Физики шутят
У физиков своя история про бор. Вот она в исполнении Ганса Бете, который, вероятно, ее родоначальник (обычно ссылаются на него):
...Walter Bothe, the leading experimental nuclear physicist in Germany, did the crucial experiment and concluded that carbon in the form of graphite would not work. In America, Enrico Fermi did a similar experiment and concluded that graphite was marginal. He suspected that an impurity in the graphite was responsible for the problem. Leo Szilard, who was working alongside Fermi, had studied chemical engineering before going into physics. He remembered that electrodes of boron carbide were commonly used in the manufacture of graphite. It was known that one atom of boron absorbs about as many slow neutrons as 100 000 atoms of carbon. Very small boron impurities would "poison" the graphite for use as a nuclear reaction moderator. Szilard therefore went around to the American graphite manufacturers and convinced one of them to make boron-free graphite.
...Despite the shortage of heavy water, Heisenberg continued to work toward a chain reaction to the very end of the war. What else could he have done? Graphite was not an alternative; he had no reason to doubt Bothe's measurement. Bothe was the recognized authority in the field and Germans believed strongly in authority. Even if another German had repeated the experiment, the result would have been unchanged. No German physicist would have consulted a chemical engineer: The barrier between the two disciplines was too great. http://www-personal.umich.edu/~sanders/214/other/news/Bethe.html
Рассказ содержит зерно истины: гений Ферми и Сциларда был и в том, чтобы не ломать дрова, а поговорить со знающими людьми. Тут добрым молодцам урок.
Более занятно утверждение Бете про карбид бора. Дело в том, что этот материал НИКОГДА не используется, не использовался, и не может быть использован как электрод для производства графита: бор и углерод дают эвтектику с температурой плавления на 500 градусов ниже температуры, при которой кристаллизуется графит (и даже B4C плавится при температуре существенно ниже необходимой). Да и зачем использовать такие электроды, если графит проводит ток? Карбид бора не имеет отношения к проблеме вообще, и это можно обнаружить за 15 минут, пролистав любую монографию по ядерному графиту. Я слышал эту историю в изложении самых известных физиков - ни один из них не задумался об очевидной неувязке. Что тут можно сказать...
Почему в ударные сроки на минимальном бюджете был построен реактор в Америке? Потому, что графитом занимался Сцилард и Вигнер, которые хорошо знали химию, а не Ганс Бете. Oн выступил бы на этой стезе не лучше, чем Ботэ с Гейзенбергом. Когда он пишет, что немецкий физик никогда бы не снизошел бы до консультации с химиком-инженером, это он о себе говорит, тут же демонстрируя справедливость изречения показательным примером.
PS. У инженеров, между прочим, своя легенда об исторической встрече:
...Vic Hammister was the senior scientist at the research laboratories of National Carbon Company in Cleveland, Ohio, and H.G. MacPherson was his associate. Their destination, Pupin Laboratory of Physics, sat at the northwest comer of the Columbia University campus; the building was some 16 or so stories high. In the basement of Pupin, J.R. Dunning and his cyclotron were busy measuring cross-sections of everything in any way he could devise. The next three floors were classrooms; but from there on up the floors were all classified secret and busy with work for the Manhattan Project. Armed with their new passes, Vie and Mac were admitted to the guarded elevator that took them to the fourth floor. And here they were met by Enrico Fermi and Leo Szilard and quickly ushered into the presence of a squat pile of graphite bricks standing perhaps three feet high and still abuilding. Fermi, with his usual enthusiasm, began to discourse on neutron moderation, the purpose of the pile of graphite, and the lattice of uranium pellets inside. But this was lost on Vie Hammister; he had quite a different worry. “Tell me, Dr. Fermi,” he interrupted, “do you know what the permissible floor loading is?” Fermi did not, but the impact of the question was not lost on him. A quick call to the buildings and grounds engineer and a few calculations on the back of an envelope were sufficient. The next day the graphite was shipped to the Metallugical Laboratory at the University of Chicago and ultimately found its way to Stagg Field. https://dl.dropboxusercontent.com/u/43807687/physics/nuclear%20graphite%20story%201981.pdf
...Walter Bothe, the leading experimental nuclear physicist in Germany, did the crucial experiment and concluded that carbon in the form of graphite would not work. In America, Enrico Fermi did a similar experiment and concluded that graphite was marginal. He suspected that an impurity in the graphite was responsible for the problem. Leo Szilard, who was working alongside Fermi, had studied chemical engineering before going into physics. He remembered that electrodes of boron carbide were commonly used in the manufacture of graphite. It was known that one atom of boron absorbs about as many slow neutrons as 100 000 atoms of carbon. Very small boron impurities would "poison" the graphite for use as a nuclear reaction moderator. Szilard therefore went around to the American graphite manufacturers and convinced one of them to make boron-free graphite.
...Despite the shortage of heavy water, Heisenberg continued to work toward a chain reaction to the very end of the war. What else could he have done? Graphite was not an alternative; he had no reason to doubt Bothe's measurement. Bothe was the recognized authority in the field and Germans believed strongly in authority. Even if another German had repeated the experiment, the result would have been unchanged. No German physicist would have consulted a chemical engineer: The barrier between the two disciplines was too great. http://www-personal.umich.edu/~sanders/214/other/news/Bethe.html
Рассказ содержит зерно истины: гений Ферми и Сциларда был и в том, чтобы не ломать дрова, а поговорить со знающими людьми. Тут добрым молодцам урок.
Более занятно утверждение Бете про карбид бора. Дело в том, что этот материал НИКОГДА не используется, не использовался, и не может быть использован как электрод для производства графита: бор и углерод дают эвтектику с температурой плавления на 500 градусов ниже температуры, при которой кристаллизуется графит (и даже B4C плавится при температуре существенно ниже необходимой). Да и зачем использовать такие электроды, если графит проводит ток? Карбид бора не имеет отношения к проблеме вообще, и это можно обнаружить за 15 минут, пролистав любую монографию по ядерному графиту. Я слышал эту историю в изложении самых известных физиков - ни один из них не задумался об очевидной неувязке. Что тут можно сказать...
Почему в ударные сроки на минимальном бюджете был построен реактор в Америке? Потому, что графитом занимался Сцилард и Вигнер, которые хорошо знали химию, а не Ганс Бете. Oн выступил бы на этой стезе не лучше, чем Ботэ с Гейзенбергом. Когда он пишет, что немецкий физик никогда бы не снизошел бы до консультации с химиком-инженером, это он о себе говорит, тут же демонстрируя справедливость изречения показательным примером.
PS. У инженеров, между прочим, своя легенда об исторической встрече:
...Vic Hammister was the senior scientist at the research laboratories of National Carbon Company in Cleveland, Ohio, and H.G. MacPherson was his associate. Their destination, Pupin Laboratory of Physics, sat at the northwest comer of the Columbia University campus; the building was some 16 or so stories high. In the basement of Pupin, J.R. Dunning and his cyclotron were busy measuring cross-sections of everything in any way he could devise. The next three floors were classrooms; but from there on up the floors were all classified secret and busy with work for the Manhattan Project. Armed with their new passes, Vie and Mac were admitted to the guarded elevator that took them to the fourth floor. And here they were met by Enrico Fermi and Leo Szilard and quickly ushered into the presence of a squat pile of graphite bricks standing perhaps three feet high and still abuilding. Fermi, with his usual enthusiasm, began to discourse on neutron moderation, the purpose of the pile of graphite, and the lattice of uranium pellets inside. But this was lost on Vie Hammister; he had quite a different worry. “Tell me, Dr. Fermi,” he interrupted, “do you know what the permissible floor loading is?” Fermi did not, but the impact of the question was not lost on him. A quick call to the buildings and grounds engineer and a few calculations on the back of an envelope were sufficient. The next day the graphite was shipped to the Metallugical Laboratory at the University of Chicago and ultimately found its way to Stagg Field. https://dl.dropboxusercontent.com/u/43807687/physics/nuclear%20graphite%20story%201981.pdf