Tritium, beams

Wolfgang and his coworker (Menzinger and Wolfgang 1969) studied threshold energy of substitution products in T -i-C6Hi2 (solid cyclohexane) reaction using a tritium beam accelerator. For simple substitution, the threshold energy is about 0.5 eV. However, for the products (n-hexane-T and hexane-T) for which C-C bond rupture is required, it is about 4.5 eV. 

Laser-Assisted Thermonuclear Fusion. An application with great potential importance, but which will not reach complete fmition for many years, is laser-assisted thermonuclear fusion (117) (see Fusion energy). The concept iavolves focusiag a high power laser beam onto a mixture of deuterium [7782-39-0] and tritium [10028-17-8] gases. The mixture is heated to a temperature around 10 K (10 keV) (see Deuterium AMD tritium). At this temperature the thermonuclear fusion reaction... 

Another approach to nuclear fusion is shown in Figure 19.6. Tiny glass pellets (about 0.1 nun in diameter) filled with frozen deuterium and tritium serve as a target. The pellets are illuminated by a powerful laser beam, which delivers 1012 kilowatts of power in one nanosecond (10 9 s). The reaction is the same as with magnetic confinement unfortunately, at this point energy breakeven seems many years away. 

The cross section for the 3H(maximum value at only 107 KeV incident deuteron energy. When thick ( 1 mg cm-2 thick deposit of titanium) titanium-tritium targets are used, however, the neutron yield continues to increase even above 200 KV acceleration potential. This is due to increased penetration of the deuteron beam into the tritium enriched layer. Since the penetration of molecular deuterium ions is less than that for monatomic deuterium ions for the same acceleration potential, accelerators using Penning ion sources require extremely clean vacuum systems to minimize build-up of deuteron absorbing deposits on the surface of the target. 

The Tokamak Fusion Test Reactor was the first fusion facility with extensive experience with tritium fuelling and removal. During the 3.5 years of D-T operation, 3.1 g T was supplied to the plasma by neutral beam injection and... 

New fusion applications include the concept of production of intense negative ion beams ( ) (for neutral beam injection for heating and diagnostics in tokamaks or other magnetically confined plasmas (26, 28)) by using photodissociation to ion pairs (e.g. NaLi + hVyy Na + Li") in supersonic molecular beams. Another promising concept is the use of laser induced fluorescence to monitor very low tritium concentrations (as little as 10 Tj/cm ) under fusion reactor conditions (29). 

The use of lithium as a solid compound, a pure melt, or a molten alloy is required for tritium breeding in at least the first generation of fusion reactors. Three fusion reactor concepts are discussed with emphasis on material selection and material compatibility with lithium. Engineering details designed to safely handle molten lithium are described for one of the example concepts. Tritium recovery from the various breeding materials is reviewed. Finally, two aspects of the use of molten Li-Pb alloys are discussed the solubility of hydrogen isotopes, and the influence of the alloy vapor on heavy ion beam propagation. 

The Li nucleus can absorb a fast (above 3 MeV) neutron to produce a tritium nucleus, an alpha particle, and a slower neutron. A moderated neutron can be absorbed by a Li nucleus to produce a tritium and an alpha. Neutronic calculations indicate that a thick sphere of natural lithium could breed about 1.8 tritium atoms for each tritium atom burned in a fusion reaction (1 ). Structure and portions of the volume left open for fueling or driver beams reduce the 1.8 tritium breeding ratio. If the ratio falls below 1.0, it may be increased by addition of a neutron multiplier such as Be or Pb, and by isotopically enriching the Li in °Li. 

With a heavy-ion-beam driver (26), the vacuum system might operate around 0.13 Pa (10" Torr), with about 50% of the vapor being pumped per second. Then, about 0.7 mPa (5 x 10 Torr) of tritium, or twice the pressure associated with 0.2 mg tritium, is allowable if only the liquid is to be processed. 

The basic idea is to ignite and bum a few milligrams of deuterium-tritium fuel by means of high-power laser or ion beam pulses. Two large laser facilities are presently under construction which should demonstrate within the next 5-10 years the feasibility of single micro-explosions. These are the National Ignition Facility (NIF) in Livermore, US and the Laser MegaJoule (LMJ) in Bordeaux, France. 

In laser- and particle-beam-driven ICF, a millimetre-scale capsule of deuterium and tritium (D-T) would be imploded to create a sufficiently high density (-10 g cm ) and temperature (-10 keV) at the centre to ignite the thermonuclear reaction D-(-T He+n-i-17.6 MeV. The fusion burn would then propagate through the surrounding... 

Nuclear fusion provides the energy of our sun and other stars. Development of controlled fusion as a practical source of energy requires methods to initiate and contain the fusion process. Here a very powerful laser beam has initiated a fusion reaction in a 1-mm target capsule that contained deuterium and tritium. In a 0.5-picosecond burst, 10 neutrons were... 

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