Operating Parameters for Corona Neutron Counters

[Richard Hester]

I love paper abstracts that give away important details. A case in point is the one cited here :http://iopscience.iop.org/0950-7671/39/3/309 . The paper describes operating a boron-lined counter tube in corona mode, and gives away a couple of important details, including the load resistor (100M), and the shaping time (2 usec). One could use this data to try out one of the SNM-9 boron-lined corona counter tubes that appear relatively available (and relatively cheap) on E-pay and other sites.

I had a notion that the resistor driving one of these tubes would have to be pretty big to limit the current properly and sense the change induced by a neutron event, but this paper nails things nicely. I may use the data to check out my corona tube.

A little 4 AM sweat time and a change in Google search parameters hit some gold.

Here's a direct citation for the SNM-9 tube, confirming that it is indeed a boron-line corona counter tube: http://www.osti.gov/energycitations/pro ... id=4172060 .

[Carl Willis]

Here's the entire Tivendale paper on corona counters, one of the few non-Russian technical mentions of the concept. Maybe the full text will have some more nuggets of wisdom for you as you work on getting the tube usefully operational.

-Carl

[Richard Hester]

Thanks for that - it looks like one of the seminal English language papers on the subject. The other Russian paper cited gives a lot of dirty details about the SNM-9 operation.

I have a couple of big HDPE cylinders I can use as moderator for my He3 corona tube. One of my recent charge sensitive amplifiers would be useful for output conditioning.

[Doug Coulter]

Well, we got some CHM-14 tubes on ebay, and now I've tested one. They work pretty well, about as you'd expect for their size and right on the numbers their data sheets recommend. In other words, pretty numb, but great for something so small and so cheap -- far better deal than a BTI.

We also got some bigger B10's and 3He's from the same source, I'll be testing those too real soon.

To not waste space here, there's a thread on my forums that discusses these, which is active and will be added to as results come in for the other tube types.

http://www.coultersmithing.com/forums/v ... 2074#p2074

Shows the lashup and some scope waveforms.

http://www.coultersmithing.com/forums/v ... f=11&t=348

Shows moderator construction details.

http://www.coultersmithing.com/forums/v ... f=19&t=338

Is the discussion about finding and buying the tubes.

Enjoy -- these seem to work fairly well, not like a super duper 3He two feet long (which is my reference standard) or even the old Ge B10 tube which is huge by comparison, but for someone starting out -- they work, they're realtime (unlike BTI) and they're at least a lot more sensitive than a bubble detector. We'll be posting more operational details and preamp design for these fairly soon.
(and thanks to Carl for finding the basic paper that de-mystified these for us)

[DaveC]

Carl - thanks for posting the paper. It's an interesting read.


Dave Cooper

[afuentes]

Does anybody know if the Russian CHM-14 Tube has
cathode lined with the enriched Boron-10 or with
natural boron (both isotopes B-11 80% and B-10 ~ 19% ) ?

[Chris Bradley]

All the odd pieces of written material I have seen on these refers to them as 'B-10' tubes (rather than 'Boron' tubes).

[Richard Hester]

It really doesn't matter that much either way, as the tube is already specified for what's pasted inside, whether it's B10-enriched or natural boron.

[afuentes]

True, the tube specs are the specs regardless of the Boron Isotope used, but
it does matter if you are going to play with it in different ways, or use it as a source of
B-10 enriched plate to be used in other detector configurations.
Interestingly, the LND, Inc Boron-lined cylinder detectors of about
the same size have the same Neutron Sensitivity of the Russian CHM-14 (SNM-14) of 1 nv cps
using B-10 Enrichment of 96%. So very likely (but not 100% sure) these
Russian made tubes may have also some degree of Boron-10 enrichment.

[Doug Coulter]

FWIW, I tend to like the B-10 lined tubes over the BF3 ones. Something about being able to use a better "counter gas" in the lined ones than BF3 turns out to be. Sensitivity isn't really much different in the samples I have, but in general, I can get larger signals out of the lined ones than the pure gas ones.

Pretty sure they are all enriched, at least all the ones I've seen.