Identifying divertor detachment using a machine learning model trained on divertor camera images from DIII-D.

This paper describes the application of a machine learning (ML) algorithm using a convolution neural network, first developed in Boyer et al. ["Classification and prediction of detachment in DIII-D using neural networks trained on C III imaging," Nucl. Fusion (submitted) (2024)], to detect divertor detachment in DIII-D. Detachment detection is based on images from tangentially viewing upper and lower filtered divertor cameras that measure CIII emission at 465 nm. Separate ML models are developed for lower single null and upper single null configurations with mostly closed divertor shapes. Due to the viewing angle and divertor geometry, camera images of the upper divertor show a stark contrast in CIII emission between attached and detached conditions and the model identified detachment with 100% accuracy in the test dataset. For the lower divertor images, the contrast between attached and detached conditions is lower and the model identifies detachment with 96% accuracy. This ML model will be applied to the image data after each shot to provide a rapid assessment of divertor detachment to aid operation of DIII-D with the potential extension to other devices in the future.

A high-density and high-confinement tokamak plasma regime for fusion energy.

The tokamak approach, utilizing a toroidal magnetic field configuration to confine a hot plasma, is one of the most promising designs for developing reactors that can exploit nuclear fusion to generate electrical energy1,2. To reach the goal of an economical reactor, most tokamak reactor designs3-10 simultaneously require reaching a plasma line-averaged density above an empirical limit-the so-called Greenwald density11-and attaining an energy confinement quality better than the standard high-confinement mode12,13. However, such an operating regime has never been verified in experiments. In addition, a long-standing challenge in the high-confinement mode has been the compatibility between a high-performance core and avoiding large, transient edge perturbations that can cause very high heat loads on the plasma-facing-components in tokamaks. Here we report the demonstration of stable tokamak plasmas with a line-averaged density approximately 20% above the Greenwald density and an energy confinement quality of approximately 50% better than the standard high-confinement mode, which was realized by taking advantage of the enhanced suppression of turbulent transport granted by high density-gradients in the high-poloidal-beta scenario14,15. Furthermore, our experimental results show an integration of very low edge transient perturbations with the high normalized density and confinement core. The operating regime we report supports some critical requirements in many fusion reactor designs all over the world and opens a potential avenue to an operating point for producing economically attractive fusion energy.

Spectrally resolved polarization angle across the motional Stark effect spectrum.

A new diagnostic technique has been developed that couples a spectrometer and an image-intensified camera into the traditional motional Stark effect (MSE) system on DIII-D. The image-intensified camera syncs with the photo-elastic modulators to spectrally resolve the Stokes parameters across the Stark multiplet. Polarization dependent phase shift, likely from a plasma facing mirror, leads to the spectropolarimeter measuring a variation in the polarization angle across the MSE spectrum of ∼8°.

Improved motional Stark effect signal processing using fast Fourier transform spectral analysis.

A Fast Fourier Transform (FFT) based method has been developed, which improves the frequency response of the Motional Stark Effect (MSE) system by about a factor of 10 over the conventional analog lock-in method. The method uses fits to rigorously derived analytic expressions for the FFT spectral components of the MSE signal to accurately obtain the amplitudes and phases of the 2f1 and 2f2 photo-elastic modulator (PEM) frequencies that encode the polarization angle. Since no frequency filtering is used in the FFT method, the frequency response is limited by fundamental measurement properties: the frequency response of the detector, photon statistics, sample rate, and the ability to resolve the spectral components. In contrast, the frequency response of the analog lock-in is limited by a low pass filter with a cutoff of around 500 Hz. In the case of the DIII-D MSE system, the output of the photo-multiplier tube detector was sampled at 500 kHz and FFTs with as few as 100 points were used to obtain the amplitudes of the 2f1 and 2f2 PEM frequency components. This corresponds to a frequency response of 5 kHz, about ten times faster than the analog lock-in amplifier system. Details of the FFT method will be presented and compared to those of the analog lock-in system.

Self-report of psychological symptoms in hypoparathyroidism patients on conventional therapy.

OBJECTIVE: Hypoparathyroidism is characterized by parathyroid hormone deficiency and hypocalcemia. It has been demonstrated that these patients may also present psychiatric symptoms and decrease of quality of life. The aims of this study were to evaluate the presence of psychopathological symptoms in a cohort of patients with hypoparathyroidism and compare to a control group. SUBJECTS AND METHODS: Patients were submitted to a cross-sectional Symptom Checklist-90-R (SCL-90-R) questionnaire that evaluates psychopathological symptoms by means of the Global Severity Index (GSI), Positive Symptoms Total (PST) and Positive Symptom Distress Index (PSDI). A score based in the positive symptoms was calculated (T-score). The test group was composed of patients with hypoparathyroidism, and control by thyroidectomized patients without hypoparathyroidism. A correlation between the presence of psychological symptoms and clinical features was analyzed. RESULTS: The study included 57 patients with a mean age of 51.1 ± 16.4 years; 20 as a control and 37, test group. There were no differences between groups regarding gender, mean age and age at diagnose. Hypoparathyroidism patients presented higher GSI index than the control group (p = 0.038). Mean T-score of the test group was as elevated as 58.2 ± 5.3 (reference range < 55). No correlation of the number of psychological symptoms to clinical and laboratorial parameters was observed. CONCLUSION: Patients with hypoparathyroidism attending our outpatient clinics presented an increase in the number of self-report of psychological symptoms when compared with a control group. However, no correlation with hypocalcemia and clinical parameters was observed. Future studies are necessary to evaluated if the absence of PTH play a role on it.

Self-report of psychological symptoms in hypoparathyroidism patients on conventional therapy

ABSTRACT Objective: Hypoparathyroidism is characterized by parathyroid hormone deficiency and hypocalcemia. It has been demonstrated that these patients may also present psychiatric symptoms and decrease of quality of life. The aims of this study were to evaluate the presence of psychopathological symptoms in a cohort of patients with hypoparathyroidism and compare to a control group. Subjects and methods: Patients were submitted to a cross-sectional Symptom Checklist-90-R (SCL-90-R) questionnaire that evaluates psychopathological symptoms by means of the Global Severity Index (GSI), Positive Symptoms Total (PST) and Positive Symptom Distress Index (PSDI). A score based in the positive symptoms was calculated (T-score). The test group was composed of patients with hypoparathyroidism, and control by thyroidectomized patients without hypoparathyroidism. A correlation between the presence of psychological symptoms and clinical features was analyzed. Results: The study included 57 patients with a mean age of 51.1 ± 16.4 years; 20 as a control and 37, test group. There were no differences between groups regarding gender, mean age and age at diagnose. Hypoparathyroidism patients presented higher GSI index than the control group (p = 0.038). Mean T-score of the test group was as elevated as 58.2 ± 5.3 (reference range < 55). No correlation of the number of psychological symptoms to clinical and laboratorial parameters was observed. Conclusion: Patients with hypoparathyroidism attending our outpatient clinics presented an increase in the number of self-report of psychological symptoms when compared with a control group. However, no correlation with hypocalcemia and clinical parameters was observed. Future studies are necessary to evaluated if the absence of PTH play a role on it.

Core tungsten radiation diagnostic calibration by small shell pellet injection in the DIII-D tokamak.

Injection of small (outer diameter = 0.8 mm) plastic pellets carrying embedded smaller (10 µg) tungsten grains is used to check calibrations of core tungsten line radiation diagnostics in support of the 2016 tungsten ring campaign in the DIII-D tokamak. Observed total brightness (1 eV-10 keV) and soft x-ray (1 keV-10 keV) brightness are found to be reasonably well (

Asymmetries in the motional Stark effect emission on the DIII-D tokamak.

Spectrometer measurements and filter upgrades to a motional Stark effect polarimeter measuring the outer half-radius of the DIII-D tokamak helped to identify asymmetries in the polarization angle of Stark-split emission. The measured polarization angle of the π components differs and is not orthogonal to the σ component. These differences persist over a range of densities and with low levels of background light. It is suggested that the difference in the polarization angle between components is from a change in the ellipticity of the emitted light across the Stark components coupled with imperfect polarization preservation from an in-vessel mirror.

Evidence for separatrix formation and sustainment with steady inductive helicity injection.

The first sustainment of toroidal plasma current of 50 kA at up to 3 times the injected currents, added in quadrature, using steady inductive helicity injection is described. Separatrix currents-currents not linking the helicity injectors-are sustained up to 40 kA. Decreases in the n=1 toroidal mode of the poloidal magnetic field at higher current amplifications indicate more quiescent, direct toroidal current drive. Results are achieved in HIT-SI (with a spheromak of major radius 0.3 m) during deuterium operations immediately after helium operation. These results represent a breakthrough in the development of this new current drive method for magnetic confinement fusion.

Depression, antidepressants, and sexual function.

AIDS: Recent studies have suggested that serotonin reuptake inhibitors (SSRI's), prescribed for the relief of depression, can cause sexual dysfunction in up to fifty percent of those taking them. The SSRI's--including fluoxetine (Prozac), sertraline (Zoloft), and paroxetine (Paxil)--affect mood stabilization by promoting the transmission of the neurotransmitter serotonin, although enhancing serotonergic function can decrease libido or lead to erectile difficulties. As an alternative to lowering antidepressant dosages and risking losing therapeutic gains, administering serotonin-blockers, such as cyproheptadine (Periactin) and yohimbine (Yocon), has been shown to restore sexual function. However, the serotonin antagonist, cyproheptadine, causes sedation and can reverse the antidepressant or anti-obsessive effect of the SSRI. Yohimbine enhances transmission of the neurotransmitter epinephrine, increasing the flow of blood to erectile tissue and stimulating sexual desire by activating the cerebral cortex. Its drawbacks are increased levels of panic attacks and higher required dosages. Other potential biochemical stratagems are: amantadine (Symmetrel), bromcriptine (Parlodel), and buspirone (Buspar), which enhance dopamine and serotonin transmission; and bethanecol (Urechline), which enhances choline transmission. One study indicates improved sexual response when the nonserotonergic, mildly dopamine-enhancing buproprion (Welbutrin) is substituted for fluoxetine.^ieng

Use of clonazepam in mania and schizoaffective disorders.

The authors report three cases in which clonazepam controlled the acute symptoms in one manic and two schizoaffective patients. Clonazepam treatment led to a decrease in agitation and logorrhea, without the side effects associated with neuroleptics.

Somatic manifestations of caffeinism.

Caffeine affects most physiological systems. Few studies, however, have attempted to document which somatic symptoms are commonly associated with caffeinism. To answer this question, the authors evaluated 124 general hospital patients, and compared reported somatic symptoms among low, moderate and high caffeine users. Diuresis, insomnia, withdrawal headache, diarrhea, anxiety, tachycardia and tremulousness were most commonly reported, in descending order of frequency. Differences among high, moderate and low users were common, and some dose-response associations were apparent. Most symptoms were explainable by caffeine's known CNS neuropharmacological effects or peripheral pharmacological actions.