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Forum: Processes Involving Optical Photons
Re: Question Cerenkov Process problem
Date: 14 Oct, 2015
From: Gumplinger Peter <Gumplinger Peter>

Dear Sage,

Cerenkov photons are emitted on the surface of a CONE, whose opening angle with respect to the particle's instantaneous direction is theta_c. The Cerenkov photons will not be just tangential to the xz plane in the detector plane at point (x=y=0,z=450mm). You see a nice little arc of the ring in your top fig. 1.

The user may limit the step size by specifying a maximum (average) number of Cerenkov photons created during the step, using the SetMaxNumPhotonsPerStep(const G4int NumPhotons) method. NumPhotons should not be a small integer (e.g. not 1 or even 0.5!) Nothing smaller than 20 - I'd suggest.

If you changed your arrangement such that the incoming e- beam is along the z axis then I'd expect the xy plane distribution at z=450mm to be a narrow filled ring with radius ~ 450mm * tan(theta_c) and a width of roughly the thickness of the SiO2.

Peter

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