Sashank Karri with Tom Shutt

System for Radon Assay of Water

Observations such as galaxy rotation curves, orbital motions of galaxy clusters, and gravitational lensing in the light of Newton’s law of gravity and general relativity overwhelmingly suggest that much of the matter in the universe is invisible.  This dark matter is theorized to be a massive particle that interacts with regular baryonic matter via only the gravitational and weak force (WIMP).  Due to the nature of the weak force, the probability (should I use cross section?) of a WIMP interacting with baryonic particle is very small, making the search for this particle a challenging experiment.  Furthermore, WIMP detector sensitivities to smaller cross sections of WIMP events are limited by the background in the detector.  The LUX Dark Matter Experiment addresses these challenges by creating a large volume detector, which increases the fiducial volume and thus increasing the probability of a wimp interacting in the detector.   Another method to increase the fiducial volume, water shielding, is used to reduce background events such cosmic rays, hot neutrons, gamma rays, and other radioactive events from reaching the detector.  Unfortunately, water can be a source of radiation, since it usually has some concentration of radon.  Thus steps are taken to purify water this radon.  After this, it is necessary to determine the remaining concentration of radon in the water in order to assess the background.  I will be constructing a new system for the radon assay of water in the framework of the LUX Dark Matter experiment.  The technique is based on separating radon from the water using a hydrophobic membrane stripping technology and subsequently after purification concentrating it in a carbon trap before sweeping it into an emanation chamber that counts the alpha decays.  The target sensitivity for this system is 1 mBq/m3.