The Instrument of the Imaging X-ray Polarimetry Explorer

Abstract

While X-ray Spectroscopy, Timing and Imaging have improved verymuch since 1962, when the first astronomical non-solar source was discovered, especially with the launch of 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, in part due to the fate of approved missions and in part because the celestial X-ray sources appeared less polarized than expected. Only one positive measurement has been available until now. Indeed the eight Orbiting Solar Observatory measured the polarization of the Crab nebula in the 70s. The advent of techniques of microelectronics allowed for designing a detector based on the photoelectric effect in gas in an energy range where the optics are efficient in focusing X-rays. Herewe describe the Instrument, which is the major contribution of the Italian collaboration to the SmallExplorer mission called IXPE, the Imaging X-ray Polarimetry Explorer, which will be flown 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. In the following we will show the technological choices, their scientific motivation and the 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.

arXiv comment25 pages, 12 figures, 5 tables (accepted for publication in Astronomical Journal)

References in corpus (17)

• An efficient photoelectric X-ray Polarimeter for the study of Black Holes and Neutron Stars
• Analyzing the Data from X-ray Polarimeters with Stokes Parameters
• Design, Construction, and Test of the Gas Pixel Detectors for the IXPE Mission
• A Sealed Gas Pixel Detector for X-ray Astronomy
• XIPE: the X-ray Imaging Polarimetry Explorer
• Direct reading of charge multipliers with a self-triggering CMOS analog chip with 105k pixels at 50 micron pitch
• Re-detection and a Possible Time Variation of Soft X-ray Polarisation from the Crab
• Development of Thick-foil and Fine-pitch GEMs with a Laser Etching Technique
• In-flight calibration system of Imaging X-ray Polarimetry Explorer
• Spectral and polarimetric characterization of the Gas Pixel Detector filled with dimethyl ether
• Low energy polarization sensitivity of the Gas Pixel Detector
• The imaging properties of the Gas Pixel Detector as a focal plane polarimeter
• Astronomical x-ray polarimetry based on photoelectric effect with microgap detectors
• Measurement of the position resolution of the Gas Pixel Detector
• A Study of background for IXPE
• Measuring x-ray polarization in the presence of systematic effects: Known background
• A versatile facility for the calibration of X-ray polarimeters with polarized and unpolarized controlled beams

Cited by in corpus (2)

• Polarized Blazar X-rays imply particle acceleration in shocks
• Vela pulsar wind nebula x-rays are polarized to near the synchrotron limit