Photon-Absorption Enhancement Factor

Work supported by National Nuclear Security Administration (NNSA), Office of Nonproliferation

Research and Engineering, DOE, and

two Advanced Detector Awards, Office of Science, DOE

Daniel Ferenc, Andrew Chang

Eckart Lorenz

Physics Department, University of California Davis, Max Planck Physics Department, University of California Davis, Max Planck Insitute, MunichInsitute, Munich

3 existingexistingmass-production

technologies

ENCLOSURE: FLAT-PANEL TV

ELECTRON DETECTION:SEMICONDUCTOR

Scintillator + Geiger-MODEAVALANCHE

DIODE‘Light Amplifier’

PHOTONELECTRONCONVERSION:

CLASSICALPHOTOCATHODE

3 existingexistingmass-production

technologies

ENCLOSURE: FLAT-PANEL TV

ELECTRON DETECTION:SEMICONDUCTOR

Scintillator + Geiger-MODEAVALANCHE

DIODE‘Light Amplifier’

PHOTONELECTRONCONVERSION:

CLASSICALPHOTOCATHODE

ALREADY VERY GOOD

MAJOR MODIFICATIONS

(will showtomorrow)

3 existingexistingmass-production

technologies

ENCLOSURE: FLAT-PANEL TV

ELECTRON DETECTION:SEMICONDUCTOR

Scintillator + Geiger-MODEAVALANCHE

DIODE‘Light Amplifier’

PHOTONELECTRONCONVERSION:

CLASSICALPHOTOCATHODE

ALREADY VERY GOOD

MAJOR MODIFICATIONS

(will showtomorrow)

LOOKIN FORWARD

FOR IMPROVEMENTS

DIAGNOSTIC TOOL – NOT USED (YET)

7-pixel 5-inch ReFerence Flat-Panel Prototype

UHV Transfer System :• Photocathode deposition• Indium/Au/Cr deposition

• Vacuum sealing

Lasers for

Active Mirror Control

SUPER-EFFICIENT CAMERA

PMT

Maximizing Double-Hits in a PMT

Not yet optimized for the milky PMT coating

Significant additional improvements to come

VacuumPhotocathodeGlass Window

Photo-ElectronPhoto-Electron

PhotonPhoton

Photon Absorption(Electron ‘Creation’)

e.g. in S-2040% ph. (400 nm) are absorbed

in a 30 nm thick

photocathode

Probability for anelectron to reach

the vacuum surface

Random Walk - mainly electron-imperfection

scattering (less e-e and e-phonon)

e.g. scattering length in S-20~25 nm

Therefore:Therefore:QE ~ 10-20%QE ~ 10-20%

VacuumVacuumPhotocathodePhotocathode

PhotonPhoton

Photon Absorption(Electron Creation)

Probability for anElectron to Reach

the Vacuum Surface

(Random Walk)

Photo-ElectronPhoto-Electron

(e.g. Substrate, Reflector,…)

& LOWER PRODUCTION

COST !

VacuumVacuumPhotocathodePhotocathode

UV PhotonUV Photon

UVPhoton Absorption(Electron Creation)Mostly @ Surface

Probability for anElectron to Reach

the Vacuum Surface

(Random Walk)

Photo-ElectronPhoto-Electron

Thin Photocathode on a Reflector,

Interference, Multi-layer Systems

Westinghouse, RCA, ITT

~1963-1975

Qua

ntum

Eff

icie

ncy

Wavelength

Reflection ModeReflection Mode vs. vs. Transmission ModeTransmission Mode

Extension Extension into into

““blue & blue & UV”UV”

~30-43 % QE bialkali

~190-450 nm

(Hamamatsu side-on PMT R7517)

TRANSMISSION PC REFLECTION PC

Source: Silvano Donati, Phosotosensors

REFLECTION-MODE PHOTOCATHODES

GOOD - air

WORSE – dense media

for larger incidence angles

H2OAIR

•Water Cheenkov – neutrinos etc.

•Liquid scintillator

•Plastic, crystal scintillator

Gamma-ray astronmy – Atmospheric Cherenkov Telescopes

&

Mass productionHigh performance

Mr. Mrs.