Identification of Charged Particles in Straw Tube Detectors

Sedigheh Jowzaee

Jagiellonian University

MESON2012 Conference, Krakow, Poland, 31May-5June 2012

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

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Outline

• PANDA experiment• Straw Tube Tracker• Straw tube simulation• Straw front-end electronic• PID Methods

• Separation π-K-p• Summary

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1. PANDA Experiment

• Interaction of antiproton with momentum range (1.5-15 GeV/c) • Hydrogen Target

• Charmonium spectroscopy• Exotic hadrons (hybrids,

glueballs, multi-quark states)• Strange and charmed baryons• Structure of the nucleon

• Nuclear Target• Hadron properties in the nuclear

medium• γ -ray spectroscopy of

hypernuclei

PANDA Program

Two-bodythresholds

Molecules, Multiquarks

Hybrids

Glueballs

qq ̄ Mesons

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1. PANDA Experiment

• Full angular acceptance and angular resolution• Particle Identification (p,π,K, e, μ) in the range up to ~ 8 GeV/c • High momentum resolution

PANDA (antiProton Annihilation at Darmstdat) Detector

Target spectrometer Forward spectrometer 4

2. Straw Tube Tracker

• STT layout• 4636 straw in 2 semi-barrels around

beam/target pipe• 23-27 planar layers in 6 hexagonal

sectors• Length: 1500 mm+150 mm (read-

out)• Angular acceptance: near 4π

• FST layout• 10752 straw tubes• 6 tracking station: 2 before, 2 inside

and 2 after the dipole magnet• 4 double layers per tracking station• Angular acceptance: ±5A vertically,

±10A horizontally

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2. Straw Tube Tracker

• Straw tube structure• Al-mylar tube, 29 μm thick, Ø=10 mm• Gold-plated anode, Ø=20 μm• End plug (ABS thermo-plastic)• Crimp pin (Cu, gold-plated)• Gas tube (PVC med, 150 μm wall)• 2.5 g weight per tube

• Advantages of straws• Modules (easy to exchange, high

flexibility)• Low mass (self supporting by gas

overpressure )• High rates (1 MHz/wire)

• Low ageing• Fast readout (pulse shaping and

digitalization)

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3. Straw Tube Simulation

• Garfield 9: program for the detailed simulation of gas detectors• Simulation of transport properties of electrons and ions with new version

Magboltz 8.9.5• Gas mixture:

• 90% Ar, 10% CO2 (the best gas mixture for high-rate, no polymeric reactions )

• Temperature 300 K, absolute pressure 2 atm

Pure Argon

Argon+ 30% CO2

10%

2%

1%

20%

10%

20%

Pure Ar

50%

Ar+75% CO2

Drift velocity Townsend

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3. Straw Tube Simulation

The gain curve with 0%, 20%, 30%, 40%, 60% and 100% Penning rate

No penning transfer

Full penning transfer

Gas gain simulation

Comparison the measured gain with Diethorn’s formula

Agreement with 34% penning rate

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• The first prototype new front-end chip fabricated in AMS 0.35 µm technology

• Preamplifier with variable gain

• CR-RC2 with variable Tpeak

• Tail-cancelation with 2 variable time constants• Baseline stabilizer• Leading edge discriminator for timing• Buffered analog output

4. Straw Front-end Electronic

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4. Straw Front-end Electronic

• Each ASIC includes 4 channels

• Digital LVDS & Buffered analog outputs

• Flash program memory ATMega controller for ASIC parameters (gain, shaping)

• Baseline and threshold set with external voltage source

• Optimum configuration

The ASIC test-board v. 2

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Transfer function produced by injection of “delta like” pulse to front-end

4. Straw Front-end Electronic

The transfer function

)()()()(

)()()(

)()()(

twtVttIfor

tdtIttwtV

sIswsV

out

inout

The 55Fe pulse convoluted by transfer function

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4. Straw Front-end Electronic

• Minimum ionizing proton beam of the intensity 1.2 MHz/straw

• signals were recorded by means of fast sampling ADC in long window of 5μs

• Baseline keeps always stable

• Energy resolution of the straws would not be affected in high counting rates

The high-rate test

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5. PID Methods

• Energy loss: below 1 GeV

• PID based on dE/dx:

TOT ? Q

Straw Tube Tracker (STT)

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5. PID Methods

• Response of 24 single straws to 400 tracks• Set the threshold as low as possible for high position

resolution• Correction to distance dependence• Truncated average for 24 straw layers

TOT simulation

Straw

Tracks

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5. PID Methods

Single straws response for 0.7 GeV/c particles before distance correction

After distance correction

After truncated average by removing 30% of the highest numbers

Reasonable for PID15

5. PID Methods

TOT spectra measured with 55Fe source shows good agreement with simulation for HV 1750 V and threshold based on 20 primary electrons

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5. PID Methods

• TOT vs. input charge plot shows good agreement between simulation and test with 55Fe source

• For high input charges, the measured TOT deviates from simulations due to saturation of pulses in the shaper

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6. Separation p-K-π

Separation power for p-π, p-K and π-K pairs based on TOT (■) and charge (▲) measurement. The threshold level was set based on 20 primary electrons

2/)(

)()(),(

BA

BMeanAMeanBASeparation

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6. Separation p-K-π

• The separation power for K-π and p-K pairs calculated using TOT and Q are different due to saturation of TOT as a function of Q for high energy deposits in the straws

• Saturation leads to smaller relative smearing and lower difference of the corresponding mean values of TOT than Q

0.3 GeV/c● proton● kaon● pion

0.7 GeV/c● proton● kaon● pion

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6. Separation p-K-π

The Separation power for π-K pair based on TOT with threshold levels based on 20 and 10 primary electrons and comparison with Q

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7. Summary

• Modular straw tube trackers are good tools for tracking and identification of particles in large scale experiments

• New front-end chip works very well for straw read-out

• Distance correction improves the results of TOT and Q for PID

• The separation power based on the TOT and Q measurements are comparable in the investigated momentum range 0.3-1.0 GeV/c

TOT works very well for PID in straw tube trackers

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Email: sedigheh.jowzaee@uj.edu.pl

THANK YOU FOR YOUR ATTENTION

MESON2012 Conference, Krakow, Poland, 31May-5June 2012 22

5. PID Methods

Tot vs. drift time for Muon 1GeV/c passing with 30 degree to wire

Drift time spectra for Muon 1GeV/c

TOT & Drift time simulation for cosmic rays

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6. Position Resolution

threshold based on 20 primary electrons

proton 1 GeV/c

threshold based on 10 primary electrons

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1. PANDA Experiment

• Full angular acceptance and angular resolution• High momentum resolution• Particle Identification (p,π,K, e, μ) in the range up to ~ 8 GeV/c

PANDA (antiProton Annihilation at Darmstdat) Detector

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3. Straw Tube Simulation

• Adding CO2 to Ar is efficient way to reduce the diffusion coefficient

15%

20%

50%

Ar+10% CO2

Longitudinal diffusion Transverse diffusion

15%

20%

50%

Ar+10% CO2

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3. Straw Tube Simulation

• CO2 as a quencher for the good drift properties and low ageing

• Ar is a main component that dominantly ionized

10%

20%

50%

Ar+ 75% CO2

attachment Ionization rate

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4. Straw Front-end Electronic• Different settings of time constants in tail-cancelation and shaping part• Optimum configuration based on fast shaping and higher amplitude and lower

undershoot

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