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Registered Member #2372
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Posts: 62
So usually with RF discharges they run best when the RF frequency matches the electron-neutral collision frequency because on average the electrons will collide once per cycle and the most energy will be transferred on average from the free electrons to the gas. This can be found from some math that is in the Lieberman and Lichtenberg plasma processing book. The way you couple energy into a plasma is through collisions, without them the electrons would just go back and forth until you turned off the electric field and no net energy would be transferred to them. You should be able to find more stuff about this if you look up how they make inductively coupled plasma sources, which are used for a lot of different plasma processing applications.
Registered Member #1134
Joined: Tue Nov 20 2007, 04:39PM
Location: Bonnie Scotland
Posts: 351
MinorityCarrier wrote ...
If your pump stops working when the oil heats up, something is wrong with your pump, or you have the wrong oil in it.
First off, I presume you have a rotary vane pump. You should be running a hivac pump oil eqivalent to Inland 19. Your pump should be able to run continuously and maintain vacuum when hot. Hopefully you didn't put automotive oil in your pump.
I would say so too, or incorrect use of / not using the gas ballast if it has one. Running the pump at atmosphere for any length of time will saturate the oil with water, which will also cause the symptoms described.
If a gas ballast is provided, pump down the chamber first, with the ballast valve open, leave it for running say 10 min, then close the valve. You should reach a lower ultimate pressure, that should be less affected by the pump temp.
Registered Member #2123
Joined: Sat May 16 2009, 03:10AM
Location: Bend, Oregon
Posts: 312
Ballasting is used primarily to prevent molecular flow of pump oil back up the foreline, and is sometimes used as a means to regulate pressure in the 1K millitorr realm. Most R.V. pumps I work with do not have ballasting inputs to the pump block, ballasting is installed upstream in the foreline plumbing. I presume he ISN'T running the pump open to atmosphere or running very high ballasting gas flow, that tends to blow out the (expensive) oil and ultimately ruin the vanes/score the pump chamber walls/ruin the pump.
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Pink light emission from low pressure gas lamp
