A NEW CONCEPT FOR BACKGROUND REJECTION IN GAMMA-RAY ASTRONOMY - THE SUPERSHIELD

Expanding the scientific successes of GRO and SIGMA will require significant improvements in sensitivity for the next generation of gamma-ray instruments. The conventional approach of increasing detector areas and shield thicknesses will reach a practical limit with the current generation of instruments, especially as moderate-sized launch vehicles will certainly be the norm in the future. Further sensitivity improvements require novel approaches for reducing detector background. Here we describe some concepts for advanced shielding configurations which we call ''supershields''. Supershields combine layers of materials designed to moderate and absorb neutrons, along with conventional, active gamma-ray shields. Due to contradictory demands placed on shield designs by neutrons and gamma-rays, supershields afford significant flexibility to optimize shield geometry compared to conventional shielding methods. If properly designed, supershields have the potential to significantly reduce overall detector backgrounds using passive, inexpensive materials.