Minutes of AFE meeting 4/3/01

Fred Borcherding, Alan Bross, George Ginther, Jerry Blazey,
Harry Weerts, John Womersley, Hugh Montgomery, Thomas Nunnemann,
Paul Grannis

In Paul Rubinov's absence, Fred reported the progress in the last
few days on differential non-linearity.   Board #1 showed little signs
of DNL at DAB3.  It was taken to Lab 3 where it showed the structures
in digital response like board 5 had done, both with light pulses and
with CAL inject signals.  On return to DAB3, this board #1 showed the
DNL structures.

Board #2 was modified to adjust terminations on data valid (and
data lines).  For all tested channels, there was no sign of the DNL
symptoms.   Studies were conducted on all 8 MCM's of the board.   
This (right handed) board will be taken to Lab3 tomorrow
to run there with sine wave inputs on the CAL input.   Board 1 will be
brought back to DAB3 to work on its terminations to try to cure it as
well.  If successful, this board can be operated at Lab3 with light.

There was however evidence of feedthrough of the SIFT clock on the SVX
readout;  it is thought that this clock can be blanked off during
readout to cure this problem.

The temperature control software is not complete as far as we
understand at present (Stefan should comment here).  This is the
necessary condition for proceeding to discriminator tests with the
realistic left- and right-handed boards in Lab 3.

The masks needed for testing the discriminator threshold variations
are thought to be completed and ready;  Paul should comment if this is
the case.

We set a deadline of Thursday for return of a fixed LH board from DAB3
to Lab3 -- or return of an unfixed board that can still be used for
the discriminator output test.  In the case that we have no clear fix
to the DNL problem, we need to attempt to get an approximate
calibration from the channel run with larger SIFT-SVX transfer gain
where we think we saw photopeaks.   This can give an approximate
calibration of the pe/channel constant that can be transferred to
other channels by knowing the various VLPC gains.  
Fred is to make a plan/schedule for testing for the next week,
to be shown in the Thursday meeting (see below).

Sanmina seems to be near the end of the bare board production phase.
They are expected to complete this week.  However there are a few
issues remaining on components for stuffing.  It was suggested that
assembly may not begin until Apr. 16, but there is not a definite word
here.  Sanmina has not officially agreed to wait for our go-ahead, but
practically our input on the component issues would seem to assure
this.

Thomas Nunnemann agreed to work at high priority with Paul Rubinov
on testing the boards at the Lab3 cryotest stand.  Thomas knows much
of the system, including the analysis package for fitting photopeaks.
We hope that this addition will help the Lab 3 test procedures.

The decision not to pursue spare AFE8 boards for the CFT stereo
(CPS) means that at present we have no visible way to complete a full
fiber tracker readout without the AFE12 boards.  We went through the
likely schedule for completion of the AFE12 -- necessarily imprecise. 
We estimated that 6 weeks are needed to complete AFE12 motherboard
prototypes, another month for daughterboards.  A month of testing
prototypes would be necessary, followed perhaps by a 3 month cycle of
board production and assembly and a month or so of testing here.  This
brings us to near the end of the year without having the capability of
tracking in D0.  Some expressed dismay.   

Discussion turned to the possibility of deciding now to defer all work
on AFE12, and to decide to instrument at least the CFT stereo/CPS
cassettes with AFE8.  The FPS, if done with AFE8, would want to have
special design modifications to allow the cross-over channels.  This
modified design, or resuscitation of AFE12, would wait with lower
priority until the AFE8 for all CFT was going well.   A note
outlining the special constraints on the FPS cassettes due to
the cross-over channels was prepared by George Ginther and
Volker Buescher and is found from the main afe page.  In addition to
getting the CFT operational  as quickly as possible, benefits of such
a decision would include the possibility of saving money (AFE8's
cheaper than AFE12's), allowing some critical manpower to focus on
AFE8 production and tests. Downside factors are the loss of the dual
range operation of at least CPS, and difficulties of calibration of
the CPS (FPS). 

We plan a special meeting Thursday to consider this possible decision
further.   ***Salles DZero at 1-3PM ***