Modular stray light mitigation
Stray light in a metering structure is controlled by surrounding with a rigid shield an elongated length of a strut and supporting on the rigid shield a surface finish which is highly absorptive of light. The strut is thermally decoupled from the rigid shield using a plurality of insulating web layers comprising a multi-layer insulation (MLI) system disposed between the strut and the rigid shield. The MLI in such scenarios (1) thermally isolates the strut from the shield (2) serves as a support structure to support the rigid shield on the strut, and (3) absorbs thermally induced mechanical stresses as between the rigid shield and the strut.
1. A method for mitigating stray light in an optical metering system, comprising:
disposing a plurality of web layers of a multi-layer insulation (MLI) system around an elongated length of a strut of an optical metering system to form an insulated strut assembly, wherein the MLI system is configured to control transfer of thermal energy;
securing the MLI system to the strut using a plurality of first fasteners;
enclosing the insulated strut assembly along the elongated length with a shield formed of a semi-rigid material and having a shield length that is coextensive with the elongated length;
securing the shield to the MLI system using a plurality of second fasteners; and
providing the shield with a surface finish that is highly absorptive of electromagnetic radiation in the optical spectrum and disposed on an exterior surface of the shield along the shield length.
2. The method of claim 1 , further comprising selecting the plurality of first fasteners to be a first fastener type from the group consisting of an adhesive, a clip, a double sided tape, and a touch fastener.
3. The method of claim 2 , further comprising selecting the plurality of second fasteners to be a second fastener type from the group consisting of an adhesive, a clip, a double sided tape, and a touch fastener.
4. The method of claim 3 , further comprising selecting the first fasteners and the second fasteners type to be of the same fastener type.
5. The method of claim 1 , further comprising disposing the plurality of web layers of the MLI system coextensive with the shield length.
6. The method of claim 1 , further comprising selecting a cross-sectional profile shape of the shield to be a different shape as compared to a cross-sectional profile shape of the strut.
7. The method of claim 4 , further comprising selecting the cross-sectional profile shape of the shield to facilitate a reduced amount of reflected stray electromagnetic radiation in the optical spectrum as compared to the cross-sectional profile shape of the strut.
8. The method of claim 1 , further comprising distributing the plurality of first fasteners at a plurality of spaced apart locations along the elongated length of the strut.
9. The method of claim 1 , further comprising when the shield is enclosing the strut, using one or more of the first fasteners, the second fasteners, and the MLI to facilitate an allowable dynamic dimensional variation of the strut relative to the shield caused by a coefficient of thermal expansion (CTE) mismatch as between the shield and the strut.
10. The method of claim 1 , further comprising absorbing in one or more of the first fasteners, the second fasteners, and the MLI mechanical stresses caused by a dynamic dimensional variation of the shield relative to the strut.
11. The method of claim 1 , wherein the shield is comprised of a tubular member having a slit extending along the shield length between two opposing shield wall edges, and the method further comprises separating the opposing shield wall edges along the slit to form a gap.
12. The method of claim 11 , further comprising positioning the shield around the strut by passing the strut through the gap and then closing the gap.
13. The method of claim 12 , further comprising at least a third fastener configured to secure a first one of the shield wall edges to a second one of the shield wall edges opposed from the first shield wall edge to maintain the gap in a closed state.
14. The method of claim 1 , wherein the shield is comprised of a tubular member formed of a plurality of shield members which divide the shield along the shield length, and the method further comprises enclosing the strut along the shield length by positioning at least a first one of the shield members along a first side of the strut, positioning at least a second one of the shield members along a second side of the strut, and securing the first one of the shield members to at least the second of the shield members.
15. The method of claim 1 , further comprising forming the surface finish as a coating comprised of carbon nanotubes.
16. The method of claim 1 , further comprising providing a surface structure on an outer surface of the shield which is configured to reduce reflections of stray electromagnetic radiation in the optical spectrum.