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 (CO) 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 (KIDs). 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 (FWHM) 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 ensure low (<−40 dB) edge illumination of the primary to minimize spill onto warmer elements at the top of the dewar.
@article{arxiv.2012.10481,
title = {Optical Design of the EXperiment for Cryogenic Large-Aperture Intensity Mapping (EXCLAIM)},
author = {Thomas Essinger-Hileman and Danny Chmaytelli and Trevor Oxholm and Tatsat Parekh and Gage Siebert and Eric R. Switzer and Alyssa Barlis and Emily M. Barrentine and Jeffrey Beeman and Christine Chung and Paul Cursey and Sumit Dahal and Rahul Datta and Negar Ehsan and Jason Glenn and Joseph Golec and Andrew Lennon and Luke N. Lowe and Jeffrey McMahon and Maryam Rahmani and Peter Timbie and Bruce Tretheway and Carole Tucker and Carolyn Volpert and Joseph Watson and Edward J. Wollack},
journal= {arXiv preprint arXiv:2012.10481},
year = {2024}
}