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Journal Articles

Model magnet development of D1 beam separation dipole for the HL-LHC upgrade

Nakamoto, Tatsushi*; Sugano, Michinaka*; Xu, Q.*; Kawamata, Hiroshi*; Enomoto, Shun*; Higashi, Norio*; Idesaki, Akira; Iio, Masami*; Ikemoto, Yukio*; Iwasaki, Ruri*; et al.

IEEE Transactions on Applied Superconductivity, 25(3), p.4000505_1 - 4000505_5, 2015/06

 Times Cited Count:0 Percentile:0(Engineering, Electrical & Electronic)

Recently, development of superconducting magnet system with high radiation resistance has been demanded for application in accelerator facilities such as CERN LHC. In order to realize superconducting magnet system with high radiation resistance, it is necessary to develop electrical insulator with high radiation resistance because the electrical insulator is made of organic materials whose radiation resistance is inferior to that of inorganic materials. We developed a glass fiber reinforced plastic with bismaleimide-triazine resin. The developed material showed excellent radiation resistance; the material evolved gases of 5$$times$$10 $$^{-5}$$mol/g and maintained flexural strength of 640MPa (90% of initial value).

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:6 Percentile:43.07(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

High-power test and thermal characteristics of a new radio-frequency quadrupole cavity for the Japan Proton Accelerator Research Complex linac

Kondo, Yasuhiro; Morishita, Takatoshi; Hasegawa, Kazuo; Chishiro, Etsuji; Hirano, Koichiro; Hori, Toshihiko; Oguri, Hidetomo; Sato, Fumiaki; Shinozaki, Shinichi; Sugimura, Takashi*; et al.

Physical Review Special Topics; Accelerators and Beams, 16(4), p.040102_1 - 040102_8, 2013/04

 Times Cited Count:15 Percentile:68.41(Physics, Nuclear)

We performed a high-power test of a new radio-frequency quadrupole (RFQ II) for the J-PARC linac. RFQ II was developed as a spare RFQ because the operating J-PARC RFQ has suffered from a sparking problem. First, the conditioning of RFQ II was carried out; after 50 h of conditioning, RFQ II became very stable with a nominal power and duty of 330 kW and 3%, respectively. Next the thermal properties were measured because the resonant frequency of RFQ II is tuned by changing the temperature of the cooling water. The frequency response was measured and compared to finite-element method simulation results, confirming that the simple two-dimensional model reproduces the experimental data well. The differences in the field distribution with changes in the rf loading and the cooling-water temperature were also measured, and no serious field distortion was observed. Therefore, we conclude that RFQ II can perform well as a high-power rf cavity.

Journal Articles

Recent progress with the J-PARC RFQs

Kondo, Yasuhiro; Morishita, Takatoshi; Hasegawa, Kazuo; Kawamata, Hiroshi*; Sugimura, Takashi*; Naito, Fujio*

Proceedings of 26th International Linear Accelerator Conference (LINAC 2012) (Internet), p.972 - 974, 2012/09

In this paper, we will report recent topics about J-PARC RFQs. First, the operating RFQ (RFQ I) have been recovered from the long shutdown due to the earthquake. This RFQ have been suffered from breakdown problem since 2008, therefore we have been developing a back-up RFQ (RFQ II). In April 2012, the high power test was successfully performed. It was confirmed to be able to stably operate at nominal power and duty factor (333 kW and 3%). Finally, we are fabricating a new RFQ for the beam-current upgrade of the J-PARC linac (RFQ III). The brazing of the first unit will be done in this September. The status of these RFQs are described.

Journal Articles

On-machine non-contact dimension-measurement system with laser displacement sensor for vane-tip machining of RFQs

Kondo, Yasuhiro; Hasegawa, Kazuo; Kawamata, Hiroshi*; Morishita, Takatoshi; Naito, Fujio*

Nuclear Instruments and Methods in Physics Research A, 667, p.5 - 10, 2012/03

 Times Cited Count:13 Percentile:69.15(Instruments & Instrumentation)

We have developed a new on-machine non-contact dimension-measurement system using a laser displacement sensor (LDS) for machining the vane tips of RFQs. The LDS was attached to a milling machine, and the dimensions of a test piece (TP) with a modulated vane tip were measured to evaluate the performance of the system. A longitudinal profile was measured with the LDS and it was compared with the profile measured with a coordinate measuring machine (CMM). A transverse profile was also measured. The required accuracy of dimension measurement was achieved using our system.

Journal Articles

Vacuum brazing of the new RFQ for the J-PARC linac

Morishita, Takatoshi; Kondo, Yasuhiro; Hasegawa, Kazuo; Naito, Fujio*; Yoshioka, Masakazu*; Matsumoto, Hiroshi*; Hori, Yoichiro*; Kawamata, Hiroshi*; Saito, Yoshio*; Baba, Hiroshi*

Proceedings of 25th International Linear Accelerator Conference (LINAC 2010) (CD-ROM), p.521 - 523, 2010/09

The fabrication of a new RFQ has been started as a backup machine for the J-PARC linac. The RFQ cavity is divided by three unit tanks in the longitudinal direction. The unit tank consists of two major vanes and two minor vanes, those are brazed together. A one-step vacuum brazing of a unit tank was adopted to unite these four vanes together with the flanges and ports. At the first tank brazing, the vacuum leak has been occurred due to the non-uniform temperature rise during the heating. Repair of this leakage and the results of the improved brazing of the second tank are reported.

Journal Articles

Vane machining by the ball-end-mill for the new RFQ in the J-PARC linac

Morishita, Takatoshi; Kondo, Yasuhiro; Hasegawa, Kazuo; Kawamata, Hiroshi*; Naito, Fujio*; Yoshioka, Masakazu*; Matsumoto, Hiroshi*; Hori, Yoichiro*; Saito, Yoshio*; Baba, Hiroshi*

Proceedings of 25th International Linear Accelerator Conference (LINAC 2010) (CD-ROM), p.518 - 520, 2010/09

The fabrication of a new RFQ has been started in the J-PARC linac. The RFQ cavity is divided by three unit tanks in the longitudinal direction. The unit tank consists of two major vanes and two minor vanes, those will be brazed together. To reduce the costs and periods to develop the special formed bite for the modulation machining, a numerical controlled machining using a conventional ball-end-mill was adopted for the vane modulation cutting instead of the wheel shape cutter. The dimension accuracy was confirmed by cutting test pieces. Moreover, the obtained surface seems smooth enough for the operation. Results of the ball-end-mill machining for the vanes are described.

Journal Articles

Fabrication of the new RFQ for the J-PARC linac

Morishita, Takatoshi; Kondo, Yasuhiro; Hasegawa, Kazuo; Naito, Fujio*; Yoshioka, Masakazu*; Matsumoto, Hiroshi*; Hori, Yoichiro*; Kawamata, Hiroshi*; Saito, Yoshio*; Baba, Hiroshi*

Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.783 - 785, 2010/05

The J-PARC RFQ (length 3.1 m, 4-vane type, 324 MHz) accelerates a negative hydrogen beam from 0.05 MeV to 3 MeV toward the following DTL. The stability of the operating RFQ decreased for a few months at the end of 2008, then, we started a preparation of a new RFQ as a backup machine in the case of RFQ problem. The beam dynamics design of the new RFQ is the same as the current cavity for a quick resumption of operation, however, the engineering and RF designs are changed to improve stability. The processes of the vane machining and the surface treatments have been carefully considered to reduce the discharge problem. The vacuum brazing technique has been chosen for vane jointing. The design of the new RFQ and the fabrication progress is descried in this proceeding.

Journal Articles

Engineering design of RFQ at J-PARC linac

Morishita, Takatoshi; Kondo, Yasuhiro; Hasegawa, Kazuo; Naito, Fujio*; Yoshioka, Masakazu*; Matsumoto, Hiroshi*; Hori, Yoichiro*; Kawamata, Hiroshi*; Saito, Yoshio*; Baba, Hiroshi*; et al.

Proceedings of 6th Annual Meeting of Particle Accelerator Society of Japan (CD-ROM), p.1047 - 1049, 2010/03

The beam commissioning of J-PARC linac has been started since November 2006. After the scheduled shutdown in summer 2007, the beam is successfully delivered from the linac to the RCS. Since then, a stable beam provision was emphasized. However, the trip in the RFQ was increased at the end of Sept. 2008, then, the stability of the beam operation decreased. To improve this situation, we started to prepare a new RFQ cavity as a backup machine. The basic concept of the engineering design is the simplicity and the effective vacuum pumping aiming at the stable operation. A 3m long cavity is divided into 3 modules longitudinally. A numerical control machining with ball-end mill is chosen for a vane machining. Four vanes are vacuum brazed each other after machining. Each modules are aligned on the platform using a linear motion guide. A basic design of the key components on machining and brazing are described in this proceeding.

Journal Articles

Status of the J-PARC RFQ

Hasegawa, Kazuo; Morishita, Takatoshi; Kondo, Yasuhiro; Oguri, Hidetomo; Kobayashi, Tetsuya; Naito, Fujio*; Yoshioka, Masakazu*; Matsumoto, Hiroshi*; Kawamata, Hiroshi*; Hori, Yoichiro*; et al.

Proceedings of 6th Annual Meeting of Particle Accelerator Society of Japan (CD-ROM), p.693 - 695, 2010/03

The J-PARC RFQ (length 3.1m, 4-vane type, 324 MHz) accelerates a beam from the ion source to the DTL. The beam test of the linac was started in November 2006 and 181 MeV beam was successfully accelerated in January 2007. Since then, the linac has been delivered beams for commissioning of the linac itself, downstream accelerators and facilities. Trip rates of the RFQ, however, suddenly increased in Autumn 2008, and we are suffering from this issue for user run operation. We tried to recover by tender conditioning, modification of RF control, improvement of vacuum and so on. We manage to have beam operation. In this report, we describe the status of the RFQ.

Oral presentation

Development of new RFQs for J-PARC

Morishita, Takatoshi; Kondo, Yasuhiro; Hasegawa, Kazuo; Sugimura, Takashi*; Kawamata, Hiroshi*; Naito, Fujio*

no journal, , 

In the J-PARC linac, a new RFQ is designed for higher current (50 mA) operation and we started a fabrication last year. The 3.6m RFQ cavity is divided into three unit tanks in the longitudinal direction. Each unit tank consists of four vanes which are brazed together. To reduce the cost and time required to develop a special formed bite for the vane modulation machining, a numerical controlled machine using a conventional ball-end-mill was adopted for the vane modulation cutting instead of a generally used wheel shaped cutter. To reduce a breakdown risk at the operation, the smoothness is important at the modulation surface. By the ball-end-mill machining, the smoothness is also improved. In addition, the surface is chemically polished after the machining to improve the smoothness.

Oral presentation

Fabrication and operating stability of the RFQs in J-PARC

Morishita, Takatoshi; Kondo, Yasuhiro; Oguri, Hidetomo; Hasegawa, Kazuo; Kawamata, Hiroshi*; Naito, Fujio*; Sugimura, Takashi*

no journal, , 

The new RFQ (Radio Frequency quadrupole) linac, in which the peak current of the beam dynamics design was increased from 30 mA to 50 mA for the beam current upgrade, has been fabricated and has high-power tested in April 2013 at the test bench in the J-PARC. The high-power conditioning reached to 1.2 times larger power than that of the nominal value within 24 hours. Then, this RFQ has been installed in the front end of the J-PARC linac to realize 1MW operation at RCS. The trip rate of the RFQ cavity depends on the beam operation parameter, however, the decrease in the beam availability is around 1 %. The properties of the J-PARC RFQs, fabrication processes in detail, and the stability in the beam operation will be presented.

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