At 600Cwet-H₂ is let into the V.I. furnace.  The controller thermocouples near the top and bottom elements show a reduction of heat.  Seamus theorized the elements got a surge in current, due to the feedback loop gain, and because there was a gap in shielding between the window ceramic and the bottom elements, the window cracked at that point.

 

The plate, which was used in the V.I. furnace during the old runs, was no longer available, and the plate that was used was not large enough to completely shield the window from the bottom elements, which are about six inches from the ceramic.  (The furnace was not open so a picture could not be taken of the set-up)

 

 

The ceramic cracked so badly, that a chip fell out and was brazed in place.  This is the way the ceramic looked at braze temperature.

 

The braze material flowed into puddles as shown.

 

 

These are the action items.  1) A completely thermo-coupled moly ring and window will be run and monitored for temperature variations.  2) The soak profile was incorrectly set for 550C.  3) A stainless steel shielding tent will be fabricated for the dummy run.

 

Seamus can be reached at, seamususa@msn.com

 

 

notes by Mike Neubauer 9/22/2000