S117 Meeting - 21.3.1995 - 10:00

• Attendance:

  R. Bassini (until 11:00), M. Begemann-Blaich (since 10:15), S. Fritz, C. Groß, X. Hongfei, U. Kleinevoß, U. Lynen (since 10:45), Walter F.J. Müller (since 10:30), B. Ocker, T. Odeh, M.Schnittker, C. Schwarz, V. Serfling, W. Trautmann.

• Topics:

  1. Catania Hodoscope - Milano electronics:

  a. Preamps:

  There are two possibilities: The broken preamps can be either repaired or both preamp boxes are replaced by boxes with new preamps which are more stable. Concerning the time which is left until the begin of the experiment the first possibility is favourized.

  b. Stretcher problems:

  Some channels on the strecher board used during the experiment failed because of a broken diode. This will be repaired until the end of this week. Additional stretcher boards for SiStrips and the telescopes are allready finished an can be tested.

  c. ECL board:

  During the testrun there was a problem with the logic output:the rising part of the discriminated signal had some jitter because of threshold effects. This can be stabilized and the with of the discriminated output will be set to 9 mus (was 4.5 before). The longer logic output also supresses the double peak, which was sometimes observed during the testrun.

  2. Silicon Strips:

  Some new facts about the strange signals (see 7.3.1995 ). A crosstalk test on the SiStrip with an alpha source: For a small percentage (roughly 2%) of the particles crosstalk from strip to strip in the order of 50% of could be observed.

  Another problem was a 3% crosstalk signal on the shaper channels which was independent of which channels were used. There might be some problem with the grounding of the shaper.

  3. ZDO:

  An 1mm aluminum absorber is made for the ZDO. U. Lynen points out that this is too thin and should be calculated again. One should look at the proton thresholds for variable absorber thickness.

  The new PM bases are mounted and the possible overlap in angle between the ZDO mounting and the hodosopes is removed.

  4. GSI hodoscope:

  A cooling for the silicons is planned and will be built this week.

  5. TOF - Jopl:

  A third scintillator of the central 8packs is cut in the middle. The central hole will then be 6.25 cm instead of 3.75. The tubes, which did not work during the testrun will be repaired this week.

  The Jopl preamps are modified. They have now a high gain (100) and a low gain (10) output and both will be used in the experiment.

  Because there will be another Stelzer detector behind the TOF chamber, the amount of material in the beam should be as small as possible.

  6. MSU hodoscope:

  GJK will be at GSI between 29.3-25.4. and 10.5.-24.5.

  Sally Gaff will be at GSI between 3.4-24.5.

  7. DAQ:

  Three FASTBUS modules will be send to LeCroy, Heidelberg for repairing. The "broken" FASTBUS TDCs are actually not broken but have to be programmed in a slightly different way.

  Simplifiying the DAQ startup procedure is still under construction. It is no longer possible to overwrite the pedestal file by accident (at least we hope so ;-)).

  8. Start - Halo:

  For the light coupling and as a supporting frame for the HALO a 5mm instead of a 2mm plexiglas has to be used.

  For the Start detector a new foil ladder with less material will be used. The so called Folger target frames are used which are shaped in a fashion that a particle which produces light in the scintillating foil will not hit the ladder. Besides the size in y-direction will be larger.

  9. Miscallenous:

  It is important to know wether the HALO scrapers in the beamline will be mounted and routinely operated until the begin of our beamtime.

• Next meeting: 28.3.1995 - 10:00