Arc expansion in xenon flashlamps

Abstract

Plasma arcs in large diameter (d>1 cm) xenon flashlamps often do not completely fill the bore of the discharge tube. The arc is usually initiated on one side of the discharge tube, adjacent to the ground plane, and the fraction of the discharge tube filled with plasma varies as a function of axial location. A model is presented that describes, from first principles, arc expansion in xenon flashlamps. The model simultaneously solves a coupled set of one-dimensional transport equations in different regions of the discharge tube to simulate two-dimensional effects in hydrodynamics, electron kinetics, and radiation transport. Using this method, expansion of arcs initiated at arbitrary locations within the discharge tube can be studied. Arc filling fractions are found to decrease with increasing filling pressure of xenon, increasing diameter of the discharge tube, and decreasing stored energy in the discharge circuit. The arc filling fraction also decreases as the breakdown filament moves away from the axis of the discharge tube and towards the wall. Arc expansion is slowed and ultimately halted by a lowered E/N (electric field/gas density) in the gas exterior to the arc, rapid conversion of atomic ions to molecular ions and their subsequent recombination, and by the efficient manner in which radiation dissipates energy which might otherwise be available for thermodynamic expansion of the arc. The asymmetric expansion of the plasma arc results in asymmetric heating of the inside wall of the discharge tube, also calculated in the model. The growth of the plasma arc is also found to be in part responsible for changes in the spectrum of radiation emitted from the arc for various angles of observation. This effect results from wavelength-dependent absorption coefficients in the plasma.

Ac breakdown in near-atmospheric pressure noble gases: I. Experiment

“…The reactions given in table 2 represent a simple model including processes with most influence on the breakdown process in pure Ar of Xe. Additional reactions are also possible [16,17]. The important thing to notice is that there are two classes of reactions mentioned -the first one depending on the electron energy and density, and the second one depending on the density of the heavy particles.…”

Dynamics of flashlamp pumping a Nd:Cr:GSGG laser

“…(1) only gives a good approximation after the plasma has formed in the flashlamp. While the plasma is forming the current dynamics can be quit complicated [4,5]. We also note that by using a smaller capacitor and a larger voltage O V one can in theory decrease the discharge time while keeping the energy constant.…”

<title>Calculations of dynamic stresses in the envelopes of pulsed Xe flashlamps</title>

“…Some error is expected in using eqn. (14) since electronic excitation and Coulomb interactions between charged particles are likely to cause xenon flashlamp plasmas to depart from the assumed ideality.…”

“…The method we used for predicting xenon pressures is now complete and includes eqns. (4), (10), and (13)(14)(15)(16)(17). We tested the agreement between pressures predicted by our method and the pressures predicted by the empirical relationship1°p…”

“…The two dominant heat processes are due to direct contact between the envelope with the plasma: recombination of ions and electrons at the surface, and thermal 14 A third weaker source, optical absorption, is presumably dominatedby the 120 nmresonance transition ofneutralxenon. At 120 nm, the optical absorption depth in quartz is less than 1 im.15 This absorption depth is much less than the thermal diffusion distance in quartz during the pulse, which is more than 10 .tm for pulselengths greater than 200 jts.…”