The National Spherical Torus Experiment-Upgrade poloidal high-k scattering system pitch angle design modifications.

A 693 GHz, eight-channel, poloidal high-k (k refers to wavenumber) collective scattering system is under development for the National Spherical Torus Experiment-Upgrade device. It will replace the previous 280 GHz, five-channel, tangential scattering system to study high-k electron density fluctuations, thereby providing a measurement of the kθ-spectrum of both electron temperature gradient and ion temperature gradient modes. A tool is under development to calculate the wavenumber that exists in the presence of strong magnetic pitch angles. We use this tool to motivate a new receiver optical design for significantly improved performance, details of which are presented herein.

Spatial calibration and synthetic diagnostic of a multi-energy hard x-ray camera at WEST tokamak.

WEST (tungsten environment in steady-state tokamak) is starting operation for the first time with a water-cooled full tungsten divertor, enabling long pulse operation. Heating is provided by radiofrequency systems, including lower hybrid current drive (LHCD). In this context, a compact multi-energy hard x-ray camera has been installed for energy and space-resolved measurements of the electron temperature, the fast electron tail density produced by LHCD and runaway electrons, and the beam-target emission of tungsten at the target due to fast electron losses interacting with the divertor plates. The diagnostic is a pinhole camera based on a 2D pixel array detector (Pilatus 3 CdTe CMOS Hybrid-Pixel detector produced by DECTRIS). The novelty of this diagnostic technique is the detector's capability of adjusting the threshold energy at pixel level. This innovation provides great flexibility in the energy configuration, allowing simultaneous space and energy-resolved x-ray measurements. This contribution details two important steps in the preparation of the diagnostic operation. First, the in-vessel spatial calibration that was carried out with a radioactive source. Second, the synthetic diagnostic is obtained by the suite of codes ALOHA/C3PO/LUKE/R5-X2, which simulates LH wave propagation and absorption, as well as the fast electron bremsstrahlung production.

Multi-energy reconstructions, central electron temperature measurements, and early detection of the birth and growth of runaway electrons using a versatile soft x-ray pinhole camera at MST.

A multi-energy soft x-ray pinhole camera has been designed, built, and deployed at the Madison Symmetric Torus to aid the study of particle and thermal transport, as well as MHD stability physics. This novel imaging diagnostic technique employs a pixelated x-ray detector in which the lower energy threshold for photon detection can be adjusted independently on each pixel. The detector of choice is a PILATUS3 100 K with a 450 µm thick silicon sensor and nearly 100 000 pixels sensitive to photon energies between 1.6 and 30 keV. An ensemble of cubic spline smoothing functions has been applied to the line-integrated data for each time-frame and energy-range, obtaining a reduced standard-deviation when compared to that dominated by photon-noise. The multi-energy local emissivity profiles are obtained from a 1D matrix-based Abel-inversion procedure. Central values of Te can be obtained by modeling the slope of the continuum radiation from ratios of the inverted radial emissivity profiles over multiple energy ranges with no a priori assumptions of plasma profiles, magnetic field reconstruction constraints, high-density limitations, or need of shot-to-shot reproducibility. In tokamak plasmas, a novel application has recently been tested for early detection, 1D imaging, and study of the birth, exponential growth, and saturation of runaway electrons at energies comparable to 100 × Te,0; thus, early results are also presented.

A new class of focusing crystal shapes for Bragg spectroscopy of small, point-like, x-ray sources in laser produced plasmas.

This paper describes a new class of focusing crystal forms for the x-ray Bragg crystal spectroscopy of small, point-like, x-ray sources. These new crystal forms are designed with the aid of sinusoidal spirals, a family of curves, whose shapes are defined by only one parameter, which can assume any real value. The potential of the sinusoidal spirals for the design x-ray crystal spectrometers is demonstrated with the design of a toroidally bent crystal of varying major and minor radii for measurements of the extended x-ray absorption fine structure near the Ta-L3 absorption edge at the National Ignition Facility.

Calibration of a versatile multi-energy soft x-ray diagnostic for WEST long pulse plasmas.

A compact multi-energy soft x-ray diagnostic is being installed on the W Environment in Steady-state Tokamak (WEST), which was designed and built to test ITER-like tungsten plasma facing components in a long pulse (∼1000 s) scenario. The diagnostic consists of a pinhole camera fielded with the PILATUS3 photon-counting Si-based detector (≲100 kpixel). The detector has sensitivity in the range 1.6-30 keV and enables energy discrimination, providing a higher energy resolution than conventional systems with metal foils and diodes with adequate space and time resolution (≲1 cm and 2 ms). The lower-absorption cut-off energy is set independently on each one of the ∼100 kpixels, providing a unique opportunity to measure simultaneously the plasma emissivity in multiple energy ranges and deduce a variety of plasma parameters (e.g., Te, nZ, and ΔZeff). The energy dependence of each pixel is calibrated here over the range 3-22 keV. The detector is exposed to a variety of monochromatic sources-fluorescence emission from metallic targets-and for each pixel, the lower energy threshold is scanned to calibrate the energy dependence. The data are fit to a responsivity curve ("S-curve") that determines the mapping between the possible detector settings and the energy response for each pixel. Here, the calibration is performed for three energy ranges: low (2.3-6 keV), medium (4.5-13.5 keV), and high (5.4-21 keV). We determine the achievable energy resolutions for the low, medium, and high energy ranges as 330 eV, 640 eV, and 950 eV, respectively. The main limitation for the energy resolution is found to be the finite width of the S-curve.

Multi-energy calibration of a PILATUS3 CdTe detector for hard x-ray measurements of magnetically confined fusion plasmas.

A multi-energy hard x-ray pin-hole camera based on the PILATUS3 X 100K-M CdTe detector has been developed at the Princeton Plasma Physics Laboratory for installation on the Tungsten Environment in Steady State Tokamak. This camera will be employed to study thermal plasma features such as electron temperature as well as non-thermal effects such as fast electron tails produced by a lower hybrid radiofrequency current drive and the birth of runaway electrons. The innovative aspect of the system lies in the possibility of setting the threshold energy independently for each of the ∼100k pixels of the detector. This feature allows for the measurement of the x-ray emission in multiple energy ranges with adequate space and time resolution (∼1 cm, 2 ms) and coarse energy resolution. In this work, the energy dependence of each pixel was calibrated within the range 15 keV-100 keV using a tungsten x-ray tube and emission from a variety of fluorescence targets (from yttrium to uranium). The data corresponding to pairs of Kα emission lines are fit to the characteristic responsivity ("S-curve"), which describes the detector sensitivity across the 64 possible energy threshold values for each pixel; this novel capability is explored by fine-tuning the voltage of a six-bit digital-analog converter after the charge-sensitive amplifier for each of the ∼100k pixels. This work presents the results of the calibration including a statistical analysis. It was found that the achievable energy resolution is mainly limited by the width of the S-curve to 3 keV-10 keV for threshold energies up to 50 keV, and to ≥20 keV for energies above 60 keV.

The high-k poloidal scattering system for NSTX-U.

An 8-channel, high-k poloidal far-infrared (FIR) scattering system is under development for the National Spherical Torus eXperiment Upgrade (NSTX-U). The 693 GHz poloidal scattering system replaces a 5-channel, 280 GHz high-k toroidal scattering system to study high-k electron density fluctuations on NSTX-U. The FIR probe beam launched from Bay G is aimed toward Bay L, where large aperture optics collect radiation at 8 simultaneous scattering angles ranging from 2° to 15°. The reduced wavelength in the poloidal system results in less refraction, and coupled with a new poloidal scattering geometry, extends measurement of poloidal wavenumbers from the previous limit of 7 cm-1 up to >40 cm-1. Steerable launch optics coupled with receiver optics that can be remotely translated in 5 axes allow the scattering volume to be placed from r/a = 0.1 out to the pedestal region (r/a ∼ 0.99) and allow for both upward and downward scattering to cover different regions of the 2D fluctuation spectrum.

A new toroidal x-ray crystal spectrometer for the diagnosis of high energy density plasmas at the National Ignition Facility.

The here-described spectrometer was developed for the extended x-ray absorption fine structure spectroscopy of high-density plasmas at the National Ignition Facility. It employs as the Bragg reflecting element a new type of toroidally bent crystal with a constant and very large major radius R and a much smaller, locally varying, minor radius r. The focusing properties of this crystal and the experimental arrangement of the source and detector make it possible to (a) fulfill the conditions for a perfect imaging of an ideal point source for each wavelength, (b) obtain a high photon throughput, (c) obtain a high spectral resolution by eliminating the effects of source-size broadening, and (d) obtain a one-dimensional spatial resolution with a high magnification perpendicular to the main dispersion plane.

A computational tool for simulation and design of tangential multi-energy soft x-ray pin-hole cameras for tokamak plasmas.

A new tool has been developed to calculate the spectral, spatial, and temporal responses of multi-energy soft x-ray (ME-SXR) pinhole cameras for arbitrary plasma densities (n e,D), temperature (T e), and impurity densities (n Z). ME-SXR imaging provides a unique opportunity for obtaining important plasma properties (e.g., T e, n Z, and Z eff) by measuring both continuum and line emission in multiple energy ranges. This technique employs a pixelated x-ray detector in which the lower energy threshold for photon detection can be adjusted independently. Simulations assuming a tangential geometry and DIII-D-like plasmas (e.g., n e,0 ≈ 8 × 1019 m-3 and T e,0 ≈ 2.8 keV) for various impurity (e.g., C, O, Ar, Ni, and Mo) density profiles have been performed. The computed brightnesses range from few 102 counts pixel-1 ms-1 depending on the cut-off energy thresholds, while the maximum allowable count rate is 104 counts pixel-1 ms-1. The typical spatial resolution in the mid-plane is ≈0.5 cm with a photon-energy resolution of 500 eV at a 500 Hz frame rate.

Simulation, design, and first test of a multi-energy soft x-ray (SXR) pinhole camera in the Madison Symmetric Torus (MST).

A multi-energy soft x-ray pinhole camera has been designed and built for the Madison Symmetric Torus reversed field pinch to aid the study of particle and thermal-transport, as well as MHD stability physics. This novel imaging diagnostic technique combines the best features from both pulse-height-analysis and multi-foil methods employing a PILATUS3 x-ray detector in which the lower energy threshold for photon detection can be adjusted independently on each pixel. Further improvements implemented on the new cooled systems allow a maximum count rate of 10 MHz per pixel and sensitivity to the strong Al and Ar emission between 1.5 and 4 keV. The local x-ray emissivity will be measured in multiple energy ranges simultaneously, from which it is possible to infer 1D and 2D simultaneous profile measurements of core electron temperature and impurity density profiles with no a priori assumptions of plasma profiles, magnetic field reconstruction constraints, high-density limitations, or need of shot-to-shot reproducibility. The expected time and space resolutions will be 2 ms and <1 cm, respectively.

Experimental tests of an infrared video bolometer on Alcator C-Mod.

A prototype of an infrared imaging bolometer (IRVB) was successfully tested on the Alcator C-Mod tokamak at the end of its 2016 campaign. The IRVB method interprets the power radiated from the plasma by measuring the temperature rise of a thin, ∼2 µm, Pt absorber that is placed in the torus vacuum and exposed, using a pinhole camera, to the full-spectrum of plasma's photon emission. The IRVB installed on C-Mod viewed the poloidal cross section of the core plasma and observed Ohmic and ion cyclotron range of frequency (ICRF)-heated plasmas. Analysis of total radiated power and on-axis emissivity from IRVB is summarized, and quantitative comparisons made to data from both resistive bolometers and AXUV diodes. IRVB results are clearly within a factor of two, but additional effort is needed for it to be used to fully support power exhaust research. The IRVB is shown to be immune to electromagnetic interference from ICRF which strongly impacts C-Mod's resistive bolometers. Results of the bench-top calibration are summarized, including a novel temperature calibration method useful for IRVBs.

Cutaneous HIV-associated Kaposi sarcoma: a potential setting for management by clinical observation.

Kaposi sarcoma (KS) is a malignancy of viral etiology whose course ranges from cutaneous limited lesions to fulminant disease with multi-organ involvement. Four clinical variants of the disease exist: classic, endemic, iatrogenic, and epidemic. Iatrogenic and epidemic variants of Kaposi sarcoma develop in the setting of immune suppression. Transplant recipients who develop iatrogenic KS typically demonstrate improvement of lesions following de-escalation of immunosuppressive therapy. Similarly, HIV-infected patients who begin highly active antiretroviral therapy (HAART) experience immune reconstitution, which can induce KS regression. We describe two patients with varying clinical outcomes of cutaneous-limited HIV-associated KS after immune reconstitution with HAART. We propose that immune reconstitution with HAART, followed by clinical and radiographic surveillance for disease progression, may be an appropriate initial management strategy for limited cutaneous HIV-associated KS. In patients with more extensive disease at presentation or failure of HAART alone, antineoplastic therapy should be instituted.

Cutaneous manifestations of disseminated gonococcemia.

BACKGROUND: Sexually transmitted infections, includingurogenital gonorrheal infection, are a growing healthconcern in the United States. Nearly 50% of cervicalinfections are asymptomatic. If left undiagnosedand untreated, there is a risk of disseminatedinfection. PURPOSE: To describe an 18-year-old womanpresenting with disseminated gonococcal infectionconfirmed by blood cultures, skin biopsy, and urinegonococcal probe. We also describe the presentation,diagnosis, and treatment of disseminated gonococcalinfection, including discussion of the variousmorphologies of cutaneous lesions that have beenreported in the literature. MATERIALS AND METHODS: Thefeatures of a woman with disseminated gonococcalinfection are presented. Using PubMed, the termscutaneous, disseminated, gonococcal, gonorrhea,infection, lesions, manifestations, pustules, skin, andsystemic were searched. Relevant citations wereutilized and discussed. RESULTS: Hemorrhagic pustules,petechiae, and purpuric lesions developed in a youngwoman with fever and joint pain. Blood cultures grewbeta lactamase negative Neisseria gonorrhoeae andthe Neisseria gonorrhoeae/Chlamydia trachomatisprobe was positive for both N. gonorrhoeae and C.trachomatis. Biopsy revealed bulla with neutrophils,extravasated erythrocytes, fibrin deposits in the vesselwalls, and leukocytoclasia. CONCLUSION: Cutaneouslesions of disseminated gonococcal infection caninclude abscesses, cellulitis, petechiae, purpuricmacules, necrotizing fasciitis, and vasculitis. It isimportant for the clinician to recognize the clinicalsigns and symptoms of disseminated gonococcalinfection, particularly the various cutaneousmanifestations.

Tamoxifen-induced radiation recall dermatitis.

BACKGROUND: Radiation recall dermatitis (RRD) canpresent days to years after radiation exposure andis most commonly caused by chemotherapy drugs,with tamoxifen-induced radiation recall dermatitisbeing exceptionally rare. PURPOSE: To report a newcase of tamoxifen-induced radiation recall dermatitisafter 4.5 years of tamoxifen exposure, making this thelongest time of onset to RRD after tamoxifen initiation. MATERIALS AND METHODS: The case of a woman withtamoxifen-induced RRD is presented. Using PubMedand Google Scholar, the terms tamoxifen, radiation,recall, dermatitis were searched. Relevant citationswere utilized and discussed. RESULTS: An adult womanwith history of inflammatory breast carcinomadeveloped an erythematous, scaly, tender plaquelocalized to previously irradiated skin of the left chestafter more than four years of tamoxifen therapy. Thepatient was diagnosed with RRD and was treated withtopical triamcinolone 0.1% cream twice daily to theaffected areas. The patient experienced subsequentrapid improvement despite continuation of tamoxifentreatment. Biopsy revealed changes consistent withradiation dermatitis with no evidence of malignancy. CONCLUSION: Radiation recall dermatitis can havesignificant impact on affected patients and can posea diagnostic dilemma for clinicians who may mistakeRRD for infection or recurrence of malignancy. It isimportant to be familiar with the presenting signs andsymptoms of this entity so that affected patients canreceive timely and appropriate therapy.

Associated conditions in patients with multiple dermatofibromas: Case reports and literature review.

Dermatofibromas are benign, fibrohistiocytic, dermal tumors. Solitary dermatofibromas may be incidental findings, whereas multiple dermatofibromas may be associated with systemic conditions or previous therapies. Two women and one man with multiple dermatofibromas and an associated systemic condition, immunosuppression, or both, are described. Nine dermatofibromas developed in a woman with hypothyroidism, optic neuritis, and Arnold Chiari I malformation. Five dermatofibromas developed in a woman with breast cancer who had received several systemic antineoplastic therapies. Eleven dermatofibromas developed in a man with HIV whose systemic therapies included acyclovir, darunavir/cobicistat, dolutegravir, etravirine, and ritonavir. Conditions associated with multiple dermatofibromas include autoimmune diseases, cancer, chromosomal abnormalities, immunodeficiencies, metabolic disturbances, and altered physiologic states such as pregnancy. Medications received by patients with multiple dermatofibromas included immunosuppressive agents, psoriasis therapies, and antineoplastic drugs. Multiple dermatofibromas can be observed in patients with associated medical conditions, systemic therapies, or both. Therefore, in individuals presenting with multiple dermatofibromas, not only evaluation for associated disorders, but also review of prior and current drug therapies, should be considered.

Upper wide-angle viewing system for ITER.

The Upper Wide Angle Viewing System (UWAVS) will be installed on five upper ports of ITER. This paper shows major requirements, gives an overview of the preliminary design with reasons for some design choices, examines self-emitted IR light from UWAVS optics and its effect on accuracy, and shows calculations of signal-to-noise ratios for the two-color temperature output as a function of integration time and divertor temperature. Accurate temperature output requires correction for vacuum window absorption vs. wavelength and for self-emitted IR, which requires good measurement of the temperature of the optical components. The anticipated signal-to-noise ratio using presently available IR cameras is adequate for the required 500 Hz frame rate.

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.

Multi-energy SXR cameras for magnetically confined fusion plasmas (invited).

A compact multi-energy soft x-ray camera has been developed for time, energy and space-resolved measurements of the soft-x-ray emissivity in magnetically confined fusion plasmas. Multi-energy soft x-ray imaging provides a unique opportunity for measuring, simultaneously, a variety of important plasma properties (Te, nZ, ΔZeff, and ne,fast). The electron temperature can be obtained by modeling the slope of the continuum radiation from ratios of the available brightness and inverted radial emissivity profiles over multiple energy ranges. Impurity density measurements are also possible using the line-emission from medium- to high-Z impurities to separate the background as well as transient levels of metal contributions. This technique should be explored also as a burning plasma diagnostic in-view of its simplicity and robustness.

Real-time radiative divertor feedback control development for the NSTX-U tokamak using a vacuum ultraviolet spectrometer.

A radiative divertor technique is planned for the NSTX-U tokamak to prevent excessive erosion and thermal damage of divertor plasma-facing components in H-mode plasma discharges with auxiliary heating up to 12 MW. In the radiative (partially detached) divertor, extrinsically seeded deuterium or impurity gases are used to increase plasma volumetric power and momentum losses. A real-time feedback control of the gas seeding rate is planned for discharges of up to 5 s duration. The outer divertor leg plasma electron temperature Te estimated spectroscopically in real time will be used as a control parameter. A vacuum ultraviolet spectrometer McPherson Model 251 with a fast charged-coupled device detector is developed for temperature monitoring between 5 and 30 eV, based on the Δn = 0, 1 line intensity ratios of carbon, nitrogen, or neon ion lines in the spectral range 300-1600 Å. A collisional-radiative model-based line intensity ratio will be used for relative calibration. A real-time Te-dependent signal within a characteristic divertor detachment equilibration time of ∼10-15 ms is expected.