A novel probe for spatially resolved emission spectroscopy in plasmas

Abstract

A novel diagnostic device is developed to obtain spatially resolved emission profiles in plasmas. A ceramic tube is immersed into the plasma and moved along its longitudinal axis.A lens located at the other end of the ceramic tube images light onto an optical fiber which guides the light to a detector. In the case that the plasma emission is detected within a negligible solid angle, simple differentiation of the measured signal yields spatially resolved emission profiles. For non-negligible solid angles, spatial resolution can still be obtained by a more sophisticated evaluation. The design of the probe and the underlying theory are presented. The arrangement of the optics is analyzed in detail. Measurements in an inductively coupled radio-frequency (RF) hydrogen discharge in a GEC cell at different RF powers, neutral gas pressures and axial probe positions are performed. The obtained radial emission profiles of the Balmer-α line exhibit a torus-like structure which reflects the structure of the induced electrical field of the antenna. Furthermore, the transition from H to E mode at lower powers is observed.Based on a corona equilibrium model excitation rates are calculated out of electron energy distribution functions measured by an RF compensated Langmuir probe. A comparison of measured emission profiles with calculated excitation rate profiles shows very good agreement. Integrated emission profiles obtained by camera images are Abel inverted and compared with profiles obtained by the optical probe. The comparison demonstrates the advantage of the optical probe.

Wave propagation and noncollisional heating in neutral loop and helicon discharges

“…36 To ensure that the probe is not disturbing the helicon plasma, a 30 cm long and 1.5 mm thin ceramic tube was fixed to the probe head. The probe tip is 1 cm long and has a diameter of 50 m.…”

“…Whereby in the high magnetic field case, the wave travels along the discharge axis but essentially no wave-particle interaction takes place. The main heating occurs at positions where the electric field induced by the antenna is maximum, 36 suggesting that ICP power coupling dominates.…”

“…10͑a͒ that the maximum oscillation occurs at the radial position of roughly two-thirds of the antenna radius ͑110 mm͒ at which a maximum of the induced electric field occurs. 36 Therefore, Fig. 10͑a͒ approximately represents the electric field distribution.…”

Spectroscopic observation of radiation emitted from thermally-produced spray droplets and the resulting temperature determination

“…[1][2][3][4][5] Although it is an established technique having a history of more than a century, operation of spray guns for obtaining good coating layers still relies on experienced technicians. Because of the necessity of meeting more and more stringent requirements for coating quality and cost reduction from customers, combined with a decreasing number of experienced technicians in Japan in recent years, there has been a strong need to try to monitor spray processess, [6][7][8][9][10] so as to optimize the operational conditions at hand. It is known for many years that the qualities of the coating layers, expressed in terms of adhesion strength, porosity, and hardness, are strongly influenced by the pre-treatments of substrates, along with the temperature and velocity of spray droplets impinging upon the substrates.…”

Spatially and temporally resolved optical spectroscopic investigations inside a self-pulsing micro thin-cathode discharge

“…In this way, the fiber probe was used to perform time integrated and spatially resolved optical emission spectroscopic (OES) measurement, similar to an optical probe for spatially resolved OES described in [7]. Here, at the probe position x, the measured intensity S(x) is given as an integral over the local emissivity I(x) of the plasma:…”