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Need of a preamplifier [message #721] Fri, 06 August 2004 19:19 Go to next message
Chilo Garabatos is currently offline  Chilo Garabatos
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Registered: August 2004
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From: lxial22.gsi.de
I am of the opinion that one should use a preamplifier (connected to the anodes through a capacitor) for testing the chambers, at least for measuring the absolute gain (by counting X-ray signals and recording the current at the same time).
In addition, it looks to me that being able to look at the signals on the scope would be of great benefict for debuging purposes: the behaviour of the X-ray tube, the observation of possible discharges due to dust, whether the gain non-uniformity is due to noise or not, etc.
What do you think?
Regards,
Chilo
Re: Need of a preamplifier [message #724 is a reply to message #721] Mon, 09 August 2004 09:06 Go to previous messageGo to next message
Clemens Adler is currently offline  Clemens Adler
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Registered: March 2004
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From: *kip.uni-heidelberg.de
Hi Chilo,
I think that's probably a very good idea. I forwarded your message to Rainer (I think he's not subscribed).
What is your experience in case of a dust discharge? would Saschas observation that the current settles within ~2 hours be consistent with your experience?

cheers,
Clemens
Re: Need of a preamplifier [message #725 is a reply to message #724] Mon, 09 August 2004 11:12 Go to previous messageGo to next message
Chilo Garabatos is currently offline  Chilo Garabatos
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From: lxial22.gsi.de
Hi, Clemens,
discharges due to dust can happen; one could tell if there was a preamp to the scope. For the records, the process of burning potential dust is called conditionning. The time scale is difficult to judge.
But current that dissapears can also be due to humidity which dries out, or to the capacitance of the system (but 2 hours is perhaps too much for that). Turning HV off and on after a few hours (with gas off or on) would give more information.
Regards and keep having fun.
Chilo
Re: Need of a preamplifier [message #726 is a reply to message #721] Mon, 09 August 2004 11:25 Go to previous messageGo to next message
Harald Appelshaeuser is currently offline  Harald Appelshaeuser
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From: kp1nbp016.gsi.de
Hi Chilo, Clemens,

I agree that a preamp is a useful thing for chamber tests. After all, using a scope allows to test the chamber also with a rather low rate source.

Clemes, did you record the current history of your "dust events"?

Regards, Harry
Re: Need of a preamplifier [message #728 is a reply to message #726] Mon, 09 August 2004 12:18 Go to previous messageGo to next message
Clemens Adler is currently offline  Clemens Adler
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From: *kip.uni-heidelberg.de
Hi Harry,
Rainer and Sascha are the persons responsible for testing the chambers (therefore I did not record anything). Sascha did however record that dust event; I'll ask him whether he can post the plot somewhere.
cheers,
Clemens
Re: Need of a preamplifier [message #730 is a reply to message #721] Mon, 09 August 2004 22:45 Go to previous messageGo to next message
Sascha Freuen is currently offline  Sascha Freuen
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From: *dip.t-dialin.net
Conditioning of Chamber L2C0#3:
==================================

Approaching the following settings in steps of 50V AnodeVoltage, after each step waiting till the Anodecurrent goes down under 10 nA :
AnodeVoltage = 1600 V , DriftVoltage = - 1935 V

3 times in the first hours with this settings the trip-current of 5 uA was reached, although besides the Anodecurrent seemed to be on a constant lvl of ~ 5 nA

During a second measurement over night (during first night a current trip happend) we saw this strange? progression of the Anodecurrent :

http://img7.exs.cx/img7/6682/k1.png

The next night everything seemed to be pretty normal :

http://img7.exs.cx/img7/1230/k2.png

During one more test with DriftVoltage = -2100 V the Anodecurrent was constantly ~6 nA


I propose to implement a new forum-section "Alice TRD Chamber testing"

Regards

Sascha

[Updated on: Wed, 11 August 2004 00:45]

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Re: Need of a preamplifier [message #732 is a reply to message #730] Tue, 10 August 2004 10:39 Go to previous messageGo to next message
Harald Appelshaeuser is currently offline  Harald Appelshaeuser
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From: kp1nbp016.gsi.de
Dear Sascha,

thanks for providing us your beautiful figures. I am not quite sure though whether I understood everything correctly: after you reached the nominal voltages the current was low (~ 5 nA) except for three excursions which reached the trip limit, is this correct?

I think the 'eruption' may well be due to a burning piece of dust. It lasted for an hour or so, right?

I will organize an extra forum for chamber tests. I think it is very useful if people from time to time submit some of their results there.

Regards, Harry
Re: Need of a preamplifier [message #737 is a reply to message #732] Tue, 10 August 2004 13:28 Go to previous message
Sascha Freuen is currently offline  Sascha Freuen
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From: *kip.uni-heidelberg.de
Dear Harry

Harald Appelshaeuser wrote on Tue, 10 August 2004 10:39

I am not quite sure though whether I understood everything correctly: after you reached the nominal voltages the current was low (~ 5 nA) except for three excursions which reached the trip limit, is this correct?


Thats correct

Harald Appelshaeuser wrote on Tue, 10 August 2004 10:39

I think the 'eruption' may well be due to a burning piece of dust. It lasted for an hour or so, right?


Yes it lasted for ~75 min.

Harald Appelshaeuser wrote on Tue, 10 August 2004 10:39

I will organize an extra forum for chamber tests. I think it is very useful if people from time to time submit some of their results there.


Very good- thank you.


Regards

Sascha
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