Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Investigation of positive streamers by double pulse experiments, effects
  of repetition rate and gas   Streamer discharges are often operated in a repetitively pulsed mode and are
therefore influenced by species left over from the previous discharge,
especially free electrons and ions. We have investigated these effects by
applying two consecutive positive high voltage pulses of 200-700 ns duration to
a point plane gap in artificial air, pure nitrogen, other nitrogen-oxygen
mixtures and pure argon at pressures between 67 and 533 mbar. The pulses had
pulse-to-pulse intervals ({\Delta}t) between 200 ns and 40 ms. We imaged both
discharges with two ICCD cameras and combined this to a compound image. We
observe for values of {\Delta}t below 0.5-15 {\mu}s (at 133 mbar, depending on
gas mixture) that during the second pulse the streamers continue the paths of
the first-pulse streamers. We call the maximal time for which this continuation
still occurs the continuation time. For N$_{2}$ - O$_{2}$ mixtures, this time
has a maximum at an oxygen concentration of about 0.2%. According to our plasma
chemical modelling this maximum is determined by the electron loss rate which
has a minimum around this oxygen concentration. Depending on oxygen
concentration the dominant recombining positive ion is N$_{4}^{+}$, O$_2^+$ or
O$_{4}^{+}$ where O$_{2}^{+}$ dominates around 0.2% O$_{2}$ and recombines
slowest. For increasing values of {\Delta}t we observe that after the
continuation phase first no new streamers occur at all, then new streamers show
up that avoid the entire pre-ionized region. Next we see new thin streamers
that follow the edges of the old channels. For larger {\Delta}t (10-200 {\mu}s)
the new streamers start to increase in size and move to the centre of the old
channel. Finally, around millisecond timescales the new channels are completely
independent of the old channels.

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The categories of this paper are: hep-ph
7
The categories of this paper are: hep-th
15
The categories of this paper are: nucl-ex
34
The categories of this paper are: chem-ph
37
The categories of this paper are: supr-con
26
The categories of this paper are: bayes-an
2
The categories of this paper are: math
10
The categories of this paper are: q-bio
35
The categories of this paper are: mtrl-th
19
The categories of this paper are: eess
28
The categories of this paper are: alg-geom
29
The categories of this paper are: funct-an
17
The categories of this paper are: q-fin
21
The categories of this paper are: adap-org
27
The categories of this paper are: comp-gas
9
The categories of this paper are: nlin