Descriptions of Pictures of XRS Adiabatic Demagnetization Refrigerator (ADR)

This page has descriptions of the photograph and cutaway drawing of the XRS Adiabatic Demagnetization Refrigerator (ADR). The main use of this page is for those who are not viewing the pages with graphics. However, others who want a better understanding of what's in the pictures might find the page useful.

This page has 3 sections:

• Description of the Cutaway Drawing
• Description of the Photograph
• Brief list of the parts labelled in the Drawing and Photo comparison

Description of Cutaway Drawing

This is a cutaway drawing of the Adiabatic Demagnetization Refrigerator (ADR) designed for the X-Ray Spectrometer (XRS). This picture does not show the magnet that is part of the ADR. Instead, it only shows the part that is slipped into the hole in the center of the magnet coil.

I'll start the description with the heart of the ADR, the Salt Pill.

• Salt PIll. In this ADR, the salt pill is a cylinder, drawn as a rectangle. Part of pill is shown with its outer covering on (stainless steel in the final version.) Parallel lines run the length of the pill's interior, representing the wires in the salt pill which ensure good end-to-end thermal contact.
• Suspension. The salt pill is supported by a suspension system of Kevlar lines which hold the salt pill rigidly in place while thermally isolating the salt pill from the surrounding apparatus. The Kevlar fibers are shown as lines stretching from the ends of the salt pill to the surrounding framework. The lines are attached at each end to bolts, so they can be tightened. In the middle of one end, the heat switch is attached to the salt pill.
• Heat Switch. The body of the heat switch is a cylinder, drawn as a rectangle. The outer shell of the heat switch, shown on part of the cylinder, is shown in brown, the color of the DuPont Vespel resin from which it's made. Where the shell is cut away, the color is yellow, for the brass components of the switch. Each end of the switch has a brass end cap. From each endcap extend brass fingers. (They're actually hollow brass cylinders, but in cross section the walls of the cylinders look like fingers.) The fingers from one end don't quite touch the fingers from the other end -- there is always a tiny gap in between. When operators want the switch to conduct, they fill the gap with helium. When they don't want it to conduct, they pull a vacuum on it. Attached to the switch, through a thin tube, is the small chamber where the helium is stored in a zeolite getter. While one end of the heat switch is attached to the salt pill, the other end is attached to a hole in the center of a large mounting flange.
• Magnet Mounting Flange. The heat switch is connected to the mounting flange, and the supports for the suspension system are also based there. The flange is used to attach the ADR to the magnet and thus to the rest of the apparatus.
• Thermal Bus. The thermal bus consists of 4 copper rods which stretch from the salt pill out through the mounting flange, without touching the flange. On the free ends of the thermal bus bars are mounted the calorimeters.
• Calorimeters. The calorimeters are the astronomical sensors that the ADR is designed to cool. This diagram shows no details of the calorimeters. It only shows (in cross section) a flat plate, connected to the bus bars, where the calorimeters will be mounted.
• Calorimeter Housing. A roughly partly cylindrical, partly rectangular metal shell, open at the ends, surrounds the calorimeter mounting plate and the ends of the bus bars which protrude from the mounting flange. The housing is mounted to the mounting flange. Kevlar fibers from the housing to the bus bars are part of the suspension system.

Description of Photograph

The parts of the ADR in this photo, from right to left, are:

• Salt Pill. This appears as a smooth, shiny, gold-colored cylinder. On the pill's far right end, are some bolt heads, which are used in the suspension system. (Much of the suspension system is missing from this photo, including the Kevlar fibers that would attach to these bolts.)
• Support Structure Hardware. Just off the left end of the salt pill are some metal rings, more silver colored than the salt pill. In this photo they look like they might be just a different-colored extension of the pill, but they're not. In fact, they don't directly touch the pill. Their only connection to the pill is by Kevlar fibers. Attached to the rings, and exteding the support structure slightly, are some gold-colored plates, curved so that they, too, seem like an extension of the salt pill.
• Thermal Bus. The round copper bars of the thermal bus, which starts at the left hand end of the salt pill and extends through and past the support structure, can be seen through gaps in the support hardware. In particular, a bar runs the length of each gap between the curved plates of the support structure. The bus bars extend through holes in the Magnet Mounting Flange. There are four copper bars in all.
• Magnet Mounting Flange. The flange is a metal disk, gold colored. Around its edge is a series of bolt holes, used to mount the flange (and with it the ADR) to the magnet. The thermal bus bars extend through holes in the flange. The support structure hardware attaches to the flange. Mounted to the flange, on the side opposite the salt pill, is the Calorimeter Housing.
• Calorimeter Housing. The Calorimeter Housing is a shell, open at both ends, which serves as thermal shield for the astronomical sensors (that is, the calorimeters.) It hides from view both the calorimeters and the ends of the thermal bus bars. The end of the housing which attaches to the mounting flange is rectangular, the free end round. The color is silver.
• Electrical Connectors. There are some small electrical connectors mounted to the Magnet Mounting Flange. They are not labelled in the photo.

Brief Description of Drawing-Photo Comparison Page

This page compares the ADR photo and the ADR Cutaway Drawing. The labelled parts are:

• Salt Pill
• Thermal Bus
• Magnet Mounting Flange
• Calorimeter Housing

To see descriptions of those parts, see the individual pages for the photo and cutaway drawing. Links are below the comparison photo and drawing.