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 ID: 1048161
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1. Accelerators and SourcesReport from Discussion SessionJose Alonso1
2. Charge (Per Janet)Credible case needs to be made to DUSEL in very near futureAddress relevant technical (not cost, now) issuesWhat 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?
3. Accelerator QuestionsIs ion source an issue? EXTERNALNON-ISSUEEmittanceBrightness (intensity)Duty factorReliabilityIs axial injection best way to go?Injection energy ~ 1-2 MeV (space charge)Inflection may be problemLose factor of 10, heat dissipationLongitudinal phase space acceptance depends on extraction strategiesQuestions about channel design in 7T magnet?
4. Accelerators (2)Is central region feasible?Injection orbitsSpace chargeVertical focusingTurn geometry (clearances?)Emittance growth (factor of 5?)Injection, dipole? Can’t do. Electrostatic… may require lower injection energy (300 keV?)
5. Non axial injection?Internal sources?If don’t worry about beam quality…7T field, GHz ECR frequency? Not crazyCan one get ECR conditions in central region?Confinement time?Plasma density?Radial injection, looping orbits in
6. Central Region IssuesDo you worry about emittance? Extraction strategies critical!!“Soup” – huge energy spread (100 MeV to 1 GeV??)
7. Accelerators (3)Magnet questions?Max field? Non-issueReduce field may ease some beam problemsIsochronicity requirement Vertical focusing problemMay limit to 5 T average fieldReturn 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
8. Accelerators (3A)RF questions? ~200 MHz, frequency not issue ~$2/wattStay in broadcast bandRequirements for 1 MW beam power? (~3MW, ~$6M)Pulsed vs CW?Voltage requirements to meet requirements? If creating “soup” don’t careIf need high-quality beam, have REAL problemBeam loading and on/off transitions?
9. 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 limitsAre 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?)
10. Accelerators (5)Radiation problems?Magnet quenching?Activation? Pretty well understood (FNAL)Tokamak example… much more severe problemsThermal cycling to restore conditionsDisplacements 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?
11. Accelerators (6)More general questions?Transport line to dump? (If extracted)Backstreaming activating acceleratorIs current concept feasible?Are there alternatives one might consider?H2+ options? Catania design1 GeV/amu, machine twice as bigTUPLS078 EPAC 2006 Jongen/[Dubna group]Lorentz stripping?
12. 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 understoodDimensions?Instrumentation?CalibrationInter-facility comparisons
13. “Donut” issuesWindowVacuum chamber issueCommon chamberRf issueCryogenic issues for coils for flutterDistributed beam dump+ distributes heat load- Increases area, volume
14. Target/beamstop (2)Maintenance and lifetime issues?Degradation over time?How would donut target be changed?Changes from instantaneous energy-absorption“Red herring”
15. Target/beamstop (3)Issues relating to interfacing with buildingHot cells and handling of hot materialMay or may not be an issueShielding need MARSDonut problems! (MiniBOONE hall?)Ground water need MARSDesign of mitigation/isolationPrevent contaminationSky shine? Physics question?Defines vertical shieldingTritium … groundwaterNeed “nuclear ventilation” for vacuum discharge, circulating air, stack dischargesBe-7 … closed cooling system
16. Summary Points3 optionsSoupH2+Current concept