Minutes of March 13 AFE meeting: (M. Johnson, P. Rubinov, A. Bross, G. Ginther, H. Weerts, J. Kotcher, J. Yu, J. Blazey, L. Babukhadia, L. Duflot, P. Grannis) NOTE: THE NEXT TWO MEETINGS WILL BE HELD ON THURSDAY MARCH 22 AND THURSDAY MARCH 29. WE HOPE TO BE IN A POSITION TO MAKE A DECISION TO PROCEED WITH STUFFING ON MARCH 29, PROBABLY IN THE TRIGGER MEETING SLOT AT 3:30 (9TH CIRCLE). +----------------------------------------------------+ | We have not been in contact with Sanmina, so | | have to assume that board production is proceeding | | and that proceeding to stuffing will occur on | | March 27, two weeks from today, as planned. | +----------------------------------------------------+ Plots (Laurent) from fitting photopeaks on 16 illuminated channels (Paul, John) from one MCM were shown by Marvin. The masks were made to put light on to every fourth channel. Example plots will be available at the AFE web site: **NOTE THE NEW URL**: http://d0server1.fnal.gov/users/grannis/afe/afe.html Although there were problems this past week with an unknown source of noise that was found on testing the 3.3V operation of the transfer gate to SVX, it is now believed that this problem is external to us. (3.3 V is the design for RevC boards.) Debugging this problem set us back a few days. The fitted peaks on the better channels have noise sigmas of about 2fC (referred to input to MCM), and are as good as theoretically expected. About 2 of 16 channels have their photopeaks smeared out. A couple have rather odd structures in the photopeaks. But the general result is very encouraging and if found for the full set of channels on a board will be acceptable. Tests showed that for 0.1% noise rates on channels with no light, the illuminated channels had efficiency at 98%. The discussion led to the statement that we do not need to demand 0.1% noise rate (see below). The light input was at about the 2pe level. The results were 'run by run stable'. No cross talk between digital channels was observed. All 8 MCMs have now been modified with coupling resistors to damp oscillations, so full board tests can proceed. A few problems need to be fixed with the working LH board. The RH board is operational, except for getting the cryo controls working. We hope this will be done in a day or so, and then testing of the pair of boards with all bias and temperature control can proceed. This remains an outstanding issue to certify the design for stuffing. There are nine prototype RevA boards at Lab 3, becoming ready for test. We discussed the full set of specifications for proceeding to stuffing boards at Sanmina. There are two classes of specs: those that are essential to pass, and those that require test measurements but are either of the sort that further work can make better, or not truly essential for CFT operation. In the first category are the mechanical, temperature/bias control, noise level, and performance of the discriminator signals and cross talk. The second category related to long term stability, behavior under background light rate, full digitized signal performance, rate of transfer of SVX data. Jerry had revised Fred's spec document and this was discussed at length. Jerry will provide the revised specs with signoff boxes for passage of the critical specs (or spaces for numbers corresponding to performance measures). These will be posted on the AFE page (above) as soon as they are available. One modification made was the noise specification. Alan proposed that we measure the threshold value corresponding to fixed noise rates (0. 5% was suggested in view of the several percent occupancies in CFT). The rms of the distribution of such threshold values is the quantity we want to control. The value for this rms is yet to be determined by Alan from simulations, and will be done in the coming week. We agreed that masks should be prepared to illuminate 1 out of 4 channels in all channels in an 8 MCM board (128 channels). Marvin said that John Anderson and perhaps Mike Matulik have agreed to visit Sanmina to discuss optimized production/stuffing schedules. The visit is not yet scheduled. We believe the optimum time for such a visit will be just before Sanmina proceeds to the stuffing phase. It may very well be useful to have a manager accompany the engineers to help work on possible incentives for faster production. We believe that digitized information from SVX should be adequate for calibration. We expect that we will transfer this information for data logging and use offline. Some discussion on the deadtime limitations that the 40 MHz transfer to VRB imposes occured, with the feeling that it will not be a problem (e.g. faster than silicon), but hard numbers were not available. Marvin said he would try to chase this. Alan presented a modified result on efficiencies with realistic input numbers for cosmic ray responses, measured waveguide attenuations of 8.1 m, AFE pe resolutions, smeared thresholds (by 10%), and estimated radiation damage rates. The efficiencies are integrated over the full rapidity of the tracker (-1.6