A new visible spectroscopy diagnostic for the JET ITER-like wall main chamber.

In preparation for ITER, JET has been upgraded with a new ITER-like wall (ILW), whereby the main plasma facing components, previously of carbon, have been replaced by mainly Be in the main chamber and W in the divertor. As part of the many diagnostic enhancements, a new, survey, visible spectroscopy diagnostic has been installed for the characterization of the ILW. An array of eight lines-of-sight (LOS) view radially one of the two JET neutral beam shine through areas (W coated carbon fibre composite tiles) at the inner wall. In addition, one vertical LOS views the solid W tile at the outer divertor. The light emitted from the plasma is coupled to a series of compact overview spectrometers, with overall wavelength range of 380-960 nm and to one high resolution Echelle overview spectrometer covering the wavelength range 365-720 nm. The new survey diagnostic has been absolutely calibrated in situ by means of a radiometric light source placed inside the JET vessel in front of the whole optical path and operated by remote handling. The diagnostic is operated in every JET discharge, routinely monitoring photon fluxes from intrinsic and extrinsic impurities (e.g., Be, C, W, N, and Ne), molecules (e.g., BeD, D(2), ND) and main chamber and divertor recycling (typically Dα, Dß, and Dγ). The paper presents a technical description of the diagnostic and first measurements during JET discharges.

Enhancements to the JET poloidally scanning vacuum ultraviolet∕visible spectrometers.

Enhancements to the JET poloidally scanning spectrometers are presented, which will aid the exploitation of the recently installed ITER-like wall in JET. They include the installation of visible filter∕photomultiplier tube assemblies and spectrometers and the replacement of large rotating mirrors in the JET vacuum with small oscillating mirrors outside. The upgrade has resulted in a more robust and reliable diagnostic than before, which is described. Drifts in the mirror angle reconstructed from quadrature encoder signals are found, a reference signal being required. The use of the small scanning mirrors necessitated the inclusion of focusing mirrors to maintain throughput into the vacuum ultraviolet spectrometers. The mirror design has taken account of the extreme sensitivity of the focusing to the grazing angle of incidence, an aspect of importance in the design of grazing incidence focusing components on future machines, such as ITER. The visible system has been absolutely calibrated using an in-vessel light source.

Quantitative ultrastructural study of boutons of ascending afferents to the feline lateral cervical nucleus.

A quantitative ultrastructural study has been performed of 300 labelled and the same number of unlabelled boutons in the feline lateral cervical nucleus (LCN) of 5 adult cats after cervical or lumbar injections of lectin-conjugated horseradish peroxidase and histochemical reaction with tetramethylbenzidine. On an average the labelled boutons were slightly elongated, had areas of 2.25 micron 2, mitochondrial volume fractions of 11.2% and densities of synaptic vesicles of 35.4.micron-2. The synaptic vesicles were round to flattened with a mean length of 60 nm and length/width ratios of 1.21. The labelled boutons were significantly larger and had significantly lower densities of synaptic vesicles than the unlabelled boutons. The labelled boutons constituted about 14% of the bouton volume of the investigated areas of the LCN. Most of them were axo-dendritic and about 16% synapsed with cell bodies with ultrastructural characteristics similar to the cervico-thalamic projection neurones of the LCN. The number of boutons labelled after the injections comprising 3-5 adjacent segments of the spinal cord was calculated to 6.8 X 10(6). Based on the assumption that they represented terminals of spinocervical tract cells, it was calculated that each of these cells in the lumbar cord gives rise to an average of 4400 boutons in the LCN.

Stereological analysis of coated pits and secondary lysosomes in cultured human glial and glioma cells.

The frequency, distribution and size of coated pits along the upper and lower cell surfaces, and the cytoplasmic volume density of secondary lysosomes were studied by ultrastructural stereological methods in sparse and post-confluent cell cultures of a human normal glial line and a human malignant glioma line. Neither the frequency of coated pits nor the volume density of secondary lysosomes showed any statistically significant changes between the normal glial cells at 2 and 14 days after subcultivation. The numerical surface density of the coated pits was significantly higher along the lower cell surface than on the upper free surface. The coated pits on the malignant glioma cells at 14 days were far more frequent than at 2 days after subcultivation, or than on the sparse and post-confluent glial cells. The surface density of the coated pits was higher along the upper free cell surface than on the lower surface of the glioma cells, in contrast to the glial cells. The volume density of lysosomes was significantly higher in the post-confluent glioma cells than in the sparse cells. The mean diameter of the coated pit openings on cells at 2 days after subcultivation was significantly larger than at 14 days, both in the glial and glioma cell cultures. The observed differences in frequency and distribution of coated pits between the glial and glioma cells may reflect differences in receptor-mediated endocytosis and be related to the different growth characteristics of the normal and malignant cells. The greatly increased load of secondary lysosomes in post-confluent cultures of the glioma cells, in contrast to the glial cells, may be due to a higher rate of autophagocytosis in the malignant cells. The larger size of the coated pit openings on isolated than on post-confluent cells may reflect differences in surface properties between sparse and dense cells.

Volume composition of the lateral cervical nucleus in the cat. I. A stereological and electron microscopical study of normal and deafferentated animals.

The neuropil of the lateral cervical nucleus (LCN) has been studied by means of ultrastructural stereological methods. Estimates of the fractional volumes of axons, glial cells (three types), extracellular space, boutons, bouton mitochondria, dendrites, dendritic mitochondria, neuronal somata and blood vessels were calculated for four normal cats and eight cats which had been subjected to spinal deafferentation 2, 4, 9, and 14 days before perfusion. 14 days after operation the fractional volume of boutons and dendrites in the nucleus was considerably lower on the operated side, corresponding to a reduction of 67% and 64% respectively. The bouton reduction was higher than could have been expected from findings in earlier qualitative studies. The reduction in dendritic volume, which was already present after 4 days, had not been detected in earlier studies of the LCN. Dark dendrites were found both in normal animals and on the normal and operated sides in operated animals. The variation from animal to animal was great but the figures for the deafferented sides were significantly higher. The general value of the stereological technique in ultrastructural neuroanatomical research is discussed and it is concluded that quantitative methods are more sensive to small and gradual changes and should give a better estimation of transneuronal effects and of the amount of degeneration than purely qualitative methods.