Analysis of mechanisms which lead to electrical breakdown in a krypton-filled tube using the time delay method

2003

The influence of positive ions and neutral active states on the memory effect in nitrogen-filled discharge tubes at 1.3 and 4.0 mbar pressures has been investigated. Analysing the thermal velocity of these particles as well as drift velocity of positive ions, it is shown that the positive ions have a dominant role in the breakdown initiation for afterglow periods lower than 30 ms, while the role of the neutral active states can be ignored because of their electrical neutrality. The estimated value of the positive ion recombination time in the afterglow for the pressures considered is about 30 ms. The atoms in ground states have a dominant role in breakdown initiation for afterglow periods higher than 30 ms. Our supposition is based on the earlier results that the long-lived Lewis–Rayleigh glow lasts up to several hours as a consequence of the recombination of these atoms on the wall. A detailed analysis of relaxation processes has shown that a contribution of vibrationally excited molecules as well as atomic and molecular metastable states created during the previous discharge cannot contribute to the memory effect significantly. Also, the contribution of cosmic rays to memory effect is analysed for the afterglow periods when the concentration of atoms in the ground state decreases to such a low value that their role in the secondary electron emission from the cathode is ignored.

Section: The Role Of Cosmic Rayssupporting

confidence: 67%

Section: The Role Of Neutral Active States In Memory Effectsmentioning

confidence: 99%

Kinetics of ions and neutral active states in the afterglow and their influence on the memory effect in nitrogen at low pressures

Živanović¹,

2003

“…According to [14], the most probable cause for the slow time-delay saturation could be related to the existence of the metastable gas atoms and molecules in the afterglow. This was confirmed later by many studies [15][16][17]. The positive ions and metastables created in the previous discharge and the presence of the cosmic rays, determine the shape of the memory curves.…”

Section: Memory Curvesmentioning

confidence: 59%

The statistical time-delay and the breakdown formative time contributions to the memory effect in Ne at 7 mbar pressure

Spasić

Radović

et al. 2003

The results of the electrical breakdown time-delay as a function of the relaxation time τ, known as ‘the memory curve’, are presented. The memory curve was experimentally established for the relaxation times from 3 ms to 300 s, for the Ne-filled diode at 7 mbar pressure. Statistical analysis was used to analyse the obtained time-delay values. The results show that for the relaxation times τ ⩽ 0.1 s the dominant part of the total time-delay is the breakdown formative time (tf ∼ 0.1 ms). The breakdown formative time obtained in this investigation shows the same ‘memory effect’ as the breakdown total time-delay, because it slowly increases with τ. For τ > 0.1 s, the statistical time-delay makes up the dominant part of the total time-delay, as was reported earlier.

“…where td sat is the saturation value of t d . This estimation obtained for krypton-filled tube with pressure p = 2.7 mbar is shown in figure 8 [31]. It is worth noting that this estimation for W is restricted to the area where W is close to unity.…”

Section: Analysis Of Time Delaymentioning

confidence: 79%

Electrical breakdown in low pressure gases

Ristić

Karamarković

2002

Self Cite

167

128

The paper presents the results of investigation of the electrical breakdown in low pressure gases when the secondary electrons released from the cathode play the dominant role in the initiation of electrical breakdown. The secondary electrons are created by the charged and neutral species formed during the previous breakdown and discharge as well as by γ-rays. Electrical breakdown investigations are based on the measurements of electrical breakdown voltage and electrical breakdown time delay for gas-filled tubes with spherical electrodes with diameters much larger than an interelectrode distance. Stochastic nature of both the breakdown voltage and time delay are discussed and their distributions based on experimental data are shown. The methods for the determination of static breakdown voltage are also analysed. The influence of different parameters (overvoltage, cathode material and its surface purity, gas pressure, glow current, etc) on time delay are studied. A special attention is paid to the memory effect in various gases that depends on the positive ion recombination times, catalytic recombination times in the case of nitrogen and hydrogen, as well as metastable states deexcitation times in noble gases. The analysis of this effect is done by memory curves on the basis of which the presence of long-lived neutral active states can be followed to their very low concentrations when cosmic and environment radiation play the dominant role in electrical breakdown initiation.