AMS measurements of 26Al in quartz to assess the cosmic ray background for the geochemical solar neutrino experiment LOREX

LORandite EXperiment (LOREX) plans to measure the time integrated solar neutrino flux of the last few million years via the product of the reaction ²⁰⁵Tl(υ_e,e^-)²⁰⁵Pb in lorandite of the Allchar mine in Macedonia. Utilizing this reaction is only possible if the background of ²⁰⁵Pb produced by the interaction of secondary cosmic ray particles and particles originating from the natural radioactivity within the rock mineral itself is substantially lower than the expected signal from neutrino interactions. Low abundance of cosmic ray induced ²⁰⁵Pb implies good shielding of the mine by the overlying rock. For the assessment of this background fraction it is necessary to acquire information about the past erosion activity at this site. In the present study the erosion rates have been estimated via cosmogenic ²⁶Al produced in situ in quartz of surface rock materials of the Allchar site. Details of the first determinations of in situ produced ²⁶Al with the AMS method at VERA are described, and a rough estimate of the erosion rates at the Allchar site is given.