Non-inductive plasma vertical position measurement for the 1056 s discharge on EAST.

Vertical position stability plays a crucial role in maintaining safe and reliable plasma operation for long-pulse fusion devices. In general, the vertical position is measured by using inductive magnetic coils installed inside the vacuum vessel; however, the integration drift effects are inherent for steady-state or long-pulse plasma operation. Developing a non-magnetic approach provides a fusion reactor-relevant steady-state solution that avoids the negative impact of integration drift. In this paper, we compare the non-inductively determined vertical position achieved by line-integrated interferometer and polarimeter measurements to that employing an inductive flux loop for a 1056 s discharge recently achieved on EAST (Experimental Advanced Superconducting Tokamak). Experimental results show that the non-inductive measurement is more robust than flux loops after 300 s if the integrator is not reset to suppress integrator drift. Real-time vertical position control using the non-inductive system is proposed for the next EAST experimental campaign.

Development of Faraday rotation measurements on Keda Reconnection eXperiment (KRX) device.

The Faraday-effect based polarimeter and interferometer are developed for non-perturbation magnetic field and density measurements on the Keda Reconnection eXperiment (KRX) device. The magnetic reconnection is externally driven by a pair of parallel current plates. To design this instrument and provide an alternative way to facilitate theory-experiment comparisons via forward modeling of the diagnostics process with full plasma dynamics given by simulation, we develop a synthetic diagnostics based on 2D photonic integrated circuit simulation for magnetic reconnection on the KRX. The view-line geometry is optimized and wavelengths (1 mm) of the polarimeter and interferometer are selected to ensure the sensitivity of measurement on the KRX. We have simulated magnetic reconnection on the x-line (x-z plane) with horizontal viewing and vertical viewing for line of sight measurements. It is found that the current sheet width and indicator of magnetic reconnection can be inferred directly from the dynamics of Faraday rotation even with the line-integrated character of polarimeter-interferometer diagnostics.

Novel peptidic dual GLP-1/glucagon receptor agonist alleviates diabetes and diabetic complications in combination with low-intensity ultrasound.

OBJECTIVE: To design and evaluate a novel oxyntomodulin (OXM) derivative with albumin-binding helix domain and dual GLP-1 receptor (GLP-1R) and glucagon receptor (GcgR) activation activity to achieve metabolize improvement on the diabetes-related complication. MATERIALS AND METHODS: Mutation (D-Ser2) on OXM was performed and then different helix albumin-binding domains were fused to the mutated OXM via a thrombin-cleavable linker to generate seven fusion peptides, named LM01-LM07. Seven LM peptides were synthesized and screened via in vitro receptor activation test, albumin binding measurement and protease cleavage assay to select potent candidate peptide for further in vivo study. Moreover, acute and chronic efficacy studies were conducted to evaluate the efficacy of selected candidate using db/db mice. RESULTS: LM06, as selected OXM derivative, exhibited higher albumin-binding affinity, sustained-release efficiency and balanced activation activities on both GLP-1R and GcgR compared with other ones. Moreover, LM06 was demonstrated with improved hypoglycemic and insulinotropic abilities in receptor-deficient mice via activating GLP-1R. In addition, prolonged anti-diabetic efficacies of LM06 were demonstrated via hypoglycemic duration assay and OGTT in db/db mice. Further pharmacokinetic test of LM06 in both rats and monkeys identified improved half-life and other metabolic characteristics. Nevertheless, 8-week subcutaneously dosed LM06 in db/db mice achieved prominent efficacies on glucostasis, weight-lowering, pancreatic function and adipogenesis via activating GLP-1R and GcgR. Moreover, LM06 also could accelerate diabetic skin wound closure in combination with low-intensity ultrasound. CONCLUSIONS: LM06, as a long-acting dual GLP-1R/GcgR agonist, exerts potential as a once-weekly therapeutic candidate against diabetes-related complication in combination with low-intensity ultrasound.

Error correction associated with stray light for Faraday-effect polarimetry system on EAST.

The polarimeter-interferometer system with 11 double-pass radial-view measurement chords has the ability to provide electron density and plasma current profiles, making it exceptionally useful in daily operation on the Experiment Advanced Superconducting Tokamak. However, due to limited optical access and intrinsic feedback, the stray lights arising from spurious reflections along the optical path (unwanted reflections from various optical components/mounts and transmissive optical elements such as windows, waveplates, and lenses as well as the detectors) distort the Faraday rotation measurements. Furthermore, the feedback light from the retro-reflector which is used to realize the double-pass configuration makes it even worse. A data processing approach to decrease the stray light influence is reported in this paper. Based on the theoretical model developed, the Faraday rotation angle is extracted by subtracting the deviation term which can be calculated with a simplified model. With this approach, the Faraday rotation oscillation during density ramp-up can be reduced from 2°-5° to 0.5°-1.5°, which reduces the Faraday rotation measurement errors significantly.

[Adiponectin ameliorated pancreatic islet mitochondrial injury induced by chronic intermittent hypoxia].

Objective: To explore the effect of adiponectin (APN) on islet injury induced by chronic intermittent hypoxia (CIH). Methods: Thirty-six SD rats were randomly divided into three groups: Normal control (NC), CIH, and CIH + APN groups. The rats in the CIH and CIH+APN groups received an intermittent hypoxia exposure while the rats in NC group received the room air only. The rats in CIH+APN group received the intravenous injection of APN. The intermittent hypoxia events persisted 8 hours a day and last for 35 days. The fasting blood glucose and fasting insulin were detected at the time of 0, 7, 14, 21, 28, and 35 day. After 35 days, the level of serum adiponectin, and adenosine triphosphate (ATP) level, superoxide dismutase (SOD), malondialdehyde (MDA), the mRNA levels of mitochondrial oxidative phosphorylation function and mitochondrial synthesis gene, and the protein level of mitochondrial and cytoplasmic cytochrome C of pancreatic islet were detected. Results: The glucose and insulin level had no statistically differences among three groups at different time points (all P>0.05). However, compared with NC and CIH+APN groups, CIH reduced the serum adiponectin [(7 265±2 209) ng/ml, (6 536±1 678) ng/ml vs (4 923±1 742) ng/ml, both P<0.05], ATP levels [(30.92±1.12) nmol/mg, (26.55±0.72) nmol/mg vs (20.22±1.47) nmol/mg, both P<0.05], mRNA levels of mitochondria oxidative phosphorylation function and mitochondrial synthesis gene, the activity of SOD, and the rate of mitochondrial/cytoplasmic cytochrome C protein level while increased the MDA level in pancreatic islet. Compared with NC group, the MDA level increased (P<0.05) and the APN level had no statistically difference, while the level of other indicators decreased in CIH+APN group (all P<0.05). Conclusion: APN ameliorates the pancreatic islet injury induced by CIH through inhibition of oxidative stress.

Five-channel tunable W-band Doppler backscattering system in the experimental advanced superconducting tokamak.

A 5-channel Doppler backscattering system has been designed and installed in the Experimental Advanced Superconducting Tokamak (EAST). Through an I/Q-type double sideband modulator and a frequency multiplier, an array of finely spaced (Δf = 400 MHz) frequencies that span 1.6 GHz has been created. The center of the array bandwidth is tunable within the range of 75-97.8 GHz, which covers most of the W band (75-110 GHz). The incident angle can be adjusted from -4° to 12°, and the wavenumber range is 4-15 cm-1 with a wavenumber resolution of Δk/k ≤ 0.35. Ray tracing is used to calculate the scattering location and the scattering wavenumber. This article details the hardware design, the ray tracing, and the preliminary experimental results from EAST plasmas.

Correlation polarimetry for broadband magnetic fluctuation measurements.

Correlation techniques have been successfully utilized for plasma diagnostics like electron cyclotron emission to reduce measurement noise. We present the first application of such a technique to Faraday-effect polarimetry measurements on the Madison Symmetric Torus (MST). The MST far infrared (FIR) interferometer-polarimeter diagnostic utilizes 11 vertical chords with a chord separation of 7-8 cm and a heterodyne detection system for fluctuation measurements up to several hundred kHz. The planar-diode mixers viewing each chord represent independent noise sources; modifying the optical setup so that two different mixers view the same chord allows cross correlation between the two independent signals to reduce the noise floor in fluctuation measurements. In this manner, the noise floor in both interferometry and polarimetry measurements in reversed-field pinch discharges has been reduced by a factor of 20-30. The correlation polarimeter provides a sensitive measurement of broadband magnetic fluctuations.

A heterodyne dispersion interferometer for wide bandwidth density measurements on DIII-D.

In order to improve both the density and particularly the temporal resolution beyond previous dispersion interferometers (DIs), a heterodyne technique based on an acousto-optic (AO) cell has been added to the DI. A 40 MHz drive frequency for the AO cell allows density fluctuation measurements into the MHz range. A CO2 laser-based heterodyne DI (HDI) installed on DIII-D has demonstrated that the HDI is capable of tracking the density evolution throughout DIII-D discharges, including disruption events and other rapid transient phenomena. The data also show good agreement with independent density measurements obtained with the existing DIII-D two-color interferometer. The HDI line-integrated density resolution sampled over a 1 s interval is ∼9 × 1017 m-2. Density fluctuations induced by MHD instabilities are also successfully measured by the HDI.

A Faraday-effect polarimeter for fast magnetic dynamics measurement on DIII-D.

A Faraday-effect-based radial-interferometer-polarimeter diagnostic has been developed to explore fast magnetic dynamics in high-performance DIII-D plasmas. The instrument measures radial magnetic field perturbations using three chords positioned near the magnetic axis. Newly developed solid-state sources operating at 650 GHz provide phase noise down to 0.01°/ k H z and tunable bandwidth up to 10 MHz. Various systematic errors which can contaminate the polarimetric measurement have been investigated in detail. Distortion of circular polarization due to non-ideal optical components is calibrated using a rotating quarter wave plate technique. The impact of perpendicular magnetic field, i.e., the Cotton-Mouton effect, is evaluated. The error due to non-collinearity of probe beams is minimized to less than 0.5° for electron density up to 7 × 1019 m-3 by alignment optimization. Optical feedback, due to multiple reflections induced by the double-pass configuration, is identified and reduced. Coherent and broadband high-frequency magnetic fluctuations for DIII-D H-mode plasmas are observed.

Tests of a full-scale ITER toroidal interferometer and polarimeter (TIP) prototype on the DIII-D tokamak (invited).

A full-scale ITER toroidal interferometer and polarimeter (TIP) prototype, including an active feedback alignment system, has been installed and tested on the DIII-D tokamak. In the TIP prototype, a two-color interferometry measurement of line-integrated density is carried out at 10.59 µm and 5.22 µm using a CO2 and quantum cascade laser, respectively, while a separate polarimetry measurement of the plasma-induced Faraday effect is made at 10.59 µm. The TIP prototype is equipped with a piezo tip/tilt stage active feedback alignment system that minimizes noise in the measurement and keeps the diagnostic aligned throughout DIII-D discharges. The measured phase resolution for the polarimeter and interferometer is 0.05° (100 Hz bandwidth) and 1.9° (1 kHz bandwidth), respectively. The corresponding line-integrated density resolution for the vibration-compensated interferometer is δnL = 1.5 × 1018 m-2, and the magnetic field-weighted line-integrated density from the polarimeter is δnBL = 1.5 × 1019 Tm-2. Both interferometer and polarimeter measurements during DIII-D discharges compare well with the expectations based on calculations using Thomson scattering measured density profiles and magnetic equilibrium reconstructions. Additionally, larger bandwidth interferometer measurements show that the diagnostic is a sensitive monitor of core density fluctuations with demonstrated measurements of Alfvén eigenmodes and tearing modes.

Non-inductive vertical position measurements by Faraday-effect polarimetry on EAST tokamak.

Vertical instability control in an elongated plasma is highly desirable for a tokamak reactor. A multi-channel 694 GHz far-infrared laser-based polarimeter-interferometer system has been used to provide a non-inductive vertical position measurement in the long-pulse EAST tokamak. A detailed comparison of vertical position measurements by polarimetry and external inductive flux loops has been used to validate Faraday-effect polarimetry as an accurate high-time response vertical position sensor.

A novel, tunable, multimodal microwave system for microwave reflectometry system.

Based on a new technique, a tunable, multi-channel system that covers the Q-band (33-55 GHz) is presented in this article. It has a potential use of the Doppler backscattering system diagnostic that can measure the turbulence radial correlation and the perpendicular velocity of turbulence by changing the incident angle. The system consists primarily of a double-sideband (DSB) modulation and a multiplier, which creates four probing frequencies. The probing frequency enables the simultaneous analysis of the density fluctuations and flows at four distinct radial regions in tokamak plasma. The amplitude of the probing frequency can be adjusted by the initial phase of the intermediate frequency (IF) input from the double-sideband, and the typical flatness is less than 10 dB. The system was tested in the lab with a rotating grating, and the results show that the system can operate in the frequency range of 33-55 GHz with a Q-band multitude and that the power of each channel can be adjusted by the phase of the IF input of DSB.

Effects of stray lights on Faraday rotation measurement for polarimeter-interferometer system on EAST.

A double-pass radially view 11 chords polarimeter-interferometer system has been operated on the experimental advanced superconducting tokamak and provides important current profile information for plasma control. Stray light originating from spurious reflections along the optical path (unwanted reflections from various optical components/mounts and transmissive optical elements such as windows, waveplates, and lens as well as the detectors) and also direct feedback from the retro-reflector used to realize the double-pass configuration can both contribute to contamination of the Faraday rotation measurement accuracy. Modulation of the Faraday rotation signal due to the interference from multiple reflections is observable when the interferometer phase (plasma density) varies with time. Direct reflection from the detector itself can be suppressed by employing an optical isolator consisting of a λ/4-waveplate and polarizer positioned in front of the mixer. A Faraday angle oscillation during the density ramping up (or down) can be reduced from 5°-10° to 1°-2° by eliminating reflections from the detector. Residual modulation arising from misalignment and stray light from other sources must be minimized to achieve accurate measurements of Faraday rotation.

An eight-channel Doppler backscattering system in the experimental advanced superconducting tokamak.

Doppler backscattering system can measure the perpendicular velocity and fluctuation amplitude of the density turbulence with intermediate wavenumber. An eight-channel Doppler backscattering system has been installed in the Experimental Advanced Superconducting Tokamak (EAST), which can probe eight different radial locations simultaneously by launching eight fixed frequencies (55, 57.5, 60, 62.5, 67.5, 70, 72.5, 75 GHz) into plasma. The quasi-optical system consists of circular corrugated waveguide transmission, a fixed parabolic mirror, and a rotatable parabolic mirror which are integrated with quasi-optics front-end of the profile reflectometer inside the vacuum vessel. The incidence angle can be chosen from 5° to 12°, and the wavenumber range is 2-15/cm with the wavenumber resolution Δk/k≤0.21. Ray tracing simulations are used to calculate the scattering locations and the perpendicular wavenumber. The dynamic range of this new eight-channel Doppler backscattering system can be as large as 40 dB in the EAST. In this article, the hardware design, the ray tracing, and the preliminary experimental results in the EAST will be presented.

A novel approach to estimating the Doppler shift frequency from quadrature mixer output.

Doppler backscattering systems (DBSs) have been widely used in magnetic confinement fusion devices to measure the density fluctuations and propagation velocity of turbulence. However, the received signals of a DBS usually include both zero-order reflection and backscattering components, which results in interference in calculating the Doppler shift frequency from the backscattering components. A novel method is introduced here for estimating the Doppler shift frequency by separating the zero-order reflection and backscattering components using the cross-phase spectrum between the I-signal and Q-signal from a quadrature mixer, based on the difference in symmetrical characteristics between the zero-order reflection and backscattering signal spectra. It is proven that this method is more effective than traditional approaches, such as multiple signal classification and fast Fourier transformation, for extracting Doppler shift information.

Initial measurements of plasma current and electron density profiles using a polarimeter/interferometer (POINT) for long pulse operation in EAST (invited).

A double-pass, radially viewing, far-infrared laser-based POlarimeter-INTerferometer (POINT) system utilizing the three-wave technique has been implemented for diagnosing the plasma current and electron density profiles in the Experimental Advanced Superconducting Tokamak (EAST). POINT has been operated routinely during the most recent experimental campaign and provides continuous 11 chord line-integrated Faraday effect and density measurement throughout the entire plasma discharge for all heating schemes and all plasma conditions (including ITER relevant scenario development). Reliability of both the polarimetric and interferometric measurements is demonstrated in 25 s plasmas with H-mode and 102 s long-pulse discharges. Current density, safety factor (q), and electron density profiles are reconstructed using equilibrium fitting code (EFIT) with POINT constraints for the plasma core.

Faraday-effect polarimeter diagnostic for internal magnetic field fluctuation measurements in DIII-D.

Motivated by the need to measure fast equilibrium temporal dynamics, non-axisymmetric structures, and core magnetic fluctuations (coherent and broadband), a three-chord Faraday-effect polarimeter-interferometer system with fast time response and high phase resolution has recently been installed on the DIII-D tokamak. A novel detection scheme utilizing two probe beams and two detectors for each chord results in reduced phase noise and increased time response [δb ∼ 1G with up to 3 MHz bandwidth]. First measurement results were obtained during the recent DIII-D experimental campaign. Simultaneous Faraday and density measurements have been successfully demonstrated and high-frequency, up to 100 kHz, Faraday-effect perturbations have been observed. Preliminary comparisons with EFIT are used to validate diagnostic performance. Principle of the diagnostic and first experimental results is presented.

An upgraded interferometer-polarimeter system for broadband fluctuation measurements.

Measuring high-frequency fluctuations (above tearing mode frequencies) is important for diagnosing instabilities and transport phenomena. The Madison Symmetric Torus interferometer-polarimeter system has been upgraded to utilize improved planar-diode mixer technology. The new mixers reduce phase noise and allow more sensitive measurements of fluctuations at high frequency. Typical polarimeter rms phase noise values of 0.05°-0.07° are obtained with 400 kHz bandwidth. The low phase noise enables the resolution of fluctuations up to 250 kHz for polarimetry and 600 kHz for interferometry. The importance of probe beam alignment for polarimetry is also verified; previously reported tolerances of ≤0.1 mm displacement for equilibrium and tearing mode measurements minimize contamination due to spatial misalignment to within acceptable levels for chords near the magnetic axis.

[Effects of chronic intermittent hypoxia on hepatic function and protective mechanism of adiponectin in rats].

Objective: To explore the effect of chronic intermittent hypoxia (CIH) on rats hepatic function, and the protective mechanism of adiponectin (Ad). Methods: Sixty healthy male wistar rats were randomly divided into 4 groups: normal control (NC), NC+ Ad, CIH, and CIH+ Ad groups with 15 rats in each. The rats in CIH and CIH+ Ad groups were exposed to an intermittent hypoxic chamber 8 hours per day for 4 months. Meanwhile, the rats in both the NC and NC + Ad groups were housed with normal pressure air. The rats in the NC+ Ad and CIH+ Ad groups were additionally treated with an intravenous injection of Ad (10 µg), twice a week for 4 months. At the end of experiment, comparison among groups was made about plasma levels of aspartate amino transferase (AST), alanine amino transferase (ALT), degrees of endoplasmic reticulum stress (ERS) and mitochondrium associated cellular apoptosis. Results: No significant difference was detected in all items between NC and NC+ Ad groups (all P>0.05). Plasma hepatic enzyme levels of AST and ALT were significantly higher in CIH group [(319±21) and (113±9) U/L] than those in NC group [(178±19) and (51±9) U/L] and NC+ Ad group [(175±16) and (52±8) U/L] (all P<0.05). Compared NC with NC+ Ad group, there was more remarkable ERS and mitochondrial injury associated cellular apoptosis in hepatic tissues of CIH group. Such pathological changes were less obvious in CIH+ Ad group than in CIH group (all P<0.05). Conclusion: CIH can induce hepatic injury in rats, while Ad supplement may play a protective role possibly through inhibition of ERS and associated pathways of cellular apoptosis.

Bench testing of a heterodyne CO2 laser dispersion interferometer for high temporal resolution plasma density measurements.

A heterodyne detection scheme is combined with a 10.59 µm CO2 laser dispersion interferometer for the first time to allow large bandwidth measurements in the 10-100 MHz range. The approach employed utilizes a 40 MHz acousto-optic cell operating on the frequency doubled CO2 beam which is obtained using a high 2nd harmonic conversion efficiency orientation patterned gallium arsenide crystal. The measured standard deviation of the line integrated electron density equivalent phase resolution obtained with digital phase demodulation technique, is 4 × 1017 m-2. Air flow was found to significantly affect the baseline of the phase signal, which an optical table cover was able to reduce considerably. The heterodyne dispersion interferometer (DI) approach is found to be robustly insensitive to motion, with measured phase shifts below baseline drifts even in the presence of several centimeters of retroreflector induced path length variations. Plasma induced dispersion was simulated with a wedged ZnSe plate and the measured DI phase shifts are consistent with expectations.