  A single-field-period quasi-isodynamic stellarator configuration is
presented. This configuration, which resembles a twisted strip, is obtained by
the method of direct construction, that is, it is found via an expansion in the
distance from the magnetic axis. Its discovery, however, relied on an
additional step involving numerical optimization, performed within the space of
near-axis configurations defined by a set of adjustable magnetic-field
parameters. This optimization, completed in 30 seconds on a single cpu core
using the SIMSOPT code, yields a solution with excellent confinement, as
measured by the conventional figure of merit for neoclassical transport,
effective ripple, at a modest aspect ratio of eight. The optimization
parameters that led to this configuration are described, its confinement
properties are assessed, and a set of magnetic-field coils is found. The
resulting transport at low collisionality is much smaller than that of W7-X,
and the device needs significantly fewer coils thanks to the reduced number of
field periods.
