Characterizing Non-linearities in the Chandra LETG+HRC-S Dispersion Relation

摘要

The Chandra Low Energy Transmission Grating Spectrometer (LETGS) is comprised of 3 micro-channel plate (MCP) segments and is primarily used with the High Resolution Camera spectroscopic array (HRC-S). In-flight calibration data observed with the LETG+HRC-S show that there are non-linear deviations in the positions of some lines by as much as 0.1 A. These deviations are thought to be caused by spatial non-linearities in the imaging characteristics of the HRC-S detector. Here, we present the methods we used to characterize the non-linearities of the dispersion relation across the central plate of the HRC-S, and empirical corrections which greatly reduce the observed non-linearities by a factor of 2 or more on the central MCP.