P. C. Souers

Anisotropic shock sensitivity and detonation temperature of pentaerythritol tetranitrate single crystal

Shock temperatures of pentaerythritol tetranitrate (PETN) single crystals have been measured by using a nanosecond time-resolved spectropyrometric system operated at six discrete wavelengths between 350 and 700 nm. The results show that the shock sensitivity of PETN is strongly dependent on the crystal orientation: Sensitive along the shock propagation normal to the (110) plane, but highly insensitive normal to the (100) plane. The detonation temperature of PETN is, however, independent from the crystal orientation and is determined to be 4140 (±70) K. The time-resolved data yielding the detonation velocity 8.28 (±0.10) mm/μs can be interpreted in the context of a modified thermal explosion model.

Permeation of helium and hydrogen from glass‐microsphere laser targets

Isothermal outgassing curves of hollow glass microspheres filled with helium, hydrogen, or deuterium gas have been determined. Four million 40–45‐μm soda‐lime glass microspheres, similar to laser‐fusion targets, were filled by gas permeation at 693–763 K and outgassed at 292–573 K. The permeabilities were calculated by an exponential theory, and they agree to an order of magnitude with the literature values. The outgassing curves are not pressure dependent. Two irregularities are apparent. First, the counting of target‐quality individual D‐T–filled microspheres shows a permeability spread of an order of magnitude from one microsphere to the next, which may be caused by variable chemical composition. Second, all the gases show deviations from exponential behavior in the form of tails at long times. Chemical reaction of the hydrogen with the glass, as well as incomplete filling and outgassing, may cause the hydrogen tails; the cause of the helium tails is not known.

Infrared spectra of liquid and solid HT and HD in mixtures with T2

The collision‐induced fundamental vibration–rotation spectra of liquid and solid HT and T2 in a mixture of 50% H and 50% T have been recorded. The spectra of liquid and solid HD in a 90% HD plus 10% T2 mixture have also been observed. The frequencies of the numerous single and double transitions have been compared with those calculated from the known molecular constants. Deep holes have been observed in the Q (O) phonon band of solid HD, HT, and DT. The position and extent of these holes have been related to a theoretical treatment which attributes the holes to a coupling of the rotational and translational motion of the molecules through the anisotropic part of the intermolecular interaction. The effect of J=1 impurity molecules on the intensity of the sharp Q1(O) line of liquid HD is discussed and the effect of the radioactive decay heat on the temperature of the liquid and solid samples is evaluated.The collision‐induced fundamental vibration–rotation spectra of liquid and solid HT and T2 in a mixture of 50% H and 50% T have been recorded. The spectra of liquid and solid HD in a 90% HD plus 10% T2 mixture have also been observed. The frequencies of the numerous single and double transitions have been compared with those calculated from the known molecular constants. Deep holes have been observed in the Q (O) phonon band of solid HD, HT, and DT. The position and extent of these holes have been related to a theoretical treatment which attributes the holes to a coupling of the rotational and translational motion of the molecules through the anisotropic part of the intermolecular interaction. The effect of J=1 impurity molecules on the intensity of the sharp Q1(O) line of liquid HD is discussed and the effect of the radioactive decay heat on the temperature of the liquid and solid samples is evaluated.

Nondestructive inspection of transparent microtargets for laser fusion

The method is described for the nondestructive inspection of small (<100‐μm outside diameter) hollow thin (<2‐μm wall thickness) transparent shells used as laser‐fusion targets. Utilizing the interference properties of light, this method enables measurements of sphericity and absolute wall thickness to accuracies better than ±10%. The equipment and calibration procedure are discussed.

Collision induced infrared lines in solid hydrogens caused by tritium radioactivity

Abstract We report the first observation of infrared absorption lines due to the presence of radioactive tritium in crystals of the solid hydrogens. Two prominent lines appear at the low-frequency side of the collision-induced spectrum, and are interpreted as due to the presence of positive and negative ions or electrons created during the radioactive process.

Time-resolved temperatures of shocked and detonating energetic materials

Chemical processes occurring in shock-compressed and detonating high explosives have been studied using fast time-resolved emission spectroscopy and a two-stage gas-gun. The spectral characteristics of emission from shock-compressed nitromethane, tetranitromethane and single crystals of pentaerythritol tetranitrate are typically very broad and structureless, likely representing thermal emission. Assuming the thermal emission from a gray-body, the emission intensity can be correlated to the temperature changes in shock-compressed and detonating high explosives. We report Chapman-Jouguet temperatures of 3800 K for nitromethane, 2950 K for tetranitromethane, and 4100 K for pentaerythritol tetranitrate. In this paper we also compare the data with the chemical equilibrium models.

Near-infrared optical absorption in solid DT and T2

Abstract Near-infrared optical absorption has been detected for solid DT and T 2 samples. It is suggested that this absorption is due to electrons and/or ions resulting from the radioactive decay of tritium being trapped in the solid lattice.

Dielectric constant and electrical conductivity of liquid D-T☆

Abstract The first dielectric constant and electrical condutivity measurements on liquid deuterium-tritium are reported. The samples, which contain 0.9, 8.8, and 98.3% tritium, are measured for complex capacitance at 1592 Hz with an effective electric field of 2830 Vm −1 at temperatures of 20 to 26 K. The tritium radioactivity converts the samples dielectrics, with dielectric constant as large as 4.5 and electrical conductivities of 200 × 10 −9 (Ωm) −1 . Carrier densities are about 10 10 per mol sample; both free electrons and ions are apparently present.

Reaction of liquid and solid D2-T2

Collision-induced infrared spectroscopy has been used to measure the initial rate of the chemical exchange of equimolar D2 and T2 in liquid and solid forms from 9 to 23K over 23 to 45 h. If first-order kinetics are assumed, the time constant is 100-140 h for thermal equilibrium and 160-180 h for a hot-atom equilibrium. The latter is favoured, but cannot be confirmed. Approximately three DT molecules are formed per ion pair (using the gas-phase value of 36.6 eV/ion pair). A likely mechanism is reaction of the T2+ to the T3+ ion, followed by exchange. The slowness of the exchange suggests that molecular DT can be isolated and handled for fusion applications.

An estimate of the thermal conductivity of solid T2 from pulsed nmr data

Abstract The thermal conductivity of solid T 2 below 17 K has been estimated from pulsed nmr data to be roughly temperature independent and approximately equal to 0.7 W/mK. Results for some mixtures of T 2 with D 2 and DT are also given.