Fusor Forums

James,

Is this company local to the Idaho Falls area?

In any case, how to measure high vacuum without a proper TC or similar gauge?

Water boils at about 17 torr. This is way too high for fusor work, but if you wet the underside of a large rubber stopper (the kind used in chemistry) and stop up the pump and then check it after a minute, a dry cork indicates than you have pulled at least 17 torr.

A simple but effective measurement would be to create a tiny spark gap in this rubber stopper and reference the Paschen Curve and measure the arc over voltage. You'll need a low current high voltage power supply, such as a ion generator, something to vary the voltage and digital volt meter and possibly a high voltage resistor divider. If this all confuses you, I can explain more in detail.

I am willing to bet your pump is OK!

If the shaft isn't frozen and the pump develops suction when it turns, there's a GOOD chance it is going to work reasonably well with little more than the obligatory oil change. There could still be leaky seals and vanes, but the test this huckster did for you with what sounds like a cheap and imprecise gauge has no credibility one way or the other.

I like Allen's suggestion of a discharge tube for an ad-hoc test, if you can't find someone with a decent thermocouple gauge in your vicinity. A test tube makes a fine electrodeless discharge tube, easily excited with a Tesla coil or a small gas-tube power supply, eBay 220718755241 for example.

-Carl

Actually, something like a DV-6 thermocouple gauge would be a fine investment for general use and specifically for determining the relative health of the pump. I'd be willing to bet that if you searched Ebay right now for "thermocouple gauge" or "Hastings vacuum", you'd find several at reasonable prices.