Minutes of feedthrough meeting of 30 July, 2001.
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Present: Pof, GV, AD, ASD, FH, MGF, RKK

*) Milestones

	- The HEC ft11 and Special ft12 were cold tested
	  last week.  ft12 developed a short to ground
	  on pin 7 slot 9b at the cold flange (unknown
	  which side) during the cold test.  The short,
	  approximately 4.7 Ohms to ground, was not present 
	  after cabling, and has not gone away after 
	  subsequent warming.  Given the high resistance
	  of the short, we speculate that it is a small
	  piece of conductive debris that is causing the
	  short.  Pof will look into the possibility of
	  attempting to burn it out by running some
	  regulated current through it at a relatively
	  low voltage.  We'll do some trials with a prototype
	  vacuum cable first to ensure that the vacuum cable
	  isn't damaged.

		- Update on Tuesday: After setting up a
		  bench test, we determined that with 500 mA
		  run through a vacuum cable and a 5 Ohm
		  resistor (voltage drop = 3V) the 5 Ohm
		  resistor quickly became too hot to touch,
		  while the vacuum cable showed no evidence
		  of heating.  We tried this on the shorted
		  pin, and got no higher than 300 mA in
		  just a few seconds before the current
		  dropped abruptly to zero and the short
		  was apparently burnt off.  We can hopefully
		  use this technique to cure ground shorts
		  which appear after shipping the feedthroughs
		  to CERN or after installation.

		  We have applied this same technique to
		  the ground short on ft00.  Less than
		  100 mA was required before the short
		  disappeared.  We now have only one feedthrough
		  with one ground short, ft01, which I will
		  investigate next week.

	- The ambient flange heater with a temperature
	  controller was tested during the cold test of
	  the HEC ft11.  Holding the centre of the heater
	  at 24.9 degrees, with an ambient room temperature
	  of 22.6 degrees, the power required by the heater
	  was 21.5 Watts.  This is slightly lower than the
	  24 - 28 Watts predicted, however the ambient room
	  temperature was also higher than usual.  It should
	  however also be pointed out that these tests were
	  conducted without the warm cables attached and 
	  without the enclosure of the pedestal, whose effects
	  on the ambient temperature around the warm cables
	  are unclear.

	- The replacement pincarrier for the leaker that was
	  returned to Glasseal has been cold cycled and
	  leak tested and is ready for use.

*) Five heater plates are to be milled this week for the
   fuse block.  Once these are done, the heater plates and
   other parts will be turned over to the electronics shop
   to be assembled.  

*) Aaron and Greg are leak checking the vacuum manifold
   to be used at CERN.

*) Aaron and Greg are working on the shipping crates.

*) There was some discussion regarding the intended use of
   a heater shunt to provide extra heating to the LV HEC
   warm cables.  Since space is already tight in the pedestal
   region, it is unclear that there would be enough room to
   manouver the LV cables to their correct placement if
   they are constrained by the heater shunt.  It is also
   not clear that they are really required; with the heater
   plate held at 25 degrees, there was no sign of condensation
   on the LV pins at the warm flange (the relative humidity 
   was about 50%).  Terry had suggested the shunts as a simple
   passive means of preventing condensation on the LV pins,
   and assuming that the HEC heater plates would be kept
   at the same (lower) temperature as all the others.  If
   we decide to go for the heater shunt option, then we will
   have to work with a more complete pedestal mockup (perhaps
   BNL's) and with the real LV HEC warm cables to determine
   the optimum design.  If we go for the elevated HEC heater
   plate temperature option, we will have to check with those
   in charge of such matters that we can control the heaters
   such that the HEC feedthroughs are maintained at a higher 
   temperature than the others.

*) Pof will check with Claude Eder of LAL, who gave the talk
   "Control of feed-through heaters, power supply" at the
   Cryostats and Cryogenics meeting at the July LARG week,
   whether or not it will be possible to control some (ie,
   the HEC) flange heaters at a higher temperature than the
   others.  Pof will also request a copy of the talk.

*) BNL is currently working on their ft # 28.

*) The feedthrough meeting minutes (under password access for
   external sites) are being maintained at:
     http://wwwhep.phys.uvic.ca/~uvatlas/atlas/feedthroughs/
   The CERN presentations (not under passord access) are also
   at that site, in both the original ppt/doc formats and also
   pdf format.

Agenda for next week: (moved to 10:00 Wednesday 8 August)
^^^^^^^^^^^^^^^^^^^^^
- Milestones
- Shipping crates
- Heater plate wiring jig
- Plans for the week
- AOB