Fiberless Coupled Tiles for a High Granularity Scintillator-SiPM Calorimeter Rick Salcido Northern Illinois University November 14, 2009 Prairie Section of the American Physical Society Inaugural Meeting November 12-14, 2009 University of Iowa in Iowa City, IA

CALICE Prototype Detector The 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!

3 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

4 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

5 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

6 SiPM operation Reverse bias applied Active area: 1mm 2 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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8 Dimpled Tiles Plots of various concavities Compared with flat tile 9cm 2, 5mm thick. 60% concavity optimal mm concavity gives most uniform response blue diamond – flat tile blue circle – 2.5 mm concavity orange triangle – 3.06 mm concavity light blue square – mm concavity

9 2D Plots Flat Cell Response Dimpled Cell Response

10 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

11 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

12 Conclusion Work Underway to prototype a highly granular, easily built scintillator-SiPM calorimeter SiPMs successfully fiberlessly coupled to scintillator cells Dimpled cells shown to have uniform response to radioactive sources Prototype IRL built and under evaluation; future beam tests and realistic calorimeter prototypes are planned

13 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

14 EXTRA SLIDES

15 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

16 SiPM and LED Locations P - 51 P - 56P - 49 “A” LED “B” LED 25u MPPC 100u MPPC

17 SiPM test with LEDs

18 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 ( 90 Sr) used as beta source Tile area scanned Response is measured with SiPM

19 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)‏

20 IRL Testing Gatestart LED Pulsewidth SiPM Bias Voltage Individual SiPM Biases Measure SiPM Gain Test LED responses

21 SiPM Bias Voltage

22 Individual SiPM Bias

23 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