LIGO Document T1500056-v5

Sketches showing views of the ETM/RM gap from chamber ports

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T - Technical notes
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This document shows annotated sketches of views of the gap between the Y End Test Mass (ETMy) and its Reaction Mass (RM), from various chamber ports. These sketches are motivated by the need to place the Test Mass Discharging System (TMDS) at the best port location for discharging electrostatic charge on the test mass.
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Notes and Changes:
v5 defines TMDS door port, clocking of custom 10' reducer, and TMDS orientation for the ETMx chamber.
v4 defines TMDS door port, clocking of custom 10' reducer, and TMDS orientation.
v3 includes pages 7 and 8 showing issue with ISC table and new solution.
v2 includes the same 5 pages from v1 as well as a page 6 which indicates the new location selected for the custom flange, LIGO-D1500065-v2.
v1 includes the original summary with options highlighted over 5 pages.

Drawings of the ETM chamber assemblies are posted at D0900506 (LBSC5, Top Level Chamber Assembly) and D0900471 (LBSC4, Top Level Chamber Assembly). With the pdf drawings one can get a good sense of the paths from the chamber ports to the gap between the End Test Mass (ETM) and the Reaction Mass (RM). These DCC entries also include eDrawings. eDrawings are 3D models that can be viewed, rotated, manipulated (parts made transparent or hidden, cross-sectional views created, etc.) and measured (if compiled with this option). The eDrawing is a free downloadable applciation from SolidWorks, available here:
However for top-level chamber assembly models (such as these two), the files are large and the computing required for the model manipulation might be more than most laptop computers can handle conveniently.

The pdf file of annotated sketches included here indicate the views (lines of sight) from the chamber ports to the gap between the ETMy and its RM. The best option seems to be C90G5 on the near (-X door). Port G2 on the chamber (behind the pier at 45 deg) may also be an option, although a 90 degree elbow will be required in the ionized gas flow path (which will cause a significant loss of delivery efficiency).

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