Comment mrc SNF 2010-09-09 16:57:13: Follow up

mtang at mtang at
Thu Sep 9 16:57:14 PDT 2010

Due to popular demand, here's a summary of this week's extended downtime and recovery.
The problem was that the plasma was not stable and reflected power could not be tuned under certain, normally stable conditions.  Jim McVittie figured either the RF generator was acting up or we had arcing or other short in the system.  He rigged up a high voltage DC monitor so he could test where the arc or short might be.  He located it to some parts in the cathode assembly.  Elmer and Mike drained the cooling water to begin tearing into the assembly and the short disappeared.  They refilled with fresh glycol/DI and the problem reappeared.  The water lines were replaced, although there were no leaks or anything obviously damaged. Cooling is supplied by a chiller where the resistivity is monitored, and cooling water itself  was OK.  With new cooling lines and new fittings, the problem is gone.

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