Majorana One-Tonne Cryostat Cooling Conceptual Feasibility Study

This report evaluates the conceptual plans for a one-tonne (S4) cryostat cooling design. This document is based upon previous design work and experimental results used to evaluate the current MAJORANA DEMONSTRATOR (MJD) thermal design. A feasibility study of a cooling system for S4 based on the MJD thermosyphon experiment is presented. The one-tonne experiment will be a scaled up version of the MJD. There will be many cryostats for the S4 experiment. In this document a cryostat with up to 19 strings of Germanium crystals is analyzed. Aside from an extra outer ring of crystals, the geometry of both systems cryostats is very similar. The materials used in the fabrication of both ultra-low background experiments will be underground electroformed copper. The current MJD uses a two-phase liquid-gas cooling system to ensure constant operating temperature. This document presents a theoretical investigation of a cooling system for the S4 experiment and evaluates the heat transfer performance requirements for such a system.