Axil
Forum Replies Created
-
The Front Lens
The purpose of the front lens is to minimize the dispersion of the radiation beam and bring its focus to a sharp point. To accomplish this, a defection lens will be used.
Diffraction lenses use the interference between the periodic nature of EMF radiation and a periodic structure such as the matter in a crystal. An elementary derivation of the Bragg condition assumes that the incident waves are reflected by the parallel planes of the atoms in the crystal. There is constructive interference if the optical path difference between neighboring paths is a multiple of the wavelength.
Based on the energy wave length produced by the plasmoid, either Bragg- or Laue geometry will be used.
Bragg- vs. Laue geometry: The Bragg condition implies that higher incoming photon energies require smaller Bragg angles. At gamma-ray energies, Bragg angles are generally less than one degree. The reflection can be at the surface (so-called Bragg geometry) or the beam can pass through the crystal volume (so-called Laue geometry). The maximum efficiency for diffraction in the Bragg geometry is close to 100% (assuming no absorption).
A hard-X ray lenses operating in Bragg geometry using mosaic pyrolithic graphite crystals has been proposed by Frontera et al 1995.The concentrator consists of 28 confocal parabolic mirrors. Each mirror is made up of small pieces of mosaic crystal with the diffraction planes parallel to the parabolic surface, which results in a broadband energy response.
Laue geometry lenses : In a crystal diffraction lens, crystals are usually disposed on concentric rings such that they will diffract the incident radiation of the same energy onto a common focal spot. A crystal at a distance r1 from the optical axis is oriented so that the angle between the incident beam and the crystalline planes is the Bragg angle. Its rotation of around the optical axis results in concentric rings of crystals. With the same crystalline plane used over the entire ring, the diffracted narrow energy band is centered on E1.
Two subclasses of crystal diffraction lenses can now be identified – narrow bandpass Laue lenses and broad bandpass Laue lenses.
Narrow bandpass Laue lenses use a different crystalline plane for every ring in order to diffract photons in only one energy band centered on an energy E1=E2 (see figure).
Overall General Reactor Design.
All alpha ions and fast electrons from the polls of the plasmoid are converted to x-rays through tungsten target irradiation.
256 x-ray production modules are evenly space on the surface of a sphere of N meters in radius each centered on the common module focal point at the center of the sphere.
This large N meters in radius sphere holds a vacuum and but at its center, a boron/hydrogen gas is puff released.
In a fusion application, boron/hydrogen fusion at the center of the large sphere produces X-rays that are directly converted to electricity on the inner surface of the sphere by a foil based X-ray to electricity conversion layer.
All Xcon modules are fired simultaneously. Because fusion is used to produce x-rays in the module, a power gain based on its fusion energy gain factor “Q” of the module can be expected.
By comparison, a Q factor of only 1% will put Xcon and the LIFE laser based reactor on an even footing, since the efficiency of its lasers is only 1%.
The design risk to improve the performance characteristics of the Xcon over existing ICF concepts is small.
Pulsed Operation
Unlike the Z-machine, whose firing repitition rate is at best .1/sec and life at 10/sec, the Xcon is capable of a firing repetition rate of 1000/sec.
Applications
With some design reconfiguration the Xcon concept is capable of the following functions:
Design replacement for the Z machine
Design replacement for the LIFE reactor
A new ICF design concept
Fusion based nuclear rocket engine.
An Xcon based in Space star wars X-ray type anti-ballistic missile system
If miniaturized, a stage one trigger for a pure fusion nuclear weapon.Development Funding
This type “out-of-the-box” system is desirable for development by DARPA since it involves possible improvement to existing and future fusion concepts and weapons.
ohiovr wrote: Getting break even and beyond is of course the primary concern but is it possible to scale the power of these reactors? The polywell people think they can get a gigawatt out of a reactor 10 meters across. Lots of little reactors is fine of course but could something larger be made? I’m looking for electrical generators for space applications. Focus fusion is already a plus because it doesn’t use thermal effects for power generation and thermal management is not so great in space with no cold air or water to sync to. Any chance for gigawatt reactors?
Yes, I think so as follows:
Overview and Rationale
I propose a new type of inertial confinement fusion (ICF) based device to test materials in conditions of extreme temperature and pressure, to gather data to aid in computer modeling of nuclear weapons and to provide a backbone technology for a high efficiency, high gain, and high output fusion reactor.
Currently, the Z machine is the largest X-ray generator in the world and is designed to test materials in conditions of extreme temperature and pressure. Operated by Sandia National Laboratories, it gathers data to aid in computer modeling of nuclear weapons. The Z machine is located at Sandia’s main site in Albuquerque, New Mexico.
The primary weakness in the current Z machine approach is the inefficiency in the way it produces and applies x-rays to the target. Most of its energy is radiated way by various mechanisms including alpha particles, high energy electrons, light, heat, and x-ray dispersion. Only a modest faction of the input power reaches the target in the form of x-rays.
The LIFE laser fusion reactor is also inefficient in its delivery of power to its target. The efficiency of its lasers is less than one percent.
Xcon
One way to improve the design of these types of ICF device is to construct a high efficiency multi-stage fusion based focused X-ray source and concentrator (Xcon).
The principle behind Xcon is simple. Using a few hundred fusion based x-ray production modules, produce hard X-rays and gamma rays using aneutronic fusion and concentrate them into a small volume of space in the same way as the LIFE laser reactor concentrates laser light into a millimeter sized spherical volume.
General Design.
An x-ray production module is a small aneutronic fusion reactor shaped like the circular headlight of an automobile. It uses aneutronic boron based fusion to produce a point source of x-rays, fast electrons and alpha particles.
This reactor fires a very powerful electrical discharge into a hollow tube in tube cathode/anode pair where the anode is hollow. During the electrical discharge, this sparkplug like device forms a plasmoid near the anode tip at the focal point of a parabolic hard radiation lens system.
This parabolic lens can reflex x-rays and gamma rays form this plasmoid point source and focus them on a point in space about N meters away.
The cathode/anode pair is composed of boron doped diamond. This pair is highly conductive, transparent to x-rays and gamma rays, optimally resistive to erosive ware and can withstand an operating temperature up to 3000C.
The electrodes are enclosed and anchored in a paraboloid shaped polycrystalline diamond support structure formed with large 100 nanometer sized crystals. The diamond paraboloid is faced with a flat lens composed of graphite that provides an enclosed volume that can hold a vacuum. Puff injection of boron and hydrogen gas near the anode and is coordinated with the electrical discharge and provides the fusion fuel source.
The Lens System
In order to cover energies up to about100 KeV – and maybe beyond – High-Energy Photons lens geometries such as Kirkpatrick/Baez Optics, Bragg-Lenses, Laue-Lenses, and Fresnel lenses can be used together with multilayer coatings as a mirror surface.
These multilayer coatings consist of alternating layers of high and low index n of High-Energy Photons refraction materials: The reflection by a multilayer mirror is described by the constructive interference of the reflections at all low-high n interfaces This result in a sizable total reflectivity of the system. Similar to the Bragg-diffraction in crystals, the reflections have to be added with the correct phase relationship, leading to a boundary condition that relates incidence angle q, layer thickness d and wavelength l
2 d sin q = n l
Where n, the order of the reflection is an integer >= 1(multilayers are most commonly used in the first order, n = 1). Consequently, the response of so called Uniform Period Multilayers results in a narrow energy-bandpass. High reflectivity in a broad energy-bandpass can be achieved with graded multilayer coatings, here the film thickness d is varied over the stack. These Extremely Broad Band (EBB) Multilayers with reflectivities over bandpasses of > 20 keV are currently being intensely developed.
The materials for the reflector/spacer coatings are selected for their different indices of refraction of hard readiation and for minimum absorption – presently considered material combinations are W/Si, W/C, Ni/C, and Pt/C.
Recent development work for the hard X-ray telescopes has indicated potential up to around 200 keV for this technique.
See the following graphic representation of the parabolic shaped back reflector structure:
Rather than reflect the high energy photons along a parallel path as in the diagram, they will be bent to converge at a point N meters distant based on overall reactor design requirements. This provision is in place to optimize the performance of the front lens system.
Continued in next post.
