The Rainwater Memorial Calibration Facility for X-Ray Optics

Abstract

The Nuclear Spectroscopic Telescope ARray (NuSTAR) is a NASA Small Explorer mission that will carry the first focusing hard X-ray (5-80 keV) telescope to orbit. The ground calibration of the optics posed a challenge as the need to suppress finite source distance effects over the full optic and the energy range of interest were unique requirements not met by any existing facility. In this paper we present the requirements for the NuSTAR optics ground calibration, and how the Rainwater Memorial Calibration Facility, RaMCaF, is designed to meet the calibration requirements. The nearly 175 m long beamline sports a 48 cm diameter 5-100 keV X-ray beam and is capable of carrying out detailed studies of large diameter optic elements, such as the NuSTAR optics, as well as flat multilayer-coated Silicon wafers.

NuSTAR on-ground calibration: II. Effective area

“…The strength of the on-ground calibration data set, compared to in-orbit data, derives from these subgroup measurements, where only a small fraction of the optic is investigated, effectively improving the resolution of the ORM validation. Detailed accounts of the calibration approach and hardware are available from Brejnholt et al 2 , Brejnholt et al 3 and Koglin et al 9 .…”

“…The on-ground calibration of the two multilayer coated flight optics was carried out at the Rainwater Memorial Calibration Facility for X-ray optics (RaMCaF) 2,3 at Nevis Laboratories in New York. The multilayer coating was laid down at the Technical University of Denmark (DTU Space) 4 .…”

First results from the ground calibration of the NuSTAR flight optics

“…The Rainwater Memorial Calibration Facility (RaMCaF) is a 163 m long hard X-ray calibration facility, 16 which is conveniently located right next to the assembly room for the NuSTAR optics at Columbia's Nevis Laboratory. The Comet MXR-160 X-ray tube with tungsten target supplies the facility with X-rays up to 100 keV (see Figure 2 for the source spectrum).…”

Evaluation of the surface strength of glass plates shaped by hot slumping process

“…Such telescopes assembling will be based on a principle of hierarchical integration: single mirrors segments will be integrated into elemental modules, usually called X-ray Optical Unit (XOU), then assembled and aligned in the Flight Mirror Assembly (FMA) through intermediate azimuthal structures to reestablish the cylindrical symmetry of the nested telescope with Wolter I (or a Wolter I approximation) optical design [8]. The slumping technology has already been successfully employed for the production of NuSTAR telescope, launched in 2012 [9], [10], able to deliver an image quality at focus of 45 arcsec HEW [11]. Additional studies are currently on going both by American and European research groups to further expand the technology in terms of achievable optical quality (the goal being 5 arcsec HEW) [12], [13].…”