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Operational experience with high power proton
beams David Findlay Head, Accelerator
Division ISIS Department Rutherford Appleton
Laboratory / STFC ADSR workshop, Cambridge, 13
January 2009
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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
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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
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Guinness Book of Records can no longer show
this photo
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ISIS worlds 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
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ISIS
Diamond
Rutherford Appleton Laboratory, looking north
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ISIS
Rutherford Appleton Laboratory, looking north-east
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70 MeV H linac
800 MeV proton synchrotron
TS-1
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ISIS from air
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View down north side of ISIS 70 MeV H MeV linac
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Superperiods 9, 0 and 1 of the ISIS 800 MeV
synchrotron
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ISIS TS-1 experimental hall
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ISIS TS-2 experimental hall
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Key dates Dec. 1984, first beam to TS-1 Dec.
2007, first protons to TS-2 Aug. 2008, first
neutrons from TS-2
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How reliable is ISIS? Cf. big chemical plant
(good performance) 80 oil refinery (good
performance) 70
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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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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)
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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)
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ISIS 70 MeV H linac 0.2 MW 800 MeV H
synchrotron J-PARC 180 MeV H linac 0.2 MW1
3 GeV 50 GeV synchrotrons LANSCE 800 MeV H
/H linac 0.8 MW accumulator ring (0.1
MW) PSI 590 MeV cyclotron 1.2 MW 72 MeV
injector cyclotron SNS 1 GeV H linac 0.6
MW2 accumulator ring 1 For limited time
during commissioning ultimate design 1 MW with
400 MeV linac. 2 Still commissioning 1 MW
design operation.
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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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Trip and inhibit summaries Trips longer Average
no. of Standard than trips per day deviation 1
second 28 18 1 hour 0.44 0.13 3
hours 0.20 0.08 6 hours 0.09 0.07 Inhibits
per day automatically reset Average St.
dev. 72 47 100 beam offs per day
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Factors determining success of user facility
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2/3 power law
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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
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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
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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 (23
mSv annual dose limit) Protection from activated
machine components Time, distance, shielding
elementary, but important Explicitly included in
designs
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12 major categories Always some arbitrariness
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How improve ISIS accelerator availabilities? Subtr
act target down-time 88 ? 90 Money-no-object
staffing 90 ? 95 ? Under-run equipment 4616
tetrodes (linac RF)mean life 1020k hours 4648
tetrodes (synch. RF, markedly under-run)mean
life 68k hours (June 2004 data)
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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
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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
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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
dont dominate
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Essential conclusions? Good engineering Lots of
people Parallel accelerators (gt2) Expensive!
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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
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V-band seals
Conflat seals
Lifting lugs
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Long mechanical drives to reduce need to work
close to high-radiation locations (e.g. when
changing motor drives for beam collimators)
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ISIS synchrotron room originally built for
Nimrod Ample space essential for repairs,
exchange of large components, etc.
Nimrod sector
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Overhead cranes very important especially for
handling activated components Aim to have two in
each area
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Shielding Configurable shielding to reduce dose
rates locally
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