Validation of techniques to mitigate copper surface contamination in CUORE

Abstract

In this article we describe the background challenges for the CUORE experiment posed by surface contamination of inert detector materials such as copper, and present three techniques explored to mitigate these backgrounds. Using data from a dedicated test apparatus constructed to validate and compare these techniques we demonstrate that copper surface contamination levels better than 10 −7 -10 −8 Bq/cm 2 are achieved for 238 U and 232 Th. If these levels are reproduced in the final CUORE apparatus the projected 90% C.L. upper limit on the number of background counts in the region of interest is 0.02-0.03 counts/keV/kg/y depending on the adopted mitigation technique.

Validation of Parylene Coating to Suppress Alpha Contamination on the Copper Surface in CUORE Bolometers

“…CUORE bolometer modules are not able to distinguish an incident α particle from β/γ particles therefore a degraded α particle may mimic a 0νββ event in the ROI. This hypothesis was confirmed in a CUORE predecessor experiment and R&D bolometric tests [5,6]. In this article, we present a novel surface contamination suppression technique using conformal thin film coating with Parylene.…”

Search for Neutrinoless Double-Beta Decay ofTe130with CUORE-0

“…Technical details can be found in Refs. [11,12,[18][19][20]; we focus here on the first physics results from CUORE-0.…”

Neutrinoless Double Beta Decay with CUORE-0: Physics Results and Detector Performance

“…The array is cooled down to a temperature of ∼10-12 mK, using the same dilution refrigerator located in the Hall A of the Gran Sasso National Laboratory that already hosted the Cuoricino experiment [5,6] The CUORE-0 array is the first tower that has been realised using all the procedures that have been developed for the construction of the upcoming CUORE experiment. A tremendous effort was put in all the stages of the detector construction, starting from the selection of extremely pure raw materials, up to the cleaning techniques of the detector components [7] in order to mitigate any surface contaminations which can produce background in the region of interest due to degraded αs [5]. In addition, to reduce any possible surface re-contamination due to the exposure of the clean components to Rncontaminated air [8], special packaging techniques were developed for the storage of the clean detector components in a controlled atmosphere.…”