SCINTILLATOR / WLS FIBER OPTION FOR BABAR MUON DETECTOR UPGRADE

PETER KIM SLAC

HAWAII SUPER B FACTORY WORKSHOP JAN 19-22, 2004
BABAR BARELL RPC MUON SYSTEM DETERIORATING RAPIDLY WE NEED REPLACEMENT IN 2004/2005
BARELL RPC: Finely segmented 19 layers 5.1 Interaction length Without Layer 19 dies, we loose 10 cm of Fe --> 4.5 Interaction length. Fill 6 out of 18 Layers with 2.2 cm BRASS -> 5.2 Interaction Length Fill Remaining 12 Layers with ACTIVE DEVICE Must Fit in 2.2 cm Gap between Irons
THREE PROPOSALS WERE MADE in 2002
RPC LST (Limited Streamer Tube) SCINTILLATOR/WLS DETECTOR
SCINTILLATOR/WLS FIBER DETECTOR WITH AVALACHE PHOTODIODE READOUT S. Fan, G. Dubois-Felsmann, D. Hitlin, P. Kim M. Lometti, D. Nelson, R. Schindler, J. Stelzer, W. Wisniewski (SLAC & Caltech)
Utilize Existing Technology of Scintillator/WLS readout Very Fast Scintillator Signals: few ns Avalanche Photodiode Readout: All READOUT ELECTRONICS inside IRON NO Problem with 1.5 T Magnetic Field Modular Design Easily Installed & Replaceable Questions: APD Gain Much Lower than PMT Unknown Long Term Reliability of APD APD Cost Issue

MINOS MUON DETECTOR

MINOS: 300 Tons OF CHEAP CO-EXTRUDED SCINTILLATOR BARS (8m x 4cmx1cm) A SINGLE 1.2mm Y11-175 multiclad WLS FIBER (polystyr., pmma, Teflon)
LIGHIT COLLECTED VIA DIFFUSE SCATTERING INTO EMBEDDED WAVE LENGTH SHIFT (WLS) FIBERS WHERE att ~ 4m RATHER THAN TRANSPORT IN SCINTILLATOR ( where att ~ 20cm to 100cm) WLS FIBER LONG CLEAR FIBER PIXELATED PMT
3-4 pe/fiber at ~3.7 m INCL. FIBER CONENCTON & PMT QUANTUM EFF. DIFFICULT TO FIND SPACE OF PMTs in BABAR
A SEXTANT FULL OF RPC READY FOR INSTALLATION
MORE WLS FIBERS MEANS MORE LIGHT
(6) 4 FIBERS IN 5cm X 2cm AMCRYS EXTRUSION
FOR EACH CASE WE EVALUATED o RELATIVE LIGHT YIELD, o ATTENUATION LENGTH, o TIME (POSITION RESOLUTION) COMPARISON WITH MC PREDICTIONS (J. Stelzer and M. Lometti)
WLS FIBER CLADDING AND SHAPE

3.1% 3.1%

5.4% TRAPPING GOING SINGLE TO MULTICLAD 4.2% TRAPPING BY GOING FROM ROUND SQUARE (potentially additional gain of 25%)
SQUARE FIBERS IMPROVE GEOMETRICAL MATCH TO A SQUARE APD UNFORTUNATELY ONLY BICRON PROVIDES MULTICLAD SQR FIBER AND THE MATCHING OF ABSORBTION TO SCINT WAS FOUND TO BE POOR (NEEDS DEVELOPMENT)
WLS FIBER & SCINTILLATOR ABSORPTION MATCHING
Y11 Kuraray WLS FIBER 1.2 mm Round Fiber Double Cladding Excellent Attenuation Lengths > 3 m
QUANTUM EFFICIENCY OF READOUT DEVICE
QE OF PMT & 2mm x 2mm RMD APD COMPARED WITH WLS EMMISSION SPECTRUM BELOW:

XP2262B

WLS EMMISSION
QE OF XP2262B & MINOS M16 / 64

Quantum Eff. Of APD

60% 40% 20%
ABOUT A FACTOR OF 4X IN QUANTUM EFFICIENCY FOR APD OVER PMT AT ~520 nm

APD GAIN MEASUREMENT

RMDs PLANAR APD #S0223 (2x2mm2, 0.7pf/mm2) QE > 65% at >530 nm, ~5 NS RISETIME AT 500nm Gain >1000X, (00C), AT ~1750v Gain/V (G=1000,00C) = +5%(-2%) EMCO CA20P HV Power Supply (Ripple < 0.001%)
Scintillator/WLS Prototype
TWO 3.7m LONG FULL LENGTH STRIP PROTOTYPES (ITASCA, AMCRYS SCINTILLATOR) & CHARACTERIZE THEM USING PMT, THEN WITH APD TESTS ITASCA vrs AMCRYS EXTRUSIONS LIGHT YIELD POSITION RESOLUTION By TIMING POSITION RESOLUTION By PULSE HEIGHT DEVELOP PELTIER COOLING & OPTICAL CONNECTIONS TO APD TEST THERMAL, CONFORMAL, & OPTICAL EPOXY ASSEMBLE TE COOLER MODULE & TEST DETERMINES NOISE, GAIN vrs TEMPERATURE CHARACTERIZE FULL LENGTH PROTOTYPE WITH A COOLED APD READOUT

ITASCA EXTRUSION

MINI-CONNECTORS WITH DOWEL REGISTRATION LIKE MINOS

WITH 4 WLS FIBERS

3.7 METER LONG 2cm THICK BAR

BOTH SCINT. HAVE A MID-PT EPOXY JOINT MAY LOCALLY EFFECT TIMING RESOLUTION
RESULTS FROM TWO FULL LENGTH PROTOTYPE TESTS WITH PMT READOUT (BOTH ENDS):

EFFICIENCY:

REQ. EXT. TRIG. HODOSCP ~ 4cm RGN ALONG BAR REQ. PMT2 TO SEE >10 adc cts (~1 ) > PEDISTAL >1500 SAMPLES / POSITION
SINGLE SIDED EFFICIENCY OF FULL LENGTH BAR

ITASCA AMCRYS

LIGHT YIELD AND ATTENUATION LENGTH: REQ. EXTERNAL TRIGGER HODOSCOPE TO DEFINE ~ 4cm REGION ALONG BAR (COSMIC MUONS)
<ATTENUATION LENGTH >(ITASCA) <ATTENUATION LENGTH >(UKRAINIAN)

312 cm 259 cm

FITS SHOW NON-EXPONENTIAL BEHAVIOR BECAUSE OF WAVELENGTH DEPENDENCE AVERAGE LIGHT YIELD UKRAINIAN ~31% > ITASCA
TIMING MEASUREMENTS (PMT) OF FULL LENGTH BARS (AVERAGED OF BOTH ENDS) (Total Length + (Pos(PMT1) Pos(PMT2) ) * 0.5 Could improve with Weighted Average OBSERVE ~17cm/ns Propagation Velocity DIST. (cm) Pos. Resolution ITASCA (cm) 17.8 +/- 0.3 16.2 +/- 0.5 17.8 +/- 0.4 16.6 +/- 0.8 17.9 +/- 1.3 17.1 +/- 0.6 17.1 +/- 0.8 16.8 +/- 0.8 DIST. (cm) 388 Pos. Resolution AMCRYS (cm) 15.1 +/- 0.2 14.3 +/- 0.4 15.6 +/- 0.3 14.5 +/- 0.3 14.4 +/- 0.4

AMCRYS SCINTILLATOR

XP2262B PMT and Photo Electron Calibration
700 ADC cts/MIN ION at 42cm PMT QE~14% at 520 nm IMPLIES ~500 PRIMARY PHOTONS FROM THE 4 FIBERS REACH PMT With APD QE of 60%, we expect 240 pe at 42 cm. > 60 pe at 370 cm
NOISE IN APDS & COOLING 4 PRIMARY SOURCES OF NOISE & PEAK BROADENING IN
PLANAR (NON-BEVELED EDGE) APDS:
USUAL ELECTRONICS NOISE FROM C & R AT INPUT OF FET (measure at ~50v when fully depleted) FLUXUATIONS IN AMPLIFICATION OF DARK CURRENT (BULK) IN APD DEPEND ON STATISTICAL NATURE OF THE IMPACT IONIZATION PROCESS FLUXUATIONS IN EDGE CURRENT (NOT AMPLIFIED) FLUCTUATIONS IN SIGNAL AMPLIFICATION WHICH DEPEND ON STATISTICAL NATURE OF THE IMPACT IONIZATION PROCESS
COOLING THE APD HAS THREE EFFECTS:
REDUCES BULK LEAKAGE CURRENT (halves @ -100C)
REDUCES AMPLIFIED NOISE CONTRIBUTION
INCREASES IMPACT IONIZATION PROBABILITY OF CARRIERS (both and increase as T decreases)
GAIN INCREASES AT FIXED VOLTAGE
REDUCES EXCESS NOISE FACTOR (F) ( > for a decrease in T)
FROM RMD STUDY. DETECTION EFFICIENCY AT

FIXED DISCR. THRESHOLD

NUMBER OF PRIMARY PHOTELECTRONS
DATA FROM RMD SUGGESTED THAT BY COOLING APD TO ~00C, THE DETECTION EFFICIENCY FOR MIN ION WILL BE ~100% EVERYWHERE.

SIGNAL TO NOISE TARGET

pe /APD (Worst Case of 3.7 m Distance) APD Gain of 1000x 60,000 electrons A250F Charge Sensitive Amplifier Integration Time ~ 100 ns Gain : 4 mV / fc Amplifier Noise: ~220 e (APD + Stray capacitance = 10 pf) Worst Case Signal: ~40 mV Masured Noise ~ 1-2 mV RMS at 1.85 kV
PELTIER COOLING & OPTICAL CONNECTS TO APD
30W THERMO-ELECTRIC COOLER TO BE USED INITIALLY 4W to 8 W SMALLER ONES 15 x 15 mm FOR ACTUAL USE IN IFR
APD COOLER, MACOR APD HOLDER, HEAT SINK & FIBER OPTIC CONNECTOR BEFORE EPOXYING (FRONT VIEW)
DATA USING COOLED APD ON FULL LENGTH BAR: APD Cooled to 0-Deg C. HV = 1765 V Defining Counters positioned at 380 cm from APD Preamp Output Amplified x20 (To fit ADC range) Top: All Signals with No Threshold Cut Middle: < 60 mV Threshold Cut Bottom: > 60 mV Threshold Cut MIN I Signal!
Signal Efficiency: > 98% with 60 mV Threshold Background Rate: < 1%
Example Scope Shot of PMT and APD Signals Top: PMT Signal Bottom: APD Signal
ADC COUNTS AT DIFFERENT DISTANCES Histogram: 380 cm Away from APD Dots: 75 cm Away from APD
TIMING RESOLUTION IS POOR
Sigma (Position) = 75 cm Due to SLOW RISE time of Preamp ~100 ns Work in Progress to modify Feedback Capacitor for AMPTEK 250F Preamp without loosing Sig/N ratio.

(MINOS DETECTOR) OR

Z Position Measurement can also be obtained with the Scintillator Bars at STEREO ANGLES
SCINTILLATOR TILES WITH WLS FIBER READOUT
STUDY OF FIBER & MODULE LAYOUT

FOUR FIBERS PER BAR

SIXTEEN SCINT. BARS, EACH 2 cm THICK
CONNECTOR TO 4x4 APD ARRAY & THERMO ELECTRIC COOLER, PREAMP& DISCR CARD
PIECES BUILT UP TO MAKE FIBER OPTIC CONNECTOR

PREAMPLIFIER CARD

BABAR HAS CHOSEN LIMITED STREAMER TUBES (LST) FOR MUON UPGRADE

R&D CONTINUES

STUDY OF 4 x 4 (16-pixel) APD ARRAYS
RMD GAVE US SUBSTRATES FOR PRACTICING & STUDYING THERMO-ELECTRIC ASSEMBLY 2mm x 2mm SINGLE PIXEL SUBSTRATE

16 PIXEL ARRAY SUBSTRATE

LONG TERM BURNIN TEST OF APD AT HIGH TEMP 15 4x4 ARRAYS OBATINED FROM RMD
POSSIBILITY OF REPLACING ENDCAP RPC IN HIGH BACKGROUND RADIATION REGION IN 2006

SUMMARY

SCINTILLATOR/WLS DETECTOR WELL SUITED FOR MUON DETECTION AT HIGH RATES (SIGNAL & BACKGROUND) NO PROBLEM WITH HIGH MAGNETIC FIELD (5 T in LC Detectors) GOOD SIGNAL/NOISE RATIO CAN BE OBTAINED WITH OPTIMIZATION OF BIAS VOLTAGE AND COOLING

64 PIXEL ARRAY