performance of the phenix ring imaging cherenkov detector takao sakaguchi, cns u. tokyo, for the...

Performance of the PHENIX Ring Imaging Cherenkov detector

Takao Sakaguchi, CNS U. Tokyo,

for the PHENIX Collaboration

CNS, U. Tokyo (H. Hamagaki, T. Matsumoto, S. Nishimura, K. Oyama, T. Sakaguchi)

Florida State U. (R. Chappell, D. Crook, A.D.Frawley, M. Kennedy)

KEK (Y. Akiba, K. Shigaki)

Nagasaki IAS (K. Ebisu, H. Hara, Y. Nagasaka, Y. Tanaka, T. Ushiroda)

ORNL (M.S.Emerry, C.G.Moscone, J.W.Walker, A.L.Wintenberg, G.R.Young)

SUNY at Stony Brook (R. Begay, J. Burward-Hoy, J.Ferriera, T.K.Hemmick, R.Hutter, S.Salomone)

U. Tokyo (R.S.Hayano)

Waseda U. (M.Hibino, S. Kametani, J. Kikuchi, M. Tamai)

The PHENIX RICH Team consists of 32 scientists from 8 institutions!

For Quark Matter 2001, Dec. 16, 2001

PHENIX Detector System

Search for Quark Gluon Plasma phase in Hot Dense Matter produced by 100 GeV/u Au+Au at BNL RHIC

(65 GeV/u Au+Au for Year-1)

Central ArmsCoverage (E&W) -0.35< y < 0.35 30o <||< 120o

A complex apparatus to measure: Hadrons, Muons, Electrons, Photons

Muon ArmsCoverage (N&S) -1.2< |y| <2.3 - < <

View From Beam

View From Top


PHENIX RICHCerenkov photons from e+ or e- are detected by array of PMTs

mirrorMost hadrons do not emit Cerenkov light

Electrons emit Cerenkov photonsin RICH.

Central Magnet

ＲＩＣＨ

PMT arrayPMT array

•Primary electron ID device of PHENIX

•Hadron rejection at 104 level for single track

•Full acceptance coverage for PHENIX central arms

•|y| < 0.35 ; = 90 degrees x 2

•Threshold gas Cherenkov•C2H6 (th ~ 25) or CO2( th ~ 35)•eID pt range : 0.2 ~ 4 GeV/c

•PMT array readout•5,120 channels in 2 arms•pixel size ~ 1 degree x 1 degree

•2-D angles (,) of electron tracks were determined from center of Cerenkov ring, and associated with the tracks reconstructed by Drift Chamber(DC)+Pad Chamber(PC)+Time Expansion Chamber(TEC)


Gas VesselTwo RICH detectorsone for each arm - Weight: 7250 kg / arm - Gas volume: 40 m3 / arm - Radiator length: 0.9 - 1.5 m - Mirror system Radius : 403 cm Surface area: 20 m2 / arm - Photon detector: 2560 PMTs / arm - Radiation length Gas: 0.41 % (ethane) Windows: 0.2% Mirror panels: 0.53% Mirror support: 1.0% Total: 2.14%

The vessels are designed and fabricated at Florida State University.


RICH PMTHamamatsu H3171S

Cathode Diameter: 25 mmTube Diameter: 29 mmCathode: BialkaliGain: > 107

Operation Voltage: - 1400 ~ -1800 VDark current: < 100 nA at Gain=107

Cathode Luminous: >70 (mA/lm)Blue Sensitivity: > 9(mA/lm)Quantum efficiency: >19% at 300 nm

>5 % at 200 nmRise Time: < 2.5nsTransit Time Spread: < 750ps

Total number of PMTs in RICH: 5120• Each PMT is housed in a magnetic shielding case

– First 900 PMTs

• Soft iron and mu-metal

– Other 4220 PMTs:

• FERROPERM (NKK)

• A Winstone cone shaped conical mirror is attached to each PMT to collect Cherenkov light

– Entrance: 50 mm, Exit: 25 mm, Angular cut off: 30

Magnetic Shielding Case design


RICH PMT array•Supermodule are installed in RICH vessel to form a tightly packed PMT array•40 super-modules per one side of a RICH vessel, forming a 16x80 array•Two arrays per RICH vessel, 4 arrays in two arms. Total number of PMTs: 5120

Completed PMT array of the first RICH detector. There is an identical PMT array in the opposite side of the RICH

• 32 PMTs are assembled into 2x16 sub-assembly called “super module”

• PMTs are grouped by its gain so that 8 tubes can share the same HV

• Supermodules are assembled and tested at Stony Brook, and sent to BNL

• At BNL, Winston cones are installed in PMTs, and the completed supermodules are installed in the RICH vessel

Super Modules?


RICH MirrorSegmented spherical mirror

Radius: 403 cm 48 panels / arm 2 (side) x 2 (z) x 12 ()

Reflection surface Aluminum Total area: 20 m2 / area

Mirror mounts are adjusted so that all optical targets are within 0.25 mm of the designed sperical surface.

graphite fiber epoxy only 0.53 % of radiation leng

thMirror support structure

graphite fiber, Delrin, 1 % of radiation length (ave.)

Rohacell foam core (1.25 cm thick)

Gel-coat (0.05 mm thick)

4 ply graphite-epoxy (0.7 mm thick)

Structure of the mirror

• Mirror panels are mounted by adjustable 3 point mounts on the frame bars

• 2 x 12 miror panels forms a spherical surface for one side of a RICH vessel

• 2 spherical surfaces in a vessel, total of 48 panels

Completed mirror array of the first RICH

Design of 3 points mirror mounts


RICH (mirror alignment)

After mirrors are installed, the RICH vessel is rotated up in the same orientation as on PHENIX carriage

Positions of optical targets placed on mirror surface were surveyed with a computerized theodolite system (MANCAT).

BNL survey crew were measuring the optical targets on the mirror during the mirror alignment.

RICH (after mirror alignment)


• Readout Signals from 5120 PMTs:

Zero10 Photon Detection 0 pC 160 pC (Signal Preceded by Pre-Amp(x10) )

Time Resolution of 200 ps (For Background Rejection)

• Very Fast Operation: 9.6 MHz RHIC Beam Clock: Average Trigger Frequency 25 KHz

• Transfer to Data Collection Module (DCM) Data Link using G-LINK

• Compactness Processes 640 PMT Signals per Crate

Conceptual Design of RICH FEE• 9U VME Dimensions• One Controller Module • Two Trigger Modules and Readout Modules• Ten AMU/ADC Modules

Front End Electronics (FEE)

RICH-FEE Crate !


Readout ModuleController Module• Management of Analog Memory Unit (AMU)• Controls FEE synchronous to Master Timing System• Controls Burst Transfer• Generate AMU Write / TAC Stop Timing• Slow Serial Control using ARCNET

DSU/ALM

BTSK2

Readout FIFO

G-LinkTransmitter

ROC

PhaseShifter

• Transferring Data to PHENIX-DCM usingG-LINK at the maximum speed of 800 Mbps• G-LINK Transfer asynchronous to BUS Transfer inside RICH-FEE using four FIFOs (Depth: 9 events)

Analog Processing (AMU/ADC) Module

Inte

grat

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TA

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RIC

H)

Chi

p

AM

U/A

DC

Chi

p

AM

U/A

DC

Bur

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ontr

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• 64 Inputs, 64 Charge and TAC(Timing) Outputs/Board• Trigger Sum: 16 Trigger Sum Outputs/Board (4 PMT Signal Sum)• Burst Transfer to Readout Module in 20-40MHz• Serial Controllable ASICs on Board

• 8 RICH Chips (Integrator+VGA+LED+CFD+TAC+Trigger Sum)• 8 Inputs, 8 CHARGE and TAC outputs/Chip, and 4 TriggerSum/Chip

• 4 AMU/ADC Chips (Random Accessible Analog Memory Unit and ADC)

• 32 Inputs/Chip


RICH in Operation! (RHIC Year-1 RUN)

•High PT electron candidate is seen!

•Candidate selected with RICH, DC, and Electromagnetic Calorimeter (EMCal).


PHENIX RUN 12280 SEQ 0014 EVENT 850

View from North Side

South Side

East Arm West Arm

RICH EMCal

RICH ring(6 PMT hit)

EMCal hit(2.5GeV)

6 PMT RICH ring2.55 GeV/c track2.5 GeV EMCal hitelectron candidate

EMCal

RICHPC1

DC

EMCal

RICHPC1

DC

TOF

TECPC3

RICH in Operation! (Cont’d)

4480 of 5120 (7/8) PMT signals are readout.

Rests are not readout because of short of electronics

Only 52 dead channels

Used CO2 as a Radiator gas

Momentum acceptance down to 100 MeV/c is achieved

Provide very good e/ separation

RICH sees electrons in its geometrical acceptance

Red: e-, Blue: e+


RICH Hit and Multiplicity

•Number of PMTs fired has good correlation with number of PC1 hits which is corresponding to Multiplicity

•Occupancy at most central: 3.4 % (Magnetic field ON)

Num

ber

of P

MT

hit

s

Number of PC1 hits


Electrons seen in Ratio of Energy and MomentumRatio of energy (E) and momentum (p) of associated track

Momentum and energy are measured with DC and EMCal, respectively

Condition required PMT hits of more than two in t

he ring of 3.4cm<r<8.4cm Good ring shape

Peak is seen at E/p=1, which corresponds to electrons

Good separation of electrons is seen


Green: Raw spectra Black: Cherenkov hit required Blue: Estimated background Red: Background subtracted

0.3GeV<p<0.4GeV 0.6GeV<p<0.7GeV

0.8GeV<p<0.9GeV 1.1GeV<p<1.2GeV

Charge Calibration with Real DataFit pedestal for each RUN

Count events above pedestal

Exceed 5000?Accumulate more RUNs

Fit single photo-electron (P.E.)

Predict mean and sigma of double and triple P.E.

Fit double and triple P.E.

Using derived fit parameters,re-fit all P.E.s again

Substitute pedestal-fit only RUNs with P.E.-fitted parameters

NO

YES

1.p.e. peak resolution: = 0.42 p.e.

After Calibration


Timing Calibration with Real Data

•See the Timing data for identified Electron Hit.

•Correlate it with Beam Beam Counter (BBC) timing

•Determine Time 0 (T0) and conversion factor of RICH timing Data

•Recheck if (RICH T0 – BBC T0) are flat over entire BBC timing range

= 0.98 nsec

Correlation of RICH T0 and BBC T0Correlation of (RICH T0 - BBC T0)and BBC T0

Correction


Photo-electrons seen in RICH

•Number of PMT hits, number of photo-electrons are in agreement with simulation study

•e+ e- identified with Time of Flight (TOF) in the momentum range from 0.3GeV to 0.4GeV

•Overall figure of merit (N0) is estimated: N0=Npe/L/ <sinc> =119 cm-1

Npe: number of photo-electrons per ring L: path length in RICH vessel <sinc>: mean cherenkov cone half-angle

Black: Raw spectrum Blue: Background estimated Red: Background subtracted

Number of PMTs per ring (r<11cm) Number of photoelectrons per ring (r<11cm)

Number of photoelectrons divided bypath length in RICH vessel (r<11cm)

Mean=0.9798


RICH Ring Associated with Track•RICH ring associated with DC+PC1+EMCal reconstructed track

•Final mirror alignment check is done with no field data in offline

•Main hits of PMTs are seen in about 3cm<r<11cm

•Low multiplicity events (PC1 hits<100) are selected

•More than four PMT hits in r<11cm are required

• Ring center deviation with reference to track:

=0.5, z=3.3cm

Good association is seen with track!


Rejection Power of RICH (CO2 Gas)Real Data

e+ e- and + - identified with TOF in the momentum range from 0.3GeV to 0.4GeV

Efficiencies for electrons are 10% lower in this momentum range compared to those in the momentum range of simulation

Number of PMTs are taken within ring of 3.4cm<r<8.4cm

Ring shape cut is applied Timing cut is not applied (lose factor of two) Shielding for conversion electron at DC is

not included (lose factor of two) Event class defined by PC1 hit: Peripheral: (PC1 hit)<150 Central: (PC1 hit)>400 Errors are statistical only

Simulation Momentum range from 0.6 to 0.8GeV Au+Au Central Various electron ID cut is applied Timing cut applied Shielding included

Black: Simulation for Au+Au CentralBlue: Real data for Au+Au PeripheralRed: Real data for Au+Au Central


Rejection Power is good, and will be much better after planned improvement

Very Near Future PlanImprove Rejection Power

Shielding against conversion electron produced in the massive material at the edge of DC Establish Timing Cut

Develop trigger board to associate with EMCal hits in online.

Reaction rates at blue book luminosities

200 A GeV Au+Au: 1.2 kHz200 GeV p+p: 400 kHz

(4 MHz later)500 GeV p+p: 1.2 MHz(12 MHz later)

• DAQ capability: level-1 limit : 25 kHz (6 kHz initially)

required level-1 rejection power order of 102 ~ 103 for heavy ion physics

Access to rare probesJ(di-electron)charm (single electron)

Simulated Trigger RejectionPower for Au+Au

Trigger Scheme

RICHTriggerBoard


Summary• RICH has succeeded to operate in the RHIC Year-1 RUN.

• High PT electrons are successfully identified.

• 7/8 of all PMTs (5120PMTs) have been readout with very few dead channels.

• Charge and timing calibration procedure using online data are established, and confirmed they work well.

• Following performances are derived. Timing resolution: ~ 1 nsec

Charge resolution: = ~ 1/2 p.e. for single photo-electron

Overall figure of merit N0: 119 cm-1

Occupancy at most central: 3.4 % (Magnetic field on)

Ring center deviation with reference to track: =0.5, z=3.3cm

Rejection power at electron efficiency of 82%: 280 for Peripheral, 85 for Central (Without shielding for conversion electron and timing cut. Ring shape cut applied)

• Conversion electron shielding, timing cut will be applied for Year-2 RUN.

• RICH trigger board is developed and will be installed.


performance of the phenix ring imaging cherenkov detector takao sakaguchi, cns u. tokyo, for the...

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