Experimental examination of a method to estimate temporal effect by neutrons and γ-rays on scintillation light in scintillator-based soft x-ray diagnostic of experimental advanced superconducting tokamak and large helical device.

Scintillators, which are more tolerant of neutrons or γ-rays than semiconductors, are a promising candidate for soft X-ray (SX) diagnostics in high neutron flux environments such as JT-60SA or ITER. Although scintillators are tolerant of radiations, neutrons and γ-rays can cause scintillation light and become noise on SX signals. Therefore, a method to estimate the temporal effect by the radiations on SX signals and an appropriate design of the radiation shield based on the estimation are required. In previous studies, it has been proposed for estimating the effect by the radiations to calculate the absorption powers due to SXs, neutrons, and γ-rays in scintillators assuming that amplitudes of scintillation light are proportional to the absorption powers. In this study, an experimental examination of this proposal is conducted in the Experimental Advanced Superconducting Tokamak (EAST). It is shown that the proposal may be valid in the examination of EAST. In addition to results in EAST, initial results of a multi-channel scintillator-based SX diagnostic in the Large Helical Device (LHD) are introduced. Although a scintillator-based SX diagnostic in LHD observes oscillations of SXs by magnetohydrodynamic (MHD) phenomena successfully, the observed temporal effect on SX signals by neutrons or γ-rays is more significant than the expected effect, which is estimated by calculating the absorption powers. One of the possible reasons for the contradiction between the results in EAST and LHD is unexpected γ-rays around the scintillators in LHD. Although the temporal effect by the radiations is significant in the current system of LHD, the degradation of amplitudes of SX signals after the deuterium plasma experiments is not observed with the current level of the fluence. The scintillator-based SX diagnostic in LHD may work as a diagnostic to research MHD instabilities in deuterium plasma experiments without additional maintenance during an experimental campaign by making the pinhole larger or setting an additional radiation shield.

Assessment of the beam path deflection for a vertically installed microwave interferometer in SUNIST.

Microwave interferometry has been widely employed to provide reliable line averaged electron density measurement on plasma devices. For a vertically installed interferometer on a tokamak, the refraction problem, which distorts the beam path and aggravates power loss at the receiving antenna, may become significant if taking the cross section shape into account. Increasing the frequency of the probing microwave can alleviate the distortion, but at the expense of losing the density resolution. To seek for an optimized frequency, previous calculations are mainly based on the cylindrical column geometry which grossly underestimates the deflection of the beam path induced by the plasma shape, and empirical suggestions indicating ne0/nc = 1/2 ∼ 1/3 may not always be the appropriate option. Here a single ray tracing method is applied to estimate the final horizontal deviation at the receiving antenna, which is supposed to represent the level of power loss. The calculation is carried out under the real tokamak geometry in Sino-UNIted Spherical Tokamak (SUNIST) with the cross section parameters obtained from the equilibrium reconstruction, and the result indicates that for a target density of 1.2 × 10(19) m(-3), a frequency of at least 100 GHz is desirable to reduce the power loss to an acceptable level. This would be helpful for the design of a vertically installed interferometer on SUNIST.

Comparison of anomalous Doppler resonance effects with molybdenum and graphite limiters on HT-7.

The material of limiter in HT-7 tokamak was changed from graphite to molybdenum in the last experimental campaign. The pitch angle scattering of runaway electrons due to anomalous Doppler resonance effects was observed. The experimental results agree very well with the stable boundary condition expected from the linear resistive theory but only agree with that from the nonlinear evolutionary of runaway-electron distribution theory in low electric field region. The current carried by runaway electrons is the same under different limiter conditions.

Packed capillary liquid chromatography coupled to fluorescence detection: application to human blood samples for the determination of glutathione.

The present investigation analyses the potentials of capillary chromatography using packed fused silica capillaries filled with 5 microns RP-18 for the fluorescence determination of glutathione in human blood samples. Adaptation of conventional HPLC equipment for miniaturized chromatographic assays proved successful. Sample preparation was relatively simple, though care should be taken in sample handling. The thiolic compound mercaptoethanol was used as internal standard. Qualitative determinations were based on standard addition providing increased peak heights at identical retention times. Quantitative determinations gave linear calibration curves, with a standard glutathione recovery of 98.9% and an intra-assay reproducibility of 3.3%. The glutathione values measured appeared within the normal range of 0.9-1.7 mmol glutathione per litre of blood.

Application of micro-scale liquid chromatography with fluorescence detection to the determination of thiols.

Different thiol compounds of biological and pharmacological interest were separated on a packed reversed-phase fused-silica capillary column and determined with fluorescence detection. Conventional inexpensive liquid chromatographic equipment could be adapted for such purposes, providing a highly efficient analytical system. The different compounds were derivatized with the fluorogenic reagents SBD-F and ABD-F and chromatographed both isocratically and in the gradient mode in order to separate a series of thiols with widely varying polarities. Subsequently the derivatives were measured at lambda ex. = 380 nm and lambda em. = 510 nm. Application of the system to biological and pharmacological samples is suggested.

Principles and applications of luminescence spectrometry coupled to liquid chromatographic techniques.

An overview is presented of the physicochemical basis of luminescence, and its application to the detection of chemicals (drugs, biomedically important compounds, environmentally active substances) in liquid chromatographic systems.

Analytical applications of enhanced drug luminescence.

Luminescence emission from drugs is strongly dependent on their physicochemical environment. Several biomedically and environmentally important compounds and pharmaceuticals exhibit sufficient intrinsic luminescence properties to allow their determination by high-performance liquid chromatography (HPLC) with fluorimetric, chemiluminescence or room temperature phosphorimetric detection. In the case of weakly fluorescing compounds it is possible to use the dependence of the emitted radiation on the molecular environment at the moment of measurement. The composition of the eluent, i.e. solvents, added salts and buffers, pH and ionic strength, oxygen content and temperature, are of the highest importance for the luminescence detection of drugs in solution (e.g. in liquid chromatography) or adsorbed onto solid surfaces (e.g. in thin-layer chromatography). Post-column or post-plate acid-base manipulation and the use of specific reagents may remarkably enhance the observed luminescence of several molecules. The term "enhancement" of luminescence comprises various sample treatments leading to an increase of the emitted radiation. These treatments include the addition of non-fluorescent compounds to, or the creation of organized media (surfactants, cyclodextrins, heavy atoms) in, the sample to be measured. They may also involve changes in molecular environment, pH, the application of excessive drying conditions, the removal of oxygen, the protection of adsorbed compounds against non-radiative decay mechanisms by means of specific spraying or dipping conditions, amongst others. The use of organized media in luminescence spectroscopy is growing. Many of the recent studies have involved micelles for enhancing the fluorescence, room temperature phosphorescence and chemiluminescence of several chemicals. Cyclodextrins are increasingly used for various analytical applications. Liquid paraffin, triethanolamine, dodecane, Triton X-100 and Fomblin Y-Vac are commonly used fluorescence enhancers in chromatographic assays. Examples of these systems in drug analysis are presented.

Determination of thiols of biological and pharmacological interest by high-performance thin-layer chromatography and fluorescence scanning densitometry.

The application of high-performance thin-layer chromatography (HPTLC) with fluorescence scanning densitometry provides a simple, rapid and reliable system for the qualitative and quantitative determination of several thiols of biological and pharmacological interest. The determination of a mixture of thiols (captopril, coenzyme A, cysteamine, cysteine and glutathione), together with their disulphides may readily be performed by pre-chromatographic derivatization with the thiol-specific fluorobenzoxadiazole reagents SBD-F and ABD-F, followed by HPTLC separation on silica gel plates using isopropyl ether-methanol-water-acetic acid (9:8:2:1, v/v/v/v) as the developing solvent, and fluorodensitometric measurement of the fluorescing derivatives. Detection limits of about 30 pg (coenzyme A) to 6 pg (cysteamine) per spot were achieved; the relative standard deviation (RSD) of the complete procedure was 1.16-3.2%.

Use of enhancers in the HPTLC fluorescence analysis of thiols.

Several thiols of biological and pharmacological interest, including glutathione, coenzyme A, acetylcysteine and captopril were derivatized with the fluorogenic reagents SBD-F and ABD-F and analysed by high-performance thin-layer chromatography (HPTLC)-fluorodensitometry on silica gel 60 plates, using isopropyl ether-methanol-water-acetic acid (9:8:2:1, v/v/v/v) as the developing solvent. The luminescence was considerably increased when several types of enhancers were applied as dipping reagents: Triton X-100, liquid paraffin and cyclodextrins; thus the detectability of the thiol fluorophores was improved. The influence of enhancer concentration, method of application, sample concentration, drying conditions and measuring time after plate dipping were investigated. The greatest enhancement was achieved using a 40% (v/v) solution of Triton X-100 in toluene as a dipping reagent for the determination of SBD-acetylcysteine; more than a 10-fold increase of the fluorescence signal was obtained, allowing low picogram detection limits.