Advancements in Cryogenic Technology for EXCLAIM Telescope

The EXperiment for Cryogenic Large-Aperture Intensity Mapping (EXCLAIM) is a balloon-borne telescope aimed at surveying star formation across cosmological time scales, particularly within the frequency range of 420 to 540 GHz. A recent paper by Sumit Dahal and 69 co-authors details the design and testing of a superfluid-tight cryogenic receiver integral to the EXCLAIM project. This receiver is cooled to approximately 1.7 K using a superfluid helium bath, which is essential for achieving high sensitivity in dark atmospheric windows.

The receiver features six on-chip spectrometers equipped with kinetic inductance detectors (KIDs) that enhance its sensitivity and allow for rapid integration. Key components of the receiver include a superfluid-tight shell, a meta-material anti-reflection coated silicon window, magnetic shielding, and a sub-Kelvin cooling system. The cooling system employs a three-stage continuous adiabatic demagnetization refrigerator (CADR) to maintain the detectors at 100 mK, while a $^4$He sorption cooler provides a thermal intercept at 900 mK for mechanical suspensions and coaxial cables.

The paper also reports on the flight-like testing of major receiver components, including the superfluid-tight receiver window and the sub-Kelvin coolers. The advancements in cryogenic technology and receiver design are expected to significantly enhance the capabilities of the EXCLAIM telescope, allowing for more detailed studies of star formation and the evolution of the universe.

For further details, the full paper can be accessed at arXiv:2409.02847.