requirements of the ess blm
DESCRIPTION
Requirements of the ESS BLM. by Lali Tchelidze CERN, Geneva, 18 Oct. 2011. The ESS. ESS: Ion source Linac Target Neutron instruments 5 MW average power 2.5 GeV protons 2.86 ms pulse 50 mA pulse current 14 Hz repetition rate - similar to SNS, but higher power and long pulse. - PowerPoint PPT PresentationTRANSCRIPT
Requirements of the ESS BLM
by Lali Tchelidze
CERN, Geneva, 18 Oct. 2011
The ESS
ESS
Max-IV
ESS:
Ion sourceLinacTargetNeutron instruments
5 MW average power2.5 GeV protons2.86 ms pulse50 mA pulse current14 Hz repetition rate
- similar to SNS, but higher power and long pulse.
The ESS
BLM requirements
• BLM should produce a beam abort signal in less than 2 μs.– Faster than SNS detector is needed (?);– We’ve redesigned the current SNS ionization chamber (shorter
gap in between the electrodes) to achieve faster ion collection time;
– Prototype quoting/ordering under process;– Will test and compare the SNS, LHC and the prototype
ionization chamber charge collection times as soon as we get all three;
Risetime of Original FNAL and New Prototype BLM
0
0.2
0.4
0.6
0.8
1
1.2
0 500 1000 1500 2000
Time [microseconds]
Cu
rre
nt
[No
rma
lize
d]
FNAL Neg Bias
New Prototype
3 kV bias, electrons to center electrode, Argon gas
Dynamic range and Sensitivity
• DR – large enough to detect slow signals, yet not saturate at high losses.
– 1 W/m (at 1 foot) -> 100 mR/h beam-off dose rate -> 100 R/h beam-on dose rates!
– 2 mR/pulse -> 0.69 R/sec during 2.86 msec pulse.
• @ SNS they never use more than 1000.
• Sensitivity - 70 nA/R/s (or even less) is probably enough.
Cryogenic requirements
• A hybrid design of a cryostat is foreseen for ESS.• an operating loss detector might be needed at 70 K / 2 K!
• Physical size of the detector should not be very small – to cover a “large” part of the loss area.