Minutes of the Zeuthen Meeting on Front End Electronics 
   -------------------------------------------------------

    Time:             Monday 29/06/98, 14:00 - 15:00
    Room:             Seminar Room 2L46
    Participants:     K.Berkhan, JJ.Wang, M.Pohl, U.Uwer, Z.Zhu


    Agenda:
    -------

   1. HV Boards:
      1.1 status of the board production
      1.2 first results from tests                                  
      1.3 order of board material
      1.4 open questions: plastic bags, length of HV cables !!!

   2. Tests of ASD-8 Distribution Board:                      
      2.1 first results from Zian 
      2.2 problems
 
   3. Test pulse distribution:                              

   4. Analog readout (Hermann's mail)




  1. HV Boards:
  --------------

  1.1 The 10mm HV boards needed for MC-2 are ready. They have
      the lengths specified in A.Lanyov's mail from Friday, 26th.

      The production of the 5mm boards has started. The boards
      for the quadrant +x+y will be equipped first and are ready
      by Thursday. The quadrants -x+y, -x-y are ready by Thursday
      next week.  

      For the quadrant +x-y there are still no numbers on the 
      required cable length available. The lengths must be
      specified by Dietrich and Sacha.

  1.2 First tests of the HV boards showed sparks depending
      on the weather condition (as expected). 
      At 35% humidity 1 channel of a 64 channel board was sparking
      at 2.3 kV.

      The board was cleaned and dried: After cleaning the channel
      was still sparking. Sparks were seen underneath the HV capacitor !!!
      -> cleaning has not improved the board behavior.
      (We should increase the statistics to check efficiency of cleaning.)
   
      Cleaning procedure:
      The board was cleaned using an ultra-sonic bath with 
      PURASOL-110(*) at 60-70 ^oC. PURASOL is supposed to remove th colophony 
      remains from the soldering.
      Afterwards water (tab water)  was used to wash the board.
      A rinsing solution (Safe-rinse 2000**) was used to remove 
      the water. Finally the boards have been dried with pressured
      air.
          
      (*) PURASOL-110: halogen-free polyglycol-ether and 
                       ether-derivate
      (**) Safe-rinse 2000, content not further specified


  1.3 Material needed for the HV board production:

      Part           Need              Status of the Order
      ------------------------------------------------------------

      PCBs:      approx. 2000       not yet ordered, delivery time
                                    small (4 week to get first boards)  
  

      Capacitors    70000           70000 pieces have been oredered
                                      

      adapter cards
                   approx 7500      4500 pieces still missing 

 
      connectors   approx 7500       7800 connectors are ordered
                                     (from Harting instead of
                                                       3M as before)
      
      Coax Cable   approx 35 km        30 km have been ordered 
 

      HV cable     approx 5 km        according to Mario
                                      Hamburg has ordered enough ???  
     ------------------------------------------------------------------- 
                                   

  1.4 Open questions:

      1. plastic bags to pack the HV boards after cleaning and testing
         -> for immediate usage we should  buy some freezer-bags
         Christine Joithe should find a bag with a zipper. 
       
      2. The length of the HV cables is not yet known. A.Lanyov
         should provide the numbers.
   

  
  2. ASD8 power distribution boards:
  ----------------------------------

  2.1 Standard test calibration procedure was developed by Z.Zhu: 
        - check CAN interface + CAN ID setting 
        - enable threshold + threshold monitoring
        - calibration of ADC/DAC
        - longterm stability test of threshold and test-pulser


  2.2 Problems with the current board:

         - input resistor for the current measurement is 
           too large (voltage drop of 0.5 V)

         - threshold setting: threshold voltage breaks 
           down if there are more than 2 ASD8 connected
           -> higher capacity for the threshold driver 
              required.

         - a disconnection of the CAN bus cable leads 
           for certain CAN Id's to a floating threshold.
           -> next version should have a DAC strobe
              independent from the CAN ID.  

         - since the SLIO has only 5 analog inputs 
           we can NOT monitor +/-3V U+I and the 2 Uth
           The current implementation is measuring
           U,I (+/-3V) and 1 x Uth.
           -> in future it is better to give up one
           of the currents and to monitor both Uth.
           As current to monitor we should use the one
           sensitive to the TDC connection.

         - the control part needs +/- 5V power. Currently
           the +5V is taken from the TDC crate while for
           the -5V we use the -3.5V ASD8 power.
           This should be changed by using a DC-DC converter
           and using for both cases the +5V line. 

     
    In summary: there are still some improvements necessary before
    the board can be used in Hamburg.

 
           
  3. Test-pulse distribution: 
  --------------------------
  
  The PCBs have arrived and the assembly will start.
  We still miss the Harting connectors. Since they
  are only for the power connection we can already
  test the boards with soldered power lines.

         
 
  4. Analog Readout:
  ------------------

  4.1 Fe55 sources:
      K.Berkhan will investigate the conditions under which we 
      are allowed to install radiative sources (Fe55) inside
      the modules. Contact person at DESY: Herbert Dinter 
      from the radiation protection group. 

  4.2 Analog channels:
      The channels must be defined giving the module name 
      and the channel number:

      e.g.: channel # 17  in Module:  -M2-1-01-09
      (for non experts of the naming conventions: 
       -M2 = SL MC2 -x side
        1  = stereo layer 1
        01 = module # 01
        09 = in sector 09 )

     During cabling of the HV boards the corresponding channel 
     must be kept free. Instead a 3 m longer coax cable must 
     be added to the plastic bag. When soldering the HV board
     to the module also the 3 m long coax cable for the analog
     channel must be connected.   

     Klaus Berkhan will specify the analog readout channels 
     in the above specification.