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From: Adrian Turner <akt21@ast.cam.ac.uk>
Subject: Coincidence Loss and Dead time correction in the OM
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Date: Fri, 14 Nov 2003 16:31:35 +0000
From: Adrian Turner <akt21@ast.cam.ac.uk>
To: xmmhelp <xmmhelp@xmm.vilspa.esa.es>
Subject: Coincidence Loss and Dead time correction in the OM
Dear Helpdesk,

I am rather confused by what the dead fraction in the OM actually is. 
Specifically does it refer to the loss in counts due to the frame 
transfer time on the CCD or does it refer to the deadtime of the 
photomultiplier that sits on top of the CCD?

Many thanks

Adrian Turner


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From: Pedro M. Rodriguez Pascual <xmmhelp@xmm.vilspa.esa.es>
To: akt21@ast.cam.ac.uk
Subject: Re: Coincidence Loss and Dead time correction in the OM (PR#9525)
Date: Tue Nov 18 07:11:14 2003
Dear Adrian, 

Please, see below the reply from OM experts, 

Sincerely, 

Pedro

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The dead fraction in the OM does refer to the frame transfer time of 
the CCD.  The photomultiplier does not have any dead time.  It can 
suffer from gain depression, which has an effect similar to coincidence 
loss (i.e. there is a limit to how fast you can operate and still see 
all the events); but this should not be called deadtime.

---------------------------------------------------------------------

> Dear Helpdesk,
> 
> I am rather confused by what the dead fraction in the OM actually is. 
> Specifically does it refer to the loss in counts due to the frame 
> transfer time on the CCD or does it refer to the deadtime of the 
> photomultiplier that sits on top of the CCD?
> 
> Many thanks
> 
> Adrian Turner
> 
> 

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