X-Ray Calibration Facility (XRCF)

XRCF Vacuum System

Instrument Chamber

The cylindrical stainless steel vacuum chamber is 24 feet in diameter and 75 feet long. The usable test volume is determined by the chamber thermal shroud inside diameter, end panels, and the chamber experiment rail system. The usable test-volume inside the chamber has a diameter of 6.1m (20ft.) The rail system cuts a chord through the test volume circumference 2'-6" from the bottom. The test volume is 60 feet long.

The chamber opens into the clean room and is serviced by a rail system for test article insertion and removal. The rails are 2" diameter roundways on a 7'-4" center. The rail system runs the full length of chamber test volume and extends 67 feet into the clean room. The rails inside the chamber are supported on vibration isolated piers (11 pairs) each of which is capable of test article interface.

The (1700ft.) long stainless steel vacuum guide tube is attached to the west end of the instrument chamber. The chamber and tube are separated by a 60" diameter gate valve. The tube is constructed of piping with three different diameters. Attached to the chamber gate valve is (356ft.) of (5ft.) diameter tube. The tube transitions to 1.2m (4ft.) diameter at this point and extends 113m (371ft.) to the west where the tube steps to 0.9m (3ft.) diameter. The 0.9m (3ft.) diameter tube extends west the remaining 297m (973ft.) to the X-ray source chamber(s). The X-ray source systems are also evacuated and have their own pumping systems.

Evacuation of the chamber and guide tube from atmosphere to 4 x 10^-2 Torr is accomplished by combinations of oil-sealed rotary plunger pumps and Roots blowers. From this point, test volume pressures of less than 1 x 10**-6 Torr are achieved using gaseous helium refrigeration cycle cryogenic vacuum pumps. Evacuation time is 8-12 hours (less than 10**-5 Torr). Supplemental pumping is performed by oil-free turbomolecular pumps. The use of these pumping systems ensures that the chamber and guide tube meet the strict cleanliness requirements of an optical test facility.

High Purity Air/Gaseous Nitrogen:
The entire facility is supported by 500 psig high purity air and nitrogen systems.

Liquid Nitrogen (LN2):
A 54,500 gallon storage area and redundant 250 GPM pumps supply the chamber with 130 psig of subcooled (and recalculated) LN2 for cold wall operation.

Synthesized Air:
Liquid nitrogen and liquid oxygen are pumped through vaporizers and mixed to produce ultra-clean breathing-quality air for facility depressurization and clean room use. Storage capacity is greater than 100,000 standard cubic feet.