Nuclear Threat Midterm

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How many nuclear weapons has the world made?

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How many nuclear weapons has the world made?


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What was the peak number of nuclear weapons in the world’s arsenal?


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What year was the peak of nuclear weapons in the world’s arsenal?


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the five countries the UN allows to have nuclear weapons

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countries in P-5

U.S., U.K., Russia, China, France

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the countries that presently have nuclear weapons

U.S., U.K., Russia, China, France, Pakistan, India, North Korea, Israel

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What countries have divested themselves of nuclear weapons?

Ukraine, Belarus, Kazakhstan, South Africa

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What countries have nuclear weapons outside of the non-proliferation treaty?

Pakistan, North Korea, India

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What country has never tested nuclear weapons, but is presumed to have them?


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What NATO allies is United States known to have provided weapons for nuclear sharing?

France, U.K

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How many nuclear warheads do the nuclear-armed state possess presently, and what two countries have over 90% of these?


U.S., Russia

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What does “atomos” mean?

greek word for atom

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Know the structure and components of an atom and nucleus.

Nucleons (protons and neutrons) compose nucleus; electrons surround nucleus

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positive charge

same mass as neutrons


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neutral/no charge

same mass as proton


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negative charge

much lighter compared to nucleus

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Atomic Number

number of protons


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Atomic Mass

number of protons and neutrons


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Nucleon Number

number of protons and neutrons

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Same number of protons and neutrons, same atomic mass

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Same number of protons, different number of neutrons, different atomic mass

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What is the heaviest naturally occurring element?


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<p>Understand picture</p>

Understand picture

same Z and A= same element

Different A

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In what sequence were protons, neutrons, and electrons discovered?

electrons, protons, neutrons

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Who discovered the electron

J. J. Thomson

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Plum Pudding Model

  1. developed by J.J. Thomson

  2. Discovered cathode rays are electrons

  3. Proposed negative electrons surrounded by a positive cloud

  4. This was a reasonable guess at the time because, Thomson discovered electrons first, so he knew there had to be a positive

  5. There were problems with this because it could not explain the stability of an atom, i.e., how a positive charge in the atom holds the negatively charged electrons. It could not explain the position of the nucleus in an atom and the scattering of alpha particles.

<ol><li><p>developed by J.J. Thomson</p></li><li><p>Discovered cathode rays are electrons</p></li><li><p>Proposed negative electrons surrounded by a positive cloud</p></li><li><p>This was a reasonable guess at the time because, Thomson discovered electrons first, so he knew there had to be a positive</p></li><li><p>There were problems with this because it could not explain the stability of an atom, i.e., how a positive charge in the atom holds the negatively charged electrons. It could not explain the position of the nucleus in an atom and the scattering of alpha particles.</p></li></ol>
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Solar System Model

  1. Developed by Ernest Rutherford

  2. direct alpha particles (atomic mass = 2 protons + 2 neutrons = 4) at thin gold foil

  3. concluded the nucleus has a compact positive charge and is surrounded by negatively charged electrons

  4. This was reasonable guess at the time because “solar system” model represents an atom as a massive positive body which is the nucleus (like the sun in the solar system) with negative entities which are the electrons (like the planets in the solar system) orbiting around it

  5. There were problems with this because it was inconsistent with existing observations a. Inherent instability b. Discrete spectra i. Predicts continuous spectra, but discrete line spectra observed ii. he couldn't explain why negatively charged electrons remain in orbit when they should instantly fall into the positively charged nucleus

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Shell Model

  1. Developed by Niels Bohr in 1913

  2. Bohr proposed quantized description of atom, electrons only occupy certain discrete orbits, or energy levels; electrons give or take energy only when they change their energy levels; lines in the spectra of gases formed by the transitions of electrons to and from various energy-levels a. Much of chemistry is valence electron physics

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Gold Foil Experiment

beam of alpha particles was aimed at a piece of gold foil; most alpha particles passed through the foil, but a few were scattered backward.

Ernest Rutherford

This was significant because it showed that the atom is mostly empty space with some negatively charged electrons surrounding a tiny positive nucleus

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Whose name is attached to the “annus mirabli” of 1905?  What (as far as we are concerned) is the equation that was theorized?

Albert Einstein


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How does the mass of the components of an atom compare to the composite nuclear mass?

The mass of the nucleus of about 1% smaller than the mass of its individual protons and neutrons

This is because a very small amount of mass may be converted into a very large amount of energy

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Mass defect

difference between individual protons and neutrons and mass of nucleus

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binding energy

the energy released when the nucleons (protons and neutrons) are bound together to form the nucleus

Determines which nuclei are stable and how much energy is released in a nuclear reaction

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What is the relative size, in tons, of your average conventional (valence electron) bomb?

10 tons of TNT

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What is the relative size, in tons, of your average nuclear (U or Pu) bomb?

more than 10,000 tons of TNT

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What is the relative size, in tons, of your average thermonuclear (H) bombs?

more than 10,000,000 tons of TNT

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Electromagnetic Force

o   Long-range

o   ~10^38

o   Acts between charges

o   Describes atomic interactions

o   Atoms, chemistry, light, electronics

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Strong Nuclear Force

o   Short-range

o   10^40

o   Holds nucleus together

o   Binding of nucleus, nuclear structure

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Weak Force

o   Short-range

o   10^26

o   Describes radioactivity

o   Alpha, beta, gamma decay

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how can a nuclear (composed of only protons and neutrons) ever be stable?

o   Charge repulsion: protons trying to push each other away (repulsive between like charges, acts over great distances); electromagnetic force

o   Binding Energy: mass is converted to energy, in the form of a glue trying to bind nucleus together (attractive both protons and neutrons; 100x stronger, but acts only over very short distances)

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parent nucleus

nuclide before disintegration

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daughter nucleus

nuclide after disintegration

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Disintegration of atomic nuclei; atom trying to reach a more stable nuclear configuration

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Alpha Particle

o  a; a helium-4 nucleus , consisting of two protons and two neutrons, that is emitted in radioactive decay

o   Stopped by paper

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Beta Particle

o   β; are high energy, high speed electrons that are ejected from the nucleus by some radionuclides during a form of radioactive decay called beta-decay, emits one electron

o   Stopped by aluminum

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Gamma Particle

o   gamma ray; y ; a bundle of energy emitted by an excited nucleus

o   Stopped by thick lead

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Alpha Decay

o   a

o   loses 2 protons and 2 neutrons

o   Most massive

o   Least penetrating

<p>o   a</p><p>o   loses 2 protons and 2 neutrons</p><p>o   Most massive</p><p>o   Least penetrating</p>
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Beta Decay

o   β

o   Gain 1 proton, lose 1 neutron

<p>o   β</p><p>o   Gain 1 proton, lose 1 neutron</p>
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Gamma Decay

o   g

o   Gamma ray (high energy light)

o   No mass

o   Least penetrating

<p>o   g</p><p>o   Gamma ray (high energy light)</p><p>o   No mass</p><p>o   Least penetrating</p>
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the changing of one element into another by radioactive decay, nuclear bombardment, or similar processes

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As nuclides get larger, why do they require increasingly more neutrons (relative to protons) to stay more stable?

As the number of protons increases in a nucleus, the repulsive force increases, which tends to break the nucleus apart

So, to keep the nucleus stable, a greater number of neutrons are needed which are neutral in nature

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o   A type of high-energy radiation that has enough energy to remove an electron (negative particle) from an atom or molecule, causing it to become ionized. Ionizing radiation can cause chemical changes in cells and damage DNA

o   X-rays

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o   A type of low-energy radiation that does not have enough energy to remove an electron (negative particle) from an atom or molecule. Non-ionizing radiation includes visible, infrared, and ultraviolet light; microwaves; radio waves; and radiofrequency energy from cell phones

o   Gamma (g) rays

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o   the time required for the amount of radioactive material to decrease by ½

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understand chart

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Mass Defect

mass of the pieces (individual protons and neutrons)- mass of nucleus

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Does E=mc2 apply only to chemical (valence electron) reactions, nuclear reactions, both, or neither?

E=mc2 does not only apply to nuclear reactions, but to all events that release energy

o   It is a universal statement

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Who discovered the proton, and also oversaw the first proven case of artificial transmutation?

Ernest Rutherford discovered the proton

o   He also was the first physicist who oversaw the first proven case of artificial transmutation from one element into another

o   In his experiment he bombards nitrogen gas with alpha particles obtaining atoms of an oxygen isotope and discovered protons.  This transmutation of nitrogen into oxygen is the first artificially induced nuclear reaction

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Who discovered the neutron?

James Chadwick (1932)

o   It was discovered last because neutrons are neutral particles, so the scientists were unable to observe neutrons

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Who first visualized the physics of an atomic bomb, and then filed for a patent on it?

Leo Szilard

o   Filed for patent in July 1934

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Fission Reaction

o   Breaks something in half/ splitting nucleus

o   U, Pu

o   nuclear

<p>o   Breaks something in half/ splitting nucleus</p><p>o   U, Pu</p><p>o   nuclear</p>
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Fusion Reaction

o   Two things combine / combining nuclei

o   H

<p>o   Two things combine / combining nuclei</p><p>o   H</p>
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Gaseous Diffusion

Chien-Shiung Wu

o   Used for Manhattan Project

o   Porous barrier

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o   Used for Manhattan Project

o   Mass spectrometer

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Liquid Thermal Diffusion

o   Not used for Manhattan Project because it was not efficient enough

o   convection

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o   Not used for Manhattan Project because scientists could not get them to work efficiently enough

o   Rapid spinning

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Geiger-Müller (G-M)

o   tube consists of a negatively charged cylinder containing a mixture of gasses as well as a wire. The wire runs from the center of the tube through a power supply and scalar counter. The positive ions move towards the negatively charged casing. Similarly, the negatively charged ions move towards the positively charged center wire within the tube. As the current travels through the scaler counter (needle flicker) counts are recorded

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Frisch-Peierls Memorandum (1940)

o   Sent to Henry Tizard (chairman of the most important scientific committee in British war effort)

o   Calculates atomic weapon only needs a few pounds of U-235 (critical mass)

o   Also anticipates strategic and moral implications (radiation, fallout)

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MAUD Report (1941)

o   Henry Tizard sets up MAUD Committee

§  British scientific working group established to perform the research required to determine if an atomic bomb was feasible.

o   Concludes creating atomic bomb is feasible

o   Recommends this be given highest priority because of Nazi fear

o   Pushing collaboration with U.S.

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At what facility was the uranium enrichment done, and why was it located there?

Oak Ridge, TN

Groves wanted to ensure that the Manhattan Project kept a low profile, and Oak Ridge's rural location definitely fit the bill

o   The fact that Tennessee is a landlocked state located away from the coast reduced the chance that the Germans or Japanese would be able to bomb the nuclear site

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At what facility was the plutonium production, and why was it located there?

Hanford, WA

Hanford’s flat, arid environment was perfectly suited to the project’s needs

o   The Hanford Site was viewed as an isolated wasteland, remote from population centers, that could be used indiscriminately for national defense or natural resource extraction purposes

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CP-1 atomic pile

o   Group at Chicago led by Enrico Fermi achieves first self-sustaining nuclear reaction: CP-1 goes critical (Dec 2, 1942)

o   Significance

§  Showed proof of concept

·       Proof of concept got them more $

§  Pile was plans of first nuclear reactor

§  Helped people understand fission

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Franck Report (1945)

o   sent to Secretary of War Stimson

o   from 7 atomic scientists working at UChicago: an early unannounced attack on Japan would be inadvisable

o   Lobbies for a demonstration of the bomb to Japanese representatives

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What was the Uranium Committee (aka Briggs Committee, aka Uranium Advisory Committee) tasked to do?

o   Roosevelt*,* in response to Einstein letter encourages further research into U fission; creates Uranium Advisory (Briggs) Committee

o   Lyman J. Briggs, head

o   Met for the first time on October 21, 1939 including both civilian and military representation

o   Tasked to look into the current state of research on uranium and recommend an appropriate role for the federal government

o   Bush reorganized Uranium Advisory (Briggs) Committee into scientific body

§  More direct access to money for nuclear research

§  Foreign-born scientists barred from committee membership

§  Censored publication of articles on uranium research

§  now became Office of Scientific Research and Development Section on Uranium, codenamed S-1, retains programmatic responsibilities for U research; recommends that all four isotope separation methods and the chain reaction work continue

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Neutron moderator

o   a type of material in a nuclear reactor that work to slow down the fast neutrons (produced by splitting atoms in fissile compounds like uranium-235), to make them more effective in the fission chain reaction

o   Fermi idea: mixture of moderator (graphite) and natural U could produce a self-sustaining fission chain reaction

o   If so, a “pile” containing large amount of natural uranium could produce enough secondary neutrons to keep a reaction going

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Tube Alloy

British atomic bomb project

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What is the origin of “Manhattan” in the Manhattan Project?

its first offices were actually in Manhattan, at 270 Broadway

General Leslie R. Groves, who was appointed to head the project, decided to follow the custom of naming Corps of Engineers districts for the city in which they are located

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o   Chain reaction stops

o   when energy release decreases and the reaction soon halts

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o   when energy is released at a steady rate

o   nuclear reactor

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o   when energy release grows rapidly and may lead to a nuclear explosion

o   nuclear bomb

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Where was the bomb created?  Where was the first bomb detonated?

The bomb was created in Los Alamos, New Mexico

The bomb was first denotated at a site located 210 miles south of Los Alamos, New Mexico, on the plains of the Alamogordo Bombing Range, known as the Jornada del Muerto

o   The code name for the test was "Trinity."

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On the binding energy curve, which area relates to fission, and which to fusion?

On the binding energy curve, Fe-56 is the isotope that separates fusion reactions on the left side of the curve and fission reactions on the right side of the curve

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Which element is the most tightly bound, meaning that you can’t get energy out of it via fission or fusion?

Fe (iron)

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Roughly how many people were in Los Alamos supporting work on the Manhattan Project?


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Gun-type (Little Boy)

uranium design


<p>uranium design</p><p>Hiroshima</p>
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Implosion-type (Fat Man)

o   eventually used for plutonium bomb

o   technically extremely challenging

o   second designed needed because Pu couldn’t be used in the gun-typr

o   the largest technical challenge with the second design

§  inverted shock wave

o   how was it solved

§  obtain symmetry implosion

§  Seth Neddermeyer; George Kistiakowsky

<p>o   eventually used for plutonium bomb</p><p>o   technically extremely challenging</p><p>o   second designed needed because Pu couldn’t be used in the gun-typr</p><p>o   the largest technical challenge with the second design</p><p>§  inverted shock wave</p><p>o   how was it solved</p><p>§  obtain symmetry implosion</p><p>§  Seth Neddermeyer; George Kistiakowsky</p>
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What is the percentage of U-235 and U-238 isotopes in natural uranium?

o   contains 0.7% of the U-235 isotope

o   the remaining 99.3% is mostly the U-238 isotope which does not contribute directly to the fission

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What is the percentage of U-235 and U-238 isotopes in “reactor grade”, low-enriched uranium (LEU)?

o   contains a uranium concentration between 0.711 percent and 20 percent

o   Most commercial reactor fuel uses low enriched uranium (LEU) enriched to between 3 percent and 5 percent 235U. Uranium between 3 and 5 percent 235U is sometimes referred to as “reactor-grade uranium.”

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What percentage of Highly Enriched Uranium (HEU) is U-235

o   More than or equal to 20% U-235

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What percentage of Weapons Grade HEU is U-235?

o   More than or equal to 90% (US uses ≥ 93.5%)

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What was project “Alsos”, and what did it find?

o   was an organized effort by a team of British and United States military, scientific, and intelligence personnel to discover enemy scientific developments during World War II

o   mission reaches Strassbourg, site of German A-bomb project

o   found documents implying German's had made minimal progress towards a bomb

o   German scientists (Werner Heisenberg, Otto Hahn, Max von Laue,…) captured and interned in Farm Hill, England

o   By the end of 1944 it is clear that the A-bomb (if used) will not be used against Germany, but rather Japan

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What was the local name for the site of the first test, and what did Oppenheimer christen it?

Jornada del Muerto local name of first test site

o   Southern NM

o   ~200 miles S of Los Alamos

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What did Oppenheimer christen the site for the first test?

Oppenheimer christens it Trinity

o   Inspiration for name from Sonnet by John Donne, 17th century

§  English poet

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Describe the symbolism within the Trinity badge.

White cloud

o   Blast/mushroom cloud

o   Blast initially reddish/brownish

Yellow circle with crack

o   Earthquake that bomb causes

<p>White cloud</p><p>o   Blast/mushroom cloud</p><p>o   Blast initially reddish/brownish</p><p>Yellow circle with crack</p><p>o   Earthquake that bomb causes</p>
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What was Jumbo

o   Massive cylindrical steel container; Its production was ordered ($12 million)

o   Concerns that the test would not be a success - plutonium core to be imploded inside Jumbo.

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Why was Jumbo made

o   Purpose: in the event that the Gadget “fizzled,” or did not properly detonate, Jumbo would preserve the plutonium

o   By the time final preparations for the test were underway, scientists were confident that the test would work and so Jumbo was not used

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What is the glassy residue left on the desert floor after the Trinity test known as?


o   Fireball touched ground, vaporizes soil causing heavy radioactive particles which precipitate our of cloud as “fallout”

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What was the Potsdam Declaration?

o   Declaration from three largest Pacific allies demanding immediate surrender or face “prompt and utter destruction”

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What was Stalin’s reaction to the Potsdam Declaration?

On July 24 Truman casually mentioned to Stalin that the U.S. had a new weapon of unusual destructive force. The Russian Premier showed no special interest. All he said was he was glad to hear it and hoped we would make ‘good use of it against the Japanese

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What was the Interim Committee?

o   a secret high-level group created by United States Secretary of War, Henry L. Stimson at the urging of leaders of the Manhattan Project and with the approval of President Harry S. Truman to advise on matters pertaining to nuclear energy (1945)

§  This is a precursor to the Atomic Energy Commission (1946)

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