Greetings Tom,

Here are some clues to look for on the slide rule image. If you can see the
two rivets on the bottom of the brace, you have a clue that helps. If the
rivets are parallel with the edge of the rule, it is a 4088-3. If the inner
one is higher, it is a 4071 -3. If the rule is fat, it is a 4081-3. <grin>

Regards,

Michael

----- Original Message -----
From: "tpugsley314" <tpugsley@...>
To: <sliderule@yahoogroups.com>
Sent: Friday, March 28, 2003 8:34 PM
Subject: SR Sighting: Fermi Again


> This is from a little booklet about the first atomic pile...(sorry
> about the length)
>
> From "The First Reactor" U.S. Atomic Energy Commission, 1968
>
> At 2:50 the control rod came out another foot. The counters nearly
> jammed, the pen headed off the graph paper. But this was not it.
> Counting ratios and the graph scale had to be changed.
> "Move it six inches," said Fermi at 3:20. Again the change - but again
> the leveling off. Five minutes later, Fermi called: "Pull it out
> another foot."
> Weil withdrew the rod.
> "This is going to do it, Fermi said to Compton, standing at his side,
> "Now it will become self-sustaining. The trace will climb and
> continue to climb. It will not level off."
> Fermi computed the rate of rise of the neutron counts over a minute
> period. He silently, grim-faced, ran through some calculations on his
> slide rule.
>
> In about a minute he again computed the rate of rise. If the rate was
> constant and remained so, he would know the reaction was
> self-sustaining. His fingers operated the slide with lightning speed.
> Characteristically, he turned the rule over and jotted down some
> figures on its ivory back.
>
> Three minutes later he again computed the rate of rise neutron count.
> The group on the balcony had by now crowded in to get an eye on the
> instruments, those behind craning their necks to be sure they would
> know the very instant history was made. In the background could be
> heard Wilcox Overbeck calling out the neutron count over an
> annunciator systern. Leona Marshall (the only girl present),
> Anderson, and William Sturm were recording the readings from the
> instruments. By this time the click of the counters was too fast for
> the human ear. The clickety-click was now a steady brrrrr. Fermi,
> unmoved, unruffled, continued his computations.
>
>
> The Curve is Exponential
>
> "I couldn't see the instruments," said Weil. "I had to watch Fermi
> every second, waiting for orders. His face was motionless. His eyes
> darted from one dial to another. His expression was so calm it was
> hard. But suddenly, his whole face broke into a broad smile."
> Fermi closed his slide rule -
> "The reaction is self-sustaining," he announced quietly, happily.
> "The curve is exponential."
> The group tensely watched for twenty-eight minutes while the world's
> first nuclear chain reactor operated.
> The upward movement of the pen was leaving a straight line. There was
> no change to indicate a leveling off. This was it.
> "O.K., 'Zip, in," called Fermi to Zinn who controlled that rod. The
> time was 3:53 p.m. Abruptly, the counters slowed down, the pen slid
> down across the paper. It was all over.
> Man had initiated a self-sustaining nuclear reaction - and then
> stopped it. He had released the energy of the atom's nucleus and
> controlled that energy.
>
>
> In the same booklet is a photograph of Laura and Enrico Fermi sitting
> at a table, both looking at the slide rule in Enrico's hands. It is a
> duplex, probably K&E, with apparently the dark wood (mahogany?).
>
> Fun stuff!
>
> Tom Pugsley
>
>
>
>
>
>
>
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>