At 9:16 AM 12/3/4, Jones Beene wrote: [snip] >Let me direct your attention to "Thallium online" >http://www.rxlist.com/cgi/generic/thallium.htm > >You will see that over 95% of the gammas in this situation >would have a mean energy between 68-80 KeV but are coming >from the transitory mercury isotope as the Tl life is so >short. After an extended run, and with such a small amount >used, and with a starting half-life of only 70+ hours, there >is almost no Tl left to measure at the end of the run.
OK, I see you were referring to the Hg gammas at 80 keV. Yes, these too have a good penetraing power and are readily discriminated from tritium betas. They too can be counted by ordinary geiger counters. Also, a 70 hour half-life is plenty good for a tracer for water drops. A test of whether a cell is vulnerable to water drop entrainment shouldn't take more than an hour. BTW, I see the referenced medical web site uses "KeV". The prefix "k" (small k) is the standard prefix for kilo-, even though "M" is the standard prefix for mega-. [snip] >...Anyway if lots of tritium was being >produced, a fair amount of the bremsstrahlung gamma photons >of about 3-6 keV would be seen. These gamms have almost no pentrating power in water. This is why organic solvents are used for liquid scintillation counting. The water is kept to a few percent in the counting vials. > >This "should be" easily discriminated from the Tl emission, >but not necessarily so - depending on the detector used and >how the results were interpreted. That is why I asked the >question. I think it would be nearly impossible to confuse tritium with either 201Tl or 201Hg. You don't even need a multi channel analyser. I think the important thing here is not to lose sight of the fact that Cirillo's and various other boil-off enthalpy data may be suspect due to the problem which P.J van Noorden so kindly pointed out. This is an important fact to consider when designing future boil-off experiments. Regards, Horace Heffner
