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Collimation efficiency with various physical apertures. Designed physical aperture sizes correspond to 1.0 of physical aperture ratio.
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In order to localize the beam loss on the restricted area, the
beam collimation system design has been performed for the 3GeV
synchrotron of the JAERI-KEK joint project. The beam loss distribution
has been calculated with Monte-Carlo simulation code STRUCT developed at
the Fermi national laboratory. The collimation efficiency was calculated
for two...
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Citations
... In order to achieve such a high-power output while maintaining the residual doses at a hands-on-maintenance level, the losses must be localized to a restricted area. To establish such a condition, a collimation system was installed in the J-PARC RCS [2][3][4]. In particular, a classical two-stage collimator system was adopted for the RCS ring collimator [5][6][7]. ...
... Email: kazami@post.j-parc.jp RCS ring collimation system are described in the literature [2][3][4]8,9]. ...
The most important issue in a high intensity proton accelerator is to keep the accelerator tunnel in a hands-on-maintenance condition. A collimation system was designed and installed in 3GeV Rapid Cycling Synchrotron (RCS) at the Japan Proton Accelerator Research Complex (J-PARC) to be localized the beam loss point to a restricted area. The experimental results indicated that the RCS collimation system performs well enough such that nearly all the ring components are maintained in good condition. However, as the beam power increased, unexpected losses downstream of the injection foil increased. Therefore, an additional collimator was installed that successfully reduced such unexpected losses.
... As a result, the temperature exceeded 200 degrees C with the design heat (700W) by natural air cooling. Next we tried forced air cooling by using the cooling fan and the temperature of the horizontal collimator fell below 120 degrees C. We adopt forced air cooling system [14]. ...
... After confirming all action, we checked by the helium leak examination that it can close less than 5.0E-10 Pa m3/sec helium leak. Moreover, it was confirmed that the leak level was same even if the central axis of opposite flanges was off to the side as 1mm [14]. ...
A 3GeV Rapid-Cycling Synchrotron (RCS) in Japan Proton Accelerator Research Complex (J-PARC) has been commissioned since September 2007. The most important issue in the beam study is to reduce unnecessary beam loss and to keep the beam line clean for the sake of maintenance and upgrade of the machines. From experience of the former accelerators, the average beam loss should be kept at an order of 1 watt per meter for hands-on maintenance. Since it is very difficult to control the beam loss at such a low level, the only measure we can take is to localize any of the losses in a restricted area, where deliberate modules should be provided for quick coupling and remote handling in order to mitigate the personal doses. Accordingly, we have designed the beam collimation system for the purpose of the beam loss localization. We report the performance of the beam collimation system of RCS through the first commissioning results and the residual doses around RCS components.
... The beam collimation system of RCS is prepared to localize the beam loss in the restricted area and to keep another area an order of 1W/m. The amount of the localized beam loss on the one collimator is estimated about 1.2kW [2], and that loss generates a large quantity of the secondary radiation. This is the side cross section of collimator shield. ...
In order to localize the beam loss in the restricted area, the beam collimation system is prepared in the 3GeV Rapid Cycling Synchrotron (RCS) of the Japan Proton Accelerator Complex (J-PARC) Project. The amount of the localized beam loss on the one collimator is estimated about 1.2kW, and that loss generates a large quantity of the secondary radiations. So the beam collimator must be designed that it is covered with enough shielding. We calculated the radiation dose of the collimator and decided necessary shielding thickness. This result indicated that the residual dose rate at the outside surface of the shielding was mostly under 1mSv/h. We developed the remote cramp system and rad-hard components in order to reduce the radiation exposure during maintenance of the collimator. And also we coated The Titanium Nitride (TiN) film on the inside surface of the vacuum chamber in order to reduce the secondary electron emission from the collimator and the chamber surface. Now we investigate the possibility of another coating.
... The 400 MeV protons of the beam halo, which are scraped initially at the collimator targer, were traced along the whole ring using a multi-turn tracking Monte Carlo code, STRUCT (5) for the estimation of the beam-loss distribution (6) . The beam pipe and the collimator aperture and the magnet fields were taken into account and 50,000 particles were traced in the calculation. ...
MARS14 Monte Carlo simulations were performed for collimation and shielding studies of the J-PARC 3 GeV synchrotron ring. The beam line module locations in the 348.3 m ring and the curved tunnel sections were described by the 'MAD-MARS beam line builder' tool. A 400 MeV proton beam loss distribution, calculated with the STRUCT code, was used as a 4 kW source term in the collimator region, with 1 kW source terms in the injection and extraction regions at 400 MeV and 3 GeV, respectively. Deep penetration calculations were carried out with good statistics using a newly developed three-dimensional multi-layer technique. Prompt dose-rate distributions were calculated inside and outside the concrete and soil shield up to the ground level. Using the calculation results obtained thus, an effective shielding design was made.
... Sum of proton beam loss (halo) at the collimator section will be 4 kW. The distributions of the beam loss in the collimators and the components around them were estimated from the calculation [3] by STRUCT [4]. It was found from the results that the total beam losses at the position of the 2nd collimator and the beam duct around the collimator were estimated to be 1566W, which is the largest beam loss in the six collimators. ...
... of the facility.Table I. From the calculation results by STRUCT, proton beam losses at the 2nd collimator, and the upstream and the downstream beam ducts near the collimator are assumed to be 910W, 520W and 136W, respectively [3]. For both the bulk shielding and the self-shielding for the activations, the collimator is covered with a collimator shield of iron and concrete complex shown in the figure. ...
Estimation of radioactivity and residual dose in accelerator tunnel is very important for the shielding design of a high-intensity proton accelerator facility. In the present work, radioactivity and residual dose rate around the collimator were estimated for 3-GeV proton synchrotron of the J-PARC facility. Exposure dose due to radioactivity in the components of the collimator, local shields and concrete walls of accelerator tunnel around the collimator section were calculated by using PHITS, DCHAIN-SP and QAD-CGGP2.
... The parameters of 3 GeV PS dedicated to the rf system are shown in Table 1, and the change of the accelerating voltage and the synchronous phase are shown in Fig. 2, which was calculated by RAMA [7] including the space charge effects. The maximum 421 kV of accelerating voltage should be obtained in ~20 m of straight section under the constraint of lattice design [8]. Considering the maximum anode current of the tetrode tube which should be comparable with the beam current due to the stability under the heavy beam loading, we choose that ten cavities will be prepared to generate such voltage, where each cavity has three accelerating gaps. ...
RF acceleration system for 3 GeV proton synchrotron in Joint JAERI-KEK high intensity proton accelerator project is described. In this synchrotron, since 8.3 x 10 13 protons must be acceler-ated from 400 MeV to 3 GeV within 20 ms, wide-band frequency range and high accelerating voltage are required, and the system must be stable under heavy beam loading. From the results of R & D works over the past several years, high gradient rf cavity loaded with Magnetic Alloy and 1.2 MW class push-pull tetrode tube amplifier will be chosen for this system. Their design and R & D works for this synchrotron are reported. Furthermore, since longitudinal beam emittance will be controlled at injection and extrac-tion by the rf manipulation because of alleviation of space charge effect, some simulation results for longitudinal motion by a particle tracking code are reported.
MARS14 Monte Carlo simulations were performed for collimation and shielding studies of the J-PARC 3 GeV synchrotron ring.
The beam line module locations in the 348.3 m ring and the curved tunnel sections were described by the ‘MAD-MARS beam line
builder’ tool. A 400 MeV proton beam loss distribution, calculated with the STRUCT code, was used as a 4 kW source term in
the collimator region, with 1 kW source terms in the injection and extraction regions at 400 MeV and 3 GeV, respectively.
Deep penetration calculations were carried out with good statistics using a newly developed three-dimensional multi-layer
technique. Prompt dose-rate distributions were calculated inside and outside the concrete and soil shield up to the ground
level. Using the calculation results obtained thus, an effective shielding design was made.
The 3-GeV rapid cycling synchrotron (RCS) of the Japan Proton Accelerator Research Complex (J-PARC) was commissioned in October 2007, and successfully accomplished 3 GeV acceleration on October 31. Six run cycles through February 2008 were dedicated to commissioning the RCS, for which the initial machine parameter tuning and various underlying beam studies were completed. Then since May 2008 the RCS beam has been delivered to the downstream facilities for their beam commissioning. In this paper we describe beam tuning and study results following our beam commissioning scenario and a beam performance and operational experience obtained in the first commissioning phase through June 2008.
