Search found 447 matches

by ian_krase
Mon Aug 20, 2018 12:31 am
Forum: Vacuum Technology (& FAQs)
Topic: Debugging an Inficon PKR 251 Series Gauge
Replies: 2
Views: 68

Re: Debugging an Inficon PKR 251 Series Gauge

Rotary vane pumps definitely get quiet when the pressure and gas load are small, but it's not terribly sensitive.
by ian_krase
Wed Aug 15, 2018 9:29 am
Forum: High Voltage - Fusor Input Power (& FAQs)
Topic: DIY hermetic feedthroughs: Has anybody done this?
Replies: 5
Views: 304

DIY hermetic feedthroughs: Has anybody done this?

DIY feedthroughs are fairly common in Fusorland because you can make them with rubber or sometimes vacuum-epoxy seals. In the days of John Strong, wax seals were also used. However, the kinds of feedthroughs you can buy, the really hermetically sealed ones, are always either glass to metal sealed or...
by ian_krase
Mon Aug 13, 2018 7:14 pm
Forum: Advanced Technical Discussion Area
Topic: Fusor Simulation
Replies: 1
Views: 189

Re: Fusor Simulation

I wish I could afford this software. My mass spectrometer project would be far easier.
by ian_krase
Sat Aug 11, 2018 6:58 pm
Forum: Announcements and Site Administration Topics
Topic: Sunnyvale Mini Meetup -- August 11
Replies: 5
Views: 641

Re: Sunnyvale Mini Meetup -- August 11

Quick update: I will be about 20 minutes late.
by ian_krase
Fri Aug 10, 2018 6:09 am
Forum: New User Chat Area
Topic: Maintaining a vacuum in the absence of a pump.
Replies: 7
Views: 394

Re: Maintaining a vacuum in the absence of a pump.

Of course there are also mercury thyratrons. The biggest ones of these, called ignitrons, have a pool of mercury covering the entire bottom of the tube, which serves as an electrode that can't melt under high current because it is already molten. It seems like you could make an (obviously non-fusing...
by ian_krase
Fri Aug 10, 2018 6:07 am
Forum: The Trading Post
Topic: 10x CHEAP TURBOS w/ controller (Pfeiffer TMH 261) on ebay ~$50
Replies: 9
Views: 658

Re: 10x CHEAP TURBOS w/ controller (Pfeiffer TMH 261) on ebay ~$50

These lots of low-ish cost small turbos are the modern version of the cheap surplus diffpumps of days past.

Sadly, while it is very hard to kill a diffpump other than by losing the Christmas Tree, you never know what condition these things are in.
by ian_krase
Thu Aug 09, 2018 6:26 am
Forum: New User Chat Area
Topic: Maintaining a vacuum in the absence of a pump.
Replies: 7
Views: 394

Re: Maintaining a vacuum in the absence of a pump.

Maintaining a hard vacuum in the absence of a pump is *comparatively* simple, by which I mean it's finicky and I don't know how many people here have ever done it. First, the chamber must be hermetically sealed -- no rubber gaskets allowed. Everything must be brazed, welded or glass-sealed together ...
by ian_krase
Fri Jul 27, 2018 5:32 am
Forum: New User Chat Area
Topic: Fusor Plan
Replies: 9
Views: 770

Re: Fusor Plan

You want to be careful with stuff like that; in some cases the voltage will first blow through one layer of insulation and then blow through the other. Still it is worth a test. This kinda reminds me of a design by Thomas Rapp where the feedthrough was "hollow" (a tube exposed to air on the outside,...
by ian_krase
Fri Jul 27, 2018 5:19 am
Forum: New User Chat Area
Topic: Calculating Resistance for a Fusor
Replies: 1
Views: 178

Re: Calculating Resistance for a Fusor

First, a fusor (or any other DC plasma discharge including an electrical arc) has a nonlinear non-monotonic current-voltage response that makes the use of "resistance" fairly meaningless. We say that a gas discharge tube goes from "insulating" to "almost a dead short" when it ignites, but really it'...
by ian_krase
Fri Jul 27, 2018 5:08 am
Forum: Announcements and Site Administration Topics
Topic: Sunnyvale Mini Meetup -- August 11
Replies: 5
Views: 641

Re: Sunnyvale Mini Meetup -- August 11

Those who wish to go, let's gather at the side of the front door of the Frys at noon. I propose we go to have lunch at the nearby Panda Express.