Abstract
The 3-GeV rapid cycling synchrotron (RCS) of Japan Proton Accelerator Research Complex (J-PARC) simultaneously delivers high intensity beam to the Material and Life Science Experimental Facility (MLF) as well as to the main ring (MR) at a repetition rate of 25 Hz. The RCS is designed for a beam power of 1 MW. RCS has to meet not only the need of power upgrade but also the specific requirement of each downstream facility. One of the issues, especially for high intensity operation, is to maintain two different transverse sizes of the extracted beam for MLF and MR; namely, a wider beam for MLF in order to reduce damage on the neutron production target but reversely a narrower one for the MR in order to ensure a permissible beam loss in the beam transport line of 3-GeV to MR and also in the MR. We proposed pulse-to-pulse direct control of the transverse painting area during the RCS beam injection process in order to get an extracted beam profile as desired. In addition to two existing dc septum magnets used for fixing injected beam trajectory for MLF beam, two additional dipoles named pulse steering magnets are designed for that purpose in order to control injected beam trajectory for a smaller painting area for the MR. The magnets are already installed in the injection beam transport line and successfully commissioned well in advance before they will be put in normal operation in 2014 for the 400 MeV injected beam energy upgraded from that of the present 181 MeV. Their parameters are found to be consistent to those expected in the corresponding numerical simulations. A trial one cycle user operation run for a painting area of $100\ensuremath{\pi}\text{ }\text{ }\mathrm{mm}\text{ }\mathrm{mrad}$ for the MR switching from the MLF painting area of $150\ensuremath{\pi}\text{ }\text{ }\mathrm{mm}\text{ }\mathrm{mrad}$ has also been successfully carried out. The extracted beam profile for the MR is measured to be sufficiently narrower as compared to that for the MLF, consistent with numerical simulation successfully demonstrating validity of the present principle.
Highlights
The 3-GeV rapid cycling synchrotron (RCS) of Japan Proton Accelerator Research Complex (J-PARC) is designed for a high power proton beam source of 1 MW (8:33 Â 1013 protons per pulse) for the neutron and muon production targets in the Material and Life Science Experimental Facility (MLF) as well as an injector for the 50-GeV main ring synchrotron (MR) [1]
In order to keep control of the foil scattering beam loss, we proposed an efficient way for switching MLF painting area to the MR one by changing only the angle of the injected beam to a smaller value
A required bending angle of each pulse steering (PSTR) magnet is determined, which is transformed to the magnetic field multiplying by the magnetic rigidity of the injected beam energy
Summary
The 3-GeV rapid cycling synchrotron (RCS) of Japan Proton Accelerator Research Complex (J-PARC) is designed for a high power proton beam source of 1 MW (8:33 Â 1013 protons per pulse) for the neutron and muon production targets in the Material and Life Science Experimental Facility (MLF) as well as an injector for the 50-GeV main ring synchrotron (MR) [1]. We proposed pulse-to-pulse direct control of the transverse painting area during the injection process in order to ensure a desired transverse beam profile or in other words, to ensure a desired transverse emittance at the extraction. In order to switch the painting area MLF to MR in a pulse-to-pulse mode, one has to changed the injected beam trajectory. Two horizontal pulse dipole magnets are proposed to install with existing two dc septum magnets (ISEP1-2) They are named pulse steering (PSTR) magnets and have already been installed in the linac to the 3-GeV RCS beam transport (L-3BT) line in the 2012 summer shutdown period.
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