Together with Paolo Saggese, we did a measurement of the East-side
8th vertical counter lenghts on all 6 SMs and also differential measurements
(displacements) w.r.t. the lengths and positions of the corresponding 9th
counters. Since we did not have access to the body of the counters, we used
as reference points the caps at the end of the counters. These have a
29cm length (till the end of the tank, NOT the window which is another
~21cm inside the tank). In general, we found that the East 8th vertical
counters are ~20cm shorter than the rest of the verticals (9th, 10th, etc.)
A sketch of how the situation looks, as viewed using the passarela, follows.
Place, keep in mind that even though we were able to measure the 29cm
length of the cap, the ~21cm length of the distance from the tank end
to the window that separates the scintilant from the mineral-oil filled
part was obtained from the spare box that is on the Attico. We don't
have any reason to assume that this length varies from box to box;
if anybody remembers anything regarding this issue, please drop a line.
<- South face -> North face
External Tank Scint. Scint. Tank External
Cap End Window Window End Cap
xE09 |<-------------- cap-to-cap length -------------->|
xE09 |<-29cm->|21cm|<----- ~1115cm ----->|21cm|<-29cm->|
xE09 | |
xE09 |--------|----|--------- ~ ---------|----|--------|
xE09 | | | | | |
xE09 |--------|----|--------- ~ ---------|----|--------|
xE09 | |
South->| |<-displacement North->| |<-displacement
External Tank Scint. Scint. Tank External
Cap End Window Window End Cap
xE08 |<----------- cap-to-cap length ----------->|
xE08 | |
xE08 |<-29cm->|21cm|<-- ~1095cm -->|21cm|<-29cm->|
xE08 |--------|----|------ ~ ------|----|--------|
xE08 | | | | | |
xE08 |--------|----|------ ~ ------|----|--------|
xE08 | |
Here are the results in details. All figures are in cm.
Cap-to-cap North-displacement South-displacement
-------------------------------------------------------
1E08 1195 8.0 12.0
1E09 1215
-------------------------------------------------------
2E08 1195 9.0 12.0
2E09 1216
-------------------------------------------------------
3E08 1198 8.5 10.5
3E09 1217
-------------------------------------------------------
4E08 1196 11.0 10.0
4E09 1217
-------------------------------------------------------
5E08 1196 22.5 -2.5
5E09 1216
-------------------------------------------------------
6E08 1196 12.0 7.0
6E09 1215
-------------------------------------------------------
It is quite hard to give an estimate of the measurement error, but
I would say +-2cm for the overall tank lengths and +-0.5cm for the
displacements is a reasonable one.
Tomorrow, we plan to do the same set of measurements for the West
side counters. Then, the CALMOD (geometry section) needs to be
changed, the calibration software to be run and analysis needs to
be done in order to see if these ~20cm difference have any effect
at all.
Regards,
Ioannis Katsavounidis