Meeting on alignment electronics 25/01/2006, Cascina
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Present: 
Jo van den Brand, Tjeerd Ketel, Harry van der Graaf,
Benoit Mours, Matteo Barsuglia, Michele Punturo, Raffaele Flaminio,
Gianfranco Giordano, Ennio Turri, Adalberto Giazotto,
Julien Marque, Henrich Heitmann, Maddalena Mantovani,
Edwige Tournefier, Sebastien Vilalte, Flavio Nocera

Conclusions:

The alignment electronics consist of 
 A. quadrant diode front ends
 B. demodulator boards
 C. phase shifter boards
 D. translation stage controllers

Need of the alignment group
A. Replacing the Si QD by a InGaAs QD for improving the quantum efficiency
   and reducing the bias voltage (higher light power possible).
   Improving the transimpedance preamplifer: reduce the DC offset (presently
   600 mV), improve current noise (presently 5 pA/rtHz). 
   To be decided if a rotation of the quadrant diode from "X" to "+" 
   configuration is necessary. The information will be available for the 
   next Virgo week.
B. Demodulator boards don't need to change, but after installation of 9th 
   quadrant diode there will be no spares anymore. 2 new spares need to be 
   constructed, for each of both demod. board types (total 4 spares).
C. Annecy is redesigning their "LO" boards, which will be compatible with
   the alignment system and can be used as 2-channel phase shifter boards.
   So no further action is required on phase shifter boards.
D. For the 9th quadrant diode, a translation stage controller drawer has been
   installed in the DAQ room, which can control also a 10th quadrant diode. 
   Enough commercial electronics cards are available for constructing one 
   more t-stage controller drawer. These cards will serve as spares. 
   So we don't foresee any action on the t-stage controllers. 

New responsibilities
A. NIKHEF will design, test, and fabricate new front end modules. 10 modules
   + 2 spares are needed, + 2 modules for eventual future needs. 1 year is 
   necessary for the full process. During this time, the 10th front end, 
   available in Frascati, will be repaired and will then serve as spare at 
   Cascina. 
      For improving the noise of the DC signals, the Annecy preshaping boards 
   will be used in front of the ADC's. 
B. NIKHEF will produce 2+2 spares for the demodulation boards, based on the 
   diagrams from Frascati. Particular care is required for the HF shielding 
   with respect to the VME environment. 
      The spare production should be done with a high priority; in the mean 
   time, in case of dem.boards failure, a quick reparation has to be done, or 
   the number of used QD's has to be reduced. 
C. Annecy will furnish the new LO boards as spares for the Frascati phase 
   shifters.
D. NIKHEF will be responsible of the translation stage electronics in case of 
   necessity of redesign or massive failure. For day-to-day necessity, the 
   already available spares should be enough.