Extreme-High Vacuum Chambers Require Ultra-Low Outgassing Rates

Posted on: May 24, 2017

The requirement for extreme-high vacuum (XHV) systems is increasingly common in advanced research and manufacturing. Applications in atomic physics, nano-technology, semiconductor and other fields require processes in the extreme-high vacuum range (< 1x10^-12 Torr). The key to creating XHV systems is to produce a chamber with ultra-low outgassing rates. To achieve ultra-low outgassing rates, gases dissolved in the bulk of the chamber material (typically hydrogen) must be removed or prevented from leaving the material surface. AVT has entered a Cooperative Research And Development Agreement (CRADA) with NIST to study the effectiveness of various material and processing options for achieving ultra-low outgassing rates in vacuum chambers.

What material and processing options yield the lowest outgassing rates?

XHV chambers are typically constructed of stainless steel, aluminum or titanium. Various heat treatments and surface treatments are typically employed to achieve low outgassing rates. Commercial vendors of vacuum chambers rarely report or specify outgassing rates of chambers, mostly because of the difficulty and expertise required to perform such measurements. It is often difficult to compare published outgassing results using various techniques because different studies use different chamber geometries, environments, and poorly defined or implemented measurement techniques. There is no consensus on the best, most efficient way of producing vacuum chambers with ultra-low outgassing rates.

NIST and AVT shared expertise to develop a test matrix for XHV chambers

The objective will be to test several vacuum chambers with identical geometries but produced using different materials and material treatments. NIST is capable of producing high-quality traceable measurements of outgassing rates. NIST and AVT agreed on a test matrix defining the material composition and treatment of each vacuum chamber.


Baseline Chambers

304L SS

316L SS

316LN ESR

T6061 AI

TI

XHV Processed Chambers

316L SS

316LN ESR

2nd Round: E-polish/Air Bake XHV Chambers

316L SS

316LN ESR


AVT will be responsible for producing the test vacuum chambers and delivering them to NIST. NIST will measure the outgassing rates of the test vacuum chambers using an advanced gauge/instrument developed specifically for XHV study.

The results of this study will allow a better understanding of material and process options used to fabricate vacuum chambers, and the effects on XHV performance. Also it allows NIST to evaluate its measurement techniques and to identify which material and processes are best for vacuum systems. After all the measurements are complete, these results, along with a description of the test vacuum chambers and a generic description of the treatment will be published in a scientific journal.

Customers can select the best material & processing options for their unique requirements.

Vacuum chamber fabrication using ultra-low outgassing materials and specific processing techniques is critical to producing any extreme-high vacuum system. Each application brings different factors relating to chamber design, material options, processing techniques and chamber manufacturability. The results of the CRADA experiment and testing will give scientific data comparing the common material and processing options. AVT has chamber design and manufacturing expertise to help customers identify the most cost effective material and process options for their XHV chamber.

Contact AVT to review your XHV requirements