  Young massive stars in compact stellar clusters could end their evolution as
core-collapse supernovae a few million years after the cluster was built. The
blast wave of a supernova propagates through the inner cluster region with
multiple stellar winds of young luminous stars. We present the results of 3D
magnetohydrodynamic simulations of the plasma flows produced by a supernova
event inside a cluster with a population of massive stars similar to that in
Westerlund 1. We followed its evolution over a few thousand years (i.e. a few
shock crossing times). The plasma temperature, density and magnetic field,
which are highly disturbed by supernova event, relax to values close to the
initial over the studied period. The relaxation time of a cluster is a few
thousand years, which is a sizeable fraction of the period between the
successive supernova events for a massive cluster of a few million years age.
The spectra of the cluster diffuse X-ray emission simulated here should be
representative for the galactic and extragalactic young massive clusters. The
resultant magnetic fields are highly intermittent, so we derived the volume
filling factors for a set of magnetic field ranges. Highly amplified magnetic
fields of magnitude well above 100 $\mu$G fill in a few per cent of the cluster
volume, but still dominate the magnetic energy. The structure of the magnetic
fields and high velocity plasma flows with shocks in the system are favorable
for both proton and electron acceleration to energies well above TeV.
