110 mA operation of J-PARC cesiated RF-driven H− ion source

Ueno, Akira; Ohkoshi, K.; Ikegami, K.; Takagi, A.; Shinto, K.; Oguri, H.

doi:10.1063/5.0057552

Cited by 7 publications

(10 citation statements)

References 9 publications

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“…Setup of the RF circuit RF driven ion sources are typically realized as cylindrical ICPs, where a helical multi-turn RF coil is wrapped around the dielectric plasma chamber 2,3,15 or placed directly inside the plasma volume. 3,4 The power is supplied by an RF generator, which can be based on amplifier tubes or solid-state technology. In between the RF generator and the coil, a matching network is installed that tunes the impedance of the entire load (plasma, RF coil, and matching network combined) to a pure real resistance of typically 50 Ω, required at the output connector of the generator.…”

Section: Inductive Coupling In Rf Ion Sources: Fundamentalsmentioning

confidence: 99%

“…One of the key features of radio frequency (RF) driven H − ion sources, which are realized as inductively coupled plasmas (ICPs), is their capability to operate at considerably high power levels while being considered maintenance-free. Therefore, the concept has been chosen for the neutral beam injection (NBI) systems of the fusion experiment ITER, 1 and it is often applied as the front-end particle source for accelerators, [2][3][4] as both recipients require maximum reliability. However, due to the technological progression, state-ofthe-art (and envisaged future) accelerator and NBI systems impose challenging requirements, which implies that RF ion sources have to operate at increasingly demanding conditions.…”

Section: Introductionmentioning

confidence: 99%

“…As an example, the ion sources for ITER NBI need to operate low pressure (0.3 Pa) hydrogen or deuterium plasmas continuously for up to 3600 s. The discharges are generated in eight so-called drivers each having a volume of about 8 l and being powered with up to 100 kW (driving frequency 1 MHz) in order to meet the imposed requirements. 1 For accelerator sources, μs/ms-scale pulsed operation at slightly higher hydrogen pressures in the Pa regime is required, while the typical RF power levels are still around 50 kW (driving frequency 2 MHz) despite the much smaller volume of only about 0.3 l. [2][3][4] Due to the considerable power levels required in these sources, high currents 𝒪 (100 A) and voltages 𝒪 (10 kV) are imposed on the RF system. This causes high stress on the components of the RF circuit, which is obviously critical in view of maximum source reliability.…”

Section: Introductionmentioning

confidence: 99%

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Diagnostics of RF coupling in H− ion sources as a tool for optimizing source design and operational parameters

Briefi

Zielke

Rauner

et al. 2022

Review of Scientific Instruments

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Radio frequency (RF) driven H− ion sources are operated at very high power levels of up 100 kW in order to achieve the desired performance. For the experimental setup, these are demanding conditions possibly limiting the source reliability. Therefore, assessing the optimization potential in terms of RF power losses and the RF power transfer efficiency η to the plasma has moved to the focus of both experimental and numerical modeling investigations at particle accelerator and neutral beam heating sources for fusion plasmas. It has been demonstrated that, e.g., at typical neutral beam injection ion source setups, about half of the RF power provided by the generator is lost in the RF coil and the Faraday shield due to Joule heating or via eddy currents. In a best practice approach, it is exemplarily demonstrated at the ITER RF prototype ion source how experimental evaluation accompanied by numerical modeling of the ion source can be used to improve η. Individual optimization measures regarding the Faraday shield, the RF coil, the discharge geometry, the RF driving frequency, and the application of ferrites are discussed, which could reduce the losses by a factor of two. The provided examples are intended as exemplary guidelines, which can be applied at other setups in order to achieve with low-risk effort an optimized ion source design in terms of reduced losses and hence increased reliability.

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Section: Inductive Coupling In Rf Ion Sources: Fundamentalsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Diagnostics of RF coupling in H− ion sources as a tool for optimizing source design and operational parameters

Briefi

Zielke

Rauner

et al. 2022

Review of Scientific Instruments

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show abstract

“…As reported in the previous paper presenting the J-PARC IS 110 mA operation [9], the I H − was limited only by the space-charge force around the extraction region in the extraction gap (EG) of 3.2 mm, EE and acceleration gap (AG) of 7 mm. On April 2022, the withstand V T for the stable operation was increased higher than 70 kV by removing two weak points of the 2 MHz RF matching circuit.…”

Section: Ma 8 Hours Operation and Transverse Emittances Measurementmentioning

confidence: 70%

120 mA operation of J-PARC cesiated RF-driven H^- ion source

Ueno,

Ohkoshi,

Ikegami

et al. 2023

J. Inst.

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The Japan Proton Accelerator Research Complex (J-PARC) cesiated RF-driven H- ion source (IS) has been stably operated for about eight years by using an internal-RF-antenna developed at the Spallation Neutron Source (SNS). From Sep. 2018, the J-PARC 400 MeV LINAC has been steadily operated with the design H- ion beam intensity (IH- ) of 50 mA, when an about 60 mA beam is injected from the IS. At each end of about 3 months J-PARC operation, the IS supplies a 52.5 keV 72 mA beam for the LINAC 60 mA acceleration. The IS superior emittances predicted in a test-stand were proven by the high RFQ acceleration efficiency of 94.3% (IH-RFQ = 67.9 mA). The high intensity beam with transverse emittances suitable for the RFQ is produced with several unique measures, such as, slight water molecules addition into hydrogen plasma, the low temperature (about 70°C) operation of 45°-tapered 16-mm thick plasma electrode with the precise cesium (Cs) density control, the impurity elimination in the hydrogen plasma along with the filter-field optimization, the continuous-wave igniter plasma driven with a 42-W 30-MHz RF, and so on. The 120 mA operation results of the IS in the test-stand are presented in this paper. A 69.9 keV 120 mA H- ion beam, about 107.8 mA of which was inside the transverse emittances used for a common RFQ design, was stably operated with a duty factor of 4% (1 ms × 40 Hz). The IS is the benchmark one for the next generation high energy H- LINACs aiming for 100 mA class intensity.

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“…In the near-term, however, a parallel project is underway to replace the Penning source with a modern high power RF-driven source. Inspired by the successes of many other labs [10][11][12][13][14][15], we intend to generate sufficient H − beam current for present ISIS operations using only the volume process; that is without caesium enhancement. This will enable simpler operation; repeatable and reliable performance; no long-term caesium thermal stabilisation effects; reduced technician workload; reduced heavy-ion sputtering and longer lifetime: all beneficial for the user program.…”

Section: Jinst 18 C07021mentioning

confidence: 99%

First H^- beam extracted from the non-caesiated external RF-coil ion source at ISIS

Lawrie,

Abel,

Cahill

et al. 2023

J. Inst.

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A high power, high duty-cycle, non-caesiated negative hydrogen ion source is in development at the ISIS pulsed spallation neutron and muon facility. Stable operation of an inductively-coupled plasma pulsing at 50 Hz, 1 ms, 70 kW has been perfected with no apparent lifetime issues. Novel features compared to similar H- sources include a very low power microwave ignition gun, an adjustable permanent magnet filter field and multiple large 3D-printed components. This paper details the initial commissioning efforts required to generate a beam. An H- beam current of 10 mA was extracted on the first try in pure volume-production mode. Parameter sweeps and optimisation to reach the required 35 mA were put on hold to address ancillary equipment problems. Mitigation of RF pickup required major mechanical changes such as additional screening and magnetic shielding. Extraction voltage holding capabilities were investigated to cope with co-extracted electron current loading in excess of 0.7 A. Preliminary studies of the biased plasma electrode current showed that co-extracted electrons could be suppressed by increasing the magnetic filter field and gas flow.

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110 mA operation of J-PARC cesiated RF-driven H− ion source

Cited by 7 publications

References 9 publications

Diagnostics of RF coupling in H− ion sources as a tool for optimizing source design and operational parameters

Diagnostics of RF coupling in H− ion sources as a tool for optimizing source design and operational parameters

120 mA operation of J-PARC cesiated RF-driven H^- ion source

First H^- beam extracted from the non-caesiated external RF-coil ion source at ISIS

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110 mA operation of J-PARC cesiated RF-driven H− ion source

Cited by 7 publications

References 9 publications

Diagnostics of RF coupling in H− ion sources as a tool for optimizing source design and operational parameters

Diagnostics of RF coupling in H− ion sources as a tool for optimizing source design and operational parameters

120 mA operation of J-PARC cesiated RF-driven H- ion source

First H- beam extracted from the non-caesiated external RF-coil ion source at ISIS

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Product

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About

120 mA operation of J-PARC cesiated RF-driven H^- ion source

First H^- beam extracted from the non-caesiated external RF-coil ion source at ISIS