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 polished.

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. 

Leak Testing
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.

• In general, the central reference point is an arbitrary point on a reference plane
• A base flange, reference plane and the zero point are selected for symmetry and simplicity
• The central reference point, or zero point, is given XYZ coordinates of (0,0,0)
• All focal point dimensions are measured from the zero point
• Port Lengths and angles are measured from focal points
  
  
  

• The polar angle of a port is measured in a vertical plane that includes the focal point of the port and the centerline of port
• The azimuthal angle of a port is measured as a projection of the port centerline onto a horizontal plane that includes the focal point of the port
• Example: 
  Port 14 is aimed at focal point C
  The cutting plane is vertical and passes through C
  The cutting plane is rotated about a vertical line through C to include the centerline of Port 14
• The polar angle of 25 degrees is measured in the cutting plane
• The azimuthal angle of 55 degrees is measured in the focal plane.