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論文

Present status of the J-PARC cesiated rf-driven H$$^-$$ ion source

神藤 勝啓; 大越 清紀; 池上 清*; 高木 昭*; 柴田 崇統*; 南茂 今朝雄*; 滑川 裕矢*; 上野 彰; 小栗 英知

AIP Conference Proceedings 2011, p.050018_1 - 050018_3, 2018/09

Operation of a cesiated RF-driven negative hydrogen ion source was initiated in September 2014 in response to the requirements of beam current upgrade in J-PARC linac. Delivery of the required beam current from the ion source to the J-PARC accelerators has been successfully performed. In 2016-2017 campaign, continuous operation of the ion source for approximately 1,840 hours (RUN#75 from April to July 2017) was achieved with beam current, macro pulse width and repetition of 45 mA, 500 $$mu$$s and 25 Hz, respectively. We present the operation status of the ion source and a high current H$$^-$$ beam with 70 mA extracted from the ion source for the further high-power upgrade in J-PARC accelerators.

論文

Observation of beam current fluctuation extracted from an RF-driven H$$^-$$ ion source

神藤 勝啓; 柴田 崇統*; 三浦 昭彦; 宮尾 智章*; 和田 元*

AIP Conference Proceedings 2011, p.080016_1 - 080016_3, 2018/09

In J-PARC, peak H$$^-$$ current of several tens mA is produced from a cesiated hydrogen plasma generated by a solid-state RF amplifier with the frequency of 2 MHz. In case of the high-intensity H$$^-$$ beam extracted from the ion source, the plasma density in the source chamber is so high that the ion sheath around the beam extraction area follows the RF oscillation. Because the ion plasma frequency defined by the ion density is much higher than the driving frequency. The potential fluctuation of the plasma is combined with the driving RF electric field and causes motion of charged particles in the plasma some changes. As a result, the H$$^-$$ beam extracted from the source plasma also fluctuates. The beam current signal from a Faraday cup was measured by a spectrum analyzer. A powerful frequency component at 2 MHz which is as same as that of the RF amplifier was also observed after the acceleration of RFQ linac located at the downstream of the ion source.

論文

Observation of plasma density oscillation with doubled value of RF frequency in J-PARC RF ion source

柴田 崇統*; 神藤 勝啓; 高木 昭*; 小栗 英知; 池上 清*; 大越 清紀; 南茂 今朝雄*; 内藤 富士雄*

AIP Conference Proceedings 2011, p.020008_1 - 020008_3, 2018/09

Balmer alpha line intensity in J-PARC Radio Frequency (RF) negative hydrogen ion source has been measured by photometry measurement. The line intensity shows several interesting time characteristics in different phases; (1) 2 MHz (RF frequency) oscillation just after plasma ignition and (2) 4 MHz (doubled RF frequency) and 2 MHz coupled oscillation in the steady-state. From the comparison between numerical analysis, it has been explained that electron acceleration in inductively coupled electromagnetic field takes place with 4 MHz frequency which results in the 4 MHz line intensity oscillation. From the understandings of the background physics, we can conclude that this fast photometry measurement is a good diagnosis tool to understand whether RF plasma is in E-mode or H-mode in general RF ion sources.

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