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Beam losses on ISIS and induced radioactivity David Findlay Head, Accelerator Division

Beam losses on ISIS and induced radioactivity David Findlay Head, Accelerator Division ISIS Department Rutherford Appleton Laboratory / STFC MICE target review, 18 December 2009. 70 MeV H – linac. 800 MeV proton synchrotron. TS-1.

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Beam losses on ISIS and induced radioactivity David Findlay Head, Accelerator Division

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  1. Beam losses on ISIS and induced radioactivity David Findlay Head, Accelerator Division ISIS Department Rutherford Appleton Laboratory / STFC MICE target review, 18 December 2009

  2. 70 MeV H– linac 800 MeV proton synchrotron TS-1

  3. Synchrotron: 800 MeV proton, 50 Hz 5 µC each acceleration cycle Targets: W (Ta coated) Protons: 2 × ~100 ns pulses, ~300 ns apart Moderators: TS-1: 2 × H2O, 1 × liq. CH4, 1 × liq. H2 TS-2: 1 × liq. H2 / solid CH4, 1 × solid CH4 Instruments: TS-1: 20 TS-2: 7 ~330 permanent staff, ~£35M/year budget ~750 experiments, ~1500 users, ~5000 user-visits per year World-leading

  4. Operating ISIS • Beam losses • Concentrated at one place — on collectors • Imperative to keep beam losses low (~1 W/m) • ISIS: ~1 kW lost, 163 m circumference, ~6 W/m — activity would be worse at higher energies • ISIS only ~0.2 MW, but ×2 beam losses would make life very difficult (3 mSv annual dose limit) • UK legal limit: 20 mSv/year • RAL formal investigation level: 6 mSv/year • ISIS limit: 3 mSv/year

  5. Collector straight MICE target

  6. Superperiods 9, 0 and 1 of the ISIS 800 MeV synchrotron

  7. Long mechanical drives to reduce need to work close to high-radiation locations (e.g. when changing motor drives for beam collectors)

  8. Vertical and horizontal collectors in Straight 1,looking downstream and upstream

  9. BLMs in grey trunking

  10. Straight 1 — too active for routine measurement Typical dose rates round synchrotron — data from 2005 and 2006

  11. ~0 V 1.6 V R8BLM1 (V-ms) 2.8 V 5 V

  12. R8BLM1 Sum BLMs 0 V-ms 1.6 V-ms 1.6 V-ms 20.3 V-ms 2.8 V-ms 30.6 V-ms 5.0 V-ms 57.0 V-ms [Old HEP oscillating target strip-out: highest recorded dose rate 100 mSv/h(10 rem/h)] • Without MICE, sum BLMs = 1.6 V-ms • At 1 target dip per second for R8BLM1 = 5 V-ms • Average sum BLMs = (49 × 1.6 + 57.0) ÷ 50 = 2.7 V-ms • 69% greater — not tolerable

  13. Way(s) forward? • Dean’s bump • Create vertical bump (R0VD1, R5VD1, R7VD1, R9VD1)Ramp up over 8–9 ms, maintain over 9–10 ms 6 mm achieved so far • 10 mm vertical bump at MICE target should be possible with new trim quad. PSUs (higher currents and higher slew rates) • Different target configurations and/or materials • E.g. pion production cf. multiple scattering • Beam dynamics modelling • ?

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