Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Boundary-induced effect on the spoke-like activity in ExB plasma   The spoke instability in an $E\times B$ Penning discharge is shown to be
strongly affected by the boundary that is perpendicular to $B$ field lines. The
instability is the strongest when bounded by dielectric walls. With a
conducting wall, biased to collect electron current from the plasma, the spoke
becomes faster, less coherent and localised closer to the axis. The
corresponding anomalous cross-field transport is assessed via simultaneous
time-resolved measurements of plasma potential and density. This shows a
dominant large-scale $E\times B$ anomalous character of the electron
cross-field current for dielectric walls reaching $40-100$% of the discharge
current, with an effective Hall parameter $\beta_\mathrm{eff}\sim10$. The
anomalous current is greatly reduced with the conducting boundary
(characterised by $\beta_\mathrm{eff}\sim10^2$). These experimental
measurements are shown to be qualitatively consistent with the decrease of the
$E$ field that triggers the collisionless Simon-Hoh instability.

20
The categories of this paper are: acc-phys
5
The categories of this paper are: gr-qc
8
The categories of this paper are: hep-ex
6
The categories of this paper are: astro-ph
15
The categories of this paper are: nucl-ex
36
The categories of this paper are: cmp-lg
0
The categories of this paper are: hep-ph
23
The categories of this paper are: solv-int
27
The categories of this paper are: comp-gas
32
The categories of this paper are: atom-ph
35
The categories of this paper are: mtrl-th
4
The categories of this paper are: cond-mat
37
The categories of this paper are: supr-con
30
The categories of this paper are: q-alg
34
The categories of this paper are: chem-ph
16
The categories of this paper are: stat