Presentation on theme: "Front end test stand — WP2"— Presentation transcript:
1 Front end test stand — WP2 Lead author:David FindlayAccelerator DivisionISIS DepartmentRutherford Appleton LaboratoryMichael Clarke-GaytherAlan LetchfordJohn Thomason
2 Why interest in front end? Front end of machine is wherecurrents and duty cycles are set for whole machinebeam quality is set for whole machineUKNF: 5 MW — Front end must be good!Multi-megawatt proton accelerators are newNeutrino factoriesNeutron sources, transmutation, tritium, energy, etc.1 W/m loss max., ~10—7 loss per metreStrong overlap
3 Neutrino factory proton driver: Ion source (65 mA)LEBT (low energy beam transport)RFQ (75 keV 2.5 MeV, 280 MHz)Chopper (typically ~30% chopped out)DTL (2.5 MeV 180 MeV, 280 MHz)AchromatSynchrotronsNeed a front end test stand!Front end
4 Ion source: H—, 65 mA, 400 µs2 × 2 × world’s leading H— source — ISISExisting negative ion source development programme at RAL for HPPAs in generalASTeCEU (network HPRI-CT )This programme a benefit to front end test stand programme
6 LEBT and RFQLow energy beam transportMatches 65 mA from ion source to RFQRFQ4-rod, 75 keV 2.5 MeV, 280 MHzThese less of a problemCan base on experience of LEBT and RFQ for ISISMore a matter of implementation than R&DBut ~1–1½ MW RF driver required for RFQ
7 Also to minimise RF transients and control beam intensity Why chopper?Ion sourceLinacRingBeam loss>10 × ISISBunchingAlso to minimise RF transients and control beam intensity
8 With chopper — gaps in beam Ion sourceLinacRingNo beam lossBunching
9 Chopper performance required DC acceleratorRF acceleratorns – µs spacingUKNF: 280 MHz, bunch spacing 3.57 nsSwitch between bunchesGoodOnOffBadPartially chopped bunches a problem! Tune shifts!
10 Choppers across the world: SNS 402 MHz, slow — only chopper builtCERN 352 MHz, power dissipation?RAL 280 MHz, fast, rugged, “UK”LEBTMEBTSNS, 2½ ns per bunch
11 Slow transmission line RAL aspiration: switch in 2 ns and dissipate ~3–4 kW (when “off”)2-stage processSlow transmission line1Lumped line — thermally hardened2 ns8 ns
12 RAL beam chopper — outline scheme Need to build and test with bunched beam
13 Build test standIon source (R&D alreadyunder way)LEBTRFQ (bunches beam)ChopperDiagnosticsExperience of building test stands at RAL — ISIS RFQ test stand
14 Front end test stand at RAL — costs SY £k (hardware incl. VAT +contingency)Overall design + infrastructureIon sourceLEBTRFQChopper4355 hardware185 travelstaff9035 total
16 Front end test stand at RAL Six-year programme to buildCosted on basis of test stand already built and working~£4½M equipment~80 staff-yearsRAL + university staffPhysics and engineering of real accelerator facility
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