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Forum: Processes Involving Optical Photons
Re: Question question regarding PMT photocathode and quantum efficiency (Athreya Shankar)
Date: 16 Jul, 2012
From: Athreya Shankar <Athreya Shankar>

Hello all,

I thought about my doubt a little more, and I arrived at this conclusion:

The spectral response of a PMT has a higher wavelength cut-off because of the nature of the photoelectric effect. The lower wavelength cut-off is because of the transmission characteristics of the window material. Thus, I can use the QE characteristics of the photocathode-cum-window system, provided I do NOT take into account the transmittance property of the window material, since this is already taken care of in the wavelength-dependent QE values. This I can accomplish by specifying the ABSLENGTH property of the window to a wavelength-independent arbitrarily high value.

The above solution ensures that the effect of the glass window on transmission is taken into account, as well as ensures that the possibility of reflection off the glass window-scintillator surface interface is not lost. However, if the photocathode reflectivity comes into play and the photon is reflected back into the glass window region, then, since we have not set the transmittance properties, the photon may travel around for longer than reality.

Is my reasoning correct ?

Thanks in advance,

Athreya

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