Posts by California Hal

There is a viable solution for this problem as outlined ...

There is a solution for this problem as outlined ...

We all agree that fusion of some sort is necessary for neither fossil fuels, nor renewables, nor fission can sustain the energy needs of the planet which require an increase of 14 TW of new energy sources plus replacement for our aging systems. Our current primary energy sources, fossil fuels and fission, are either polluting the air we all breath or they have unacceptable consequences when something goes wrong. Increasing the number of fission reactors by a factor of ten or more over the next few decades is simply untenable.

Fortunately, there is another means of achieving the energy needs of the world that is clean, green and very safe, - the fusion goal that we all desire. That is the ICF process know as RF Accelerator Driven Heavy Ion Fusion (HIF) that was studied extensively in the 1970s. The boundary conditions for successful ignition are set by the Lawson Criteria which simply states that the number of nuclei in a given volume must be large and the temperature very high for long enough for the fusion reaction to take place. The goal of the NIF was to demonstrate this was possible; a goal that was not achieved. The same goal is sought in Tokomak like devices: also never achieved in a fully sustainable way for times long enough to suggest viability as a power production facility. The comment attributed to Teller that says “if it involves plasma, it vont verk” seems very appropriate after the spending of 10's of Billions of dollars on the experiments at NIF and ITER and there predecessors.

But, the studies made at Argonne National Laboratory in the 1970s and incorporated into the HIDIF report in 1998 suggest that there is another way to meet the Lawson criteria. NIF has shown that frozen hydrogen can be compressed to densities of several hundred gm/cc. Unfortunately the NIF experiment needed a uniform compression of near 3000 and that goal has remained illusive, But compression using ion beams for both the compression and for a separate heating pulse, known as fast ignition, relies on the need for uniform extreme compression to a much more modest 100 fold compression terminated by a separate heating pulse that raises the fuel to temperatures approaching 100 million degrees.

The HIDIF design provided the compression and heating by a complex design utilizing a source of four heavy isotopes to accelerated to about half the speed of light in a linear accelerator. The resulting pulses of ions were stored in a storage ring until sufficient beam current was accumulated to provide the pulse current needed. On paper this seems appropriate, but in reality, this cloud of pulses was not a single beam but a shot-gun like blast of beams each with a different focus. This is the Achilles heel of the HIDIF design.

Re-examination of this design by Dr. Robert J. Burke and Dr. Charles E. Helsley, of Fusion Power Corp in California, has led to an elegant solution. If one dispenses with the storage ring and replaces it with a large collection of ion sources all aligned prior to acceleration one could compensate for the loss of the multi-pulse storage ring. Moreover, the use of more isotopes can be shown to be advantageous in energy deposition at the fuel pellet and the progressive conversion of a long sequence of pulses into a single multi-isotope beam, each isotope moving at a separate velocity and timed to arrive at the target simultaneously. Calculations show that such an accelerator does not violate any of the parameters that are in the accelerator designer's handbook until after the final focus. At that point the beam must be neutralized but this is only meters from the target. Calculated energy on the target can be as high as 1015 watts deposited in 10s of nanoseconds. Basko has calculated that this amount of energy deposition assures ignition with a burn efficiency of nearly 40 percent. Thus a modern version of the HIDIF fusion driver appears both feasible and economically viable.

The availability of a process that could achieve fusion by use of heavy ions provides an alternative path that will lead to success.

Ion sources can achieve currents of approximately 100 milliamps. To get enough energy on the target one needs a beam current of about 1000 amps at 140 GeV. - this is no small feat. But it can be done if one merges the ion current from say 500+ sources and accelerates them via a linear accelerator. But one also needs pulse compression. and this is achieved by using multiple isotopes and accelerating each to a common magnetic rigidity so that subsequent beam manipulations involving bending of the beam do not produce dispersion of the various isotopes. Each isotope has a different velocity in such a device and this proves advantageous for it allows the higher velocity isotopes to 'catch up' with the slower ones just as the target is encountered. This telescoping of the beams and the careful maintenance of the micro-bunches in each of the beams is what makes the high current required achievable in the FPC design.

Since the beams are essentially unidirectional, the ideal geometry of the target is cylindrical. Cylindrical targets have been examined by Basko (ref) and the target dynamics indicate that the conditions necessary for fusion can be achieved. (ref G Logan) But the use of multiple isotopes of varying mass, suggests an even better mechanism. The focusing of the slower isotopes on the axis of the target just after the compression pulse allows the creation of a fast ignition pulse that heats the pre-compressed fuel to fusion ignition temperatures. Moreover, This two stage ignition mechanism allows fusion to take place at considerably lower total applied energy, perhaps lower by a factor of 7. This in turn reduces the length of the accelerator thus reducing the cost of the driver.

The chambers operates at a modest vacuum being set by the temperature of the rain of lithium sheets and droplets sprayed into the chamber between pulses – a vacuum of about 10-5 Torr. These droplets also provide for pressure wave damping and their vaporization provides a working fluid for the transport of heat to the heat exchangers to extract the energy to be used in the electrical generators, etc.

The use of lithium or lithium-lead or FLIBE is essential for each moderates the neutrons to a degree necessary to remove most of the devastating effects of the unchecked neutron radiation. Again, not a new idea, but one investigated extensively in the 1970 to 1990 period.

What is needed at this point in time is a willingness to change course away from ITER and NIF and toward a technology that was endorsed for demonstration almost three and a half decades ago by the scientific community. If anything, our ability to do that demonstration has greatly improved through the advent of superior computers, higher frequency drivers, and new means of construction. Our need to resolve the CO2 problem (GHGs) is urgent.

I believe that the use of heavy ion driven fusion is the only way it can be achieved in the next decade – not the next century. This is the ‘Apollo” project for this era. HIF needs the funding and the political will to move down a known path to successful fusion.

RFADHIFusion has the ability to provide the world the energy it needs without additional GHGs, radio-active waste problems and the danger of a meltdown.