FAQ - Activation Materials - Overview

[Richard Hull]

Neutron activation is the ultimate proof that one is doing d-d fusion and is proportional to just how much fusion is being done. Nothing the amateur can do with a fusor, except fusion, will result in radioactivation of materials. Activation is one superb step better than a bubble detector as proof of fusion in a noisy electrical environment.

Fusors, in amateur hands, perform at many different levels based on the purse, skills, designs and self-imposed limitations of the fusioneer, operator/owner.

There is no recorded lower limit for detectable neutron activation established here as such efforts are mostly limited by the sensitive detection gear required for very low level activation recording.

The purpose of this series of FAQs is to suggest and recommend various materials for amateur activation efforts using the fusor, but much of this also applies to activation with any neutron source.

Fusors are constructed to greater and lesser levels of robustness. The activation time is limited in weaker systems and selecting the ideal, easy, or even a challenging activation material is an effort that is complex and involves many questions that the fusioneer must answer. Among the most important questions are the following:

1. What is the absolute maximum neutron number I can easily run?
2. How long can I sustain this level without a catastrophe?
3. How close to the fusor can I place a fairly beefy, heavy and cumbersome moderator block?
4. What kind of instruments do I have to detect activation?
5. How close to the statistical noise do I want to go if I have a weak fusor and still claim activation?

These are questions that each individual must answer and this series will, hopefully delineate the various strengths and weaknesses found in various activation materials so that the fusioneer seeking to do activation work will know which materials are best for his or her fusor at its current level of operation.

As a general rule, and with a broad brush stroke, one should not attempt activation that would be expected to yield easy results using a fusor producing much less than 100,000 n/s isotropic. Likewise, one can activate virtually all the materials pressented here if their fusor is capable of producing in excess of 700,000 n/s isotropic.

Shielding for personal safety or remote operation is often demanded at levels over 500,000 n/s isotropic, especially on longer activation runs. See past posted radiation safety and shielding FAQs related to fusor operation.

I hope that everyone finds the material in these related FAQs informative.

Richard Hull