The currently recommended values for tpc tracking (in particular for TPM1 and TPM2) have been deduced
looking at several zero-file runs, and field runs at different angles, and revisiting the survey and complementing measurements.
Additionaly they have been compared to the rudimentary survey done before the run, as well as performing measuremnts
on TPC timing etc, looking at positions of clusters within TPCs etc. Some of the information is also pertinent to the
forward TPCs.
a) The TPM1,TPM2 values are for 90 degrees
b) The small tpm2 rotation is consistent with the survey value (of -.4 deg)
c) The heights are derived from the survey top's and internal geometries.
(design drawings + later checks). All TPCs
d) The timing offsets for the SCA readout start are from a measurement of T1. It is estimated the other TPCs at most
can deviate by 50 nsec.
e) Drift velocities have been found for tpm1 as the 'best value' the consistently
-- get the track projection near Ty~0
-- the bottom cluster y (in local coordinates between -10 to -9 cm) [physical constraint]
-- reasonable matching with TPM2
-- matching with Tpm2 tracks.
f ) TPM2 average velocities from projection and matching with fibres and tof calibration slats.
g) It is apparent the changes in Vdrift has occured over the running period even within hours, and calibrations
will have to be done. Also for at least Tpm2 there are x,y dependent effects in the tracking that eventually has to be
taken care of. This should also be investigated to wehat degree this is present in T1,T2 now with the fibres avaliable.
h) The quoted values for Vdrift for T1 and T2 are speculations The 1.6 from the presently used values. The larger value
comes if one assumes that the lowest y-values comes from near the bottom cathode plane (at -10 cm). The other
T1, T2 values should be used.
i) There are several effects NOT understood for the MRS tracking as the mentioned x,y variations (as observed by track
projection with fibres), the change of matching angle vs track angle.So the present geometry though reasonable and
consistent is not the final word on this story.
Eun-Joo, JHLee and FV
---------------------------------------------------------------------------------
TPM1
geo x (90) 0
y(90) 1.8 +-0.1
z(90) 94.6
angle 90
params fTimeOffset 1030 +-50
fTimeBase 12 +-.2
fDrift 1.7 +-0.05 Time dependent?
TPM2
geo x (90) 0
y(90) 2.05 +-0.1
z(90) 286.6
angle 89.75 +-0.05
params fTimeOffset 1030 +-50
fTimeBase 11.8 +-.1
fDrift 1.6 +-0.05 Time dependent?
T1
geo x (90)
y(90) 0.8 +-0.1
z(90)
angle 1.95
params fTimeOffset 1030 +-20
fTimeBase 11.8 +-.1
fDrift 1.6-1.9 +-0.05 Time dependent?
T2
geo x (90)
y(90) 0.8 +-0.1
z(90)
angle
params fTimeOffset 1030 +-50
fTimeBase 11.8 +-.1
fDrift 1.6-1.9 +-0.05 Time dependent?
------------------------------------------------------
Flemming Videbaek
Physics Department
Brookhaven National Laboratory
tlf: 631-344-4106
fax 631-344-1334
e-mail: videbaek@bnl.gov
This archive was generated by hypermail 2b30 : Thu Oct 18 2001 - 15:58:53 EDT