1. Identification of Charged Particles in Straw Tube Detectors
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
Identification of Charged Particles in Straw Tube Detectors
Sedigheh Jowzaee
Jagiellonian University
MESON2012 Conference, Krakow, Poland, 31May-5June 2012

2. Outline PANDA experiment Straw Tube Tracker Straw tube simulation
Straw front-end electronic
PID Methods
Separation π-K-p
Summary

3. 1. PANDA Experiment PANDA Program Nuclear Target
Interaction of antiproton with momentum range ( 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
Two-body thresholds Molecules, Multiquarks Hybrids Glueballs qq̄ Mesons

4. 1. PANDA Experiment
PANDA (antiProton Annihilation at Darmstdat) Detector
Full angular acceptance and angular resolution
Particle Identification (p,π,K, e, μ) in the range up to ~ 8 GeV/c
High momentum resolution
Target spectrometer
Forward spectrometer

5. 2. Straw Tube Tracker STT layout FST 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: ±5̊ vertically, ±10̊ horizontally

6. 2. Straw Tube Tracker Straw tube structure Advantages of straws
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)

7. 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
Drift velocity
Townsend
Pure Ar
Argon+ 30% CO2
10%
20%
20%
10%
50% 2% 1%
Ar+75% CO2
Pure Argon

8. 3. Straw Tube Simulation Gas gain simulation
Full penning transfer
Agreement with 34% penning rate
No penning transfer
The gain curve with 0%, 20%, 30%, 40%, 60% and 100% Penning rate
Comparison the measured gain with Diethorn’s formula

9. 4. Straw Front-end Electronic
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

10. 4. Straw Front-end Electronic
The ASIC test-board v. 2
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

11. 4. Straw Front-end Electronic
The transfer function
Transfer function produced by injection of “delta like” pulse to front-end
The 55Fe pulse convoluted by transfer function

12. 4. Straw Front-end Electronic
The high-rate test
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

13. 5. PID Methods TOT ? Q Energy loss: below 1 GeV PID based on dE/dx:
Straw Tube Tracker (STT)

14. 5. PID Methods TOT simulation
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
Straw
Tracks

15. 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 PID

16. 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

17. 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

18. 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

19. 6. Separation p-K-π
0.3 GeV/c
● proton
● kaon
● pion
0.7 GeV/c
● proton
● kaon
● pion
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

20. 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

21. 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 GeV/c
TOT works very well for PID in straw tube trackers

22. Thank you for your attention
Thank you for your attention
MESON2012 Conference, Krakow, Poland, 31May-5June 2012

23. 5. PID Methods TOT & Drift time simulation for cosmic rays
Tot vs. drift time for Muon 1GeV/c passing with 30 degree to wire
Drift time spectra for Muon 1GeV/c

24. 6. Position Resolution proton 1 GeV/c
threshold based on 20 primary electrons
threshold based on 10 primary electrons

25. 1. PANDA Experiment
PANDA (antiProton Annihilation at Darmstdat) Detector
Full angular acceptance and angular resolution
High momentum resolution
Particle Identification (p,π,K, e, μ) in the range up to ~ 8 GeV/c

26. 3. Straw Tube Simulation
Transverse diffusion
Longitudinal diffusion
Ar+10% CO2
15%
Ar+10% CO2
20%
15%
20%
50%
50%
Adding CO2 to Ar is efficient way to reduce the diffusion coefficient

27. 3. Straw Tube Simulation
attachment
Ionization rate
Ar+ 75% CO2
50%
20%
10%
CO2 as a quencher for the good drift properties and low ageing
Ar is a main component that dominantly ionized

28. 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