The charge transfer efficiency of a CCD is based on the average level of signal lost per pixel over a number of transfers. This value can be used to directly compare the relative performances of different structures, increases in radiation damage or to quantify improvements in operating parameters. This number does not however give sufficient detail to mitigate for the actual signal loss/deference in either of the transfer directions that may be critical to measuring shapes to high accuracy, such as those required in astronomy applications (e.g. for Gaia's astrometry or the galaxy distortion measurements for Euclid) based in the radiation environment of space.Pocket-pumping is an established technique for finding the location and activation levels of traps; however, a number of parameters in the process can also be explored to identify the trap species and location to sub-pixel accuracy.This information can be used in two ways to increase the sensitivity of a camera. Firstly, the clocking process can be optimised for the time constant of the majority of traps in each of the transfer directions, reducing deferred charge during read out. Secondly, a correction algorithm can be developed and employed during the post-processing of individual frames to move most of any deferred signal back into the charge packet it originated from.Here we present the trap-pumping techniques used to optimise the charge transfer efficiency of p-and n-channel e2v CCD204s and describe the use of trap-pumped images for on-orbit calibration and ground based image correction algorithms.

Future NASA X-ray spectroscopy missions will require high throughput, high resolution grating spectrometers. Off-plane reflection gratings are capable of meeting the performance requirements needed to realize the scientific goals of these missions. We have identified a novel grating fabrication method that utilizes common lithographic and microfabrication techniques to produce the high fidelity groove profile necessary to achieve this performance. Application of this process has produced an initial pre-master that exhibits a radial (variable line spacing along the groove dimension), high density (>6000 grooves/mm), laminar profile. This pre-master has been tested for diffraction efficiency at the BESSY II synchrotron light facility and diffracts up to 55% of incident light into usable spectral orders. Furthermore, tests of spectral resolving power show that these gratings are capable of obtaining resolutions well above 1300 ($\lambda/\Delta\lambda$) with limitations due to the test apparatus, not the gratings. Obtaining these results has provided confidence that this fabrication process is capable of producing off-plane reflection gratings for the next generation of X-ray observatories.Comment: 17 pages, 10 figures, Submitted to Experimetal Astronom

Lynx is a concept under study for prioritization in the 2020 Astrophysics Decadal Survey. Providing orders of magnitude increase in sensitivity over Chandra, Lynx will examine the first black holes and their galaxies, map the large-scale structure and galactic halos, and shed new light on the environments of young stars and their planetary systems. In order to meet the Lynx science goals, the telescope consists of a high-angular resolution optical assembly complemented by an instrument suite that may include a High Definition X-ray Imager, X-ray Microcalorimeter and an X-ray Grating Spectrometer. The telescope is integrated onto the spacecraft to form a comprehensive observatory concept. Progress on the formulation of the Lynx telescope and observatory configuration is reported in this paper.

No abstract

Abstract-Electron Multiplying Charge-Coupled Devices (EMCCDs) are used in low-light-level (L3) applications for detecting optical, Ultra-Violet (UV) and Near Infra-Red (NIR) photons (10 nm to 1100 nm). The on-chip gain process is able to increase the detectability of any signal collected by the device through the multiplication of the signal before the output node, thus the effective read-out noise can be reduced to sub-electron levels, allowing the detection of single photons; however, this gain process introduces an additional noise component due to the stochastic nature of the multiplication. In optical applications this additional noise has been characterised. The broadening of the detected peak is described by the Excess Noise Factor. This factor tends to a value of √ 2 at high gain (>100x). In X-ray applications the situation is improved by the effect the Fano factor, f , has on the shot noise associated with X-ray photon detection (f ≈ 0.12 at X-ray energies). In this paper the effect of the detection of X-ray photons in silicon is assessed both analytically and through a Monte Carlo model of the gain amplification process. The Excess Noise on the signal is predicted (termed the Modified Fano Factor) for photon detection in an EM-CCD at X-ray energies. A hypothesis is made that the Modified Fano Factor should tend to 1.115 at high levels of gain (>10x). In order to validate the predictions made, measurements were taken using an 55 Fe source with Mn k-alpha X-ray energy of 5898 eV. These measurements allowed the hypothesis to be verified.