Plasma diagnostic by emission spectroscopy during vacuum arc remelting

Abstract

The plasma produced during vacuum arc remelting of a Zircaloy4 electrode has been investigated by optical emission spectroscopy. Spatial variations of plasma emission along the arc axis has been measured with a specific apparatus consisting of nine aligned optic fibres. The plasma consists of zirconium atoms, of singly and doubly charged zirconium ions and of chromium atoms. The non-observation of emissions of tin and iron particles, which are, with chromium, the three main alloy components of Zircaloy4, suggests that the concentrations of these two species in the plasma are negligibly small. Distribution temperatures of atomic and ionic species of the order of 1 eV and high ionization degree of the plasma (greater than 70%) have been determined. The similar decay of the line intensities of the various species with increasing axial distance from the cathode surface indicates that the plasma composition remains approximately unchanged within the interelectrode region. Synthesis of the spectroscopic results has shown that the emission of vapour into the plasma cannot be accounted for by a mechanism of metal volatilization from the cathodic and anodic liquid surfaces only. It also involves emission mechanisms occurring in the cathode spot region, like the expulsion of metal droplets which volatilize or the ejection of particles.

Arc Behaviour and Cathode Melting Process during VAR: an Experimental and Numerical Study

“…Similar experiments have been carried out more recently by Chapelle et al on zirconium electrodes. 9,10) One of the main conclusions from these observations is that the behaviour of the arc is similar to the diffuse mode of a vacuum arc created between cold solid electrodes for the same range of current densities. The arc consists of several dispersed clusters of cathode spots moving very rapidly over the whole surface of the cathode, as shown on Fig.…”

OPTICAL CHARACTERIZATION OF 50 Hz ATMOSPHERIC PRESSURE SINGLE DIELECTRIC BARRIER DISCHARGE PLASMA

“…7 gives the graphical representation of the plasma parameters as functions of the inter-electrode gap. Using the relation V = Q/C and Equation (1), we can justify the observed behavior of the plasma parameters at different values of inter-electrode gap [7,11,14]. Many authors have researched on plasma study [22][23][24].…”

“…Again the N + 2 (B 2 + u ) excited state emits the characteristic photons of (0-0) band of first negative system as identified in recorded spectrum [11,14]. The emission intensity of the band is proportional to the population density of the N + 2 (B 2 + u )υ = 0 state.…”

“…The intensities of these spectral lines can be used for determinations of kT e and n e . The spectroscopic technique used to determine kT e is based on the measurement of the relative intensities of two or four spectral lines of same atomic species [14]. The emission line intensity of these spectral lines is kT e dependent and always proportional to the population density of excited states.…”

“…These processes involve electron impact excitation (from ground state N 2 (X 1 + g ) and first metastable state N 2 (A 3 + u )), pooling reactions, associative excitation, energy transfer between colliding particles and penning excitation [11]. The radiative decay of subsequent states emit the characteristic photons of (0-0) band of second positive system at 337.1 nm which is identified in the recorded spectrum [14].…”