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Journal Articles

Operation status of the J-PARC RF-driven H$$^{-}$$ ion source

Oguri, Hidetomo; Okoshi, Kiyonori; Ikegami, Kiyoshi*; Takagi, Akira*; Asano, Hiroyuki; Shibata, Takanori*; Nammo, Kesao*; Ueno, Akira; Shinto, Katsuhiro

AIP Conference Proceedings 1869, p.030053_1 - 030053_7, 2017/08

 Times Cited Count:5 Percentile:3.46

A cesiated RF-driven negative hydrogen ion source was started to operate in September, 2014 in response to the need for upgrading J-PARC's linac beam current. The ion source mainly comprises a stainless-steel plasma chamber, a beam extractor, and a large vacuum chamber with two turbo molecular pumps of 1500 L/s for differential pumping. The ion source has been successfully providing the required beam current to the accelerator without any significant issues other than a single-incident antenna failure occurred in October, 2014. Continuous operation for approximately 1,000 h was achieved with a beam current and duty factor of 45 mA and 1.25 % (0.5 msec and 25 Hz), respectively. In this paper, we will present the some operation parameters and the beam stability through the long-term user operation.

Journal Articles

High density plasma calculation of J-PARC RF negative ion source

Shibata, Takanori*; Asano, Hiroyuki; Ikegami, Kiyoshi*; Naito, Fujio*; Nammo, Kesao*; Oguri, Hidetomo; Okoshi, Kiyonori; Shinto, Katsuhiro; Takagi, Akira*; Ueno, Akira

AIP Conference Proceedings 1869, p.030017_1 - 030017_11, 2017/08

 Times Cited Count:4 Percentile:5.35

From September 2014, operation of Cs-seeded, multi-cusp, Radio Frequency (RF), hydrogen negative ion source (J-PARC source) has been started. The operation for 1,000 hours of J-PARC source has been achieved with H$$^{-}$$ beam current 45 mA and duty factor of 1.25 % (0.5 msec and 25 Hz). In the present study, mechanisms of hydrogen plasma ramp-up and H$$^{-}$$ production/transport processes in the steady state (which lasts for few 100 us) are investigated by numerical modeling for RF plasma. In the simulation, charged particle (e, H$$^{+}$$, H$$_2^{+}$$, and Cs$$^{+}$$) transport, time variations of inductive and capacitive electromagnetic field, collision processes between charged and neutral (H, H$$_{2}$$) particles are solved simultaneously. The model is applied to KEK parallel computation System-A with 32 nodes and 256 GB memory in order to solve high density RF plasma up to around 10$$^{18}$$ m$$^{-3}$$ with adequate statisticity. In the presentation, time variations of plasma density distributions and average energy are shown with electromagnetic field variations.

Journal Articles

Emittance improvements of cesiated RF-driven H$$^{-}$$ ion source to enable 60 mA operation of high-energy and high-intensity LINACs by plasma impurity controls

Ueno, Akira; Okoshi, Kiyonori; Ikegami, Kiyoshi*; Takagi, Akira*; Oguri, Hidetomo

AIP Conference Proceedings 1869, p.030011_1 - 030011_10, 2017/08

 Times Cited Count:5 Percentile:3.46

At the Japan Proton Accelerator Research Complex (J-PARC), the operation of a 400-MeV linear accelerator (LINAC) with an extraction H$$^{-}$$ ion beam intensity of 60 mA is under investigation. This intensity is 20% higher than the 50 mA achieved by the J-PARC LINAC and about 50% higher than those of operating similar LINACs in the world. Recently, the J-PARC cesiated RF-driven H$$^{-}$$ ion source successfully produces a beam enabling the 60 mA operation. A 66-mA beam with 95%-beam transverse normalized rms emittance of 0.23 $$pi$$mm$$cdot$$mrad is produced by controlling the impurities of argon, nitrogen and water molecules in the hydrogen plasma and tuning rod-filter-field.

Journal Articles

Transverse RMS emittance evaluation based upon explicit and reasonable definitions of 100% and 95% beams

Ueno, Akira; Okoshi, Kiyonori; Ikegami, Kiyoshi*; Takagi, Akira*; Oguri, Hidetomo

AIP Conference Proceedings 1869, p.030052_1 - 030052_7, 2017/08

 Times Cited Count:3 Percentile:9.1

In order to compare brightnesses of beams produced by different ion sources, a transverse emittance evaluation procedure with consistency and small ambiguity for different background noises is required. The procedure to evaluate emittances of beams produced by the Japan Proton Accelerator Research Complex (J-PARC) cesiated RF-driven H$$^{-}$$ ion source is presented in this paper. The ambiguity in emittance evaluations is eliminated by defining uniquely 100% and 95% beams with a reasonably corrected beam-signal base-level. Two 95%-beam transverse normalized root mean square emittances of beams, which are produced with almost the same 2-MHz RF power and cesiation condition but with different background noise, are estimated as almost the same values by this procedure.

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