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Summary of "8V" Activation Study discussions

This is an informal summary of separate discussions Henry Nebrensky had with Dean Adams, Chris Rogers and Ed Overton, around the 18 July 2013.

HN: I would like to follow up the 4V Activation Study (Feb. 2013) with an 8V Activation Study in either Sept. 2013 or Feb. 2014:
  • Get it done and dusted. Also same target as last study - comparable hardware.
  • Even if MICE DAQ saturates at 4V, may need higher losses to keep rate if e.g. DS fails
  • Establishes operating envelope - 8V is maximum practically possible with a 0-10V display
DA: Why is MICE now asking for 4V, when a few years ago talk was of 20V?
  • The tracker effectively saturates because of the dead time. This wasn't expected to be a problem but "misplaced optimism" regarding tracker firmware re-write.
DA: Beyond 4V, BLMs elsewhere in ring start to saturate. (May not be obvious as the calibration for voltage vs. loss isn't constant around circumference.) Could MICE stay at 4V and dip twice as fast?
  • The principle of dipping faster and shallower suits MICE (see above).
  • HN: would rather not dip faster already in September, as we then have a new project to double the DAQ rate for projected EMR run.

DA: MICE could run at 8V in Sept. if needed.

HN: If beyond 4V is an issue, then how would 20V be achievable?
DA: Could run at 20V - can lower gain on BLMs to keep MICE in range.

NB thus MICE must be careful about quoting beamloss as BLM voltage as that calibration can change beneath us! Hence normalise to Luminosity Monitor.

DA: Is 4V 3ms spill gate max. for MICE?
  • Step IV: 3ms gate
  • Steps V/VI: 1ms (this needs to be tested at the end of IV - must go on work plan!)

[Subsequent note: the ISIS RF tank failure means MP time cut in next set of User Runs - not now confident about 8V Activation Study in Feb. 2014]

[Much later note: Discussion with Yordan 18-Oct-2013, feasible to have DAQ capture at 64/50 instead of 128/50 but might have to split equipment across multiple crates to read out in time. But, why would we want this? YK claims that present trigger rate (with DS) is sufficient to demonstrate ionisation cooling within a couple of days. Whence the discrepancy between the extended StepIV/VI schedules (e.g. a year for Step IV, see Coney CM36 Ops slides 10 & 11), and the long-standing claim ("we only need a million muons" - from a CM 5+ years ago) that once the experiment is built we can complete data-taking within a week?]