FNAL Feasibility Study on a Neutrino Source Based on a Muon Storage Ring

1. FNAL Feasibility Study on a Neutrino Source Based on a Muon Storage Ring Norbert Holtkamp Fardog Summary, Jan. 6th ‘00 • Results from recent technical discussions • some nice technical solutions • some results with impact on the physics study • Status of the study • Timing

2. The Task • A design concept for a muon storage ring and associated support facilities that could, with reasonable assurance, meet performance goals required to support a compelling neutrino based research program. • 2.Identification of the likely cost drivers within such a facility. • 3.Identification of an R&D program that would be required to address key areas of technological uncertainty and cost/performance optimization within this design, and that would, upon successful completion, allow one to move with confidence into the conceptual design stage of such a facility. • 4.Identification of any specific environmental, safety, and health issues that will require our attention.

3. Choice has been made ! • Basic Calculation • 1/3 of the muons decay in the straight section (38 %) • 10 protons for 1 m into the storage ring (>10; >20-50) • 2x107 sec • 2x1013 proton on target per pulse @ 16 GeV and 15 Hz • 3x1013 proton because of carbon target • 2x1012m per pulse to be accelerated and injected into the ring • cooling channel not successfully simulated < 2x1012 • longer bunch in the proton driver and on target (1 nsec  3) • helps • ring tilt angle is 13deg ( 22 %) instead of 35 deg (57 %) • ring with these params. Is not a cost driver at all

4. The Neutrino Source • Approach: • go more conventional where ever possible • Oak Ridge, FHML, Brookhaven  the target • most people bought the solid target • Jefferson Lab / Cornell  sc rf and re-circulating linacs • biggest disconnect right now • LBNL , DUBNA  induction linacs (talk tomorrow) • goes much better than expected but not cheap • IHEP Protvino sc solenoid channels • so far very good job • specific design and engineering (cooling channel, target collection, beam manipulation, beam tracking and simulation)  Muon Collider group (12 people @FNAL) + the collaboration • ( thank Andy for the enormous support) • general engineering (large scale rf systems, sc magnets, sc solenoid channels, ps, vacuum, beam lines, tunnel, water)(20 FTE for 6 month) • very good support from FESS and TD • not easy to convince somebody in BD that anything else than TEVATRON is useful at all.

5. The Neutrino Source • First experiment based on an intense muon source -> does it have to be 50 GeV ?? • 10 GeV and 50 kT or more magnetized water detector: Goal: Balance detector cost with Accelerator: E*kT*I=const. • Start with 2x1019/year (Sessler, Geer) and still good physics

6. Neutrino Source Study @ FERMI • Application of a “Generic Neutrino Source” to specific site • Base the study on specific set of Parameters • 6 month period of time to define the R&D program and develop a layout to investigate the scope of such a complex Generic Layout collaboration paper “deviate wherever necessary or useful” Physics Study in parallel H. Schellmann / S. Geer

7. Footprint for a 50 GeV Neutrino Source • Infrastructure is very close together ...

8. R & D Issues for the Proton Driver Design Study • R & D groups: • Goal: • 4 x 0.75x 10-13 = 3x 10-13 @ 15 Hz • 8 GeV versus 16 GeV versus higher energies ? • Very hard to get people going on this: Only Chuck A. • Will probably not appear in the report in detail • Why? • Power bill is dominated acceleration • at low Frequ. Tfill is large compared to T pulse • most of the time power source is on for filling • -> higher rep rate less efficient; peak current is limit too. • Go to higher energies (more acceleration): Higher Proton beam energy and smaller rep rate is more efficient way to produce beam power

9. What changes compared to MC • The target • Ptarget is still of the order of 1.5 (graphite) with upgrade possibility to 4 MW (probab. Liquid) • RF after target only gives increase in Polarization from 28% to 40% -> it is not worth it !! A. Blondel from CERN • Target dissipation is only 30 kW or so -> radiation cooled • Radiation damage is a major constraint for sc coil. 0.5 - 1 year is most probable lifetime so far • 20 T can only be achieved with sc +nc coil. • Disagreement between people on the fatigue limits calculated and the actually NuMI test. 30 - 60 MHz rf ~ 5 MV/m

10. Target for a Neutrino Factory • 1 - 2 MW target • Reduce power in the target -> low Z • Solid Target: loose x 1.5 in yield -> more protons -> ok at this intensity • Magnet radius is too small, especially with Copper inside

11. Induction Linacs and Long Solenoidal Channels 50 m drift before f rotation For carbon target: 0.10 m/p between 225 - 240 MeV 0.13 m/p between 220 - 250 MeV 0.18 m/p between 200 - 270 MeV • Trade off: • Energy Spread after rotation drift channel length[loss] • Particle capturelength(voltage) in induction linac[loss] •  simplest solution offers comparable yield

12. Induction Linac Layout • Strong Effort at LBL for DAHRT • A little bit of expertise at Fermi • higher field 2-3 T and smaller cores may be better solution • saturation in the cores is under control • switching is the main problem Small effort at FNAL: “old” expert from DUBNA no working in TD. Mainly on solenoid channel design

13. LBNL Status • Induction Cell • basically ok. Trade off between: operational and investment cost • Pulser system: • still not so clear: 4 pulse per burst… • asymmetric voltage

14. The Heart of the Cooling Channel for a Neutrino Factory • IIT, BNL, LBNL, FNAL: go through an engineering design faster • Goal: Do all the cooling with one set of hardware RF may be, solenoids no • Analytical (Courant Snyder type description of the motion in Solenoidal channel) LBL Bz ~ 5 T max Eacc ~ 15 MV/m @ 200 MHz

15. The Cooling Channel • +/- 3.5 T up to 5T or more Lattice with 15 MV/m 175 MHz rf • period gets shorter and shorter Reduces to about 100-140 m of cooling channel

16. 200 MHz Cavity + Power Source • Engineering Layout required for the study • Want to build and test it, once study is done 1/8th of the full accelerating cell ~ 0.65 m Enhance the E Field on Axis by using a grid Goal: 15 MV/m nc cavities ~ 0.65 m

17. Acceleration based on RLA • Why not nc? • Peak power limited already • in normal conducting cavity: too much power required to build up the gradient • gradient is not a free parameter for optimization: • muon decay +longitudinal acceptance • SC structures at 200 MHz (100 MHz) and 10 MV/m (7,5 MV/m real estate) • almost no power to build up gradient --> beam • loaded Q’s are similar to nc structures ->fill time short but coupler ? -> comparatively efficient ! • 4 x 30 bunches per RLA, 2.5x1012 total • Plinac ~ 6 MW, PRLA1 ~ 2 MW, PRLA2 ~ 12 MW • ~20 MW power for RF acceleration at ~25 % overall efficiency (AC  RF) • Problem is the required peak power not average power !

18. Optimization of the Storage Ring • The cheapest way to produce muons in the straight section is to make them as long as possible ! Nr of m decaying in straight section h = Nr of m injected 1 1 h = = L=length of straight 2 (1+p r /L) 2 (1+0.2) B / Tesla • Problem with dynamic aperture due to short Magnets and large aperture (10x15 cm) -> not fixed yet

19. The SC Large Bore Magnets • Low field quality helps reduce price although large aperture • main heat load due to m-decay, probably not optimum • 1 cm tungsten liner instead of 3 cm

20. Large Bore Magnets • Similar magnets for the RLA Arcs with less tungsten shielding • Bigger magnets in the Beam Spreaders of the RLA arcs + combined function • Energy Acceptance of the Arcs ?????? Storage Ring Arc Cell

21. The Storage Ring Location@ FNAL

22. Storage Ring Layout • Site layout for the Storage Ring and the Arcs • Experimental beam lines and halls • Cryo space requirement

23. Goal & Schedule • 6 Month study:  “10 pages of paper per subsystem+ 1 schedule + 1 cost” • Internal Review Feb. 15th and 16th for the Accelerator part, Feb. 17th and 18th for Geer/Shellman to align the different contributions • Documents in by beg. of march • Report out by March 30th if that’s acceptable • Most risky • induction linac (no, only expensive ->R&D) • cooling channel design and performance • what is the minimum emittance achievable • it is still the most unreliable item • acceleration: ( largest cost driver) • Jefferson Lab  Cornell CERN  SLAC  Fermi • after Feb. 15th & 16th have working meeting with these groups to go through: Cryo, cavities, couplers and power sources • not sop clear how to organize it

24. Cost • Hot Topic: Preliminary result.

25. Questions • What comes after the study ? • Review the results • Does the lab want to do this ? • If done or obvious: Define the R & D program • remember: 10 different subsystem and all need strong R&D program … a lot of people, time and money. • Develop efficient and cost effective accelerating systems at low frequency • Prepare a site where this experimental program can be pursued • leading role for Muon Cooling Directors office