Katsuya Yonehara Accelerator Physics Center, Fermilab On behalf of the Muon Accelerator Program 5/22/121International Particle Accelerator Conference, K. Yonehara

5/22/12International Particle Accelerator Conference, K. Yonehara2  Compact  Low synchrotron radiation  Multi-pass acceleration  Multi-pass collisions in ring  Possible to fit a Multi-TeV CoM machine at Fermilab  Energy frontier lepton collider  Full √s is available to generate particle

5/22/12International Particle Accelerator Conference, K. Yonehara3

5/22/12International Particle Accelerator Conference, K. Yonehara4 Project X Accelerate Hydrogen ions to 8 GeV using SRF technology. Compressor Ring Reduce size of beam (2±1 ns). Target Collisions lead to muons with energy of about 200 MeV. Muon Capture and Cooling Capture, bunch and cool muons to create a tight beam. Initial Acceleration In a dozen turns, accelerate muons to 20 GeV Recirculating Linear Accelerator In a number of turns, accelerate muons up to Multi-TeV using SRF techlnology. Collider Ring Bring positive and negative muons into collision at two locations 100 meters underground.

 Compact  Low synchrotron radiation  Multi-pass acceleration  Multi-pass collisions in ring  Possible to fit a Multi-TeV CoM machine at Fermilab  Energy frontier lepton collider  Full √s is available to generate particle 5/22/12International Particle Accelerator Conference, K. Yonehara5  Small energy spread at interaction region  No beamstrahlung effect  δE/E ≤ 10 -3

5/22/12International Particle Accelerator Conference, K. Yonehara6 Beamstrahlung is intrinsic to any e+e- collider

5/22/12International Particle Accelerator Conference, K. Yonehara7 ParameterUnitValue Center of mass energyTeV1.53 Luminosity10 34 cm -2 s Beam-beam tune shift0.087 Muons per bunch Muon power (both beams)MW Normalized rms emittance ε x,y mm mrad25 Normalized rms emittance ε z mm mrad72,000 Repetition rateHz1512 Proton driver powerMW43.2 “Muon Collider and Neutrino Factory”, ICFA Beam Dynamics Newsletter

 Muons are produced as tertiary particles 5/22/12International Particle Accelerator Conference, K. Yonehara8 Need new accelerator technology R&D μ ν ν e μ p π  Muons decay  Muons are born within a large 6D phase space e.g. Hg jet Target  Need a MW-scale proton source & target  Everything must be done fast  Need to deal with decay electron  Need to cool them by O(10 6 ) before they decay

5/22/12International Particle Accelerator Conference, K. Yonehara9 The mission of the US Muon Accelerator Program (MAP) is to develop and demonstrate the concepts and critical technologies required to produce, capture, condition, accelerate, and store intense beams of muons for Muon Colliders and Neutrino Factories. The goal of MAP is to deliver results that will permit the high-energy physics community to make an informed choice of the optimal path to a high-energy lepton collider and/or a next-generation neutrino beam facility. Coordination with the parallel Muon Collider Physics and Detector Study and with the International Design Study of a Neutrino Factory will ensure MAP responsiveness to physics requirements.

5/22/12International Particle Accelerator Conference, K. Yonehara10 1.Demonstrate the feasibility of key concepts that would allow us to build a multi-TeV collider 2.Continue to develop the critical elements of the NF and MC designs 3.Support the ongoing accelerator R&D and concept demonstration program 4.Establish close coordination with the detector and HEP experimental community 5.As able, continue to support fundamental technical development in the field that has the potential to contribute significantly to the machine design Overarching goal during this phase of the program is to Establish Conceptual Feasibility Overarching goal during this phase of the program is to Establish Conceptual Feasibility

5/22/12International Particle Accelerator Conference, K. Yonehara11  Proton driver  π production target  Capture/Decay/Buncher  Muon beam cooling  Accelerator  Collider ring  Collider detector  Physics One of the most critical R&D items determines the achievable parameters for a Muon Collider In the rest of this presentation, we will discuss > 55 contributions for IPAC’12 from MAP

 Cool beam phase space by ionization energy loss  Like synchrotron radiation and electron cooling  But fast cooling because of large energy loss rate passing through material  Single pass cooling channel  Not yet experimentally validated 5/22/12International Particle Accelerator Conference, K. Yonehara12

5/22/12International Particle Accelerator Conference, K. Yonehara13 μ beam Absorber RF cavity Solenoid magnet coil Longitudinal momentum is restored by RF cavity RF cavities are embedded in Multi-Tesla magnetic field Beam envelope Achievable transverse emittance is determined by focusing strength and material property Strong magnetic field RF field direction Transverse momentum phase space before cooling Transverse momentum phase space after cooling Condition of momentum phase space in cooling channel

5/22/12International Particle Accelerator Conference, K. Yonehara14 RF cavity 4T Spectrometer LH2 absorber 4T Spectrometer Scintillating fiber tracker LH2 absorber 201 MHz RF cavity TOF & Calorimeter are not shown in below picture Validate an Ionization Cooling Channel

5/22/12International Particle Accelerator Conference, K. Yonehara15 Length of IC (Ionization Cooling Channel) required reduction as a function of the RF acceleration gradient Performance is determined by RF gradient

5/22/12International Particle Accelerator Conference, K. Yonehara16 Peak RF gradient in MV/m Peak Magnetic Field in T at the Window >2X less gradient than desired Data were taken in an 805 MHz vacuum pillbox cavity

5/22/12International Particle Accelerator Conference, K. Yonehara17 Accelerating field on axis (MV/m) Y= X Intensity (mRem/Hr) Concentration of dark current by magnetic field in the MTA 805 MHz Vacuum RF button cavity Higher current intensity in stronger magnetic field

5/22/12International Particle Accelerator Conference, K. Yonehara18 Maximum electric field gradient in HPRF test cell Schematic view of HPRF test cell High Pressure RF (HPRF) cavity has been successfully operated in strong magnetic fields Use Hydrogen gas to use as ionization cooling material Metallic breakdown Gas breakdown: Linear dependence Governed by electron mean free path Gas breakdown Operation range for muon cooling P. Hanlet et al., Proceedings of EPAC’06, TUPCH147 Metallic breakdown: Plateau Depend on electrode material No detail study have been made yet

5/22/12International Particle Accelerator Conference, K. Yonehara19 Dense hydrogen gas Beam-induced plasma Muon beam Beam-induced plasma formed in GH2 Plasma is drifted by RF E field Absorb RF power Beam on Observed beam-induced plasma loading effect with 400 MeV proton beam RF envelope w/o beam RF envelope w beam Add small amount of electronegative gas (SF6, O2, etc) Ionized electrons disappear Still positive ions (mainly ionized hydrogen) consume RF power Pure GH2 1% Dry Air (0.2 % O2) in GH2 1% Dry Air (0.2 % O2) in GH2 at B = 3 T Inject either proton or muon electron Positive ion E 0 = 25 MV/m ~50 times diffrent RF dissipation

5/22/12International Particle Accelerator Conference, K. Yonehara20 1 % Dry Air doped 100 atm He gas 1 % Dry Air doped 100 atm H2 gas 0.01 % SF6 doped 100 atm H2 gas 1 % Dry Air doped 50 atm N2 gas Observed RF power dissipation per single electron-ion pair (dw) 34 atm pure H2 gas ~50 times diffrent RF power dissipation

5/22/12International Particle Accelerator Conference, K. Yonehara μ ± × 12 bunches = μ ± per one bunch train in 60 ns Designed μ beam parameter in cooling channel for MC Each μ produces ~2,000 electron-ion pairs/cm in 200 atm GH2 Plot shows the estimated RF amplitude reduction (only due to beam-Induced plasma loading effect) Pure 200 atm GH2 0.2 % O2 doped 200 atm GH2 E 0 = 16 MV/m for Helical cooling channel Ne = electrons/cm 3 !! << No2 = O2/cm 3 (0.2 % O2) 2 orders of magnitude larger # of O2

 New Result: Demonstration of high-gradient of cavity in high-pressure gas  Operated in intense proton beam at Mucool Test Area in Fermilab  Understood beam-induced plasma dynamics  Beam-induced plasma loading can be managed with electronegative dopant  Gas Filled RF cavity can be a potential solution for muon accelerator 5/22/12International Particle Accelerator Conference, K. Yonehara22

5/22/12International Particle Accelerator Conference, K. Yonehara23 Thank you

5/22/12International Particle Accelerator Conference, K. Yonehara24 Compressor + refrigerator room Entrance of MTA exp. hall MTA exp. hall SC magnet 200 MHz cavity Magnet + HPRF cavity 400 MeV H - beam transport line Multi task work space to study RF cavity under strong magnetic fields & by using intense H - beams from Linac

Plot maintained by Peter Lee at: HTS can now enable a new generation of magnets - > 30 Tesla J E floor for practicality 5/22/1225International Particle Accelerator Conference, K. Yonehara

5/22/12International Particle Accelerator Conference, K. Yonehara26 1.Longitudinal phase rotation 2.6D cooling channel 3.Final cooling channel 4. (Optional) Extra cooling 5.(Optional) Final cooling channel.