On the design of wide-field x-ray telescopes
X-ray telescopes having a relatively wide field-of-view and spatial resolution vs. polar off-axis angle curves much flatter than the parabolic dependence characteristic of Wolter I designs are of great interest for surveys of the X-ray sky and potentially for study of the Sun's X-ray emission. We discuss the various considerations affecting the design of such telescopes, including the possible use of polynomial mirror surface prescriptions, a method of optimizing the polynomial coefficients, scaling laws for mirror segment length vs. intersection radius, the loss of on-axis spatial resolution, and the positioning of focal plane detectors.
Mathematical Design Optimization of Wide-Field X-ray Telescopes: Mirror Nodal Positions and Detector Tilts
We describe a mathematical formalism for determining the mirror shell nodal positions and detector tilts that optimize the spatial resolution averaged over a field-of-view for a nested x-ray telescope, assuming known mirror segment surface prescriptions and known detector focal surface. The results are expressed in terms of ensemble averages over variable combinations of the ray positions and wave vectors in the flat focal plane intersecting the optical axis at the nominal on-axis focus, which can be determined by Monte-Carlo ray traces of the individual mirror shells. This work is part of our continuing efforts to provide analytical tools to aid in the design process for wide-field survey x-ray astronomy missions.
In-House Industrial Production of the Superconducting Conductor for the 43 T Hybrid Magnet of LNCMI-Grenoble
The hybrid magnet being built at LNCMI-Grenoble is based on the combination of resistive inserts, made up of Bitter and polyhelix coils, with a large bore superconducting outsert. It will produce, in the first step, an overall continuous magnetic field of 43 T in a 34 mm warm bore aperture. The superconducting coil will provide a nominal magnetic field of 8.5 T in a 1.1 m cold bore diameter. It relies on the novel development of an Nb-Ti/Cu Rutherford Cable On Conduit Conductor (RCOCC) cooled down to 1.8 K by a bath of superfluid helium pressurized at 1200 mbar. After a brief reminder of the specificity of hybrid magnets, namely the strong electromechanical coupling between resistive and superconducting coils, the main requirements of the RCOCC for efficient and reliable magnet operation are given. The test and validation phases prior to the industrial production of the RCOCC are reported, including the trial production of the ½ hard-drawn (H02 cold-worked) Cu-Ag 0.05% hollow stabilizer in continuous lengths of 325 m. The novelty of the RCOCC development concerns the assembly and the induction soft-soldering of the Rutherford cable on the Cu-Ag hollow stabilizer allowing a strict control of the interstrand contact resistance. Studies, developments, and the integration of the industrial production line at LNCMI-Grenoble are presented together with the result of the production of all RCOCC unit lengths.