NIST rf Reference Cell Projects

This Web page describes projects utilizing a "reference cell" for generating radio-frequency (rf) discharges in various gasses at a frequency of 13.56 MHz. The reference cell concept grew out of a need to provide an experimental platform for comparing plasma measurements carried out in a number of separate but identical chambers. The design for this reference chamber was developed in the 1988 Gaseous Electronics Conference (GEC). At present, the cell is a conventional ultrahigh vacuum (UHV) chamber with a pair of 10 cm diameter, parallel plate electrodes. The detail mechanical drawings of the chamber, the electrodes and all of the components are available from NIST and can be down-loaded from Cell Drawings and Components.

The basic purpose of the reference cell was to provide a comparison between measurements performed on identical discharge sources by different groups to establish the necessary and sufficient conditions defining reproducible plasma parameters and establishing a reference rf-excited plasma that allows others to define and calibrate diagnostic measurements and theoretical models. Initial measurements addressed the voltage and current properties of the discharge under predetermined conditions of gas type, flow rate, pressures and applied rf voltages. The first experiments compared data on the first three Fourier components of the plasma voltage and current among six cells in different laboratories. Since these first experiments, over 20 cells have been established in different laboratories throughout the world (rf Reference Cells around the Globe) and the results of various experiments have been published (General GEC rf Reference Cell Bibliography).

The NIST rf Reference Cell Projects are a collaboration of three laboratories within NIST. The specific groups are the Quantum Processes and Metrology Group in the Physics Laboratory, the Electrical Systems Group in the Electrical and Electronics Engineering Laboratory and the CSTL Process Measurements Division in the Chemical Science and Technology Laboratory.