Well, as promised, I did some activation experiments with iodine. First I had to get enough to be useful, and luckily the Chemistry Department was willing to make a donation of some very old and raunchy periodic acid (HIO4). This stuff is a wicked strong oxidizer, smells bad, is extremely acidic, poorly soluble--I am sure that a nice big target of crysal iodine would be much better all around. As can be seen however, the periodic acid did activate. The listed value for the iodine peak is 441 keV. I had to cut down on conversion gain in order to get this reasonably strong peak. Four hours later, the activity was all but gone and I decided to subtract a background spectrum then. I-127 has a thermal neut cross section of some 6.5 barns, is 100% abundant, has lots of strong resonances, and the resultant nuclide I-128 is short-lived (T1/2 = 27 min) and emits the gamma in about 14% of decays. As suspected, iodine turns out to be a viable activation material near fusors.
Richard, sounds like you are nicely equipped with that 4" scintillation head! With such a big crystal, I'll bet you could easily see the short-lived aluminum activation peak that is still eluding me (Jon, I haven't given up on it yet!). Sorry that Fusor IV is not still up and running, but your head-on duo-linac will probably be churning out neutrons soon enough. Sometimes a big step forward requires a little step back, but I'm sure the fruits of that effort will pay off nicely in due time.
More experiments are on the way...
-Carl
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2003-02-21 22:49 Iodine Activation 
(Carl Willis) [Latest: 2003-02-24 11:46]