  Laser produced $gamma$-photons can make an important impact on applied and
fundamental physics that require high $gamma$-photon yield and strong
collimation. We propose addition of a constant magnetic field to the
laser-solid interaction to obtain the aforementioned desired $gamma$-photon
properties. The $gamma$-ray flash spatial and spectral characteristics are
obtained via quantum electrodynamics particle-in-cell simulations. When the
constant magnetic field aligns with the laser magnetic field then the
$gamma$-ray emission is significantly enhanced. Moreover, the $gamma$a-photon
spatial distribution becomes collimated, approximately in the form of a disk.
