mo, 2-7 It was steep fronted and had a 22 foot snen from crest to trough. Hydrodynami¢ Yields, ARF attached two strings of blast switches and one dop- pler system to a taut cable runnine outward from the Umbrella device with the aim of measuring the time interval betweer, closures of the blast switches and the rate of phase change of an r.f. signal fed into the doppler cable. was received in the zero LCU and telemetered to a remote location. Date ecords were obtained for the blast switches only as the doppler catle was crimped during installetion. Preliminary deta analyveis yielded an effective hydro- dynamic yield of oe tance curves from which hydrodynamic yields are determined, however, showec an a3 yet unexplained deviation from the slope expected from "Jigwam results. Crater Dimensions. ONR and H.C. measured the Umbrella crater by means of pre=shot fathometer survey and a post-sho* lead=line and fathometer survey, A crater of about 20' depth and 15CO!' eic-cter vas found. 2el.c NUCLECR RADI TION +ND EFFECTS Program 2 included ten projects, which could be grouped into four cate- gories: 1. Underwater detonetions . 2. High=altitude detonations 3. Developmental shots wos .: 4. Nuclear radiation from a very-lcow-yreld device of particular interest to the army ef . Underwater Shots, shoo and Umbrella. Shipboard Radiation Vulnerability. It wes the object of this study to docu- ment the gamma-radiation phenomena gener:ted aboard three target destroyers by shots ‘fahoo and Umbrella. Both total gamma dose and gamma dose-rate histories were measured by film-badge dosimetry and garma~intensity-tine- yecorders (GiTR's), respectively. ben Poe th po 4k ao Unshiclded GITR stations and film badges ZX oan PaGE gr #7