Design and implementation of optics for the experiment for cryogenic large-aperture intensity mapping (EXCLAIM)

Thomas Essinger-Hileman; Danny Chmaytelli; Trevor Oxholm; Tatsat Parekh; Gage Siebert; Eric R Switzer; Joseph Watson; Alyssa Barlis; Emily M Barrentine; Jeffrey Beeman; Christine Chung; Paul Cursey; Sumit Dahal; Rahul Datta; Negar Ehsan; Jason Glenn; Joseph Golec; Andrew Lennon; Luke N Lowe; Jeffrey McMahon; Maryam Rahmani; Peter Timbie; Bruce Tretheway; Carole Tucker; Carolyn Volpert; Edward J Wollack

doi:10.1063/5.0246814

Design and implementation of optics for the experiment for cryogenic large-aperture intensity mapping (EXCLAIM)

Rev Sci Instrum. 2025 Jan 1;96(1):014503. doi: 10.1063/5.0246814.

Authors

Thomas Essinger-Hileman¹, Danny Chmaytelli², Trevor Oxholm³, Tatsat Parekh¹, Gage Siebert⁴, Eric R Switzer¹, Joseph Watson¹, Alyssa Barlis¹, Emily M Barrentine¹, Jeffrey Beeman⁵, Christine Chung⁶, Paul Cursey¹, Sumit Dahal¹, Rahul Datta⁷, Negar Ehsan¹, Jason Glenn¹, Joseph Golec⁸, Andrew Lennon⁶, Luke N Lowe¹, Jeffrey McMahon⁷, Maryam Rahmani¹, Peter Timbie³, Bruce Tretheway⁶, Carole Tucker⁹, Carolyn Volpert¹⁰, Edward J Wollack¹

Affiliations

¹ NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA.
² University of California, Los Angeles, Los Angeles, California 90095, USA.
³ University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
⁴ Arizona State University, Tempe, Arizona 85281, USA.
⁵ Lawrence Berkeley National Lab, Berkeley, California 94720, USA.
⁶ Applied Physics Laboratory, The Johns Hopkins University, Laurel, Maryland 20723, USA.
⁷ University of Chicago, Chicago, Illinois 60637, USA.
⁸ University of Massachusetts Amherst, Amherst, Massachusetts 01003, USA.
⁹ Cardiff University, Cardiff CF10 3AT, United Kingdom.
¹⁰ University of Maryland, College Park, Maryland 20742, USA.

PMID: 39807964
DOI: 10.1063/5.0246814

Abstract

This work describes the design and implementation of optics for EXCLAIM, the EXperiment for Cryogenic Large-Aperture Intensity Mapping. EXCLAIM is a balloon-borne telescope that will measure integrated line emission from carbon monoxide at redshifts z < 1 and ionized carbon ([CII]) at redshifts z = 2.5 - 3.5 to probe star formation over cosmic time in cross-correlation with galaxy redshift surveys. The EXCLAIM instrument is designed to observe at frequencies of 420-540 GHz using six microfabricated silicon integrated spectrometers with spectral resolving power R = 512 coupled to kinetic inductance detectors. A completely cryogenic telescope cooled to a temperature below 5 K provides low-background observations between narrow atmospheric lines in the stratosphere. Off-axis reflective optics use a 90-cm primary mirror to provide 4.2' full-width at half-maximum resolution at the center of the EXCLAIM band over a field of view of 22.5'. Illumination of the 1.7 K cold stop combined with blackened baffling at multiple places in the optical system ensures low (<-40 dB) edge illumination of the primary to minimize spill onto warmer elements at the top of the dewar.

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