1. MICE Ionization Cooling Channel and Phase II Construction Michael S. Zisman Center for Beam Physics Accelerator & Fusion Research Division Lawrence Berkeley National Laboratory MICE Funding Agency Committee Meeting—RAL April 18, 2008

2. MICE-FAC: Zisman2 Outline Introduction Muon beam challenges Ionization cooling System description Stages Estimated performance Module design and fabrication status R&D issues Future activities International perspective Summary

3. April 18, 2008MICE-FAC: Zisman3 Introduction (1) Motivation for MICE —muon-based Neutrino Factory is most effective tool to probe neutrino sector and, hopefully, observe CP violation in leptons o results will test theories of neutrino masses and oscillation parameters, of importance for both particle physics and cosmology —a high-performance Neutrino Factory (≈10 21 e aimed at far detector per 10 7 s year) depends on ionization cooling o straightforward physics but not experimentally demonstrated —facility will be expensive (O(1B€)), so prudence dictates a demonstration of the key principle —a Muon Collider depends even more heavily on ionization cooling Cooling demonstration aims to: —design, engineer, and build a section of cooling channel capable of giving the desired performance for a Neutrino Factory —place this apparatus in a muon beam and measure its performance in a variety of modes of operation and beam conditions

4. April 18, 2008MICE-FAC: Zisman4 Introduction (2) Another key aim: —show that design tools (simulation codes) agree with experiment o gives confidence that we can optimize design of an actual facility –we are testing a section of “a” cooling channel, not “the” cooling channel  simulations are the means to connect these two concepts Both simulations and apparatus to be tested should be as realistic as possible —must incorporate full engineering details of all components into the simulation Here I will cover the cooling channel concept, component design, fabrication status, and supporting R&D

5. April 18, 2008MICE-FAC: Zisman5 Muon Beam Challenges Muons created as tertiary beam (p     ) —low production rate o need target that can tolerate multi-MW beam —large energy spread and transverse phase space o need solenoidal focusing for the low energy portions of the facility –solenoids focus in both planes simultaneously o need emittance cooling o high-acceptance acceleration system and decay ring Muons have short lifetime (2.2  s at rest) —puts premium on rapid beam manipulations o high-gradient RF cavities (in magnetic field) for cooling o presently untested ionization cooling technique o fast acceleration system If intense muon beams were easy to produce, we’d already have them!

6. April 18, 2008MICE-FAC: Zisman6 Ionization Cooling (1) Ionization cooling analogous to familiar SR damping process in electron storage rings —energy loss (SR or dE/ds) reduces p x, p y, p z —energy gain (RF cavities) restores only p z —repeating this reduces p x,y /p z (  4D cooling) —presence of LH 2 near RF cavities is an engineering challenge o we get lots of “design help” from Lab safety committees!

7. April 18, 2008MICE-FAC: Zisman7 Ionization Cooling (2) There is also a heating term —for SR it is quantum excitation —for ionization cooling it is multiple scattering Balance between heating and cooling gives equilibrium emittance —prefer low   (strong focusing), large X 0 and dE/ds (H 2 is best) CoolingHeating

8. April 18, 2008MICE-FAC: Zisman8 Ionization Cooling (3) Merit factors for candidate MICE absorbers —scaled as equilibrium emittance o requirements for Al windows and extended absorber for H 2 and He degrade these ideal values by about 30% –H 2 remains best, even with windows included Material(dE/dx) min (MeV g -1 cm 2 ) X 0 (g cm -2 ) Relative merit Gaseous H 2 4.10361.281.03 Liquid H 2 4.03461.281 He1.93794.320.55 LiH1.9486.90.47 Li1.63982.760.30 CH 4 2.41746.220.20 Be1.59465.190.18

9. April 18, 2008MICE-FAC: Zisman9 System Description MICE includes one cell of the FS2 cooling channel —three Focus Coil (FC) modules with absorbers (LH 2 or solid) —two RF-Coupling Coil (RFCC) modules (4 cavities per module) Along with two Spectrometer Solenoids with scintillating fiber tracking detectors —plus other detectors for confirming particle ID and timing (determining phase wrt RF and measuring longitudinal emittance) o TOF, Cherenkov, Calorimeter

10. April 18, 2008MICE-FAC: Zisman10 MICE Cooling Channel Courtesy of S. Q. Yang, Oxford Univ. LH 2 absorbers Eight 201-MHz RF cavities

11. April 18, 2008MICE-FAC: Zisman11 MICE Stages Present staging plan

12. April 18, 2008MICE-FAC: Zisman12 Estimated Performance (1) Simulations of MICE performance carried out with several codes —nominal cooling performance estimated with ICOOL —full detailed simulations done with G4MICE Typical parameters —beam o momentum: 200 MeV/c (variable) o momentum spread:  20 MeV/c o  x,y ≈ 5 cm;  x’,y’ ≈ 150 mrad —channel o solenoid field: ≈ 3 T o   : 0.42 m o cavity phase: 90° (on crest)

13. April 18, 2008MICE-FAC: Zisman13 Estimated Performance (2) ICOOL simulation shows transverse emittance reduction of ≈10%

14. April 18, 2008MICE-FAC: Zisman14 Estimated Performance (3) Virtual scan over emittance used to determine equilibrium emittance —transmission is 100% for input emittance below 6  mm-rad o high emittance behavior reflects “scraping” as well as cooling

15. April 18, 2008MICE-FAC: Zisman15 RFCC Module Module comprises one coupling coil and 4 RF cavities —in advanced design stage —CC design and fabrication done in collaboration with ICST in Harbin, China o initial conductor order delivered —RF cavities will be similar to existing MuCool prototype o fabrication to get under way shortly

16. April 18, 2008MICE-FAC: Zisman16 ICST Coil Winding Facility De-spooling and Tensioning Apparatus Coil Winding Apparatus Winding a Copper Test Coil

17. April 18, 2008MICE-FAC: Zisman17 Winding banding Cooling Charging Winding coil Von Mises Stress in CC Stress and deflection calculations include the winding pre-stress in the coil and banding, which keeps the coil from lifting off the mandrel when it is fully charged to a current of 210 A. The minimum winding Pre-stress is 70 MPa. The aluminum banding pre-stress is 30 MPa.

18. April 18, 2008MICE-FAC: Zisman18 ICST Team Strong team available to work on CC

19. April 18, 2008MICE-FAC: Zisman19 MuCool Test Cavity Test cavity similar to MICE design has been fabricated —in place at Fermilab MTA —Be window design also successfully tested 42-cm

20. April 18, 2008MICE-FAC: Zisman20 Technology for MICE Cavity Local annealing of ports Extruded port Development of the technique Cavity ports being extruded (pulled) Power coupler and RF window

21. April 18, 2008MICE-FAC: Zisman21 FC Module Focus coil module vendor has been selected —contract award delayed until recently due to STFC funding woes —comprises two coils that can run with same or opposite polarity o 20-L LH 2 absorber (plus safety windows) fits inside

22. April 18, 2008MICE-FAC: Zisman22 LH 2 System LH 2 system design is based on using metal hydride bed as storage tank —R&D system being set up at RAL to test operation Design has passed two international safety reviews and is presently being fabricated in industry

23. April 18, 2008MICE-FAC: Zisman23 MuCool R&D (1) NFMCC’s MuCool program does R&D on cooling channel components in support of MICE —RF cavities, absorbers Carried out in MuCool Test Area (MTA) at Fermilab —located at end of 400 MeV linac and shielded for eventual beam tests

24. April 18, 2008MICE-FAC: Zisman24 MuCool R&D (2) Motivation for cavity test program: observed degradation in cavity performance when strong magnetic field present —201 MHz cavity easily reached 19 MV/m without magnetic field —initial tests in fringe field of Lab G solenoid now under way 201 MHz cavity 5-T solenoid + 805-MHz cavity 805 MHz results

25. April 18, 2008MICE-FAC: Zisman25 Test Setup at MTA The 805-MHz and 201-MHz cavities at MTA, FNAL for RF breakdown studies with external magnetic fields.The 805-MHz and 201-MHz cavities at MTA, FNAL for RF breakdown studies with external magnetic fields. 805 MHz pillbox cavity 201 MHz cavity

26. April 18, 2008MICE-FAC: Zisman26 Tests with Magnetic Fields Separation of the nearest curved Be window from the face of Lab-G magnet reduced from 110 to 10 cm Maximum possible magnetic field near the Be window ~1.5 T ( with 5 T in magnet) The 201-MHz cavity Lab-G magnet

27. April 18, 2008MICE-FAC: Zisman27 Initial Results First results indicate evidence for multipactor in presence of magnetic field —but, increase in dark current rate slower than expected o data still preliminary

28. April 18, 2008MICE-FAC: Zisman28 LH 2 System R&D at RAL Test system at RAL is presently under construction —intent is to validate the system and make it the “first article” (of 3) o both components and computer controls must be vetted

29. April 18, 2008MICE-FAC: Zisman29 Absorber Windows Required windows must be large (300 mm diameter), thin (~125  m) and strong (4x safety factor) Aluminum windows designed by Oxford and built at U.- Miss. —125  m; machined from single piece of Al —burst at 140 psi (nearly 10 atm)

30. April 18, 2008MICE-FAC: Zisman30 Future Activities RAL muon beam facility will continue to be valuable after MICE is completed —continuing to a 6D cooling demonstration is attractive option “Poor man’s” test of 6D cooling in MICE “Rich man’s” test of 6D cooling, e.g., FOFO snake, Guggenheim, HCC “HCC”

31. April 18, 2008MICE-FAC: Zisman31 International Perspective International community holds annual “NuFact” workshops —provides opportunity for physics, detector, and accelerator groups to plan and coordinate R&D efforts at “grass roots” level —venue rotates among geographical regions (Europe, Japan, U.S.) Year Venue 1999Lyon, France 2000Monterey, CA 2001Tsukuba, Japan 2002London, England 2003New York, NY 2004Osaka, Japan 2005Frascati, Italy 2006Irvine, CA 2007Okayama, Japan 2008Valencia, Spain

32. April 18, 2008MICE-FAC: Zisman32 Summary MICE is making excellent progress towards Phase II —design of coupling coils complete (ICST Harbin) o MOU between LBNL and HIT for fabrication in place —RF cavity design being finalized —focus coil module contract placed —LH 2 R&D system being prepared at RAL Fabrication of CC and FC getting under way —fabrication of RF cavities will begin shortly Strong R&D program under way to develop and test key components —RF, LH 2 absorbers We are looking forward to first ionization cooling measurements!

33. April 18, 2008MICE-FAC: Zisman33 Final Thought Challenges of a muon accelerator complex go well beyond those of standard beams —developing solutions requires substantial R&D effort to specify o expected performance, technical feasibility/risk, cost (matters!) Critical to do experiments and build components. Paper studies are not enough!