MCTF Muon Colliders m m Steve Geer SLACLBNL

MCTF Muon Colliders m + m Steve Geer SLAC/LBNL November, 2009 1

MCTF Physics Landscape Steve Geer SLAC/LBNL November, 2009 2

MCTF Decision Tree 0. 5 Te. V e+e 3 Te. V e+e- 3 -4 Te. V m+m- Pierre Oddone Steve Geer SLAC/LBNL November, 2009 3

MCTF Muon Collider Motivation Fits on laboratory site - MULTI-PASS ACCELERATION Cost Effective (e. g. 10 passes → factor 10 less linac) - MULTIPASS COLLISIONS IN A RING (~1000 turns) Relaxed emittance requirements & hence tolerances COST - NARROW ENERGY SPREAD Precision scans - TWO DETECTORS (2 IPs) - DTbunch ~ 10 ms … (e. g. 4 Te. V collider) Lots of time for readout Backgrounds don’t pile up - (mm/me)2 = ~40000 Enhanced s-channel rates for Higgs-like particles PHYSICS If we can build a multi-Te. V muon collider it’s an attractive option because muons don’t radiate as readily as electrons (mm / me ~ 207): - COMPACT Steve Geer SLAC/LBNL November, 2009 4

MCTF Muon Colliders are Compact 3 Te. V 0. 5 Te. V 4 Te. V Steve Geer SLAC/LBNL November, 2009 5

MCTF Narrow Energy Spread Shiltsev Beamstrahlung in any e+e- collider E/E 2 Steve Geer SLAC/LBNL November, 2009 6

MCTF Challenges Muons are born within a large phase space (p → mn) ● - To obtain luminosities O(1034) cm-2 s-1, need to reduce initial phase space by O(106) ● Muons Decay (t 0 = 2 ms) - Everything must be done fast → need ionization cooling - Must deal with decay electrons - Above ~3 Te. V, must be careful about decay neutrinos ! Steve Geer SLAC/LBNL November, 2009 7

MCTF Muon Collider Schematic Proton source: Upgraded PROJECT X (4 MW, 2± 1 ns long bunches) Steve Geer 1021 muons per year that fit within the acceptance of an accelerator SLAC/LBNL √s = 3 Te. V Circumference = 4. 5 km L = 3× 1034 cm-2 s-1 m/bunch = 2 x 1012 s(p)/p = 0. 1% b* = 5 mm Rep Rate = 12 Hz November, 2009 8

MCTF Target Facility Design • A 4 MW target station design study was part of “Neutrino Factory Study 1” in 2000 ORNL/TM 2001/124 V. Graves, ORNL • Facility studied was 49 m long = target hall & decay channel, shielding, solenoids, remote handling & target systems. • Target: liquid Hg jet inside 20 T solenoid, identified as one of the main Neutrino Factory challenges requiring proof-of-principle demonstration. 4 MW Target Station Design T. Davonne, RAL • Beam dump = liquid Hg pool. Some design studies started. Proton Hg Beam Dump Steve Geer SLAC/LBNL November, 2009 9

MCTF MERcury Intense Target Experiment (MERIT) • Proof-of-principle demonstration of a liquid Hg jet target in high-field solenoid ran at CERN PS in Fall 2007. • Successfully demonstrated a 20 m/s liquid Hg jet injected into a 15 T solenoid, & hit with a suitably intense beam (115 KJ / pulse !). • Results suggest this technology OK for beam powers up to 8 MW with rep. rate of 70 Hz ! 1 cm Hg jet in a 15 T solenoid Measured disruption length = 28 cm Steve Geer SLAC/LBNL November, 2009 10

MCTF Front-End Specifications p± → mn Parameter Drift Buncher Rotator Cooler Length (m) 56. 4 31. 5 36 75 Focusing (T) 2 2. 5 (ASOL) RF f (MHz) 360 240 202 201. 25 RF G (MV/m) 0 15 15 16 Total RF (V) 126 360 800 m/p within reference acceptance = 0. 085 at end of cooler → » 1. 5 1021 μ/year Steve Geer SLAC/LBNL November, 2009 11

MCTF Front-End Simulation Results Neuffer Steve Geer SLAC/LBNL November, 2009 12

MCTF Ionization Cooling Must cool fast (before muons decay) Muons lose energy by in material (d. E/dx). Re-accelerate in longitudinal direction reduce transverse phase space (emittance). Coulomb scattering heats beam low Z absorber. Hydrogen is best, but Li. H also OK for the early part of the cooling channel. Cooling Steve Geer Heating SLAC/LBNL November, 2009 13

MCTF Mu. Cool Developing & bench testing cooling channel components Mu. Cool Test Area at end of FNAL linac is a unique facility: -Liquid H 2 handling -RF power at 805 MHz -RF power at 201 MHz -5 T solenoid (805 MHz fits in bore) -Beam from linac (soon) New beamline MTA 42 cm Æ Be RF window Steve Geer Liq. H 2 absorber SLAC/LBNL November, 2009 14

MCTF RF in Magnetic Field: 805 MHz Results When vac. copper cavities operate in multi Tesla co-axial mag. field, the maximum operating gradient is reduced. Data reproducible & seem to follow universal curve. Possible solutions: -special surfaces (e. g. >2 X Reduction @ required field Peak Magnetic Field in T at the Window Steve Geer SLAC/LBNL beryllium) -Surface treatment (e. g. ALD) - Magnetic insulation Effect is not seen in cavities filled with high pressure hydrogen gas (Johnson & Derbenev) – possible solution (but needs to be tested in a beam – coming soon) November, 2009 15

MCTF MICE GOALS: Build a section of cooling channel capable of giving the desired performance for a Neutrino Factory & test in a muon beam. Measure performance in various modes of operation. m Multi-stage expt. enta m u r t Ins oling o C n izatio n o I tation n e m Ø Beam Line Complete Instru First stage being installed at purpose-built muon beam at RAL (first beam to hall March 2008). 10% cooling measured to ± 1%. Anticipate completed ~2011/12 Steve Geer tion Ø Spectrometer Solenoid being assembled SLAC/LBNL Ø Ø First Beam 3/08 Ø Running now PID Installed Ø CKOV Ø TOF Ø EM Cal First Spectrometer Ø Spring 2010 November, 2009 16

MCTF 6 D Cooling Palmer MC designs require the muon beam to be cooled by ~ O(106) in 6 D Ionization cooling reduces transverse (4 D) phase space. To also cool longitudinal phase space (6 D) must mix degrees of freedom as the cooling proceeds Alexhin & Fernow This can be accomplished with solenoid coils arranged in a helix, or with solenoid coils tilted. Steve Geer SLAC/LBNL November, 2009 17

MCTF 6 D Cooling Channel Scheme Palmer Steve Geer SLAC/LBNL November, 2009 18

MCTF 6 D Cooling Channel Development REQUIRES BEYOND STATE OF ART TECHNOLOGY → Ongoing R&D FOFO Snake - Alexhin Helical Cooling Channel- Muons Inc. Magnet development for 6 D cooling channels HCC magnet 4 coil test Steve Geer Detailed Simulations for candidate 6 D cooling schemes SLAC/LBNL November, 2009 19

MCTF Final Cooling When the emittance is very small, to continue cooling we need very high field solenoids (to continue winning against scattering) For fields up to ~50 T, the final luminosity is ~ prop-ortional to the solenoid field at the end of the channel. For higher fields we no longer expect to continue to win (limited by beam tune shift). Steve Geer SLAC/LBNL November, 2009 20

MCTF The Promise of HTS Steve Geer SLAC/LBNL November, 2009 21

MCTF HTS Solenoid R&D NHMFL test coil LBL Test Coil FNAL test cable. Test degradation of Jc in the cabling process Steve Geer SLAC/LBNL November, 2009 22

MCTF Acceleration MUON SURVIVAL FRACTION ● Early Acceleration Accelerating muons from 3 Ge. V to 2 Te. V (to 25 Ge. V ? ) could be the same as NF. 1. 0 Needs study. Bogacz ● Main Acceleration – 0. 8 0. 6 Example: TESLA cavities: Real estate gradient ~31 MV/m → 97% survival 0. 4 0. 2 0. 1 1 2 5 10 20 50 AVERAGE GRADIENT (MV/m) Steve Geer SLAC/LBNL Attractive Candidates - RLAs (extension of NF accel. scheme ? ) - Rapid cycling synchrotron – needs magnet R&D - Fast ramping RLA ● Options need study → particle tracking, collective effects, cavity loading, . . . November, 2009 23

MCTF Collider Ring • Muons circulate for ~1000 turns in the ring • Need high field dipoles operating in decay backgrounds → R&D DESIGN PROCESS • First lattice designs exist New ideas → conceptual designs for various options Comparison of different schemes, choice of the baseline Detailed lattice design with tuning and correction “knobs” WE ARE HERE Dynamic aperture studies with magnet nonlinearities, misalignments and their correction Transient beam-beam effect compensation Coherent instabilities analysis Steve Geer SLAC/LBNL November, 2009 24

MCTF Neutrino Radiation With L ~ E 2 → OK at √s = 1 Te. V OK at √s = 3 Te. V if D = 200 m Above 3 Te. V need to pay attention (wobble beam, lower b*, higher Bring , … ) Steve Geer SLAC/LBNL November, 2009 25

MCTF Background from Muon Decay Number of Decays 2 2 Te. V Collider m- → e - n e n m 2 x 1012 muons/bunch 2 x 105 decays/m Electron decay angles O(10) mrad Mean electron energy = 700 Ge. V Mean energy = 700 Ge. V 0 500 1000 1500 2000 Electron Energy (Ge. V) Steve Geer SLAC/LBNL As the decay electrons respond to the fields of the final focus system they lose 20% of their energy by radiating on average 500 synchrotron photons with a mean energy of ~500 Me. V … & are then swept out of the beampipe. November, 2009 26

MCTF Detector Backgrounds Muon Collider detector backgrounds were studied actively ~10 years ago (1996 -1997). The most detailed work was done for a 2 2 Te. V Collider → s=4 Te. V. Since muons decay (t 2 Te. V=42 ms), there is a large background from the decay electrons which must be shielded. The electron decay angles are O(10) microradians – they typically stay inside the beampipe for about 6 m. Hence decay electrons born within a few meters of the IP are benign. Shielding strategy: sweep the electrons born further than ~6 m from the IP into ~6 m of shielding. Steve Geer SLAC/LBNL November, 2009 27

MCTF Background Simulations • Shielding design group & final focus design group worked closely together & iterated • Used two simulation codes (MARS & GEANT), which gave consistent results • Shielding design & simulation work done by two experts (Mokhov & Stumer) in great detail, & involved several person-years of effort. Steve Geer SLAC/LBNL November, 2009 28

MCTF Final Focus Setup Fate of electrons born in the 130 m long straight section: 62% interact upstream of shielding, 30% interact in early part of shielding, 2% interact in last part, 10% pass through IP without interacting. Steve Geer SLAC/LBNL November, 2009 29

MCTF IP Region Steve Geer SLAC/LBNL November, 2009 30

MCTF More Shielding Details r=4 cm Designed so that, viewed from the IP, the inner shielding surfaces are not directly visible. Z=4 m Steve Geer SLAC/LBNL November, 2009 31

MCTF 4 Te. V Collider Backgrounds Results from Summer 1996 N. Mokhov MARS I. Stumer GEANT Background calculations & shielding optimization was performed using (independently) MARS & GEANT codes … the two calculations were in broad agreement with each other (although the designs were different in detail). Steve Geer SLAC/LBNL November, 2009 32

MCTF Particles/cm 42 from bunch Backgrounds with 2 1012 muons (2 Te. V) Te. Vone Collider GEANT (I. Stumer) Results from LBL Workshop, Spring 1997 r (cm) 5 2700 10 750 15 350 20 210 50 70 100 31 calo muon Steve Geer n 120 110 100 120 50 p p 0. 05 0. 9 0. 20 0. 4 0. 13 0. 08 0. 05 0. 04 0. 003 e 2. 3 m 1. 7 0. 4 0. 1 0. 02 0. 008 0. 003 0. 0003 SLAC/LBNL November, 2009 33

MCTF Occupancies in 300 x 300 mm 2 Pixels TOTAL Steve Geer CHARGED SLAC/LBNL November, 2009 34

MCTF Vertex Detector Hit Density Consider a layer of Silicon at a radius of 10 cm: GEANT Results (I. Stumer) for radial particle fuxes per crossing: 750 photons/cm 2 2. 3 hits/cm 2 110 neutrons/cm 2 0. 1 hits/cm 2 1. 3 charged tracks/cm 2 1. 3 hits/cm 2 TOTAL 3. 7 hits/cm 2 0. 4% occupancy in 300 x 300 mm 2 pixels MARS predictions for radiation dose at 10 cm for a 2 x 2 Te. V Collider comparable to at LHC with L=1034 cm-2 s-1 At 5 cm radius: 13. 2 hits/cm 2 1. 3% occupancy For comparison with CLIC (later) … at r = 3 cm hit density about × 2 higher than at 5 cm → ~20 hits/cm 2 → 0. 2 hits/mm 2 Steve Geer SLAC/LBNL November, 2009 35

MCTF Pixel Micro-Telescope Idea S. Geer, J. Chapman: FERMILAB-Conf-96 -375 Photon & neutron fluxes in inner tracker large but mean energies O(Me. V) & radial fluxes ~ longitudinal fluxes ( isotropic) Clock 2 layers out at variable clock speed (to maintain pointing) & take coincidence. Blind to soft photon hits & tracks that don’t come from IP Steve Geer SLAC/LBNL November, 2009 36

MCTF Pixel Micro-Telescope Simulation - 1 Steve Geer SLAC/LBNL November, 2009 37

MCTF Pixel Micro-Telescope Simulation - 2 Steve Geer SLAC/LBNL November, 2009 38

MCTF TPC V. Tchernatine Exploit 10 ms between crossings Large neutron flux – gas must not contain hydrogen: 90% Ne + 10% CF 4 Vdrift = 9. 4 cm/ms with E = 1500 V/cm. Ion buildup DE/E = 0. 7% Cut on pulse height removes photon & neutron induced recoils Steve Geer SLAC/LBNL November, 2009 39

MCTF Calorimeter Backgrounds Electromagnetic: Consider calorimeter at r=120 cm, 25 r. l. deep, 4 m long, 2 2 cm 2 cells: GEANT 400 photons/crossing with <E > ~1 Me. V <ETower>~400 Me. V s. E ~ (2<n >) <E > = 30 Me. V For a shower occupying 4 towers: <E> = 1. 6 Ge. V and s. E = 60 Me. V Hadronic: Consider calorimeter at r=150 cm, 2. 5 m deep (~10 l), covering 30 -150 degrees, 5 5 cm 2 cells: <ETower> ~ 400 Me. V s. E ~ (2<n >) <E > = O(100 Me. V) These estimates were made summer 1996, before further improvements to final focus + shielding reduced backgrounds by an order of magnitude … so guess background fluctuations reduced by 3 compared with above. Steve Geer SLAC/LBNL November, 2009 40

MCTF Bethe-Heitler Muons ( Z Zm+m-) Special concern: hard interactions (catastrophic brem. ) of energetic muons travelling ~parallel to the beam, produced by BH pair production. Believe that this background can be mitigated using arrival-times, pushing calorimeter to larger radius, & spike removal by pattern recognition … but this needs to be simulated Steve Geer SLAC/LBNL November, 2009 41

MCTF Comparison with CLIC • We are not yet in a position to make an apples-to-apples comparison with CLIC, but …. . FROM CLIC Machine. Detector interface studies: hits/mm 2/bunch train NOT AN APPLES-to. APPLES COMPARISON … BUT … Background hit densities appear to be similar to MC … so there may be many detector design issues in common between the 2 machines Note: CLIC shielding cone = 7 o c. f. 20 o for MC (but we hope to improve on this) Steve Geer CLIC 30 mm O(1) hit/mm 2/bunch train SLAC/LBNL November, 2009 42

MCTF MC R&D – The Next Step • In the last few years MC-specific R&D has been pursued in the U. S. by Neutrino Factory & Muon Collider Collaboration (NFMCC) & Muon Collider Task Force (MCTF) • Last December the NFMCC+MCTF community submitted to DOE a proposal for the next 5 years of R&D, requesting a greatly enhanced activity, aimed at proving MC feasibility on a timescale relevant for future decisions about multi-Te. V lepton colliders. Steve Geer SLAC/LBNL November, 2009 43

MCTF NFMCC/MCTF Joint 5 -Year Plan ● Deliverables in ~5 years: -Muon Collider Design Feasibility Report - Hardware R&D results → technology choice - Cost estimate - Also contributions to the IDS-NF RDR ● Will address key R&D issues, including - Maximum RF gradients in magnetic field - Magnet designs for cooling, acceltn, collider - 6 D cooling section prototype & bench test - Full start-to-end simulations based on technologies in hand, or achievable with a specified R&D program ● Funding increase needed to ~20 M$/yr (about 3 x present level); total cost 90 M$ Steve Geer SLAC/LBNL November, 2009 44

MCTF R&D – Ongoing NFMCC/MCTF HISTORY & FUTURE PROPOSAL Steve Geer SLAC/LBNL November, 2009 45

MCTF Anticipated Progress NOW 5 YEARS s el d o m nt e n po om yc e K Steve Geer SLAC/LBNL November, 2009 46

MCTF Aspirational Bigger Picture Steve Geer SLAC/LBNL November, 2009 47

MCTF Muon Collider R&D: A National Program Steve Geer SLAC/LBNL November, 2009 48

MCTF Final Remarks • Steady progress on the Front-End development for Muon Colliders - Cooling channel design concepts - NF R&D (IDS-NF, MERIT, MICE, … ) • The time has come to ramp up the Muon Collider specific R&D → a National Program • There are many challenges to be overcome - RF in magnetic fields & 6 D Cooling Channel - Cost effective acceleration scheme - Collider Ring - Detector/Backgrounds optimization • The incentive to meet these challenges is great → “ 5 Year Plan” → Design Feasibility Study Steve Geer SLAC/LBNL November, 2009 49

MCTF Illustrative Staging Scenario 4 MW multi-Ge. V Proton Source Accumulation & Rebunching 3 a b 4 Ge. V NF 25 Ge. V NF 4 Steve Geer CERN Neutrino Workshop October 1 -3, 2009 50

MCTF Muon Collider Parameters Steve Geer SLAC/LBNL November, 2009 51