The Imaging X-ray Polarimetry Explorer (IXPE) will expand the information space for study of cosmic sources, by adding polarization to the properties (time, energy, and position) observed in x-ray astronomy. Selected in 2017 January as a NASA Astrophysics Small Explorer (SMEX) mission, IXPE will be launched into an equatorial orbit in 2021. The IXPE observatory includes three identical x-ray telescopes, each comprising a 4-m-focal-length (grazing-incidence) mirror module assembly (MMA) and a polarization-sensitive (imaging) detector unit (DU). The optical bench separating the MMAs from the DUs is a deployable boom with a tip/tilt/rotation stage for DU-to-MMA (gang) alignment, similar to the configuration used for the NuSTAR observatory. The IXPE mission will provide scientifically meaningful measurements of the x-ray polarization of a few dozen sources in the 2-8 keV band, over the first two years of the mission. For several bright, extended x-ray sources (pulsar wind nebulae, supernova remnants, and an active-galaxy jet), IXPE observations will produce polarization maps indicating the magnetic structure of the synchrotron emitting regions. For many bright pulsating x-ray sources (isolated pulsars, accreting x-ray pulsars, and magnetars), IXPE observations will produce phase-resolved profiles of the polarization degree and position angle.
We report on the first measure of the polarization of a laboratory source with a continuum energy spectrum, which simulates the effect of a real astrophysical source, carried out with a prototype of the Gas Pixel Detector (GPD). This detector is an X-ray polarimeter exploiting the photoelectric effect both to measure the polarization and to obtain the image of astrophysical sources. The gas pixel detector will be the focal plane detector on board the IXPE (Imaging X-ray Polarimetry Explorer) mission selected by NASA in the framework of the Explorer program for a launch in 2021.
IXPE scientific payload comprises of three telescopes, each composed of a mirror and a photoelectric polarimeter based on the Gas Pixel Detector design. The three focal plane detectors, together with the unit which interfaces them to the spacecraft, are named IXPE Instrument and they will be built and calibrated in Italy; in this proceeding, we will present how IXPE Instrument will be calibrated, both on-ground and in-flight. The Instrument Calibration Equipment is being finalized at INAF-IAPS in Rome (Italy) to produce both polarized and unpolarized radiation, with a precise knowledge of direction, position, energy and polarization state of the incident beam. In flight, a set of four calibration sources based on radioactive material and mounted on a filter and calibration wheel will allow for the periodic calibration of all of the three IXPE focal plane detectors independently. A highly polarized source and an unpolarized one will be used to monitor the response to polarization; the remaining two will be used to calibrate the gain through the entire lifetime of the mission.
The Gas Pixel Detector (GPD) is an X-ray polarimeter that exploits the photoelectric effect to measure the polarization and to obtain the image of astrophysical sources. This detector is on board the IXPE (Imaging X-ray Polarimetry Explorer) mission selected by NASA in the framework of the Explorer program scheduled for the launch in 2021. We report on tests carried out with a laboratory prototype of the GPD to verify the performance as a function of the temperature in a large temperature range between 15°C and 40°C.
XIPE, the X-ray Imaging Polarimetry Explorer, is a mission dedicated to X-ray Astronomy. At the time of
writing XIPE is in a competitive phase A as fourth medium size mission of ESA (M4). It promises to reopen the
polarimetry window in high energy Astrophysics after more than 4 decades thanks to a detector that efficiently
exploits the photoelectric effect and to X-ray optics with large effective area. XIPE uniqueness is time-spectrally-spatially-
resolved X-ray polarimetry as a breakthrough in high energy astrophysics and fundamental physics.
Indeed the payload consists of three Gas Pixel Detectors at the focus of three X-ray optics with a total effective
area larger than one XMM mirror but with a low weight. The payload is compatible with the fairing of the Vega
launcher. XIPE is designed as an observatory for X-ray astronomers with 75 % of the time dedicated to a Guest
Observer competitive program and it is organized as a consortium across Europe with main contributions from
Italy, Germany, Spain, United Kingdom, Poland, Sweden.