Bob,
Isn’t the reality check that eliminating a cosmic ray contribution means the expected gamma counts are going to be too low to impress anyone? However, I am very glad you are going to the trouble – if you also test for radiation (all types) with and without the enclosure, and then compare the two. Without both, the benefits of a cave alone are small. BTW - a PNNL study I ran across says that the best material to shield against cosmic-ray components is iron, which has the best combination of primary shielding and minimal secondary neutron production. As you are using iron with lead – that is good. A compromise is the simple expedient to test the ongoing reaction as you plan but also with no shielding. If bare gives significantly more counts, then you have made the right choice to shield. However, it is likely that a bare test will show fewer, not more. That is especially true if the reaction itself is making muons. And didn’t Mark mention having a second meter anyway? Perfect. IMO - the most important finding which could come out of this is to see significantly more gammas in the cave than with no shielding - and to see a variance from inverse square when the cave is moved back from the reactor. If a radiation burst was to be correlated with apparent endotherm, as in the last test – it would be a significant indication that Holmlid is correct. From: Bob Higgins Do you have a reference on this? Otherwise, a lead cave would not be useful - it is there to protect the sensor from the cosmic rays. My understanding is that the cosmic rays produce the neutrons by spallation. If the neutrons are absorbed in the lead, they will likely cause isotopic shift which will lead to beta emission and then characteristic x-rays for lead at 78 keV. My plan is to follow the inside of the lead with 1/4" of Fe which will absorb all of the 78 keV but will produce the characteristic x-ray of Fe at 6 keV. Then there is the boric acid neutron absorber, and then the aluminum absorbs the 6 keV from the Fe, but gives off 1.5 keV Al characteristic x-ray in small amount. On Sun, Feb 28, 2016 at 7:58 PM, Jones Beene <[email protected]> wrote: From: Bob Higgins Ø Jones, the moral of the story is that the large amount of lead (and it probably took a whole lot for the HPGe detector) converted some of the cosmic rays into a small neutron flux. Bob, as the thesis clearly states – the neutrons then are absorbed by the lead, causing the gamma radiation.
