## Measuring Ion Energies with Neutrons

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.
Steven Sesselmann
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Real name: Steven Sesselmann
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### Measuring Ion Energies with Neutrons

Hi Guys,

I learnt something new today..., one can measure ion temperature in pulsed D+D fusion by measuring the neutrons.

Apparently that is what they do at Lawrensville (LPPX), by measuring the arrival time of the neutrons from each pulse, they can determine the ion temperature inside the plasma.

Neutrons from the D+D reaction are monoenergetic, which means that they are always produced with the same energy 2.45 mev. however within the plasma ions are moving in all directions, so some are moving towards the detector and others are moving away from the detector, therefore when they fire a shot, some neutrons arrive early and some arrive late, and by looking at the width of the bell curve, it is possible to deduce the plasma temperature.

The neutron velocity varies with the square root of the energy...

E = mv^2

v = sqrt(e/m)

...assume M = 1

sqrt(2,400,000 ev)
------------------------ = + or - % of Neutron velocity.
sqrt(ion energy)

The neutron velocity can be measured by knowing the time of the shot and the distance from the experiment to the detector.

Steven
http://www.gammaspectacular.com - Gamma Spectrometry Systems
https://www.researchgate.net/profile/Steven_Sesselmann - Various papers and patents on RG

Starfire
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### Re: Measuring Ion Energies with Neutrons

Interesting Steven - thanks

Steven Sesselmann
Posts: 2111
Joined: Thu Aug 11, 2005 1:50 am
Real name: Steven Sesselmann
Location: Sydney - Australia
Contact:

### Re: Measuring Ion Energies with Neutrons

http://www.gammaspectacular.com - Gamma Spectrometry Systems
https://www.researchgate.net/profile/Steven_Sesselmann - Various papers and patents on RG