RE: North by Northwest to Catch a Neutrino in the Act

[Rick_Strickert@radian.com]

Bruce Heinmiller wrote:

	>> "Photographic emulsions are the world's oldest radiation
detection
	>> technique, dating back to 1896 when Henri Becquerel discovered
radiation
	>>  when he accidentally left a piece of uranium ore atop some fresh
film."

	> Wasn't the real "accident" a case of too much cloud cover one
	> day in Paris? 

Henri Becquerel described his discovery in "On the invisible rays emitted by
phosphorescent bodies" [read before the French Academy of Science 2 March
1896 (Comptes Rendus 122, 501 (1896)) translated by Carmen Giunta, see
http://maple.lemoyne.edu/~giunta/becquerel.html
<http://maple.lemoyne.edu/~giunta/becquerel.html> ]

	Here is how I was led to make this observation: among the preceding
experiments, some had been prepared on Wednesday the 26th and Thursday the
27th of February, and since the sun was out only intermittently on these
days, I kept the apparatuses prepared and returned the cases to the darkness
of a bureau drawer, leaving in place the crusts of the uranium salt. Since
the sun did not come out in the following days, I developed the photographic
plates on the 1st of March, expecting to find the images very weak. Instead
the silhouettes appeared with great intensity. I immediately thought that
the action had to continue in darkness, and I arranged the following
experiment:

	At the bottom of a box of opaque cardboard I placed a photographic
plate; then, on the sensitive side I put a crust of the uranium salt, a
convex crust which only touched the bromide emulsion at a few points; then,
alongside, I placed on the same plate another crust of the same salt but
separated from the bromide emulsion by a thin pane of glass; this operation
was carried out in the darkroom, then the box was shut, then enclosed in
another cardboard box, and finally put in a drawer.

	I did the same with the case closed by a plate of aluminum in which
I put a photographic plate and then on the outside a crust of the uranium
salt. The whole was enclosed in an opaque box, and then in a drawer. After
five hours, I developed the plates, and the silhouettes of the crystalline
crusts appeared in black as in the previous experiments and as if they had
been rendered phosphorescent by light. For the crust placed directly on the
emulsion, there was scarcely a difference in effect between the points of
contact and the parts of the crust which remained about a millimeter away
from the emulsion; the difference can be attributed to the different
distance from the source of the active rays. The effect from the crust
placed on a pane of glass was very slightly attenuated, but the shape of the
crust was very well reproduced. Finally, through the sheet of aluminum, the
effect was considerably weaker, but nonetheless very clear.

Rick

Richard G. Strickert, Ph.D.
P.O. Box 201088  Austin, TX 78720  (Mailing Address)
14046 Summit Park, Building B, Austin, TX 78728  (Shipping Address)
512-310-5259 (Phone)
512-244-0855 (Fax)
rick_strickert@radian.com <mailto:rick_strickert@radian.com> 

	


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