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Journal Articles

Negative hydrogen ion beam irradiation experiments of beam scrapers using the J-PARC 3 MeV-Linac

Hirano, Koichiro; Ishiyama, Tatsuya; Kurihara, Toshikazu*; Sugimura, Takashi*; Maruta, Tomofumi*

Proceedings of 14th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.847 - 852, 2017/12

Beam scrapers made of carbon composite have been used in the MEBT1 between a 324 MHz RFQ and a 50-MeV DTL of the J-PARC Linac. We have conducted the scraper irradiation test with the 3 MeV linac. The test piece of the scraper was irradiated by the H$$^{-}$$ beam up to particle number of 1.2E20. We measured the surface temperature of more than 3000$$^{circ}$$C using a high-speed radiation thermometer and observed the irradiation damage on the scraper by using the laser microscope. When the surface temperature exceeded 2900$$^{circ}$$C, the ionic current of carbon and the irradiation damage on the surface of the test piece rapidly increased. This paper describes beam irradiation test results of the scraper.

Journal Articles

Observation of beam loss proton tracks at 400 MeV J-PARC Linac

Sako, Hiroyuki; Miura, Akihiko; Miyao, Tomoaki*; Maruta, Tomofumi*

Proceedings of 14th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.545 - 547, 2017/12

Journal Articles

LEBT commissioning of the J-PARC LINAC

Shibata, Takanori*; Ikegami, Kiyoshi*; Liu, Y.*; Maruta, Tomofumi*; Naito, Fujio*; Takagi, Akira*; Asano, Hiroyuki; Kondo, Yasuhiro; Miura, Akihiko; Oguri, Hidetomo; et al.

Proceedings of 28th International Linear Accelerator Conference (LINAC 2016) (Internet), p.251 - 253, 2017/05

After upgrade of J-PARC Linac in 2014, Low Energy Beam Transport (LEBT) beam commissioning of the J-PARC LINAC has been made for improving H$$^{-}$$ beam intensity extracted from Linac. Currents of two solenoid coils and steering magnets in LEBT are optimized with extraction and acceleration voltages for static acceleration in ion source (IS) which decides on an initial emittance diagram of H$$^{-}$$ beam. As a result of LEBT and IS parameter optimization, beam transmission rate of RFQ has been reached up to 96% in 50 mA H$$^{-}$$ current operation. Moreover, PIC-MC (Particle-In-Cell Monte-Carlo) simulation models developed for H$$^{-}$$ transport in LEBT. Comparison between experimental and numerical results are presented to clarify beam physics from IS exit to RFQ entrance.

Journal Articles

Detection of H$$^{0}$$ particles in MEBT2 chicane of J-PARC linac

Tamura, Jun; Miura, Akihiko; Morishita, Takatoshi; Okabe, Kota; Yoshimoto, Masahiro; Ao, Hiroyuki*; Futatsukawa, Kenta*; Maruta, Tomofumi*; Miyao, Tomoaki*; Nemoto, Yasuo*

Proceedings of 8th International Particle Accelerator Conference (IPAC '17) (Internet), p.2308 - 2310, 2017/05

In the Japan Proton Accelerator Research Complex (J-PARC), H$$^{0}$$ particles generated by collisions of accelerated H$$^{-}$$ beams with residual gases are considered as one of the key factors of the residual radiation in the high energy accelerating section of the linac. To diagnose the H$$^{0}$$ particles, the new analysis line for the H$$^{0}$$ particles was installed in the matching section from the separated-type drift tube linac (SDTL) to the annular-ring coupled structure linac (ACS). In the analysis line, the accelerated H$$^{-}$$ ions travel in chicane orbit by the four dipole magnets. In the beam commissioning, we directly detected the H$$^{0}$$ particles by using a carbon plated installed to a wire scanner monitor and indirectly detected the H$$^{0}$$ particles by using a scintillation detector. We also confirmed that the signals change with vacuum condition in the SDTL section.

Journal Articles

Beam tuning for longitudinal profile at J-PARC linac

Miura, Akihiko; Liu, Y.*; Maruta, Tomofumi*; Miyao, Tomoaki*

Proceedings of 5th International Beam Instrumentation Conference (IBIC 2016) (Internet), p.150 - 153, 2017/03

no abstracts in English

Journal Articles

Development of beam scrapers using a 3-Mev linac at J-PARC

Hirano, Koichiro; Asano, Hiroyuki; Ishiyama, Tatsuya; Ito, Takashi; Okoshi, Kiyonori; Oguri, Hidetomo; Kondo, Yasuhiro; Kawane, Yusuke; Kikuzawa, Nobuhiro; Sato, Yoshikatsu; et al.

Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.310 - 313, 2016/11

We have used a beam scraper with the incident angle of 65deg to reduce the beam power deposition density in the MEBT between a 324 MHz RFQ and a 50-MeV DTL of the J-PARC linac. The 65$$^{circ}$$ scraper was irradiated by the H$$^{-}$$ beam up to particle number of 1.47E22. We observed a lot of surface projections with several hundred micrometers high in the beam irradiation damage on the scraper by using the laser microscope. In order to study the limits of scrapers, we constructed a new 3 MeV linac at J-PARC. We will conduct the scraper irradiation test at the end of this year.

Journal Articles

Development of a vertical collimator at the mebt1 of J-PARC linac

Sugimura, Takashi*; Maruta, Tomofumi*; Hirano, Koichiro

Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.307 - 309, 2016/11

There is an upgrade plan of J-PARC (Japan Proton Accelerator Research Complex) Linac from currently operated beam parameters such as, beam current of 40 mA, beam pulse width of 0.5msec and repetition of 25 Hz, to 50 mA, 0.5msec and 50 Hz, respectively. To reduce beam loss during a beam acceleration is a must task to accelerate a high power beam. At J-PARC Linac, a beam from an ion source followed by RFQ (Radio Frequency Quadrupole) injected into a series of DTLs (Drift Tube Linac) through a MEBT1 (Medium Energy Beam Transport 1), where a beam matching and a beam pulse forming are carried out at the beam energy of 3 MeV. There are some locally activated spots in DTL area at the current beam power level so that some kind of mitigation measure is required. Beam simulation results show that the beam loss at the DTL area can be reduced if there is a pair of vertical beam collimators. This paper reports a design and fabrication status of new vertical collimators.

Journal Articles

Beam commissioning of the linac for iBNCT

Naito, Fujio*; Anami, Shozo*; Ikegami, Kiyoshi*; Uota, Masahiko*; Ouchi, Toshikatsu*; Onishi, Takahiro*; Oba, Toshiyuki*; Obina, Takashi*; Kawamura, Masato*; Kumada, Hiroaki*; et al.

Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1244 - 1246, 2016/11

The proton linac installed in the Ibaraki Neutron Medical Research Center is used for production of the intense neutron flux for the Boron Neutron Capture Therapy (BNCT). The linac consists of the 3-MeV RFQ and the 8-MeV DTL. Design average beam current is 10mA. Target is made of Beryllium. First neutron production from the Beryllium target was observed at the end of 2015 with the low intensity beam as a demonstration. After the observation of neutron production, a lot of improvement s was carried out in order to increase the proton beam intensity for the real beam commissioning. The beam commissioning has been started on May 2016. The status of the commissioning is summarized in this report.

Journal Articles

Phase resolution measurement for the Bunch Shape Monitor at J-PARC Linac

Miyao, Tomoaki*; Maruta, Tomofumi*; Liu, Y.*; Miura, Akihiko

Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1094 - 1096, 2016/11

no abstracts in English

Journal Articles

Bunch length analysis of negative hydrogen ion beam in J-PARC linac

Miura, Akihiko; Hayashi, Naoki; Maruta, Tomofumi*; Liu, Y.*; Miyao, Tomoaki*; Fukuoka, Shota*

Proceedings of 4th International Beam Instrumentation Conference (IBIC 2015) (Internet), p.386 - 389, 2016/02

We have used bunch shape monitors (BSMs) to measure the longitudinal bunch length of negative hydrogen ion beam in the J-PARC linac. In order to evaluate the measurement errors with peak beam current increasing, we observed waveforms with various beam current. As the result, an RMS bunch length depends on the peak beam current and the bending at the pulse head grows with the peak beam current. We also compared the data taken at an off-center beam to avoid the thermal stress with the ones at an on-center beam, because a target wire will be exposed to a higher peak beam current. In this paper, we introduced the peak beam current dependence of the bunch length waveforms, and an effect of on- /off-centering of the wire position. Finally the new buncher tuning method using one BSM have been discussed.

Journal Articles

Beam monitors for the commissioning of energy upgraded linac

Miura, Akihiko; Maruta, Tomofumi*; Liu, Y.*; Miyao, Tomoaki*; Kawane, Yusuke; Ouchi, Nobuo; Oguri, Hidetomo; Ikegami, Masanori*; Hasegawa, Kazuo

JPS Conference Proceedings (Internet), 8, p.011002_1 - 011002_6, 2015/09

BB2014-1017.pdf:0.51MB

In the J-PARC Linac, an energy upgrade project has started since 2009 using Annular-ring Coupled Structure cavities to achieve design beam power of 1 MW at the exit of the downstream rapid cycling synchrotron. Linac beam parameters of the upgraded Linac is drastically improved especially for the beam energy from 181 to 400 MeV in the project. To meet with the significant upgrades of the Linac, beam monitors to be used for the upgraded beam line are newly designed and fabricated as well as the beam monitor layout is designed with the consideration to the beam commissioning strategies. This paper introduces the beam monitor layout in the new beam line and the commissioning results to confirm the beam monitor functioning.

Journal Articles

Bunch shape measurement of 181 MeV beam in J-PARC linac

Miura, Akihiko; Feschenko, A. V.*; Mirzojan, A. N.*; Miyao, Tomoaki*; Ouchi, Nobuo; Maruta, Tomofumi*; Liu, Y.*; Oguri, Hidetomo; Ikegami, Masanori*; Hasegawa, Kazuo

JPS Conference Proceedings (Internet), 8, p.011003_1 - 011003_6, 2015/09

BB2014-1018.pdf:0.45MB

In J-PARC Linac, an energy upgrade project has started since 2009 using Annular-ring Coupled Structure (ACS) cavities. We have decided to use the bunch shape monitors (BSM) as the monitors of the longitudinal beam width measurement in order to take the longitudinal matching using two bunchers located in the upstream of ACS cavities, where the RF frequency jumps from 324 to 972 MHz. Three BSMs were completely fabricated and installed in the beam line. The BSMs were commissioned with the beam and their operability was demonstrated. We found the vacuum degradation during the measurement. We once removed all BSMs to have a vacuum conditioning and postponed the longitudinal matching at the establishment of 400-MeV operation of the energy upgraded Linac. In this paper, we introduce the mechanism of the BSM, its operability, the measurement results with the 181 MeV beam and consistency check with the respect cavity amplitude. We also describe the operational vacuum conditions and the outline of the improvement of the vacuum system for the BSMs.

Journal Articles

Beam loss mitigation by the modification of the beam pulse definition in the J-PARC LINAC

Sawabe, Yuki; Maruta, Tomofumi*; Liu, Y.*; Miura, Akihiko; Miyao, Tomoaki*; Ishiyama, Tatsuya; Kikuzawa, Nobuhiro; Hayashi, Naoki

Proceedings of 12th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1202 - 1205, 2015/09

no abstracts in English

Journal Articles

Recent progress of beam study in the J-PARC linac

Maruta, Tomofumi*; Liu, Y.*; Futatsukawa, Kenta*; Miyao, Tomoaki*; Miura, Akihiko; Ikegami, Masanori*

Proceedings of 12th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.432 - 436, 2015/09

no abstracts in English

Journal Articles

Twiss parameter matching of the injection beam for the J-PARC RCS

Okabe, Kota; Maruta, Tomofumi*; Hotchi, Hideaki; Saha, P. K.; Yoshimoto, Masahiro; Miura, Akihiko; Liu, Y.*; Kinsho, Michikazu

Proceedings of 12th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.933 - 937, 2015/09

In a high power proton accelerator such as the 3-GeV rapid cycle synchrotron (RCS), small ratio of the beam loss such as beam halo can cause serious radiation dose. The suppression of the transverse beam halo is a key issue to provide high intensity beam for routine user operation at the RCS. If the transverse twiss parameter of the injection beam is not matched to the RCS optics, it will generates beam halo during the multi-turn injection. In order to suppress such beam halo, twiss parameters and dispersion matching are performed at the RCS injection point. In the beam matching process, we use the rms envelope equation solver with space charge effect to predict high intensity beam behavior. The beam profile measurement is done with wire scanner monitors at the downstream of the L3BT as well as multi-wire profile monitors at the RCS injection section. In this presentation, we introduce the transverse twiss parameter matching scheme at the RCS injection points.

Journal Articles

Development of RF chopper system at J-PARC Linac, 2

Hirano, Koichiro; Kondo, Yasuhiro; Kawane, Yusuke; Shinozaki, Shinichi; Miura, Akihiko; Morishita, Takatoshi; Sawabe, Yuki; Sugimura, Takashi*; Naito, Fujio*; Fang, Z.*; et al.

Proceedings of 12th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.944 - 947, 2015/09

Two RF-deflecting cavities as a chopper and a beam scraper have been used in the MEBT1 between a 324 MHz RFQ and a 50-MeV DTL of the J-PARC Linac. We replaced with a newly fabricated RF chopper to decrease beam loss for the operation with 50 mA. We installed two new scrapers to absorb the higher power of the deflected beam by the RF chopper. This paper describes the RF chopper system and beam irradiation test results of the scraper.

Journal Articles

Preliminary studies of laser-assisted H$$^{-}$$ stripping at 400 MeV

Saha, P. K.; Harada, Hiroyuki; Kinsho, Michikazu; Maruta, Tomofumi*; Okabe, Kota; Yoshimoto, Masahiro; Irie, Yoshiro*; Gorlov, T.*

Proceedings of 6th International Particle Accelerator Conference (IPAC '15) (Internet), p.3795 - 3797, 2015/06

Journal Articles

Scintillating fiber detector for the beam loss proton measurements at J-PARC linac

Konstantinova, O.*; Sako, Hiroyuki; Maruta, Tomofumi*; Miura, Akihiko

Proceedings of Science (Internet), 8 Pages, 2015/05

The highest beam loss has been observed at the ACS (Annular Coupled Structure) section in the J-PARC linac. We have developed a scintillating fiber detector for beam loss proton measurements at J-PARC linac. It consists of 4 upstream fiber planes and 4 downstream fiber planes. The upstream and downstream planes are separated by 1.6 m for time-of-flight measurements. A charged particle which passes through the 8 planes are either a proton or an electron, which can be distinguished by time-of-flight. We measured the absolute proton beam loss rates of 1.8-3.2$$times$$10$$^{5}$$. The ratio of H$$^{+}$$/H$$^{-}$$ was 0.7-1.8$$times$$10$$^{-8}$$, which is closed to the estimated value of 2.7$$times$$10$$^{-8}$$ from residual gas pressure. The energy of protons was measured to be 80-120 MeV, which was consistent with the average simulated value of 90 MeV.

Journal Articles

Beam test of a new radio frequency quadrupole linac for the Japan Proton Accelerator Research Complex

Kondo, Yasuhiro; Morishita, Takatoshi; Yamazaki, Saishun; Hori, Toshihiko; Sawabe, Yuki; Chishiro, Etsuji; Fukuda, Shimpei; Hasegawa, Kazuo; Hirano, Koichiro; Kikuzawa, Nobuhiro; et al.

Physical Review Special Topics; Accelerators and Beams, 17(12), p.120101_1 - 120101_8, 2014/12

 Times Cited Count:5 Percentile:54.22(Physics, Nuclear)

We performed a beam test of a new radio frequency quadrupole linac (RFQ III) for the beam current upgrade of the Japan Proton Accelerator Research Complex. First, the conditioning of RFQ III was conducted, and after 20 h of conditioning, RFQ III became very stable with a nominal peak power and duty factor of 400 kW and 1.5%, respectively. An off-line beam test was subsequently conducted before installation in the accelerator tunnel. The transmission, transverse emittance, and energy spread of the 50-mA negative hydrogen beam from RFQ III were measured and compared with simulation results. The experiment and simulation results showed good agreement; therefore, we conclude that the performance of RFQ III conforms to its design.

Journal Articles

Installation and performance check of beam monitors for energy upgraded J-PARC linac

Miura, Akihiko; Ouchi, Nobuo; Oguri, Hidetomo; Hasegawa, Kazuo; Maruta, Tomofumi*; Liu, Y.*; Miyao, Tomoaki*; Ikegami, Masanori*

Proceedings of 27th International Linear Accelerator Conference (LINAC 2014) (Internet), p.1059 - 1061, 2014/12

An energy upgrade project has started in the J-PARC Linac since 2009. In the upgraded project, beam energy in the Linac has increased from original 181 MeV to 400 MeV using the additional 21 Annular-ring Coupled Structure Linac (ACS) cavities. The new beam monitors as the beam current monitors, the phase monitors, the beam position monitors and the transverse profile monitors (wire scanner monitors) were designed and fabricated. By the end of November, 2013, all beam monitors were completely installed. From the middle of December, we started the beam commissioning to achieve the beam energy as 400 MeV, as well as to confirm the beam monitor functioning. We achieved the 400 MeV beam acceleration at the middle of January, 2014 using newly installed beam monitors. This paper describes the beam monitor installation and the beam commissioning results of beam monitor functioning.

47 (Records 1-20 displayed on this page)