منتديات ثانوية الشيخ عامر بريان

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منتديات ثانوية الشيخ عامر بريان

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منتديات ثانوية الشيخ عامر بريان

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    Gone fission Edward Teller

    Admin
    Admin
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    عدد المساهمات : 277
    تاريخ التسجيل : 12/10/2009
    العمر : 31
    الموقع : ليدو - الجزائر العاصمة حاليا

    Gone fission Edward Teller Empty Gone fission Edward Teller

    مُساهمة من طرف Admin الإثنين يونيو 14, 2010 9:08 pm

    Enter the time warp

    To understand the difficulty of
    inventing the
    H-bomb, take a mental journey to 1945. Atomic ("fission")
    bombs have
    just closed World War II with a double-bang. For more than
    two years,
    Los Alamos, New Mexico has been world headquarters for
    physicists,
    home to the intense intellectual debates and frantic
    engineering needed
    to build the atomic bomb. Gone fission Edward Teller NagasakiBut
    the exhilaration at Los Alamos is soured by the
    realization that
    the "project" has killed more than 100,000 people and
    forever tipped
    the military balance toward offense. A week after
    Nagasaki, Manhattan
    Project leader J. Robert Oppenheimer is "guilty, weary and
    depressed,
    wondering if the dead at Hiroshima and Nagasaki were not
    luckier
    than the survivors, whose exposure to the bombs would have
    lifetime
    effects," wrote Richard Rhodes in his history of the
    hydrogen bomb.
    The leaders of the bomb project write that "the safety of
    this nation...
    cannot lie wholly or even primarily in its scientific or
    technical
    prowess. It can only be based on making future wars
    impossible"
    (see p. 203, "Dark Sun... " in the bibliography.

    While Los Alamos continues
    working on the
    atomic bomb, and takes faltering steps toward a hydrogen
    bomb, many
    physicists, satisfied that their goal is met and uncertain
    about
    building a hydrogen bomb based on the vastly greater
    energy of fusion,
    return to their universities.


    Fusion
    confusion: the
    terrible terminology of fission and fusion
    Nuclear energy comes
    from two
    distinct sources—fission

    and fusion:
    Fission
    ("splitting") occurs
    when the nucleus of large, unstable atoms, like uranium
    and plutonium,
    break into smaller atoms, releasing energetic radiation
    and neutrons.
    Fission powers the "atomic" bomb that destroyed Hiroshima, and all nuclear power reactors.
    Gone fission Edward Teller Fission_anim
    Fusion
    ("joining") occurs when
    light atoms, primarily isotopes of hydrogen, fuse into
    larger atoms,
    releasing fantastic quantities of energy. Fusion powers
    the sun
    and "hydrogen" bombs, which are called "thermonuclear" for
    the intense
    heat needed to overcome electrical repulsion between
    positively-charged
    hydrogen nuclei. Fusion, however, is extremely difficult
    to control;
    although billions have been spent to tame fusion for
    electricity,
    practical reactors are decades away.

    Gone fission Edward Teller Fusion_anim

    In bombs, the two forms of nuclear
    energy are
    often blended. Most fission bombs are "boosted" with
    fusion fuel.
    All fusion bombs are triggered by fission bombs, and most
    contain
    a second fission bomb, called a "spark plug."

    In 1946, Edward Teller departs for the
    University
    of Chicago. One of several brilliant Hungarian refugees who
    contributed
    mightily to the atomic bomb, Teller had earned his Ph.D.
    under the
    eminent German physicist Werner Heisenberg and moved to the
    United
    States in 1933, after the Nazis took power in Germany.



    A 'super' bomb?



    Teller's interest in the hydrogen bomb dated to 1941, when Italian
    physicist Enrico Fermi floated the idea. Although the fusion bomb
    (called the 'super') got some attention, leaders of the Manhattan
    Project decided to defer the difficult challenge of fusion until they
    had learned to make a fission weapon from uranium and plutonium. (For
    one thing, fission could be tested in the laboratory, while fusion
    requires conditions more like the center of the sun than the top of a
    New Mexican mesa. And the physicists understood that a fusion bomb would
    need a fission trigger.)


    While the Manhattan Project tried to tackle first things first, Teller
    dwelled on fusing two isotopes of hydrogen --deuterium and tritium.
    (Isotopes are atoms that are chemically identical but have a different
    neutron count and different masses.) "Even during the war he was
    troublesome," says physicist Herbert York. "He wanted to work on fusion,
    but the job was fission, and he quit in a huff several times."
    Under earthly conditions,
    electrical repulsion
    prevents hydrogen nuclei from fusing. In the sun, however,
    enormous
    gravitation squeezes hydrogen nuclei until they fuse into
    helium.
    Gobs of energy are released when a bit of their mass is
    converted
    to energy according to Einstein's famous equation, E=MC2

    (Energy equals mass times the speed of light, squared).

    Gone fission Edward Teller Apache
    The Apache H-bomb test, July, 8,
    1956 on Eniwetok
    atoll. In 1963, health concerns about radioactive fallout
    led to
    a ban on atmospheric testing. Photo:
    Department
    of Energy


    Shocking truth



    Scientists had known since the 1930s about fusion in the sun, but fusion
    refused to be "tamed" into a bomb on Earth, and even after the war,
    fusion was not the focus at Los Alamos. Then the Cold War intensified:
    The 1948 Berlin blockade, the 1949 Soviet atomic bomb test, and the
    start of the Korean war in 1950 created new political realities. In
    1950, President Harry Truman made the H-bomb a national priority.


    In June, 1950, however a long series of calculations proved that
    Teller's super design would fail. The calculations, made in those
    pre-computer days with slide rules and mechanical calculators, were
    incredibly complex, says Carey Sublette, author of Nuclear Weapons
    Frequently Asked Questions and operator of the Nuclear Weapon Archive
    website. "There are a lot of processes involved that could pull the
    outcome in different directions, and all are significant, so you can't
    simplify the problem by assuming things away, as you frequently can do
    in science .... Very complicated computations were needed to chart what
    was going to happen."


    The answer, delivered by mathematician Stanislaw Ulam, was that the
    fusion fuel would either not start fusing, or the fission trigger would
    blow the fuel apart too soon. Then, in January, 1951, Ulam, who had
    immersed himself in matters thermonuclear, suggested using energy from
    the fission bomb to compress, not heat, the fusion fuel.


    Although Teller had long argued "compression does not matter," Ulam
    realized, according to Rhodes, that "Compression works in thermonuclear
    fuels in much the same way it works in fission fuels, squeezing nuclei
    closer together and therefore improving their chances of interacting"
    (Dark Sun, p. 464). Compression also makes the fuel easier to heat with
    thermal radiation and slower to cool, Sublette adds.


    Although Teller soon scented success, shock from the atomic bomb might
    not compress the fuel evenly, and the secondary might still be destroyed
    too soon. So Teller built on Ulam's idea by suggesting that the
    compression could come from thermal X-rays from the primary bomb, not
    the shock wave.
    Gone fission Edward Teller Teller_ulam
    In the Teller-Ulam hydrogen
    bomb design,
    high explosive compresses fission fuel in the "primary"
    stage. Intense
    X-rays from the atomic explosion move through the
    radiation channel,
    vaporizing the uranium pusher-tamper, which acts like an
    inside-out
    rocket, compressing the fusion fuel and spark plug to
    extreme density.
    The spark plug becomes a second fission bomb, heating the
    fusion
    fuel and igniting the fusion reaction. The uranium shield
    protects
    the secondary from destruction while fusion occurs; the
    explosion
    is over in microseconds. Diagram:

    Adapted from Carey Sublette, Nuclear Weapon Archive


    The different was subtle, but critical. Radiation moves at the speed of
    light, much faster than a shock wave, and radiation can be directed to
    compress the fuel evenly from all directions so quickly that fusion can
    occur before the shock wave destroys the secondary.


    Teller then contributed another idea: placing a "spark plug" of uranium
    or plutonium in the center of the fusion stage. The spark plug,
    compressed by the radiation implosion, would fission, heating and
    igniting fusion in the already compressed fusion fuel. The result, the
    "Teller-Ulam" design for a thermonuclear weapon, remains the standard
    design 50 years after it was invented.


    The stage was set for the monster, Mike. On Nov. 1, 1952, the world's
    first hydrogen bomb created a mushroom cloud 100 miles across and proved
    what physicists suspected - that while there was an upper limit to the
    size of fission bombs, hydrogen bombs could be made as big as you
    wished.


    عدل سابقا من قبل Admin في الإثنين يونيو 14, 2010 9:11 pm عدل 1 مرات (السبب : _)
    alilazaal
    alilazaal
    عضو جديد
    عضو جديد


    عدد المساهمات : 9
    تاريخ التسجيل : 15/04/2010

    Gone fission Edward Teller Empty رد: Gone fission Edward Teller

    مُساهمة من طرف alilazaal السبت يونيو 26, 2010 10:07 am

    شكرا جزيلا على الموضوع اريد ان اشارك بموضوع المفاعل النووي الطبيعي
    ليتمكن الانسان من صنع مفاعل نووي، تطلب منه
    الأمر الانتظار حتى القرن
    العشرين... أما الطبيعة فقد تمكنت من صنع مفاعل قبل ما يقارب
    ملياري عام.
    الفيزيائيون الذين يعملون على دراسة هذا المفاعل
    الجيولوجي و الذي تم
    اكتشافه في العام 1972 في الغابون بإفريقيا، تمكنوا من تحديد كيفية عمله.
    الباحث أليكساندر ميشيك من جامعة واشنطن في سانت لويس و مجموعة من
    زملاءه أوضحوا أن مياه الأنهار بجريانها على قاع النهر الصخري الغني
    باليورانيوم عملت كأنابيب التحكم الخاصة بالمفاعل زائدًة بهذا من فعالية
    انشطار
    ذراته دافع ً ة اليورانيوم نحو القيام بالتفاعل المتسلسل. التفاعل بدوره
    أنتج حرارة
    أدت الى غليان الماء... وبتبخر الماء بالكامل توقف التفاعل... بمرور الزمن،
    كانت كميات أخرى من الماء تصل معيدًة إحياء العملية من جديد.
    المشع و الذي هو أحد نتائج التفاعل
    بتحليل عنصر
    الزينون(
    xenon)، و صل
    الفريق الى معرفة أنه و لفترة زمنية تقارب 150 مليون سنه كان المفاعل يعمل
    لمدة 30 دقيقة كل ساعتين و من ثم يتوقف. هذا الاكتشاف يؤكد أن القوانين
    الفيزيائية كانت قبل ملياري عام تعمل بنفس الطريقة التي تعمل بها الآن


      الوقت/التاريخ الآن هو الخميس مارس 28, 2024 11:24 pm