Download RF Safety Discussion

RF Safety Discussion
Derun Li/Bob Rimmer
Center for Beam Physics
Lawrence Berkeley National Laboratory
SRF Institute, JLab
Hazards & Mitigations
• High Voltage
– Usually fully contained in interlocked enclosure
• RF radiation
– Survey, configuration control, WG overpressure
• X-rays
– Shielding, monitors, interlocked access (PPS)
• Vacuum implosion (e.g. ceramic windows, foils)
– Mechanical barriers, redundancy, procedures
• Arc
– Fast arc detection, reflected power, vacuum
MICE Cavity Conditioning
• Before turning on high power RF
– Cable calibrations (safety related)
• Power measurements (for safety interlock): forward and
reflected power
– Low power RF measurements: frequency, coupling
and Q (may be used to calculate critical quantities)
– Interlock checkout
• Arc detectors have to be verified (using test light and see if it
triggers the interlock)
• Vacuum interlock: break vacuum measurement circuits
• RF window temperature interlock (water flow, infrared etc.)
• Water cooling system interlock (flow switch or “klixon”)
– Visual inspection and survey for RF leaks if
necessary (start at low power, maybe into a short
circuit)
RF safety cont.
• Other inputs into RF “permissive”
– Pressurized waveguide interlock
– Radiation monitor interlock
– PSS chain
– LLRF “heartbeat”
– Hydrogen safety system?
– Etc.
• Magnetic field interlock
• PSS system should have it’s own
checkout procedure
• Area search or sweep
MICE cavity conditioning
• General process
– Go slowly
– Condition couplers if needed (de-tune cavity)
– Ramp voltage/pulse length with magnets off
– Control ramp rate with vacuum up to gradient
– Increment magnetic field & repeat
• Don’t get impatient (computers are better at this)
– May sit in multipacting bands for a while
– May take a while to condition at high gradient
– Do not raise vacuum trip point to “help things
along a bit”
Post-conditioning
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Relax & Enjoy
Monitor trip rate pay attention to changes
Cool some muons
Write papers
Build neutrino factory
Condition a lot more RF systems
Measure Higgs
Retire somewhere warm and sunny