  The primary secondary particles from the spallation target of the China
Spallation Neutron Source are mainly gammas and neutrons, which are related to
the distribution of the incident proton. The reconstruction of proton beam spot
could be implemented based on the distribution of secondary particles. The
methods of pinhole imaging and Compton imaging are developed by measuring the
gamma distribution based on the pixelated detector. The secondary gammas could
be detected by the pixelated gamma detector directly. The neutron can be
identified by detecting the characteristic (478 keV) $\gamma$-rays from the
$^{10}B$(n, $\alpha$) reactions. In order to detect secondary neutrons, a layer
of $^{10}B$ converter is added before the pixelated gamma detector. The
pixelated gamma detector is sensitive to the characteristic (478 keV)
$\gamma$-rays and then the neutron imaging could be achieved based on measuring
the distribution of the characteristic gamma.
