X-Rays are around 10^15 Hz. Gammas are more like 10^20 Hz. They are penetrating suckers. I just know that we had a 1/4-inch tantalum shield ready to fly on New Horizons, but ditched it because it only dropped the gamma flux by 1/3 to 1/2. It wasn't worth the mass hit to fly it...
I know. We have a metal X-ray set-up at work. The power level determines the depth of penetration. Is it possible to measure the power level of incoming X-Rays and Gamma Rays in either dBm or Watts?
I only work with things that go up to 50 GHz at 10 dBm max for operational testing. Various types of microwave absorber with either graphite, oxidixed iron powder, etc. attenuate reflections for a specific band. Metal is a mirror in this low region. Also sharp corners. Surface phase.