detector issues

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Detector Issues

H. Wieman

Feb. 7, 2002

STAR Collaboration Meeting

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Outline Detectors under consideration

» BNL Detector R&D Workshop Nov. 01 Some detector decisions

» TPC replacement?– Option for increased capability– Are there fundamental limits at 40X luminosity upgrade

Progress» Tests of micro pattern gas detectors» Active Pixel Sensor (APS) development

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Upgrade considerations

1. Build large TOF barrel (RPC ALICE/STAR R&D)

2. Install high precision inner vertex detector

3. Extend high quality forward tracking

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Upgrade considerations

5. Forward RICH, Yale 6. TPC replacement plus RICH -

Nikolai Smirnoff7. High speed FEE/RDO for current

TPC

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RHIC Detector WorkshopNov 13-14, 2001

Semiconductor Vertex Tracking Rene Bellwied, Wayne State U.Gas Tracking Detectors Itzhak Tserruya, Weitzmann Inst.Particle Identification Hideki Hamagaki, Univ. TokyoTrigger/Data Acquisition James Nagle, Columbia U.

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Detector Decisions

Present TPC vs Replacement» Can the present TPC work with the X40

luminosity upgrade» If TPC is replaced what are the trade offs,

what are the physics benefits

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Can the present TPC handle X40 luminosity

upgrade Space charge induced drift distortion?

» Observed DCA = 2.7 mm from Space Charge (Jamie Dunlop showed dependence on CTB scaler rate)

» Space Charge depends on beam current not interaction rate (charge comes from upstream background)

» Expect 12 mm with full 110 bunches x 109 ions» Jamie can correct 2.7 mm to 250 microns

– DCA RMS does not increase with scaler rate

Conclusion: Distortion Problem is probably not a show stopper

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Can the present TPC handle X40 luminosity

upgrade Wire aging?

» Depends on track multiplicity and gate open rate– This depends more on FEE/RDO rates than luminosity– 2kHz of central collisions – 4 years to reach limit of 0.1

Coul/cm on inner wires

Conclusion: Wire aging probably not a show stopper

Tracking problems from pileup?

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Present TPC vs replacement

Conclusion: Luminosity upgrade does not force a decision

Remains a question of physics priorities» Additional room for detectors with improved

particle ID vs expense and energy» What improvements are possible using present

TPC with new high rate FEE/RDO/DAQ and increased trigger capability?

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Smirnov Mini TPC

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Smirnov Mini TPC plus pad planes

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Detector replacement for TPC

Detector type A.

Silicon tracking + pads

B.

Silicon tracking

Methane TPC

RICH

pads

Channel count 12x105 8x105

dPt/Pt 4.1% 2.1%

Electron ID No Efficiency 70%

Contamination 0.3%

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Replacement TPC, Technical issues

Is pure silicon better – probably too expensive and gives poorer low momentum resolution

The outer pad chambers – how many needed for adequate tracking and how expensive

Drift gas CF4 vs CH4

Micro pattern readout – robustness with heavily ionizing tracks

Development needs and an early R&D progress report next>>

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Experimental set-up

I.Giomataris,G.Smith,B.Yu

Micro-pattern gas chamberreadout for TPC

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Micro-photograph of Micromegas

50 m tall Kapton pillar

50 m

5 m copper, 25 m diameter holes, 50 m pitch

Pillar spacing normally 1mm

( 2mm on test sample)


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Anode plane: Al strips with pitch 0.95 mm

Center 12 strips bussed together, to preamplifier. Load 150 pF.

Rest of strips grounded for present measurements.

152 mm

152 mm

Active area of micromegas mesh

Section used for measurements

(12 mm wide by 70mm)


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Measurement instrumentation

Collimator (25 m, 100 m, 1 mm)

Monochromator

Energized X-ray source

Detector


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300 350 400 450 500

Micromegas Voltage (-V)

0.001

0.01

0.1

1C

ha

rge

(p

C)

100

1000

10000

Ga

in

Micromegas Mesh, 50 µm spacing, Ar/20%CO2

VW

= -2000 V, 55Fe

Electrical Instability

Charge and Gain vs HTI.Giomataris,G.Smith,B.Yu

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+ve ion transmissionI.Giomataris,G.Smith,B.Yu

Must check if this is an issue for a small TPC

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Comments

• Micromegas mesh tested in Ar/20%CO2 and pure CF4

• Gas gain ~ 7,000 achieved in Ar/20%CO2 and ~ 300 in CF4

• 2mm post spacing may limit upper voltage, and hence gain, with CF4

• Resn of 16% and 27% FWHM in Ar/20%CO2 and pure CF4 at 5.4 keV

• Positive ion feedthrough ~ 1% with ED = 200 V cm-1

• Collimated beam cyclic gain change (~ 3%) across mesh holes

• Tests continue: Ar/10%CH4, Ar/20%DME, ~ 10ns shaping, ion drift velocity, local gain variation, lateral diffusion….


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GEM DetectorCourtesy of F. Sauli (CERN)

Additional GEM foils will be used to construct readout detector for TPC Drift Cell

N. Smirnov/ C. Woody

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GEM TPCGEM1

S1 S2 S3 S4

GEM2

GEM3

200 µm

DRIFT

Fast signals (no ion tail) T~20 ns :

Narrow pad response function (s ~ 1 mm):

Intrinsic multi-track resolution V ~ 1 mm3

(Standard MWPC TPC ~ 1 cm3)

Improved multi-track resolution

F.Sauli (CERN)

N. Smirnov/ C. Woody

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TPC Readout Plane and Electonics

Readout PadsDR ~ 1 cm f ~ 2 mm

Segmentation driven largely by resolution

P.O’Connor& Bo Yu (BNL)

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Absorbance: CF4

-0.03

-0.01

0.01

0.03

0.05

0.07

0.09

0.11

0.13

0.15

1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000

Wavelength [m x E-10]

Ab

sorb

ance

VUV Spectrometer

Measures optical transmission down to 120 nm

Bob Azmoun and Craig Woody

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TOF Barrel RPC plate technology (50 ps), different then

current installed systems that have problems Rice/ALICE

» Bill Llope, Jose Lamas-Velverde (thesis), Geary Eppley

ALICE Beam testing at BNL Test slat in STAR Outstanding issues – a TDC?

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Strawman / Potential layouts

Strawman technology = Silicon Strip double-sided Silicon Strip detector, 100 micron pitch 5 by 5 cm active area, 1000 channels/wafer 300+320 wafers (see layout below) 0.8 and 0.75 m2 of active Silicon, respectively

potential location:in front of FTPC 5 layers (z=60,80,100,120,140 cm ; r=10,15,20,25,30 cm) = 2.3-4.0 (320,000 channels)

potential location: behind FTPC 5 layers (z=350,375,400,425,450 cm ; r=20 cm all planes) = 3.5-5.0 (300,000 channels)

Bellwied, November 2000Bellwied, November 2000

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Potential Layouts two ‘stations’ in front and behind the FTPC

develop a quasi-circle use single-sided Si have FEE on disk edges use TAB Technology ?

Bellwied, June 2001Bellwied, June 2001

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RICH Detectors

Continuation of STAR RICH program» Located forward or» If TPC removed then in the cylinder

Gerd Kunde, Nikolai Smirnoff, Jamie Dunlop, Brian Lasiuk of Yale

Possible Yale development of CsI photo cathode production

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RICH Development, Yale

Investigation of CVD Diamond replacement for Cs-I by Brian Lasiuk

Hamamatsu R7639

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Faster TPC readout

Tonko next talk Interest by Tonko, Fred and Hank Low impact solution to high luminosity

operation

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8 cm

5.6 cm

Active Pixel Sensor (APS)

20 m square pixels

5 chips per slat

90 million pixels

40 m thick chips

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MEMOSA APS

A’B’

AB

A-A’

B-B’

e-

A Monolithic Active Pixel Sensor for Charged Particle Tracking and Imaging using Standard VLSI CMOS TechnologyJ.D. Berst, B. Casadei, G.Claus, C.Colledani, W.Dulinski, Y.Hu, D.Husson, J.P.Le Normand, R.Turchetta and J.L.RiesterLEPSI, IN2P3/ULP, Strasbourg, FranceG.Deptuch1, S.Higueret, M.WinterIReS, IN2P3/ULP, Strasbourg, France1vistitor from UMM, Cracow, Poland

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First chip – tested and works

128X128 pixels0.25 m CMOSTSMC through MOSIS

n well collection nodes

4 styles

column selection shift register

row selection shift register

S. Kleinfelder

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SK chip design

4 pixel styles Added FET acts as

» Sample and hold (off or on) or

» Capacitance isolator (TX held constant at intermediate voltage)

Copy of MIMOSA style

capacitance isolator

Cd Cg

Cd

Cg

Vsg drops to Vthreshold and any additional charge spills to drain (Cg).Only Cg is reset

Vsg

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LBL APS test with 1.5 GeV/c e-beam

SE 10 NE 10

17 e RMS per pixel

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LBL APS measured MIP signalSums of 25 pixel regions centered on pixels with ADC 7

Same sums with empty frames

Background subtracted APS signal with Bichsel calculation for 8 m Si Conclusion, signal to noise

is good enough to get good efficiency without excessive false hits

The above analysis is with CDS and leakage current subtraction

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Summary

Present TPC will probably handle luminosity with new electronics

Forward tracking and inner vertex improve physics reach without disruption

Improved particle ID possible at mid rapidity with RICH, Aero gel etc. - but must replace TPC to free up real estate

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Leakage Current

Mean pixel current 0.9 fA or 5600 e/sec

Q leakage = 1 MIP in 70 ms

Negligible with cooling (preliminary), i.e. won’t need correction for zero suppress

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Extended PID with Aerogel

Aerogel together with TOF can extend the PID capability up to ~ 10 GeV/c

5 - 91 - 5 n=1.007Aerogel

17 -5 - 17 n=1.004RICH

0 - 50 - 2.5 ~100 ps

TOF

Kaon-Protonseparation

Pion-Kaon

separation

0 4 8

0 4 8

0 4 8 0 4 8

0 4 8

0 4 8

Y. Miake

detector issues

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