DetectionoffaintX-rayspectralfeaturesusingwavelength,energy, andspatialdiscriminationtechniques

AbstractWe report here our methods and results of measurements of very low-signal X-ray spectra produced by highly charged ions in anelectron beam ion trap (EBIT). A megapixel Si charge-coupled device (CCD) camera was used in a direct-detection, single-photon-counting mode to image spectra with a cylindrically bent Ge(220) crystal spectrometer. The resulting wavelength-dispersed spectra werethen processed using several intrinsic features of CCD images and image-analysis techniques. We demonstrate the ability to clearly detectvery faint spectral features that are on the order of the noise due to cosmic-ray background signatures in our images. These techniquesremove extraneous signal due to muon tracks and other sources, and are coupled with the spectrometer wavelength dispersion andatomic-structure calculations of hydrogen-like Ti to identify the energy of a faint line that was not in evidence before applying themethods outlined here.r 2007 Elsevier B.V. All rights reserved. PACS: 32.30.Rj; 39.30.+w; 07.05.Kf; 07.85.!mKeywords: X-ray spectroscopy; Highly charged ions; CCD imaging; Crystal spectroscopy; Cosmic ray removal