SEM Fusor    

Confinement of deuterium ions and electrons with a static electromagnetic field

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In a "normal" fusor an electric field  heations to conditions suitable for nuclear fusion.  Because most of the ions fall into the wires of the inner grid (and electrons collide with the wall), these fusors suffer from high conduction losses and do unfortunately not produce net energy. Would it be possible to design a new kind of fusor without this inner grid but that still confines the ions (and electrons) more or less in the centre?

Let's consider the following:


Fig. 1. Design of SEM fusor. (Shem)


It consists of:

  • A vacuum chamber.

  • Two rings at a constant voltage of  about -100 kV and one ring  and two spheres at a constant voltage of about  +100 kV (these voltages can have other values, can  be reversed and one or more rings or spheres can also be deleted).

  • A constant magnetic field of about 1 or 1,5 tesla, produced by, for example, a superconducting magnet.

  • The vacuum chamber contains a low concentration of deuterium gas which should be ionized by the voltage differences between the rings and spheres. However, more efficient is perhaps to inject the deuterium ions and electrons, as shown in the image, although a bit more complicated to realize.


When do deuterium D+  ions  fuse?


If two  D+  ions with the same but opposite speed collide head on,  their speed must be at least 8,3E6 m/s in order to come at such a short distance from one each other that the strong nuclear force becomes larger than the repulse Coulomb force. (see temp.- speed calculations  and  droom11.16 )


But because of  i.a. tunneling this speed can be lower:  In, in hyperphysics and other sources a temperature of about 450E6  degrees C is mentioned for D-D fusion reaction to occur. This corresponds with a mean speed of  about 2E6 m/s .



Confining  D+  ions with speeds up to 3E6 m/s


In a field of 1,5 tesla deuterium ions with a speed of 1,4 E7 m/s move in circles with a radius of 0,2 m (see   radius D+ ions in a magn.  field ).  So with this magnetic field it seems to be possible to avoid that the particles escape sidewards.


A positive charged sphere at 151 V and with a radius of 8 cm will stop a D+ particle with a speed of 3E6 m/s and an initial distance of 30 cm from the centre of the sphere. See calculationSo it seems to be possible to confine the fast D+  ions in the vertical directions with a static electric field.


The electrons, by the way, are a lot easier to confine, because of their smaller mass.



Computer simulation


A simulation program is used to simulate the SEM fusor design.


The deuterium ions and the electrons are injected into the vacuum chamber with vertical speeds of about 3.105 and 3.104 m/s.. They interact with the static electromagnetic field and with each other according Coulomb's and Biot-Savart law (non relativistic).  Leapfrog integration is used



Fig. 2. Screenshot of a simulation experiment.

In this experiment the vertical magnetic field strenght is 1,5 T and the
 static voltages of the rings and spheres are +/- 200 kV.


Shown is a cross section in a vertical plane through the centre of the vacuum chamber; the three dimensional positions of the particles are projected in this plane. Old positions become black. The directions of the electric field is indicated with the arrows. The redder, the stronger is this field.


Result: both the deuterium ions and the electrons stay confined (the D+ ions reach speeds up to of 3,5.106 m/s).



Another configuration.


Fig. 3. Screenshot of another simulation experiment.


The blue and red rings are again charged with a constant voltage. A current I flows through the gray circles which produces a magnetic field somewhat in the form of a magnetic bottle. The deuterium ions and the electrons are injected into the vacuum chamber.


Result: both the deuterium ions and the electrons stay confined (the deuterium ions reach speeds up to 2.106 m/s).




  • If in the first experiment the rings and spheres of the SEM fusor are charged, will the low concentration of deuterium gas be ionized? Injecting the electrons and deuterium ions inside the vacuum chamber will be probably more efficient, but having an ion and electron gun inside could perhaps cause problems.

  • In the simulation non relativistic formulas are used. But the particles achieve quite high speeds. What will be the error because of this?

  • Deuterium ions with very high speeds ( > 3,5E6 m/s in the first experiment) will still escape, according the simulation. How many? Also the accelerating and decelerating of the charged particles causes losses.. See calculations .

  • In the simulation only a couple of hundreds of particles can be generated (because of lack of computer power). In reality there will be millions and millions more . Will their behaviour then be alike?

  • In the simulation a part of the electrons are concentrated in the centre. Will they form a kind of virtual electrode and attract the positive deuterium ions to the centre? (as in a polywell ) This would improve the SEM fusor!

  • Without the charged spheres our design is quite similar to a Penning Trap .  The SEM fusor could be considered as a modified Penning trap. But instead of confining only one type of ion, both positive and negative particles are confined. Is this really a new idea and, perhaps..,  the egg of Columbus?  I searched the internet, but could not find something similar.

  • Charging the rings and spheres with +/- 200 kV (or 100 kV), is it realizable? It seems to be possible to acquire dc power supplies up to 200 kV.

  • Will (easy) nuclear fusion take place, similar as in the "normal" fusor? How much fusion will take place?

  • Perhaps we could instead of deuterium inject boron and hydrogen ions and achieve aneutronic fusion, see Experiment_11.17.9  ( or another possibility: deuterium and tritium).

  • A simplified design is only with two rings. See: Video



Real experiments should be performed to clearify these doubts...


Remark: the advantage of confining both positive deuterium ions and negative electrons is that we will not accumulate a (huge) electrical charge inside the vacuum chamber that would limit the quantity of particles. The disadvantage is that the electrons will cause looses.


See also:

More  information, calculations and experiments
More calculations

Site map 


With about 2 millions (dollar or euro) I could buy a building for a lab, magnet, instruments... and do real experiments.

The fusion experiment ITER in the south of France costs about 20000 millions... so 2 millions isnīt so much J

I do not expect a lot of the next button, but who knows.. some miracle could happen, and the SEM fusor experiments could work...






20 February 2014 - 2019      by  Rinze Joustra