Snowmass White Paper Coordination Workshop - Shared screen with speaker view
Thomas Tsang
On the radioacitivity of Kr, years ago we (BNL) made dark count rate measurement of VUV sensitive SiPMs in purified LAr, LKr, and LXe. A significantly higher DCR was observed in LKr than LAr or LXe, about a factor of 100. So LKr do glow (at 155 nm) more than LAr (128 nm). We speculated that it was due to the natural Kr-85 radioactivity (687 keV) remained in the Earth’s atmosphere after dissolving of nuclear fuel for military and civilian purposes in the past decades.
Kate Scholberg
thanks, Thomas
Kate Scholberg
I thought the Kr-85 rate in natural krypton was very much higher than Ar-39 in natural Ar, but seems that is not so. Low level glow is indeed probably not a major problem for TeV scale events
Milind Diwan
We should certainly make the measurement in Krypton again.
Kate Scholberg
I guess both Kr-81 and Kr-85 are present
Milind Diwan
I think Krypton 81 contributes also.
Milind Diwan
We would have to study how to trigger. There is no reason to trigger below ~few hundred MeV. Even this is debatable since the low trigger is driven by dark matter scattering.