1. Proposal to put 232 Th Source in  K for > 2MeV Gamma  Detection Bobby Lanza May 1, 2008 Neutron Meeting

2. The case for 232 Th Why are  ’ s with E > 2MeV important? –Muons interacting with the bedrock at Soudan create photons at this energy scale. –Source of background. What can  K do? –  ’ s above the 2MeV threshold can impart enough energy to electrons to make them Cherenkov radiate in  K. – Calibration with a test source would inform possible future tests at Soudan.

3. Why 232 Th instead of the Depleted Uranium we have? – DU has many sticking points in its decay chain (long lived daughters), before the high energy gammas. – DU chemically purified approx. 30 years ago, so not in equilibrium yet. Sticking Points > 2MeV  ’s

4. – 232 Th Approx. 10-15 yrs old (longer than combined daughter half-lives), so likely in equilibrium. – Above threshold gammas available from 208 Tl --> 208 Pb decay. 2.6 MeV  ’s

5. We have a 232 Th Source 0.1g of 232 Th in liquid solution. 400 decays per second expected. Standard calibration source.

6. Near Future (Proposed) Design simple containment vessel for 232 Th & install in  K. Take data with liquid 232 Th source. Do Monte Carlo & compare to data.

7. --Thanks--