Operational experience with high power proton beams David Findlay Head, Accelerator Division ISIS Department Rutherford Appleton Laboratory / STFC ADSR workshop, Cambridge, 13 January 2009

2 High power proton accelerators used and proposed for: Spallation neutron sources (molecular studies) Neutrino factories (life, universe & everything) Tritium production Transmutation (nuclear waste) Electricity generation  review of high power proton accelerator operations ADSRs

3 Current high power proton accelerators: PSI (Villigen, Switzerland) LANSCE (Los Alamos) SNS (Oak Ridge) ISIS (RAL, Oxon.) J-PARC (Tokai-mura) Concentrating on user-facility accelerators Decreasing power

Guinness Book of Records — can no longer show this photo

5 ISIS — world’s most productive spallation neutron facility ISIS J-PARC, PSI, SNS ISIS:800 MeV protons on to tungsten targets, 0.2 MW TS-1, 0.16 MW, 40 pps; TS-2, 0.04 MW, 10 pps ~800 neutron experiments per year ~1600 visitors/year (~5000 visits) ISIS accelerators wholly for neutron factories Also muon factory Decreasing number of target stations

Rutherford Appleton Laboratory, looking north ISISDiamond

Rutherford Appleton Laboratory, looking north-east ISIS

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

ISIS from air

View down north side of ISIS 70 MeV H – MeV linac

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

ISIS TS-1 experimental hall

ISIS TS-2 experimental hall

14 Key dates: Dec. 1984, first beam to TS-1 Dec. 2007, first protons to TS-2 Aug. 2008, first neutrons from TS-2

15 How reliable is ISIS? Cf.big chemical plant (good performance)~80% oil refinery (good performance)~70%

16 How reliable is ISIS? Cf.big chemical plant (good performance)~80% oil refinery (good performance)~70% ISIS 10-year average availability: 88% (±6% stand. dev.)

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19 How reliable is ISIS? Cf.big chemical plant (good performance)~80% oil refinery (good performance)~70% ISIS 10-year average: 88% (±6% stand. dev.) Cf. ILL reactor (Grenoble):

20 ISIS cf. other high power proton accelerators Lujan = neutron scattering centre at LANSCE (800 MeV protons, PSR) NuMI = Fermilab main injector (neutrino production) (120 GeV protons)

21 ISIS70 MeV H – linac0.2 MW MeV H + synchrotron J-PARC180 MeV H – linac0.2 MW GeV + 50 GeV synchrotrons LANSCE800 MeV H + /H – linac0.8 MW + accumulator ring (0.1 MW) PSI590 MeV cyclotron1.2 MW + 72 MeV injector cyclotron SNS1 GeV H – linac0.6 MW 2 + accumulator ring 1: For limited time during commissioning; ultimate design 1 MW with 400 MeV linac. 2: Still commissioning; 1 MW design operation.

22 Trips — require operator intervention to reset Inhibits — automatically reset after ~1 second No. of inhibits = several × no. of trips Inhibits:non-specific beam losses running near some edge

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27 Trip and inhibit summaries: Trips longerAverage no. ofStandard thantrips per daydeviation 1 second hour hours hours Inhibits per day— automatically reset AverageSt. dev ~100 “beam offs” per day

Factors determining success of user facility

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30 2/3 power law

31 Availabilities — good or bad — as they are because machine runs for only ~2/3 year per year Maintenance/shutdown ~1 week machine physics + run-up ~40-day cycle ~3-day machine physics 220 days running maximum — any more would have substantial resource implications In principle “just in time” preventative maintenance régime, but effectively partly/mostly responsive régime — too expensive otherwise ~5/year

32 Crew: 5 teams of 4 — 24 hours/day, 365 days/year — even during shutdowns (although shift size may reduce) Each team:Duty Officer Assistant Duty Officer Shift Technician Operations Assistant Team of 5 health physicists — one of whom on call Accelerator and target: ~30 people on call at any one time 24 hours/day, 7 days/week — 45 names Instruments, sample & environment: ~15 on call (TS-1) With TS-2, ~100 people total mostly “electrical”

33 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 ISIS only ~0.2 MW, but ×2 beam losses would make life very difficult (2–3 mSv annual dose limit) Protection from activated machine components Time, distance, shielding — elementary, but important Explicitly included in designs

34 12 “major” categories Always some arbitrariness

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37 How improve ISIS accelerator availabilities? Subtract target down-time 88%  90% Money-no-object staffing 90%  95% ? Under-run equipment 4616 tetrodes (linac RF): mean life ~10–20k hours 4648 tetrodes (synch. RF, markedly under-run): mean life 68k hours (June 2004 data)

38 How improve ISIS accelerator availabilities? — 2 “Better” engineering What is “better”? Avoid “value engineering” PLC control systems not always better than old relay systems Sometimes simplicity best Minimise numbers of electrical connections Lots of off-line test/proving rigs, e.g. Run all tubes for 1000 hours before installation

39 How improve ISIS accelerator availabilities? — 3 Lots of warnings, e.g. Reflected RF powers increasing Water pump bearings becoming noisy Big transformers becoming hot But need staff on hand to act on warnings UPSs for sensitive plant Mains-dip crash-offs can give serious problems But resources needed to service UPSs Interlocks to trip off plant “gently” — not just make main contactor fall out Good water chemistry control

40 How improve ISIS accelerator availabilities? — 4 ~1-second trips — due to beam losses Often cause simply unknown Sometimes RF instabilities (but sometimes magnet PSUs) Mitigation from feedback systems already incorporated Sometimes bad electrical connections — high currents often involved Hitherto no real need to mitigate Tackle by redundancy? — provided common mode issues don’t dominate

41 Essential conclusions? Good engineering Lots of people Parallel accelerators (>2) Expensive!

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43 Some relevant issues Plan in detail — break down into many sub-tasks — estimate radiation doses for each sub-task UK legal limit: 20 mSv/year RAL investigation level: 6 mSv/year ISIS practice: 3 mSv/year Design all new apparatus with active handling specifically in mind — e.g. Lifting lugs V-band not Conflat seals Ensure plenty of space around Detailed project management of task

V-band seals Conflat seals Lifting lugs Lifting lug

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

ISIS synchrotron room — originally built for Nimrod Ample space essential for repairs, exchange of large components, etc. Nimrod sector

Overhead cranes very important — especially for handling activated components Aim to have two in each area

Shielding Configurable shielding to reduce dose rates locally