Protons for a m + m - Higgs Factory, Sooner Chuck Ankenbrandt Muons , Inc. Physicist And

1. Higgs Collider Workshop Protons for a m+m- Higgs Factory, Sooner Chuck Ankenbrandt Muons, Inc. Physicist And FermilabScientist Emeritus November 13, 2012 Chuck Ankenbrandt, Muons, Inc.

2. Outline • Introduction • Using 3-GeV Protons from Project X • Using 60-GeV Protons from the Main Injector • Conclusions Chuck Ankenbrandt, Muons, Inc.

3. Introduction • The baseline proton driver and front end promise high performance to drive an energy-frontier muon collider. • But there is a sense of urgency—can we do a Higgs Factory faster by trading performance for speed? • Current plans call for implementing Project X in 3+1 stages. • The first three stages include 1, 3, 8 GeV linacs. • The fourth stage would transform the facility into a 4-MW PD. • That will take a while… • This talk considers two faster-track possibilities: • Using the Project X 3-GeV CW linac beam • Using 60-GeV beam from the Main Injector Chuck Ankenbrandt, Muons, Inc.

4. 3-GeV Driver-Intro • At last Friday’s MAP meeting Yuri Alexahin described a scenario based on using 1 MW of 8-GeV protons. • Here I’ll scale his luminosity to 1 MW of 3-GeV protons. • So dNp/dt goes up by 8/3 for the same beam power. • Assumptions: • The yield Nm/NpTp is the same at 3 and 8 GeV. • The pion production target geometry is the same . • Two challenges: space charge and multi-turn injection; both can be alleviated by raising the rep rate. • Assume the 4-MW baseline proton driver is at the SC limit • What’s the resulting collider luminosity? Chuck Ankenbrandt, Muons, Inc.

5. Beam size and geometrical emittance • The maximum geometrical emittance is determined by the beam size requirement at the pion prod. target: • The beta function should match the effective target length. • The geometrical emittance is then limited: assume same as 8 GeV • Note that the beam size in the 3-GeV ring can thus be smaller than that in the 8-GeV ring because Chuck Ankenbrandt, Muons, Inc.

6. Scaling of SC tune shift and Luminosity • The space-charge tune shift scales as • For 3 GeV instead of 8 GeV at 1 MW, • dNp/dt goes up by 8/3. • Note that dNp/dt = Frep * Np • The kinematic factor goes down by a factor 12.26 • Assuming that the 4 MW, 8 GeV system is sc-limited, • the upshot is that Frep must go up by 12.26*8/(3*4) = 8.2 • The luminosity scales like 1/Frep, so it goes down x 8.2 • (This would work pretty well for a neutrino factory.) Chuck Ankenbrandt, Muons, Inc.

7. Can we do better than 1/8 at 3 GeV ? • Push the parameters: • Use 3 MW instead of 1 MW • Increase the geometrical emittance • Maybe higher space-charge tune shift is tolerable. • Use multiple 3-GeV accumulation rings: • They’re relatively inexpensive. • 4 rings would cost less than two 8-GeV rings of larger aperture. • All of that might get us close to Yuri. • But what if we’re really impatient?? Chuck Ankenbrandt, Muons, Inc.

8. 60-GeV Main Injector Driver-Intro • The Main Injector will deliver 700 kW post-shutdown; • It may deliver ~ 1.5 MW after Phase 1 of Project X. • The cycle time will be about 0.8 sec at 60 GeV. • 60 GeV is less effective at making usable muons per unit power. • Problem: the Main Injector proton bunch train is long. • There may be a simple way to make short, intense, cooled muon beams from a long proton beam. • How can we do that? • What will the resulting performance be? Chuck Ankenbrandt, Muons, Inc.

9. The 2-Ring CircUS: Cartoon Layout p-, m- ring extracted m- MI beam Production target extracted m+ p+, m+ ring Chuck Ankenbrandt, Muons, Inc.

10. The 2-Ring CircUS: System Concepts Chuck Ankenbrandt, Muons, Inc. There are two pion/muon fixed-energy storage rings. They function as pion production, collection, decay, and muon cooling rings. The rings share a common straight section; there are splitter/recombiner dipoles at the ends of that straight section. MI protons impinge on a low-Z target at low beta in the shared straight section. The revolution times of both rings are multiples of the fundamental 1/(53.1 MHz) bunch spacing of the Main Injector. The rings have RF to maintain rf bunching and to restore the energy lost when the beams pass thru matter.

11. Characteristics of the Rings Chuck Ankenbrandt, Muons, Inc. p = eBr means Br = 1 Tm at 300 MeV/c. So r~ 0.5 m. Size p/m ring circumferences to create several bunches spaced at 53 MHz (we can coalesce them later). Say C = 5*5.65 m. They operate close to transition energy. The acceptances must be very large. Recirculating systems allow multiple passes thru RF cavities, providing affordable multipass cooling. We extract three times each MI cycle, so the bunch train is about 3.3 msec long; about 1/2 a muon lifetime. The resulting rep rate in the collider is about 3 Hz.

12. Summary/conclusions • A system based on the Project X 3-GeV CW linac: • could provide performance comparable to a 1 MW 8-GeV system. • would work very well to drive a neutrino factory. • The 2-Ring CircUS idea is intriguing; • Its feasibility and performance need to be evaluated. Chuck Ankenbrandt, Muons, Inc.