Surface Charges in a Coplanar-Electrode Microgap Discharge Measured at Various Gas Pressures Using an Electrooptic Crystal

Abstract

The surface voltage and charge on the dielectric barrier in a plasma display panel (PDP)-like microdischarge have been measured using an electrooptic crystal. The initiation of discharge starts the accumulation of surface charges and the charges spread uniformly over the entire region of the electrode surface under the condition of a time resolution of 0.1 ms. For the case of a gas mixture of Ne+Xe (10%), the plasma light emission at the cathode side is much stronger than that at the anode, however, the quantity of surface charges accumulated at both electrodes are the same. The surface charges at various gas pressures are also measured as functions of externally applied voltage and total charge flowing in an external circuit estimated from the discharge current. These characteristics for the microdischarge are compared with the results obtained for macrodischarge. It is found that the voltage difference on the barrier surface between the ground and high-voltage electrodes, caused by the accumulated charges, is an important factor in determining the barrier discharge.

Electron energy loss spectroscopy of wall charges in plasma-facing dielectrics

“…Hence, charge densities n p s > 10 11 cm −2 may be measurable by this technique. But this is also the range expected for plasma-facing dielectrics as can be inferred from experimental studies of the charging of dust particles in low-temperature plasmas 44 and measurements of the wall charge by the Pockels effect [16][17][18] .…”

“…The calculation of the loss function w P q , ( )   has thus been reduced to the determination of the function c w ¢ q z z , ; , ( )   . The fact that the electrons are embedded in a dielectric structure is taken into account in (18) by the functions in front of c w ¢ q z z Im , ; , ( )   .…”

“…The numerical work consists of two major parts: (i) calculating the density-density response function c w ¢ q z z , ; , ( )   by solving the integral equation (20) and (ii) integrating c w ¢ q z z , ; , ( )   over z and ¢ z as specified in (18) to obtain the loss function w P q , ( )   , which is then inserted into(1) to yield after integrating over q   the EELS cross section dS/dω. In order to obtain c w ¢ q z z , ; , ( )   we first have to construct the function c w ¢ q z z , ; , 0 ( )   .…”

“…Obtaining c w ¢ q z z , ; , ( )  in the manner described is numerically the most challenging task. The integrations specified in(1) and (18), on the other hand, can be performed with standard integration routines. For the numerical work we used dimensionless variables, measuring energies and lengths, respectively, in units of k B T and…”

“…There exists a number of techniques to estimate the charge accumulated by plasma-facing solids. Electric probes [9], surface potential measurements [10][11][12], opto-mechanical devices based on the reflection of a laser by a cantilever [13], and the Pockels effect of an electro-optic crystal [14][15][16][17][18][19] have been employed for that purpose. However, with the exception of the Pockels effect measurements, the methods are rather invasive.…”