Enhanced Sensitivity Beam Emission Spectroscopy System for Nonlinear Turbulence Measurements

An upgraded Beam Emission Spectroscopy (BES) system has been deployed to access low amplitude turbulence regions near internal transport barriers on the DIII-D tokamak. Sixteen high sensitivity channels are being installed. A significant increase in total signal to noise is achieved by: 1.) Increased spatial volume sampling tailored to known turbulence characteristics; 2.) An increased throughput spectrometer assembly to isolate the local beam fluorescence, coupled to new large-area photoconductive photodiodes; 3.) A new sharp edge interference filter designed to optimize detection of the beam emission plus a significant fraction of the thermal deuterium charge exchange. A new data acquisition system has been installed, providing an 8 times increase in integration time or an increased sample rate. Preliminary results from the upgraded system show a signal enhancement of greater than an order of magnitude. A clear broadband density fluctuation signal is observed in H-mode discharges with the upgraded BES system, demonstrating the significant performance enhancement.Comment: HTPD-200

Turbulence regulation and stabilization by equilibrium and Time-varying sheared turbulence flows

Turbulence flows are directly measured in a tokamak plasma by applying time-delay-estimation (TDE) analysis to localized 2-D density fluctuation measurements obtained with Beam Emission Spectroscopy on DIII-D. The equilibrium radial flow shear near the plasma edge (0.8 < r/a < 1) varies strongly with magnetic geometry. With the ion grad-B drift directed towards the X-point in a single null plasma, a large radial shear in the poloidal flow is measured, while little shear is observed in the reverse condition. This large shear appears to facilitate the L-to H-mode transition, consistent with the significantly lower LH transition power threshold in this configuration. In addition, time varying, radially localized (k . ρI < 1) flows with a semi-coherent structure peaked near 15 KHz and a very long poloidal wavelength, possibly m=0, are observed. These characteristics are very similar to theoretically predicted zonal flows that are self-generated by and in turn regulate the turbulence

Visible charge exchange recombination spectroscopy on TFTR

Visible charge exchange recombination spectroscopy is routinely used to measure the time evolution of the ion temperature (T{sub i}) and toroidal rotation velocity (v{sub {phi}}) profiles on TFTR. These measurements are made with the CHERS diagnostic, a fiber-optically coupled spectrometer equipped with a two-dimensional photodiode array detector which provides both spectral and spatial resolution. The instrumentation, data analysis techniques, and examples of T{sub i} and v{sub {phi}} measurements are described. Recently, CHERS has been used to perform impurity transport experiments: radial profiles of diffusivities and convective velocities for helium and iron have been deduced from measurements of the time evolutions of He{sup 2+} and Fe{sup 24+} profiles following impurity injection. Examples of these measurements are given. 12 refs., 8 figs

Diagnostic suite used for magnetohydrodynamics equilibrium reconstruction on the PEGASUS

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Predictors of linkage to care following community-based HIV counseling and testing in rural Kenya

Despite innovations in HIV counseling and testing (HCT), important gaps remain in understanding linkage to care. We followed a cohort diagnosed with HIV through a community-based HCT campaign that trained persons living with HIV/AIDS (PLHA) as navigators. Individual, interpersonal, and institutional predictors of linkage were assessed using survival analysis of self-reported time to enrollment. Of 483 persons consenting to follow-up, 305 (63.2%) enrolled in HIV care within 3 months. Proportions linking to care were similar across sexes, barring a sub-sample of men aged 18–25 years who were highly unlikely to enroll. Men were more likely to enroll if they had disclosed to their spouse, and women if they had disclosed to family. Women who anticipated violence or relationship breakup were less likely to link to care. Enrolment rates were significantly higher among participants receiving a PLHA visit, suggesting that a navigator approach may improve linkage from community-based HCT campaigns.Vestergaard Frandse

Experience of violence and adverse reproductive health outcomes, HIV risks among mobile female sex workers in India

<p>Abstract</p> <p>Background</p> <p>Female sex workers (FSWs) are a population sub-group most affected by the HIV epidemic in India and elsewhere. Despite research and programmatic attention to FSWs, little is known regarding sex workers' reproductive health and HIV risk in relation to their experiences of violence. This paper therefore aims to understand the linkages between violence and the reproductive health and HIV risks among a group of mobile FSWs in India.</p> <p>Methods</p> <p>Data are drawn from a cross-sectional behavioural survey conducted in 22 districts from four high HIV prevalence states (Andhra Pradesh, Karnataka, Maharashtra, Tamil Nadu) in India between September 2007 and July 2008. The survey sample included 5,498 FSWs who had moved to at least two different places for sex work in the past two years, and are classified as mobile FSWs in the current study. Analyses calculated the prevalence of past year experiences of violence; and adjusted logistic regression models examined the association between violence and reproductive health and HIV risks after controlling for background characteristics and program exposure.</p> <p>Results</p> <p>Approximately one-third of the total mobile FSWs (30.5%, n = 1,676) reported experiencing violence at least once in the past year; 11% reported experiencing physical violence, and 19.5% reported experiencing sexual violence. Results indicate that FSWs who had experienced any violence (physical or sexual) were significantly more likely to be vulnerable to both reproductive health and HIV risks. For example, FSWs who experienced violence were more likely than those who did not experience violence to have experienced a higher number of pregnancies (adjusted odds ratio [OR] = 1.2, 95% confidence interval [CI] = 1.0-1.6), ever experienced pregnancy loss (adjusted OR = 1.4, 95% CI = 1.2-1.6), ever experienced forced termination of pregnancy (adjusted OR = 2.4, 95% CI = 2.0-2.7), experienced multiple forced termination of pregnancies (adjusted OR = 2.2, 95% CI = 1.7-2.8), and practice inconsistent condom use currently (adjusted OR = 1.97, 95% CI: 1.4-2.0). Among FSWs who experienced violence, those who experienced sexual violence were more likely than those who had experienced physical violence to report inconsistent condom use (adjusted OR = 1.8, 95% CI: 1.4-2.3), and experience STI symptoms (adjusted OR = 1.3, 95% CI: 1.1-1.7).</p> <p>Conclusion</p> <p>The pervasiveness of violence and its association with reproductive health and HIV risk highlights that the abuse in general is an important determinant for reproductive health risks; and sexual violence is significantly associated with HIV risks among those who experienced violence. Existing community mobilization programs that have primarily focused on empowering FSWs should broaden their efforts to promote reproductive health in addition to the prevention of HIV among all FSWs, with particular emphasis on FSWs who experienced violence.</p