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Journal Articles

High-speed emittance measurements for beams extracted from J-PARC RF ion source

Shibata, Takanori*; Shinto, Katsuhiro; Wada, Motoi*; Oguri, Hidetomo; Ikegami, Kiyoshi*; Okoshi, Kiyonori; Nammo, Kesao*

AIP Conference Proceedings 2373, p.050002_1 - 050002_9, 2021/08

Oscillation of emittance and Twiss parameters in the negative ion beam from the J-PARC 2-MHz RF ion source is measured by applications of a double-slit emittance monitor located at the RFQ (Radio Frequency Quadrupole) entrance. The emittance monitor is equipped with a newly-developed 60 MS/s data acquisition system, so that beam current oscillation in a few MHz can be observed with enough time resolution. From the measurement, it is shown that the beam phase space consists of (1) a DC component in the beam core, (2) a 2-MHz oscillating component which takes place both in the beam core and the halo and (3) a doubled RF frequency (4 MHz) oscillation which slightly exists in the beam halo. The major component is the 2-MHz component, which resultantly decides the beam emittance oscillation frequency. A typical value of the beam emittance in the present experiment is 0.34 $$pi$$ mm-mrad, while the amplitude of the 2 MHz oscillation is around 0.04 $$pi$$ mm-mrad. The results indicate that the high-frequency oscillation component occupying about ten-percent of the beam from the RF source travels a few meters passing through a magnetic lens focusing system.

Journal Articles

NIBS 2020 reference sheets

Sarmento, T.*; W$"u$nderlich, D.*; Fantz, U.*; Friedl, R.*; Rauner, D.*; Tsumori, Katsuyoshi*; Shenjin, L.*; Chen, W.*; Bollinger, D.*; Oguri, Hidetomo; et al.

AIP Conference Proceedings 2373, p.110001_1 - 110001_18, 2021/08

In preparation for NIBS 2020 various labs prepared reference sheets containing key information about their ion sources and the machines that they serve. The contents of the reference sheets have been formatted and edited into this paper for posterity and ease of access.

Journal Articles

Reliability of J-PARC accelerator system over the past decade

Yamamoto, Kazami; Hasegawa, Kazuo; Kinsho, Michikazu; Oguri, Hidetomo; Hayashi, Naoki; Yamazaki, Yoshio; Naito, Fujio*; Yoshii, Masahito*; Toyama, Takeshi*

JPS Conference Proceedings (Internet), 33, p.011016_1 - 011016_7, 2021/03

The Japan Proton Accelerator Research Complex (J-PARC) is a multipurpose facility for scientific experiments. The accelerator complex consists of a 400-MeV Linac, a 3-GeV Rapid-Cycling Synchrotron (RCS) and a 30-GeV Main Ring synchrotron (MR). The RCS delivers a proton beam to the neutron target and MR, and the MR delivers the beams to the neutrino target and the Hadron Experimental Facility. The first operation of the neutron experiments began in December 2008. Following this, the user operation has been continued with some accidental suspensions. These suspensions include the recovery work due to the Great East Japan Earthquake in March 2011 and the radiation leak incident at the Hadron Experimental Facility. In this report, we summarize the major causes of suspension, and the statistics of the reliability of J-PARC accelerator system is analyzed. Owing to our efforts to achieve higher reliability, the Mean Time Between Failure (MTBF) has been improved.

Journal Articles

Phase space formation of high intensity 60 and 80 mA H$$^-$$ beam with orifice in J-PARC front-end

Shibata, Takanori*; Ikegami, Kiyoshi*; Nammo, Kesao*; Liu, Y.*; Otani, Masashi*; Naito, Fujio*; Shinto, Katsuhiro; Okoshi, Kiyonori; Okabe, Kota; Kondo, Yasuhiro; et al.

JPS Conference Proceedings (Internet), 33, p.011010_1 - 011010_6, 2021/03

Together with the intensity upgrade in J-PARC Linac Front-End, improvement of RFQ transmission ratio is an important task. This RFQ transmission ratio depends strongly upon the solenoid current settings in the low energy beam transport line (LEBT). In the present study, high beam current cases (72 mA and 88 mA H$$^-$$ beam current in LEBT) are investigated at a test-stand. Phase space distributions of the H$$^-$$ beam particles at the RFQ entrance are measured and compared with numerical results by Particle-In-Cell simulation. As a result, it has been clarified that a 15 mm $$phi$$ orifice for differential pumping of H$$_2$$ gas coming from the ion source plays a role as a collimator in these beam conditions. This leads to change the beam emittance and Twiss parameters at the RFQ entrance. Especially in the condition with the beam current up to 88 mA in LEBT, the beam collimation contributes to optimize the phase space distribution to the RFQ acceptance with relatively low solenoid current settings. As a higher solenoid current setting would be necessary to suppress the beam expansion due to high space charge effect, these results suggest that current-saving of the solenoids can be possible even in the higher beam intensity operations.

Journal Articles

Present status of the R&D of the superconducting linac for the JAEA-ADS

Yee-Rendon, B.; Tamura, Jun; Kondo, Yasuhiro; Hasegawa, Kazuo; Maekawa, Fujio; Meigo, Shinichiro; Oguri, Hidetomo

JPS Conference Proceedings (Internet), 33, p.011043_1 - 011043_5, 2021/03

The Japan Atomic Energy Agency (JAEA) has been working in the research and development of an Accelerator Driven Subcritical System (ADS) for the transmutation of nuclear waste. The ADS proposed by JAEA consists of a CW proton linac of 30 MW coupling with a subcritical core reactor. The accelerator will be operated with a beam current of 20 mA. Normal conducting Radio-Frequency Cavities (NRFC) and Superconducting Radio-Frequency Cavities (SRFC) will be used to achieve final energy of 1.5 GeV, and the SRFC will be employed for the main part of the acceleration: from 2 MeV to 1.5 GeV. In the first stage of the accelerator development, the focus was the design and optimization of the SRFC models and the beam optics. For the SRFC sections, the acceleration will be done by using Half Wave Resonators (HWR), Single Spokes (SS), and Elliptical cavities (Ellip) operating with a frequency of 162, 324, and 648 MHz, respectively. The beam optics were optimized satisfying the equipartitioning condition to control the emittance growth, which helped to reduce the beam halos and the beam loss.

Journal Articles

Error studies for the JAEA-ADS linac

Yee-Rendon, B.; Tamura, Jun; Kondo, Yasuhiro; Maekawa, Fujio; Meigo, Shinichiro; Oguri, Hidetomo

Proceedings of 17th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.33 - 37, 2020/09

Japan Atomic Energy Agency (JAEA)- Accelerator Driven System (ADS) linac consists of a CW proton accelerator with a beam current of 20 mA driven with the energy of 1.5 GeV. Most of the beam acceleration is achieved by using superconducting cavities to obtain high acceleration efficiency at CW mode. The main superconducting linac is composed of five families of cavities (Half Wave resonators, Spokes resonators, and Elliptical cavities) with theirs respectively magnets. Due to the large beam power in the linac of 30 MW and the high reliability required for the ADS project, a robust beam optic designed is necessary to have a stable beam operation and control the beam loss power. The JAEA-ADS linac is composed of several sections and components; thus, the misalignment of these elements together with field errors enhance the beam loss rate and compromises the safety of the linac. To this end, an error linac campaign was launched to estimate the error tolerance of the components and implement a correction scheme to reduce the beam loss power around the linac.

Journal Articles

Evaluation of the bunch-shape monitor for the high-intensity proton beam

Kitamura, Ryo; Futatsukawa, Kenta*; Hayashi, Naoki; Hirano, Koichiro; Kondo, Yasuhiro; Kosaka, Satoshi*; Miyao, Tomoaki*; Nemoto, Yasuo*; Morishita, Takatoshi; Oguri, Hidetomo

Proceedings of 17th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.251 - 253, 2020/09

A bunch-shape monitor (BSM) in the low-energy region is being developed in the J-PARC linac to accelerate the high-intensity proton beam with the low emittance. A highly-oriented pyrolytic graphite (HOPG) was introduced as the target of the BSM to mitigate the thermal loading. The stable measurement of the BSM was realized thanks to the HOPG target, while the tungsten target was broken by the thermal loading from the high-intensity beam. However, since the longitudinal distribution measured with the BSM using the HOPG target was wider than the expected one, the improvement of tuning parameters is necessary for the BSM. The BSM consists of an electron multiplier, a bending magnet, and a radio-frequency deflector, which should be tuned appropriately. Behavior of these components were investigated and tuned. The longitudinal distribution measured with the BSM after the tuning was consistent with the expected one.

Journal Articles

Upgrade of the 3-MeV linac for testing of accelerator components at J-PARC

Kondo, Yasuhiro; Hirano, Koichiro; Ito, Takashi; Kikuzawa, Nobuhiro; Kitamura, Ryo; Morishita, Takatoshi; Oguri, Hidetomo; Okoshi, Kiyonori; Shinozaki, Shinichi; Shinto, Katsuhiro; et al.

Journal of Physics; Conference Series, 1350, p.012077_1 - 012077_7, 2019/12

 Times Cited Count:0 Percentile:0.07

We have upgraded a 3-MeV linac at J-PARC. The ion source is same as the J-PARC linac's, and the old 30-mA RFQ is replaced by a spare 50-mA RFQ, therefore, the beam energy is 3 MeV and the nominal beam current is 50 mA. The main purpose of this system is to test the spare RFQ, but also used for testing of various components required in order to keep the stable operation of the J-PARC accelerator. The accelerator has been already commissioned, and measurement programs have been started. In this paper, present status of this 3-MeV linac is presented.

Journal Articles

Longitudinal measurements and beam tuning in the J-PARC linac MEBT1

Otani, Masashi*; Futatsukawa, Kenta*; Miyao, Tomoaki*; Liu, Y.*; Hirano, Koichiro; Kondo, Yasuhiro; Miura, Akihiko; Oguri, Hidetomo

Journal of Physics; Conference Series, 1350, p.012078_1 - 012078_5, 2019/12

 Times Cited Count:0 Percentile:0.07

The Japan Proton Accelerator Research Complex (J-PARC) linac is operated with design peak current of 50 mA from 2018. For operation with such a high beam current, itis important to understand transverse and longitudinal beam properties especially in low-velocity region. A medium energy beam transport (MEBT1) line between the 3-MeV radio-frequency quadrupole linac (RFQ) and the 50-MeV drift-tube linac (DTL) is a 3-m-long transport line to match the beam to the DTL and produce a macro pulse configuration for a 3-GeV rapid-cycling synchrotron (RCS). In this paper, recent measurements and beam tuning results in MEBT1 will be presented.

Journal Articles

Bunch shape monitor for the high-intensity H$$^{-}$$ beam with 3 MeV using the carbon material

Kitamura, Ryo; Futatsukawa, Kenta*; Hayashi, Naoki; Hirano, Koichiro; Kosaka, Satoshi*; Miyao, Tomoaki*; Moriya, Katsuhiro; Nemoto, Yasuo*; Oguri, Hidetomo

Proceedings of 16th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.51 - 54, 2019/07

The longitudinal measurement and tuning at the beam transport after the RFQ are important to reduce the beam loss and the emittance growth in the J-PARC linac, when the high-intensity H$$^{-}$$ beam of more than 60 mA is supplied. The new bunch shape monitor (BSM) using the carbon-nanotube (CNT) wire is necessary to measure the bunch shape of the high-intensity H$$^{-}$$ beam with 3 MeV, because the CNT wire has a high-temperature tolerance and a small energy deposit. However, when the high voltage was applied to the CNT wire to extract the secondary electron derived, the discharge prevents the power supply from applying the voltage. Therefore, the discharge should be suppressed to measure the bunch shape with stability. Considering the characteristics of the CNT as the emitter, when the length of the CNT wire was short, the high voltage of -10 kV was applied to the CNT wire. The current status and future prospects of the BSM using the CNT wire are reported in this presentation.

Journal Articles

Status of J-PARC accelerators

Hasegawa, Kazuo; Kinsho, Michikazu; Oguri, Hidetomo; Yamamoto, Kazami; Hayashi, Naoki; Yamazaki, Yoshio; Naito, Fujio*; Yoshii, Masahito*; Toyama, Takeshi*; Yamamoto, Noboru*; et al.

Proceedings of 16th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1235 - 1239, 2019/07

After the summer shutdown in 2018, the J-PARC restarted user operation in late October. While beam power to the Materials and Life Science Experimental Facility (MLF) was 500 kW as before the summer shutdown, linac beam current was increased from 40 to 50 mA. Operation of the Main Ring (MR) was suspended due to the modification and/or maintenance of the Superkamiokande (neutrino detector) and Hadron experimental facility. The user operation was resumed in the middle of February for the Hadron experimental facility at 51 kW. But on March 18, one of the bending magnets in the beam transport line to the MR had a failure. It was temporary recovered and restored beam operation on April 5, but the failure occurred again on April 24 and the beam operation of the MR was suspended. In the fiscal year of 2018, the availabilities for the MLF, neutrino and hadron facilities are 94%, 86%, and 74%, respectively.

Journal Articles

Cavity and optics design of the accelerator for the JAEA-ADS project

Yee-Rendon, B.; Tamura, Jun; Kondo, Yasuhiro; Hasegawa, Kazuo; Maekawa, Fujio; Meigo, Shinichiro; Oguri, Hidetomo

Proceedings of 16th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.107 - 111, 2019/07

Journal Articles

Progress of long-time operation and industrial use of negative ion source for particle accelerator

Oguri, Hidetomo

Purazuma, Kaku Yugo Gakkai-Shi, 95(7), p.340 - 344, 2019/07

no abstracts in English

Journal Articles

Development of the bunch shape monitor using the carbon-nano tube wire

Kitamura, Ryo; Hayashi, Naoki; Hirano, Koichiro; Kondo, Yasuhiro; Moriya, Katsuhiro; Oguri, Hidetomo; Futatsukawa, Kenta*; Miyao, Tomoaki*; Otani, Masashi*; Kosaka, Satoshi*; et al.

Proceedings of 10th International Particle Accelerator Conference (IPAC '19) (Internet), p.2543 - 2546, 2019/06

A bunch shape monitor (BSM) is one of the important instruments to measure the longitudinal phase space distribution. For example in the J-PARC linac, three BSMs using the tungsten wire are installed at the ACS section to measure the bunch shapes between the accelerating cavities. However, this conventional BSM is hard to measure the bunch shape of H$$^{-}$$ beam with 3 MeV at the beam transport between the RFQ and DTL sections, because the wire is broken around the center region of the beam. The new BSM using the carbon-nano-tube (CNT) wire is being developed to be able to measure the bunch shape of the H$$^{-}$$ beam with 3 MeV. The careful attention should be paid to apply the high voltage of $$-$$10 kV to the CNT wire. The several measures are taken to suppress the discharge from the wire and operate the CNT-BSM. This presentation reports the current status of the development and future prospective for the CNT-BSM.

Journal Articles

Numerical and experimental study of H$$^{-}$$ beam dynamics in J-PARC LEBT

Shibata, Takanori*; Ikegami, Kiyoshi*; Liu, Y.*; Miura, Akihiko; Naito, Fujio*; Nammo, Kesao*; Oguri, Hidetomo; Okoshi, Kiyonori; Otani, Masashi*; Shinto, Katsuhiro; et al.

Proceedings of 29th International Linear Accelerator Conference (LINAC 2018) (Internet), p.519 - 521, 2019/01

Transport process of negative hydrogen ion (H$$^{-}$$) in LEBT (Low Energy Beam Transport) is investigated by comparison of experimental and numerical results. A three dimensional Particle-In-Cell (PIC) particle transport model has been developed in order to take into account (i) axial magnetic field by two solenoids in J-PARC LEBT and (ii) radial electric field by space charge (SC) effect. Ratio of H$$^-$$ beam particles inside the RFQ (Radio Frequency Quadrupole) acceptance to the total particles at the RFQ entrance is calculated for different current conditions in LEBT solenoid 1 and 2. The results are compared with RFQ transmission rate measured in the J-PARC linac commissioning. The double peak of RFQ transmission rate to the solenoid applied current seen in the measurement is explained by the calculation results. The results indicate that presence of the LEBT orifice for differential pumping plays a role as a collimator to reduce emittance at RFQ entrance.

Journal Articles

Solving beam intensity bottlenecks and 100 mA operation of J-PARC cesiated RF-driven H$$^{-}$$ ion source

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

AIP Conference Proceedings 2052, p.050003_1 - 050003_7, 2018/12

 Times Cited Count:2 Percentile:83.27

In order to specify the beam intensity bottlenecks of the J-PARC cesiated RF-driven H$$^{-}$$ ion source, the extraction and acceleration voltages (V$$_{rm E}$$ and V$$_{rm A}$$) higher than the design values of 10 kV and 40 kV were examined. A 100 mA beam, whose about 93 mA has transverse emittances used for a common RFQ design, was stably operated with a duty factor of 5% (1 ms $$times$$ 50 Hz) by using the V$$_{rm E}$$ and V$$_{rm A}$$ of 12.4 kV and 49.6 kV, respectively. This breakthrough with important information on the space-charge limited bottlenecks in the extraction and acceleration gaps will derive the optimal electrode shapes for the source operated with a beam intensity higher than 100 mA and realize the next generation benchmark H$$^{-}$$ ion source for high intensity and high energy H$$^{-}$$ LINACs.

Journal Articles

Progress of the J-PARC cesiated rf-driven negative hydrogen ion source

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

AIP Conference Proceedings 2052, p.050002_1 - 050002_7, 2018/12

 Times Cited Count:2 Percentile:83.27

In the 2017/2018 campaign, the J-PARC cesiated rf-driven negative hydrogen (H$$^-$$) ion source producing H$$^-$$ beam with the beam current of 47 mA accomplished three long-term operations more than 2,000 hours without any serious issues. On the final day of this campaign, the ion source produced an H$$^-$$ beam current of 72 mA so that the linac commissioning group could demonstrate the beam current of 60 mA at the linac exit. We are also conducting an endurance test of a J-PARC-made antenna at a test bench. The antenna achieved the operation time approximately 1,400 hours.

Journal Articles

Longitudinal bunch size measurement using an RF deflector

Otani, Masashi*; Futatsukawa, Kenta*; Hirano, Koichiro; Kondo, Yasuhiro; Miura, Akihiko; Oguri, Hidetomo; Liu, Y.*

Nuclear Instruments and Methods in Physics Research A, 908, p.313 - 317, 2018/11

 Times Cited Count:0 Percentile:0.02(Instruments & Instrumentation)

It is extremely important to diagnose beams in accelerators to improve accelerator operation. In the low velocity section of a proton or heavy ion linac, the diagnostic method for longitudinal beam properties is less established compared to that for transverse properties. We have developed a new diagnostic method for the longitudinal bunch size by utilizing an RF deflector. We evaluated the uncertainty in bunch size measurement through simulation, and it was obtained as 0.5$$^{circ}$$. In addition, we measured longitudinal beam emittance through bunch size measurements at several RF amplitudes of an upstream buncher. The measured emittance was 0.13$$pm$$0.01$$pi$$ deg$$cdot$$MeV, which was consistent with the simulation result.

Journal Articles

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

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

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

 Times Cited Count:3 Percentile:91.26

Journal Articles

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

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

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

 Times Cited Count:4 Percentile:94.9

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