From: Serguei Zelepukin
Sent: 24 July 2008 00:02
To: Dave Cockerill
Cc: Ken Bell; Wolfgang Funk; Botjo Betev; Werner Lustermann; Guenther
Dissertori; Diogo Raphael Da Silva Di Calafiori
Subject: Dee's rear screen cooling

Attachments: 2008_07_22_Dee3_moderator.ppt


Dear Dave, dear all,

Regarding the Dee rear screen / moderator cooling:

on Dave's request I have installed temperature probes on the inner surface of all 4 Dee's rear screens;
the idea was to monitor rear screens in P5 during EE commissioning in order to find whether it's needed
to have active cooling on these screens.

Just to remind: I don't have signal cables to provide a regular readout of these probes in the final EE configuration.

Initial solution was to measure thermistor resistancies with a multimeter and then manually convert to temperatures...
While this is still possible I have provided a more reliable and "comfortable" option:
Rear screen sensors are wired to a 9-pin connector of the same type as the environmental screen sensors
(which are supported with readout). Connector is easily accessible at the right Dee's "corner" -- integration area view.

This optiond gives us a possibility:
-- to read rear screen probes with a regular cabling/readout
   in B.867 (swapping between Env.screen and Moderator);
-- do the same in p5 -- providing we have access to Dee's
   patch panels;
-- in the very end -- to use a Dee's humidity cable to send 
   rear screen temperatures to the readout.
   (again we need access to Dee's PPs to make re-connection).
   This latter feature requires extension cables to be
   produced to connect between a rear screen connector and
   a signal cable (Dee -- readout).

That was a preamble to introduce you...

Now,
from the B867 experience (unfortunately extremely short term and definitely not complete):

Dee-3 was the only one for which I had a chance to monitor more than just a few hours (rear screen when it's in place).
Plots are in the attachment -- sorry about not having time to change labels etc from EB SMs to EE Dee's.

These plots show that in the Dee's electronics compartment (which is closed) in the absence of the rear screen cooling
the temperature grows considerably! (electronics is cooled by cooling blocks)

I have never seen stabilized conditions... by the attached plot the difference between the ambient temperature
(backplate) and the rear screen temperature can easily be more than 3 deg C

Unfortunately no one Dee was tested for a ~week with LV ON and so we have no data about the stabilized conditions...
the difference may be more significant.

From the above very preliminary measurements I would propose:
-- during the EE commissioning (Dee-1,2) monitor the rear screens
   instead of env.screens;
-- complement these measurements with DCU readings of the
   board's temperature probes.

Also, we can connect rear screens instead of Dee's humidity probes (but again not immediately -- several transition
cables have to be produced).

Please let me know about your decision possibly sooner as I may need to produce transition/extension cables -- 
and these cables have to be installed on Dee's...

Thank you,
cheers, Serguei


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