Development of plasma bolometers using fiber-optic temperature sensors

Measurements of radiated power in magnetically confined plasmas are important for exhaust studies in present experiments and expected to be a critical diagnostic for future fusion reactors. Resistive bolometer sensors have long been utilized in tokamaks and helical devices but suffer from electromagnetic interference (EMI). Results are shown from initial testing of a new bolometer concept based on fiber-optic temperature sensor technology. A small, 80 μm diameter, 200 μm long silicon pillar attached to the end of a single mode fiber-optic cable acts as a Fabry–Pérot cavity when broadband light, λo ∼ 1550 nm, is transmitted along the fiber. Changes in temperature alter the optical path length of the cavity primarily through the thermo-optic effect, resulting in a shift of fringes reflected from the pillar detected using an I-MON 512 OEM spectrometer. While initially designed for use in liquids, this sensor has ideal properties for use as a plasma bolometer: a time constant, in air, of ∼150 ms, strong absorption in the spectral range of plasma emission, immunity to local EMI, and the ability to measure changes in temperature remotely. Its compact design offers unique opportunities for integration into the vacuum environment in places unsuitable for a resistive bolometer. Using a variable focus 5 mW, 405 nm, modulating laser, the signal to noise ratio versus power density of various bolometer technologies are directly compared, estimating the noise equivalent power density (NEPD). Present tests show the fiber-optic bolometer to have NEPD of 5-10 W/m2 when compared to those of the resistive bolometer which can achieve <0.5 W/m2 in the laboratory, but this can degrade to 1-2 W/m2 or worse when installed on a tokamak. Concepts are discussed to improve the signal to noise ratio of this new fiber-optic bolometer by reducing the pillar height and adding thin metallic coatings, along with improving the spectral resolution of the interrogator

D-cycloserine increases positive symptoms in chronic schizophrenic patients when administered in addition to antipsychotics: A double-blind, parallel, placebo-controlled study

A hypofunction of the glutamatergic system and NMDA receptors in schizophrenia has been hypothesized. Therefore, stimulation of these receptors could be of benefit to patients with schizophrenia. D-cycloserine has been used for this purpose. This study reports the effects of 100 mg D-cyclo-serine, when added to typical antipsychotics in chronic schizophrenic patients exhibiting prominent negative symptoms, using a placebo-controlled, double-blind, parallel, design. D-cycloserine slightly worsened psychotic symptoms and general psychopathology as compared to placebo. D-cycloserine failed to change negative symptoms and had no effect on extrapyramidal symptoms. The exacerbation of schizophrenic symptoms may be explained by the antagonistic effects of this dose of D-cycloserine at the glycine recognition site of the NMDA receptor due to competition with the endogenous agonist glycine. Another explanation for the increase in psychopathology may be an interaction with the effects of antipsychotics on NMDA mediated neurotransmission. Thus, D-cycloserine in this study did not ameliorate schizophrenic symptoms. However, the fact that they actually worsened suggests that NMDA systems may be involved in the pathogenesis of schizophrenia. Further placebo-controlled studies with lower dosages of D-cycloserine, preferably in drug-free patients, are necessary to evaluate if D-cycloserine is of use for the treatment of patients with schizophrenia. Copyright (C) 1999 American College of Neuropsychopharmacology