Phase Rotated Intense Slow Muon (PRISM) source
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Although COMET is a lepton flavour violation experiment in its own right, it is primarily a pre-cursor to the Phase-Rotated Intense Slow Muon (PRISM) source experiment which implements a scaling Fixed Field Alternating Gradient (FFAG) accelerator for Phase Rotation of the intense muon beam. Phase rotation is a well established technique used to reduce the spatial size of a beam of particles, by accelerating slow muons and decelerating fast ones; advantageous as the muon beam will become monochromatic (&Delta E /E of a few %) at low-energies (20 MeV). As well as increasing the intensity of the muon beam entering the phase-rotating FFAG, the additional path length is used to effectively eliminate beam contamination of pions, as even the most energetic of pions in the beam will have decayed after a few turns in the FFAG. The insertion of the FFAG ring into the PRISM schematic can be seen in the diagram to the right, rotating the phase of the muon beam before it interacts with the stopping target further down the beamline. The effect of phase rotation on the beam can be seen in the before and after plots below. This technique of phase rotation, however, has never been used with such a large emittance beam before (possibly as large as 10000 &pi mm mrad). An FFAG is the obvious choice in this case as the beam has such a large emittance and it is necessary to accelerate the muons before they decay. As phase rotation will increase intensity of the muon beam, a Titanium target is chosen which will increase the predicted branching ratio by a factor of 1.4 relative to Aluminium. Both these factors will increase the sensitivity to LFV by a factor of 100. | 
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| Although the PRISM project is many years away from completion, the MUSIC project, a pilot experiment for PRISM, may be up and running by as soon as Spring 2010. MUSIC will be installed in the Nuclear Physics lab at Osaka University, under the supervision of the collaboration spokesperson Prof. Yoshi Kuno, and will comprise of a 'slimmed down' version of PRISM with 6 magnetic cells and one accelerating RF cavity. The principle of phase rotation on &mu+ will be analysed so check back here soon for some interesting results hot out of Japan... |
Last Modified : 15:46:10 05 Jun 2009