Two other aspects of the recoil detectors

From: Aaron Joseph Maschinot (ajmasch@MIT.EDU)
Date: Tue Dec 18 2001 - 11:57:40 EST


Two other things regarding the Si material/medium definition:

1) Considering as how the Si recoil detectors are so thin (about 300
    microns), it would probably be of merit to change the maximum step
    size variable, STEMAX, in the Si medium definition to something much
    smaller than the default BLAST step size of 10cm. In my recoil
    analysis that I am doing, I use a step size of 100 microns, for
    example.

2) However, even if 1) is done, GEANT will still almost always pass
    right through the recoil detectors, oblivious to their existance,
    due to the large step size in the volumes right before the recoil
    detectors (the default GEANT step size currently in CVS is 10cm!!).
    One way around this is to (as Tim suggested at the last software
    meeting) make a large volume enclosing each recoil detector volume
    such that the entrance planes of both this enclosing volume and the
    recoil detector volume overlap. As such, whenever a particle enters
    the enclosing volume, GEANT shifts the particle back to the entrance
    plane of the volume. At this point, as long as the recoil volume is
    declared as an 'ONLY' volume, it will supercede the enclosing volume
    (assuming the enclosing volume is defined as a 'MANY' volume) and
    GEANT will always "see" the recoil detectors, provided the enclosing
    volume is at least 10cm thick. I use such enclosing volumes in my
    analysis. I do not think they are a part of the file rc_geom.f,
    though. I think they should be.

Both of these changes, in my opinion, should be added to CVS, else the
recoil detectors will not be seen correctly by GEANT.

Thanks,

Aaron



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