Spectroscopic study and high speed imaging of a transient arc

Anode energy transfer in a transient arc

“…We have shown in a previous work [3] that the mass loss increases with current and time constant is more than ten times higher with copper than with graphite for a 6 mm diameter anode. It is negligible in the case of graphite for a current of 500 A and reaches 4.8 mg ± 5% for  = 24 ms and I max = 2000 A.…”

“…The comparison of images obtained with interference filters centered on copper and nitrogen lines provides qualitative information on these elements repartition. While nitrogen is distributed rather homogeneously in the plasma, a darker zone (indicating a low neutral nitrogen concentration area) can always be observed below the cathode for imaged recorded with the filter centered on nitrogen lines [3]. This can be explained by the prevalence of ionized lines over neutral lines considering the high temperature (> 20 000 K) [5,6] encountered.…”

“…The maximal current and the time constant of the RC circuit can be set independently; detailed description of the setup is given in [3]. The arc discharge is triggered by the closure of a thyristor: the current rises up to its maximal value in less than one millisecond, according to the thyristor switching on characteristic.…”

“…The high speed imaging of the arc has shown that copper vapors are present during all the discharge, even if the amount is very low for the first milliseconds [3]. The mass of metal required to get visible copper vapor is very low (0.1 mg for a 100 ms arc) when compared to the measured ablated mass (1 to 150 mg).…”

“…On the basis of our previous results [11] the voltage can be estimated to a few volts (at least 1 V). Considering that the power transferred to the anode P anode is proportional to current it can be written as: P anode = I. U anode (3) With the equivalent voltage V anode equals to 9.5 V ± 1.5 V. This represents 20% to 30 % of total voltage for arc length of 1 cm to a few mm. Then one can consider that the energy transferred to the anode can reach one third of arc total energy in our experimental conditions.…”