The Off-Plane Grating Rocket Experiment (OGRE) will flight-test high-precision X-ray technology in a three-component spectrometer comprised of a Wolter-I telescope, X-ray reflection gratings and electron-multiplying charge-coupled devices (EM-CCDs). OGRE will demonstrate cutting-edge X-ray mirrors known as monocrystalline silicon optics which are planned for use on several proposed X-ray Probe missions, and fly X-ray reflection gratings that after our recent characterization campaign, indicate high-precision spectral resolution. This X-ray technology serves as a great candidate for space-based X-ray astronomy as we move towards a Lynxlike flagship mission, and OGRE will be the first mission to test such gratings and optics in space. However, mono-crystalline silicon optics are still in development, while the gratings and electronics section of OGRE will be ready for a flight-test in the immediate future. In the interim, it is proposed that OGRE achieves a pathfinder flight which incorporates the Joint European Telescope for X-ray astronomy (JET-X) as a substitute optic, establishing an initial flight for the gratings and electronics on board. A pathfinder flight will reduce risk and gain insight for a full OGRE launch which will fly mono-crystalline silicon optics for the first time. Through an extensive characterization campaign for JET-X, the mono-crystalline silicon optics, EM-CCDs and a reflection grating, we have measured the performance of the OGRE spectrometer for its pathfinder flight. We confirm the continued ability of the JET-X optic, and that both the OGRE and Pathfinder OGRE spectrometers are capable of meeting the science requirement of R > 1500. Additionally, we motivate that with more detailed analysis, even higher spectral resolutions could be possible, alongside a result for the resolution of the grating itself.
The Off-plane Grating Rocket Experiment (OGRE) is a sounding rocket mission which aims to raise the technology readiness levels of three new technologies for soft X-ray astronomy, as well as produce the highest resolution spectrum of Capella yet. This paper focusses on the focal plane camera of the telescope which employs four electron-multiplying CCDs – three for spectral observations and one for imaging observations. The camera and its detectors will switch between two different operating modes during the observation window to maximise the scientific return of the mission, all while transmitting live telemetry and a limited amount of imagery data to the ground in real time. The energy resolution of the detectors has been modelled across the intended operational energy range to confirm whether diffraction orders can be separated, and the dependency of the multiplication gain on voltage and temperature has been characterised for each detector.
Electron Multiplying Charge Coupled Devices, EMCCD are used as x-ray detectors. The NSLS-II Soft Inelastic x- ray Scattering (SIX) beam line uses two EMCCDs for x-ray detection. Electrons drift and diffuse from generation point toward pixel gates and are collected there. The diffused electrons form a charge cloud distributed over several neighboring pixels. This charge sharing enables coordinate measurements with accuracy better than the pixel pitch. The charge distribution shape has to be taken into account to achieve ultimate accuracy in coordinate measurements. In this paper, we present a method of the charge distribution shape analysis and demonstrate its applications. The number of electrons collected under a pixel is proportional to the shape function integral. These electron packets get transferred to the sense node of the output amplifier. The transfer process could introduce distortions to the original charge distribution. For example, during transfers, electrons in the packet could be exposed to traps if they are present in the sensor. The trapping and later the release processes distort the apparent shape of the charge distribution. Therefore, deviations of the charge distribution shape from the originally symmetrical form can indicate the presence of trap centers in the sensor and can be used for sensor diagnostics.
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