  Colliding collisionless shocks appear in a great variety of astrophysical
phenomena and are thought to be possible sources of particle acceleration in
the Universe. We have previously investigated particle acceleration induced by
single super-critical shocks (whose magnetosonic Mach number is higher than the
critical value of 2.7) (Yao et al. 2021, 2022), as well as the collision of two
sub-critical shocks (Fazzini et al. 2022). Here, we propose to make
measurements of accelerated particles from interpenetrating super-critical
shocks to observe the ''phase-locking effect'' (Fazzini et al. 2022) from such
an event. This effect is predicted to significantly boost the energy spectrum
of the energized ions compared to a single supercritical collisionless shock.
We thus anticipate that the results obtained in the proposed experiment could
have a significant impact on our understanding of one type of primary source
(acceleration of thermal ions as opposed to secondary acceleration mechanisms
of already energetic ions) of ion energization of particles in the Universe.
