Wow guys! I just beat Joe Zambelli's record of 140K+ n/s! I spent 4 hours just conditioning the fusor III last evening. I nursed the D2 bleed against a highly throttled back vac valve, for over 2 hours, making micro adjustments of current vs. voltage, with the shell tmeperature hitting 235 deg C. I set my calibrated Eberline PNC-1 exactly 25cm from the poissor position. I took an 18 minute background reading of 12 counts (1count/90seconds).
For the next two hours, I listened to the count, subjectively, as voltage and pressure were jockeyed. I was like a spider monkey twidling and twirling, adjusting and fidgeting until I hit the ultra sweet spot. The meter on the Eberline was hovering at a rather smooth 110-150 events/minute. I started a 2 minute count average run while in this sweet spot and the average was 134 events/minute.
I shut the thing down about 1AM this morning and took another 18 minute background count and got 7 counts over the period.
This amounts to about 0.75 count knocked off of the 134 cpm reading. Lets play devil's advocate and drop it to 130 cpm I like to round down to be somewhat conservative and keep round figures.
Now this particular meter shows, by calibration, to read 39 counts/mrem/hr. (Eberline tech's said 40-60cpm/mrem/hr depending on age of tube.) Mine is ancient so that probably explains the diff. Let's say 40cpm/mrem/hr for my PNC-1.
The standard inverse RPG curve for 2.45 mev neutrons, (look up in Eberline's data charts), shows that for this moderator (parafin) 8n/sqcm/s flux represents 1 mrem/hr of neutron flux.
So, 130 cpm /40 = 3.25 mrem
3.25mrem X 8n/sqcm/s = 26n/sqcm/s of flux at the detector.
Sphere at r=25cm contain 4 pi r x r or 7853 sqcm area.
7850sqcm x 26n/sqcm/s means an idealized isotropic emission of 204,100 n/s!
The meter read higher than this at times too!
I have never had a fusor behave as nicely and as smootly as fusor III did last night. (no pulsing at all!) Perhaps it was the TLC I poured into it coupled with the fine new super sealed feedthru.
I do know the old Wifo was pissed that I ignored her all evening and my excitement over the neutron run did little to mollify her either. It looks like I am in th' dog house and must wine and dine her tonight. She sometimes jokingly refers to herself as a fusion widow.
Anyway, the best average pressure was 8 microns and 32.4kv applied at 5-7ma. Tantalum grid running white hot!!
Richard Hull
Created on Wednesday, April 11, 2001 10:17 AM EDT by Richard Hull Last Modified on Thursday, April 19, 2001 11:22 PM EDT by Richard Hull