Prebreakdown events in liquid nitrogen

2014 It was shown previously that a small volume of liquid nitrogen in front of a sharp metal tip can withstand an extremely high field without any sign of breakdown or charge injection. Subsequently, the influence of the tip radius on the critical field has been investigated and is described here. Also, by monitoring the injection, it has been possible to analyse the influence of the injected charge on further onset and cut-off voltages. In the light of theoretical considerations, the results show that the injected current is definitely larger than it would be if it resulted from tunnel injection. In fact, the nature of the injected current depends upon various parameters ; however, a common feature to all current-voltage characteristics is a quadratic variation of the current with the applied voltage, which may be attributed to space-charge limited motion of carriers. Microscopic observation of a tip under injection has revealed the presence of small bubbles. The motion of these bubbles and their influence on the apparent mobility of the injected charges are discussed. LE JOURNAL DE PHYSIQUE TOME 35, FTVRIER 1974, Classification Physics Abstracts 6.700 8.270 8.700 PART I. ONSET AND CUT-OFF OF CHARGE INJECTION