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Journal Articles

Simulation of phase modulation for longitudinal emittance blow-up in J-PARC MR

Yamamoto, Masanobu; Ezura, Eiji*; Hara, Keigo*; Hasegawa, Katsushi*; Nomura, Masahiro; Omori, Chihiro*; Schnase, A.*; Shimada, Taihei; Takagi, Akira*; Takata, Koji*; et al.

JPS Conference Proceedings (Internet), 8, p.012015_1 - 012015_6, 2015/09

The J-PARC MR provides a coasting proton beam for nuclear physics experiments by slow extraction. The longitudinal emittance should be enlarged until the MR flat top to mitigate the microwave instability. We have investigated a Phase Modulation (PM) method by using a High Frequency Cavity (HFC) to increase the emittance. We have performed extensive simulation studies to find the appropriate parameters of the PM through the particle tracking simulation. We found that the effective HFC frequency has linear dependence with the PM frequency, where the emittance is smoothly enlarged. Furthermore, we found that the required HFC voltage is inverse proportional to the square root of the duration time of the PM. These PM properties will be used for the design of the HFC. We describe the particle tracking simulation results of controlled emittance blow-up by the PM.

Journal Articles

Ribbon thickness dependence of the magnetic alloy core characteristics in the accelerating frequency region of the J-PARC synchrotrons

Nomura, Masahiro; Shimada, Taihei; Tamura, Fumihiko; Yamamoto, Masanobu; Hara, Keigo*; Hasegawa, Katsushi*; Omori, Chihiro*; Takata, Koji*; Toda, Makoto*; Yoshii, Masahito*; et al.

Nuclear Instruments and Methods in Physics Research A, 749, p.84 - 89, 2014/06

 Times Cited Count:1 Percentile:11.75(Instruments & Instrumentation)

We have been developing high shunt impedance Magnetic Alloy (MA) cores. The MA core shunt impedance is a key parameter to achieve a higher field gradient for increasing a beam power. We increase the MA core shunt impedance by two different ways. One way is applying an external magnetic field during annealing to increase the MA core magnetic properties. The other way is using thinner ribbons to reduce the eddy current. In this paper, we discuss the latter way.

Journal Articles

Simulation of controlled longitudinal emittance blow-up in J-PARC RCS

Yamamoto, Masanobu; Nomura, Masahiro; Schnase, A.; Shimada, Taihei; Tamura, Fumihiko; Ezura, Eiji*; Hara, Keigo*; Hasegawa, Katsushi*; Omori, Chihiro*; Takagi, Akira*; et al.

Proceedings of 3rd International Particle Accelerator Conference (IPAC '12) (Internet), p.2952 - 2954, 2012/05

In J-PARC RCS, the high intensity beam is delivered to the MR. The longitudinal beam emittance at the RCS extraction should be optimized to avoid the beam loss after the MR injection. In order to match the longitudinal emittance shape between the RCS and the MR, it is desirable to enlarge the longitudinal emittance during the RCS acceleration. We have performed the particle tracking simulation for the controlled longitudinal emittance blow up in the RCS.

Journal Articles

Condition of MA cut cores in the RF cavities of J-PARC main ring after several years of operation

Nomura, Masahiro; Schnase, A.; Shimada, Taihei; Tamura, Fumihiko; Yamamoto, Masanobu; Sato, Tomonori; Yamamoto, Masahiro; Ezura, Eiji*; Hara, Keigo*; Hasegawa, Katsushi*; et al.

Proceedings of 2nd International Particle Accelerator Conference (IPAC 2011) (Internet), p.107 - 109, 2011/09

J-PARC 3 GeV Rapid Cycling Synchrotron (RCS) and 50 GeV Synchrotron (MR) employ the Magnetic Alloy (MA) loaded RF cavities. We observed the impedance reductions of MR RF cavities. Opening the RF cavities, we found that the impedance reductions were caused by the corrosion on the core cutting surfaces. The copper ions in the cooling water from hollow conductors of main magnets might accelerate the corrosion process.

Journal Articles

Condition of MA cores in the RF cavities of J-PARC synchrotrons after several years of operation

Nomura, Masahiro; Schnase, A.; Shimada, Taihei; Suzuki, Hiromitsu; Tamura, Fumihiko; Yamamoto, Masanobu; Ezura, Eiji*; Omori, Chihiro*; Hara, Keigo*; Hasegawa, Katsushi*; et al.

Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.3723 - 3725, 2010/05

We have been operating the RF cavities loaded with MA cores with a high field gradient of more than 20 kV/m since October 2007. We have been measuring the RF cavity impedance at the shutdown periods, and we detected the impedance reductions of RCS RF cavities on January and June 2009. Taking out the RF cavities from the beam line and opening them, we found that many of cores showed a buckling at the inner radius. We report the detail of condition of MA cores and the relation between the impedance reduction and core condition.

Journal Articles

Simulation of longitudinal emittance control in J-PARC RCS

Yamamoto, Masanobu; Nomura, Masahiro; Schnase, A.; Shimada, Taihei; Tamura, Fumihiko; Ezura, Eiji*; Hara, Keigo*; Hasegawa, Katsushi*; Omori, Chihiro*; Takagi, Akira*; et al.

Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.1940 - 1942, 2010/05

The beam commissioning and user operation have been going at the J-PARC RCS. Some Longitudinal beam gymnastics and the acceleration has been successfully performed under the high intensity operation. We have developed the longitudinal particle tracking code with the beam loading and the space charge effects to evaluate the longitudinal beam emittance. We describe the relation between the acceleration voltage pattern and the beam emittance in the dual harmonic rf and the high intensity operation.

Journal Articles

Core buckling position measurement for J-PARC RCS cavity

Schnase, A.; Omori, Chihiro*; Tamura, Fumihiko; Ezura, Eiji*; Hara, Keigo*; Hasegawa, Katsushi*; Nomura, Masahiro; Shimada, Taihei; Suzuki, Hiromitsu; Takagi, Akira*; et al.

Proceedings of 6th Annual Meeting of Particle Accelerator Society of Japan (CD-ROM), p.1077 - 1079, 2010/03

Journal Articles

Measurement of thermal deformation of magnetic alloys cores for RF cavities

Shimada, Taihei; Yamamoto, Masanobu; Suzuki, Hiromitsu; Toda, Makoto*; Hasegawa, Katsushi*; Omori, Chihiro*; Tamura, Fumihiko; Schnase, A.; Hara, Keigo*; Nomura, Masahiro; et al.

Proceedings of 6th Annual Meeting of Particle Accelerator Society of Japan (CD-ROM), p.1080 - 1082, 2010/03

Few magnetic alloys cores of the RF cavities which are installed in the 3 GeV rapid cycling synchrotron of the J-PARC have buckled after the operation of about two years. We heated cores in the air and measured thermal deformation in order to get information about the buckling process. We report the results.

Journal Articles

Cavity voltage calibration for J-PARC Ring RF

Schnase, A.; Ezura, Eiji*; Hara, Keigo*; Hasegawa, Katsushi; Nomura, Masahiro; Omori, Chihiro*; Shimada, Taihei; Suzuki, Hiromitsu; Takagi, Akira*; Tamura, Fumihiko; et al.

Proceedings of 5th Annual Meeting of Particle Accelerator Society of Japan and 33rd Linear Accelerator Meeting in Japan (CD-ROM), p.340 - 342, 2008/00

Journal Articles

Longitudinal particle simulation for J-PARC RCS

Yamamoto, Masanobu; Anami, Shozo*; Ezura, Eiji*; Hasegawa, Katsushi; Hara, Keigo*; Horino, Mitsuyoshi*; Nomura, Masahiro; Omori, Chihiro*; Schnase, A.; Shimada, Taihei; et al.

Proceedings of 5th Annual Meeting of Particle Accelerator Society of Japan and 33rd Linear Accelerator Meeting in Japan (CD-ROM), p.358 - 360, 2008/00

The beam commissioning has been started at the J-PARC RCS in October 2007, and the beam acceleration and the extraction at 3 GeV has been succeeded. Some longitudinal bunch gymnastics has been tested toward the high intensity operation, one of the issues is arriviating the space charge effect at the injeciton. Since the multi-turn injection scheme is employed at the RCS, the electric charge density of the bunch near the center of the RF bucket tends to be high with only normal fundamental RF capture. Some schemes such as adding 2nd higher harmonic RF, the momentum offset and the phase offset of the 2nd one are simulated by longitudinal particle tracking code to make the bunching factor low. The comparison between the beam test result and the particle tracking simulation is described.

Journal Articles

An Improved fast neutron radiography quantitative measurement method

Matsubayashi, Masahito; Hibiki, Takashi*; Mishima, Kaichiro*; Yoshii, Koji*; Okamoto, Koji*

Nuclear Instruments and Methods in Physics Research A, 533(3), p.481 - 490, 2004/11

 Times Cited Count:3 Percentile:25.71(Instruments & Instrumentation)

The validity of a fast neutron radiography quantification method, the $$Sigma$$-scaling method, which was originally proposed for thermal neutron radiography was examined with Monte Carlo calculations and experiments conducted at the YAYOI fast neutron source reactor. Water and copper were selected as comparative samples for a thermal neutron radiography case and a dense object, respectively. Although different characteristics on effective macroscopic cross-sections were implied by the simulation, the $$Sigma$$-scaled experimental results with the fission neutron spectrum cross-sections were well fitted to the measurements for both the water and copper samples. This indicates that the $$Sigma$$-scaling method could be successfully adopted for quantitative measurements in fast neutron radiography.

Journal Articles

Energetic protons from a few-micron metallic foil evaporated by an intense laser pulse

Matsukado, Koji*; Esirkepov, T. Z.; Kinoshita, Kenichi*; Daido, Hiroyuki; Utsumi, Takayuki*; Li, Z.*; Fukumi, Atsushi*; Hayashi, Yukio; Orimo, Satoshi; Nishiuchi, Mamiko; et al.

Physical Review Letters, 91(21), p.215001_1 - 215001_4, 2003/11

 Times Cited Count:134 Percentile:95.57(Physics, Multidisciplinary)

no abstracts in English

Journal Articles

Development of a fast neutron radiography converter using wavelength-shifting fibers

Matsubayashi, Masahito; Hibiki, Takashi*; Mishima, Kaichiro*; Yoshii, Koji*; Okamoto, Koji*

Nuclear Instruments and Methods in Physics Research A, 510(3), p.325 - 333, 2003/09

 Times Cited Count:9 Percentile:55.15(Instruments & Instrumentation)

A fluorescent converter for fast neutron radiography (FNR) comprising a scintillator and hydrogen-rich resin has been developed and applied to electronic imaging. The rate of the reaction between fast neutrons and the converter is increased by thickening the converter, but its opaqueness attenuates emitted light photons before they reach its surface. To improve the luminosity of a fluorescent converter for FNR, a novel type of converter was designed in which wavelength-shifting fibers were adopted to transport radiated light to the observation end face. The performance of the converter was compared with that of a polypropylene-based fluorescent converter in an experiment conducted at the fast-neutron-source reactor YAYOI in the University of Tokyo.

Journal Articles

High-resolution resonance photoemission study of Ce$$MX$$ ($$M$$=Pt, Pd; $$X$$=P, As, Sb)

Iwasaki, T.*; Sekiyama, Akira*; Yamasaki, Atsushi*; Okazaki, Makoto*; Kadono, Koji*; Utsunomiya, Hiroshi*; Imada, Shin*; Saito, Yuji; Muro, Takayuki*; Matsushita, Tomohiro*; et al.

Physical Review B, 65(19), p.195109_1 - 195109_9, 2002/05

 Times Cited Count:23 Percentile:72.01(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Preliminary examination of the applicability of imaging plates to fast neutron radiography

Matsubayashi, Masahito; Hibiki, Takashi*; Mishima, Kaichiro*; Yoshii, Koji*; Okamoto, Koji*

Nuclear Instruments and Methods in Physics Research A, 463(1-2), p.324 - 330, 2001/05

 Times Cited Count:16 Percentile:74.78(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Compact X-ray sources by intense laser interactions with beams and plasmas

Kotaki, Hideyuki; Kando, Masaki; Dewa, Hidenori; Kondo, Shuji; Watanabe, Takahiro*; Ueda, Toru*; Kinoshita, Kenichi*; Yoshii, Koji*; Uesaka, Mitsuru*; Nakajima, Kazuhisa

Nuclear Instruments and Methods in Physics Research A, 455(1), p.166 - 171, 2000/11

 Times Cited Count:12 Percentile:63.79(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Generation and application of femtosecond X-ray pulse

Uesaka, Mitsuru*; Kotaki, Hideyuki; Nakajima, Kazuhisa; Harano, Hideki*; Kinoshita, Kenichi*; Watanabe, Takahiro*; Ueda, Toru*; Yoshii, Koji*; Kando, Masaki; Dewa, Hidenori; et al.

Nuclear Instruments and Methods in Physics Research A, 455(1), p.90 - 98, 2000/11

 Times Cited Count:36 Percentile:90(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Experimental verification of laser photocathode RF gun as an injector for a laser plasma accelerator

Uesaka, Mitsuru*; Kinoshita, Kenichi*; Watanabe, Takahiro*; Sugahara, Jun*; Ueda, Toru*; Yoshii, Koji*; Kobayashi, Tetsuya*; Halz, N.*; Nakajima, Kazuhisa; Sakai, Fumio*; et al.

IEEE Transactions on Plasma Science, 28(4), p.1133 - 1142, 2000/08

 Times Cited Count:14 Percentile:43.45(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Development of fast neutron radiography imaging technique using imaging plate

Matsubayashi, Masahito; Yoshii, Koji*; Hibiki, Takashi*; Mishima, Kaichiro*

Kashika Joho Gakkai-Shi, 20(Suppl.1), p.325 - 328, 2000/07

no abstracts in English

Journal Articles

Generation, diagnosis and application of femtosecond electron single bunch

Uesaka, Mitsuru*; Watanabe, Takahiro*; Kinoshita, Kenichi*; Sugahara, Jun*; Harano, Hideki*; Ueda, Toru*; Yoshii, Koji*; Nakajima, Kazuhisa; Sakai, Fumio*; Kotaki, Hideyuki; et al.

Nihon Genshiryoku Gakkai-Shi, 42(4), p.310 - 324, 2000/04

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

no abstracts in English

30 (Records 1-20 displayed on this page)