FTPC calibration status & plans for Y03 Joern Putschke for the STAR FTPC group
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Transcript of FTPC calibration status & plans for Y03 Joern Putschke for the STAR FTPC group
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FTPC calibration status & FTPC calibration status & plans for Y03plans for Y03
Joern Putschke
for the STAR FTPC group
STAR Calibration Meeting 2002November 7, 2002
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November 7, 2002 STAR Calibration Meeting 2
Overview
• The Forward-TPC layout
• Laser Calibration
• “TimeStep problem”
• DCA distribution
• ToDo list & Plans before Y03 physics run
• Online tool & calibration runs in Y03
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November 7, 2002 STAR Calibration Meeting 3
The Forward-TPC layout
• 2 FTPCs • 2.5 < || < 4.0• 6 azimuthal sectors (~60 deg.) with 5*2 rows in
z- direction• electron drift ~1/r and to magnetic field
Volume inner radius 7.73 cm outer radius 30.05 cm
chamber length 120 cm (|z| = 150 – 270 cm)
acceptance =2.5 –4.0 (=2° - 9°) Field properties
drift cathode voltage 10-15 kV
drift electrical field 240-1400 V/cm (radial, beam)
Solenoid magnetic field 0.5 T (|| beam) Gas properties
gas mixture Ar(50%)-CO2(50%) drift velocity 0.3 – 2.0 cm/s
trans. Diffusion DT 100-130 m/cm long. Diffusion DL 100-130 m/cm
Lorentz angle 4 deg.
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November 7, 2002 STAR Calibration Meeting 4
Radial drift / space point reconstruction
co n st)()(v
co n st)(vv1
rFBrqFBE
rr
E
D
DD
l e )L o r e n t z a n g(
)(
r)(v
)(
L
D
0
00
r
r
LD
r
r
r
rD
d rrr
rd rd trT
vD(r) and D(r) have to be known with high accuracy
using MAGBOLTZ calculations
How to check ?
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November 7, 2002 STAR Calibration Meeting 5
Laser residuals & momentum resolution
Residuals of the inclined laser tracks
d e g .
re s [d eg .]
cm
re s [cm ]r
r
1/p [1/GeV]-0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5
coun
ts
0
50
100
150
200
250
300
350
400 0 .0 8 2 1 /G e V
Momentum resolution
2LBpA
pdp
B : m a g n e tic f ie ldA : a c c u ra c y in p o in t m e a s u re m e n t a n d n u m b e r o f u s e d p o in tsL : t r a c k le n g thp : tra n sv e r se m o m e n tu m
momentum resolution and residuals reach design goals (for laser tracks) !
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November 7, 2002 STAR Calibration Meeting 6
Deflection angle
Comparsion of the measured deflection anglevs. raidus and MAGBOLTZ calculations
• differences between different laser calibration sets in the azimuthal direction due to mirror movement in laser system
• tool to compare different MAGBOLTZ versions calculations
rad 0.0062296,,,
PadRadiansPer
PadRadiansPerpadpad fullfiedBnofieldBlaserD
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November 7, 2002 STAR Calibration Meeting 7
Residuals of different intensity laser tracks
charge (cluster geometry) dependence of residuals explains the poor space point resolution in Y02 (factor of 2) because of low gas gain (for safety reasons due to earlierproblems with contaminated gas) !
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November 7, 2002 STAR Calibration Meeting 8
Vertex reconstruction of minBias data
• possible explainations: drift velocity change, wrong B-field distortion corrections (bug in geant magnetic field table ?)
zvertex,FTPC-zvertex,TPC [cm]
ReversedFullField Run 311
west
east
zvertex,FTPC-zvertex,TPC [cm]
FullField Run 313
west
east
but effect could not be explained at current calibration level !
tool to adjust drift velocity (and t0) with physics data
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November 7, 2002 STAR Calibration Meeting 9
“TimeStep problem”
azimuthal dependence of the TimeStep/inner radius of reconstructed hits !
AuAu minBias(radialStep)
AuAu central(timeStep)
pp minbias(radialStep)
No idea …(maybe a new one, thanks Dave)
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November 7, 2002 STAR Calibration Meeting 10
DCA distribution(ReversedFullField Run313)
west east
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November 7, 2002 STAR Calibration Meeting 11
ToDo list
priority task
h timeStep problem
h pulser/electronic check
h magboltz I/II (laser/DVM)
h laser calibration
h vertex B-field problem
h FTPC residuals
h realistic simulations
m definition of FTPC pico events
m new QA histograms
m Tracker noise/holes
m gas, T & p simulations studies
m embedding (infrastructure)
lr ITTF
also in TPC ???(heard about …)
There are a lot of tasks more …
need help from outside FTPC group (small group) !!!
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November 7, 2002 STAR Calibration Meeting 12
Plans before Y03 physics run
1. Pulser runs– check exchanged FE cards– gain correction
2. Laser Calibration (as soon as possible)– gain scan residuals (azimuthal reproducibilty of laser tracks)– zero field laser look at timeStep problem– zero field laser and drift velocity mointor
fix drift velocity and MAGBOLTZ– B-field scan check ExB corrections– laser during data runs spacecharge
3. Data calibration runs– gain scan cluster shapes and residuals– B-field scan solve vertex-z position puzzle– zero field run, laser and drift velocity mointor
fix drift velocity and MAGBOLTZ
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November 7, 2002 STAR Calibration Meeting 13
Online tool & calibration runs in Y03
• online tools– use event pool and FTPC clf & tracker (not ready yet)– laser calibration online tool possible with L3 ?– integration into L3 (DAQ 100) need separate hitfinding
module - maybe not for dAu (has to be checked)
• calibrations runs – daily laser runs to check drift velocity and ExB– zero field physic runs– combination zero field physic and laser runs
as often as possible
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November 7, 2002 STAR Calibration Meeting 14
The STAR FTPC group
• Volker Eckhardt• Maria Mora Corral• Markus Oldenburg • Joern Putschke• Janet Seyboth• Peter Seyboth• Frank Simon
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November 7, 2002 STAR Calibration Meeting 15
Vertex reconstruction
• transform to STAR coordinate system• compare FTPC and TPC vertex pos.• a tool to check our drift velocity with real data
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November 7, 2002 STAR Calibration Meeting 16
Reconstruction qualityResiduals Cluster geometry (on track)
Why are the residuals a factorof 2 larger than expected ?
Residuals r
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November 7, 2002 STAR Calibration Meeting 17
Laser shift
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November 7, 2002 STAR Calibration Meeting 18
Residuals of different intensity laser tracksResiduals
r
padwidth timewidth
selection of a low intensity laser track (black) with cluster geometry similar to physics data to compare with the high intensity laser track (red) factor of 2 visible