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## RE: Cerenkov Spectral Shape

Forum: Processes Involving Optical Photons
Re: Cerenkov Spectral Shape (Nicole Ackerman)
Date: 09 Nov, 2010
From: Robert Penny <Robert Penny>

 ```This is a multi-part message in MIME format. ------_=_NextPart_001_01CB8032.E0C93BF6 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable The Frank-Tamm distribution shows that the energy loss per unit length = from Cerenkov radiation is=20 dT/ds =3D 4 pi^2 z^2 e^2/c^2 Integral( 1 - 1/(beta^2 n^2) nu d nu ) beta is v/c,=20 n is the refractive index nu is the Cerenkov photon frequency But the energy per photon is proportional to nu. It looks to me then = that this is saying that for constant beta and n, the number of photons = produced per unit length is constant. Are you seeing constant energy distribution of photons or constant = number per unit energy. I'm no expert. Just referring to my copy of Evans, "The Atomic = Nucleus". -Rob. -----Original Message----- From: douglas@slac.stanford.edu on behalf of Nicole Ackerman Sent: Mon 11/8/2010 8:40 PM To: opticalphotons-g4hn@slac.stanford.edu Subject: Cerenkov Spectral Shape =20 *** Discussion title: Processes Involving Optical Photons I'm interested in studying the Cerenkov light coming from a radioactive decay in tissue. I believe I have things set up correctly (I am basing my physics lists and much of the structure on the LXe example) and I see Cerenkov photons generated in my volume. I'm confused about how the Cerenkov photons are generated. I know that the G4Cerenkov process uses RINDEX as a function of the energy of the photon, but RINDEX is effectively constant over optical photon energies for either water or tissue. I expected to see more photons generated with high energy based on the Frank-Tamm distribution, but when I plot the energy of the Cerenkov photons the distribution is flat in whatever energy region I have defined in my MaterialPropertiesTable. (The weight on all of them seems to be 1) Does this indicate I have made a mistake, or is the way it is supposed to be generated? Thank you for your assistance, Nicole ------------------------------------------------------------- Visit this GEANT4 at hypernews.slac.stanford.edu message (to reply or = unsubscribe) at:=20 http://hypernews.slac.stanford.edu/HyperNews/geant4/get/opticalphotons/35= 2.html=20 ------_=_NextPart_001_01CB8032.E0C93BF6 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable RE: Cerenkov Spectral Shape

The Frank-Tamm distribution shows that the energy loss = per unit length from Cerenkov radiation is

dT/ds =3D 4 pi^2 z^2 e^2/c^2 Integral( 1 - 1/(beta^2 n^2) nu  d nu = )

beta is v/c,
n    is the refractive index
nu   is the Cerenkov photon frequency

But the energy per photon is proportional to nu.  It looks to me = then that this is saying that for constant beta and n, the number of = photons produced per unit length is constant.

Are you seeing constant energy distribution of photons or constant = number per unit energy.

I'm no expert.  Just referring to my copy of Evans, "The = Atomic Nucleus".

-Rob.

-----Original Message-----
From: douglas@slac.stanford.edu on behalf of Nicole Ackerman
Sent: Mon 11/8/2010 8:40 PM
To: opticalphotons-g4hn@slac.stanford.edu
Subject: Cerenkov Spectral Shape

*** Discussion title: Processes Involving Optical Photons

I'm interested in studying the Cerenkov light coming from a = radioactive
decay in tissue. I believe I have things set up correctly (I am = basing
my physics lists and much of the structure on the LXe example) and I = see
Cerenkov photons generated in my volume.

I'm confused about how the Cerenkov photons are generated. I know = that
the G4Cerenkov process uses RINDEX as a function of the energy of = the
photon, but RINDEX is effectively constant over optical photon = energies
for either water or tissue. I expected to see more photons generated
with high energy based on the Frank-Tamm distribution, but when I = plot
the energy of the Cerenkov photons the distribution is flat in = whatever
energy region I have defined in my MaterialPropertiesTable. (The = weight
on all of them seems to be 1)

Does this indicate I have made a mistake, or is the way it is = supposed
to be generated?

Thank you for your assistance, Nicole

-------------------------------------------------------------
Visit this GEANT4 at hypernews.slac.stanford.edu message (to reply or = unsubscribe) at:
http://hypernews.slac.stanford.edu/HyperNews/geant4/get/o= pticalphotons/352.html

------_=_NextPart_001_01CB8032.E0C93BF6-- ```

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1 Re: RE: Cerenkov Spectral Shape   (Nicole Ackerman - 09 Nov, 2010)
RE: RE: Cerenkov Spectral Shape   (Penny, Robert D. - 09 Nov, 2010)
Re: RE: RE: Cerenkov Spectral Shape   (Gumplinger Peter - 09 Nov, 2010)
 to: "RE: Cerenkov Spectral Shape"
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