Fiberless Coupled Tiles for a High

Granularity Scintillator-SiPM

CalorimeterRick SalcidoRick SalcidoNorthern Illinois UniversityNorthern Illinois University

November 14, 2009November 14, 2009Prairie Section of the American Physical Society

Inaugural Meeting November 12-14, 2009

University of Iowa in Iowa City, IA

CALICE Prototype DetectorThe CALICE detector is an example of a highly

granular scintillator-based hadronic calorimeter

which uses Silicon Photo Multipliers as readouts

Event Display showing 32 GeV Muons in Fermilab test-beam.

The highly granular design allows viewing of single particle tracks. Important parts of a detector are

electromagnetic calorimeter (ECAL). Hadronic colorimeter

(HCAL) and a muon system, here called the “tail catcher – muon

tracker” (TCMT).

CALICE is an international collaboration aimed at designing calorimetry

detector for future colliders mainly the International Linear

Collider (ILC)

This prototype has the order of 10,000 channels, where

proposed calorimeters like the ILC or any future e+e-, µ+µ-, pp

bar, pe- require tens of millions of channels!

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Goals and Ideas Future Detectors in High Energy Physics

e+e-,µ+µ-, pp bar, or pe- colliders are the future

High Segmentation Hadron Calorimetry Improve jet energy resolution

Separate particles of similar mass

NIU R&D at Fermilab Exploring highly granular scintillator-based hadronic

calorimetry

Fiberless Coupling of scintillator to photo-detector

Surface Mounted Silicon Photomultiplier (SiPM) Technology

Integrated Readout Layer (IRL) – Cost Efficient Proof of Principal

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Scintillator Previous tile design

required wavelength shifting (WLS) fiber optic; technique used since the 80's with larger photo-multiplier tubes (PMTs)

New fiber-less tile design with concave dimple and surface mount SiPM

Concave dimple creates the uniform flat response

When a charged particle, such as a muon, passes through scintillating material, an electron in the material is promoted to a higher energy level and quickly falls back to its ground state emitting a photon of light. The photon eventually gets detected by the SiPM

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Silicon Photo Multiplier (SiPM)

Advantage in that SiPMs are insensitive to magnetic fields

High Voltage is “low” compared to dynodes of a photo-multiplier tube (PMT), Voltage range 30 – 70 V

SiPMs are small and naturally lend themselves to compact calorimeters

Detection Efficiency acceptance greater than PMT

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SiPM operation

Reverse bias applied

Active area: 1mm2 containing many avalanche photodiodes (APDs)

APDs amplify photocurrent

Applied reverse bias larger than breakdown -> E field large resulting in huge gain

Ionization – e-hole pair accelerated by high E field

Avalance Multiplication – carriers accelerated producing more carriers

Quenched Gieger Mode

Photo-electron spectrum using 2 calibration LEDs

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Dimpled Tiles Plots of various concavities

Compared with flat tile

9cm2, 5mm thick. 60% concavity optimal

3.375 mm concavity gives most uniform response

blue diamond – flat tileblue circle – 2.5 mm concavityorange triangle – 3.06 mm concavitylight blue square – 3.375 mm concavity

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2D Plots

Flat Cell Response

Dimpled Cell Response

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Building up...

Leading up to a large calorimeter, detection takes place not with one tile, but many

Tiles placed together to make larger mega-tile

Two holes required to mount on board

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Integrated Readout Layer (IRL) 64 SiPM slots

Each Channel has High and low gain option

8 calibration LED slots

Each SiPM coupled fiberlessly to individual scintillating tile

3 SiPMs tested on this board

Other boards and SiPMs under examination now

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Conclusion

Work Underway to prototype a highly granular, easily built scintillator-SiPM calorimeterSiPMs successfully fiberlessly coupled to scintillator cellsDimpled cells shown to have uniform response to radioactive sourcesPrototype IRL built and under evaluation; future beam tests and realistic calorimeter prototypes are planned

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References

“Directly Coupled Tiles as Elements of a Scintillator Calorimeter with MPPC Readout”

Nuclear Instruments and Methods in Physics Research Section A

Volume 605, Issue 3, 1 July 2009, pgs 277-281 http://www.nicadd.niu.edu/~psalcido/605.277.2009.pdf

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EXTRA SLIDES

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IRL Electronics

CRIM and CROC boards

CRIM connects 4 CROCS

CROC connects 4 IRL's

20 slot crate: 4 CRIM's 16 CROC's thus 64 IRL's 4096 channels

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SiPM and LED Locations

P - 51

P - 56P - 49

“A” LED“B” LED

25u MPPC

100u MPPC

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SiPM test with LEDs

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Response Measured

Flat portion of scintillating tile covered with VM2000 mirrored film

Sides of tile painted white for reflection properties

Concave portion of tile placed on Tyvek with opening for the SiPM

Strontium 90 (90Sr) used as beta source

Tile area scanned

Response is measured with SiPM

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SiPM Test

External LED and Pulser Photopeaks observed (2 – 100U and 1 – 25U) Pedestal peaks shown for reference

Onboard LEDs Procedure is tricky LED proximity to SiPM Scintillating Tile Crosstalk

SiPM testing done on a PCB called the “Integrated Readout Layer” (IRL)

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IRL Testing

Gatestart

LED Pulsewidth

SiPM Bias Voltage

Individual SiPM Biases

Measure SiPM Gain

Test LED responses

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SiPM Bias Voltage

0 10000 20000 30000 40000 500000

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20

30

40

50

60

70

80

Board 1 DAC to HV

Column F

Linear regression for Column F

DAC Value

Vo

ltag

e (

Vo

lts)

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Individual SiPM Bias

0 50 100 150 200 2500

0.5

1

1.5

2

2.5

3

3.5

4

4.5

Indivudual Voltage Board1 SiPM slot1

Adjusted DAC value

Bia

s V

olta

ge (V

olts

)

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Determining the SiPM Gain

Sepctrum of PE peaks

Low gain option

Red – pedestal (p1)

Blue – peak 2 (p2)

Green – peak 3 (p3)

p2 – p1 = p3 – p2 = gain