abouc 30,000 meters. In either case the half-thickness is roughly proportional to the third power of the photon energy. Bence, at Teak altitude, X-rays pere- trate to an extent sufficienr to hswe a direct effect om materials expos.d muy thousands of feet from the burst point. This effect is expected to be quite severe for an intense beam of soft I-rays, sicce it becomes absorbed in 2 surface thickness of a few microns is wost dense materials. Thus X-ray damage potectial has produced much interest in the X-ray yield of muclear varbeads. ‘There are Jk p , certainly situations where the X-ray yield of a dewice would hawe a strung influence ow its effectiveness as an anti-ICEM warhead. (b After emission frow the case, the X-rays propagate to the measuring stations with consequent absorption in the intervening air as well as absorption in the detector filters. Energy E of X-rays reaching the unit ares of the calorineter surface is 2 0) p,(r)dr- (4.0 P2e£,%3(P)0535) seca] E =» cos F ¥(0) e ap, es; 77. HBand 4% / oe deleted. (2.1) ,

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