DISCOVERY OF THE NEUTRINO — COWAN 429 



If we were seeing antineutrinos from the reactor, we should not 

 be able to reduce their intensity on the detector by putting absorbers 

 around it. If, on the other hand, we were seeing only gamma rays 

 and neutrons, it should be easy to change the rate with absorber. — 



This simple experiment, however, took some time to devise, for a 

 considerable amount of material was needed to stack aromid the 

 detector to form our shield. This amount of anything looked very 

 expensive to us. We first thought of wooden planks and timbers. 

 The cutting and fitting problem was too great for wood. We consid- 

 ered water, but the tanks required would have been expensive and very 

 large. 



As we were in South Carolina in the summer, an obvious suggestion 

 was a great pile of watermelons. We doubted that they would have 

 survived long enought in a sweet condition. Another suggestion 

 was sacks of hominy grits. An enterprising member of the group 

 actually located a warehouseman in Augusta, Ga., who was willing to 

 lend us the requisite amount. We feared, however, that he would be 

 reluctant to take them back when he learned that they had been placed 

 very close to the Nation's largest nuclear reactor ! The native resources 

 of the South did come to our rescue, however. 



We used sawdust. Obtained free from a sawmill in Aiken, S.C., 

 and bagged as it came from the chute, we hauled it in great truckloads 

 to the reactor site. The sawdust was too light for our liking, so we 

 piled it into a small mountain and squirted it with a firehose for several 

 days. Drained and stacked around our detector, it provided a fine 

 shield. In recognition of the Southern hospitality which we were 

 enjoying all this time, we also incorporated hominy grits into the 

 shield — a pound of it. ( See pi. 3, fig. 2. ) 



Tested with neutron and gamma ray sources carried around it and 

 placed in various places in it, the shield was fine. It reduced such 

 artificial signals by large amounts. But it made no di-fferenjce to out 

 reactor signal. 



This test, alone, was sujQicient to demonstrate that we were observ- 

 ing antineutrinos from the reactor. 



QUOD ERAT DEMONSTRANDUM 



We were done. For a few days, we enjoyed the knowledge privately 

 that Pauli had guessed correctly as we prepared a report to this effect 

 for publication in the literature and for a summer meeting of the 

 American Physical Society at Yale. The experience of knowing a 

 fact new to mankind and knowing it for awhile all alone is an un- 

 forgettable one. The neutrino existed as an objective, demonstrable 

 fact of nature. The great laws of conservation stood firm. And our 

 small group had had the privilege of sharmg in the work that made 

 them so. 



