| Paper | Title | Page |
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| THPD054 | Inverse Compton Scattering by Laser Accelerated Electrons and its Application to Standoff Detection of Hidden Objects | 4404 |
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A technique for remote detection of hidden objects is an urgent issue, but is not yet realized, because a source and a sensor must be located on the same side of the object. An ultra-intense laser can produce extremely short and directional radiations, that is the inverse Compton scatterings used for the backscattering system. We here demonstrate that the laser-wakefiled-accelerated 10-MeV electrons inversely scatter the same laser light to keV X-ray emissions. A 10 TW OPCPA Ti:sapphire laser BEAT ( 1J output, wavelength 815 nm, and pulse width 150fs) is divided to two beams. A 0. 8-J beam is focused to an entrance edge of helium gasjet to accelerate electrons via wakefield and the other 0.2-J beam is focused to the exit of the plasma channel from the opposite direction. A second harmonic probe light measured the channel density. To the upstream direction of the latter beam, a CdTe detector analyzed the Compton spectrum under a photon counting mode* in the range of 1 keV to 20 keV, which well agrees with that calculated from the obtained electron spectrum up to a few tens MeV. We also have observed that the emission is strong into the laser axis direction. *H. Kuwabara, Y. Mori, Y. Kitagawa, 'Coincident Measurement of a Weakly Backscattered X-ray with a CPA Laser-Produced X-ray Pulse', Plasma Fusion Research: 3, 003-004 (2008). |
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| MOPEB009 | Low Leakage Field Septa for J-PARC Main Ring Injection System Upgrade | 295 |
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Injection into the J-PARC main ring is implemented by 4 kickers and 2 pulsed septa at 3 GeV in a long straight section. To accommodate the injection beam of 54 pmm.mrad, both septa have large physical acceptance of 81 pmm.mrad. However, large aperture leads to large end fringe field interfereing the circulating beam and causing beam loss, which has been observed even at low beam intensity during the beam commissioning. To provide users a proton beam with high beam power, the injection beam intensity will increase greatly in future, which creates difficulties for the present injection system. To accommodate these high intensity beams with low beam loss, the injection system needs to be upgraded. Taking account the strong space charge effects, even larger physical is needed to reduce the localized beam loss, which creates severer end fringe leakage field. This paper will discuss the problems encountered in operating the present septa, and give an optimized design for the new septa. |
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| MOPEB010 | Development of a High Radiation Resistant Septum for JPARC Main Ring Injection System | 298 |
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The J-PARC is a high intensity proton accelerator complex, which consists of a LINAC, a Rapid Cycling Synchrotron (RCS) and a Main Ring (MR). The MR injection system employs a high-field septum to deflect the incoming beam from the RCS, which has been used for the beam commissioning study with low beam intensity successfully. Relative large beam losses in the injection area have been observed, which is proportional to the injection beam intensity. In future, the beam intensity will increase about 100 times to realize high beam power (~MW) operation required from neutrino experiments. The beam loss at the injection region is expected increase greatly due to the space charge effects, which creates severe radiation problems. Since the present injection septum coil is organic insulated, which will be destroyed under such a severe irradiation quickly. To cope with this problem, a new high radiation resistant injection septum magnet is developed, which uses inorganic insulation material (Mineral Insulated Cable - MIC) to prevent the septum from radiation damage. This paper investigates different effects caused by the MIC and gives an optimization design. |
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| THPEB015 | Beam Injection Tuning of the J-PARC Main Ring | 3915 |
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The beam commissioning of J-PARC (Japan Proton Accelerator Research Complex) MR (Main Ring) was started from May 2008 and is in progress. As usual, injection tuning is in the first stage and strongly related to other tuning items. Starting with design schemes, making adjustment due to leakage field influence from injection septum, doing envelope matching considering dilution of beam profile in Main Ring are reported in this paper. The 'Without bump' scheme was got on June 15th 2008, while 'With bump' scheme on February 15th 2009. Beam orbit betatron oscillation to the MR close orbit which cause by injection error is less than 1 mm both in horizontal and vertical direction. Meanwhile, Beam Optics matching for 3 GeV beam from 350BT to MR has been well done too, which is also very important. * T. Koseki, Challenges and Solutions for J-PARC Commissioning and Early Operation, in these proceedings |
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| THPEB016 | Beam Fast Extraction Tuning of the J-PARC Main Ring | 3918 |
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The beam commissioning of J-PARC/MR has been started from May 2008 and is in progress*. One key purpose of MR commissioning is the 30 GeV beam fast extraction to Neutrino beam line, which reflect the overall commissioning result. In the MR, the third straight section is assigned for the fast extraction. 5 kickers and 8 septa were installed there, which can give beam a bipolar kick to inside or outside of MR. Inside kick means beam to Neutrino Oscillation Experiment, while outside kick means beam dumped to abort line. However before commissioning, the measured magnetic field distribution of each septa shows non-linear profile along the horizontal direction. In order to find the influence, a simulation with these measured field has been performed. Depends on this study and some OPI (Operation Interface) made by code SAD for orbit modification online, fast extraction of 30 GeV beam to Neutrino line has been achieved on April 23rd 2009. Beam orbit have been tuned to less than 0.5 mm and 0.1 mrad in both horizontal and vertical at the beginning of Neutrino line, which is also the end of MR fast extraction. And so far, 100 kW continual operation to neutrino line have been achieved, too. * T. Koseki, "Challenges and Solutions for J-PARC Commissioning and Early Operation", in these proceedings |