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Alignment and tolerances - task description

The task is to determine what the tolerances are for the MICE Demonstration of Ionisation Cooling lattice. Intention is to deliver tolerances to the engineering team and let them feedback where they are not practical; we can then assess the consequences.

Reminder of experimental aims

The aims of the MICE analysis are to

  • Measure the emittance change in the MICE cooling channel
  • Show that MICE does indeed cool the beam
  • Show that the simulation tools correctly reproduce the MICE cooling channel performance

In order to do this, we need to understand the properties of the cooling channel. In particular, we need to be able to:

  • Predict the emittance change in the cooling channel
  • Have a cooling channel which cools okay
  • Understand particle trajectories in the cooling channel
  • Understand the channel optics (i.e. the behaviour of the beam as a whole)
  • Reconstruct the detectors

Tolerance Criteria

The tolerance - i.e. allowable error - on each parameter should be determined for each of the following criteria. Some criteria will be more relevant than others (e.g. magnetic fields can never cause energy loss)

  • At what point does the output emittance of the cooling channel degrade by more than 1 (0.1) %?
  • At what point does the optical beta function at the absorber change by more than 1 (0.1) %?
  • At what point does the optical beta function at the downstream tracker change by more than 1 (0.1) %?
  • At what point does the mean position of particles in a matched, 6 mm emittance beam, change by more than the downstream tracker resolution (10 % of the D/S tracker resolution)?
  • At what point does the field uniformity in the tracker region degrade by more than 1 (0.1) %
  • At what point does the projection from tracker to PID detectors become dominated by the field errors (as opposed to multiple scattering, energy straggling, finite size of detectors)?
  • At what point does the energy loss/gain change by more than 1 % (0.1 %)?
  • At what point does the energy loss/gain change by more than 10 % (1 %) of the detector resolution?
  • At what point does the scattering in material change by more than 1 % (0.1 %)?

Note that I have put a loose tolerance and a tight tolerance on each specification. The loose tolerance means that analysis group would have to measure the effect and treat it in the analysis; the tight tolerance means that the analysis group would be able to treat the error as a systematic.

Parameters of interest

Magnets

We desire to know the tolerances of the following parameters:

  • Module position
  • Module rotation
  • Magnet field strength (power supply current)

The modules are the two spectrometer solenoid modules and two focus coil modules.

Absorbers and windows

We desire to know the tolerances of the following parameters, for material in the beamline (windows and absorbers)

  • Material position
  • Material rotation
  • Material thickness

RF

For the RF cavities:

  • RF cavity position
  • RF cavity rotation
  • RF phase
  • RF peak voltage

Implementation and Reporting

  • Results of the study should be reported reasonably frequently at analysis meetings or equivalent.
  • The study should eventually be written up as one or more MICE notes
  • Simulations should be reproducible; i.e.
    • use a release version of MAUS
    • a publicly available geometry (ideally on the Configuration Database)