Tomoyuki Johzaki

Accuracy validation of flux limited diffusion models for calculating alpha particle transport in ICF plasmas

Within the framework of a one dimensional study, the accuracy is examined of two kinds of flux limited diffusion model: one is the artificially flux limited model developed by Corman and the other is based on the Levermore-Pomraning theory, for evaluating the alpha particle heating rate in laser imploded DT targets. It is found that the former model cannot correctly evaluate the ignition condition and the gain since it significantly underestimates the heating rate in the region where alpha particles are born. Contrary to this, in the latter model, which can estimate well the profile of the alpha particle heating rate, not only the time integrated burn properties but also the fuel evolution in space and time are in good agreement with results obtained on the basis of accurate transport calculations.

Effects of neutron heating on ignition and energy gain of laser-imploded D-T pellets

On the basis of coupled neutronic/hydrodynamic calculations, we examine the neutron heating effects on the ignition and burn propagation in laser-imploded D-T pellets. The fusion-produced neutrons deposit their energy all over the pellet region since the mean-free-path of the neutron is long. The fraction of neutron energies deposited to the central spark region during the ignition phase is too small to reduce the threshold energy of the laser for ignition. In the burn phase, the neutron heating decreases the maximum compression ratio and accelerates the plasma expansion. The inclusion of neutron heating hence decreases the pellet gain from the value in the case without neutron heating. Calculations neglecting the transport of neutron recoils overestimate the neutron heating rate in the reactor-grade pellets.

Fusion product momentum deposition in laser imploded targets

A calculation method for fusion product momentum deposition in dense plasma spheres has been developed and applied to laser imploded DT targets. The net radial momentum deposition from αparticles accelerates the expansion of the plasma sphere and thus reduces the rate of thermonuclear reactions. However, this effect is not so significant as previously expected because the rate of momentum deposition by the α particles is much less than the local pressure gradient around the burn front. The momentum deposition from neutrons is negligibly small because of its long mean free path.

Neutron heating in ignition and burn phases of laser‐imploded DT pellets

On the basis of coupled neutronic/hydrodynamic calculations, we examine the neutron heating effects in the ignition and burn phases of the laser imploded D‐T pellets. The neutrons deposit their energy all around the pellet, since the mean free path of neutron is long. The fraction of neutron energies deposited to the central spark region in the ignition phase is too small to reduce the threshold energy of laser for ignition. In the burn phase, the neutron heating decreases the maximum compression ratio and accelerates the plasma expansion. The inclusion of neutron heating then decreases the pellet gain from the value in the case of neglecting the neutron heating.

Simulation study on ablation and evacuation of liquid metal in laser fusion reaction chamber

Using the theories of photon count statistic and test data of the ultraweak photon emission from biological system, the biophoton fields spectra distribution properties were studied in this paper. An experimental setup for testing UPE in different spectral region were designed. The test data proved UPE of living biological system exists in wide spectra region from UV-visible to IR. Using the test data, we can obtain important conclusions that is UPE almost has nothing to do with wavelength. The conclusion has important significance for proving the bio-photon coherence. In the end of this paper, the medical applications of UPE in 21st century were discussed simply.

Neutronic effects in reactor-size ICF targets

On the basis of coupled transport-hydrodynamic calculations, the neutronic effects in reactor-size volume ignition targets are investigated. It is shown that contrary to the case of central spark ignition, neutrons effectively heat the plasma in the ignition phase and reduce the threshold temperature for ignition. In practically-interesting regions where the areal density of compressed targets < 15 g/cm 2 , this positive effect exceeds the negative one, i.e. a shortening of the confinement time due to excessive heating in the burn phase. Moreover, the suprathermal fusion reactions induced by neutron recoils appreciably contribute to the energy production. Thus, in the volume ignition scheme, the inclusion of neutronic processes results in lowering the ignition temperature and increasing the maximum fuel gain.

Ignition and burn dynamics of low temperature ignition D-T targets

On the basis of 1-D coupled transport-hydrodynamic simulations from the stagnation phase, we investigate the ignition and burn dynamics of low temperature ignition D-T targets. It is shown that the ignition takes place in the central fuel region. The burn dynamics, however, differs from that of central spark ignition scheme because of the difference in density profile in the ignition phase. It is also shown by numerical simulations that the bremsstrahlung loss during the stagnation phase significantly affects the ignition condition and the energy gain.