Overview of the Fiber System for the Dark Energy Spectroscopic Instrument
Claire Poppett, Luke Tyas, J. Aguilar, C. Bebek, David G. Bramall, T. Claybaugh, Jerry Edelstein, Parker Fagrelius, H. Heetderks, Patrick Jelinsky, Sharon R. Jelinsky, Robin Lafever, Andrew Lambert, M. Lampton, M. E. Levi, P. Martini, Constance M. Rockosi, J. Schmoll, R. M. Sharples, Martin M. Sirk, Edward Wishnow, Jiaxi Yu, S. P. Ahlen, A. Bault, S. BenZvi, D. Brooks, Shaun Cole, Axel de la Macorra, Arjun Dey, P. Doel, K. Fanning, Andreu Font-Ribera, J. E. Forero-Romero, E. Gaztañaga, Satya Gontcho A Gontcho, Alma X. González‐Morales, ChangHoon Hahn, Klaus Honscheid, Jorge Jiménez, S. Juneau, D. Kirkby, Anthony Kremin, Martin Landriau, L. Le Guillou, Marc Manera, Aaron Meisner, R. Miquel, John Moustakas, Eva-Maria Mueller, A. Muñoz-Gutiérrez, A. D. Myers, J. Nie, Gustavo Niz, N. Palanque‐Delabrouille, Will J. Percival, Francisco Prada, D. Rabinowitz, Mehdi Rezaie, Graziano Rossi, E. Sánchez, Edward F. Schlafly, David J. Schlegel, M. Schubnell, Hee‐Jong Seo, David Sprayberry, G. Tarlé, M. Vargas-Magaña, Benjamin Alan Weaver, Rongpu Zhou
Abstract
Abstract The Dark Energy Spectroscopic Instrument (DESI) is a revolutionary instrument designed for precise measurements of cosmic distances and the investigation of dark energy. DESI utilizes 5000 optical fibers to simultaneously measure the spectra of distant objects and aims to measure 40 million galaxies and quasars in a 5 yr survey. One of the critical challenges to DESI’s success was ensuring that the fiber system was not only highly efficient but also delivered a highly stable beam enabling more reliable sky subtraction for measurements of faint objects. We achieved this stability by minimizing the stress on the fiber system during the manufacture and operation of the telescope and fiber positioning robots. We installed the DESI fiber system on the 4 m Mayall telescope with ≥99% of fibers intact, and the instrument has delivered superb optical performance throughout the initial years of the DESI survey, including ≥90% average throughput when injected with a focal ratio of ∼ f /3.9 as delivered by the primary focus corrector, excluding fiber absorption losses. The design of DESI required multiple innovations to achieve these requirements, such as cleaved fibers bonded with a UV-curing epoxy to glass ferrules in the focal plane and fusion splicing instead of physical connectors. In this paper, we describe the development, delivery, and installation of the fiber system, the innovations that made the state-of-the-art performance possible, and the key lessons learned that could benefit future projects.