In this phase, we are working toward improving our setup with a rigid copper bar, and obtaining a new data point for our radiative cooling thermal models for a suspended silicon mass. Since the past cooling runs of a silicon test mass did not yet incorporate aquadag-painted shields, we wanted to obtain a new data point in the model (in other words, we painted the shields in QIL/2645, but the next test was a PD measurement, so this is the first silicon test mass measurment after shields were painted). The improvement to the thermal linkage, now using a rigid copper bar with higher conductivity (ref. QIL/2666), is a second variable being changed simultaneously in the spirit of improving the cooldown time.
Refer to the prior post (QIL/2694) for the bulk of the blow-by-blow of configuring the chamber to use the rigid copper bar linkage. This post will describe the mounting of the Si mass, and the pump down and cool down.
- The silicon mass with Aquadag barrel was dropped into the existing frame, with the previous wire arrangement and with no particular requirement on position or orientation (just best effort centering and leveling). Adjustments were done chamberside as access was easier.
- The frame was lifted into the chamber, with the hanging mass supported by auxiliary fingers, and placed in an available area. Since conductive cooling was not a dominant mode of heat transfer in this setup (ref. QIL/2647), clamping to the baseplate was simply a single dog clamp on each foot of the frame.
- The cigarette paper was cryovarnished to the surface in the bare central position. Once the cryovarnish was set, the RTD was cryovarnished to the cigarette paper pad. No strain relief or thermal anchoring considerations were implemented. RTD continuity was verified.
- Lids were bolted down and shields were finalized (avoiding shorting to copper bar, making sure foil drapes covering apertures were well positioned, etc.
- Vacuum pumps on at ~3 pm, cryocooler on at 3:30 pm. At 4 pm, things are still looking good!
Closeout photos will be posted to the QIL Cryo Vacuum Chamber photo album. |