Well, all is well here with the return and NIST tracable absolute calibration of my Eberline PNC-1.
I now have a rigid anchor point for not only future calculations, but a base for giving my other counters a crude check and calibration. (a real no-no in th' biz, but I did use the word crude).
They did note that my old ranges were set low and I estimate that in my old system when I read 100cpm on the meter I was actually producing about 148 cpm, based on their recorded corrections.
The PNC-1 came back with a rating of .009mrem/cpm and with all the cross checks from the four data sheets with reported ranges and check points.
Remember 1mrem/hr represents a flux of ~8n/sq.cm/s for fusion neuts (RPG curve based on normalized ratemeter moderation of the BF3 tube.)
I know that 110 events/minute on my meter, (For fast neuts in the range 1-5mev), will equal 1mr/hr. This is nicely in agreement with the measured 230 events per minute on my meter from their 1.4X10e7 n/s, Am241-Be source at 288cm (2mrem). All absolute count data they warrant to only 10%! So there will always be that slop in any measurement or MORE depending on the amount of data manipulation/massaging and additional assumptions attendant to the effort.
I try and fix my meter's tube axis at 30cm from the fusor as a norm. With this distance I can now state with a new found confidence that for fusion neuts @2.45mev I am isotropically emitting 815 neutrons per second for each event or count/minute on my meter. thus for 100 cpm on my meter the fusor is kickin' out 81,500 n/s (isotropic).
I have, for very short moments, in the past, kicked the meter up to 300 cpm (that would be more now that they adjusted the range pots and that would mean that I probably have hit over 300,000 n/s for bursts! My heaviest steady (>60sec) run was about 140cpm as the lowest reading. This would have been about 160,000n/s steady and reliable.
I will have to go home and run the fusor to a new reading now with the calibration well established.
This puts the whole effort here on a much firmer grounding and my numbers will carry a NIST traceable cachet from this point on.
The total was $70.00, plus 14.00 shipping. (a bargain)
Richard Hull
Created on Tuesday, May 01, 2001 5:10 PM EDT by Richard Hull