MEASUREMENTS IN GAS DISCHARGES T. The result is -OLT METER T=1160va-V4 (16) In the case of the intercept method it is found tI nless vd and vd'' are chosen too close to the knees TERENTLAL he value of T. determined is in excellent agreement TYPE 52。 SCILLOSCO with that obtained by the other methods. In summary we can say that any error in the choice of Zip tends to be compensated with the result that the error registered in T. will usually be 5 percent or less. It is obvious that the most certain values of T, are obtained in the cases where the flat portion slopes are a COLLECTING AREA minimum. Comparison of corresponding temperatures IM ARGON FILLING obtained with different sets of probes, each set having different values of slopes in the flat portions, indicates 日) EXPERIMENTAL TUBE that the 5 percent estimate is a reasonable one This is ARC CURRENT DURING DISCHARGE also borne out by the close correspondence of tem peratures as obtained from,(1)the logarithmic plot method based on Eip evaluated at the knees, and(2)the C)OPERATING CONDITIONS other two methods where 2ip is computed from the FIG 9. Tube and circuit for double probe studies of interpolated values of ip, and i It will be noticed that the mathematical treatment of the dPm is based on the potential diagram of Fig. 8 choice of this value is explained in the Appendix. From which represents an ideal case in which uniform electron these extended curves one can obtain the value of Eip densities and probe-plasma potentials exist along the corresponding to Va=0. (An illustration of this pro- probe surfaces. Such an ideal situation is not achieved edure is given in Fig. 11)Experience has shown that in practice. However, it can be shown in a perfectly if one fails to make this correction for Si, when em- general and rigorous manner that non-uniform electron ploying the equivalent resistance method, but instead densities and probe-plasma potentials introduce no make of the positive ion currents corresponding to errors into the temperature measurements, Such non- points y and z of Fig. 7, then the values for T. come out uniformities, even when quite large, only introduce to be too large, but virtually never by more than 5 percent. Thus for rapid and approximate temperature determinations one can simply make use of ip, and i as determined from Fig. 7. C. The Intercept Method In some cases the equivalent resistance method ot be used owing to the fact that when vd=0, one is operating in a region of positive ion saturation to one of the probes(i.e, in region xy or ww of Fig. 7). In that case another rapid method is possible which does not require the laborious computations of the logarithmic FIG 10. Double nt decay curves be of Fig 9 plot method small corrections in the value of o as determined by By simple algebra Eq(6)can be transformed into: Eq (7). This deduction is consistent with the observa- ion that the value of o determined by Eq. (7)is usual (15) in close agreement with its value determined from either the log plot or the factor G. In the case of probes used in tubes with oxide Now let Va be the value of Va which corresponds to cathodes it has been found at times the deposition of i/ieD, and let Vd be the value of Vd which cor- barium onto the glass probe insulation(with subsequent responds to Eip/ie= F. D and F are chosen arbitrarily. leakage)causes the flat portions to have considerably use of the fact that p =e/kTe, one can solve readily for the probe leads seems to burn out the g Tesla coil to Then, substitution of these values in (15)and making increased slopes. a short application of a