E.O. JOHNSON AND L. MALTER 142 (4004S AFTER DISCHARGE 15 1600av WHERE AV, IS THE VOLTAGE CHANGE IN THE RATIO 2 73: 1 FIG. 11. Double probe current-voltage characteristic. DIFFERENTIAL LTs) nating the leakage. Interestingly enough, the DPM FIG. 12. Double probe temperature determination plot seems to be sufficiently insensitive to error that the following the interruption of the discharge are plotted thods outlined above) within a few percent The values of v a are corrected for the voltage drops with those taken after the leakage has been eliminated. in the resistor R. The values selected for the computa- VI ILLUSTRATIONS OF THE USE OF THE DPM tion of ip are indicated in the same figure. The plot of the function [(2ip -1)/ie, against V a is presented in The presentation of the data which follow is mainly Fig. 12. The slope yields an electron temperature of intended for the purpose of illustrating the use of the 950K. The temperature was also computed by means DPM and not as a detailed study of any particular of Eq(13)(the equivalent resistance method). The phenomena which take place in the afterglow period. factor G is found directly from Fig. 11 and is The tests were carried out in the cylindrical triode shown in Fig. 9(B). Two sets of double probes were G=[in2/ip]va=0=112/243=0.463 employed, one in the cathode-grid region and the other The value of 0. 142 volts per ua for Ro is computed in the anode -grid region. The measuring set-up is shown from the slope of the characteristic of Fig. 6 at Va=0 in Fig. 9(A).(Only the cathode-grid probes are illus- The extensions of the fat portions of the characteristic trated.) give the value of ip at va=0, as (1.15+1.28)or The tube(containing Ar at 1 mm pressure)was fired 2.43 wamp. Substituting the above values into(13) by the simultaneous application of 8 usec. pulses to get; mp grid and anode. The probe current was determined fro T=11600(0.249)(243)(0.142)=1000°K deflections on a Tektronix No. 512 scope which has a This agrees quite well with the 950%K determined from the semilog presented in Fig Various cases illustrating the The value of o computed from Eq.(12)and the applicability of the DPM are presented below above value of G is 1.16. This agrees very well with the Case 1. Typical probe current decay curves for various value of 1.15 determined by insp ralues of Va are shown in Fig. 10. From these curves the point where Vd=0. We can ompute o Irom he current voltage characteristic can be obtained for any time. As an illustrative case, the data for 400 use The reason for this choice is discussed in the Appendix