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We discuss the analyses of gated, x-ray imaging data from polar-direct-drive experiments with cryogenically layered deuterium–tritium targets on the OMEGA laser. The in-flight shell asymmetries were diagnosed at various times during the implosion, which was caused by the beam pointing geometry and preimposed variations in the energy partition between the different groups of laser beams. The shape of the ablation surface during the acceleration phase of the implosion was measured along two different lines of sight, and a Legendre mode ( ℓ-mode) decomposition was applied for modes of up to ten to investigate shell asymmetries. A clear causal relationship between the imposed beam imbalance and the shape of the in-flight shell asymmetries was observed. The imploded shell with a balanced energy ratio shows smaller values of the amplitudes of ℓ-mode 2 compared to that from implosions with an imbalanced ring energy ratio. The amplitudes of ℓ-modes 4 and 6 are the same within the measurement uncertainty with respect to the change in beam energy ratio.

The present paper discusses the development of the NaCl:K (10 −1 molar fraction of potassium) phosphor as dosimeter material for beta-radiation thermoluminescent dosimetry (TLD). The TLD grade NaCl:K(6T) material was prepared by annealing the NaCl:K powder obtained from aqueous solution by the method of recrystalization and annealed at 600°C for two hours in open air. It is observed that thermal glow curves of NaCl:K(6T) specimen exhibit well defined glow peak around 170°C alongwith a weaker peak at lower temperature. The high-temperature peak is found to grow supralinearily with increase in beta dose in the range 10–2×103 rad. Since the nature of glow curves under the influence of different doses remains more or less identical, it is believed that the phosphor does not undergo radiation damage and give high intrinsic TL around peak III. Examination of the system for fundamental dosimetry requirement shows that the NaCl:K(6T) material can be used as a suitable TLD material in beta radiation.

Thermoluminescene (TL) of synthetic quartz specimens under different physical conditions is investigated. An analysis for one of the prominent glow peaks has been done using the peak shape method. Further, on the basis of extracted trap level spectroscopic information, the results are explained. It is found that with different physical conditions characteristics of trapping level changes systematically.

NaCl:Tl(T) phosphor is found to have high intrinsic thermoluminescence (TL) sensitivity to 253.7 nm UV-radiation. The dosimetric glow peak II grows sublinearly with increase in UV dose in the range 103-106 JM−2. The other requirements of an efficient dosimeter material such as high storage stability, matching of the spectral response of detector tube and TL-emission from phosphor, reproducibility, desirable size and shape, easy availability in powder, pellet and crystal forms at cheaper rates, and repeated re-usability of the same phosphor without much difficulty, etc., are additional factors which strengthen the claim of NaCl:Tl(T) phosphor as UV dosimetric material. It is proposed that present NaCl:Tl(T) material is suitable TL-phosphor for UV dosimetry in the range 103-106 JM−2.

A detailed examination is presented of the thermoluminescence (TL) characteristics of untreated and heat-treated pure and Ba-doped NaCl exposed to gamma radiation at room temperature. The NaCl:Ba (10(-2) molar fraction) phosphor quenched from 750 degrees C, designated as NaCl:Ba(T), is found to give a pronounced TL output with a well-defined glow peak around 220 degrees C (peak III) along with other peaks at lower temperatures. It is suggested that the TL centre associated with glow peak III is comprised of an impurity-vacancy dipole with a negative ion vacancy in its vicinity. The TL centres are presumed to be located in the dislocation region. The dosimetric properties of peak III after gamma irradiation have also been examined. It is observed that most of the basic requirements of an efficient TLD material are fulfilled by the phosphor.

The present paper discusses the development of the NaCl: T1 (T), (10−3 m.f. of thallium concentration) phosphor as dosimeter material for beta-radiation thermoluminescent dosimetry (TLD). The TLD grade NaCl:Tl(T) powder was prepared by annealing the NaCl: Tl powder obtained from aqueous solution by method of crystallization at 750°C for two hours in open air. The thermoluminescence (TL) behaviours of NaCl :T1 (T) phosphor were examined in different physical situations. It is inferred from the present experimental work that, due to their high TL-efflciency, capability of registering beta-dose in the range 10–104 R, resistance to radiation damage and negligible fading, the NaCl:Tl(T) phosphors are found suitable for beta-dosimetry.

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Die Einflusse der Storstellenkonzentration sowie von thermischen und /oder mechanischen Vorbehandlungen auf die Phosphoreszenzabklinggeschwindigkeiten von NH4ClzTl-Phosphoren (dargestellt durch Kristallisation aus wasriger Losung) werden bei Raumtemp. fur die Emission im nahen UV untersucht.

It is known that thermal and/or mechanical pretreatment influences the luminescent behaviour of phosphors. It has been reported that mechanically pretreated NaCl : Tl specimens, exposed to ultraviolet radiation, exhibit a pronounced glow peak at 420 K. The present work concerns the study of the intensity of this peak as a function of impurity concentration. There is a remarkable growth in the intensity of the 420 K glow peak with decreasing concentration. This can be explained on the basis of the interaction between impurity ions and moving dislocations.

The phosphorescence decay rates of thallium-doped ammonium chloride (NH4Cl:Tl) phosphors, prepared by crystallization from aqueous solution, have been studied at room temperature for near-ultraviolet emission. The effects of impurity concentration as well as thermal and/or mechanical treatment on the decay rates have been examined. Phosphorescence centres consisting of a Tl+ion and a nearby negative ion vacancy are suggested to be responsible for the observed luminescence decay. The changes in the decay characteristics after pretreatments are explained on the basis of the location of the centres in normal and distorted regions of the host lattice.

Correlated measurements on the thermoluminescence and optical absorption of X-irradiated NaCl:Tl indicate that the glow peaks observed at 360 and 390°K may be due respectively to electrons released from F′ and some species of higher aggregate centres.

Thallium-doped NaCl crystals, x-irradiated at room temperature, were heated to 525 K for glow-curve measurements. The recorded glow curves show two definite peaks at 340 and 500 K. Study of the growth of these peaks with x-irradiation time indicates that the 500 K peak may be related to some species of interstitial clusters.