A collective scattering system for measuring electron gyroscale fluctuations on the National Spherical Torus Experiment

A collective scattering system has been installed on the National Spherical Torus Experiment (NSTX) to measure electron gyroscale fluctuations in NSTX plasmas. The system measures fluctuations with k(perpendicular to)rho(e)less than or similar to 0.6 and k(perpendicular to)less than or similar to 20 cm(-1). Up to five distinct wavenumbers are measured simultaneously, and the large toroidal curvature of NSTX plasmas provides enhanced spatial localization. Steerable optics can position the scattering volume throughout the plasma from the magnetic axis to the outboard edge. Initial measurements indicate rich turbulent dynamics on the electron gyroscale. The system will be a valuable tool for investigating the connection between electron temperature gradient turbulence and electron thermal transport in NSTX plasmas.X1137sciescopu

Discursive chains: How prison becomes real and chains identity movements for a sex offender

Detainees enact a "self" that is faced with the prejudices and stereotypes of the crime for which that detainee was convicted. Of all inmates, sex offenders face the greatest risk of receiving social condemnation alongside their prison sentence. This empirical study worked with 32 male sex offenders over 18 years old that were housed in the "protected" unit of the Due Palazzi. The following analysis explores how these men are required to manage their "self," hetero-narrations, perception of everyday interactions in the protected unit, and conceptions about the rehabilitation path. Moreover, the detainees' view on the prison's strategic opportunities for promoting effective change in their condition and identity are also examined. Discourse analysis applied to an open answer questionnaire showed that, rather than facing the stigma assigned to them, the detainees tend to minimize the importance of storytelling and construct alternative biographies to share with other inmates. Managing narratives allows the sex offenders to distance themselves from the perceived threats of living with other detainees; however, it also prevents the re-signification of their offenses. As such, the rules of "secrecy" must be considered by both qualitative researchers who conduct studies in prisons and prison administrators who plan the housing and treatment of sex offenders

Threshold Photo/Electro Pion Production - Working Group Summary

We summarize the pertinent experimental and theoretical developments in the field of pion photo- and electroproduction in the threshold region. We discuss which experiments and which calculations should be done/performed in the future.Comment: plain TeX (macro included), 6pp, summary talk presented at the workshop on "Chiral Dynamics: Theory and Experiments", MIT, July 25-29, 199

Small-scale density fluctuations in the adiabatic toroidal compressor

A new class of density fluctuations has been observed in the ATC tokamak by using spectral analysis of scattered microwaves. The observed frequency spectrum is consistent with that of drift waves with amplitudes that are maximum in the wavelength range 0.5 to 1.0 cm where finite ion Larmor radius effects are important for plasma stability. The total density fluctuation is n tilde/sub e/ greater than or equal to 5 x 10$sup -3$ anti n/sub e/. It is estimated that these fluctuations could account for a large fraction of the electron energy losses of the ATC discharge. (auth

Numerical Study of Microwave Reflectometry in Plasmas with 2D Turbulent Fluctuations

This paper describes a numerical study of the role played by 2D turbulent fluctuations in microwave reflectometry -- a radar technique for density measurements using the reflection of electromagnetic waves from a plasma cutoff. The results indicate that, if the amplitude of fluctuations is below a threshold which is set by the spectrum of poloidal wavenumbers, the measured backward field appears to originate from a virtual location behind the reflecting layer, and to arise from the phase modulation of the probing wave, with an amplitude given by 1D geometric optics. These results suggest a possible scheme for turbulence measurements in tokamaks, where the backward field is collected with a wide aperture antenna, and the virtual reflecting layer is imaged onto the plane of an array of detectors. Such a scheme should be capable of providing additional information on the nature of the short-scale turbulence observed in tokamaks, which still remains one of the unresolved issues in fusion research

Microwave Reflectometry for Magnetically Confined Plasmas

This paper is about microwave reflectometry -- a radar technique for plasma density measurements using the reflection of electromagnetic waves by a plasma cutoff. Both the theoretical foundations of reflectometry and its practical application to the study of magnetically confined plasmas are reviewed in this paper. In particular, the role of short-scale density fluctuations is discussed at length, both as a unique diagnostic tool for turbulence studies in thermonuclear plasmas and for the deleterious effects that fluctuations may have on the measurement of the average plasma density with microwave reflectometry

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Electron gyroscale fluctuation measurements in National Spherical Torus Experiment H-mode plasmas

A collective scattering system has measured electron gyroscale fluctuations in National Spherical Torus Experiment [M. Ono et al., Nucl. Fusion 40, 557 (2000)] H-mode plasmas to investigate electron temperature gradient (ETG) turbulence. Observations and results pertaining to fluctuation measurements in ETG-stable regimes, the toroidal field scaling of fluctuation amplitudes, the relation between fluctuation amplitudes and transport quantities, and fluctuation magnitudes and k-spectra are presented. Collectively, the measurements provide insight and guidance for understanding ETG turbulence and anomalous electron thermal transport. (C) 2009 American Institute of Physics. [doi:10.1063/1.3262530]X116sciescopu