Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Diode magnetic field influence on radiographic spot size   The Dual-Axis Radiography for Hydrodynamic Testing (DARHT) facility at Los
Alamos was developed for flash radiography of large hydrodynamic
experiments.Both axes now routinely produce radiographic source spot sizes
having full-width at half-maximum (FWHM) less than 1 mm. The beam canonical
angular momentum contributes to spot size, and it is minimized by using a
shielded source of electrons.An ideal shielded source creates the beam in a
region where the axial magnetic field is zero, thus the canonical momentum is
also zero, since the beam is born with no mechanical angular momentum.It then
follows from Busch's theorem that the canonical angular momentum is minimized
at the target, at least in principal.
  In the DARHT accelerators, the axial magnetic field at the cathode is
minimized by using a solenoid with reverse polarity to cancel out whatever
solenoidal beam transport field exists there. This is imperfect in practice,
because of radial variation of the total field across the cathode surface,
solenoid misalignments, and long-term variability of solenoid fields for given
currents. This article quantifies the relative importance of canonical momentum
in determining the focal spot, and establishes a systematic methodology for
tuning the bucking coils for minimum spot size.

16
The categories of this paper are: stat
31
The categories of this paper are: ao-sci
4
The categories of this paper are: cond-mat
6
The categories of this paper are: astro-ph
19
The categories of this paper are: eess
11
The categories of this paper are: hep-lat
22
The categories of this paper are: chao-dyn
30
The categories of this paper are: q-alg
9
The categories of this paper are: nlin
34
The categories of this paper are: chem-ph
32
The categories of this paper are: atom-ph
27
The categories of this paper are: comp-gas
12
The categories of this paper are: nucl-th
1
The categories of this paper are: cs
2
The categories of this paper are: math
37
The categories of this paper are: supr-con