Algorithms for correcting geometric distortions in delay-line anodes

• Published in: Review of scientific instruments 2003-01, Vol.74 (1), p.38-46
• Main Authors: Wilkinson, Erik, Béland, Stéphane, Penton, Steven V., Vallerga, John V., McPhate, Jason B., Sahnow, David J.
• Format: Article
• Language: English
• ISSN: 0034-6748; 1089-7623
• DOI: 10.1063/1.1524715

Time-delay anodes are typically used in conjunction with microchannel plates to create photon counting, two-dimensional imaging detectors. The anode and associated electronics are used to compute the centroid of the charge cloud from the microchannel plate stack. The computation of event position is done in analog circuitry and then digitized to an appropriate number of bits. The analog nature of the time-delay anode makes it susceptible to a wide variety of outside influences resulting in variations in the correlation between physical space and the reported digital value. These variations, both local and global, must be corrected as part of the reduction of scientific data. If left uncorrected in spectral data, for example, these variations result in decreased spectral resolution, inaccurate wavelength identifications, and/or distorted spectral line profiles. This work presents successful algorithms for correcting the dominant distortions present in a time-delay anode. These algorithms were developed as part of the data reduction pipeline for the cosmic origins spectrograph (COS) far ultraviolet channel. COS is a fourth generation instrument for the Hubble Space Telescope.