for photodetachment and a structured electrostatic probe to visualize a flow pattern of H− ions. Spatial distributions of large-area H− ion beams are monitored by infrared thermography images, showing interactions among multiple beamlets. These diagnostic methods deepen the understanding of how H− ions are produced and extracted through beam-forming apertures. The acquired knowledge on ion source plasma and beam transport improves the ion source design of the next-generation H− ion sources for fusion experiments and accelerators. The essence of research and development for negative ion source study is summarized through briefly tracing the history.

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Breakdown Oscillations of the ISIS H⁻ Penning Ion-Source Hydrogen–Cesium Discharge

Cited by 5 publications

References 40 publications

Extending the pulse length of the ISIS H− Penning ion source

Extending the pulse length of the ISIS H− Penning ion source

Negative hydrogen ion sources for particle accelerators: Sustainability issues and recent improvements in long-term operations

A review of diagnostic techniques for high-intensity negative ion sources

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Breakdown Oscillations of the ISIS H− Penning Ion-Source Hydrogen–Cesium Discharge

Cited by 5 publications

References 40 publications

Extending the pulse length of the ISIS H− Penning ion source

Extending the pulse length of the ISIS H− Penning ion source

Negative hydrogen ion sources for particle accelerators: Sustainability issues and recent improvements in long-term operations

A review of diagnostic techniques for high-intensity negative ion sources

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Product

Resources

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Breakdown Oscillations of the ISIS H⁻ Penning Ion-Source Hydrogen–Cesium Discharge