Fusion Physics - Energy Boon or Nuclear Gloom?
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Transcript of Fusion Physics - Energy Boon or Nuclear Gloom?
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Fusion Physics - Energy Boon or Nuclear Gloom?
David Schilter and Shivani Sharma
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Problem Statements...
• Is it possible to construct a potential array (electrostatic potential well) which would allow for resulting energy close to or exceeding applied voltage?
• What electrode configuration in an IEC device can both avoid energy loss due to space charge as well as encouraging ion acceleration?
• Would the idea of circulating ions provide a solution to the problems of space charge while also inducing nuclear fusion?
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Plasmas
• AC grid causes radio frequency discharge which creates oscillating B and E ionizes the hydrogen gas used to create a plasma, a mixture of high energy ions and electrons
• Diffuses into a chamber that also contains a neutral hydrogen background gas, which is not affected by the electrodes
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Experimental Setup
• Inner spectacle (=22mm) cathode
• Outer mesh anode (earthed)
• Pressure maintained at 5mTorr (7x10-6 atm)
• Magnetic field was set at 70 gauss (7x10-3 T)
• Voltages of 1-10kV applied to cathode
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Electrode Geometry
Outer mesh (anode)
Inner rings
(cathode, -ve bias)B
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Some theory...
• The H line (656.3nm) represents the first atomic transition in the Balmer series (from n=3 to n=2)
• 1/ = RH[(1/2)2 - (1/n)2] where Rydberg’s constant = RH = 1.0968x107m-1
• The spectrometer measures intensity near this wavelength, providing a wavelength distribution.
• Fusion cross-section (probability) of 1H is many orders of magnitude less than deuterium (2H) or tritium (3H)
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Charge-exchange Reactions• Charge exchange
reactions occur as fast, ionized plasma collides with stationary background gas
• In all cases, the high energy plasma becomes unstable due to the exchange and fragments
• This results in the excited radical H* which is detected by the spectrometer
H+ + HH* + H+
H2+ + H H* + H+ H+
H3+ + H H* + H2+ H+
H+ + H2 H* + H2+
H2+ + H2 H* + H + H2
+
H3+ + H2 H* + H2+ H2
+
analysed
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Observations
• Very slight circulation of ions observed between two rings, which were red hot
• Majority of ions passed through, and continued in a roughly linear path, which created “beams”
• Purple colour characteristic of high energy hydrogen
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Energy Distributions
• Shifts involved are characteristic of the various charge-exchange reactions
• The “knee” relates to the most energetic ions
• Intense alpha line is due to background gas
• Note symmetryions moving toward and away from spectrometer
Intensity vs Doppler Shift
0
10000
20000
30000
40000
50000
60000
-3 -2 -1 0 1 2 3doppler shift (nm)
Inte
nsity
(arb
. uni
ts)
H-line
“knee”
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Results Continued...
• Energy plotted against voltage results in a linear relationship
• It was also found that that B had no effect on the maximum ion energies
• Efficiency=gradient, which in this case is approximately 7%
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Conclusions
• Excited and Doppler shifted atoms were observed at wavelength up to 0.89nm greater than that of the H line (o=656.3nm) corresponding to energies of 8.7x10-1keV
• Efficiency of 7% clearly too lownew grid design• B not strong enough to induce circulation in a large
proportion of the ions• Ions accelerated from each direction rather than in a
circular motion to avoid the “virtual anode”• The simulation of the exact same conditions were
undertaken and discrepancies accounted for...