S117 Meeting - 7.3.1995 - 10:00

• Attendance:

  S. Fritz, C. Groß, X. Hongfei, J. Lüning, Walter F.J. Müller, B. Ocker (since 11:15), T. Odeh, C. Schwarz, V. Serfling, W. Trautmann.

• Topics:

  1. Scattering chamber :

  The chamber was rotated. Because the rails have an angle of 0.4%, they have to be aligned so that (hopefully) the chamber will be aligned when rotated back for the 100 MeV run.

  2. Start detector:

  There will be a new HALO detector. It consists of a 200 mu scintillating foil (BC418) which will be read out by PMs via plexiglas light guides.The hole in the foil should not be larger than the target (20 mm diameter).

  3. ZDO:

  All bases of the ZDO are redesigned. For the middle and the outer layer the nonlinear bases with the low resistance (1.5 MOhm) got the same resistors as the inner layer (1.8, 1.2, 1.2, 1.2, 1.2, 1.2, 1.2 MOhm = 9 MOhm), which will increase the amplification by 50%. A factor of 2 was gained by replacing the 50 Ohm resistance parallel to the output with 1 kOhm. A factor of 2 can be gained during the experiment by applying 1500 instead of 1200 V, because the produced heat of the new bases will be much smaller. This yield in an overall factor 6 for the middle and outer an a factor 4 for the inner layer.

  4. Si Strips :

  Multiplicity spectrum: Exponential fall of between Multiplicity 5 and 20 and a small peak at Multiplicity 25 (maximum multiplicity). The energy spectra showed a two-fold structure. The bump at lower energy had a higher multiplicity content as the tail of the distribution. This might be due to the strange bipolar signals which were seen during the testbeamtime when putting one detector signal on the oscilloscope.

  The setup has to be changed in order to perform a alpha source test in the chamber. The Si strips have to be turned around and for the alpha test the brass shieldings have to be removed. Maybe for the 100 MeV a thinner shielding should be used.

  5. Data acquisition :

  The E7 processor has to be repaired. At the moment measurements for calibration and testing are possible with a E6. The whole DAQ will be simplified so that it can be used and controlled by more people.

  7. TOF :

  During the testrun the maximum count rate limit on TOF and Jopl is 0.5 MHz. Another problem of the beam time was the apparently bad focus on the wall which brought a very high count rate on the central slats, especially the left and the right neighbour of the hole. There should be a modifaction of the central 8pack. The bias voltage will be made individually adjustable for the slats in this 8pack. Furthermore the hole will be increased by one slat on every side.

  8. Miscalleneous :

  X.H. wants to have the bias for the Telescopes in the counting hut. This requires one additional NIM crate and one 13m Cannon cable with 16 connectors for the back arm. Alternatively one can use the SHV at the front arm.

• Next meeting: 21.3.1995 - 10:00