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Diagram (not to scale) illustrating the essence of the mesa-structure PBJT of the present experiments, and optical imaging of the collector emission with a telescope and a gated, ICCD array. For the sake of clarity, the anode for the PBJT collector is not shown.
Series of false color images, captured by a telescope and ICCD detector, of the emission produced by the negative glow and sheath edge in a PBJT. For these measurements, the anode-cathode separation and Ne pressure were fixed at mm and 25 Torr (300 K), respectively. The spatial scale provided in (d) and (h) represents the FWHM for the image along the y coordinate. All data were recorded with a 2 V peak-to-peak (0.7 V RMS) sinusoid (shown at the top of the figure) driving the emitter-base junction, and the blue dots superimposed onto the waveform denote the times at which images (a)-(h) were acquired.
Variation of the PBJT base current (ib ) with the base terminal voltage (VB ), for a 2 V peak-to-peak, 100 Hz sinusoid driving the EB junction. Collector emission images recorded at several operating points (represented by the open circles) are given, and the circuit employed for these measurements is shown by the inset at lower right. For convenience, the blue arrows indicate the direction of travel for the hysteresis characteristic. VCC and pNe were fixed at 320 V and 25 Torr, respectively.
Lineouts (y-axis) of images similar to those of Fig. 2 . Data are presented for two points in time, t = 1.8 ms and t = 5.4 ms, that correspond approximately to maximum forward and reverse bias, respectively, of the EB junction. For convenience, the t = 5.4 ms profile (reverse bias) is also shown rescaled so as to match the peak of the forward bias (t = 1.8 ms) lineout. Notice that the anode-cathode gap is 1.85 mm.
Comparison of the temporal history of the measured sheath thickness (a) with the waveforms for the collector and base voltages (VC [panel (b)] and VB [panel (c)], respectively). The negative overshoot in sheath thickness (shown early in each positive half-cycle) is a measurement artifact and is highlighted in red.
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