Interferometer, Cryogenic, Reflectors
Saturday, September 09, 2006
A Cryogenic Interferometer has been designed and developed consisting of two metal mesh Reflectors. The Reflectors are built into three plates in the configuration of a sandwich with the outer two plates suspended by three BeCu leaf springs. The springs are profiled to a segment of an annulus, attached to one of the plates and fixed to the moving plate. This configuration allows high compliance in the direction of motion, but high stiffness in the direction perpendicular to motion. Three moving coil actuators enabling control of the parallel motion of the two metal mesh Reflectors achieve the plate motion. The separation of the plates is monitored by three capacitance micrometer readouts. A closed-loop servo circuit provides a signal for plate positional control.
The Reflectors are made of nickel metal mesh, 3 μm thick, 6 μm wide, and a pitch of 15-19 μm. The mesh is stretched over a titanium alloy ring and permanently attached by thermal compression using a gold flux. The rings are attached to aluminum plates, which can provide additional stretching because of specially designed rims. This use of dissimilar material requires analytical characterization of the configuration, so that the tension remains intact (taut) at the cryogenic temperature (4K). The rims define the operating position of the meshes and requires a flatness of ~0.1 μm RMS. This is to minimize interferometer performance degradation. The rims, the micrometer pads, and all reference surfaces are diamond tip turned.
Source: “Cryogenic mechanisms for scanning and interchange of the Fabry-Perot interferometers in the ISO Long Wavelength Spectrometer”, 25th Aerospace Mechanisms Symposium, NASA Conference Publication 3113, JPL, May 8-10, 1991; G. R. Davis, I. Furniss, T. J. Patrick, R. C. Sidey, and W. A. Towlson (Davis and Patrick are both with Mullard Space Science Laboratory, University College London).
Reference: None Available
Industrial Products
posted by JD52 @ 1:39 PM,
