=== Minutes of 2000/05/18 SVD meeting ===

Attendance: Alimonti, Asano, Hazumi, Ishino, Kaneko, Kawasaki, Nakamura,
Satpathy, Stanic, Tajima, J.Tanaka, M.Tanaka, Tsuboyama, Varner, Yamada,
Yamamoto, Yokoyama, Zontar.
(People offsite is not listed completely).

SVD1.2 status
1. Radiation&BG status (Zontar)
Total dose is now 82 kRad. One third of dose is due to accidents
(earthquakes, magnets down due to water problems) in last 3 weeks. It looks
like gain drop is smaller than the value expected from the dose. Beam abort
rate seems normal. Occupancy is 1% for layer 1, 1.5% for layer 2 and 2.5%
for layer 3 with random trigger events. Occupancy increases by 0.5-1% for
hadronic events. Occupancy can be reduced by 30% if the threshold of total
cluster energy is set at 30 keV which is consistent used for the offline
tracking and seems very efficient.


2. SEU  (Kawasaki)
We still have problem with new TTM firmware with 8 bit counter. It functions
well if there is no beam. It becomes unstable with beam. The problem may be
caused by TTM when trigger is issued at high rate. It was suggested to check
if it is due to beam or trigger.


3. April/1st accident conclusions (M.Tanaka)
Direct radiation damage of the VA1 and DSSD leak current are ruled out as a
cause of the gain loss. There was leak current imbalance between p- and
n-side. After this incident, power supply was turned off due to beam abort.
When the power is turned on, the Iss increased by 1A. The Idd decreased at
the same time. This can be explained by very negative voltage on the gate of
input FET. This could burn Vss power line. Or, gate can be broken by large
Vgs if Vgs get further negative by turning off the power (turning off Vss
means Vss moves from -2V to 0V).


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SVD2 status

SVD2 DSSD radiation damage (Kaneko)
Damage rate are measured to be 0.6 nA/kRad/cm^2 for test chip,
1.6 nA/kRad/cm^2 for prototype, 3.4 nA/kRad/cm^2 for S6936. We may have less
shot noise contribution than we expected.


SVD2.0 Beampipe R&D (Yamamoto)
Sanjay finished saw-tooth design study using EGS. It was found that
back-scattering is more important than tip scattering. Copper is better than
Aluminum below 8 keV (K-edge). We do not expect incoming SR greater than 3
keV. Incident angle of saw-tooth is being optimized against HOM.
Tom and Sanjay is performing ray-tracing SR from BC3 and QC's for mask
design.
Hulya confirmed Hamasaki's results. Energy cut-off is being optimized for
CPU time saving. SVD2 geometry is being implemented.
Gas(He) cooling seems to be marginal. Aluminum mock is under construction
for PF200 cooling test. FEA analysis is underway by Marc. RFQ is submitted
for initial study by Electrofusion. Cooling tube routing design is in
progress.