Shutdown drytek2 SNF 2009-01-21 11:40:09: Matching network upgrade ....

shott at snf.stanford.edu shott at snf.stanford.edu
Wed Jan 21 15:32:23 PST 2009


Added 200 pf of fixed capacitance and placed the smaller of the two hand-wound inductors in paralled with the roller inductor.  This was the 2-turn inductor made by wrapping 1/4" copper tubing around a piece of 1 1/4" Schedule 80 PVC pipe.  The separation between adjacent loops is about 1/4 inch as well.
This improved tuning performance.  I was able to comfortably tune an oxygen plasma with a coil setting of 1.6 and a capacitor setting of about 2.2.  If anything, I may have increased the capacitance too much ... and should consider removing 50-100 pf in the future.
When tuning I saw a forward power of 425 watts and could consistently achieve a reflected power of 20 watts or less.
Note:  I measured my new fixed inductor to be 670 nH, my larger inductor was about 840 nH (both measured with the HP 4275 LCR meter with a small signal frequency of 1MHz.  The reading was fairly independent of frequency.
John




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