Search found 708 matches

by Andrew Seltzman
Sun Jul 08, 2018 9:50 pm
Forum: Fusor Construction & Operation (& FAQs)
Topic: Mark3 operation 3e-4 torr / quad ion source @ -40kV, 1mA-9mA
Replies: 142
Views: 42833

Re: Mark3 operation and upgrades

A recent upgrade to the mark 3 has replaced the 6 way conflat cube with an 8 way kimball physics vacuum hexagon. The hexagon is considerably smaller and more compact, and has 2 more ports then the cube. The hexagon is connected to the core with a brazed ceramic isolator with copper conflat o-rings, ...
by Andrew Seltzman
Thu Jul 05, 2018 11:12 pm
Forum: Books & References
Topic: Answer keys w/ explanation?
Replies: 19
Views: 3566

Re: Answer keys w/ explanation?

This is the rutherford scattering problem: http://hyperphysics.phy-astr.gsu.edu/hbase/Nuclear/elescat.html It means assume the atom is free space except for the nucleus which is solid sphere. Calculate the radius of the nucleii and thus the area each nucleii is blocking. Find how thick a foil is req...
by Andrew Seltzman
Sat Jun 02, 2018 1:08 pm
Forum: High Voltage - Fusor Input Power (& FAQs)
Topic: Spellman DXM70N600X3547 power supplies on ebay -70kV 8.56MA
Replies: 157
Views: 35614

Re: Spellman DXM70N600X3547 power supplies on ebay -70kV 8.56MA

I don't see an attached plot, could you upload the plot and the text output printed to the matlab terminal?

It sounds like one of the interlocks is tripped, do you have the proper pins jumpered on the 15pin connector?

The java applet is really old and dosen't work on current OS.
by Andrew Seltzman
Wed May 23, 2018 9:49 pm
Forum: Fusor Construction & Operation (& FAQs)
Topic: TIG welding tubing and flanges with an automated fixture
Replies: 8
Views: 3231

Re: TIG welding tubing and flanges with an automated fixture

The chuck is capable of continuous rotation, the wire on the jaw connects to the chuck body so weld current dosen't flow through the jaw ways or scroll. The current then flows down the drawbar (a 1/4-20 bolt) which is insulated from the gearbox so current doesn't flow through the worm gear or bearin...
by Andrew Seltzman
Wed May 23, 2018 12:43 pm
Forum: Fusor Construction & Operation (& FAQs)
Topic: TIG welding tubing and flanges with an automated fixture
Replies: 8
Views: 3231

TIG welding tubing and flanges with an automated fixture

I have recently built a welding lathe for automated tube welding for an upgrade to my fusor. The lathe holds a TIG torch at a fixed distance from the tube or flange and rotates the part at a constant speed. A current path is provided through the chuck drawbar which is insulated from the gearbox. The...
by Andrew Seltzman
Sun May 20, 2018 10:45 pm
Forum: Images du Jour
Topic: Sharing hamfest booty images
Replies: 27
Views: 7235

Re: Sharing hamfest booty images

Today's (May 20) turnout MIT Flea Market was much bigger than last months, with easily 4x the number of sellers. There were tables all the way up to the top of the parking garage. I got a 22" new in box LCD display for $60 and two 1sccm mass flow controllers for $10 ea. My haul 32952163_101028544775...
by Andrew Seltzman
Tue May 08, 2018 12:36 pm
Forum: Neutrons, Radiation, and Detection (& FAQs)
Topic: Second pulse from He3 tube
Replies: 5
Views: 1744

Re: Second pulse from He3 tube

In this case I don't think termination or ringing of a cable is the issue; a 650us delay would equate to a 400000ft long RG58 cable (5 ns/m (1.54ns/ft) delay).
by Andrew Seltzman
Sun Apr 15, 2018 5:04 pm
Forum: Images du Jour
Topic: Sharing hamfest booty images
Replies: 27
Views: 7235

Re: Sharing hamfest booty images

I was just over there are the M.I.T. Flea Market as well, yes, it had pretty slim pickings. It probably has a bigger turn out in the summer.
by Andrew Seltzman
Mon Apr 02, 2018 12:55 am
Forum: New User Chat Area
Topic: Thermocouple Gauges VS Vacuum Gauges
Replies: 7
Views: 2512

Re: Thermocouple Gauges VS Vacuum Gauges

I'd recommend an MKS 901p, it's a combination piezo/pirani gauge that will function between atmospheric and 1e-5torr