RHIC-STAR 飞行时间谱仪的进展

2005 June 28-30 Shanghai Eastern Forum 1

RHIC-STARRHIC-STAR 飞行时间谱仪飞行时间谱仪的进展的进展

CHEN, Hongfang, USTC for STAR-China


• Time of Flight Project in STAR• Introduction of Multi-gap Resistive Plate Chamber

(MRPC)• Prototype running in STAR• Preparation for mass production in China (at USTC

and Tsinghua)• Conclusion

OutlineOutline


Time of Flight Project in STARTime of Flight Project in STAR

80 年代初物理学家提议建立高能重离子装置产生和研究 QGP, 高温 QCD 物质。T.D.Lee 提议在 BNL 利用 ISABELLA 的隧道来建造 RHIC 。 1991 年在 BNL 开始建造。1999 年建成，环周长 3.8 公里。加速金核最大能量 100 GeV/Nu


STAR Detector (baseline)STAR Detector (baseline)

Large coverage >2, ~2

ZCal

Barrel EM Calorimeter

Endcap Calorimeter

Magnet

Coils

TPC Endcap & MWPC

ZCal

FTPCs

Vertex Position Detectors

Central Trigger

Barrel or TOF

Time Projection Chamber

Silicon Vertex Tracker


Specific Energy Loss in STAR TPCSpecific Energy Loss in STAR TPC

STAR p + p at 200 GeV data

d d t

p K K p

e e

With the STAR TPC

K identification: pT ~ 0.6 GeV/c

Proton identification: pT ~ 1.1 GeV/c

S/N for reconstruction: ~ 1/few 100

Multi-strange particles reconstruction efficiency: ~ 10- 4 --10-3

J. Ma, Yamamoto et al.


Upgrade Requirements

Keep (expand) the general STAR philosophy of large coverage

• High rate readout and DAQ • Micro vertex detector for enhanced heavy quark ID • Enhanced (higher momentum) PID barrel TOF• High rate tracking capability and improved momentum resolution (TPC replacement, GEM technology)


by R. Majka for STAR

Barrel Time of Flight using Multi-gap Resistive Plate Chambers

Goal: Cover entire outer barrel of TPC with affordable, high resolution TOF (0<Φ<2π, -1<η<1,t<100ps)

Limits For PID2σ PID TPC dE/dx TOF (η~0) TOF (η~1)π/K/P ~0.7 GeV/c ~1.6 GeV/c ~2.0 GeV/c (π+K)/p ~1.0 GeV/c ~2.6 GeV/c ~3.2 GeV/c d ~1.0 GeV/c ~4.0 GeV/c ~4.7 GeV/c

With TOF, over 95% of the particles in the TPCacceptance will be Identified


Good time resolution (<100ps), high detection efficiency(>95%),high granularity, robustious, low cost.

Active area : 20 ×6cm, Readout Pad ： 3.15cm×6.1cm, gap ： 6×0.22mmGas ： 95% C2H2F4 + 5% Iso-C4H10

Beam test result

多气隙电阻板室（ MRPC ）是在 95 年以后发展的一种新探测器，利用 MRPC 技术制作桶部 STAR － TOF 探测器是一个好的方案。在 STAR 上采用 MRPC 技术建成 TOF 系统，将是国际上首先应用此技术的 TOF 。 TOF的运行将大大改进和扩展 STAR 的粒子识别能力，增强物理潜力。这是一项有高技术含量的硬件建设工作。

Introduction to STAR-TOFr, MRPCIntroduction to STAR-TOFr, MRPC


STAR TOF Team:(2002)STAR TOF Team:(2002)

16 institutions16 institutions

US US

Electronics, tray assembly and Electronics, tray assembly and integrationintegration

China (6 institutions)China (6 institutions)

Module construction and QAModule construction and QA


STAR-TOFSTAR-TOF

Width of Tray ～ 22cm

MRPC/Tray 32

Pad/MRPC 6

Capability in 82%

Total Trays 120

Total MRPCs ～ 4000

Total Pads ～ 24000

• MRPC modules to cover outer barrel of STAR TPC t < 100 ps

• Large coverage – < <, -1< <1, R≈2.1 m

• More than double momentum range of PID

• 3840 modules with 23,000 readout channels

• Fast detector – maintains (improves)

trigger capability


The specific technical goals of this project included the following:• Install and integrate a MRPC-based TOF system in a collider experiment for the first time.• Operate the system in a quasi-steady state over the entire run to gain experience on the reliability of the system and possible aging effects.• Collect enough data in specific configurations

to make statistically significant evaluations of the timing and PID performance of the system (based on the choice of the gas mixture, detector operating voltage, temperature effect,• Test new electronic.

TOF Tray Prototype Run in STAR(Run3, Run 4, Run5)


TOFr Tray 的结构

241*21.6*8.9cm3

=6° for one tray

Run 3--2002: 24 modules from USTC+4 modules from RICE; Run 4--2003: 2 modules from Tsinghua +22 modules from USTC; new mechanic frame Run 5--2004: 12 modules from Tsinghua +20 modules from USTC; new electronic


TOF Tray in STAR

Run 3


Instantaneous Radiation Hard

TOF running stable and reliable


Summary of TOF calibration

Time Resolution

(ps)

200GeV d-AU

200GeVpp

62 GeVAu-Au

200GeVAu-Au

200GeVAu-Au

Half Field

TOF 120 160 105 86 82

pVPD 85 140 55 27 20

MRPC 85 80 89 82 80

pVPDMRPCTOF

MRPC (include the contribution from electronics and intrinsic detector jitter)

K) :1.6GeV/c, (p/ ,K): 3GeV/c

Run 3 RUN 4


Time resolution (200GeV CuCu)

104 ps for 200GeV CuCu data from fit.~ 51 ps from pVPD. 90ps (85ps for run4)

ns

From Liu Jing-- Run 5 calibration, Preliminary

New electronics


TOFr response efficiency vs particle transverse momentum

Response efficiency is around 95% after the material absorption correction


PID capability demonstrated

TOFr combined with TPC

Electron identification: TOFr |1/ß-1| < 0.03 TPC dE/dx electrons!!!

electrons

ToFr+TPC, pT ~ 3 GeV/c ，

Extend hadron’s PID to higher momentumPreliminary spectra of ,K and p up to pT=5GeV/c are acquired in 62GeV Au+Au collisions


• HV was on for the entire run – no failures

• Noise rate ~300Hz from OR of 72 chan.

• TPC track matching done (software developed)

• Calibrations (t-zero, slewing, TDC nonlinearity, …) are all performed

• Gain running experience with Au-Au collisions

• < 85 ps MRPC timing resolution, 95% efficiency demonstrated

• PID capability demonstrated (software developed)

• Electron tagging demonstrated

• Physics publicationPhysics publication

• Ready for mass production when the fund ready Ready for mass production when the fund ready

What we learn from TOFr Tray running


Preparation for mass production (USTC and Tsinghua)


New laboratory at USTC


Tools developed by Tsinghua University


MRPC workshop>200m2

at Tsinghua

Outer scene of the workshop Assemble room


ConclusionConclusion

• MRPC TOF technology has operated successfully in

the RHIC/STAR environment

• PID capability demonstrated, including e-tag

• Physics capability demonstrated – publications

1 PRL; 2 PLB; 4 J.Phys.G;

paper for Detector R&D >20 (since 2001)

(STAR- 中国组：团结，齐心，配合。建立国内基地，华籍物理学家支持)

• Construction proposal submitted

• Ready for mass production


ThanksThanks

谢谢谢谢


E. Gorini et al. Nucl. Instr. Meth. A 396(1997)93

Uniform High Electric Field ~11kV/mm high drift velocity ~220m/ns high Townsend coefficient.Operate in Avalanche modeGas: Freon (electron affinity ) iso-butane (UV photon absorption) SF6 (streamer suppressing) heavy gas: 9-10clusters/mm for MIPSmall gap: 0.2-0.3 mmMulti-gaps: high efficiency

Introduction to STAR-TOFr, MRPCIntroduction to STAR-TOFr, MRPC

What is MRPC


Advantage of Join the international collaboration• Big Science must be international.• Get Chance directly work on the Frontier of Physics• More young Physicists get trained (challenge, competition)• 6 Chinese Ph.D thesis for Star physics (2002--)

Documents

RHIC-STAR 飞行时间谱仪 的进展

RHIC-STAR 飞行时间谱仪的进展