LEXT: a lobster eye optic for Gamow

Kavli Affiliate: Marshall Bautz

| First 5 Authors: Charlotte Feldman, Paul O’Brien, Nicholas White, Wayne Baumgartner, Nicholas Thomas

| Summary:

The Lobster Eye X-ray Telescope (LEXT) is one of the payloads on-board the
Gamow Explorer, which will be proposed to the 2021 NASA Explorer MIDEX
opportunity. If approved, it will be launched in 2028, and is optimised to
identify high-z Gamma Ray Bursts (GRBs) and enable rapid follow-up. The LEXT is
a two module, CCD focal plane, large field of view telescope utilising Micro
Pore Optics (MPOs) over a bandpass of 0.2 – 5 keV. The geometry of the MPOs
comprises a square packed array of microscopic pores with a square
cross-section, arranged over a spherical surface with a radius of curvature of
600 mm, twice the focal length of the optic, 300 mm. Working in the photon
energy range 0.2 – 5 keV, the optimum L/d ratio (length of pore L and pore
width d) is 60, and is constant across the whole optic aperture. This paper
details the baseline design for the LEXT optic in order to full the science
goals of the Gamow mission. Extensive ray-trace analysis has been undertaken
and we present the development of the optic design along with the optimisation
of the field of view, effective area and focal length using this analysis.
Investigations as to the ideal MPO characteristics, e.g. coatings, pore size,
etc., and details of avenues for further study are also given.

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