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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.