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Title |
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| MOPCH118 |
Wideband Low-output-impedance RF System for the Second Harmonic Cavity in the ISIS Synchrotron
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321 |
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- Y. Irie
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
- D. Bayley, G.M. Cross, I.S.K. Gardner, M.G. Glover, D. Jenkins, A. Morris, A. Seville, S.P. Stoneham, J.W.G. Thomason, T. Western
CCLRC/RAL/ISIS, Chilton, Didcot, Oxon
- J.C. Dooling, D. Horan, R. Kustom, M.E. Middendorf, G. Pile
ANL, Argonne, Illinois
- S. Fukumoto, M. Muto, T. Oki, A. Takagi, S. Takano
KEK, Ibaraki
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Wideband low-output-impedance RF system for the second harmonic cavity in the ISIS synchrotron has been developed by the collaboration between Argonne National Laboratory, US, KEK, Japan and Rutherford Appleton Laboratory, UK. Low output impedance is realized by the feedback from plate output to grid input of the final triode amplifier, resulting in less than 30 ohms over the frequency range of 2.7 - 6.2 MHz which is required for the second harmonic cavity. The vacuum tubes in the driver and final stages are both operated in class A, and a grid bias switching system is used on each tube to avoid unnecessary plate dissipations during a non-acceleration cycle. High power test was performed with a ferrite-loaded second harmonic cavity, where the bias current was swept at 50 Hz repetition rate. The maximum voltage of 12kV peak per accelerating gap was obtained stably at earlier period of an acceleration cycle. A beam test with this system is planned at the ISIS synchrotron in order to investigate how the low impedance system works under heavy beam loading conditions, and is capable of mitigating the space charge detuning at the RF trapping stage.
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| MOPCH122 |
Realistic Beam Loss Estimation from the Nuclear Scattering at the RCS Charge-exchange Foil
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333 |
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- P.K. Saha, H. Hotchi, Y. Irie, F. Noda
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
- H. Harada
Hiroshima University, Higashi-Hiroshima
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We have developed simulation tools for the realistic beam loss estimation at the RCS(rapid cycling synchrotron) of J-PARC(Japan Proton Accelerator Research Complex). The present simulation concerns an accurate estimation of the beam loss caused by the nuclear scattering at the charge-exchange foil during the multi turn injection period. It can also figure out the loss point in the ring, so would become very useful for the maintenance and optimization as well. The simulation code GEANT together with the SAD(Strategic Accelerator Design) have been used for the present purpose. In this paper, detail simulation method including the result will be discussed.
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| TUPLS028 |
An Irradiation System for Carbon Stripper Foils with 750 keV H- Beams
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1550 |
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- A. Takagi, Y. Arakida, Z. Igarashi, K.I. Ikegami, C. Kubota, I. Sugai, Y. Takeda
KEK, Ibaraki
- S. Dairaku, N. Saito, A. Sato, K. Senzaki
Kyoto University, Kyoto
- Y. Irie
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
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Carbon stripper foils of around 300 ug/cm2 will be used as a stripping of H-ion beam of the 3 GeV Rapid Cycling Synchrotron in the J-PARC. The foil should have a long lifetime with mechanically strong against high temperature of 1800K due to high-energy deposition by high intensity H-ion and circulating bunched proton beam irradiations. For this purpose, we have installed a new irradiation system using high intensity pulsed and dc H-beams of the KEK 750keV Cocksfoot-Walton accelerator. By adjusting the peak intensity and the pulse length of the hydrogen beams appropriately, the energy deposition becomes equivalent to that exerted by the incoming H- and the circulating beams at the injection process of the RCS. The new irradiation system and some preliminary results of the carbon stripper foil will be reported.
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| TUPLS108 |
Realization of Thick Hybrid Type Carbon Stripper Foils with High Durability at 1800K for RCS of J-PARC
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1753 |
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- I. Sugai, K. Hara, H. Kawakami, M. Oyaizu, A. Takagi, Y. Takeda
KEK, Ibaraki
- T. Hattori, K.K. Kawasaki
RLNR, Tokyo
- Y. Irie, J. Kamiya, M. Kinsho
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
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The J-PARC requires thick carbon stripper foils (250-500 ug/cm2) to strip electrons from the H-beam supplied by the linac before injection into a 3 GeV Rapid Cycling Synchrotron. The 200 MeV H- beam from the linac has a pulse length of 0.5 ms with a repetition rate of 25 Hz and an average beam current of 335 uA. By much energy deposition of these high-intensity H- and circulating bunched beams, commercially available best stripper foils (CM) will break in a very short time and even a diamond foil will rupture at around 1800K by MW class accelerators. We have realized for first time the hybrid boron doped carbon stripper foils with long life time for J-PARC. The foils of 250-500 ug/cm2 were made by a controlled DC arc-discharge method. The lifetime was tested by using 3.2 MeV Ne+ DC beam of 2.5 uA and 750 keV H- DC beam of 500 uA, in which a significant amount of energy was deposited in the foils. The maximum lifetime was extremely long, 120- and 480-times than those of diamond and CM foils. The foils were also free from any shrinkage, and showed low thickness reduction rate even at high temperature of 1800K during long time irradiation of 90h.
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| TUPLS111 |
Experimental Results of the Shift Bump Magnet in the J-PARC 3-GeV RCS
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1762 |
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- T. Takayanagi, Y. Irie, J. Kamiya, M. Kinsho, M. Kuramochi, O. Takeda, T. Ueno, M. Watanabe, Y. Yamazaki, M. Yoshimoto
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
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The shift bump magnet produces a fixed main bump orbit to merge the injection beam into the circulating beam. In order to control the injection beam for the short injection time (500 microseconds) with sufficient accuracy, the shift bump magnet needs a wide uniform magnetic field and the high speed exciting pattern of the high current. The magnetic field design and the structural analysis of the shift bump magnets have been performed using three-dimensional electromagnetic analysis code and mechanical analysis code, respectively. The magnetic field distributions were measured with a long search coil, thus giving a BL product over a magnet gap area. The temperature distributions at the various points of the magnet were measured by thermocouples over 24 hours till they saturated. General trend of these measurements agrees well with calculations.
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| TUPLS112 |
Present Status of Injection and Extraction System of 3 GeV RCS at J-PARC
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1765 |
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- M. Yoshimoto, Y. Irie, J. Kamiya, M. Kinsho, F. Noda, P.K. Saha, T. Takayanagi, O. Takeda, M. Watanabe
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
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The injection and extraction system for 3GeV RCS (Rapid Cycling Synchrotron) at J-PARC (Japan Proton Accelerator Research Complex) have many challenging issues, in order to realize MW beam in the RCS ring. The system is consisted in 3 parts, such as the injection line, the dump line, and the extraction line. And they are constructed from many kinds of components, such as DC and pulse magnets, a charge exchange system, beam monitors, titanium and ceramic vacuum chamber, a beam dump, and so on. Up to now, final designs are accomplished and developments and experiments of some components are carried out. In this presentation, summary of the injection and extraction system, recent status of developments, and beam commissioning scheme for beam injection and extraction are introduced.
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| TUPLS113 |
Designs of Septum Magnet at 3 GeV RCS in J-PARC
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1768 |
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- M. Yoshimoto, Y. Irie, J. Kamiya, M. Kinsho, T. Takayanagi, O. Takeda, M. Watanabe
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
- H. Fujimori, S. Igarashi, H. Nakayama
KEK, Ibaraki
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3 GeV RCS (Rapid Cycling Synchrotron) at J-PARC (Japan Proton Accelerator Research Complex) consists in many kinds of septum magnets. There are two septum magnets to inject the beam into the ring, three septum magnets to extract the beam for the users, and two septum magnets to dump the beam which can not be exchanged its charge at the first foil. In order to reduce the magnetic leakage field from the septum magnets at the beam orbit in the ring, the silicon steel sheets are set at the outside of the septum magnets for the magnetic shields. However sufficient spaces to set the thick magnetic shields are not securable at the divergent duct areas. Therefore the vacuum chambers are made by the magnetic stainless steel and the leakage fields in the chambers can be reduced. As results of the 3D field calculations by TOSCA, the magnetic leakage field can be suppressed to a few Gauss or less.
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| WEPCH028 |
Position Shuffling of the J-PARC Main Ring Magnets
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1984 |
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- M. Tomizawa, K. Fan, S. Igarashi, K. Ishii, H. Kobayashi, A.Y. Molodozhentsev, K. Niki, E. Yanaoka
KEK, Ibaraki
- Y. Irie
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
- S. Machida
CCLRC/RAL/ASTeC, Chilton, Didcot, Oxon
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The J-PARC 50GeV main ring has 96 dipole, 216 quadrupole with 11 families and 72 sextupole magnets with 3 families. Magnets installation in the tunnel started last year and will be planed to finish by the end of next fiscal year. Field measurements of all magnets will soon finish by this March. Deviations for BL, B'L, B"L in dipole, quadrupole and sextupole magnets make COD, beta beat and third integer stopband, respectively. They can be reduced by choosing a pair of magnets with similar field deviation and by positioning them so as to cancel each other considering betatron phase (shuffling). In this paper, we will report our shufflling scheme chosen under the given schedule for installation and field measurements and also will show performances expected by the shufflings.
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| WEPCH079 |
Effects of Intrinsic Nonlinear Fields in the J-PARC RCS
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2104 |
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- H. Hotchi, Y. Irie, F. Noda
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
- S. Machida
CCLRC/RAL/ASTeC, Chilton, Didcot, Oxon
- A.Y. Molodozhentsev
KEK, Ibaraki
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In order to accelerate a high intense proton beam with small particle losses, the J-PARC RCS, which is being constructed at JAEA, has a large acceptance. In such synchrotrons, the nonlinear motion of the beam particles, especially moving away from the axis of the elements, is a common issue, and it becomes essential to consider intrinsic field nonlinearities. The main sources of nonlinear magnetic fields in the RCS are as follows: fringes of the main dipole and quadrupole magnets, sextupole fields used for the chromatic correction, leak fields from the injection and extraction beam lines, etc. In this paper, we will discuss influences of the intrinsic field nonlinearities and a cure for the induced betatron resonances, based on single-particle and multi-particle tracking simulations.
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