Search found 937 matches

by Rich Feldman
Wed Mar 13, 2019 4:52 am
Forum: New User Chat Area
Topic: Demo Fusor troubleshooting
Replies: 3
Views: 790

Re: Demo Fusor troubleshooting

Mixture of right and wrong advice in previous responses. Having too high a pressure (which you do) means the arc or glow discharge takes all the current your NST can give, without the secondary voltage getting very high, even with full primary voltage. But that has nothing to do with "tripping the s...
by Rich Feldman
Sun Mar 10, 2019 8:11 pm
Forum: Neutrons, Radiation, and Detection (& FAQs)
Topic: Making a SHV connector
Replies: 1
Views: 556

Making a SHV connector

Would be nice to have a SHV connector on the end of a cable today. They aren't super expensive to get by mail, even brand new, for example from Field Components. shv_fieldcomponents.JPG . Impatient and itching to fabricate something, I undertook to make one out of BNC connector parts on hand. DSCN11...
by Rich Feldman
Wed Mar 06, 2019 7:05 am
Forum: Neutrons, Radiation, and Detection (& FAQs)
Topic: A semi-DIY preamplifier for radiation detectors
Replies: 16
Views: 1834

Re: A semi-DIY preamplifier for radiation detectors

Broke down & got me an Ortec 459 Bias Supply ($75) and a powered NIM bin to put it in ($33). Picked 'em up this morning, and in a quick test this evening both appear to work. Except +/- 6V power at the bin slot I checked, but the 459 doesn't use that. The turns-counting dial on voltage setting pot h...
by Rich Feldman
Fri Mar 01, 2019 8:08 pm
Forum: Announcements and Site Administration Topics
Topic: Straw Poll / Proposal for San Francisco Area mini-meetup
Replies: 33
Views: 3786

Re: Straw Poll / Proposal for San Francisco Area mini-meetup

Flea market season is almost upon us. Opens Saturday, March 9, at Fry's in Sunnyvale. https://www.electronicsfleamarket.com/
I'll join Ian in inviting readers to meet for lunch after the show.
p.s. Who wants NST's, variacs, vacuum hose, graphite plates, or old oscilloscopes?
by Rich Feldman
Tue Feb 26, 2019 7:34 pm
Forum: Neutrons, Radiation, and Detection (& FAQs)
Topic: A semi-DIY preamplifier for radiation detectors
Replies: 16
Views: 1834

Re: A semi-DIY preamplifier for radiation detectors

We agree that ramping HV bias up or down is good practice. Richard and John, how slow is your slow? Designer at Cremat just agreed with me that ramping slow enough for preamp to stay linear is unnecessarily conservative. I tried it while watching scope, not quite pegging CR-110 output. Took about a ...
by Rich Feldman
Mon Feb 25, 2019 3:47 am
Forum: Neutrons, Radiation, and Detection (& FAQs)
Topic: A semi-DIY preamplifier for radiation detectors
Replies: 16
Views: 1834

Re: A semi-DIY preamplifier for radiation detectors

Thanks, Dan. Here's a question for all, about turning HV bias on or off. The cited manual from Fastcomtec says "Increase or decrease the high voltage only at a very slow rate. Observe output during bias voltage change with an oscilloscope. Do not allow the output to saturate during change of high vo...
by Rich Feldman
Wed Feb 20, 2019 9:52 pm
Forum: Neutrons, Radiation, and Detection (& FAQs)
Topic: A semi-DIY preamplifier for radiation detectors
Replies: 16
Views: 1834

Re: A semi-DIY preamplifier for radiation detectors

Thank you, Harald. I don't have meaningful risetime measurements yet. The CR-100 is supposed to have an impulse response like: csp1.JPG with risetime of about 7 ns and decay time constant of about 140 us (you could work it out from the test mode waveform picture). I think it's common for CSP's to be...
by Rich Feldman
Mon Feb 18, 2019 7:43 am
Forum: Neutrons, Radiation, and Detection (& FAQs)
Topic: A semi-DIY preamplifier for radiation detectors
Replies: 16
Views: 1834

Re: A semi-DIY preamplifier for radiation detectors

Well said, Jerry. I could probably find one or two, perhaps a laser power supply module, in one of many HV junk boxes in the garage. Or swap the transformer in a cheap low-voltage regulated DC power supply, with flyback topology, like we find in appliance controller boards these days. The primitive ...
by Rich Feldman
Sun Feb 17, 2019 8:03 pm
Forum: Neutrons, Radiation, and Detection (& FAQs)
Topic: A semi-DIY preamplifier for radiation detectors
Replies: 16
Views: 1834

Re: A semi-DIY preamplifier for radiation detectors

Progress report. 1. Sparking was solved by removing the R's and C's in bias circuit, so perf-board metal could be cleared in a wide margin on both sides. With the R's back in place, circuit sustained 4500 V for 5 minutes with no spark or series-NE2-lamp visible glow in the dark. Then with both high ...
by Rich Feldman
Sun Feb 17, 2019 3:18 am
Forum: Images du Jour
Topic: Joe Gayo's Fusor - Neutron Detection Upgrade
Replies: 29
Views: 3371

Re: Joe Gayo's Fusor - Neutron Detection Upgrade

Nice. Please say more about how you set up the axial magnetic field -- or point to an earlier post if you already told the story. Permanent magnets? Steel yoke?