Fusion Physics - Energy Boon or Nuclear Gloom?

David Schilter and Shivani Sharma

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?

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

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

Electrode Geometry

Outer mesh (anode)

Inner rings

(cathode, -ve bias)B

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)

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

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

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”

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%

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...