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beam with 3 MeV by the bunch-shape monitorKitamura, Ryo; Futatsukawa, Kenta*; Hayashi, Naoki; Hirano, Koichiro; Kondo, Yasuhiro; Kosaka, Satoshi*; Miyao, Tomoaki*; Nemoto, Yasuo*; Morishita, Takatoshi; Oguri, Hidetomo
JPS Conference Proceedings (Internet), 33, p.011012_1 - 011012_6, 2021/03
The new bunch shape monitor (BSM) is required to measure the bunch size of the high-intensity H beam with 3 MeV at the front-end section in the J-PARC linac. The carbon-nano tube wire and the graphene stick are good candidates for the target wire of the BSM, because these materials have the enough strength to detect the high-intensity beam. However, since the negative high voltage of more than a few kV should be applied to the wire in the BSM, the suppression of the discharge is the challenge to realize the new BSM. After the high-voltage test to investigate the effect of the discharge from the wire, the detection of the signal from the BSM was successful at the beam core with the peak current of 55 mA using the graphene stick. The preliminary result of the bunch-size measurement is reported in this presentation.
Morishita, Takatoshi
JPS Conference Proceedings (Internet), 33, p.011013_1 - 011013_6, 2021/03
A precise surveys and realignments have been performed in a long-term maintenance period in the J-PARC linac. In the recent years, the local settlement continues in the upstream section of the straight line. A realignment of about 1.5 mm is carried out approximately every three years. To connect the coordinate system while securing its accuracy, the horizontal measurement is performed with moving the tracker at short intervals, then, it takes time for the precise survey. Therefore, it is desirable that a long-distance horizontal linearity can be monitored or measured in a short period of time. A stretched wire is tested as a horizontal reference to assist the tracker survey and to obtain the long-range straightness in the linac tunnel. The survey and alignment results in these years, and the initial results of the horizontal monitoring for tunnel linearity will be presented.
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.
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：1 Percentile：53.97We 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.
Nakazawa, Yuga*; Iinuma, Hiromi*; Iwata, Yoshiyuki*; Iwashita, Yoshihisa*; Otani, Masashi*; Kawamura, Naritoshi*; Mibe, Tsutomu*; Yamazaki, Takayuki*; Yoshida, Mitsuhiro*; Kitamura, Ryo; et al.
Journal of Physics; Conference Series, 1350, p.012054_1 - 012054_7, 2019/12
Times Cited Count：4 Percentile：92.52An inter-digital H-mode drift-tube linac (IH-DTL) is developed in a muon linac at the J-PARC E34 experiment. IH-DTL will accelerate muons from 0.34 MeV to 4.5 MeV at a drive frequency of 324 MHz. Since IH-DTL adopts an APF method, with which the beam is focused in the transverse direction using the rf field only, the proper beam matching of the phase-space distribution is required before the injection into the IH-DTL. Thus, an IH-DTL prototype was fabricated to evaluate the performance of the cavity and beam transmission. As a preparation of the high-power test, tuners and coupler are designed and fabricated. In this paper, the development of the tuner and the coupler and the result of the low-power measurement will be presented.
Otani, Masashi*; Fukao, Yoshinori*; Futatsukawa, Kenta*; Kawamura, Naritoshi*; Matoba, Shiro*; Mibe, Tsutomu*; Miyake, Yasuhiro*; Shimomura, Koichiro*; Yamazaki, Takayuki*; Hasegawa, Kazuo; et al.
Journal of Physics; Conference Series, 1350, p.012067_1 - 012067_6, 2019/12
Times Cited Count：1 Percentile：53.97Negative muonium atom (
e
e, Mu) has unique features stimulating potential interesting for several scientific fields. Since its discovery in late 1980's in vacuum, it has been discussed that the production efficiency would be improved using a low-work function material. C12A7 was a well-known insulator as a constituent of alumina cement, but was recently confirmed to exhibit electric conductivity by electron doping. The C12A7 electride has relatively low-work function (2.9 eV). In this paper, the negative muonium production measurement with several materials including a C12A7 electride film will be presented. Measured production rate of the Mu were 10
/s for all the Al, electride, and SUS target. Significant enhancement on electride target was not observed, thus it is presumed that the surface condition should be more carefully treated. There was no material dependence of the Mu averaged energy: it was 0.2
0.1keV.
Otani, Masashi*; Futatsukawa, Kenta*; Mibe, Tsutomu*; Naito, Fujio*; Hasegawa, Kazuo; Ito, Takashi; Kitamura, Ryo; Kondo, Yasuhiro; Morishita, Takatoshi; Iinuma, Hiromi*; et al.
Journal of Physics; Conference Series, 1350, p.012097_1 - 012097_7, 2019/12
Times Cited Count：2 Percentile：76.59A disk and washer (DAW) coupled cavity linac (CCL) has been developed for a middle velocity part in a muon linac to measure muon anomalous magnetic moment and search for electric dipole moment. I will accelerate muons from 
= 
= 0.3 to 0.7 at an operational frequency of 1.3GHz. In this poster, the cavity design, beam dynamics design, and the cold-model measurements will be presented.
Tamura, Jun; Kondo, Yasuhiro; Morishita, Takatoshi; Naito, Fujio*; Otani, Masashi*; Nemoto, Yasuo*
Journal of Physics; Conference Series, 1350, p.012079_1 - 012079_6, 2019/12
Times Cited Count：0 Percentile：0.07In 2013, the Annular-ring Coupled Structure (ACS) cavities were installed to the Japan Proton Accelerator Research Complex (J-PARC) linac. Since then, the ACS cavities have been stably running. Although any serious problem induced by the RF window had not yet observed, we decided to replace the RF window of one ACS cavity by the newly manufactured one. The major motivations of the replacement are to check the surface condition of the RF window which have been under operation for nearly five years, to confirm that the new RF window fully meets specifications, and to learn how much time is required for high-power conditioning of the new RF window. By making use of the summer maintenance period of 2018, we carried out the replacement. This was the first experience for us to replace the RF window installed to the ACS cavity in the linac accelerator tunnel. As for the removed RF window, there was no any abnormal warning found with the visual examination. At the resuming of the cavity operation after the maintenance period, we conducted the high-power conditioning in a measured manner. It took around fifty hours so that the targeted peak power was stably input to the cavity through the new RF window. The ACS cavity with the new RF window is now stably operating.
Tamura, Jun; Kondo, Yasuhiro; Morishita, Takatoshi; Naito, Fujio*; Otani, Masashi*; Nemoto, Yasuo*
Journal of Physics; Conference Series, 1350, p.012080_1 - 012080_6, 2019/12
Times Cited Count：0 Percentile：0.07In the Japan Proton Accelerator Research Complex (J-PARC) linac, negative hydrogen beams are accelerated from 190 MeV to 400 MeV by Annular-ring Coupled Structure (ACS) cavities. The RF input coupler of the ACS21 cavity, which is the twenty-first (the last) accelerating cavity in the order of beam acceleration, had a comparatively larger Voltage Standing Wave Ratio (VSWR) value than the other ACS cavities. Therefore, we designed and manufactured a rectangular waveguide which has a capacitive iris to adjust the coupling factor of the ACS21 cavity. By making use of the summer maintenance period in 2018, we installed the newly manufactured waveguide to the cavity. Consequently, the VSWR of the ACS21 was successfully decreased to the target value which leads to the critical coupling under the nominal accelerating condition with 50-mA peak beam current.
Kondo, Yasuhiro; Morishita, Takatoshi; Jameson, R. A.*
Physical Review Accelerators and Beams (Internet), 22(12), p.120101_1 - 120101_8, 2019/12
Times Cited Count：7 Percentile：62.36(Physics, Nuclear)Radio frequency quadrupole linac (RFQ) is the key component which realized modern high-current proton linacs, however, many RFQs are designed based on very conventional design schemes. We developed 3-MeV 50-mA H (negative hydrogen) RFQ based on a beam space-charge physics concept. The equipartitioning scheme, which is widely used in the high intensity linac design, is implemented into the RFQ design. Design performances of 99.1% transmission, 0.24
mm mrad transverse normalized rms emittance, and 0.11 MeV deg for longitudinal direction are achieved with a vane length of 3 m and the final energy of 3 MeV. An RFQ employing this design concept was fabricated, and the design performance was confirmed by beam commissioning. In this paper, the design and result of the beam commissioning of this fully equipartitioned RFQ are described.
Kondo, Yasuhiro; Morishita, Takatoshi
JPS Conference Proceedings (Internet), 25, p.011030_1 - 011030_5, 2019/03
In this paper, we present the performance and RFQs at J-PARC. In the summer of 2014, we replaced the frontend system of the J-PARC linac for beam current upgrade. An RF driven ion source (IS) and a radio frequency quadrupole linac (RFQ III) are newly developed to make the linac be capable for 50 mA peak current operation. Prior to the installation to the accelerator tunnel, we conducted an off-line beam test at an RFQ test stand, and confirmed the basic performance of the IS and RFQ as their design. The 50 mA peak current was demonstrated at this test stand and we also succeeded the 50 mA operation in the actual linac. The used RFQ (RFQ I) replaced by RFQ III will be used for beam test of laser charge exchange system for the ADS project and beam scraper and so on. The other RFQ developed as a spare of RFQ I will be used for world first muon acceleration experiment. The status of these RFQs is also shown.
Kondo, Yasuhiro; Morishita, Takatoshi; Tamura, Jun; Otani, Masashi*
Proceedings of 29th International Linear Accelerator Conference (LINAC 2018) (Internet), p.794 - 797, 2019/01
A muon linac development for a new muon g-2 experiment is now going on at J-PARC. Muons from the muon beam line (H line) at the J-PARC muon science facility are once stopped in a silica-aerogel target, and room temperature muoniums are evaporated from the aerogel. They are dissociated with lasers, then accelerated up to 212 MeV using a linear accelerator. In the current reference design, a 324-MHz radio frequency quadrupole (RFQ) and an interdigital H-mode drift tube linac (IH-DTL) are used for the low beta acceleration. We propose a 1300 MHz (L band) RFQ instead of the 324 MHz RFQ and IH-DTL as an alternative to simplify the configuration of the muon linac. In this paper, the present status of the design and the measurement of a cold model of this world first L-band RFQ is described.
Nakazawa, Yuga*; Iinuma, Hiromi*; Iwata, Yoshiyuki*; Iwashita, Yoshihisa*; Otani, Masashi*; Kawamura, Naritoshi*; Mibe, Tsutomu*; Yamazaki, Takayuki*; Yoshida, Mitsuhiro*; Kitamura, Ryo*; et al.
Proceedings of 29th International Linear Accelerator Conference (LINAC 2018) (Internet), p.180 - 183, 2019/01
We have developed an Interdigital H-mode (IH) Drift-Tube Linac (DTL) design with an alternative phase focusing (APF) scheme for a muon linac, in order to measure the anomalous magnetic moment and electric dipole moment (EDM) of muons at the Japan Proton Accelerator Research Complex (J-PARC). The IH-DTL accelerates muons from beta 0.08 to 0.28 at an operational frequency of 324 MHz. The output beam emittances are calculated as 0.315 and 0.195 mm mrad in the horizontal and vertical directions, respectively, which satisfies the experimental requirement.
Tamura, Jun; Kondo, Yasuhiro; Morishita, Takatoshi; Ao, Hiroyuki*; Naito, Fujio*; Otani, Masashi*; Nemoto, Yasuo*
Journal of Physics; Conference Series, 1067(5), p.052009_1 - 052009_6, 2018/09
Times Cited Count：0 Percentile：0.11In the Japan Proton Accelerator Research Complex (J-PARC) linac, the Annular-ring Coupled Structure (ACS) cavities have been stably operating. To maintain this operation availability, we manufactured three pillbox-type RF windows for the ACS cavities in fiscal year 2015 and 2017. It is desirable to minimize the RF reflection of the RF window to prevent standing waves from exciting between the cavity and the RF window, and not to significantly change the optimized coupling factor between the cavity and the waveguide. To realize the minimization, the relative permittivities of the ceramic disks of the RF windows were evaluated by measuring the resonant frequencies of the pillbox cavity containing the ceramic disk. On the basis of the evaluated relative permittivities, the pillbox-part lengths of the RF windows were determined. The measured Voltage Standing Wave Ratios (VSWRs) of the manufactured RF windows are just about 1.08 and these are applicable for the practical use.
Bae, S.*; Choi, H.*; Choi, S.*; Fukao, Yoshinori*; Futatsukawa, Kenta*; Hasegawa, Kazuo; Iijima, Toru*; Iinuma, Hiromi*; Ishida, Katsuhiko*; Kawamura, Naritoshi*; et al.
Physical Review Accelerators and Beams (Internet), 21(5), p.050101_1 - 050101_6, 2018/05
Times Cited Count：15 Percentile：82.65(Physics, Nuclear)Muons have been accelerated by using a radio-frequency accelerator for the first time. Negative muonium atoms (Mu), which are bound states of positive muons and two electrons, are generated from through the electron capture process in an aluminum degrader. The generated Mu's are initially electrostatically accelerated and injected into a radio-frequency quadrupole linac (RFQ). In the RFQ, the Mu's are accelerated to 89 keV. The accelerated Mu's are identified by momentum measurement and time of flight. This compact muon linac opens the door to various muon accelerator applications including particle physics measurements and the construction of a transmission muon microscope.
Kitamura, Ryo*; Otani, Masashi*; Kondo, Yasuhiro; Bae, S.*; Choi, S.*; Fukao, Yoshinori*; Futatsukawa, Kenta*; Hasegawa, Kazuo; Iinuma, Hiromi*; Ishida, Katsuhiko*; et al.
Proceedings of 14th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.100 - 103, 2017/12
Muon acceleration is an important technique in exploring the new frontier of physics. A new measurement of the muon dipole moments is planned in J-PARC using the muon linear accelerator. The low-energy (LE) muon source using the thin metal foil target and beam diagnostic system were developed for the world's first muon acceleration. Negative muonium ions from the thin metal foil target as the LE muon source was successfully observed. Also the beam profile of the LE positive muon was measured by the LE-dedicated beam profile monitor. The muon acceleration test using a Radio-Frequency Quadrupole linac (RFQ) is being prepared as the first step of the muon accelerator development. In this paper, the latest status of the first muon acceleration test is described.
Morishita, Takatoshi; Kondo, Yasuhiro; Oguri, Hidetomo; Hasegawa, Kazuo
Journal of Vacuum Science and Technology A, 35(4), p.041602_1 - 041602_5, 2017/07
Times Cited Count：1 Percentile：5.6(Materials Science, Coatings & Films)In the J-PARC, the linac provides 400 MeV hydrogen negative ion beam to the following 3GeV synchrotron. For the beam current upgrade, the new radio-frequency quadrupole (RFQ) linac, in which the design peak beam current was increased from 30 to 50 mA, has been fabricated and installed in the beam line in summer 2014. The beam provision to users started in the beginning of November, 2014. Since then, the RFQ operates without serious problems for more than two years, however, the operation stability of the RFQ with beam acceleration was not enough due to the sparking in the cavity. We consider that the impurities in the vacuum chamber are related to this sparking phenomena. The design and performance of the RFQ vacuum system is described in this paper, then, the relationship among the sparking rates, the residual gas species in the vacuum chamber, and the beam operation parameters are described.
Ito, Takashi; Morishita, Takatoshi; Tamura, Jun; Nammo, Kesao*; Sugimura, Takashi*
Proceedings of 8th International Particle Accelerator Conference (IPAC '17) (Internet), p.4184 - 4186, 2017/06
We have suffered from multipactor problem of some SDTLs after the Great East Japan Earthquake. As a designed operating rf power of the SDTL is in the multipactor region, we had to operate at higher power of the designed one. From the result of the simulation and the observation of the SDTL cavity, it became clear that the multipactor occurred on the inner surface of the cavity. We think that one of the cause of the multifactor is the contamination on the inner surface of the cavity, we performed the cleaning of the inner surface of the cavity by using acetone. The cleaning was very effective and the multipactor region was reduced or disappeared. The multipactor problem has not occurred since then.
Kondo, Yasuhiro; Asano, Hiroyuki*; Chishiro, Etsuji; Hirano, Koichiro; Ishiyama, Tatsuya; Ito, Takashi; Kawane, Yusuke; Kikuzawa, Nobuhiro; Meigo, Shinichiro; Miura, Akihiko; et al.
Proceedings of 28th International Linear Accelerator Conference (LINAC 2016) (Internet), p.298 - 300, 2017/05
We have constructed a linac for development of various accelerator components at J-PARC. The ion source is same as the J-PARC linac's, and the RFQ is a used one in the J-PARC linac. The beam energy is 3 MeV and nominal beam current is 30 mA. The accelerator has been already commissioned, and the first development program, laser-charge-exchange experiment for the transmutation experimental facility, has been started. In this paper, present status of this 3-MeV linac is presented.
particles in MEBT2 chicane of J-PARC linacTamura, 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 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 particles, the new analysis line for the H 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 particles by using a carbon plated installed to a wire scanner monitor and indirectly detected the H particles by using a scintillation detector. We also confirmed that the signals change with vacuum condition in the SDTL section.
