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Chimura, Motoki; Harada, Hiroyuki; Kinsho, Michikazu
Progress of Theoretical and Experimental Physics (Internet), 2022(6), p.063G01_1 - 063G01_26, 2022/06
Times Cited Count：1 Percentile：26.42(Physics, Multidisciplinary)In the low-energy region of a high-intensity ion linac, a strong space-charge field causes a rapid beam emittance growth over a short distance of only few meters. The beam emittance growth leads to a beam loss and the machine activation raising a serious issue for regular maintenance of the accelerator component and beam power ramp up. In this work, we studied the mechanism of beam emittance growth due to the space-charge field based on three-dimensional particle-tracking simulation and theoretical considerations. Numerical simulations done for the high-intensity linac at J-PARC shows that the nonlinear terms in the space-charge field directly cause a beam emittance growth and beam halo formation. Then, we also propose a method to mitigate the beam emittance growth by using an octupole magnetic field, which arises as one of the nonlinear terms in the space-charge field. By applying this method in the simulation, we have succeeded mitigating the beam emittance growth.
Okabe, Kota; Liu, Y.*; Otani, Masashi*; Moriya, Katsuhiro; Shibata, Takanori*; Chimura, Motoki*; Hirano, Koichiro; Oguri, Hidetomo; Kinsho, Michikazu
JPS Conference Proceedings (Internet), 33, p.011011_1 - 011011_6, 2021/03
To realize more stable operation of the J-PARC accelerators, we have a re-design plan of an MEBT1 (Medium Energy Beam Transport). At the J-PARC Linac, the MEBT1 has transverse and longitudinal beam matching section for the DTLs. However there are some locally activated spots in DTL area at the current beam power level. To reduce beam loss during a beam acceleration at the DTLs is a most important task for a stable user operation. The first thing we should do is investigation a connection between beam quality in the MEBT1 and parameters of the upstream hardware. In this presentation, we will report a high intensity beam study results at the MEBT1.
Chimura, Motoki*; Harada, Hiroyuki; Moriya, Katsuhiro; Okabe, Kota; Kinsho, Michikazu
Proceedings of 16th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.728 - 732, 2019/07
The increase of space charge effect in high intensity beam causes the increase of the beam-loss. Beam loss limits beam intensity for accelerator equipment activation. Therefore, it is important to suppress the emittance growth due to the space charge effect. I focused on the low energy region in the linac where the space charge effect becomes remarkable. In order to identify the origin of the emittance growth due to the effect, a simulation was performed with a 3-D particle-in-cell simulation code, and evaluated the influence of the effects in the J-PARC medium energy beam transport line (MEBT1) entrance to DTL exit. As a result, it was confirmed that distortion of phase space distribution occurred due to nonlinear space charge force and that leading to emittance growth. I proposed to suppress the emittance growth by using an octupole magnet that gives nonlinear force to the beam. We report the new method and simulation results.
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.
Laird, J. S.; Hirao, Toshio; Onoda, Shinobu; Ito, Hisayoshi
IEEE Transactions on Nuclear Science, 52(5), p.1504 - 1512, 2005/10
Times Cited Count：7 Percentile：44.84(Engineering, Electrical & Electronic)no abstracts in English
Laird, J. S.; Hirao, Toshio; Onoda, Shinobu; Wakasa, Takeshi; Yamakawa, Takeshi; Abe, Hiroshi; Kamiya, Tomihiro; Ito, Hisayoshi
Proceedings of the 6th International Workshop on Radiation Effects on Semiconductor Devices for Space Application (RASEDA-6), p.125 - 129, 2004/10
no abstracts in English
Ikegami, Masanori
Nuclear Instruments and Methods in Physics Research A, 454(2-3), p.289 - 298, 2000/11
Times Cited Count：2 Percentile：26.91(Instruments & Instrumentation)no abstracts in English
Morimoto, Iwao; Kishiro, Junichi*; Takayama, Ken*; Zheng, X.; Maebara, Sunao; Shiho, Makoto
JAERI-Research 2000-008, p.59 - 0, 2000/02
JAERI-Research-2000-008.pdf:3.83MB
no abstracts in English
Ikegami, Masanori; Machida, Shinji*; Uesugi, Tomonori*
Physical Review Special Topics; Accelerators and Beams, p.124201_1 - 124201_10, 1999/12
no abstracts in English
Noda, Fumiaki*; Kinsho, Michikazu
JAERI-Research 99-019, 64 Pages, 1999/03
JAERI-Research-99-019.pdf:1.83MB
no abstracts in English
Ikegami, Masanori*
Physical Review E, 59(2), p.2330 - 2338, 1999/02
Times Cited Count：26 Percentile：69.92(Physics, Fluids & Plasmas)no abstracts in English
Ikegami, Masanori*
Nuclear Instruments and Methods in Physics Research A, 435(3), p.284 - 296, 1999/00
Times Cited Count：10 Percentile：60.61(Instruments & Instrumentation)no abstracts in English
Machida, Shinji*; Ikegami, Masanori
Proceedings of 6th European Particle Accelerator Conference (EPAC98) (CD-ROM), p.282 - 284, 1998/01
no abstracts in English
Ikegami, Masanori*; Mizumoto, Motoharu
Proc. of XIX Int. Linac Conf. (LINAC98), 2, p.821 - 823, 1998/00
no abstracts in English
Machida, Shinji*; Ikegami, Masanori*
Workshop on Space Charge Physics in High Intensity Hadron Rings, p.73 - 84, 1998/00
no abstracts in English
Noda, Fumiaki*; Kinsho, Michikazu; Kusano, Joichi; Mizumoto, Motoharu
Proc. of 11th Symp. on Accelerator Sci. and Technol., p.350 - 352, 1997/00
no abstracts in English
Okabe, Kota
no journal, ,
In the Japan Proton Accelerator Research Complex (J-PARC) 3-GeV rapid cycle synchrotron (RCS), supression of the transverse beam halo for the injected beam int the RCS is required to increase the output beam power. Transverse beam matching of the injection beam at the Linac-RCS beam transport line (L3BT) is one of the most useful method to reduce a beam loss in the RCS. Results of the beam commissioning for high intensity operation at the RCS, beam loss in the RCS and halo compornent of the extracted beam from the RCS ware supressed by the transverce matching methd. In this presentation, we will report the injection beam matching method at the L3BT and discuss the space charge phenomena about the high intensity beam.
Chimura, Motoki; Harada, Hiroyuki; Moriya, Katsuhiro; Okabe, Kota; Kinsho, Michikazu
no journal, ,
Beam intensity in a high-intensity proton accelerator is an important parameter in user experimental facilities. Beam emittance growth and beam loss due to space charge effect make a limit of beam power from the view point of high activation at devices. In order to identify the source of beam emittance growth due to space charge effect, we performed beam simulation by using a model of J-PARC Linac. As the result, nonlinear component of space charge force causes a strain of beam distribution and emittance growth. We proposed a new method for suppression of the nonlinear component by using multipole magnet and simulated the method in our model. As the result, we indicated that the growth is suppressed by using the nonlinear field. In my presentation, we report the new method and simulation results.
Chimura, Motoki; Harada, Hiroyuki; Moriya, Katsuhiro; Okabe, Kota; Kinsho, Michikazu
no journal, ,
High intensity beam also increases the beam loss, which originates from the space charge effect, so that the intensity is limited from the maintenance point of view. In the early acceleration region where the space charge field is very strong, its nonlinearity causes a rapid emittance increase over a short distance. Although this emittance growth has a small effect on the activation at that point, it causes an increase in the beam loss after that point. In this study, we propose a new method to suppress this emittance growth by compensating the nonlinear term of the space charge field by inducing a nonlinear octupole magnetic field, and perform a beam simulation of the J-PARC linac model using the IMPACT. As a result, it was confirmed that the expansion of the beam distribution in the outer core and the beam loss was suppressed. In this presentation, the results of the space charge compensation will be reported and the experimental plan will be discussed.
Chimura, Motoki; Harada, Hiroyuki; Takayanagi, Tomohiro; Kinsho, Michikazu
no journal, ,
In low-energy regions where space-charge fields become pronounced, such as in high-intensity proton accelerators, beam quality deteriorates rapidly over short distances of a few meters. Simulations in the 3 MeV beam transport line of the J-PARC linac show that the emittance increases by more than 50% at a short distance of 3 m. Therefore, we proposed a method to compensate a space charge force by using an octupole magnetic field and showed that the emittance increase can be suppressed from the simulation. We have developed a new coupled magnet to realize a higher quality and intensity beam by applying this method to an actual accelerator. In this talk, we will report the design and beam simulation results of the new coupled magnets that can generate quadrupole and octupole magnetic fields simultaneously.
