  We develop an original apparatus of the granular impact experiment by which
the incident angle of the solid projectile and inclination angle of the target
granular layer can be systematically varied. Whereas most of the natural
cratering events occur on inclined surfaces with various incident angles, there
have not been any experiments on oblique impacts on an inclined target surface.
To perform systematic impact experiments, a novel experimental apparatus has to
be developed. Therefore, we build an apparatus for impact experiments where
both the incident angle and the inclination angle can be independently varied.
The projectile-injection unit accelerates a plastic ball (6~mm in diameter) up
to $v_i\simeq 100$~m~s$^{-1}$ impact velocity. The barrel of the injection unit
is made with a three-dimensional printer. The impact dynamics is captured by
high-speed cameras to directly measure the impact velocity and incident angle.
The rebound dynamics of the projectile (restitution coefficient and rebound
angle) is also measured. The final crater shapes are measured using a
line-laser profiler mounted on the electric stages. By scanning the surface
using this system, a three-dimensional crater shape (height map) can be
constructed. From the measured result, we can define and measure the
characteristic quantities of the crater. The analyzed result on the restitution
dynamics is presented as an example of systematic experiments using the
developed system.
