Search found 1387 matches

by Dennis P Brown
Tue Jan 16, 2018 1:51 pm
Forum: Fusor Construction & Operation (& FAQs)
Topic: A Bunch of Failures
Replies: 46
Views: 1146

Re: A Bunch of Failures

In a previous post you said: Note: I had filled the pump up to the max marking. I lost this much oil after 1hr 10mins of combined run time (two 20 minute runs and one 30 minute run). Is this normal? No, that is not normal! No way that much oil should be lost even if the ballast is open. I have used ...
by Dennis P Brown
Sat Jan 13, 2018 11:44 am
Forum: Fusor Construction & Operation (& FAQs)
Topic: A Bunch of Failures
Replies: 46
Views: 1146

Re: A Bunch of Failures

Are you just pumping on the vacuum gauge? A decent pump will never pull just 500 microns; either you have a massive leak - i.e. a bad o-ring or non-vacuum tight connection between the gauge and pump body (Also, have you tried listening for a leak?) or water in the pump (so Bruce's advice will help t...
by Dennis P Brown
Thu Jan 11, 2018 2:05 pm
Forum: Neutrons, Radiation, and Detection (& FAQs)
Topic: Ludlum 12 Ratemeter Issues
Replies: 10
Views: 332

Re: Ludlum 12 Ratemeter Issues

My unit had a few issues being old and having had corrosion issues. The later problem is not your issue here. Did you ohm the cable and cable & unit to confirm no grounding issues with the high voltage side of the unit/cable? That can be an issue - also, make certain the high voltage line in the uni...
by Dennis P Brown
Wed Jan 10, 2018 5:00 pm
Forum: Vacuum Technology (& FAQs)
Topic: Question About Design Trade-offs for Backing Pumps
Replies: 20
Views: 439

Re: Question About Design Trade-offs for Backing Pumps

If you are hoping to use a diffusion pump without a real cold trap your system might not get below 10^-6 torr. Worse, the oil vapor back flow from the DP will contaminate the system even if you gate the DP off after reaching low enough for the ion pump to start. You might need a dry ice/alcohol or s...
by Dennis P Brown
Tue Jan 09, 2018 11:16 am
Forum: Fusor Construction & Operation (& FAQs)
Topic: A Bunch of Failures
Replies: 46
Views: 1146

Re: A Bunch of Failures

As long as you are prepared to properly clean out the pump - remember, that is no simple task to really remove the wrong oil if its vapor pressure may be a future issue - then fine. The oil will provide the pump lubrication to enable you top test its operation. However, might be easier in the long r...
by Dennis P Brown
Mon Jan 08, 2018 10:39 am
Forum: Fusor Construction & Operation (& FAQs)
Topic: A Bunch of Failures
Replies: 46
Views: 1146

Re: A Bunch of Failures

While 500 microns is terrible for a good pump, that it had little oil can explain that figure but also, an excellent way to destroy the pump. Always fill the pump to the correct level before operation.
by Dennis P Brown
Fri Jan 05, 2018 3:33 pm
Forum: Fusor Construction & Operation (& FAQs)
Topic: A Bunch of Failures
Replies: 46
Views: 1146

Re: A Bunch of Failures

That appears to be a good pump and will certainly work with any DP as long as it gets below 50 microns; so when you say but is rated to reach 7.5 X 10^-4 Torr. I figure that will be enough to back a diffusion pump. So, as long as it gets under 5 microns (assuming the system has no real leaks) you wi...
by Dennis P Brown
Thu Jan 04, 2018 12:37 pm
Forum: Neutrons, Radiation, and Detection (& FAQs)
Topic: Ludlum 12 Ratemeter Issues
Replies: 10
Views: 332

Re: Ludlum 12 Ratemeter Issues

One of my battery wires had a an issue within the wire - must have been broken making poor contact. I replaced it and that fixed one of my battery issues. The other is an internal spring which, due to corrosion, I can't replace. So, I installed an external battery (not saying do this later part.) So...
by Dennis P Brown
Wed Jan 03, 2018 12:06 pm
Forum: Neutrons, Radiation, and Detection (& FAQs)
Topic: Ludlum 12 Ratemeter Issues
Replies: 10
Views: 332

Re: Ludlum 12 Ratemeter Issues

Two very possible problems: first, (and hopefully, the least likely) if the battery contacts are bad or not making proper contact, it is very easy to measure low battery on the meter display (assuming your batteries are new - 1.6 volts each.) Assuming the batteries are fresh and put in correctly, pr...
by Dennis P Brown
Fri Dec 29, 2017 5:26 pm
Forum: Fusor Construction & Operation (& FAQs)
Topic: Conversion to a Small Chamber Fusor
Replies: 2
Views: 151

Re: Conversion to a Small Chamber Fusor

Added the D2 line and tested the system under high voltage. Very difficult to control - seasoning helped but didn't cure that issue at all. Found (finally after a lot of effort) a semi-stable operating region for my system - 20/21 kV @ 43 microns. Power (after chasing both the current and pressure) ...