1. Parametrisation of PRISM Ring and Design Options J. Pasternak Imperial College London/RAL STFC PRISM-FFAG Task Force phone meeting, 10.09.2009

2. Outline Introduction and motivation Current PRISM design Possible strategy Basic parametrisation and constrains Ring design options Summary

3. As charge lepton flavor violation (cLFV) is strongly suppressed in the Standard Model, its detection would be a clear signal for new physics! Search for cLFV is complementary to LHC. The  - + N(A,Z)→e - + N(A,Z) seems to be the best laboratory for cLFV. The background is dominated by beam, which can be improved. The COMET and Mu2e were proposed. The PRISM-FFAG ring was proposed for a next generation experiment in order to: -reduce the muon beam energy spread by phase rotation, -purify the muon beam in the storage ring. Search for cLFV and motivations for PRISM

4. The PRISM-FFAG Task Force was proposed and discussed during the last PRISM-FFAG workshop at IC (1-2 July’09). The aim of the PRISM-FFAG Task Force is to address the technological challenges in realising an FFAG based muon-to-electron conversion experiment, but also to strengthen the R&D for muon accelerators in the context of the Neutrino Factory and future muon physics experiments. It was proposed to achieve a conceptual design of the PRISM machine at the end of 2010/beginning 2011. The following key areas of activity were identified and proposed to be covered within the Task Force: - the physics of muon to electron conversion, - proton source, - pion capture, - muon beam transport, - injection and extraction for PRISM-FFAG ring, - FFAG ring design including the search for a new improved version, - FFAG hardware R&D for RF system and injection/extraction kicker and septum magnets. The Task Force will use phone conferences and next PRISM-FFAG workshops were proposed. The PRISM-FFAG Task Force Initiative Please join! j.pasternak@imperial.ac.uk

5. PRISM-FFAG Task Force phone meeting, 10.09.2009 V per turn ~2-3 MV Δp/p at injection = ± 20% Δ p/p at extraction = ± 2% (after 6 turns ~ 1.5 us) h=1 Current Design Parameters – A. Sato

6. PRISM-FFAG Task Force phone meeting, 10.09.2009 Possible PRISM Task Force Design Strategy Option 1: Adopt current design and work out injection/extraction, and hardware Option 2: Find new design They should be evaluated in parallel and finaly confronted with the figure of merit (FOM) (number of muons delivered to target/cost). We may also need to have a common FOM with COMET (muons at target/background ??)

7. PRISM-FFAG Task Force phone meeting, 10.09.2009 Requirements for a new design High transverse acceptance (at least 38h/5.7v [Pi mm] or more). High momentum acceptance (at least ± 20% or more). Small orbit excursion. Compact ring size (this needs to be discussed). Relaxed or at least conserved the level of technical difficulties. for hardware (kickers, RF) with respect to the current design.

8. PRISM-FFAG Task Force phone meeting, 10.09.2009 Basic constraints Energy acceptance depends on RF voltage and harmonic number. Observation: if we want to go for h=2, we need a factor of 2 more RF! Synchrotron tune tells us about number of turns needed for phase rotation. Observation: for h=2 phase rotation is twice as fast (3turns). If we want to change the central momentum (keeping momentum acceptance), RF voltage goes down! Changing central momentum increases revolution time. This is good for kickers, but you need to be within the frequency range of MA cavities. C. Ohmori

9. PRISM-FFAG Task Force phone meeting, 10.09.2009 Preliminary scaling Current design: p0 = 68 MeV/c h=1 Δ p/p at injection = ± 20% V = 2.3 MV RF frequency = 3.55 MHz Trev= 280 ns Trise for the kicker=80 ns N of turns = 6 Option 1: p0 = 68 MeV/c h=2 Δ p/p at injection = ± 20% V = 4.6 MV RF frequency = 7.1 MHz too large? Trev= 280 ns Trise for the kicker~ 140 ns! N of turns = 3 Option 1a: p0 = 68 MeV/c h=2 Δ p/p at injection = ± 20% V = 4.6 MV RF frequency = 3.55 MHz Trev= 560 ns Trise for the kicker~ 280 ns! N of turns = 3 RF is expensive!

10. PRISM-FFAG Task Force phone meeting, 10.09.2009 Preliminary scaling (2) Current design: p0 = 68 MeV/c h=1 Δ p/p at injection = ± 20% V = 2.3 MV RF frequency = 3.55 MHz Trev= 280 ns Trise for the kicker=80 ns N of turns = 6 Option 2: p0 = 40 MeV/c h=1 Δ p/p at injection = ± 20% V = 1.15 MV (??) It needs be to check! RF frequency = 2.3 MHz too low? Trev= 430 ns Trise for the kicker~ 123 ns! N of turns <5 Option 2a: p0 = 40 MeV/c h=2 Δ p/p at injection = ± 20% V = 2.3 MV (?) RF frequency = 4.6 MHz Trev= 430 ns Trise for the kicker~ 215 ns! N of turns <3

11. PRISM-FFAG Task Force phone meeting, 10.09.2009 R Ring Design Options Scaling FFAG Options: standard lattice, periodic with extended cell (for example 5 magnets per cell), superperiodic (see Shinji’s talk) advanced (Y. Mori) Non-Scaling FFAG Problems to be addressed: confirmation of a large DA currently no insertion scheme, very difficult injection TOF with amplitude

12. PRISM-FFAG Task Force phone meeting, 10.09.2009 Summary PRISM-FFAG Task Force was created. We need to discuss the strategy for the ring design. The ring design is constrained mostly by RF voltage, frequency and central momentum. There exist a variety of choices for the ring structure and optics.