Accelerator Design
We designed a feasible acceleration scheme for high intensity heavy-ion beams at J-PARC along with the existing proton acceleration scheme. In order to achieve the required world record of high beam intensity at more than 10 AGeV (GeV/nucleon) for a U92+ beam, we aim to utilize the high performance 3-GeV Rapid Cycling Synchrotron (RCS) as well as the 50-GeV Main Ring synchrotron (MR), approaching to the designed beam power for operation. The numerical parameters depicted in the figure correspond to a particular heavy ion species of U92+. Another goal is to accelerate other ion species as interested from the experimental point of view. The existing accelerator facility comprising a 400~MeV H- linac, the 3-GeV RCS, and the 50-GeV MR (operated at 30 GeV at present).The RCS simultaneously delivers a 3 GeV proton beam to the Material and Life Sciences Experimental Facility (MLF) and to the MR. The MR operates for either Fast Extraction (FX) for the Neutrino Experimental Facility (NU) or Slow Extraction (SX) for the Hadron Experimental Facility (HD). The MR cycles for FX and SX operation are currently 2.48 s and 5.52 s, respectively, but the cycles will be shortened at least by 1 s from the present values in near future.
The largest advantage of using the RCS and the MR for the heavy-ion acceleration is that we have already understood and optimized performance of each machine for the designed or nearly the designed beam power. The RCS has been already successfully demonstrated an extraction of 1 MW equivalent beam power (8.33×1013/cycle). In the MR, the FX beam and the SX beam power has been reached 400 kW (2×1014/cycle) and 50 kW (0.6×1014/cycle), respectively. Those values are already more than a half and just a half from the designed beam power for the FX and SX operation, respectively. It thus enables us for realistic discussions on beam dynamics issues and measures to aim at the world's most intensive heavy-ion beams. On the other hand, the uses of existing buildings and devices make very much reduction of the construction cost. The primary goal is to achieve a more than 1011 U92+ ions per MR cycle. Table.1 shows a summary of key parameters and required accelerator performance for the heavy-ion physics program by using U92+ beam.
| Parameter | Value |
|---|---|
| Beam energy | 0.727-11.2(19.5) AGeV |
| √sNN | 1.9-4.9(6.2) AGeV |
| Beam rate | 4×1011(/MR cycle) |
| MR cycle | ~4.5 s |
| Average beam rate | 1×1011(Hz) |
| Extraction scheme | Slow extraction |
