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Photodetection

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N. Dinu, T. Gys, C. Joram, S. Korpar, Y. Musienko, V. Puill, D. RenkerEDIT 2011 1

Photodetection Principles, Performance and Limitations

Nicoleta Dinu (LAL Orsay)Thierry Gys (CERN)Christian Joram (CERN)Samo Korpar (JSI Ljubljana)Yuri Musienko (Northwestern U, USA) Veronique Puill (LAL, Orsay)Dieter Renker (TU Munich)

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Photodetection

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OUTLINE

• Basics

• Requirements on photodetectors

• Photosensitive materials

• ‘Family tree’ of photodetectors

• Detector types

• Applications

Photodetection

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Basics

1. Photoelectric effect2. Solids, liquids, gaseous materials3. Internal vs. external photoeffect, electron affinity4. Photodetection as a multi-step process5. The human eye as a photodetector

Photodetection

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Formatting guidelines for preparing slides

Use Calibri as default fontDefault color: white (avoid text in red, difficult to read for many people)Main title: 24 ptsNormal text: 16 ptsReferences: 10 pts

Photodetection

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Photodetection

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Energy loss eVth in (thin) ohmic contact

Hybrid Photon Detectors (HPD’s) – Basic Principles

• Combination of vacuum photon detectors and solid-state technology;

• Input: collection lens, (active) optical window, photo-cathode;

• Gain: achieved in one step by energy dissipation of keV pe’s in solid-state detector anode; this results in low gain fluctuations;

• Output: direct electronic signal;• Encapsulation in the tube implies:• compatibility with high vacuum

technology (low outgassing, high T° bake-out cycles);

• internal (for speed and fine segmentation) or external connectivity to read-out electronics;

• heat dissipation issues;

DV

(C.A. Johansen et al., NIM A 326 (1993) 295-298)

Optical input window

n+

n

p+

- ++ -+

-

Photon

Photoelectron

Typical stopping range 3-5mm

Photodetection

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• Photo-emission from photo-cathode;• Photo-electron acceleration to DV 10-

20kV;• Energy dissipation through ionization and

phonons (WSi=3.6eV to generate 1 e-h pair in Si) with low fluctuations (Fano factorF 0.12 in Si);

• Gain M:

• Intrinsic gain fluctuations sM :

dominated by electronics• Example: DV = 20kV

M 5000 and sM 25• suited for single photon detection with

high resolution;

SiWVthVeM )( D

(C.P. Datema et al., NIM A 387 (1997) 100-103)

Background from electron back-scattering

at Si surface

MFM s

1 pe

2 pe 3 pe

4 pe

6 pe

7 pe

5 pe

Energy resolution of HPD’s - Basic Properties

Photodetection

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(http://cmsinfo.cern.ch/Welcome.html/CMSdetectorInfo/CMShcal.html)

(P. Cushman et al., NIM A 504 (2003) 502)

Possible cross-talks

(http://cmsinfo.cern.ch/Welcome.html/CMSdetectorInfo/CMShcal.html)

Multi-pixel proximity-focussed HPD – CMS HCAL

• B=4T proximity-focussing with 3.35mm gap and HV=10kV;

• Minimize cross-talks:– pe back-scattering: align with B;– capacitive: Al layer coating;– internal light reflections: a-Si:H AR

coating optimized @ l = 520nm (WLS fibres);

• Results in linear response over a large dynamic range from minimum ionizing particles (muons) up to 3 TeV hadron showers;

Photodetection

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Object illuminance: 0.1lx

EBCCDproximity-focussed

Commercial 2/3” CCD

Hamamatsu N7640EB-CCD

(Hamamatsu)

Electron-bombarded CCD (EBCCD)

extra slide

not shown

Photodetection

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• Industry-LHCb development:• LHCb-dedicated pixel array sensor bump-

bonded to binary electronic chip (in close collaboration with ALICE-ITS), specially-developed high T° bump-bonding;

• Flip-chip assembly encapsulated inside vacuum tube using full-custom ceramic carrier;

(M. Moritz et al., IEEE TNS Vol. 51,No. 3, June 2004, 1060-1066)

50mm

Pixel-HPD anode

72mm

(K. Wyllie et al., NIMA 530 (2004) 82-86)

Pixel-HPD’s for LHCb RICHes

(M. Campbell et al., IEEE TNS Vol. 53,No. 4, August 2006, 2296-2302)

Photodetection

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RICH2 H X-section

Upper RICH1 HPD plane

Pixel-HPD’s for LHCb RICHes

• Single photon sensitivity over 200nm-600nm (aerogel response and scattering, and chromatic dispersion in gases)

• Detection area of 3.3m2 (500 HPD’s) with active area fraction of ~65% and position resolution 2.5mm (optimum of pixel vs chromatic vs emission point errors)

• Fast response for LHC bunch-crossing rate of 40MHz with good signal-to-noise ratio

• Radiation tolerant (3krad per year)

LHCb data(preliminary)

K ring in RICH1

Photodetection

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• Non-exhaustive list:• www.photonis.com: “Photomultiplier tubes, principles and applications”;• www.hamamatsu.com;• www.photek.com;• A.H. Sommer, ”Photoemissive materials”, J. Wiley & Sons (1968);• H. Bruining, “Physics and Applications of Secondary Electron Emission”, Pergamon Press

(1954); • I. P. Csorba, “Image Tubes”, Sams (1985);• Proceedings of the triennial NDIP (New Developments in Photo-detection) Conference (1996-

2008), published in NIMA;

Literature

Photodetection

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Applications

1. Readout of scintillators / fibres with PMT/MAPMT. 2. Readout of RICH detectors with HPD. 3. Readout of RICH detector with gas based detectors4. Readout of inorganic crystals with APD. Example: CMS ECAL.5. Readout of scintillators with G-APD. 6. Ultrafast timing for TOF with MCP-PMT

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