DUO 008 fixed, TPH270 dead...

. zaterdag 23 juli 2011
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The DUO 008b pump I have seemed to have a problem with it's thermal protection.
After about an hour it switched off, but sometimes it just switched off randomly.
I replaced the thermal protection switch (a relay with a PTC), and I replaced the off switch. Worked fine for 5 hours continuously after that:

And then.. after a two hour bake out at 100 deg. C, cooling down and pumping for about 3 hours until 4e-7, my TPH270 started to make an unfamiliar noise, the pressure went up, the noise got louder...
Goodbye TPH270... I don't know if I can fix it. It's probably the bearings.
But I did finish two 3d drawings for presenting the idea of the "octavio". Using FreeCAD wonderful program, really free and open source, not completely bug-free, but easy to work with, also tried wings3d but that was much harder.

Bake out

. dinsdag 19 juli 2011
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Trying bake out,

Got 4.9e-7 with about 1 hour of bake-out at 70 deg. C. Have to do a lot more bake out to get lower.
Will build a temperature control system to do longer bake out.
Working on the drawings of the "octavio" and will present the ideas here soon.

Mass spectrometer failure and bake out

. zaterdag 9 juli 2011
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After cleaning every vacuum component (again) I tried bake out, for a short time, just heating the setup to about 60 deg. C for 10 to 15 minutes, using a paint burner.

Seemed to do the right thing to the H2O pressure, but then my mass spectrometer showed a very low pressure, about 8e-8, which was obviously wrong, the cold cathode gauge was still in the e-6 range.

The researchers at radiantmatterresearch.com had the same problem with the same QMA 064 sensors. They tried cleaning with acetone, without any effect.

After posting it on the fusor board the idea is to start cleaning with H2SO4, NH4OH and H2O2.

We think that over the years various gasses got buried into the collector and were released during bake out, reacting and forming an insulating layer on the collector, so we have to do proper bake out before cleaning it, or the same affect would come up again.

But the bake out did have a positive effect, pressure is now in the e-7 range, to get to e-8 I need longer bake out.
I've ordered 50x Vishay PTC heating elements for 110 deg. C, they can be connected to 230 VAC directly and will heat up until reaching a specified temperature. Very simple and cheap. At 1200 ohms they will start at 44 watt and start giving of less power at about 100 deg. C, and switch off almost completely when the surface temperature is 140 deg. C.

Only a factor 12 to go (indication of the cold cathode is a bit on the high side, so t might be better than indicated):