Minutes of the telephone conference about Post Collision Issues 
February 7, 2005, compiled by V. Ziemann, UU

Participants:
P. Bambade, O. Dadoun, Cecile Rimbault,  LAL-Orsay
R. Appleby, J. Carter, Daresbury and RHU
A. Faus-Golfe, IFIC-Valencia
D. Schulte, CERN
A. Ferrari, T. Ekelof, V. Ziemann, Uppsala

After a brief introduction of the participants P. Bambade gave
a brief run-down of the current activities done in collaboration
R. Appleby and O. Dadoun which mostly focus on the 2 mrad option
of the ILC final focus. The following issues were mentioned

  * QD is passed off-axis (kick is 3-4 mrad) and the resulting
    dispersion is compensated with a bend down stream. Quads
    inbetween fix the phase-advance and an additional sextupole
    alleviates the chromatic calamities with the low energy tail.
    The optics calculations are done with  MAD and tracking with
    DIMAD. Olivier does a comparison of BDSIM and DIMAD tracking.
    The first quad in the extraction line probably has to be
    septum quad.
  * Special attention is dedicated to losses and background in
    the beam line. In particular synchrotron radiation from QD
    is a problem.
  * Similar efforts are going on at SLAC and are compared to 
    the LAL/UK activities. Focus lies on 500 GeV system at SLAC
    and 1 TeV at LAL/UK. 
  * A horizontal chicane is preferential to a vertical one because
    of polarization.
  * Philip pointed out that the dump for beamstrahlung and
    primary beam are different due to the chicane.

Daniel pointed out the necessity to carefully benchmark the used
computer codes and a lively discussion followed. 

  * Volker volunteered to take care of a web-site to host the input 
    files and discussion of results of the code comparison. 
  * Robert and Philip provide an example lattice of the post-collision 
    line based on the present 2 mrad dump line and having all the 
    trouble-making elements like off-axis quads and sextupoles included. 
    A set of  typical bench-marking plots to be reproduced will be 
    proposed as a starting point for the comparisons. Probably, such 
    comparisons will also involve colleagues participating in the work 
    at SLAC and KEK.
  * We can probably use the GuineaPig input files from the mdi
    website at LAL for starting conditions.
  * Codes: MAD, DIMAD, PLACET, BETA, TRANSPORT, BDSIM, SAD, 
    private codes.

Angeles will have a new student and they will work on understanding
the optics-codes and their comparison. Then she will collaborate with 
LAL/UK on the 2 mrad final focus.    	

In the near future Daniel plans to work on the code comparison.
Furthermore he suggested to look at tolerances and imperfections.

Volker plans to first get BDSIM working and then using it to
understand the present 20 mrad final focus and extraction line and
extrapolating it to higher energies to understand where the limits
are. Arnaud will contact people at SLAC regarding work done on
the 20 mrad final focus.

We also mentioned the necessity to find suitable limits for the
tolerable losses. For now Philip suggested to use 100 W/m as a
base. The required aperture to transport the beam to the dump 
with a given lossrate per meter is a useful measure and should 
be calculated. For beamstrahlung the opening angle is the 
relevant quantity.

We briefly discussed the communication infrastructure and agreed
that Daniel will use the CERN phone system to host the next
phone meeting which is planned to be on the monday before the 
next ILPS meeting.