Technical Notes

   1.   D + T -> He-4 + n + 17.588 MeV
   2.   D + D -> He-3 + n + 3.268 MeV
   3.   D + D -> T + p + 4.03 MeV
   4.   He-3 + D -> He-4 + p + 18.34 MeV
   5.   Li-6 + n -> T + He-4 + 4.78 MeV
   6.   Li-7 + n -> T + He-4 + n - 2.47 MeV
D and T stand for deuteron or deuterium (H-2),
and triton or tritium (H-3) respectively.

The neutron produced in reaction 1 is extremely energetic, it carries away 14.06 MeV of the reaction energy, the alpha particle (He-4 nucleus) only 3.52 MeV.

The neutron produced in reaction 2 has an energy of only 2.45 MeV (similar to the faster fission neutrons), with the He-3 carrying 0.82 MeV. The division of energy in reaction 3 is 1.01 MeV for the triton, and 3.03 MeV for the proton. The two D+D reactions are equally likely and each will occur half the time. In reaction 4 the alpha particle carries off 3.67 MeV, the proton 14.67 MeV.

Reactions 5 and 6 are not thermonuclear reactions, strictly speaking. They are neutronic reactions, like fission, and do not require heat or pressure, just neutrons in the correct energy range. This distinction is usually ignored in the literature . The Li-6 + n reaction requires neutrons with energies is the low MeV range or below. The Li-7 + n reaction is only significant when the energies are above 4 MeV.

For fusion to occur, one must simultaneously maintain the pressure, temperature and particle density at a sufficient level.  Some remarks on this are:

1) For the ignition and sustained burn of a plasma the fusion product n*tau*T of the ion density, the energy confinement time and the ion temperature has to exceed a value of 50*1020 keV/m3. This has to be realized by ion densities of the order of 2-3*1019 m-3, energy confinement times of the order of 1-2 seconds and ion temperatures of the order of 20 keV (about 200 Million degrees).  While all these three individual values have been exceeded in present experiments the combined product has not been reached, yet. Since the last 30 years the world wide effort to reach this value has resulted in improvements of the order of 10000, but there is still a factor of about 10 missing.

2) The first type of generator to be invented relies on the fact that one of the neutrons in beryllium-9 is easily knocked loose. Occasionally if it is struck by an alpha particle, like those produced by some produced by some radioactive isotopes, a neutron will be released as a result of the collision:

     Be-9 + He-4 -> Be-8 + n + He-4

This happens in only 0.008% of collisions, so a strong alpha emitter (like polonium-210) is required to achieve the neutron flux needed.  Ref.

It is desirable to use fuels that are cheaper, and more stable than tritium. Deuterium, the sole fuel in reactions 2 and 3, is relatively cheap (especially considering its enormous energy content) and is completely stable. Pure deuterium has been used in at least one fusion weapon test - Ivy Mike, arguably the first true fusion explosion in history (1 November 1952). Unfortunately deuterium, like all elemental hydrogen, is difficult to store. It must either be highly compressed, or liquefied at extremely low temperatures. This problem can be overcome by combining the deuterium chemically with lithium to form lithium deuteride, a stable solid. An additional benefit is that through reactions 5 and 6, the lithium can itself participate in the fusion reaction.

To make use of these fuels, the slower reaction rates must be offset by compressing them to densities hundreds or thousands of times greater than those of normal conditions. At any given temperature the reaction rate goes up with the square of the density, a thousand-fold compression gives a million-fold reaction rate increase.

The work required to compress a gas is proportional to its temperature (at these pressures the physical strength of materials is negligible, and everything can be considered a gas). To minimize the work required for compression, or alternatively to achieve maximum compression for a given amount of work, it is important to keep the fusion fuel from getting hot until after the desired density is reached.

The fuel in the fission capsule consists of lithium deuteride that may be enriched in the Li-6 isotope (which makes up 7.5% of natural lithium). Natural lithium has been used but modern light weight designs seem to use lithium enriched in Li-6. There is some tritium generated by the fission neutrons, but as noted above the contribution to yield is insignificant. Far more tritium is produced by the D+D reactions, either directly by reaction 3, or by reaction 5 via the neutrons produced in reaction 2.

Since the D+T reaction rate is so high, and there is large excess of deuterium, the tritium is consumed almost as fast it is produced. The 14.1 MeV neutrons can also produce large amounts of tritium from Li-7 through reaction 6.

A large part of the fusion fuel can be burned before expansion quenches the reaction by reducing the density, which takes some 20-40 nanoseconds. The power output of a fusion capsule is noteworthy. The largest yield ever recorded had a yield of 50 megatons almost all produced by its final fusion stage. Since 50 megatons is 2.1x10^17 joules, the power produced during the burn was around 5.3x10^24 watts. This is more than one percent of the entire power output of the Sun (4.3x10^26 watts)!! The peak output was possibly even greater.  Definitely the hot set up for solar system exploration.

Perfect monatomic gases are of special interest to us here, not only because they are particularly simple to analyze, but because under many extreme physical regimes all matter tends to behave like a perfect monatomic gas (kinetic energy dominates other forms of energy present).

From: http://www.phys.uni.torun.pl/~jkob/physnews/node127.html
Superfluidity in the two helium isotopes is very different, a fact that stems from the fact that He-4, which consists of two electrons and a nucleus containing two protons and two neutrons, is a boson while He-3, which consists of two electrons and a nucleus containing two protons and only one neutron, is a fermion (Scientific American, December 1976). In He-4, the superfluid state is essentially a Bose-Einstein condensation of He atoms into a single quantum state. In contrast, the He-3 superfluid state consists of a condensation of pairs of atoms, somewhat analogous to the pairing of electrons in low-temperature superconductivity. (The discovery of superfluidity in He-4, at the much warmer of temperature of 2 K, occurred in 1938.) Furthermore, because its constituents (pairs of atoms) are magnetic and possess an internal structure, the He-3 superfluid is more complex than its He-4 counterpart. Indeed, superfluid He-3 exists in three different forms (or phases) related to different magnetic or temperature conditions. In one of these phases, the A phase, the superfluid is highly anisotropic; that is, it is directional, somewhat like a liquid crystal. To put it another way, this phase of He-3 (unlike He-4) has texture. This property was exploited in a recent experiment (Nature, 25 July 1996) in which vortices set in motion within a He-3 sample simulated the formation of topological defects ("cosmic strings") in the early universe. Another notable experiment in recent years was the verification (by Douglas Osheroff) of the "baked Alaska" model. This theory, formulated by Anthony Leggett of the University of Illinois, explains the somewhat piecemeal transition from the A phase of superfluid He-3 into the lower-temperature B phase by supposing that B-phase droplets can be nucleated within the supercooled A-phase by the ionizing energy of passing cosmic rays (Physics Today, June 1992).

 -- excerpted from http://www.onestep.com/milnet and other links where noted

Session I

8:40 - 9:20 S. Putterman "Defining the Unknowns of SL"
9:20 - 9:40 B. Gompf  "Resolving SL Pulse Width with
                                        Time-Correlated Single Photon  Counting"
9:40-10:00 M. Moran "Temporal Characteristics of SL"

Session II

10:20 - 11:00 H. Kuttruff "Bubble Dynamics and SL in Multi-Bubble Cavitation Fields"
11:00 - 11:20 F. Gaitan "Anomalous Mass Flux & Threshold for Light Emission in SBSL"
11:20 - 11:33 J. Holzfuss "Shock Wave Emission of SL Bubble"
11:33 - 11:46 Y. Lee "Shock Pulse from SL Gas Bubble"
11:46 - 11:59 J. Young "Magnetic Field Study of SL"

Session III

1:30 - 2:10 D. Lohse "SL Air Bubbles Rectify Argon"
2:10 - 2:30 R. Lofstedt "Mechanisms of Luminescence"
2:30 - 2:43 R. Gunther "Analytical and Numerical Results for Pressure, Temperature and Light"
2:43 - 2:56 P. Mohanty "SL as a Cooperative Many Body Phenomenon"

Session IV

3:15 - 4:15 Open Forum on the Future of Sonoluminescence
4:15 - 4:55 A. Prosperetti "Old Fashioned Bubble Dynamics"
4:55 - 5:08 M. Longuet-Higgins  "Particle Drift Near an Oscillating Bubble"
5:08 - 5:21 L. Frommhold "SL and Collision Induced Emission"
5:21 - 5:34 L. Bernstein "A Fully Coupled Radiation Hydrodynamic Model for SBSL"
5:34 - 5:47 W. McNamara "Metal Atom Emission from Multi-Bubble SL"

Saturday, September 13, 1997

Session V

8:30 - 9:10 K. Suslick "Multi-Bubble Sonoluminescence"
9:10 - 9:23 G. Williams "Bubble Dynamics and SL at Cryogenic Temperatures"
9:23 - 9:36 K. Yasui "A New Model of Single Bubble Sonoluminescence"
9:36 - 9:56 G. Holt "On the Relationship between Nonlinear Bubble Dynamics and Light Emission"

Session VI

10:15 - 10:55 R. Laughlin "Theory of Ultrafast Temperature Measurement of SL"
10:55 - 11:15 R. Apfel "Recent Work in SL at Yale"
11:15 - 11:28 L. Kondic "Why is ambient pressure important?"
11:28 - 11:41 S. Hilgenfeldt "Analysis of Rayleigh-Plesset Dynamics for SL Bubbles"
11:41 - 11:54 K. Weninger "SL from an Isolated Hemispherical Bubble on a Solid Surface"

Session VII

1:30 - 2:10 T. Matula "Sonoluminescence Experiments"
2:10 - 2:30 A. Szeri "Shock formation within sonoluminescence bubbles"
2:30 - 2:43 M. Chu "Comparative Study of Hydrodynamic models for SBSL"
2:43 - 2:57 S. Hayashi "Creation of a Variety of SL Bubble in Low Q Cavities"

Session VIII

3:15 - 3:55 H. Maris "Nucleation of Bubbles in Superfluid helium: Quantum Tunneling and Exploding Electrons"
3:55 - 4:08 T. Prevenslik "SL: the Effect of Magnetic Field in the Planck Theory"
4:08 - 4:21 M. Longuet-Higgins "Viscous Streaming from an Oscillating Spherical Bubble"
4:21 - 4:34 B. Gompf "Single Bubble SL: Acoustic Emission Measurements with a Fiber
     Optic Probe Hydrophone"
4:34 - 4:47 Stephane Zaleski "Simulation of Axisymmetric Free Surface Viscous Flow around a Non-Spherical
     Bubble in the SL Regime"
4:47 - 5:47 Critical Evaluation of the Symposium