Study of some aspects of straw tube detectors S. Roy, R. P . Adak, - PowerPoint PPT Presentation

Study of some aspects of straw tube detectors S. Roy, R. P . Adak, S. Biswas, S. Chattopadhyay, S. Das, D. Ghosal, S. K. Ghosh, A. Mondal, D. Nag, D. Paul, S. K. Prasad, S. Raha, J. Saini Bose Institute, Kolkata INSTR17: Instrumentation for Colliding Beam Physics, 27 February - 3 March, 2017, BINP , Novosibirsk, Russia 1

Outline — CBM experiment @ FAIR — CBM Muon Chamber — GEM development — R&D of Straw tube — Summary and Outlook 2

Phase diagram of matter • Main aim of relativistic heavy ion collisions is to study the phase diagram of strongly interacting matter. • CBM @ FAIR, Darmstadt, Germany will explore the region at low temperature and moderate to high baryon densities. 3

The Compressed Baryonic Matter Experiment (CBM)@FAIR — Fixed target heavy-ion Diagnostic probes of the experiment high-density phase: — Energy range 2-45 GeV/u — Open charm, charmonia — Expected to begin 2021 — Low-mass vector mesons ◦ Rare probes ◦ High interaction rates CBM physics program: ◦ Selective triggers — Equation of state at — Multi strange hyperons moderate baryon density — Flow, fluctuations, — Deconfinement phase correlations transition — QCD critical endpoint — Chiral symmetry restoration 4

CBM experiment Dipole MuCh RPC PSD TRD Magnet (TOF) STS 5

CBM experiment : Muon set up TRD RPC PSD MuCh (TOF) Dipole Magnet STS 6

Muon detection system 7

All the GEM R&D has been carried out at VECC for CBM At Bose Institute, Kolkata an initiative has been taken for R&D of GEM detector (stability test) and Straw tube detector for the CBM Muon Chamber (MuCh) 8

Set-up at Bose Institute 9

Long term stability test — Long term stability test is done with Fe 55 source (100 mCi or 3.7 GBq) — Gas: Ar/CO 2 70/30 — Constant applied voltage to the divider: -4300 V — Anode current is measured with and without source continuously (using Keithley 6485 Pico-ammeter) — Temperature, pressure and relative humidity are measured continuously 10

Gain Vs. time i source The absolute gain of the detector is calculated from the formula: gain = r ⇥ n ⇥ e r is the rate of the X-ray, n is the number of primary electrons and e is the electronic charge. 11 is the number of primary electrons

Correlation plot — g = G/Ae BT/p — G(T/p) = Ae BT/p — G = measured gain — g = normalized gain — A & B fit parameter — Townsend coefficient α ∞ 1/ ρ ∞ T/p — ρ = mass density Ref. M.C. Altunbas et al., NIM A 515 (2003) 249–254. 12

dQ Normalized gain Vs. dA The gain is normalized by using the relation: gain normalized = gain measured Ae ( B T p ) 2016 JINST 11 T10001 doi:10.1088/1748-0221/11/10/T10001. [arXiv:1608.00562] 13

Straw tube detector — Straw tube is typically prepared from a kapton film, one side containing a conductive layer of 1000-3000 Å Al + 4 μ m carbon-loaded kapton and the other side containing a thermoplastic polyurethane layer of 3 μ m. — The thickness of the straw wall is around 60 μ m. — A straw tube detector is basically a gas filled single channel drift tube with a conductive inner layer as cathode and a wire stretched along the cylindrical axis as anode — When high voltage is applied between the wire and the tube an electric field is generated in the gas filled region. — The electric field separates electrons and positive ions produced by an incident charged particle along its trajectory through the gas volume. — The wire is kept at positive voltage and collects the electrons while the ions drift towards the cathode. By choosing thin wires, with a diameter of a few tens of μ m, the electric field strength near the wire is made high enough to create an avalanche of electrons. — Depending on the high voltage and the gas composition a gain of about 10 4 − 10 5 can be achieved 14

Straw tube for CBM 6 straws diameter 6 mm length 20 cm Detector courtesy: Late Prof. Vladimir Peshekhonov of JINR, Dubna 15

Signal from Straw tube The Fe 55 signal in the oscilloscope at1600 V (20 mV/Div, 50 ns/Div, 50 Ω load). 16

Block diagram Pre-Amp HV Straw tube Fe 55 TSCA Scalar TTL-NIM adopter For count rate measurement • Gas: Ar/CO 2 gas in 70/30 • Flow rate: 3 lt/hr • Conventional NIM electronics 17

Count rate vs. voltage for Fe 55 100 count rate (kHz) 90 Threshold to the SCA : 1 Volt 80 70 60 50 40 30 o t = 20-21 C 20 o t = 24-25 C o 10 t = 26-28 C 0 1100 1200 1300 1400 1500 1600 1700 1800 voltage (V) R. P . Adak, et. al. Proc. of the DAE-BRNS Symp. on Nucl. Phys. Vol. 61, (2016), 996-997. 18

Count rate vs. voltage for different sources count rate (Hz) 55 Fe 137 5 Cs 10 60 Co 22 Na 4 10 without source SCA threshold 1.5 V 3 10 2 10 10 1 -1 10 1000 1100 1200 1300 1400 1500 1600 1700 1800 voltage (V) 19

Test of signal attenuation 100 count rate (kHz) HV 1600 V HV 1700 V 90 HV 1750 V 80 70 60 50 40 0 200 400 600 800 1000 1200 1400 1600 1800 2000 cable length (cm) 20

Gain vs. voltage 2 10 ion charge per particle (pC) 10 1 1200 1300 1400 1500 1600 1700 1800 voltage (V) 21

Uniformity of count rate along the length of the straw 120 count rate (kHz) 100 80 60 40 20 0 0 2 4 6 8 10 12 14 16 18 20 position (cm) 22

Uniformity of gain along the length of the straw 50 ion charge per particle (pC) 45 40 35 30 25 20 15 10 5 0 0 2 4 6 8 10 12 14 16 18 20 position (cm) 23

Gain vs. rate 2 10 ion charge per particle (pC) 10 1 HV 1700 V; th: 3 V HV 1700 V; th: 2.7 V HV 1750 V; th: 2.7 V HV 1700 V; th: 4.5 V HV 1700 V; th: 1.5 V -1 10 0 2 4 6 8 10 12 count rate per unit area (kHz/cm sq) 24

Summary and outlook — Basic characteristic studies are performed for straw tube with Ar/CO 2 gas in 70/30 ratio using conventional NIM electronics. — Count rate, gain, signal attenuation, uniformity are studied — Dependence of rate on gain is observed — Use of the straw tube in CBM MuCh is under investigation. 25

Acknowledgements We would like to thank Late Prof. Vladimir Peshekhonov of JINR, Dubna for providing the straw tube prototype and Dr. Christian J. Schmidt of GSI Detector Laboratory for valuable discussions in the course of the study. 26

Workforce Thank you for your kind attention ! 27

Back-up slides 28

MUCH: Accumulated Charge H hits/cm 2 /event ~0.5 (first GEM Layer) R event rate [Hz] 10 7 P primary electrons/track ~30 G detector gas gain 10 3 N e =H × R × P × G (no. of electrons) 1.5 × 10 11 cm 2 /s Q y =N e × Q e × y (acc. charge/year) 0.75 C/cm 2 /y Q 10y acc. charge over exp. lifetime 7.5 C/cm 2 29

Hysteresis 30