Surface Science Analysis Chambers
MDC SSAC-12 and -12D are versatile general purpose surface science analysis
chambers which have proven to be suitable for a wide range of analytical studies or
MDC surface science chambers are constructed of type 304 stainless steel and
with a total of 18 access ports. In addition to a vacuum pump port at the base, the
chamber includes three 8", two 6", three 4-1/2" and nine 2-3/4 inch Del-Seal™ CF
metal seal flanges with tube diameters of 6", 4", 2-1/2" and 1-3/4 inch, respectively. The
chamber access ports accommodate a variety of experimental devices, analytical
instruments, viewports, electrical and motion feedthroughs, vacuum measurement gauge
tubes and other accessories.
The SSAC-12 chamber has a 14-5/8 inch female wire seal flange on the pump port
while the SSAC-12D is supplied with a 14 inch Del-Seal™ CF metal seal flange. As
previously noted, all 2-3/4 inch Del-Seal™ CF flanged ports are constructed with an
oversized 1-3/4 inch outside diameter tubing to provide maximum apertures and allow the
installation of larger devices. Access ports are precision aligned with a
helium-neon laser during construction. Each port is directed at one of three internal reference or
focal points A, B and C, or a vertical centerline. Angles and distances to these
points are listed in a table alongside the diagram of the chamber.
Fastening and sealing hardware, including copper gaskets and bolt sets, are found
under the individual size flange in the Flanges & Fittings section of this catalog.
MDC employs advanced tungsten inert gas (TIG) welding techniques with high
purity Argon as the inert gas medium. Manual as well as automated orbital welding machines
are at the heart of all welding operations. MDC adheres to stringent UHV welding
standards and practices including that of nonfiller metal, all internal fusion weld joints.
External weld joints are not used unless required for structural reinforcement and
then, limited to skip or span weld configurations. In the event that a weld joint
can not be made internally, a one hundred percent full penetration external weld will be
used. All weld joints are leak tested using a mass spectrometer leak detector with a
minimum Helium sensitivity of 2x10-10 standard cc/sec.
Chamber Surface Finishes
Vacuum chamber finishes include internal and external glass bead blasting of all body
and port tube surfaces. Flanges and machined components have a standard 64
micro-inch surface finish. Seal surfaces are machined with a 32 micro-inch
concentric finish suitable for standard metal seals. All internal surfaces are electrochemically
The electropolishing process is the reverse of electroplating where the work piece is
made the anode and dissolves or gives up material in the electrolytic process. The
electropolishing operating conditions are controlled so that atomic oxygen
forms and reacts with the metal work piece surface. According to one theory, the high points of
the metal surface are most readily oxidized and this oxidized material is thereupon
dissolved in the electrolyte and otherwise removed. Selective solution of the high
points of a surface tends to give a very smooth finish comparable or superior to a
mechanically buffed surface. In contrast to mechanical polishing, electropolishing
produces a strain free surface.
MDC is dedicated to providing high and ultrahigh vacuum components of the highest
quality and performance. To this end all vacuum rated components manufactured by
MDC and its divisions are leak tested repeatedly, as required, throughout the
manufacturing process to insure these goals are met. All weld joints and flange seals are
leak tested using a mass spectrometer leak detectors with a minimum Helium sensitivity
of 2x10-10 standard cc/sec.