REPROCUCED AT THE NATIONAL ARCHIVES,
A Remote Observation on the Bikini Tests
, During the recent Bikini tests, measurements were obtained on the background of radiation at Ithaca, New York,
A
Geiger counter and associated recording equipment was set up on
the next-to-the-top floor of the Physics Laboratory at Cornell
University.
The counter was run continuously, and readings on
the accumulated number of counta were taken periodically, on
the average about two readings per day.
‘The experiment was set
up rather hurriedly, and no provision for checking the oalibra-~
tion of the counter with a standard source was made.
The counter was one which had been designed and constructed by Rossi and Greisen for cosmia ray measurements,
active volume was 4 cm in diameter and 19 cm long.
exhibited about a 4 per cent rise per 100 volts,
The
The plateau
The high volt-
are supply and scaling oircuit were of the type used at the Los
Alamos laboratories; their operation seamed to be very reliable
during the observation pertod,
The results of the measurements are plotted in the
accompanying graphs,
In both rraphs the counting rate is plotted
as a function of the time measured from the time of the "Able"
shot.
The unit of counting rate is 64 counts per minute.
Tho
upper graph is a plot cf all the data; the lower one is an ex~
panded plot of the behavior i-mediately after the "Able" shot.
Professor Greisen has pointed out that the background in this
laboratory is roughly twice the normal cosmic ray background.