Design of a broadband soft x-ray polarimeter

Herman L. Marshall; Hans Moritz Günther; Ralf K. Heilmann; Norbert S. Schulz; Mark D. Egan; Tim Hellickson; Sarah N. Trowbridge Heine; David L. Windt; Eric M. Gullikson; Brian Ramsey; Gianpiero Tagliaferri; Giovanni Pareschi

doi:10.1117/1.JATIS.4.1.011005

6 April 2018 Design of a broadband soft x-ray polarimeter

Herman L. Marshall, Hans Moritz Günther, Ralf K. Heilmann, Norbert S. Schulz, Mark D. Egan, Tim Hellickson, Sarah N. Trowbridge Heine, David L. Windt, Eric M. Gullikson, Brian Ramsey, Gianpiero Tagliaferri, Giovanni Pareschi

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Journal of Astronomical Telescopes, Instruments, and Systems, Vol. 4, Issue 1, 011005 (April 2018). https://doi.org/10.1117/1.JATIS.4.1.011005

Abstract

We describe an optical design and possible implementation of a broadband soft x-ray polarimeter. Our arrangement of gratings is designed optimally for the purpose of polarimetry with broadband focusing optics by matching the dispersion of the spectrometer channels to laterally graded multilayers (LGMLs). The system can achieve polarization modulation factors over 90%. We implement this design using a single optical system by dividing the entrance aperture into six sectors; high efficiency, blazed gratings from opposite sectors are oriented to disperse to a common LGML forming three channels covering the wavelength range from 35 to 75 Å (165 to 350 eV). The grating dispersions and LGML position angles for each channel are 120 deg to each other. CCD detectors then measure the intensities of the dispersed spectra after reflection and polarizing by the LGMLs, giving the three Stokes parameters needed to determine a source’s linear polarization fraction and orientation. The design can be extended to higher energies as LGMLs are developed further. We describe examples of the potential scientific return from instruments based on this design.

CC BY: © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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Herman L. Marshall, Hans Moritz Günther, Ralf K. Heilmann, Norbert S. Schulz, Mark D. Egan, Tim Hellickson, Sarah N. Trowbridge Heine, David L. Windt, Eric M. Gullikson, Brian Ramsey, Gianpiero Tagliaferri, and Giovanni Pareschi "Design of a broadband soft x-ray polarimeter," Journal of Astronomical Telescopes, Instruments, and Systems 4(1), 011005 (6 April 2018). https://doi.org/10.1117/1.JATIS.4.1.011005

Received: 24 November 2017; Accepted: 12 March 2018; Published: 6 April 2018

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