TITLE: Preparation of sub-ppm to ppt level K, U, Th analytical standards and reference materials using a deep underground ultra low background counting facility
Auth1: PILLALAMARRI ILA * PILA@MIT.EDU
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PREPARATION OF SUB-PPM TO PPT LEVEL K, U, TH ANALYTICAL STANDARDS AND REFERENCE MATERIALS USING A DEEP UNDERGROUND ULTRA LOW BACKGROUND COUNTING FACILITY Abstract: Ultra trace level determination of U and Th is important for fields such as deep underground high energy physics experiments, environmental sciences, geosciences, microelectronic fabrication and Homeland Security. Analytical standards for K, U and Th with concentrations from sub-ppm to ppt and even femto level are required to determine the K, U and Th concentrations accurately and precisely. Currently, standard reference materials with trace level U and Th are available at ppm to ppb level only. K in standard reference materials is usually above ppb level. So preparation of standards at ppt level is proposed for K, U and Th concentrations. These standards would be calibrated by using radiometric gamma spectroscopy of the low background counting facility located deep underground. The major challenges expected are 1) the availability of high pure and radiopure materials for the preparation of the standards, 2) extreme radiopurity demand on the determination of ultra trace level K, U and Th of the detection media, containment and segmentation materials, the detection and readout hardware, the structural support, and the shielding of the gamma spectrometer, 3) ultra low level background for the gamma counting facility. But once these major hurdles are overcome, it is expected to be quite feasible to prepare synthetic and naturally occurring materials as ppt standards. An outline of the project : • material selection for the preparation of the standards, • preparation of the K, U, Th standards in the range sub-ppm to ppt, • gamma background counting without any source in the low background, counting facility (LBCF) located deep underground • assessment of radon background of LBCF, • photon and neutron flux measurement of LBCF, • gamma measurement of the K, U, Th standards, • Finalize the standards by repeat analyses and calibration.