The Instrument of the Imaging X-Ray Polarimetry Explorer
P. Soffitta, L. Baldini, R. Bellazzini, E. Costa, L. Latronico, Fabio Muleri, E. Del Monte, Sergio Fabiani, M. Minuti, Michele Pinchera, C. Sgró, G. Spandre, A. Trois, Fabrizio Amici, H. Andersson, Primo Attinà, Matteo Bachetti, M. Barbanera, Fabio Borotto, A. Brez, Daniele Brienza, Ciro Caporale, Claudia Cardelli, Rita Carpentiero, Simone Castellano, Marco Castronuovo, Luca Cavalli, E. Cavazzuti, Marco Ceccanti, Mauro Centrone, S. Ciprini, Saverio Citraro, Fabio D’Amico, Elisa D’Alba, Sergio Di Cosimo, Niccolò Di Lalla, Alessandro Di Marco, Giuseppe Di Persio, I. Donnarumma, Y. Evangelista, Riccardo Ferrazzoli, Asami Hayato, Takao Kitaguchi, Fabio La Monaca, Carlo Lefevre, Pasqualino Loffredo, Paolo Lorenzi, Leonardo Lucchesi, C. Magazzù, S. Maldera, Alberto Manfreda, Elio Mangraviti, Marco Marengo, G. Matt, Paolo Mereu, Alfredo Morbidini, Federico Mosti, Toshio Nakano, Hikmat Nasimi, Barbara Negri, S. Nenonen, Alessio Nuti, Leonardo Orsini, M. Perri, M. Pesce-Rollins, Raffaele Piazzolla, M. Pilia, A. Profeti, Simonetta Puccetti, John Rankin, Ajay Ratheesh, A. Rubini, Francesco Santoli, Paolo Sarra, Emanuele Scalise, Andrea Sciortino, Toru Tamagawa, Marcello Tardiola, Antonino Tobia, Marco Vimercati, Fei Xie
Abstract
While X-ray spectroscopy, timing, and imaging have improved much since 1962 when the first astronomical nonsolar source was discovered, especially wi the launch of the Newton/X-ray Multi-Mirror Mission, Rossi/X-ray Timing Explorer, and Chandra/Advanced X-ray Astrophysics Facility, the progress of X-ray polarimetry has been meager. This is in part due to the lack of sensitive polarization detectors, which in turn is a result of the fate of approved missions and because celestial X-ray sources appear less polarized than expected. Only one positive measurement has been available until now: the Orbiting Solar Observatory measured the polarization of the Crab Nebula in the 1970s. The advent of microelectronics techniques has allowed for designing a detector based on the photoelectric effect of gas in an energy range where the optics are efficient at focusing in X-rays. Here we describe the instrument, which is the major contribution of the Italian collaboration to the Small Explorer mission called IXPE, the Imaging X-ray Polarimetry Explorer, which will launch in late 2021. The instrument is composed of three detector units based on this technique and a detector service unit. Three mirror modules provided by Marshall Space Flight Center focus X-rays onto the detectors. We show the technological choices, their scientific motivation, and results from the calibration of the instrument. IXPE will perform imaging, timing, and energy-resolved polarimetry in the 2-8 keV energy band opening this window of X-ray astronomy to tens of celestial sources of almost all classes.