RF efficiency measurements of inductively-coupled plasma H<sup>−</sup> ion sources at accelerator facilities

Lawrie, Scott; Abel, Robert; Morais-Sarmento, Tiago; Tarvainen, O.; Welton, R. F.; Piller, C.; Stinson, Chris; Briefi, S.; Zielke, D.

doi:10.1088/1361-6463/acb5ac

Cited by 3 publications

(3 citation statements)

References 22 publications

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“…Figure 1 shows the latest design of the ion source. An RF efficiency measurement campaign [19] on the previous design iteration [18] indicated significant coupling between the RF-coil and the nearby stainless steel main housing. This resulted in heating which had a risk of demagnetising the low Curie temperature filter magnets.…”

Section: Design Featuresmentioning

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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Section: Design Featuresmentioning

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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“…In collaboration with RAL-ISIS [17] and following the methodology of Zielke [18] we conducted RF coupling efficiency measurements with both the SNS internal and external ion sources. These measurements were made to support modelling efforts which require the total RF power absorbed by the plasma (i.e.…”

Section: Mhz Rf Coupling Efficiency Measurementsmentioning

confidence: 99%

“…Next, P 𝑔 is determined with the source plasma lit as a function of I 0 as power is increased to operational levels. The above equation can then be solved for the RF coupling efficiency η for each source at nominal power level and was found to be η = 55-60% for the external antenna source and η = 75-77% for the internal antenna source [17,18]. This can help explain why it is more difficult to implement two-frequency excitation in an external versus an internal antenna source.…”

Section: Mhz Rf Coupling Efficiency Measurementsmentioning

confidence: 99%

Recent H^- ion source research and development at the Oak Ridge National Laboratory*

Welton,

Han,

Stockli

et al. 2023

J. Inst.

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The U.S. Spallation Neutron Source (SNS) is a state-of-the-art neutron scattering facility delivering the world's most intense pulsed neutron beams to a wide array of instruments which are used to conduct investigations in many fields of science and engineering. Neutrons are produced from spallation of liquid Hg by bombardment of short (∼1 μs), intense (∼35 A) pulses of protons delivered at 60 Hz by a storage ring which is fed by a high-intensity, ∼1 GeV H- LINAC. This facility has operated almost continuously since 2006, with ion source performance increasing over those years, and currently providing 50–60 mA of H- ions with a duty-factor of 6% for maintenance-free runs of several months with near 100% availability. Ion source research and development at ORNL has played a key role in enabling and supporting this success: this report provides an update on some of the ongoing ion source research and development efforts which have been undertaken since the previous Negative Ion Beams and Sources (NIBS) conference in 2020. These include significant improvements to H- beam current by extraction from a larger source outlet aperture and improvements to the electron dumping system which should eliminate the gradual loss of electrode voltage over the course of a run which has occasionally impacted SNS operations. Improvement and simplification of the plasma ignition system for the external antenna ion source, a long-standing problem, was also realized. Lastly, RF coupling efficiency was measured for both the SNS internal and external antenna ion sources.

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Plasma discharge experiments of a Faraday shieldless driver for high-power and long-pulse radio frequency ion source for NBI application

Liu,

Peng,

et al. 2024

Review of Scientific Instruments

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Due to the high stability and less maintenance, the radio frequency (RF) driven ion source is preferred for the neutral beam injection (NBI) system. In a popular design of the RF ion source for NBI application, a Faraday shield (FS) is installed inside the RF plasma driver to protect the discharge tube. However, the FS also brings some drawbacks, such as lowering the RF power transfer and increasing the processing difficulty. A prototype of the RF plasma driver without FS and with mature manufacturing technology has been developed by using a water-cooled discharge tube. After basic testing, this prototype was further tested under the RF plasma discharge experiments in views of high power, long pulse, and long term. The reliability and its plasma characteristics were the focus of these experiments, also for the hidden issues. The results show that the prototype could generate stable and high-density plasma without any damage or sputtering mark. An RF plasma discharge of 50 kW and 20 s has been achieved. The expected frequency tuning was equally effective on the prototype. Moreover, compared to the RF plasma driver with FS, the prototype could produce higher electron density in the extraction region under the same RF power. Of course, some of the shortcomings of the prototype have also been exposed in the experiments and will be improved in subsequent experiments.

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RF efficiency measurements of inductively-coupled plasma H⁻ ion sources at accelerator facilities

Cited by 3 publications

References 22 publications

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

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

Recent H^- ion source research and development at the Oak Ridge National Laboratory*

Plasma discharge experiments of a Faraday shieldless driver for high-power and long-pulse radio frequency ion source for NBI application

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RF efficiency measurements of inductively-coupled plasma H− ion sources at accelerator facilities

Cited by 3 publications

References 22 publications

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

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

Recent H- ion source research and development at the Oak Ridge National Laboratory*

Plasma discharge experiments of a Faraday shieldless driver for high-power and long-pulse radio frequency ion source for NBI application

Contact Info

Product

Resources

About

RF efficiency measurements of inductively-coupled plasma H⁻ ion sources at accelerator facilities

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

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

Recent H^- ion source research and development at the Oak Ridge National Laboratory*