Three-Stage Cryocooler Cold Head for Advanced Heterodyne Sensors

Future advanced heterodyne sensors for submillimeter-wave receivers require 50 to 100 mW of cooling at 15 to 20 K for the sensor, and 1 to 2 W cooling at 80 to 120 K for the local oscillator, with size and input power suitable for use in a Small Sat. nbsp;During Phase I, a detailed cryocooler configuration trade study was completed, and the 3-stage pulse tube configuration driven by the Lockheed Martin (LM) Midi compressor was selected based on efficiency and adaptability. nbsp;An assessment of innovative regenerator materials and direct metal laser sintering (DMLS) additively-manufactured heat exchanger materials was completed, and the decision was made to include DMLS in the design, while keeping the advanced regenerator material as an option as a future improvement. nbsp;Cooling powers of 100 mW at 20 K and 2 W at 120 K were selected, with 47 W compressor ac power predicted. nbsp;A solid model of the 3-stage cold head was then generated in Phase I. nbsp;CU Aerospace (CUA) will use innovative materials and low cost cold head design and assembly, coupled with LMrsquo;s industry-leading multi-stage pulse tube expertise, to provide NASA with a compact, affordable cryocooler for submillimeter detectors. nbsp;Our team proposes to: 1) nbsp;Refine the 3-stage cold head solid model design initiated in Phase I, optimized to provide simultaneously 100 mW cooling at 20 K and 2 W cooling at 120 K, to improve manufacturability and decrease cost compared with heritage LM multi-stage cold heads. 2) nbsp;Procure all hardware necessary to assemble the 3-stage cold head, and the gas transfer line to connect it to a LM-owned Midi compressor. 3) nbsp;Assemble and weld 3-stage cryocooler cold head, perform proof pressure testing and leak testing. 4) nbsp;Integrate cold head with LM Midi compressor and perform cryocooler performance testing over a range of operating conditions, varying the input power, ambient temperature and 1st, 2nd and 3rd stage temperatures to fully characterize cryocooler performance.