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Final Answers
© 2000-2017   Gérard P. Michon, Ph.D.    

     Nuclear Physics

 Coat-of-arms of 
 Ernest Rutherford (1871-1937) 
 Lord Rutherford, first Baron Rutherford of Nelson
All science is either physics
 or stamp collecting
Ernest Rutherford  (1871-1937)

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Related Links (Outside this Site)

The Effects of Nuclear Weapons  pdf  (1950, 1957, 1962, 1964, 1977, 1984)

United Nuclear:  Scientific Equipment & Supplies.

Wikipedia :   Gamma ray (1900)   |   Rutherford scattering (1909)   |   Rutherford model of the atom (1911)

Videos :


From Nuclear Physics to Nuclear Engineering

 Henri Becquerel  
 Polytechnique (2011-09-07)  Radioactivity   (March 1, 1896)
Henri Becquerel's great experimental discovery.

It is important to observe that this phenomenon cannot be attributed to the luminous radiation emitted by phosphorescence.
Henri Becquerel   (1852-1908; X1872; Nobel 1903)

A. Henri Becquerel  belongs to one of the most famous dynasty of French physicists.  He was the grandson of Antoine César Becquerel (1788-1878; X1806), the son of Edmond Becquerel (1820-1891) and the father of Jean Becquerel (1878-1953; X1897)  who discovered the rotation of polarization due to a magnetic field.  Three of them studied at  Polytechnique.  (Edmond didn't, as he chose to become pupil and assistant of his father instead.  In Polytechnique's own records, the remark identifying Henri as  fils de polytechnicien  is thus erroneous).  All four Becquerels held successively the same chair of applied physics, created in 1838 at the Muséum National d'Histoire Naturelle  (founded on 10 June 1793)  and all of them became members of the French  Académie des Sciences.

Potassium Uranyl Sulfate:   K2 [ (UO2) (SO4)2 (H2O) ] (H2O)

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An Unsung Prior Discovery of Radioactivity  (1857) :

Becquerel's celebrated serendipitous discovery was actually made,  39 years before him,  by  Abel Niépce de Saint-Victor (1805-1870)  a younger cousin of  Nicéphore Niépce (1765-1833) the man credited for the invention of photography  (1826).

Although that early discovery was duly heralded as  major  at the time  (1857)  the World was apparently not quite ready for it yet...  By the time of Becquerel's own discovery  (1896)  the previous work of  Niépce de Saint-Victor  had apparently been all but forgotten...

Curiously enough, one of the few noteworthy physicists who  did  notice in due time was Becquerel's own father!  Edmond Becquerel (1820-1891) fully discussed the future discovery of his son in a book he published in 1868  (La lumière, ses causes et ses effets).  At the time, the younger Becquerel was 16 and curious.  It's hard to believe he never read the book of his father.

Videos:   Discovery of Radioactivity (7)   |   Properties of Becquerel Rays (8)

 Marie Curie  Coat-of-arms of 
 Marie Curie
(2011-09-08)  Polonium and Radium  (1898)
New elements discovered by Pierre & Marie Curie.

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Videos:   Discovery of Radioactivity (7)   |   Properties of Becquerel Rays (8)

 Ernest Rutherford  Coat-of-arms of 
 Ernest Rutherford
(2017-06-28)  Lead-Block Experiment  (1899)
Rutherford named 3 types of ionizing radiation.

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Rutherford and Radioactivity  (Purdue University)

(2011-01-19)  Rutherford's Gold-Foil Experiment  (1909)
This experiment was first conducted by Hans Geiger (1882-1945) and Ernest Marsden (1889-1970) under the supervision of Rutherford.

It was almost as incredible as if you fired a 15-inch shell
at a piece of tissue paper and it came back and hit you
  Ernest Rutherford  (1871-1937)

The Geiger-Marsden experiment (1909)  was conducted while Hans Geiger was a student of Rutherford at Manchester.  Ernest Marsden was still an undergraduate student there  (he was a New-Zealander, like Rutherford).

 Ernest Rutherford
Ernest Rutherford
Ernest Rutherford ("Ern") had been awarded a Nobel prize the previous year (1908) for his studies of radioactivity, including the concept of  half-life  and the naming of alpha and beta radiations (1899).  He also coined the term  gamma radiation  (in 1903) for what the Frenchman Paul Villard had discovered in 1900 while studying the decay of radium.  In spite of those early achievements, Rutherford's best work was yet to come...  In 1911, the surprising results of the Geiger-Marsden gold-foil experiment prompted him to posit a model of the atom consisting of a tiny heavy positively-charged nucleus orbited by electrons.

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Video:   Modern re-enactment of the Rutherford Gold Foil Experiment  (Am instead of Ra as am alpha source).

(Yahoo! 2011-01-16)  Energy of alpha particles from Po-210 decay
How close can those  a-particles  approach another polonium nucleus?

Using unabbreviated notations, the nuclear decay involved can be written:

® 206
Pb -2
   +    4
   +   5.4075 MeV

The  a-particle  being the bare nucleus of helium-4  (doubly-ionized atom of helium-4)  the above is commonly written with more compact notations:

Po ® 206
Pb - -
   +   a ++
  +   5.4075 MeV

Table of Relevant (Neutral) Isotopes
ElementA Atomic weight (u)Half-lifeDecay%Q-value (keV)
82Pb206205.974465 278   ¥
84Po210209.982873 673 138.376(2) da 1005407.46(7)

In the main, this may be treated nonrelativistically.  As the initial polonium atom is at rest, the two outgoing particles have opposite momenta and thus share the available total energy in inverse proportion of their masses.  So, the recoiling lead atom gets 1.9% of it and the alpha particle retains  98.1%. 

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Table of Isotopes (LBNL)   >   Education   >   Polonium (Z = 84)   >   Po-210
Atomic Masses   >   AMDC   >   AME   >   Atomic Mass Adjustment (2003)

(2011-01-27)   Energy and Mass Defect:   E = m c 2
The Q-value energy of a nuclear reaction balances the change in mass.

There isn't the slightest indication that energy will
ever be obtainable from the atom.
  [Oops!  1932]
Albert Einstein (1879-1955; Nobel 1921)

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Energy from the Nucleus (9)
Atomic Masses   >   AMDC   >   AME   >   Atomic Mass Adjustment (2003)
Inertia of Energy:  E = m c2.   Einstein Explains his Famous Formula.  Voice of Albert Einstein, 1948.

(2011-01-21)   Standard Decay Modes for Heavy Radioactive Nuclides
Heavy radioactive nuclei decay in the following five standard  modes :

a Decay :

The alpha-decay of an atom is the emission of an  a-particle  from its nucleus  (an Helium-4 nucleus consists of 2 protons and 2 neutrons).  The mass number (A) is decreased by 4 units; the atomic number (Z) is decreased by 2 units.  With a negligible error  (due to the differences in electronic binding energies for helium-4 versus other elements),  the products of a-decay have a mass not less than the combined mass of a neutral helium-4 atom  (namely  4.002603254 u)  and the  (neutral)  isotope of the element two steps down with a mass number four units down.  This implies an inequality among tabulated masses of the istopes which is a necessary  (and almost sufficient)  condition for  a-decay  to occur.  Translated in terms of energy, the positive difference between the aforementioned masses is the so-called  Q-value  for the  a-decay reaction.

e Decay :

e decay is commonly abbreviated EC ("electron capture") in English texts.  It consists in the capture of an orbital electron  (and emission of a neutrino).  One proton of the nucleus  turns into  a neutron; the mass number (A) does not change; the atomic number (Z) is decreased by one.  Besides a neutrino, whose energy can be arbitrarily low, e decay produces only a neutral atom of the previous element (more precisely, the isotope of that element which has the same mass number as the isotope whose decay is being considered).  Thus, an atom can undergo e decay only if it is heavier than the corresponding isotope of the previous element.

b+ Decay :

b+ decay consists in the emission of a positron (and a neutrino).  One proton of the nucleus  turns into  a neutron;  the mass number (A) does not change; the atomic number (Z) is decreased by one.  The decay produces the same nuclear result as e decay but a positron is radiated away and an additional electron remains in the vicinity of the nucleus  (the atom produced is a negative ion instead of a neutral atom for e+).

The binding energy of an electron is less than a few electron-volts; (1 eV being about 0.00000000107 u).  If we neglect that, the above means that b+ decay can only occur for an atom whose mass exceeds that of the corresponding isotope of the previous element by at least two electron masses (i.e. 0.001097 u).

b- Decay :

b- decay consists in the emission of an electron (and an antineutrino).  It used to be known simply as "b decay" before the discovery of the positron (1932).  One neutron of the nucleus  turns into  a proton; the mass number (A) does not change; the atomic number (Z) is increased by one.  Besides the antineutrino, whose energy can be arbitrarily small, b- decay produces only a positive ion and an electron whose combined mass is not less than that of a neutral atom.

Thus, b- decay can occur as soon as the decaying atom is heavier than the corresponding isotope of the next element.

2b- :   There are some (very) long lived radioisotopes like Tellurium-128 or Tellurium-130 for which a single b- decay is impossible but for which near-simultaneous double b- decays (2b-) are allowed because the atom is heavier than the corresponding isotope two elements up.  Thus, the 2b- decay of Te-128 (resp. Te-130) into Xe-128 (resp. Te-130) is rare but possible, whereas the b- decay of Tellurium into Iodine is forbidden.  Other nuclides for which the same remark applies include Ca-48, Ge-76, Mo-100, Xe-136, Ne-150...

Isomeric Transition :

Isomeric Transition  (IT)  is the name given to the decay of a long-lived excited state of the nucleus into an isomeric state of lower energy  (usually, but not always, the ground state).  Such long-lived  metastable  states are normally marked with the suffix "m"  or, if there are several, "m1", "m2", "m3", etc.  During such a decay,  the extra energy and the extra spin  (a whole number of spin quanta)  is carried away by gamma-ray photons.

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Wikipedia :   Ionizing radiation   |   Alpha decay

(2011-01-21)   The four  radioactive series  of heavy nuclides:
Successive decay products of a heavy nucleus stay in one of four series.

Since the above  standard decay modes  either decrease the mass number (A) by 4 units or leave it unchanged, there are 4 standard radioactive  families  or  series.  The mass number modulo 4 is characteristic of each series.

Three of those families are  natural  ones which start with a long-lived parent and end with a stable isotope of lead.  Glenn T. Seaborg was instrumental in establishing artificially the fourth series, which was  extinct :  With a half-life of  only  2.14 million years,  the parent of that series  (Neptunium-237)  has not maintained a native presence on Earth.  Neither has any other member of the  Neptunium series, except for the [two] final one[s]:  Bi-209 [& Tl-205].

As bismuth-209  was once believed to be the heaviest stable nuclide, the news that it is   extremely weakly  radioactive made  headlines in 2003.  The line at  3.14 MeV,  now attributed to the decay of Bi-209 below,  was first observed on the morning of  March 15, 2002,  during calibration of a new scintillating bolometer using bismuth germanate cooled to  20 mK.  Bismuth-209 decays into stable thallium-205 with a record-breaking half-life  (about a billion times the age of the Universe)  first estimated from a total of 128 alpha disintegrations seen over a period of 5 days, using two distinct masses of bismuth  (31 g & 62 g).  The experimental value of  1.9(2) 1019 years  matched predictions around  4.6 1019 years, based on tabulated masses and energies that have since been revised because of this discovery.

Bi ® 205 
Tl  - -
   +   a ++
  +   3.137 MeV

The Four Radioactive Series
NameAParentEnds with...  
Thorium series4nThorium 232...   Lead 208.
Neptunium series4n+1Neptunium 237...   Bismuth 209 (& Thallium-205).
Uranium series4n+2Uranium 238...   Lead 206.
Actinium series4n+3Uranium 235...   Actinium 227, ... , Lead 207.

 Fiesta red bowl, 
 with U-238 glaze

A late 1960's Homer Laughlin Fiesta Ironstone "mango red" bowl, 6.5" in diameter, 1.75" deep. The 0.2 mm glaze owes its color to  UO3, trioxide of depleted uranium.  The  Homer Laughlin Company  of West Virginia used natural uranium until 1943.  Depleted uranium  (0.25% of U-235)  is about 60% less radioactive than the natural uranium originally used for "Fiesta red" (1936) containing about 0.72% of U-235.

Walter Lewin's Dinnerware   |   Fiestaware Radioactivity   |   Family Fiestaware

(2011-01-21)   Other decay modes
Lighter isotopes commonly decay in  nonstandard modes.

One reason why the above concept of radioactive series is of little or no use for lighter elements is that their radioactive isotopes may decay in  nonstandard modes  which need not preserve the mass number modulo 4.

Such modes include the spontaneous emission of a proton or a neutron, spontaneous  fission  into two nuclei  [both bigger than an alpha particle]  or  spallation  into three or more fragments.

(2011-09-07)   Geiger-Müller  Counter
The simplest device to detect ionizing radiation and quantify activity.

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Wikipedia :   Geiger-Müller tube   |   Geiger counter
Single-photon avalanche diode
Illy Sommer video:   Radiation detection with a Geiger-Müller tube

(2011-09-07)   Scintillation  Counters and Spectrometers
Measuring and tallying the energy of individual gamma rays.

scintillator crystal  (e.g., sodium iodide doped with thallium)  produces a flash of visible light whose intensity is  proportional  to the energy of the incoming gamma photon.

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Wikipedia :   Photoelectric effect   |   Secondary emission   |   Photomultiplier tube (PMT)   |   Scintillator
Illy Sommer :   Scintillation detection & Scintillation crystal NaI(Tl)   |   Spectrometer analysis
Mr. Wizard's "Everyday Radioactivity" (1973)  Part 1   |   Part 2  by Don Herbert (1917-2007)

Interesting as it may be, that last educational film isn't part of the celebrated "Mr Wizard" TV series and may not be completely candid...  It was deliberately produced in the educational style of the 1950s and 1960s with a grant from Southern-California Edison.  The barely-readable copyright date on the last frame is MXMLXXIII (1973) which might indicate a specific commission to reassure the public at that particular time...  Especially dubious is the closing comment that spending a year 5 miles from the featured nuclear plant  (San Onofre, operated by Edison)  is like watching color-tv for 8 hours... By the same reasoning, the nuclear plant shown  (photographed from a distance of about 50 yards)  emits 25000 times as much radiation, which is what you'd get by watching 30 color TVs at once.

(2011-08-26)   Cross-section
The apparent size of the target depends on the speed of the projectile.

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Cross-section (Wikipedia)

(2011-02-02)   Artificial Radioactivity  (neutron activation).
Bombarding stable nuclides with neutrons can make them radioactive.

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J. Frédéric Joliot (1900-1958)   |   Irène Joliot-Curie (1897-1956)

(2011-02-02)   Chain Reaction   (December 2, 1942)
Neutron-induced decays release neutrons that induce further decays

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Enrico Fermi (1901-1954)   |   Induced radioactivity
The hardest step in making a nuclear bomb  by nbsp; Bill Hammack,  "the engineer guy".

(2011-02-02)   Critical Mass
The smallest mass that can cause a runaway chain reaction.

The Able nuclear test  (3.5 miles off Bikini Island,  on July 1, 1946)  was the fourth nuclear explosion ever  (the first three were Trinity, Hiroshima and Nagasaki).  Although the test itself didn't cause any casualties, the plutonium core involved  (dubbed the  Demon core)  has previously claimed two lives...

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The Mathematics of the Manhattan Project  by  John F. McGowan, Ph.D.  (2013-07-08).
Critical mass   |   Neutron reflector   |   Beryllium   |   Demon core (6.2 kg Pu-Ga)
Harry Daghlian (1921-1945)   |   Louis Slotin (1910-1946)   |   Tickling the Dragon (movie clip, 1988)

(2011-10-16)   Thermonuclear bombs   (hydrogen bombs, H-bombs)
Nuclear fusion can release much more energy than fission devices.

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Teller-Ulam design   |   Ivy Mike   |   Mark 16   |   Castle Bravo

Alpha (Yahoo! 2011-01-03)   Radiocarbon (C-14) allows carbon dating:
In a dead organism, carbon-14  decays with a half-life of 5730 years.

C ® 14 
N  +
   +    e-
   +   156.46 keV

The above  b decay  occurs for radiocarbon everywhere, including in the carbon dioxide of the air.  However, the concentration of carbon-14 in the atmosphere remains essentially constant because it is replenished by the following action on nitrogen of neutrons that originate from cosmic rays:

n   +    14 
N ® 14 
C  -
   +    p+
   +   625.87 keV

All told, the atmospheric concentration of radiocarbon remains fairly constant but it may vary for several reasons that influence the above production of radio-carbon.  Those factors, listed by increasing order of severity, include:

  • Radiocarbon is primarily produced in the upper atmosphere where it gets oxidized by oxygen.  Radioactive carbon dioxide then diffuses down below  (which means that the concentration of radiocarbon varies a little bit with altitude).
  • The bombardment by neutrons is very sensitive to cosmic circumstances which may vary over time.  This results in some  noise  which limits the precision of carbon dating for relatively young samples, unless some calibration is done using samples of dead things whose history is precisely known by other means.
  • When atmospheric nuclear tests where still allowed, there were times when the concentration of radiocarbon was twice as high in some locations of the Northern Hemisphere compared to reference points in the Southern Hemisphere.  (Mixing of air through the horse latitudes can be particularly slow at times.)  In the distant future, dead plants that grew in the wrong places during that dark period may appear thousands of years too young if this effect is not taken into account.

... / ...

Table of Relevant Isotopes   (neutral elements, unless otherwise specified)
ElementA Atomic weight (u)Half-lifeDecay%Q-value (keV)
0n1   1.008664 91597(43) 879.9(9) sp+100782.33349(41)
1p+1   1.007276 46677(10)   ¥
6C12 12.0   ¥
6C14 14.003241 98870 5730(40) yb- 100156.475(4)
7N14 14.003074 00478   ¥

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Table of Isotopes (LBNL)   >   Carbon-14

Spencer  (Yahoo! 2007-10-27)   Nuclear Fusion  &  Nuclear Synthesis
When two deuterons come together in fusion, mass is lost.  Wassup?

In the fusion of two light nuclei  (like deuterons)  the resulting nucleus has a mass which is  less  than the sum of the masses of the reactants.

The  missing mass  is converted to energy.  The fusion yields a nucleus in an  excited state  which can either release that extra energy directly as gamma rays or split into something else.  For example:

2H  +  2H   ®   4He  +  23.84648 MeV   ®   3He  +  n  +  3.26886 MeV

When two new particles are produced like this, the final release of energy is normally split between them as kinetic energy in inverse proportion of their respective masses.  In this example, as the helion has about 3 times the mass of the neutron, it gets  25%  (817 keV)  and the neutron  75%  (2.45 MeV).

Indeed, in the frame of their center of mass, the momenta of the two particles are opposite and their (nonrelativistic) speeds are thus inversely proportional to their masses, which makes their kinetic energies also inversely proportional to their masses.

Fusing heavier elements  (i.e., elements heavier than  Fe=iron)  requires an input of energy, while the splitting of an heavy nucleus into several lighter pieces (fission) releases energy.  For example fission of a uranium nucleus releases energy.

The fusion of heavy nuclei into heavier ones is only possible in very violent events  (like the supernova explosion of a star)  because there is extra energy floating around which can be absorbed in the process.  This is how all elements heavier than iron were once synthesized from lighter elements  (mostly hydrogen and helium)  of which the early universe was made of.

(2011-08-20)   The Proton-Proton chain fusion process:
What powers the Sun and all stars colder than  15 000 000 K.

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Proton-Proton Fusion  by  Rod Nave

(2011-08-15)   Tokamak Reactors
Igniting fusion by heating a magnetically-confined plasma.

For two positively charged atomic nuclei to fuse, they must come close enough to each other for the attractive nuclear forces to overcome their electric repulsion.  This can only happen if their relative speed exceeds a certain threshold, which can be measured equivalently either in terms of energy or temperature.  The latter is called the  ignition temperature.

The key conversion factor is the reciprocal of  Boltzmann's constant:

1/k   =   11604.5 K/eV

Temperature (K)   =   11604.5  (Charges on the particle)  (Voltage)

The lowest known ignition temperature  (4.5 107 K, or about  4 keV)  is for the fusion of deuterium and tritium  (this fusion cannot occur in a natural star unless some tritium is produced by a prior process with a higher ignition temperature).  As this  "D-T fusion"  seemed easiest to ignite, it became the focus of all Tokamak experiments.

2H +  +  3H +   ®   4He++  +  n  +  17.58925 MeV

The energy of  17.6 MeV  is shared between the particles inversely as their masses:  20%  (3.5 MeV)  for  4He++  and  80%  (14.1 MeV)  for the neutron.

In a magnetically confined plasma, the charged helium nucleus  (alpha particle)  will stay in the plasma and release its energy in it by thermal collisions with other ions.  The neutron, on the other hand, doesn't feel the magnetic confinement and will escape into the  blanket  material around the reactor, which will get hot by absorbing it.  Useful energy from the reactor can be recovered as heat by running a cooling fluid through that  blanket.

Wikipedia :   Tokamak

Adaviel  (Yahoo! 2010-01-24)   Hot Fusion  &  Cold Fusion
At what temperature does nuclear fusion ignite?  Is cold fusion possible?

18 000 000  K

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Focardi and Rossi Press Conference (Italian)  by Sergio Focardi and Andrea Rossi (2011-01-15).

(2011-08-15)   The Farnsworth-Hirsch  fusor  design   (c. 1964)
A well-established way to achieve  nuclear fusion  on a tabletop.

The design presented below is extremely simple and works very well.

The actual construction involves substantial engineering challenges.  However, those have not stopped dozens of amateurs  (including a few high-school students)  from building  homemade  nuclear fusion reactors...

The core is just a spherical cavity containing deuterium under a very low pressure between  5  and  20 microns.  Prior to receiving the deuterium, the cavity is evacuated down to  0.001 or 0.0001 microns  (another possibility might be to flush the cavity with deuterium several times using less extreme pumping).

micron  is defined either as a  millitorr  (mTorr)  or a  micrometer of mercury  (mHg).  Both definitions are used interchangeably in practice  (although the latter is preferred)  since both specify  almost  the same pressure.  The correct equivalence is precisely:

1 mHg    =   0.133322387415  Pa   (exactly)
 =   1.000000142466321243523316... mTorr

1 pascal  (Pa)  is thus very nearly equal to  7.5 microns.  A gas  or plasma in that pressure range is essentially a  high-vacuum.

Inside the cavity are two concentric spherical electrodes.  The wall of the cavity can serve as the outer electrode  (it can be electrically grounded for safety).  The inner electrode, on the other hand, is kept at a large negative potential  -U  of  -10 000 V  or  -30 000 V.

That inner grid must consists of a loose mesh of wire.  It is thus fairly transparent to the positive ions that it attracts  (which will go through it most of the time, at substantial speed).

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Elmore-Tuck-Watson electron accelerator :

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Farnsworth Labs  (later, "ITT Philo Farnsworth Research Corporation")  consisted of never more than  6  engineers working on-site at the Pontiac St. television factory in Fort Wayne, Indiana, until ITT stopped funding the research in 1967.  The original team  (1959)  working on fusors included:

The cataloged Meeks-Farnsworth papers are mostly from 1961 to 1974.

In 1998,  Richard Hull,  the first amateur to achieve nuclear fusion did meet with all four living members of that original team  (Hirsch, Meeks, Haak and Blasing).  Hull did it again with  Paul Schatzkin  around 2004.  Hull and Schatzkin are now coordinating the efforts to keep alive among amateurs the practical knowledge gathered in that era, as explained below.

Farnsworth-Hirsch Fusor (Wikipedia)
The Farnsworth Fusor,  in  "The Farnsworth Chronicles"  by  Gerry Vassilatos  (1995)
US Patent 3258402 by Philo T. Farnsworth (June 1966) for ITT   [ Virtual cathode formed by electrons ]
US Patent 3386883 by Philo T. Farnsworth (June 1968) for ITT   [ Fusor with real transparent cathode ]
US Patent 3530497 by Robert L. Hirsch and Gene A. Meeks (Sept. 1970) for ITT   [ 3 electrodes ]

(2011-08-15)   Polywell design  &  Wiffleball  machines  (WB1 ... WB8)
The brainchild of the late  Dr. Robert W. Bussard (1928-2007).
 Robert Bussard
Robert Bussard
  On 2006-11-09,  Robert Bussard gave an inspirational Google Tech Talk on the fusion reactor that he had been developping since 1987, with Navy funding, at his own company  (EMC2)  where Tom Ligon had assisted him for 5 years.  Bussard passed away only 11 months later, at the age of 79.  However, his Google talk was instrumental in getting his company renewed Navy backing a few weeks before his death.  This allowed research at EMC2 to go on, with a team of 5 people led by Dr. Richard Nebel who was on leave from Los Alamos.

Rick Nebel retired in November 2010 and was suceeded by 41-year-old  Jaeyoung Park  who gave up his position at Los Alamos to focus on the project.  As of May 2011, EMC2 employs 8 or 9 staff members interacting with about two dozen external consultants.

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If/when it becomes practical to use nuclear fusion to generate energy, neutron radiation would become a nuisance.  Aneutronic fusion would be preferred, possibly using Boron-11 in a  500 keV  reaction, known as  "Proton Boron-11"  (p-B11)  and heralded as the  Holy Grail of fusion :

11B  +  1H    ®   12C  +  15.957 MeV
®   8Be  +  4He  +  8.590 MeV
®   3 4He  +  8.682 MeV

A large part of the kinetic energy of the alpha particles so produced  (without any residue or harmful radiation)  could be converted directly into electricity.

Unfortunately,  theoretical arguments  presented by  Todd H. Rider  in his doctoral dissertation at MIT  (1995)  strongly indicate that any plasma outside of thermal equilibrium cannot generate net fusion power because of Bremsstrahlung losses  (even with gridless designs like the Polywell machines).  This applies to all known clean nuclear fuels and, most probably, to other fuels as well.  Allowing the plasma to thermalize seems to make matters only worse.  Here's how Rider saw fit to start his dissertation:

For the record, the author would like to apologize for apparently killing some of the most attractive types of fusion reactors which have been proposed.  He advises future graduate students working on their theses to avoid accidentally demolishing the area of research in which they plan to work after graduation.

Apparently, Bussard never considered that the Bremsstrahlung issue could be a fundamental limitation and kept arguing that the power output of large Polywell machines would scale as the seventh power of their linear size...

Polywell (Wikipedia)   |   IEC Fusion Technology (blog)
Polywell Nuclear Fusion :   Nuclear Reactors Compared
Videos :   Analysis of the Bussard Polywell :   | 1 | 2 | 3 |
Extended Interview with Tom Ligon :   | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
Forum discussions :   Talk-Polywell.org   |   Physics Forums
Should Google go Nuclear?  by  Mark Duncan.
A Fusion Thruster for Space Travel  (John J. Chapman)  by  Willie D. Jones for IEEE Spectrum (August 2011).

(2011-08-13)   Enthusiastic amateur studies in radioactivity
Amateur nuclear physics is a hobby that may puzzle the general public.

   Illy Sommer in 2009
Illy Sommer

From natural radioactivity to fusors...

Here are a few samples of the many videos  (all are nice, some are  great )  of  Illy Sommer  ("bionerd23")  a self-described  radiophile  from Berlin, Germany  (b. 1984).

One of the above topics is the homemade  fusor  (i.e., fusion reactor)  built by  Jon Rosenstiel  of Anaheim, California.  Jon's fusor holds the record in amateur nuclear fusion, with more than 10 million neutrons per second.  Such devices are arguably the most advanced type of nuclear contraptions that have been successfully duplicated by independent amateurs.

 Tom Ligon
Thomas Ligon
  The amateur fusion movement began in 1997 when  Tom Ligon, the assistant of Robert Bussard, decided to stir up interest in nuclear fusion among the  Tesla Coil Builders Of Richmond  (TCBOR)  at a  Teslathon  organized by  Richard Hull  in Richmond, VA.  In a matter of weeks, Hull had built his own  fusor  and other amateurs weren't far behind...    Richard Hull
Richard Hull

With  Paul Schatzkin  ("The Perfesser")  Richard Hull  now runs  fusor.net,  where all  fusioneers  congregate  (including Tom Ligon).  Hull maintains a list of known experimenters at various stages of their own  fusor  projects :

  • Scroungers  who have declared their intentions to gather components.
  • Plasma Club  members have obtained preliminary functionality.
  • Members of the  Neutron Club  have achieved fusion and measured it.

As of June 2013, about 50 hobbyists have reached that last stage  (dubbed  Star in a Jar  in some popular articles).  They almost always use a plasma of deuterium as nuclear fuel in a traditional Farnsworth-Hirsch Fusor, which can be built at low cost  (albeit beyond Hull's low estimate of $50-$400).

According to the aforementioned records,  Mark Suppes  (who has worked as a Web designer for Gucci)  became the 37-th  hobbyist  to achieve nuclear fusion, in 2010  (in a Brooklyn warehouse, at a cost of about  $39000).  Reportedly, Suppes was investigating Bussard's Polywell design, but he apparently settled for a standard Farnsworth-Hirsch fusor instead.

The amateurs are not even trying to produce the net output of energy that current research is aiming for.  Their fusors serve exclusively as  artificial sources of neutrons  based on deuterium-deuterium  (D-D)  fusion:

2H  +  2H   ®   4He  +  23.84648 MeV   ®   3He  +  n  +  3.26886 MeV

In 1966, a fusor built by Bob Hirsh himself put out  2 1010 neutrons/s  using DT fusion.  This is more than 1000 times the figure of merit achieved by the best amateur devices with DD fusion.

Tom Ligon :   The World's Simplest Fusion Reactor (1998)  |  The WSFR Revisited (2007)
Richard Hull :   video  |  The Farnsworth-Hirsch Fusor  (The Bell Jar, v.6, #3/4, Summer/Autumn 1997)
Carl A. Willis :   BS Thesis (2003)  |  Carl's Jr.
Thiago Olson :   video  |  Teenager achieves nuclear fusion  by Stephen Ornes  (Discover Mag., 2007-03-06)
Doug Coulter :   Coulter's Smithing   |   2010-06-26
Mark Suppes :   Homemade nuclear reactor in NYC  by Matthew Danzico  (BBC News, 2010-06-23)
Raymond Jimenez :   pdf  |  Amateur Nuclear Fusion    (a 40-page chronicle of the construction of a fusor)
Chad Ramey (b. 1993) :   Fusion for the Future (smallest fusor)   |   Fusioneer Subculture  by  Dan Solomon
Conrad Farnsworth :   disqualified from Science Fair (2013-06-01)
Helium-3 Fusion Apparatus  by ScienceGuy  (untested naive concept with numerical errors)
Diane Neisius :   Laser Diane builds a fusor
Plasma videos :   Five-Minute Fusor   |  
Mike Feldman:  Geek Group Farnsworth-Hirsch-Meeks Fusor by Paul Kidwell & Chris Boden (25 min video).

(2011-08-08)   The  Radioactive Boyscout  &  misguided endeavors:
Poor experiments attract more media attention than great investigations.

The best known case of radioactivity experimentations gone astray is surely that of David Charles Hahn (born Oct. 30, 1976)  who conducted misguided experiments on radioactivity in a potting shed at his mother's house, until 1994  (he was then a 17-year old boyscout who had earned a merit badge for atomic energy in 1991 and had already attained the rank of Eagle Scout).

David Hahn had gotten his start in chemistry from reading his grandfather's copy of  "The Golden Book of Chemistry Experiments".

David C. Hahn became the subject of a 1998 article in Harper's Magazine  by  Ken Silverstein and a subsequent best-selling book by the same author, entitled  The Radioactive Boy Scout (2004).

   David Hahn in 2007 
The Radioactive Boyscout at 31
David Hahn, in 2007

After being discharged from the U.S. Navy, David Hahn returned to his home state of Michigan, still obsessed with radioactivity.  On August 1st 2007, at age 31, Hahn was arrested in Detroit for stealing 16 smoke detectors  (containing Americium-241).  His face was covered with open sores, hastily attributed to radiation exposure.  No hazardous materials were found in Hahn's appartment.

Subsequently, Hahn was sentenced to a treatment facility where he had Internet access and would make weird posts on articles about his story,  using the handle  Thumper235  or  Thumper23598  and signing:  David Charles Hahn / Eagle Scout / Former U.S. Navy / Former U.S. Marine Corps (Retired) / Time Travel Institute Member / American Legion Member / Associates Of Applied Science / "The Radioactive Boyscout".

 Richard Handl
Richard Handl

A Swedish rad-freak who made the news :

In May 2011, Richard Handl  (a 31 year old unemployed man from Ängelholm, southern Sweden)  chronicled in his blog his own attempts at reproducing the misguided efforts of David Hahn.  On 2011-05-20, he quoted some hilarious tongue-in-cheek recipe  for building a "nuclear reactor" as if it had been some kind of inspirational  documentary...

The very next day, Handl reported a "meltdown" [sic!] after trying to cook  (on his stovetop)  americium, radium and beryllium in  96%  sulfuric acid, seemingly unaware of the dangerous propensity of concentrated sulfuric acid to  burp  when improperly heated.  He had been fooling around with his samples of radioactive elements "to easier get them blended" [sic!] in the naive way mocked by the aforementioned spoof video...

Richard Handl alerted the Swedish Radiation Safety Authority himself to make sure he wasn't doing anything illegal...  He was questioned by police, who confiscated his radioactive samples and his computer.  He readily admitted that his experiments were  crazy  but  (rightly)  argued that they were "not so dangerous"  (well, boiling concentrated sulfuric acid is just about as dangerous with or without radioactive samples in it). Following his arrest, Handl announced on his blog the "cancelation" of his project  (2011-07-22).  He clearly enjoyed the worldwide media attention that he attracted, starting with a  2011-08-02  Fox News preliminary report (from a NewsCore story) and culminating with a BBC news interview on 2011-08-04.

Richard's Reactor:  Blog of Richard Handl   |   The Raw Story by David Edwards (2011-08-03)   |   AFP
Splitting atoms in the kitchen?  Interview of Stephen Liddle by Brady Haran
The Noble Art of the Obsessive Hobby  by  Tim Dowling  (The Guardian, 2011-08-10)

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