helium

But are these reflectors mentioned work specifically for x-rays, or is it only neutrons? It says " In practical applications, the amount of material required for criticallity is modified by shape, purity, density, and the proximity to neutron-reflecting material, all of which affect the escape or capture of neutrons." And also " Often the same layer serves both as tamper and as neutron reflector."

Can x-rays be reflected? I thought x-rays can be neither reflected nor focused (such as light with a lens). I found this quote from an article from the link below: "Scientists have long been aware of the advantages of X-ray imagers, but they have been difficult to build. X-rays have enough energy to pass right through an ordinary mirror instead of being reflected off it. However, lower-energy or "soft" X-rays can be reflected if the mirror is stood on edge so that the incoming radiation just grazes the surface." http://imagine.gsfc....ray_mirror.html So, if x-rays really can be reflected off a mirror, how exactly does it work? Are the optical properties of the mirror important for this to occur? Can any type of mirror be used? Won't x-rays graze off of any object? On the same topic of x-rays and mirrors, are mirrors implemented in x-ray lasers, and if so, how?