1. μ-Capture, Energy Rotation, Cooling and High-pressure Cavities David Neuffer Fermilab

2. 2 0utline  Motivation  Study 2AP Neutrino factory …  Muon Collider, …  “High-frequency” Buncher and  Rotation  Study 2Ap scenario, obtains up to ~0.2  /p  Integrate cooling into phase-energy rotation  Gas-Cavity Variations  Cooling in bunching and phase rotation  Higher gradient, lower frequency ???  Shorter system, fewer bunches  Optimization ….  Polarization  Use high gradient rf near target to improve polarization

3. 3 Advantages of high-pressure cavities  high gradient rf  In magnetic fields B=1.75T, or more …  With beam  Change cavity f rf by   Can Integrate cooling with capture  Capture and phase-energy rotation + cooling  Can get high-gradient at low frequencies (30, 50, 100 MHz ???)  Beam manipulations  Polarization Research can be funded…

4. 4 Study2A Dec. 2003  June2004  Drift –110.7m  Bunch -51m  V’ = 3(z/L B ) + 3 (z/L B ) 2 MV/m (× 2/3) (85MV total)  (1/  ) =0.0079  -E Rotate – 52m – (416MV total)  12 MV/m (× 2/3)  P 1 = 280, P 2 = 154  V = 18.032  Match and cool (100m)  V’ = 15 MV/m (× 2/3)  P 0 = 214 MeV/c  0.75 m cells, 0.02m LiH

5. 5 Study2AP June 2004 scenario  Drift –110.7m  Bunch -51m  V  (1/  ) =0.0079  12 rf freq., 110MV  330 MHz  230MHz  -E Rotate – 54m – (416MV total)  15 rf freq. 230  202 MHz  P 1 = 280, P 2 = 154  N V = 18.032  Match and cool (80m)  0.75 m cells, 0.02m LiH  “Realistic” fields, components  Fields from coils  Be windows included

6. 6 Simplest Modification  Add gas + higher gradient to obtain cooling within rotator  ~300MeV energy loss in cooling region  Rotator is 51m;  Need ~6MeV/m H 2 Energy loss  9MeV/m if cavities occupy 2/3  ~30% Liquid H 2 density  Alternating Solenoid lattice in rotator  21MV/m rf  Try shorter system … Cool here

7. 7 Short bunch train option  Drift (20m), Bunch–20m (100 MV)  Vrf = 0 to 15 MV/m (  2/3 )  P 1 at 205.037, P 2 = 130.94  N = 5.0  Rotate – 20 m (200MV)  N = 5.05  Vrf = 15 MV/m (  2/3 )  Palmer Cooler up to 100m  Match into ring cooler  ICOOL results  0.12  /p within 0.3  cm  Could match into ring cooler (C~40m) (~20m train) 60m 40m 95m

8. 8 FFAG-influenced variation – 100MHz  100 MHz example  90m drift; 60m buncher, 40m rf rotation  Capture centered at 250 MeV  Higher energy capture means shorter bunch train  Beam at 250MeV ± 200MeV accepted into 100 MHz buncher  Bunch widths < ±100 MeV  Uses ~ 400MV of rf

9. 9 Lattice Variations (50Mhz example) Example I (250 MeV)  Uses ~90m drift + 100m 100  50 MHz rf (<4MV/m) ~300MV total  Captures 250  200 MeV  ’s into 250 MeV bunches with ±80 MeV widths Example II (125 MeV)  Uses ~60m drift + 90m 100  50 MHz rf (<3MV/m) ~180MV total  Captures 125  100 MeV  ’s into 125 MeV bunches with ±40 MeV widths

10. 10 Polarization for μ + -μ - Colliders  Start with short proton bunch on target < ~1ns  Before π⇒μ+ν decay, use low-frequency rf to make beam more monochromatic  ~50MV in ~5m?  Drift to decay (~10m?)  Higher energy μ’s pol. +  Lower energy μ’s pol. –  ¼ Phase-Energy rotation  ~10m  Rebunch at ~2× frequency  +’s in one bunch  -’s in other bunch + + - -

11. 11 Summary  High-frequency Buncher and  E Rotator (ν-Factory) improved (?) with high-pressure cavities  Shorter systems  Lower Frequency (fewer bunches).  μ + -μ - Colliders …  Polarization … To do:  Optimizations, Best Scenario, cost/performance …

12. 12 Current Status (New Scientist) (or μ + -μ - Collider)

13. 13 DoE/NSF today …