1. MWPC prototyping and testing of STAR inner TPC upgrade
Shuai Wang,
Shandong University
for the STAR collaboration p
PANIC 2017,Beijing
September , 2017
PANIC /09/2017

2. Upgrade motivation of iTPC Upgrade components of iTPC
Outline
Upgrade motivation of iTPC
Upgrade components of iTPC
iTPC MWPC prototyping
iTPC MWPC test with 55Fe X-ray
Summary and Outlook
PANIC /09/2017
Shuai Wang

3. 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.
PANIC /09/2017
Shuai Wang

4. 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)
PANIC /09/2017
Shuai Wang

5. STAR TPC geometry STAR-TPC,NIM A499(2003)659 Outer sector Inner sector
PANIC /09/2017
Shuai Wang

6. iTPC MWPC upgrade content
Produce and replace all 24 inner sectors
Increase readout channels
Renew all three wire frames
New electronics for inner sectors
Pad coverage 20%->100%
Gain uniformity better than 10%
Detection efficiency >98%
PANIC /09/2017
Shuai Wang

7. iTPC MWPC production procedure
PCB bonding
Wire mounts installing
Pining wire mounts
Mounting wires
Epoxying wires
Soldering wires
PANIC /09/2017
Shuai Wang

8. Wire winding for MWPC Anode wires: Shield wires: Gated grid:
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:
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
PANIC /09/2017
Shuai Wang

9. Wire tension measurement system
By the fast Fourier analysis program FFT , the fundamental frequency f is extracted from the vibration signal
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
PANIC /09/2017
Shuai Wang

10. Anode wire tension test result
Some test results of wire tension
Anode wire tension test result
Xu Wang,Fuwang Shen,Shuai Wang,Cunfeng Feng,Changyu Li,Peng Lu,Jim Thomas,
Qinghua Xu,Chengguang Zhu
NIM 859(2017),page
“Design and implementation of wire tension measurement system for MWPCs used
in the STAR iTPC upgrade”
Measurement uncertainty: <1%
Meet the tension accuracy requirements 0.5±0.03N.
PANIC /09/2017
Shuai Wang

11. Wire pitch and height control
Wire comb and pitch control
Wire pitch and height control schematic diagram
PANIC /09/2017
Shuai Wang

12. Testing system for iTPC at SDU
Cooling fan for FEEs and RDO boards
Temperature transmitter
Pressure transmitter
Amplifier + MCA
Temperature and pressure transmitter
Amplifier + MCA
Radioactive source 55Fe
X-ray transmission window
100 um PCB with graphite coating
PANIC /09/2017
Shuai Wang

13. 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
PANIC /09/2017
Shuai Wang

14. Correcting temperature and pressure dependence
Gain=ec0+c1T/P
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%
Measuring accuracy:
ΔT= ± 0.05℃ ΔP= ± 0.05mbar
Data for 180 hours
Measuring accuracy: ΔT= ± 0.05℃ ΔP= ± 0.05mbar
Data for 180 hours
PANIC /09/2017
Shuai Wang

15. Gas gain uniformity Scan time : last 1 day
Before correction 8.6%
After correction 6%
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)
PANIC /09/2017
Shuai Wang

16. 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℃
PANIC /09/2017
Shuai Wang

17. Thanks! Summary and Outlook
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.
Thanks!
PANIC /09/2017
Shuai Wang