Accelerators and Sources Report from Discussion Session Jose Alonso 1

Charge (Per Janet) Credible case needs to be made to DUSEL in very near future –Address relevant technical (not cost, now) issues What questions need to be answered related to feasibility of accelerator concept? Can one develop (now) specifications for target/beam stop? –What issues are there relating to target/stop that need R&D or careful engineering studies?

Accelerator Questions Is ion source an issue? EXTERNAL –NON-ISSUE –Emittance –Brightness (intensity) –Duty factor –Reliability Is axial injection best way to go? –Injection energy ~ 1-2 MeV (space charge) Inflection may be problem Lose factor of 10, heat dissipation Longitudinal phase space acceptance depends on extraction strategies –Questions about channel design in 7T magnet?

Accelerators (2) Is central region feasible? –Injection orbits –Space charge –Vertical focusing –Turn geometry (clearances?) –Emittance growth (factor of 5?) –Injection, dipole? Can’t do. Electrostatic… may require lower injection energy (300 keV?)

Non axial injection? Internal sources? –If don’t worry about beam quality… –7T field, GHz ECR frequency? Not crazy Can one get ECR conditions in central region? –Confinement time? –Plasma density? Radial injection, looping orbits in

Central Region Issues Do you worry about emittance? –Extraction strategies critical!! “Soup” – huge energy spread (100 MeV to 1 GeV??)

Accelerators (3) Magnet questions? –Max field? Non-issue Reduce field may ease some beam problems –Isochronicity requirement Vertical focusing problem May limit to 5 T average field –Return yoke, 700T… may be a lot less? –Field variations and control – flutter? How form flutter? Current sheets? (B too high for steel) Exotic materials? –Holmium neutron cross section x30 thermal neutrons over steel, but difference is much less at higher neutron energies

Accelerators (3A) RF questions? ~200 MHz, frequency not issue ~$2/watt –Stay in broadcast band –Requirements for 1 MW beam power? (~3MW, ~$6M) –Pulsed vs CW? –Voltage requirements to meet requirements? If creating “soup” don’t care If need high-quality beam, have REAL problem –Beam loading and on/off transitions?

Accelerators (4) Extraction? –Self-extraction, IBA, 14 MeV H+, mA beam (this energy seems to be limit) 75% efficiency, Need scaling parameter, energy gain in field-changing region, turn separation is much lower at higher energies, Rf manipulation could induce resonances? Relating to beam energy? Need tune close to gamma (~2 for 1 GeV) Can one get 1 cm/turn? Liouville Theorem limits Are there “un-needed” dimensions in phase space? –Turn separation? –Septum placement, definition of extraction channel? –Beam loss specification for component survival and maintainability? –(Is controlled extraction possible?)

Accelerators (5) Radiation problems? –Magnet quenching? –Activation? Pretty well understood (FNAL) Tokamak example… much more severe problems Thermal cycling to restore conditions Displacements per atom? (3kbarn for DPA) Trapped hydrogen? Helium? –Neutron fluxes due to beam loss? –Material degradation? –Maintainability questions? (SNS – 1w/meter) Hands-on limits and requirements?

Accelerators (6) More general questions? –Transport line to dump? (If extracted) Backstreaming activating accelerator –Is current concept feasible? –Are there alternatives one might consider? –H 2 + options? Catania design 1 GeV/amu, machine twice as big TUPLS078 EPAC 2006 Jongen/[Dubna group] Lorentz stripping?

Target/beamstop (1) What unanswered issues exist? For “soup” or extracted beam? –Pursue both paths. –Need conceptual designs for both “Donut” issues… –Materials? All pretty well understood –Dimensions? –Instrumentation? Calibration Inter-facility comparisons

“Donut” issues Window Vacuum chamber issue –Common chamber –Rf issue –Cryogenic issues for coils for flutter Distributed beam dump + distributes heat load - Increases area, volume

Target/beamstop (2) Maintenance and lifetime issues? –Degradation over time? How would donut target be changed? –Changes from instantaneous energy- absorption “Red herring”

Target/beamstop (3) Issues relating to interfacing with building –Hot cells and handling of hot material May or may not be an issue –Shielding need MARS Donut problems! (MiniBOONE hall?) –Ground water need MARS Design of mitigation/isolation Prevent contamination –Sky shine? Physics question? Defines vertical shielding –Tritium … groundwater Need “nuclear ventilation” for vacuum discharge, circulating air, stack discharges –Be-7 … closed cooling system

Summary Points 3 options –Soup –H 2 + –Current concept