Parametrisation of PRISM Ring and Design Options J. Pasternak Imperial College London/RAL STFC

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. Search for cLFV and motivations for PRISM • 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.

4. The PRISM-FFAG Task Force Initiative • 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. Please join! j.pasternak@imperial.ac.uk

5. Current Design Parameters – A. Sato 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

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

12. 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.