  We report on measurements of beam backgrounds during the first commissioning
phase of the SuperKEKB collider in 2016, performed with the plastic
scintillator and silicon photomultiplier-based CLAWS detector system. The
sub-nanosecond time resolution and single particle detection capability of the
sensors allow bunch-by-bunch measurements, enable CLAWS to perform a novel time
resolved analysis of beam backgrounds, and make the system uniquely suited for
the study of injection backgrounds. We present measurements of various aspects
of regular beam background and injection backgrounds which include time
structure and decay behavior of injection backgrounds, hit-energy spectra and
overall background rates. These measurements show that the elevated background
rates following an injection generally last for several milliseconds, with the
majority of the background particles typically observed within the first 500
us. The injection backgrounds exhibit pronounced patterns in time, connected to
betatron and synchrotron oscillations in the accelerator rings. The frequencies
of these patterns are determined from detector data.
