Transcript Calibration of the COSY-TOF straw tube tracker

INTERNATIONAL PHD PROJECTS IN APPLIED NUCLEAR PHYSICS AND INNOVATIVE TECHNOLOGIES
This project is supported by the Foundation for Polish Science – MPD program, co-financed by the European Union within the European Regional Development Fund
Calibration of a Modular Straw-TubeTracker for the COSY-TOF Experiment
Sedigheh Jowzaee
3-6 June 2013, Symposium on Applied Nuclear Physics and Innovative Technologies,
Krakow, Poland
Outline
• COSY facility & COSY-TOF Spectrometer
• COSY-TOF Straw-Tube-Tracker (STT)
• STT calibration goal
• Calibration approach
▫ Apply Corrections
▫ Find R-T correlation
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COSY facility
• COSY: Cooler Synchrotron
• Polarized and unpolarized beams of
protons and deuterons
• Momentum range 600 MeV/c to 3.3
GeV/c
▫ medium energy physics program
• Cooler & storage ring circumference
184 m
• High precision beam by:
▫ electron and stochastic cooling
• 4 internal experiment
▫ ANKE, PAX, WASA, EDDA
• 2 external experiment
▫ TOF, PANDA test
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COSY-TOF Spectrometer
3m
• Strangeness physics
pp  pK  
p 
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COSY-TOF STT
• Installed in vacuum tank
• Consists of 2704straw tubes with
Ø=10 mm & 1050 mm length
• Organized in 13 double-layers
• Filled with Ar/CO2 gas at 1.2 bar
overpressure
• Fixed in 3 orientations with
angle 60˚ to each other for 3D
track reconstruction
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STT readout electronics
In the vacuum tank
Preamplifier
ASD-8 chip:
Short measurement time
(10 ns)
Good resolution (25 ns)
Low operational
threshold (2 fC)
Shaper with pole-zero
cancelation
Out of the vacuum tank
Amplifier-shaperdiscriminator chip
ASD-8
Time measurement
ASD-8 input board:
Impedance
matching and
shaping for ASD-8
chip
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STT information
• Information from straws
Beam hole
leading edge
trailing edge
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Calibration motivation
• Reconstruction of events with STT at COSY-TOF
▫ Precise reconstruction of vertices
▫ Reducing background for better resolution
▫ Event analysis based on the vertices reconstruction of the charged final state
particles (p, K, Λ p, π)
▫ Precise calibration needed
• Different effects should be considered
▫
▫
▫
▫
Multiple hits removal
Signal width cut
Electronics offset correction
Straw layers position correction
• pp elastic events measured in Fall 2012 at pbeam=2.95 GeV/c are
analyzed for the calibration of the STT
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Calibration
• Multiple hits removal
Track
Straw
Tube
e
Wire
Using the common-stop
readout of the TDCs,
higher values
correspond to shorter
drift times
raw TDC spectrum for 5.106 hits in
the 2704 single straw tubes
TDC spectrum after removing
multiple hits
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Calibration
• Signal width cut
▫ Some noisy hits remain after
removing multiple hits
▫ STT electronics readout has
a 5ns signal width limit
between leading and
following trailing edge
▫ Only noise can produce
width lower than 5ns
▫ Record leading edge time
without trailing edge time
▫ The width spectrum was cut
for less than 5ns
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Calibration
• Signal width cut effect
TDC spectrum before the signal width cut
TDC spectrum after a cut on the signal width
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Calibration
• Electronics offset correction
▫ Different readout modules
▫ Correction with fit method
▫ Error function was fitted to the
leading edge of TDC spectrum
for each straw
▫ χ2/NDF ≤2
▫ Ref. point=turning point of
error function + 1σ
fit  function(t ) 
1  Erf ( x) 
2

am p
t  turning
(1  Erf (
))  noise
2
2

 exp(t
2
)dt
complementary error function
Turning point
σ
x
▫ Offset= 780 ns(arbitrary)-Ref.
point
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Calibration
• Electronics offset correction
▫ Fit-functions were defined for empty or improper fitted straw tdc spectra
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Calibration
• Electronics offset correction effect
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Drift time
• Corrected drift time spectra
▫ Maximum drift time 145 ns
▫ Same drift time spectrum
within each double layer
▫ Irregular shape and tail part in
first 4double layers
▫ Improper recognition of first
hits due to low sensitivity of
their electronics
▫ Events mixing and tail pile-up
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Self-calibrating method
• Main aim: determination of the
correlation between the drift
time and the isochrone radius
• Isochrone radius was
calculated for each bins of drift
time (homogeneous illumination
assumption in whole straw)
r(ti ) =  vdrift (t)dt= (Rtube  Rwire
N

)
R
i
Ntot
Track
Isochrone radius:
cylinder of closest
approach of the
particle track to
the wire
Ni: no of tracks in t0
to ti
min
Straw
Tube
Risochrone
Rtube
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Distance to track calibration method
•
•
Track reconstruction with averaged R-T curve from self-calibrating method
Track parameters were analyzed to find the most probable correlation between TDC
time and isochrone radius (track to wire distance)
TDC time vs distance to wire for double layer-13
TDC time vs isochrone radius for double layer-13
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STT resolution
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•
•
•
•
In Ideal case the R-T curve should be same for all straws
The averaged R-T curve from 3 groups of double layers was used for all straws
Residual=|d| – r d: track to wire distance, r: isochrone radius
Spatial resolution: width of the gaussian+pol4 fit functions to the residual
distribution as a function of TDC time
Average resolution at 0.25 cm over all double layers is 142 ± 8 µm
Resolution vs isochron radius for double layer-13
TDC time vs residual for double layer-13
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Summary
• Signal width cut is effective to clean noisy channels
• Electronics offset correction was applied well to reduce the systematic
error from different electronics modules
• For the first time the same Self calibrating R-T curve was used for track
reconstruction within each double layer
• Improved Average spatial resolution 142 ±8 µm at 0.25 cm over all
double layers was found compare to the last calibration with same beam
momentum (170 ±11 µm) by taking an average R-T curve
• The new calibration improvement is studying with comparison of pp
elastic parameters (i.e. vertex resolution) to the former work.
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INTERNATIONAL PHD PROJECTS IN APPLIED NUCLEAR PHYSICS AND INNOVATIVE TECHNOLOGIES
This project is supported by the Foundation for Polish Science – MPD program, co-financed by the European Union within the European Regional Development Fund
Thank You
3-6 June 2013, Symposium on Applied Nuclear Physics and Innovative Technologies,
Krakow, Poland
Back up
STT inefficiency
• STT is the base detector for track reconstruction
• Low detection efficiency or not response
▫ Mechanical problem or electronics
noise
47.106 hits
Electronics problem
Mechanical damage
• 2 electron clusters
• error function
• complementary error function