MWPC prototyping and testing of STAR inner TPC upgrade

Shuai Wang, Shandong University

for the STAR collaboration

PANIC 2017,Beijing

September , 2017

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Outline

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1. Upgrade motivation of iTPC

2. Upgrade components of iTPC

3. iTPC MWPC prototyping

4. iTPC MWPC test with 55Fe X-ray

5. Summary and Outlook

Shuai Wang PANIC2017 3/09/2017

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RHIC Beam Energy Scan(BES)

RHIC-BES key objective

Mapping the features of the QCD phase diagram.

Physical mechanism

Heavy ion collisions allow to explore the QCD phase structure by varying the collision energy.

RHIC-BES program (I->II)

Goals

Turn-off of QGP signatures

Search for critical point

First order phase transition

Schedule

BES-I completed 2010~2014

BES-II in 2019~2020

It Need detailed study of the key region.

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Why to upgrade STAR iTPC

Inner TPC upgrade: Increase inner sector pad coverage from 20% to 100% Extend TPC acceptance from |η|<1 to |η|<1.5 Lower pT measured minimum limit from 125MeV/c to 60 MeV/c Improve the dE/dx resolution from 7.5% to 6.5% (|η|<1)

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STAR TPC geometry

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STAR-TPC,NIM A499(2003)659

Outer sector

Inner sector

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1. Pad coverage 20%->100%

2. Gain uniformity better than 10%

3. Detection efficiency >98%

Produce and replace all 24 inner sectors

• Increase readout channels

• Renew all three wire frames

• New electronics for inner sectors

iTPC MWPC upgrade content

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iTPC MWPC production procedure

PCB bonding Wire mounts installing Pining wire mounts

Mounting wires Epoxying wires Soldering wires

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Wire winding for MWPC

Anode wires: gold-plated tungsten wires 20um diameter, tension 0.5N accuracy requirement:±0.03N

Shield wires: gold-plated beryllium copper wires 75um diameter, tension 1.2N

Gated grid: gold-plated beryllium copper wires 75um diameter, tension 1.2N

Why wiretension is so important May influence the uniformity of the gain Prevent the wire vibration under high voltage

Three layers of wire for MWPC

Winding machine at SDU 8 Shuai Wang

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Wire tension measurement system

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When the length of wire L and linear density ρ are known, the wire tension can be calculated by the formula :T=4 ρ f2L2

By the fast Fourier analysis program FFT , the fundamental frequency f is extracted from the vibration signal

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Some test results of wire tension

Measurement uncertainty: <1% Meet the tension accuracy requirements 0.5±0.03N.

Anode wire tension test result

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Xu Wang,Fuwang Shen,Shuai Wang,Cunfeng Feng,Changyu Li,Peng Lu,Jim Thomas, Qinghua Xu,Chengguang Zhu NIM 859(2017),page 90-94. “Design and implementation of wire tension measurement system for MWPCs used in the STAR iTPC upgrade”

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Wire pitch and height control

Wire comb and pitch control Wire pitch and height control schematic diagram

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Testing system for iTPC at SDU

Temperature transmitter

Pressure transmitter

Cooling fan for FEEs and RDO boards

Amplifier + MCA

Temperature and pressure transmitter Amplifier + MCA Radioactive source 55Fe X-ray transmission window 100 um PCB with graphite coating

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55Fe spectrum of a single wire

• Anode voltage: 1120V • P10(Ar:CH4 = 9:1) • Gas pressure: +2mbar • Temperature: 27.3℃ • Amplifier: A225+A206 • MCA Data Total rate: ~2077 Gas gain: 2700 Energy resolution(FWHM):

~20%

Main Peak

Escape Peak

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Correcting temperature and pressure dependence

Measuring accuracy: ΔT= ± 0.05℃ ΔP= ± 0.05mbar Data for 180 hours

Measuring accuracy: ΔT= ± 0.05℃ ΔP= ± 0.05mbar Data for 180 hours

Wire number:98th Data collected in 10 days Gas gain versus : Gain=ec0+c1T/P

Correction set:T=25℃ P=1013mbar Gas gain variation: before correction=17.7%, after correction=4.8%

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Gain=ec0+c1T/P

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Gas gain uniformity

Scan time : last 1 day The gain are corrected to 25℃, and the pressure corrected to 2mbar above the standard atmospheric pressure. Gain variation:6%(Max-Min),1%(RMS)

After correction

Before correction

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Anode voltage scan

Measured gain under different anode voltage Gain Vs HV follow the exponential distribution The peak position ratio of main peak to escape peak decrease

from1.95 to 1.65 Temperature: 25.3℃-25.8℃

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iTPC mass production for STAR started in June 2017,and it is expected to be finished in August 2018 on schedule.

Winding machine, Wire tension measurement system,and the test system for iTPC has been set up. Wire tension and other technical parameters all meet the requirements.

The iTPC performance test with 55Fe for the first two sectors are completed. The uniformity met the requirement too.

Summary and Outlook

Shuai Wang

PANIC2017 3/09/2017

Thanks!