This document ce“sists of otpages No \ / of Navy DEPARTMENT et JOINT CROSSROADS COMMITTEE 17 January 1947 Wasaincton 25, D. C. 22% Jjopies AQGAT 1 SIUPISECEET— ~—NCLASSIFIED SE X Doctor Wright Langhem : P.O. Box 1665 Sante Fe, New Mexico Dear Wright: Joe Nolan has gotten togethtr a group of CROSSROADS photographs which have been released for public views, and these were forwarded on to you today. Therefore, you should probably receive them even before this letter since no problems of delivery are involved. In going through the safe in the main CROSSROADS office they discovered a copy of the section of our report dealing with the neutron flux. This copy was supposed to have been delivered to you by courier in September and I must apologize for such a bad foul-up. I am now enclosing it along with a copy of a Checlon CRoS COLLECTION t BOX No. “Th S3S4- \ Peas graph showing the variation with distances for slow neutrons. The points used on this graph were carefully selected to make sure no shielding of any sort existed and their accurate locations on the ships were used in computing the distances. As you will see, they agree quite closely with the predicted equation of Hirschfelder f CAB nepositonyOS Abn 5 kLi However, and Magee. In anelyzing these neutron results, w have raised a few questions. We have put them to Doctor Dessauer and he is checking them, but I wondered if perhaps you or some one at Los Alamos could also help us out. The first point involves the question whether the Sulphur pills are measuring all the fast neutrons which are of physiélogical importance. Since the minimum energy of the neutrons captured by the Sulphur is between two and three Mev and since it is our impression that a number of the - fast neutrons of physiological significance are in the energy range between 1/10 and 2 Mev, we thought our a values might be considerably in error. Would it be possible 6 to obtain the energy distribution of the fast neutrons which OS actually get out of the bomb? Another point involves the “ question of whether we are using the proper cross-section for wr TENCEASSIRED Esad since they may in prectice be Ciaesifieation chan¥é ee by Authority of tid ons with energies greater than the tragen PARP Cummiission, ’ teONDradiNeeeee. (afc bd Eeseatis, eee gl abenuge in Clos.ie wal) (Sasnateec DPpepsoaBia uu ero, aai . easeee (wate). lL =