Surfatron 2450 MHz

AN EFFICIENT AND STABLE MICROWAVE SUSTAINED PLASMA SOURCE PROVIDING EXCITED ATOMS AND MOLECULES, RADICALS, IONS AND PHOTONS

APPLICATIONS

- ELEMENTAL ANALYSIS
- OPTICAL SPECTROSCOPY
- SURFACE PROCESSING
-PLASMA CHEMISTRY

MAIN PARAMETERS

MAIN ADVANTAGES

Stability : the discharge is sustained in a non resonant mode.

Reproducibility : impedance tuning is unambiguous and for given operator set discharge conditions, the plasma is fully reproducible without anv need for retuning at start-up.

Efficiency : as a rule, close to 0% reflected power is achieved, without the assistance of external impedance tuning means.

OPERATING PRINCIPLES

The use of electromagnetic surface waves allows one to create a plasma in a quartz tube at frequencies ranging from 10 MHz to 10 GHz. In order to cover this frequency range different applicators have been designed. The surfatron is one of them ; depending on its dimensions it can be used between 300 MHz and 2450 MHz.

The present one has been optimised for 2450 MHz an ISM frequency. The discharge tube must be a low loss high temperature-resistant dielectric such as fused silica or ceramic. It must fit as closely as possible to the inner diameter of the sleeve from the surfatron. For example : with a 6,5 mm i.d. sleeve, we recommend using a 6 mm o.d. discharge tube. Air is required to provide external cooling of the discharge tube when operating at atmospheric pressures (plasma density close to 10 ¹⁵/cm³ in that case). Water cooling of the surfatron body is required when operating above 150 W.

The length of the plasma column increases with microwave power past some threshold value (typically for argon 30W while for helium it is close to 150 W).

CAUTION

A small diameter Faraday cage can be attached to the front plate ring. It should be long enough to enclose not only the plasma column but also the dielectric tube full length.

PRACTICAL EXAMPLE

For Fourier Transform Emission Spectroscopy, to avoid spurious spectral lines due to the mains 50/60 Hz, we recommend using our low ripple microwave generator GMP 03 KE/D.

The present device is based on work achieved at the Universit© de Montreal. Patents in many countries (MOISAN, LEPRINCE, BEAUDRY and BLOYET).