U.S. Patent 6,377,436

Microwave Transmission Using a Laser-Generated Plasma Beam Waveguide

Issued April 23, 2002 to Jed Margolin


      A directed energy beam system uses an ultra-fast laser system, such as one using a titanium-sapphire infrared laser, to produce a thin ionizing beam through the atmosphere. The beam is moved in either a circular or rectangular fashion to produce a conductive shell to act as a waveguide for microwave energy. Because the waveguide is produced by a plasma it is called a plasma beam waveguide. The directed energy beam system can be used as a weapon, to provide power to an unmanned aerial vehicle (UAV) such as for providing communications in a cellular telephone system, or as an ultra-precise radar system.

Full Patent     1,403 KB (PDF)
 Specification Only      44 KB (HTML)
 Drawings Only       613 KB (PDF)
Reference: U.S. Patent  5,726,855  (Mourou)  763 KB (PDF)
Other References  746 KB (PDF)

By an interesting coincidence there is an article in the May 2002 issue of Scientific American (page 81) about ultrafast lasers. The article is coauthored by Dr. Gerard Mourou, one of the inventors of the chirped-pulse ultrafast laser.

In the event you are planning on building the device, I strongly urge you to contact me and secure my services in order to bring the device up in a controlled and orderly fashion. Otherwise, unless you build the device exactly as outlined in the Patent Specification, there is a possibility, however small, that it will produce a bang that is much larger than the one you may be expecting.

I believe there is a possibility that, with a few modifications, my invention can be used to produce a fusion reaction. Think linear tokamak.

You didn't think I stopped working on it after I filed the Patent Application, did you?  :-)

Jed Margolin
San Jose, CA
June 7, 2002

Microwave Transmission Using a Laser-Generated Plasma Beam Waveguide

Possibilities to Investigate

Jed Margolin

These possibilities are highly speculative, but because of their potential benefits (or consequences) they must be considered.

Possibility #1

Part 1:

If the frequency of the microwave energy is the same frequency as that used by microwave ovens (2.45GHz.), the water molecules in the waveguide will heat up, turning first into steam, and then into a plasma. We can inject water if the humidity is not high enough.

I believe there is a good chance this plasma will be contained by the waveguide due to the intense magnetic field produced by the ultrafast laser.

From the article in Scientific American (May 2002, page 82) written by Gérard Mourou and Donald Umstadter:

"  These compact lasers can fire a hundred million shots per day and can concentrate their power onto a spot the size of a micron, producing the highest light intensities on earth. Associated with these gargantuan power densities are the largest electric fields ever produced, in the range of a trillion volts per centimeter. Such intense laser light interacting with matter re-creates the extreme physical conditions that can be found only in the cores of stars or in the vicinity of a black hole: the highest temperatures, 1010 kelvins; the largest magnetic fields, 109 gauss; and the largest acceleration of particles, 1025 times the earth's gravity."
Part 2:

If this plasma is contained by the waveguide, we would like the plasma to come shooting out the end of the waveguide. This may occur naturally, especially if the beam is tilted above the horizontal. If not, by modulating the microwave energy (amplitude and/or frequency) we may be able to produce systolic action. Think of a standing wave pattern traveling along the length of the waveguide.

Part 3:

Being able to produce a blast of plasma through a cross-section of a few inches at long distances (10 KM. or so) would produce a weapon more destructive than I had planned, but would probably be acceptable. (Dead is Dead.)

However, there is a much better use for what I will call the plasma projector.

Since the plasma has mass, it has momentum.

We can use it to power the first stage of a launch vehicle. Since all the fuel for the first stage would come from the ground (and would be water) the launch vehicle would have an extremely high mass ratio. (A high percentage of the mass of the launch vehicle would make it into orbit. Most of the mass of current launch vehicles is in the first stage.)  The launch vehicle would only have to carry its own fuel to continue past the atmosphere (and for maneuvering and de-orbiting).

We can do this with a number of plasma projectors arranged in a circle aimed at the bottom of the launch vehicle which would be in the shape of a large disc.

When it is time to fire the second stage, the disc can be dropped. Alternatively, the disc can be comprised of vanes which can be opened. This has the advantage of giving the launch vehicle some amount of control of the launch, especially for dynamic stability.

The use of water as the primary fuel makes it much more environmentally friendly than the toxic rocket fuels currently used.

If NASA is too embarrassed to develop a launch vehicle that looks something like a flying saucer we will just have to find someone else to do it.

Possibility #2

If the laser-generated plasma beam waveguide, instead of being cylindrical, is conical and comes to a point (gradually, over a long distance, lets say 10KM.) the plasma will also be focused to a point. If the magnetic containment is sufficient, it may produce a fusion reaction at the point of the waveguide. It would be like a linear Tokamak.

There is a potential problem, since the critical dimension of a waveguide must be more than one-half the lowest frequency to be transmitted. As the waveguide narrows it will become less than this, so this is something to look into further.

The reason for using the 10KM. figure is that the ideal shape of this waveguide is an exponential horn, such as used in horn loudspeakers. A cross sectional area that changes exponentially is the optimum shape for matching the impedances of two different pressure areas, but having the cross sectional area change linearly over a long enough distance might be good enough.

If this works, it is possible that such a fusion reaction would propagate back through the waveguide to its source, so I suggest short bursts.

Since a conical waveguide may be produced accidentally simply by making a non-ideal mirror ring, any system must be very carefully designed and tested under controlled conditions.

In any event, this is much more of a weapon than I would like. It would instantly and completely destroy anything it hits, and then some.

One saving grace would be to use it to generate electricity, presumably at a distance considerably shorter than 10 KM., preferably like 2M. I would like that. Perhaps an external magnetic field can be used to shape the waveguide into an approximation of an exponential horn.

Another saving grace would be to use it in a rocket engine. In this case a pressurized cylinder (presumably metal) would be used to contain the atmosphere for ionization by the ultrafast laser and to provide water vapor for the fusion reaction. The idea is to have the energy released by the fusion reaction propel the plasma out the tail end at a very high velocity, thus producing thrust. Since the engine is obviously a mission-critical component, there should be at least two or three of them on the spacecraft.

While we're on the subject of atmospheres, both the Mourou patent and the Scientific American article seem to assume the use of a standard atmosphere for the ultrafast laser. I wonder what the ultrafast laser would do in a pure atmosphere of nitrogen, or hydrogen, or maybe just water vapor, since water vapor is a necessary component anyway. I also wonder what kind of trail the beam of an ultrafast laser would leave if it were aimed into a tank of salt water.

Possibility #3

Lately, I've been wondering about the effects of standing waves in the plasma projector discussed in Possibility #1.  Standing waves are produced in a transmission line when the line is terminated in other than its characteristic impedance. The energy is reflected at the impedance discontinuity; the percentage of energy reflected is a function of the impedance mismatch.

The highest impedance discontinuity occurs when the end of the transmission line is either open or shorted. A conducting plate would qualify as a short and would also provide a handy place for injecting water into the waveguide.

The microwave transmitter can be modulated (frequency and/or amplitude) to control the standing wave pattern.

The question is whether the standing waves would produce alternating areas of plasma compression and rarefaction and whether the compression in the areas of high compression would be high enough to be interesting.

Possibility #4

If you build a device using my patent (after obtaining a license, of course), I would like you to do the following:

1. Measure the frequency of the microwave energy at the end of the waveguide and compare it to the frequency of the microwave transmitter. While there is no reason to believe that the frequency will be different, we are venturing into unknown territory and should be alert for any anomalies.

2. For the same reason you should measure gravity both inside and immediately outside the waveguide. If anything can affect gravity anomalistically at less than galactic distances it would be the intense magnetic field and relativistic electrons produced by an ultrafast laser.

3. Just for grins, measure time inside the waveguide.

Jed Margolin
San Jose, CA
July 4, 2002 

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Copyright 2002 Jed Margolin