He-3 Detector Operational and Background

This area is for discussions involving any fusion related radiation metrology issues. Neutrons are the key signature of fusion, but other radiations are of interest to the amateur fusioneer as well.
Post Reply
ericstroud
Posts: 26
Joined: Wed Nov 29, 2006 3:33 pm
Real name: Dr. Eric M. Stroud
Location: Northern NJ
Contact:

He-3 Detector Operational and Background

Post by ericstroud » Sat Nov 08, 2008 12:17 am

Hi Everyone-

I was able to get my He-3 detector up and running, and some background counts were made.

The Hardware
****************
Reuter-Stokes 3He tube P4-0820-103, from Don Orie, www.oetech.com
Tennelec TC175 preamplifier, from Don Orie
NIM Bertran 345 bias supply, +1700vDC
NIM Ortec 452 Spectroscopy amp, 20x coarse gain, 3uS shaping
NIM Tennelec TC246 windowed for gammas (not windowed in photo)
Ortec 5500 Multichannel Analyzer

I also use a Ludlum 2200 scalar/ratemeter windowed for gammas - which involves a lot less space, adjustment, and cables than the above! I highly recommend this portable device!

Background Check Data
***************************
All samples were 60 minutes at 1,107 feet above sea level on 07Nov2008:

Unmoderated tube: 10cpm (605 cts)
Polyethylene sleeve on tube: 10cpm (623 cts)
Paraffin moderator in acrylic: 9cpm (562 cts)
1/8" lead sheet around tube: 8cpm (509 cts)

Kindest regards,
Eric
Attachments
320_He3setup.JPG
320_He3setup.JPG (38.29 KiB) Viewed 1344 times

User avatar
Richard Hull
Moderator
Posts: 11969
Joined: Fri Jun 15, 2001 1:44 pm
Real name: Richard Hull

Re: He-3 Detector Operational and Background

Post by Richard Hull » Mon Nov 10, 2008 4:01 pm

This data sounds good. How long is the tube?

I like to hold an intense gamma source near the tube and set the level detect to well above the gamma level "grass".

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

ericstroud
Posts: 26
Joined: Wed Nov 29, 2006 3:33 pm
Real name: Dr. Eric M. Stroud
Location: Northern NJ
Contact:

He-3 Detector Operational and Background

Post by ericstroud » Mon Nov 10, 2008 4:35 pm

Hi Richard-

This is the usual 22" tube from Don Orie. Timing was good, as I think he is currently sold out!
As you suggested, I will put a small gamma source before the next run.

Kind regards, Eric

User avatar
Richard Hull
Moderator
Posts: 11969
Joined: Fri Jun 15, 2001 1:44 pm
Real name: Richard Hull

Re: He-3 Detector Operational and Background

Post by Richard Hull » Mon Nov 10, 2008 7:30 pm

A large Gamma source should make virtually no difference in the count if the discriminator is set correctly.

My He3 counter tube is also 22" long. I get between 4 and 7 CPM taken over a period of10 minutes. This has been as high as 25cpm during the great November CME of a couple of years back. Solar activity definitely affects background. That is why I do a 10 min background both before and after a fusor run. Background subtraction is not really all that important anymore with 3000-4000cpm being the norm for a moderate fusor run.

When I re-vamp my area for fusor IV I hope to have the He3 counter a good bit farther back.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

Post Reply