calibration of a modular straw-tube-tracker for the cosy-tof experiment

Calibration of a Modular Straw-Tube-Tracker for the COSY-TOF Experiment

Sedigheh Jowzaee

3-6 June 2013, Symposium on Applied Nuclear Physics and Innovative Technologies, Krakow, Poland

INTERNATIONAL PHD PROJECTS IN APPLIED NUCLEAR PHYSICS AND INNOVATIVE TECHNOLOGIESThis project is supported by the Foundation for Polish Science – MPD program, co-financed by the European Union within the European Regional Development Fund

Outline

• COSY facility & COSY-TOF Spectrometer

• COSY-TOF Straw-Tube-Tracker (STT)

• STT calibration goal

• Calibration approach

▫ Apply Corrections

▫ Find R-T correlation

2

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

• Strangeness physics pKppp

3 m

4

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

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Amplifier-shaper-discriminator chip ASD-8

Preamplifier Time measurement

ASD-8 input board:Impedance matching and shaping for ASD-8 chip

ASD-8 chip:Short measurement time (10 ns)Good resolution (25 ns)Low operational threshold (2 fC)Shaper with pole-zero cancelation

In the vacuum tank Out of the vacuum tank

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

Wiree

raw TDC spectrum for 5.106 hits in the 2704 single straw tubes

TDC spectrum after removing multiple hits

Using the common-stop readout of the TDCs, higher values correspond to shorter drift times

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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 10

Calibration• Signal width cut effect

TDC spectrum before the signal width cut

TDC spectrum after a cut on the signal width 11

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

▫ Offset= 780 ns(arbitrary)-Ref. point

Turning pointσ

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x

dttxErf

noiseturningt

Erfamp

tfunctionfit

)exp(2

)(1

))2

(1(2

)(

2

complementary error function

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

14

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)

minRN

N)R(R=(t)dtv=)r(t

tot

iwiretubedrifti

Ni: no of tracks in t0 to ti

TrackStraw Tube

Risochrone

Rtube

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Isochrone radius: cylinder of closest approach of the particle track to the wire

TDC time vs isochrone radius for double layer-13

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

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STT resolution• 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

TDC time vs residual for double layer-13 18

Resolution vs isochron radius for double layer-13

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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Thank You

3-6 June 2013, Symposium on Applied Nuclear Physics and Innovative Technologies, Krakow, Poland

INTERNATIONAL PHD PROJECTS IN APPLIED NUCLEAR PHYSICS AND INNOVATIVE TECHNOLOGIESThis project is supported by the Foundation for Polish Science – MPD program, co-financed by the European Union within the European Regional Development Fund

Back up

STT inefficiency

• STT is the base detector for track reconstruction• Low detection efficiency or not response

▫ Mechanical problem or electronics

Electronics problem

Mechanical damage

noise

47.106 hits

• 2 electron clusters

• error function • complementary error function