LEXT: a lobster eye optic for Gamow

TL;DR

The paper presents the design and optimization of the LEXT lobster eye optic for the Gamow Explorer, aiming to detect high-redshift Gamma Ray Bursts with a large field of view and effective area in the 0.2-5 keV range.

Contribution

It introduces a detailed baseline design of the LEXT lobster eye optic, including ray-trace analysis and optimization for the Gamow mission's science goals.

Findings

Optimized the field of view, effective area, and focal length of the LEXT optic.

Developed a ray-trace based design process for lobster eye optics.

Identified key MPO characteristics for improved X-ray focusing.

Abstract

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.