Message: RE: Cerenkov Spectral Shape Not Logged In (login)
 Next-in-Thread Next-in-Thread
 Next-in-Forum Next-in-Forum

None RE: Cerenkov Spectral Shape 

Forum: Processes Involving Optical Photons
Re: Sad 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

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
<HTML>
<HEAD>
<META HTTP-EQUIV=3D"Content-Type" CONTENT=3D"text/html; =
charset=3Diso-8859-1">
<META NAME=3D"Generator" CONTENT=3D"MS Exchange Server version =
6.5.7655.4">
<TITLE>RE: Cerenkov Spectral Shape</TITLE>
</HEAD>
<BODY>
<!-- Converted from text/plain format -->

<P><FONT SIZE=3D2>The Frank-Tamm distribution shows that the energy loss =
per unit length from Cerenkov radiation is<BR>
<BR>
dT/ds =3D 4 pi^2 z^2 e^2/c^2 Integral( 1 - 1/(beta^2 n^2) nu&nbsp; d nu =
)<BR>
<BR>
beta is v/c,<BR>
n&nbsp;&nbsp;&nbsp; is the refractive index<BR>
nu&nbsp;&nbsp; is the Cerenkov photon frequency<BR>
<BR>
But the energy per photon is proportional to nu.&nbsp; 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.<BR>
<BR>
Are you seeing constant energy distribution of photons or constant =
number per unit energy.<BR>
<BR>
I'm no expert.&nbsp; Just referring to my copy of Evans, &quot;The =
Atomic Nucleus&quot;.<BR>
<BR>
-Rob.<BR>
<BR>
-----Original Message-----<BR>
From: douglas@slac.stanford.edu on behalf of Nicole Ackerman<BR>
Sent: Mon 11/8/2010 8:40 PM<BR>
To: opticalphotons-g4hn@slac.stanford.edu<BR>
Subject: Cerenkov Spectral Shape<BR>
<BR>
<BR>
*** Discussion title: Processes Involving Optical Photons<BR>
<BR>
I'm interested in studying the Cerenkov light coming from a =
radioactive<BR>
decay in tissue. I believe I have things set up correctly (I am =
basing<BR>
my physics lists and much of the structure on the LXe example) and I =
see<BR>
Cerenkov photons generated in my volume.<BR>
<BR>
I'm confused about how the Cerenkov photons are generated. I know =
that<BR>
the G4Cerenkov process uses RINDEX as a function of the energy of =
the<BR>
photon, but RINDEX is effectively constant over optical photon =
energies<BR>
for either water or tissue. I expected to see more photons generated<BR>
with high energy based on the Frank-Tamm distribution, but when I =
plot<BR>
the energy of the Cerenkov photons the distribution is flat in =
whatever<BR>
energy region I have defined in my MaterialPropertiesTable. (The =
weight<BR>
on all of them seems to be 1)<BR>
<BR>
Does this indicate I have made a mistake, or is the way it is =
supposed<BR>
to be generated?<BR>
<BR>
Thank you for your assistance, Nicole<BR>
<BR>
-------------------------------------------------------------<BR>
Visit this GEANT4 at hypernews.slac.stanford.edu message (to reply or =
unsubscribe) at:<BR>
<A =
HREF=3D"http://hypernews.slac.stanford.edu/HyperNews/geant4/get/opticalph=
otons/352.html">http://hypernews.slac.stanford.edu/HyperNews/geant4/get/o=
pticalphotons/352.html</A><BR>
<BR>
</FONT>
</P>

</BODY>
</HTML>
------_=_NextPart_001_01CB8032.E0C93BF6--

Inline Depth:
 1 1
 All All
Outline Depth:
 1 1
 2 2
 All All
Add message: (add)

1 Feedback: Re: RE: Cerenkov Spectral Shape   (Nicole Ackerman - 09 Nov, 2010)
(_ None: RE: RE: Cerenkov Spectral Shape   (Penny, Robert D. - 09 Nov, 2010)
(_ Feedback: Re: RE: RE: Cerenkov Spectral Shape   (Gumplinger Peter - 09 Nov, 2010)
 Add Message Add Message
to: "RE: Cerenkov Spectral Shape"

 Subscribe Subscribe

This site runs SLAC HyperNews version 1.11-slac-98, derived from the original HyperNews