Arcus: the soft x-ray grating explorer

Abstract

Arcus provides high-resolution soft X-ray spectroscopy in the 12-50 Å bandpass with unprecedented sensitivity, including spectral resolution > 2500 and effective area > 250 cm 2. The three top science goals for Arcus are (1) to measure the effects of structure formation imprinted upon the hot baryons that are predicted to lie in extended halos around galaxies, (2) to trace the propagation of outflowing mass, energy, and momentum from the vicinity of the black hole to extragalactic scales as a measure of their feedback, and (3) to explore how stars form and evolve. Arcus uses the same 12 m focal length grazing-incidence Silicon Pore X-ray Optics (SPOs) that ESA has developed for the Athena mission; the focal length is achieved on orbit via an extendable optical bench. The focused X-rays from these optics are diffracted by high-efficiency Critical-Angle Transmission (CAT) gratings, and the results are imaged with flight-proven CCD detectors and electronics. Combined with the high-heritage NGIS LEOStar-2 spacecraft and launched into 4:1 lunar resonant orbit, Arcus provides high sensitivity and high efficiency observing of a wide range of astrophysical sources.

SPO mirror plate production and coating

“…The plate manufacturing process begins with double-sided polished 300 mm wafers, and ends with diced, ribbed, wedged, and coated SPO plates which can be subsequently stacked to form an optical unit [1,2]. SPO stacks are currently fabricated using a combination of established semiconductor fabrication techniques and novel fabrication techniques specifically designed for ESA's Athena mission and NASA's ARCUS candidate mission [6][7][8]10]. The scientific requirements for Athena specify an angular resolution of five arc-seconds Half-Energy Width (HEW), and an energy-dependent effective area of up to 1.5 m 2 [3][4][5].…”