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Muon Collider & Ionization Cooling Issues Y. Alexahin

FERMI NATIONAL ACCELERATOR LABORATORY US DEPARTMENT OF ENERGY. f. Muon Collider & Ionization Cooling Issues Y. Alexahin. FNAL Accelerator Advisory Committee meeting December 5, 2006. Plan of the talk. Overview of basic ideas low emittance MC 6D ionization cooling

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Muon Collider & Ionization Cooling Issues Y. Alexahin

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  1. FERMI NATIONAL ACCELERATOR LABORATORY US DEPARTMENT OF ENERGY f Muon Collider & Ionization Cooling Issues Y. Alexahin FNAL Accelerator Advisory Committee meeting December 5, 2006

  2. Plan of the talk • Overview of basic ideas • low emittance MC • 6D ionization cooling • PIC and REMEX • Ongoing work • Questions to answer • FY07 plan • FY08 plan and beyond • Summary Muon Collider & Ionization Cooling Issues - Y. Alexahin, FNAL December 5, 2006

  3. Muon Collider parameters • Low emittance option (advanced): owing to ideas by Yaroslav Derbenev (HCC, PIC) much lower 6D emittances seem to be feasible than previously thought of. • High emittance option (baseline):conceptuallyfollows1999 PRSTAB Muon Collider Collaboration report Low Emitt.High Emitt. Energy (TeV) 0.75+0.75 (=7098.4) Average Luminosity (1e34/cm^2/s) 2.7 1 Average bending field (T) 10 8.33 Mean radius (m) 361.4 363.8 Number of IPs 4 (350m/2 each) 2 (200m each) P-driver rep.rate (Hz) 65 60 Beam-beam parameter/IP,  0.052 0.1  (cm) 0.5 3 Bunch length (cm), z 0.5 2 Number of bunches/beam, nb 10 1 Number of muons/bunch (1e11), N 1 12 Norm.transverse emittance (m), N 2.1 13 Energy spread (%) 1 0.1 Norm.longitudinal emittance (m), ||N 0.35 0.14 Total RF voltage (GV) at 800MHz 406.6 103c 0.26103c RF bucket height (%) 23.9 0.6 Synchrotron tune 0.723 103c 0.02103c + - in collision / proton 0.15 /2 0.15 8GeV proton beam power (MW) 1.1 0.6 Muon Collider & Ionization Cooling Issues - Y. Alexahin, FNAL December 5, 2006

  4. Low emittance option for MC f z /  “Hourglass factor” • Low emittancepros: • smaller  → smaller total number of particles nbN → •  relaxed coherent stability requirements •  low proton driver power •  low neutrino radiation • Low emittancecons: • bb-effect limits N → larger nb is required → electrostatic separation or crossing angle • smaller  → strong IR chromaticity • → smaller z is required → •  small c → strong arc cell chromaticity •  higher p/p for the same long. emittance problems with momentum acceptance Muon Collider & Ionization Cooling Issues - Y. Alexahin, FNAL December 5, 2006

  5. The roadmap to low emittance Ionization cooling: very similar to SR cooling in e-damping rings Thelongitudinal damping partition numberisnaturally negative at p  <300MeV/c: How to make it positive – see next slide. Thenormalized equilibrium emittance(r.m.s.) (overestimation for H and He) With Z=4 (Be) and the natural value of g||<0 (the final cooling stage) so that to achieve =2m<0.2mm is required (for 1). Is it feasible? Another possibility (D.Neuffer): decelerate muons to very low . Muon Collider & Ionization Cooling Issues - Y. Alexahin, FNAL December 5, 2006

  6. Basic 6D Cooling • Two ways to get g||>0: • generate large dispersion and use wedge absorbers; • generate large momentum compaction c >0 in a homogeneous absorber • The first method is realized in two schemes: • "Guggenheimed" RFOFO channel (helical or spiral with reducing radius), estimated emittances N~5102m, || N~1mm • straight FOFO channel with tilted solenoids, N~5102m, || N~0.5mm • The second method in: • Helical Cooling Channel (HCC) , N~2102m, || N ~0.3mm; • HCC is the most attractive scheme, however, it has inherent difficulties Muon Collider & Ionization Cooling Issues - Y. Alexahin, FNAL December 5, 2006

  7. PIC & REMEX • Basic idea of the Parametric resonance Ionization Cooling (Y. Derbenev): • form a structure with ~180 phase advance/cell • resonantly excite beta-beating with special lenses to obtain very small  at absorber plates Lattice magnets and RF cavities not shown • Reverse EMittance EXchange: • obtain very small  as described above • enhance transverse damping by making g|| <0 as large by the absolute value as possible by reversing the wedge angle and generating maximum dispersion at the wedges Muon Collider & Ionization Cooling Issues - Y. Alexahin, FNAL December 5, 2006

  8. “Guggenheim” RFOFO structure (R.Palmer) - modification of the initially proposed by V.Balbekov RFOFO ring Muon Collider & Ionization Cooling Issues - Y. Alexahin, FNAL December 5, 2006

  9. “Guggenheim” RFOFO cooling simulations (R.Palmer, A.Klier) • Adding 804 MHz section would allow to achieve N~7.5102m , but: • no matching section designed yet (may further increase losses surpassing 50% already) • high magnetic field may drastically limit RF voltage (would GH2 filling help?) • shown reduction in emittances include both cooling and initial shaving • the merit factor of the 2-stage RFOFO channel is just (N /6D)fin/ (N /6D)ini = 800 Muon Collider & Ionization Cooling Issues - Y. Alexahin, FNAL December 5, 2006

  10. HCC Simulations (K.Yonehara) • Initial proposal: • RF cavities packed inside solenoid • additional helical coils create rotating dipole and quadrupole fields • As R.Palmer noted the transverse field on the coils would exceed 103T at the last stage! 6D cooling factor in the series of HCC is ~50,000 Muon Collider & Ionization Cooling Issues - Y. Alexahin, FNAL December 5, 2006

  11. HCC issues Vladimir Kashikhin found a brilliant solution: helical solenoid! Magically, the dipole and quadrupole components have the right values, while the orbit goes through the centers of the coils! • Still a number of problems to be solved: • how far down this helix can be scaled? Is helix period of ~ 20cm (with Bs~15T) technically feasible? • a principal solution for the RF structure which can fit inside the HCC has yet to be found; • segmented HCC with RF cavities between solenoid sections was proposed but not demonstrated to provide adequate cooling Muon Collider & Ionization Cooling Issues - Y. Alexahin, FNAL December 5, 2006

  12. REMEX with HTS solenoids (R.Palmer) It is possible to obtain N~10 m in a solenoidal focusing channel with LH2 absorber: Simulations of cooling in a channel with 6 solenoids (no RF yet) gave N=25 m . To achieve emittances for the low emittance MC option this channel must be followed by a stronger focusing channel with short solid absorbers. Muon Collider & Ionization Cooling Issues - Y. Alexahin, FNAL December 5, 2006

  13. Mixed Lattice for PIC/REMEX channels (A.Bogacz) absorber 10T solenoid quads dipoles This mixed quadrupole-solenoid focusing lattice provides  =1.4cm at the absorber center. Large dispersion function gives the possibility of chromatic correction (not demonstrated yet). By reducing dimensions and increasing field strength one may hope to get  in the mm range. Muon Collider & Ionization Cooling Issues - Y. Alexahin, FNAL December 5, 2006

  14. Questions to answer • Collider ring: • correction of chromatic perturbations (chromatic beta-beating, nonlinear chromaticity and momentum compaction factor); • radiation shielding necessary to protect the superconducting magnets and detectors at specific for the particular design beam intensity and sizes ; • field quality of the magnets which have the required aperture and field strength (magnets being developed for the LHC luminosity upgrade is a good first approximation); • dynamic aperture with realistic field and alignment errors; • beam-beam effects; • suppression of coherent instabilities at given bunch intensity, length, momentum compaction and lattice functions. • 6D cooling channel: • scalability of the proposed by V.Kashikhin HCC technical solution to the helix period of ~ 20cm (with Bs~15T); • principal solution for the RF structure which can fit inside the HCC; Muon Collider & Ionization Cooling Issues - Y. Alexahin, FNAL December 5, 2006

  15. Questions to answer • 6D cooling channel (continued) • ability of gas-filled cavities to support high-gradient RF field in the presence of ionizing beam; • end-to-end simulation of the "Guggenheimed" RFOFO channel to prove its competitiveness; • proof-of-principle study of the FOFO channel with tilted solenoids followed by cooling simulations. • PIC / REMEX • optics design for different stages (solenoidal vs quadrupole and mixed focusing) • compensation of chromatic and spherical aberrations; • space charge effects • Proton driver, Pion production, Muon RF capture, Bunch coalescing, Acceleration • There is little doubt in feasibility of these elements of the complex, • there are a number of options for each of them which should be studied and compared, • but only after the principal solution for the collider ring and the cooling channel is chosen. Muon Collider & Ionization Cooling Issues - Y. Alexahin, FNAL December 5, 2006

  16. FY07 plan • Physics analysis and computer simulations of different schemes for the basic 6D cooling channel and PIC/REMEX channel. • Side-by-side comparison of the obtained results with the aim of choosing the 6D cooling channel baseline scheme compatible with the chosen collider option. • Analysis of implications of different options for the muon collider (low emittance vs. high emittance, electrostatic separation in one ring vs. double ring) resulting in a presumably optimal choice of parameters. • Collider ring optics design for the chosen option. • Preliminary analysis of the technical feasibility and physical validity of the proposed design (momentum acceptance, medium-term dynamic aperture, coherent stability). • Formulating requirements to the proton driver and other systems of the complex. • Consistent scheme(s) of the muon collider complex. Muon Collider & Ionization Cooling Issues - Y. Alexahin, FNAL December 5, 2006

  17. FY08 plan and beyond • Upgrade of the muon production and RF capture systems design • Analysis, selection and preliminary design of muon acceleration systems (RLA vs. FFAG for the first stage, RLA vs. fast ramping synchrotrons for subsequent stages) • Extensive simulation studies and design optimization of all essential systems of the collider complex. • Analysis of radiological issues for appropriate choice of the collider orientation and depth • Cost estimates • Draft conceptual design report • Optimistically, the conceptual design will be finished in 2009 Muon Collider & Ionization Cooling Issues - Y. Alexahin, FNAL December 5, 2006

  18. Summary • The Muon Collider for c.o.m. energy 1.5-2TeV seems doable with present day technology and can be accomodated on the Fermilab site • Extensive design and simulation work is necessary for all parts of the complex with the 1999 PRSTAB Muon Collider Collaboration report being a good first approximation • The requested funding for this work seems adequate taking into account heavy contribution from other labs especially BNL, JLab and MuonsInc. Muon Collider & Ionization Cooling Issues - Y. Alexahin, FNAL December 5, 2006

  19. Backup slides – Emittance diagram Emittance evolution in R.Palmer’s muon cooling scheme Muon Collider & Ionization Cooling Issues - Y. Alexahin, FNAL December 5, 2006

  20. Backup slides – straight FOFO channel (Y.Alexahin)  tilted solenoids straight solenoids RF cavities y/L z/L x/L Closed orbit at  = 0.01 (dispersion follows the same pattern) • Phase advance over the 4-solenoid period is above 2 → resonant dispersion generation • Cooling by combination of GH2 and Li wedges in high-dispersion locations for damping repartition • The scheme requires RF cavities operation in high magnetic field (hopefully GH2 will help) Muon Collider & Ionization Cooling Issues - Y. Alexahin, FNAL December 5, 2006

  21. Backup slides – collider ring optics • Two optics designs so far: • prepared for 1999 PRSTAB Muon Collider Collaboration report by Carol Johnstone et al.: * = 3mm, peak max=1.5 105m, c= - 9.210-5. Requires further work on chromatic correction, the momentum acceptance is just (- 1.210-4, 1.610-4). • more conventional design by A.Bogacz: * = 1cm, peak max=4.8 103m (but with the distance from IP to the first quad just ~2m), c= 210-4 IR and a few arc cells in the design by A.Bogacz Muon Collider & Ionization Cooling Issues - Y. Alexahin, FNAL December 5, 2006

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