QUBIC III: Laboratory characterization
Authors: Torchinsky S.A. , Hamilton J.-Ch. , Piat M. , Battistelli E.S. , de Bernardis P. , Chapron C. , D'Alessandro G. , De Petris M. , Gamboa Lerena M.M. , González M. , Grandsire L. , Marnieros S. , Masi S. , Mennella A. , Mousset L. , Murphy J.D. , O'Sullivan C. , Prêle D. , Stankowiak G. , Tartari A. , Thermeau J.-P. , Voisin F. , Zannoni M. , Ade P. , Alberro J.G. , Almela A. , Amico G. , Arnaldi L.H. , Auguste D. , Aumont J. , Azzoni S. , Banfi S. , Baù A. , Bélier B. , Bennett D. , Bergé L. , Bernard J.-Ph. , Bersanelli M. , Bigot-Sazy M.-A. , Bonaparte J. , Bonis J. , Bunn E. , Burke D. , Buzi D. , Cavaliere F. , Chanial P. , Charlassier R. , Cobos Cerutti A.C. , Columbro F. , Coppolecchia A. , De Gasperis G. , De Leo M. , Dheilly S. , Duca C. , Dumoulin L. , Etchegoyen A. , Fasciszewski A. , Ferreyro L.P. , Fracchia D. , Franceschet C. , Ganga K.M. , García B. , García Redondo M.E. , Gaspard M. , Gayer D. , Gervasi M. , Giard M. , Gilles V. , Giraud-Heraud Y. , Gómez Berisso M. , Gradziel M. , Hampel M.R. , Harari D. , Henrot-Versillé S. , Incardona F. , Jules E. , Kaplan J. , Kristukat C. , Lamagna L. , Loucatos S. , Louis T. , Maffei B. , Marty W. , Mattei A. , May A. , McCulloch M. , Mele L. , Melo D. , Montier L. , Mundo L.M. , Murphy J.A. , Nati F. , Olivieri E. , Oriol C. , Paiella A. , Pajot F. , Passerini A. , Pastoriza H. , Pelosi A. , Perbost C. , Perciballi M. , Pezzotta F. , Piacentini F. , Piccirillo L. , Pisano G. , Platino M. , Polenta G. , Puddu R. , Rambaud D. , Rasztocky E. , Ringegni P. , Romero G.E. , Salum J.M. , Schillaci A. , Scóccola C.G. , Scully S. , Spinelli S. , Stolpovskiy M. , Supanitsky A.D. , Timbie P. , Tomasi M. , Tucker C. , Tucker G. , Viganò D. , Vittorio N. , Wicek F. , Wright M. , Zullo A. 
Published: April 2022

We report on an extensive test campaign of a prototype version of the
QUBIC (Q & U Bolometric Interferometer for Cosmology) instrument,
carried out at Astroparticle Physics and Cosmology (APC) in
Paris. Exploiting the novel concept called bolometric interferometry,
QUBIC is designed to measure the CMB polarization at 150 and 220 GHz
from a high altitude site at Alto Chorillo, Argentina. The prototype
model called QUBIC Technological Demonstrator (QUBIC-TD) operates in a
single frequency band (150 GHz) and with a reduced number of
baselines, but it contains all the elements of the QUBIC instrument in
its final configuration. The test campaign included measurements of
the synthesized beam and of the polarization performance, as well as a
verification of the interference fringe pattern. A modulated,
frequency-tunable millimetre-wave source was placed in the telescope
far-field and was used to simulate a point source. The QUBIC-TD field
of view was scanned across the source to produce beam maps. Our
measurements confirm the frequency-dependent behaviour of the beam
profile, which gives QUBIC the possibility to do spectral imaging. The
measured polarization performance indicates a cross-polarization
leakage less than 0.6%. We also successfully tested the polarization
modulation system, which is provided by a rotating half wave
plate. We demonstrate the full mapmaking pipeline using data
from this measurement campaign, effectively giving an end-to-end
checkout of the entire QUBIC system, including all hardware
subsystems, their interfaces, and the software to operate the whole
system and run the analysis. Our results confirm the viability of
bolometric interferometry for measurements of the CMB polarization.