Integrated plasma facing component calorimetry for measurement of shot integrated deposited energy in the NSTX-U.

The upgrade to the National Spherical Torus eXperiment (NSTX-U) [J. Menard et al., Nucl. Fusion 52, 083015 (2012)] increases the injected neutral beam power up to 12 MW and the plasma current up to Ip = 2 MA for plasma durations up to 5 s. The graphite plasma facing components have been re-designed to handle greater heat and energy fluxes than were seen in NSTX using a castellated design. We present the experimental testing and validation of a castellated graphite target, similar to the prototype tile design, instrumented with thermocouples at various depths in the castellation. During testing, incident heat flux is provided by a programmed electron beam system and surface temperatures are measured via infrared thermography directly viewing the target surface. It was found that the thermocouple response scaled linearly with the measured surface temperature rise regardless of thermocouple depth in the castellation. A sensitivity of 14.3 °C/kJ of deposited energy was found when treating individual castellations as a semi-infinite solid.

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.

Design and characterization of a prototype divertor viewing infrared video bolometer for NSTX-U.

The InfraRed Video Bolometer (IRVB) is a powerful tool to measure radiated power in magnetically confined plasmas due to its ability to obtain 2D images of plasma emission using a technique that is compatible with the fusion nuclear environment. A prototype IRVB has been developed and installed on NSTX-U to view the lower divertor. The IRVB is a pinhole camera which images radiation from the plasma onto a 2.5 µm thick, 9 × 7 cm2 Pt foil and monitors the resulting spatio-temporal temperature evolution using an IR camera. The power flux incident on the foil is calculated by solving the 2D+time heat diffusion equation, using the foil's calibrated thermal properties. An optimized, high frame rate IRVB, is quantitatively compared to results from a resistive bolometer on the bench using a modulated 405 nm laser beam with variable power density and square wave modulation from 0.2 Hz to 250 Hz. The design of the NSTX-U system and benchtop characterization are presented where signal-to-noise ratios are assessed using three different IR cameras: FLIR A655sc, FLIR A6751sc, and SBF-161. The sensitivity of the IRVB equipped with the SBF-161 camera is found to be high enough to measure radiation features in the NSTX-U lower divertor as estimated using SOLPS modeling. The optimized IRVB has a frame rate up to 50 Hz, high enough to distinguish radiation during edge-localized-modes (ELMs) from that between ELMs.

Preliminary design of a tangentially viewing imaging bolometer for NSTX-U.

The infrared imaging video bolometer (IRVB) measures plasma radiated power images using a thin metal foil. Two different designs with a tangential view of NSTX-U are made assuming a 640 × 480 (1280 × 1024) pixel, 30 (105) fps, 50 (20) mK, IR camera imaging the 9 cm × 9 cm × 2 µm Pt foil. The foil is divided into 40 × 40 (64 × 64) IRVB channels. This gives a spatial resolution of 3.4 (2.2) cm on the machine mid-plane. The noise equivalent power density of the IRVB is given as 113 (46) µW/cm2 for a time resolution of 33 (20) ms. Synthetic images derived from Scrape Off Layer Plasma Simulation data using the IRVB geometry show peak signal levels ranging from ∼0.8 to ∼80 (∼0.36 to ∼26) mW/cm2.

2D divertor heat flux distribution using a 3D heat conduction solver in National Spherical Torus Experiment.

The divertor heat flux footprint in tokamaks is often observed to be non-axisymmetric due to intrinsic error fields, applied 3D magnetic fields or during transients such as edge localized modes. Typically, only 1D radial heat flux profiles are analyzed; however, analysis of the full 2D divertor measurements provides opportunities to study the asymmetric nature of the deposited heat flux. To accomplish this an improved 3D Fourier analysis method has been successfully applied in a heat conduction solver (TACO) to determine the 2D heat flux distribution at the lower divertor surface in the National Spherical Torus Experiment (NSTX) tokamak. This advance enables study of helical heat deposition onto the divertor. In order to account for heat transmission through poorly adhered surface layers on the divertor plate, a heat transmission coefficient, defined as the surface layer thermal conductivity divided by the thickness of the layer, was introduced to the solution of heat conduction equation. This coefficient is denoted as α and a range of values were tested in the model to ensure a reliable heat flux calculation until a specific value of α led to the constant total deposited energy in the numerical solution after the end of discharge. A comparison between 1D heat flux profiles from TACO and from a 2D heat flux calculation code, THEODOR, shows good agreement. Advantages of 2D heat flux distribution over the conventional 1D heat flux profile are also discussed, and examples of 2D data analysis in the study of striated heat deposition pattern as well as the toroidal degree of asymmetry of peak heat flux and heat flux width are demonstrated.

Spectral emission measurements of lithium on the lithium tokamak experiment.

There has been a long-standing collaboration between ORNL and PPPL on edge and boundary layer physics. As part of this collaboration, ORNL has a large role in the instrumentation and interpretation of edge physics in the lithium tokamak experiment (LTX). In particular, a charge exchange recombination spectroscopy (CHERS) diagnostic is being designed and undergoing staged testing on LTX. Here we present results of passively measured lithium emission at 5166.89 A in LTX in anticipation of active spectroscopy measurements, which will be enabled by the installation of a neutral beam in 2013. Preliminary measurements are made in transient LTX plasmas with plasma current, I(p) < 70 kA, ohmic heating power, P(oh) ∼ 0.3 MW and discharge lifetimes of 10-15 ms. Measurements are made with a short focal length spectrometer and optics similar to the CHERS diagnostics on NSTX [R. E. Bell, Rev. Sci. Instrum. 68(2), 1273-1280 (1997)]. These preliminary measurements suggest that even without the neutral beam for active spectroscopy, there is sufficient passive lithium emission to allow for line-of-sight profile measurements of ion temperature, T(i); toroidal velocity and v(t). Results show peak T(i) = 70 eV and peak v(t) = 45 km/s were reached 10 ms into the discharge.

High-harmonic fast-wave power flow along magnetic field lines in the scrape-off layer of NSTX.

A significant fraction of high-harmonic fast-wave (HHFW) power applied to NSTX can be lost to the scrape-off layer (SOL) and deposited in bright and hot spirals on the divertor rather than in the core plasma. We show that the HHFW power flows to these spirals along magnetic field lines passing through the SOL in front of the antenna, implying that the HHFW power couples across the entire width of the SOL rather than mostly at the antenna face. This result will help guide future efforts to understand and minimize these edge losses in order to maximize fast-wave heating and current drive.

A dual-band adaptor for infrared imaging.

A novel imaging adaptor providing the capability to extend a standard single-band infrared (IR) camera into a two-color or dual-band device has been developed for application to high-speed IR thermography on the National Spherical Tokamak Experiment (NSTX). Temperature measurement with two-band infrared imaging has the advantage of being mostly independent of surface emissivity, which may vary significantly in the liquid lithium divertor installed on NSTX as compared to that of an all-carbon first wall. In order to take advantage of the high-speed capability of the existing IR camera at NSTX (1.6-6.2 kHz frame rate), a commercial visible-range optical splitter was extensively modified to operate in the medium wavelength and long wavelength IR. This two-band IR adapter utilizes a dichroic beamsplitter, which reflects 4-6 µm wavelengths and transmits 7-10 µm wavelength radiation, each with >95% efficiency and projects each IR channel image side-by-side on the camera's detector. Cutoff filters are used in each IR channel, and ZnSe imaging optics and mirrors optimized for broadband IR use are incorporated into the design. In-situ and ex-situ temperature calibration and preliminary data of the NSTX divertor during plasma discharges are presented, with contrasting results for dual-band vs. single-band IR operation.

Continuous improvement of H-mode discharge performance with progressively increasing lithium coatings in the National Spherical Torus Experiment.

Lithium wall coatings have been shown to reduce recycling, improve energy confinement, and suppress edge localized modes in the National Spherical Torus Experiment. Here, we show that these effects depend continuously on the amount of predischarge lithium evaporation. We observed a nearly monotonic reduction in recycling, decrease in electron transport, and modification of the edge profiles and stability with increasing lithium. These correlations challenge basic expectations, given that even the smallest coatings exceeded that needed for a nominal thickness of the order of the implantation range.

High density Langmuir probe array for NSTX scrape-off layer measurements under lithiated divertor conditions.

A high density Langmuir probe array has been developed for measurements of scrape-off layer parameters in NSTX. Relevant scale lengths for heat and particle fluxes are 1-5 cm. Transient edge plasma events can occur on a time scale of several milliseconds, and the duration of a typical plasma discharge is ∼1 s. The array consists of 99 individual electrodes arranged in three parallel radial rows to allow both swept and triple-probe operation and is mounted in a carbon tile located in the lower outer divertor of NSTX between two segments of the newly installed liquid lithium divertor. Initial swept probe results tracking the outer strike point through probe flux measurements are presented.

Thermoelectric magnetohydrodynamic stirring of liquid metals.

The direct observation of a thermoelectric magnetohydrodynamic (TEMHD) flow has been achieved and is reported here. The origin of the flow is identified based on a series of qualitative tests and corresponds, quantitatively, with a swirling flow TEMHD model. A theory for determining the dominant driver of a free-surface flow, TEMHD or thermocapillary (TC), is found to be consistent with the experimental results. The use of the analytical form for an open geometry develops a new dimensionless parameter describing the ratio of TEMHD to TC generated flows.

AMPA-receptor blockade within the RVLM modulates cardiovascular responses via glutamate during peripheral stimuli.

We investigated the effects of AMPA-receptor blockade in the rostral ventrolateral medulla (RVLM) on cardiovascular responses and extracellular concentrations of glutamate during two different types of stimuli that activate peripheral Adelta - and C-fiber polymodal nociceptors using anesthetized rats. First, mechanical stimulation was achieved by applying a bilateral hindpaw pinch for 5 s, and second, thermal stimulation was evoked by immersing bilaterally the hindpaw metatarsi in a 52 degrees C hot water bath for 4 s. Mechanical stimulation increased mean arterial pressure (MAP) by 23 +/- 1 mmHg and heart rate (HR) by 25 +/- 3 bpm (n= 8). Thermal stimuli increased MAP by 32 +/- 3 mmHg and HR by 27 +/- 4 bpm (n= 8). After controlled generation of mechanical or thermal stimulation, 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; 1.0 microM) was microdialysed bilaterally into the RVLM for 30 min. Administration of CNQX attenuated MAP and HR responses during a subsequent mechanical but not during thermal stimulation. Analyses of extracellular concentrations of glutamate within the RVLM bilaterally revealed an increase of this neurotransmitter within the RVLM during mechanical noxious stimulation. Concomitant with attenuation of the cardiovascular responses, glutamate concentrations were also decreased during the mechanical stimulation after administration of CNQX. These results demonstrate that the AMPA-receptor blockade within the RVLM that attenuates cardiovascular responses during mechanical stimulation is associated with a reduction in extracellular levels of glutamate. In addition, it appears that AMPA receptors in the RVLM do not play a role in mediating cardiovascular responses during thermal stimulation.

Correlation between low levels of estrogen receptors and estrogen responsiveness in two rat osteoblast-like cell lines.

With the knowledge that estrogen replacement therapy can circumvent postmenopausal osteoporosis and with the discovery of estrogen receptors (ER) in cultures of normal osteoblast-like cells, extensive investigations have been directed toward understanding the role of the ER in normal bone homeostasis. ROS 17/2.8 and UMR-106-01, two established osteoblast-like cell lines derived from rat osteosarcomas, have been shown to have estrogen-regulated biologic responses. Only the ROS 17/2.8 cell line has been reported to contain ER. In this study, high-affinity, saturable binding sites characteristic of the ER were detected in UMR-106-01 cells by binding assays with the high-affinity ligand, [125I]17 beta-estradiol. An initial immunoconcentration step before western blot analysis also allowed detection of the full-length ER protein. In addition, northern blot analysis indicated that the entire ER transcript was expressed and that the half-life of the ER message was increased following cycloheximide treatment. Message levels were also regulated by removal of serum and treatment with estradiol. An estrogen-regulated reporter vector, ERET81CAT, was transfected into the UMR-106-01 cells to determine whether the detected level of ER was transcriptionally functional. Using this assay, estrogen responsiveness was evident; however, the response was inconsistent. Multiple factors, such as serum, estradiol, and cell density, influence the ER levels in these cells and probably cause fluctuations in the abundance of receptors available to induce the CAT response. When the cells are responsive, the ICI 164,384 antagonist could block the estrogen-induced activation of CAT.(ABSTRACT TRUNCATED AT 250 WORDS)

Estrogens modulate the responsiveness of osteoblast-like cells (ROS 17/2.8) stably transfected with estrogen receptor.

Recent studies have demonstrated the presence of estrogen receptor (ER) in both normal human osteoblast-like and osteoblast-like osteosarcoma cells. The number of ER in cultured osteoblastic cells is very low (200-500 sites/cell). This has complicated characterization of the biological role of estrogens in bone cells. To study the responsiveness of bone cells to estrogens, we established osteoblast-like cell lines expressing higher ER levels. ROS 17/2.8, an osteoblastic cell line, was stably transfected with the cDNA encoding for the mouse ER. After a selection period, positive clones were isolated and evaluated for the presence of ER by both Northern blot analysis and ligand binding assays. Using these techniques, we detected a significant increase in the level of both ER transcript and binding compared to that in wild-type cells. The levels of expressed ER protein were similar to those reported in normal human osteoblast-like cells in primary culture (approximately 2000 sites/cell). To test whether the exogenously inserted ER was responsive, both wild-type and ER stably transfected cells were transiently transfected with a reporter construct containing an estrogen-responsive element linked to a truncated thymidine kinase promoter and a chloramphenicol acetyltransferase (CAT) reporter gene. Exposure of the cells to increased concentrations of estradiol induced a slight increase in CAT activity in wild-type cells (approximately 1.5-fold) at maximal stimulation; however, it provoked a clear concentration-dependent increase in CAT activity in the ER stably transfected cells, with a maximal stimulation of approximately 10-fold. This event was receptor mediated, since ICI 164,384, an ER antagonist, blocked the enhancement of estradiol-induced CAT activity, and it was specific, since other steroid hormones did not stimulate CAT activity. Finally, we evaluated the ability of ER to modulate an endogenous estrogen-responsive gene by measuring the activity of the enzyme alkaline phosphatase. In addition, diethylstilbestrol, a synthetic estrogen agonist, increased the activity of both the CAT reporter gene and the endogenous alkaline phosphatase enzyme. In summary, we have established osteoblast-like cells expressing high levels of an exogenously inserted ER, which has characteristics similar to those of the endogenous ER in terms of its Kd. Finally, the exogenous ER regulates both exogenously inserted construct (VITERECAT) and endogenous properties of the cells (enzymatic activity and proliferation).

Biochemical effects of 17 beta-estradiol on UMR106 cells.

The effect of 17 beta-estradiol (E) on an osteoblast-like cell line, UMR106, was studied in vitro. The concentrations of transferrin and seven enzymes (gamma glutamyl transferase, alkaline phosphatase, acid phosphatase, lactate dehydrogenase, creatine kinase, alanine aminotransferase and aspartate aminotransferase) were measured in these cells after incubation in culture medium containing either E or the vehicle. E treatment increased five of the seven enzymes and increased the transferrin concentration in the UMR106 cells while simultaneously reducing the proliferation rates. 4-Hydroxytamoxifen, an estrogen antagonist, produced a mild estrogen agonist action on growth rates and enzyme concentrations in the UMR106 cells. When E was present simultaneously, the agonist properties of 4-hydroxytamoxifen were enhanced. These studies show that E enhanced activity of five enzymes and the transferrin content of UMR106 cells after a 2-day incubation. 4-Hydroxytamoxifen enhanced the E effect, illustrating that estrogen antagonists may manifest agonist or antagonist properties depending on the model. These results extend our previous observations showing a direct effect of E in vitro on osteoblast-like cells.

Estradiol stimulates in vitro the secretion of insulin-like growth factors by the clonal osteoblastic cell line, UMR106.

UMR106 cells, a rat osteosarcoma derived clonal line, secreted insulin-like growth factors (IGF) in vitro. The IGF-II levels corrected for the cell numbers were 7-8 times higher than the IGF-I levels in the medium. Both growth factors were higher by 4-5 fold in medium conditioned by rapidly growing cells than in medium conditioned by confluent cells. The addition of 17-beta-estradiol (E) to the culture medium was associated with a statistically significant increase in the IGF concentrations. This increment was metabolite specific, not occurring with 17-alpha-E, the inactive epimer of E. 1,25(OH)2D3 also increased the IGF-I concentration but prior treatment with E blocked the response to 1,25(OH)2D3, demonstrating antagonistic actions of these two hormones on IGF secretion by osteoblast-like cells.

Transforming growth factor beta mediates the estrogen induced inhibition of UMR106 cell growth.

A mitogenic response to transforming growth factor beta (TGF) occurred in the UMR106 cells cultured in serum-free medium and exposed serially to estradiol and TGF. This mitogenic response was lost when insulin was removed from the medium. TGF inhibited growth and increased the alkaline phosphatase content in the UMR106 cells cultured in medium lacking insulin. Prior exposure of the cells to estradiol enhanced this response. Monoclonal antibodies against TGF blocked the estradiol induced inhibition of growth after a two day incubation in medium devoid of insulin.

Estrogens and the skeleton: cellular and molecular mechanisms.

Postmenopausal women lose bone mineral density and this loss can be prevented by estrogen administration. Although the skeletal effects of estrogens have been regarded previously as indirect, estrogen receptors have been discovered in cultured human osteoblasts and related cell lines. The UMR106 cell line derived from a rat osteogenic osteosarcoma is such an osteoblast model. We have shown direct effects of estradiol (E) on these cells in vitro, inhibiting growth and stimulating alkaline phosphatase activity (AP) corrected for cell number. This response was maximal at E conc. of 10(-10) M in serum and Phenol Red free medium, was metabolite specific and cell cycle-dependent. These cells contain high affinity binding sites with a Kd of 0.5 nM. Estrogen receptors were detected by the monoclonal antibody H-222 on Western blot after initial immunoprecipitation to concentrate the proteins. E treatment increased several enzymes including creatine kinase and LDH isoenzymes along with increments in intracellular transferrin. Transforming growth factor-beta is secreted by these cells. Secretion of this peptide was stimulated by E. TGF-beta mediated the transient growth inhibition associated with E treatment. Insulin like growth factors (IGF) are also secreted by these cells with IGF-II concentrations in the culture medium being eight times higher than IGF-I levels. E treatment increased the concentrations of both IGFs in the culture medium after a 3 day incubation. Exposure of E treated cells manifested a mitogenic response and reduced AP, indicating that E induced receptors for IGFs. These findings establish direct effects of E on osteoblastic cells in vitro and demonstrate responses to E at many levels. These osteoblast responses in vitro suggest an important role for sex steroids in the development and function of the osteoblast lineage.

Ring hydroxylation of 25-hydroxycholecalciferol by rat renal microsomes.

Two metabolites have been isolated from rat renal microsomes incubated with 25-hydroxycholecalciferol. Postmitochondrial supernatant fractions from kidneys of thyroidectomized and parathyroidectomized rats were incubated with magnesium acetate, potassium acetate, an NADPH generating system, and 25-hydroxycholecalciferol at a level of 20 micrograms/ml postmitochondrial supernatant for 60 min at 30 degrees C. Lipid extracts of the incubation mixtures were purified by silica gel TLC and HPLC. Two peaks were obtained. Metabolite chi 2 eluted at 18 min and metabolite chi 1 at 23 min when chromatographed on a silica column developed with hexane-isopropanol. Metabolites chi 1 and chi 2 were found to have maximal absorbance at 265 nm. Both metabolites were periodate sensitive, indicating vicinal hydroxyl groups. Mass spectral analysis of metabolite chi 2, which was isolated in greater quantity than metabolite chi 1, indicates that metabolite chi 2 had resulted from hydroxylation of the A ring. Results indicate that 25-hydroxycholecalciferol is hydroxylated on carbon 2 or carbon 4 by renal microsomes. Metabolites chi 1 and chi 2, because of similarity in chromatographic migration and periodate sensitivity, are, perhaps, isomers or 2- and 4-hydroxylated metabolites.