Minutes for 16 Mar 2006 SWMD Telephone Meeting

Present: Andre Sopczak, Jonny Smith, Luis Fernandez, Justin Greenhalgh, George Ellwood, Adriana Bungau, Nigel Watson
Minutes: Nigel

Material damage
- EUROTeV documents
- Draft EUROTeV report on Geant4 damage simulations - Adriana
  Prepared a report on her Geant4 studies, following closely the format which Luis used for his Fluka work, allowing easy comparison of results. Requested comments to her before 28-Mar-2006 so that she can finalise this before next group meeting.
- SLAC Damage Tests - George
  Presented a study of stress predictions for bunch impacts on Ti alloy, spaced at 0.1s, as at ESA, with energy deposition from Luis' Fluka simulations. Refinement since last work is to restrict model to a smaller total volume (but same spatial mesh size) to keep computation to sensible time while examining behaviour over longer timescale. Verified this does not affect max. temperature rise or location of this. Peak temp. rise observed ~230K reduces to rise of ~35K after 0.02s; some unphysical fluctuations of temperature observed on underlying temperature rise which decays with time. Conclusion: 0.1s beam spacing will not be suitable to study ILC damage from multiple beam impacts, even if a spot size o(10microns) could be achieved.
  Next: (i) Repeat study over total time 0.02s, to be absolutely sure about the apparent temperature oscillations observed on this timescale.
  (ii) Simulation of stress inside sample as possible at DESY: circular disk, 20mm diameter, 4mm thick, Ti alloy, with energy deposition profile from Luis using Fluka.
- Exploration of Issues in Thermal Shock - Justin
  A few (highly selected) key points, from a lot of work: time profile of heating from a single bunch cannot be important - there must be a thermalisation time ~10^-10s which is much greater than time over which energy is deposited in the material. Similarly, detailed profile in space over which energy is deposited is not expected to be too important (although should be used as available). Reflected stress waves are observed (+ sign changes in the stresses), therefore combination of both tensile and compressive stresses will be present. 3-d effects will be important and have to be considered.
  Failure mechanisms in the material: von Mises stress (still an appropriate concept?) and melting.
- Short proposal status - waiting for NKW.
- Discussion of damage tests: Luis to send George profile of energy depostion from FLuka for samples of the size which can be accommodated by the DESY jig, assume round beam with sigma_r=10microns. Q: How to determine damage on surface? Assume SEM, with location of spots using fiducials on surface.
Wakefield simulations: Comparisons of Theory, GdfidL & ABCI - Jonny
Analytic calculations - spreadsheet- Mark S. / Nigel (original version)
Wire/bench test preparations

Progress for ESA tests

Collimator jaws 5-8 - Photos
Reconstruction code

ESA test beam travel
Please confirm dates, below is best information I have at present (change from previous meeting, Andre will now also attend):

     Luis - 9/4 - 11/5
     Carl - 11/4 - 25/4
     Frank - 24/4 - 8/5
     Jonny - 24/4 - 11/5
     Roger J. -
     Andre - 20/4 - 1/5
     NKW - 25/4 (pm) - 7/5 (pm)

  Remember that if you have booked e.g. flights in advance on a
  personal credit card, you can submit a separate claim for these
  before you travel, and to ensure that you do as much as you can of
  the visitor registration/safety training in advance.

Future plans