Thirty years at Pajarito Canyon Site Page: 4 of 51

THIRTY YEARS AT PAJARITO CANYON SITE

PROLOGUE
In her House at OtowiBridge, Peggy Pond Church tells of two years in Pajarito Can-
yon at her father's dude ranch, the Pajarito Club.' The location, where the Canyon
broadens just below a fork, is the Pajarito Canyon Site of the present account. The Club
was abandoned in 1916 when its water supply, a spring that fed a small stream, dried up
- reminiscent of the much earlier history of the Canyon's Indian ruins.? A log cabin
that actually predates the Club is still standing, and a nearly obscured sawdust pile
shows that there had been a sawmill at some time.
The first use of the Pajarito Canyon by The Los Alamos Laboratory, as it was
originally named, was by the Radioactivity Group in mid-1943.' The choice of this out-
lying Site for a field station was to avoid the radiation background arising from other
Laboratory activities. A year or so later, this Group moved to the East Gate Laboratory
that was set up specifically for spontaneous fission measurements.
In late 1944, the Site was adapted as a proving ground for the so-called "magnetic
method" of diagnosing implosions. Three earth-covered bunkers are the only remaining
evidence of that acitivity, which was abandoned before the end of 1945.
Finally, work with critical assemblies was moved from the Omega Laboratory to the
Pajarito Site in April 1946.' Although this followed the fatal radiation injury of Harry
Daghlian, urgently required critical assemblies were still manipulated by hand until
Louis Slotin suffered the same fate about a year later. In each case, a component of the
assembly slipped into a more reactive position, producing a superprompt-critical pulse
of radiation. This second accident outlawed hand operation, thus increasing the
urgency of need for a facility for remotely controlled critical assemblies. Because of its
remoteness and existing rudimentary buildings, Pajarito Canyon remained the favored
location for this new facility, which was rushed to completion in 1947. This brings us to
the beginning of the thirty years during which activities at The Pajarito Canyon Site
have evolved systematically.
BEFORE ROVER
In the course of numerous changes of activities and groups at the Pajarito Canyon
Site, the thread of continuity has been the remote-control Critical Experiments
Facility. Originally, this Facility consisted of a critical-assembly laboratory known as
"Kiva" (the ceremonial chamber), located one quarter mile from a control room in an
existing shack. An exclusion area provided radiation protection by keeping people
beyond this distance whenever the remotely controlled critical assemblies were
operated. Guidelines directed toward the safety of operations are described in Appen-
dix C. Except as required directly for critical experiments, the operating Group M-2
was housed in Gamma Building near the Los Alamos townsite.

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Paxton, H.C. Thirty years at Pajarito Canyon Site, report, March 1, 1978; New Mexico. (https://digital.library.unt.edu/ark:/67531/metadc1053423/m1/4/ocr/: accessed May 19, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.

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