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From: bgaensler@cfa.harvard.edu
Subject: EPIC-pn small window mode
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Notification:


Date: Thu, 4 Oct 2001 22:36:34 GMT
From: bgaensler@cfa.harvard.edu
To: xmmhelp@xvsoc01.vilspa.esa.es
Subject: EPIC-pn small window mode
Full_Name: Bryan Gaensler
Submission from: (NULL) (131.142.42.158)


Hi,

I'm after some further clarification regarding EPIC-pn small window mode.

For a 6-ms frame time and 29% dead-time, I assume the read-out time is 1.7 ms.

But when does this 1.7 ms occur - during a 6-ms frame, or in
some "dead" interval between one frame and the next? If the former,
I presume data which are collected during read-out appear as out-of-time
events?
If the latter, are these events still included in the final event
list and marked as separate from those taken during the standard 6-ms
exposures,
or are no data recorded at all during read-out?

thanks,

Bryan



Followup 1

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Subject: Re: EPIC-pn small window mode (PR#2502)
To: xmmhelp@xvsoc01.vilspa.esa.es (Maria Santos-Lleo)
Date: Fri, 5 Oct 2001 10:23:37 -0400 (EDT)
Cc: bgaensler@cfa.harvard.edu (Bryan Gaensler)
From: Bryan Gaensler <bgaensler@cfa.harvard.edu>
> The pn detectors are read after the 6-ms per frame (in small window). 
> However, there are no shutters and therefore during readout, photons 
> can still be received. This data appear as out-of-time events, as 
> you though. One cannot correct for this effect in individual cases, 
> but only account for it statistically. 

Hi Maria,

Thanks for this information. But I'm still not entirely clear on
things. If I suppose that frame 1 begins at t = 0 ms, then does frame 2
begin at t = 6 ms? Or at t = 6 + 1.7 = 7.7 ms?  If the latter, are the
out-of-time events which occur between t=6ms and t=7.7ms time-stamped
as being in frame 1 or frame 2?

regards
Bryan


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Subject: Re: EPIC-pn small window mode (PR#2502)
To: xmmhelp@xvsoc01.vilspa.esa.es (Maria Santos-Lleo)
Date: Sat, 20 Oct 2001 01:59:43 +1000 (EST)
Cc: bgaensler@cfa.harvard.edu (Bryan Gaensler)
From: Bryan Gaensler <bgaensler@cfa.harvard.edu>
Hi Maria,

Thank you for this explanation. So one final clarification...
is it correct that during the read-out time, no data is
being taken? If the CCD has no shutter, why is this the case?

regards
Bryan

> 
> On small window mode, only part of one CCD is readout (currently 
> CCD O of Quadrant 1 being on the focus). The scientific parameters
> of this readout mode are the following:
> 
> - The integration time under the telescope PSF is 3.97 ms. 
> - The transfer time (i.e. the time during which the window is 
> fast-shifted towards the anodes) is 0.098 ms. 
> - The readout time is 1.521 ms. 
> 
> The above imply
> 
> - a frame time of 5.7 ms, 
> - relative number of out of time events of 2 per cent (per frame) 
> - a life time (1-dead time) of 71 per cent. 
> 
> Hope this helps you to prepare your observations
> 
> With best regards
> 
> Maria
> 


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Subject: Re: EPIC-pn small window mode (PR#2502)
To: xmmhelp@xvsoc01.vilspa.esa.es (Maria Santos-Lleo)
Date: Sat, 20 Oct 2001 03:37:41 +1000 (EST)
Cc: bgaensler@cfa.harvard.edu (Bryan Gaensler)
From: Bryan Gaensler <bgaensler@cfa.harvard.edu>
> the readout is followed by another fast transfer of the window, 
> before the next frame starts, so that the photons that arrived on 
> the mean time are "removed".

Maria, thanks - I now understand the significance of the
second readout.

But what happens to the photons that arrive "in the mean time"
and are then "removed"? Are they recorded and included
in the event list? Or are they simply discarded?

regards
Bryan


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Subject: Re: EPIC-pn small window mode (PR#2502)
To: xmmhelp@xvsoc01.vilspa.esa.es (Maria Santos-Lleo)
Date: Sat, 20 Oct 2001 03:45:29 +1000 (EST)
Cc: bgaensler@cfa.harvard.edu (Bryan Gaensler)
From: Bryan Gaensler <bgaensler@cfa.harvard.edu>
> I am sorry I do not know so much about the EPIC operating modes. 
> If you need an answer I should ask an expert, but I cannot 
> guarantee a quick reply. If you can wait for a few days, then 
> it is not a problem for me to ask, of course !. 
> Do you want me to ask for more details ?. Please let me know. 

Hi Maria,

Yes, thanks, I would be very grateful for some further information on
this. I apologise for all these questions, but I am trying to do a very
detailed simulation of a rather tricky experiment, and really want to
understand exactly how this mode works!

many thanks for your help,

Bryan


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Subject: Re: EPIC-pn small window mode (PR#2502)
To: xmmhelp@xvsoc01.vilspa.esa.es (Maria Santos-Lleo)
Date: Tue, 23 Oct 2001 13:59:19 +1000 (EST)
From: Bryan Gaensler <bgaensler@cfa.harvard.edu>
> I have got the answer to your question. I copy it below, hope it is 
> fine with you. 

Maria, many thanks. I think I now have all the info I need
to write my proposal - thanks for your patience!

regards
Bryan


Reply 1

Resend
From: Maria Santos-Lleo <xmmhelp@xmm.vilspa.esa.es>
To: bgaensler@cfa.harvard.edu
Subject: Re: EPIC-pn small window mode (PR#2502)
Date: Fri Oct  5 13:01:17 2001
Dear Bryan, 

The pn detectors are read after the 6-ms per frame (in small window). 
However, there are no shutters and therefore during readout, photons 
can still be received. This data appear as out-of-time events, as 
you though. One cannot correct for this effect in individual cases, 
but only account for it statistically. 

You can read the XMM-Newton User Handbook for a few more details 
about out-of-time events , e.g.

http://xmm.vilspa.esa.es/user/AO2/uhb/XMM_UHB/node105.html

with best regards

Maria Santos-Lleo, 
XMM-Newton SOC 
User Support Group


Reply 2

Resend
From: Maria Santos-Lleo <xmmhelp@xmm.vilspa.esa.es>
To: bgaensler@cfa.harvard.edu
Subject: Re: EPIC-pn small window mode (PR#2502)
Date: Mon Oct  8 12:48:43 2001
Dear Bryan, 

On small window mode, only part of one CCD is readout (currently 
CCD O of Quadrant 1 being on the focus). The scientific parameters
of this readout mode are the following:

- The integration time under the telescope PSF is 3.97 ms. 
- The transfer time (i.e. the time during which the window is 
fast-shifted towards the anodes) is 0.098 ms. 
- The readout time is 1.521 ms. 

The above imply

- a frame time of 5.7 ms, 
- relative number of out of time events of 2 per cent (per frame) 
- a life time (1-dead time) of 71 per cent. 

Hope this helps you to prepare your observations

With best regards

Maria


Reply 3

Resend
From: Maria Santos-Lleo <xmmhelp@xmm.vilspa.esa.es>
To: bgaensler@cfa.harvard.edu
Subject: Re: EPIC-pn small window mode (PR#2502)
Date: Mon Oct  8 13:00:30 2001
Dear Bryan

Just to clarify my previous mail, I forgot to let you know, in addittion
to the science parameters, the order of the sequence: 

The out-of-time events only occur during the fast transfer of the CCD 
lines, but not during the readout. The sequence is as follows: 

After the 3.97ms integration time, the relevant CCD lines are shifted in 
about 0.049 ms, then they are normally read in 1.521 ms and then the 
lines are shifted again in the remaining 0.049 ms (of the total 0.098 ms
quoted). This completes one PN small window frame. 

Hope everything is clear now

Regards

Maria


Reply 4

Resend
From: Maria Santos-Lleo <xmmhelp@xmm.vilspa.esa.es>
To: bgaensler@cfa.harvard.edu
Subject: Re: EPIC-pn small window mode (PR#2502)
Date: Fri Oct 19 17:32:54 2001
Dear Bryan, 

With regard to your question:

> Thank you for this explanation. So one final clarification...
> is it correct that during the read-out time, no data is
> being taken? If the CCD has no shutter, why is this the case?
> 

during the transfer time data is being collected, as there 
is no shutter, you cannot avoid it, this has the effect of 
creating the out-of-time events

after the charge is transferred it is read-out in the anodes, which 
are not exposed to the incoming photons 

the readout is followed by another fast transfer of the window, 
before the next frame starts, so that the photons that arrived on 
the mean time are "removed".

I hope that this makes sense to you. 

With best regards

Maria


Reply 5

Resend
From: Maria Santos-Lleo <xmmhelp@xmm.vilspa.esa.es>
To: bgaensler@cfa.harvard.edu
Subject: Re: EPIC-pn small window mode (PR#2502)
Date: Fri Oct 19 17:42:42 2001
Dear Bryan, 

I am sorry I do not know so much about the EPIC operating modes. 
If you need an answer I should ask an expert, but I cannot 
guarantee a quick reply. If you can wait for a few days, then 
it is not a problem for me to ask, of course !. 

Do you want me to ask for more details ?. Please let me know. 

With best regards

Maria


Reply 6

Resend
From: Maria Santos-Lleo <xmmhelp@xmm.vilspa.esa.es>
To: bgaensler@cfa.harvard.edu
Subject: Re: EPIC-pn small window mode (PR#2502)
Date: Fri Oct 19 18:05:11 2001
Dear Bryan, 

I forwarded your question to EPIC experts. As soon as I get something 
from them I will let you know. 

With best regards

Maria


Reply 7

Resend
From: Maria Santos-Lleo <xmmhelp@xmm.vilspa.esa.es>
To: bgaensler@cfa.harvard.edu
Subject: Re: EPIC-pn small window mode (PR#2502)
Date: Mon Oct 22 18:23:21 2001
Dear Bryan

I have got the answer to your question. I copy it below, hope it is 
fine with you. 

With best regards

Maria

---------------------------------------------------------------------------
Here is what I get from the EPIC User Manual, section 8.1 CCDs READOUT MODES
DESCRIPTION and 8.1.4 Small Window Mode:

The integration time is precisely 3.9709msec.
In order to then read the SW, we first shift 136 lines down. 
This takes 136 * 0.72usec = 0.098msec
then we shift and read 66 lines. 
This takes 66 * 23.05usec = 1.521msec
As the readout is also shifting the exposed area, the photons which have fallen
in it during the 1.5msec readout time are smeared, therefore it has been
decided
to clean-up the exposed area with an additional shift of 64 lines. 
This takes 63 * 0.72usec = 0.045msec.
In order to close the pipeline processing one last line is read which take
23.05usec.
After this a new integration time is started again on.

So the total frame time is:
3.9809msec int time + 0.098msec transfer + 1.521msec image read-out + 0.045
cleanup transfer + 0.023msec last readout = 5.6679msec.

This is what I calculate based on the User Manual numbers. 
For a precise description of the timing in the different p-n readout modes, 
please refer to
"Time resolution capability of the XMM EPIC pn-CCD in different readout modes",
Kuster, Markus; Benlloch, S.; Kendziorra, Eckhard; Briel, Ulrich G.; Proc. SPIE
Vol. 3765, p. 673-682


Reply 8

Resend
From: Maria Santos-Lleo <xmmhelp@xmm.vilspa.esa.es>
To: bgaensler@cfa.harvard.edu
Subject: Re: EPIC-pn small window mode (PR#2502)
Date: Tue Oct 23 08:04:40 2001
Dear Bryan

I am glad you finally got what you needed.

Let me wish you good luck with your proposal

Best regards

Maria

Up to top level
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