The Farnsworth Fusor

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The Farnsworth Fusor

• Nuclear fusion in the garage

Frank Sann fusion star
Henry Hallam, Fergus Noble - November 2004
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Inertial Electrostatic Confinement

• Electrostatic nuclei accelerated by electric
  field
• Inertial continue moving due to momentum
• Confinement collide in central region with
  sufficient energy for fusion

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Anatomy of a fusor
Deuterium gas at about 5 Pascals (5 x 10-5
atmospheres)
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Operation
D
D2
e-
He
n
D
D2
e-
Repeat
Next
n
He
Neutron
Helium-3
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Operation
D
D2
e-
T
H
D
D2
e-
Repeat
Next
H
T
Proton
Tritium
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Reactions

• 2H 2H -gt 3He (0.82 MeV) n (2.45 MeV)
• 2H 2H -gt 3H (1.01 MeV) 1H (3.02 MeV)
• Equal probabilityeach happens 50of the time
• 3He or 3H can also beused as fuel
  betterresults but veryrare expensive!

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History of the fusor

• Dr. Philo T. Farnsworthinventor of electronic
  television, built the first fusor in 1959 after
  noticing the focusing effect in vacuum tubes
• By 1966 he was producing 1012 neutrons/second
  with a complicated device involving filaments,
  ion guns etc.
• Dr. Robert Hirschmodified the fusor design to be
  the simple grid system. Reduced neutron counts
  but greater efficiency.
• Little research since Farnsworths death in 1971.
• First successful amateur fusor built by Richard
  Hull in mid 1990s

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Other peoples fusors
Farnsworths fusors in the 1960s
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Other peoples fusors
Richard Hulls first neutron-producing fusor
(left) and latest (right)
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Other peoples fusors
Joe Zambelli (current amateur record holder)
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Other peoples fusors
Brian McDermotts fusion star
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Our fusor construction photos

• 15 months and 3000

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Our fusor
Vacuum pumps
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Our results so far
Air plasma at about 1.5kV, 5mA, 4.5 x 10-2 torr
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Our results so far
High power photo 1kV, 60mA at about 3.5 x 10-2
torr Too bright for the camera!
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Our results so far
Video of an early run
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Our results so far
Blue colour caused by very thin layer of
deposited copper
Effect of a long run at high power on a copper
spiral grid Melty melty!
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The next step

• Reduce interference with electronics
• Run at lower pressure ? higher voltage
• New spherical grid
• Get deuterium gas ? fusion!
• Record full data sets at different pressures,
  voltages etc as a permanent reference point
• Ion guns, magnetic shielding

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Practicality uses of IEC fusion

• Avg. energy per fusion 3.6MeV
• Energy to accelerate deuterons 0.12MeV
• Net energy gain 3.5MeV per fusion
• Best rate Farnsworth with 1012 neutrons/sec
  2 x 1012 fusions/sec 7 x 1012
  MeV/sec 1.1 Watts
• Best amateur Zambelli with 107
  neutrons/sec 11 microWatts
• But actually requires several kW power in!

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Practicality uses of IEC fusion

• Increased power, larger scale etc? More fusions,
  greater power out
• But efficiency does not improve
• Losses
• Heating grid from ion bombardment
• Ionisation
• Xray production
• Wasted deuterons that do not fuse must be
  recirculated and accelerated again

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Practicality uses of IEC fusion

• Too inefficient to use as an electricity source
• But many other applications
• Compact neutron generator lunar probe
• Fission/fusion hybrid reactors
• Plasma physics experiments
• Neutron activation analysis
• Fusion concept demonstrator

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Whats in it for us?

• Needed to learn many skills
• Vacuum technique
• Metalwork
• High voltage engineering
• Electronics for computer control
• Physics and nuclear theory
• Error analysis and dealing with real problems
• Overall has been a great learning experience and
  is not over yet!
• 6th-form students can accomplish demanding
  projects try a Tesla coil or fusor yourself!

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Thank you!

• Interested in more details?http//henryhallam.cj
  b.net/fusor/
• Any questions?

Henry Hallam, Fergus Noble - November 2004