Quasi-optical design for the cross-polarization scattering diagnostic on the HL-3 tokamak.

As the plasma beta (ß) increases in high-performance tokamaks, electromagnetic turbulence becomes more significant, potentially constraining their operational range. To investigate this turbulence, a cross-polarization scattering (CPS) diagnostic system is being developed on the HL-3 tokamak for simultaneous measurements of density and magnetic fluctuations. In this work, a quasi-optical system has been designed and analyzed for the Q-band CPS diagnostic. The system includes a lens group for beam waist size optimization, a rotatable wire-grid polarizer for polarization adjustment, and a reflector group for measurement range regulation and system response enhancement. Laboratory tests demonstrated a beam radius of order 4 cm at the target measurement location (near the plasma pedestal), cross-polarization isolation exceeding 30 dB, and poloidal and toroidal angle adjustment ranges of ±40° and ±15°, respectively. These results verify the system's feasibility through laboratory evaluations. The quasi-optical system has been installed on the HL-3 tokamak during the 2023 experimental campaign to support the development of CPS diagnostics.

Plasma position measurements by O-mode and X-mode reflectometry systems in tokamak plasmas.

Plasma Position Reflectometry (PPR) is planned to provide plasma position and shape information for plasma operation in future fusion reactors. Its primary function is to calibrate the drift of the magnetic signals due to the integral nature of magnetic measurement. Here, we attempt to measure plasma position using ordinary mode (O-mode) and extraordinary mode (X-mode) reflectometry systems on two tokamaks. A new physical model based on the phase shift is proposed to deduce the relative movement of the cut-off layer without density inversion. We demonstrate the plasma position measurements by absolute measurement from density profile inversion and relative measurement from phase shift. The combination of X-mode and O-mode reflectometers can minimize the limitations of single polarization reflectometry and further increase the accuracy of plasma position measurement. These results could provide an important technical basis for the further development of a real-time control system based on PPR.

Preliminary results of the 105 GHz collective Thomson scattering system on HL-2A.

A 105 GHz collective Thomson scattering (CTS) diagnostic has been successfully developed for fast-ion measurements on the HL-2A tokamak, and it has been deployed during an experimental campaign. Enhanced signals exhibiting synchronous modulation characteristics have been observed across all CTS channels upon the launch of a modulated probe wave. Results show that the intensity of the CTS signal increases with Neutral Beam Injection (NBI) power and is proportional to neutron count, indicating that the scattering signal contains a contribution from fast ions. Compared with the signal without NBI, the enhanced scattering spectrum due to NBI is slightly wider than the predicted fast ion range. Such broadening might be attributed to the heating effects of the gyrotron.

Design and first measurements of the fast-ion D-alpha diagnostic at the HL-2A tokamak.

The fast-ion D-alpha diagnostic (FIDA) is employed to detect Dα light emitted by neutralized fast ions during neutral beam injection. A tangentially viewing FIDA has been developed for the HuanLiuqi-2A (HL-2A) tokamak and typically achieves temporal and transverse spatial resolutions of ∼30 ms and ∼5 cm, respectively. A fast-ion tail on the red shifted wing of the FIDA spectrum is obtained and analyzed with the Monte Carlo code FIDASIM. Good agreement has been presented between the measured and simulated spectra. As the FIDA diagnostic's lines of sight intersect the central axis of neutral beam injection with small angles, the beam emission spectrum is observed with a large Doppler shift. Thus, tangentially viewing FIDA could detect only a small portion of fast ions with an energy of ≈ 20 ∼ 31 keV and a pitch angle of ≈ -1 ∼ -0.8. A second FIDA installation with oblique viewing is designed to minimize spectral contaminants.

MHD instability dynamics and turbulence enhancement towards the plasma disruption at the HL-2A tokamak.

The evolutions of MHD instability behaviors and enhancement of both electrostatic and electromagnetic turbulence towards the plasma disruption have been clearly observed in the HL-2A plasmas. Two types of plasma disruptive discharges have been investigated for similar equilibrium parameters: one with a distinct stage of a small central temperature collapse ([Formula: see text] 5-10%) around 1 millisecond before the thermal quench (TQ), while the other without. For both types, the TQ phase is preceded by a rotating 2/1 tearing mode, and it is the development of the cold bubble from the inner region of the 2/1 island O-point along with its inward convection that causes the massive energy loss. In addition, the micro-scale turbulence, including magnetic fluctuations and density fluctuations, increases before the small collapse, and more significantly towards the TQ. Also, temperature fluctuations measured by electron cyclotron emission imaging enhances dramatically at the reconnection site and expand into the island when approaching the small collapse and TQ, and the expansion is more significant close to the TQ. The observed turbulence enhancement near the X-point cannot be fully interpreted by the linear stability analysis by GENE. Evidences suggest that nonlinear effects, such as the reduction of local [Formula: see text] shear and turbulence spreading, may play an important role in governing turbulence enhancement and expansion. These results imply that the turbulence and its interaction with the island facilitate the stochasticity of the magnetic flux and formation of the cold bubble, and hence, the plasma disruption.

A gamma ray spectrometer with Compton suppression on the HL-2A tokamak.

A new broad-energy, high-resolution gamma ray spectrometer (GRS) with Compton suppression function has been developed recently in the HL-2A tokamak to obtain the gamma ray information in the energy range of 0.1-10 MeV. This is the first time to develop an anti-Compton GRS for a magnetic confinement fusion device. The anticoincidence detector consists of a large-volume high purity germanium (HPGe) crystal (Φ63 × 63 mm2) as the primary detector and eight trapezoidal bismuth germinate (BGO) scintillators (trapezoid crystal with 30 mm thickness) as the secondary detector. The anti-coincidence data processing is implemented by a digital-based data acquisition system with fast digitization and software signal processing technology. Using radioisotope gamma ray sources and Monte Carlo N-Particle code, the energy and efficiency of the spectrometer have been calibrated and quantitatively tested. The Compton continuum suppression factor reaches 4.2, and the energy resolution (Full Width at Half Maximum) of the 1.332 MeV full energy peak for 60Co is 2.1 keV. Measurements of gamma ray spectra with Compton suppression using the spectrometer have been successfully performed during HL-2A discharges with different conditions. The performance of the spectrometer and the first experimental results are presented in this paper.

Visible imaging system with changeable field of view on the HL-2A tokamak.

A new visible imaging system characterizing a flexible optical design and delivering high resolution frames is established on the HL-2A tokamak. It features a modular configuration, consisting of a front-end imaging lens, a set of bilateral telecentric relay lenses, and a camera. To avoid the effects of plasma radiation (x and gamma-rays) and magnetic field variation on the camera, it should be away from the coils. Therefore, the length of the relay lenses determines the total size of the imaging system. The main feature of this imaging system is to realize the variation of field of view (FOV) by interchanging the front-end prime lenses or by using a zoom lens directly rather than designing the optical system afresh, which lowers the cost drastically. The primary purpose of varying FOV is to enrich the versatility of this system, i.e., focusing on a narrow FOV such as gas puff imaging or a wide FOV such as the plasma cross sections. During the HL-2A experiments, this visible imaging system is used to provide high quality pictures of the plasma-wall interaction, divertor detachment, pellet injections, and so on. The frames confirmed that a strong radiation close to the X point is correlated with the completely detached inner target.

Analysis of synthetic electron cyclotron emission from the high field side of HL-2M tokamak plasmas.

A synthetic electron cyclotron emission (ECE) diagnostic is used to interpret ECE signals from preset plasma equilibrium profiles, including magnetic field, electron density, and electron temperature. According to the simulation results, the electron temperature (Te) profile covering the harmonic overlap region can be obtained by receiving ECE signals at the high field side (HFS) of the HL-2M plasma. The third harmonic ECE at the low field side (LFS) cannot pass through the second harmonic resonance layer at the HFS unless the optical thickness (τ) of the second harmonic becomes gray (τ ≤ 2). In addition, the impact of the relativistic frequency down-shift has been evaluated and corrected. The measurable range of the HFS ECE has been calculated by scanning different parameters (electron density, temperature, and magnetic field). Higher plasma parameters allow a wider radial range of electron temperature measurements. The minimum inner measurable position can reach R = 120 cm (r/a = -0.89) when the product of core temperature (Te0) and density (ne0) is greater than 35 × 1019 keV m-3, which is extended by more than 30 cm inward compared with that of the LFS measurement. The HFS ECE will greatly improve the diagnostic ability of ECE systems on the HL-2M tokamak.

Development of solid state terahertz interferometer for the first plasma on HL-2M tokamak.

A solid state terahertz interferometer has been developed on the recent commissioned HL-2M tokamak. It can work in a wide frequency region of 220-325 GHz, and the terahertz wave is generated from a low frequency phase locked voltage controlled oscillator with the frequency multiplying technique. A phase processor based on field programmable gate array (FPGA) technology is designed for the heterodyne interferometer, and it contributes to real-time display of electron density. To extract phase information, a novel numerical algorithm related to fast Fourier transform is written on the FPGA chip and enables one to obtain phase shift without being affected by amplitude variation induced by plasma absorption or frequency modulation from the outer electromagnetic environment. The interferometer achieves minimum measurable electron density in the order of 1016 m-3. With the plasma diagnosis, electron density and low frequency tearing mode have been measured during the first experimental campaign.

A remote gain controlled and polarization angle tunable Doppler backward scattering reflectometer.

Remote control of the diagnostic systems is the basic requirement for the high performance plasma operation in a fusion device. This work presents the development of the remote control system for the multichannel Doppler backward scattering (DBS) reflectometers. It includes a remote controlled quasi-optical system and a remote intermediate frequency (IF) amplifier gain control system. The quasi-optical system contains a rotational polarizer, its polarization angle is tunable through a remote controlled motor, and it could combine the microwave beams with a wide frequency range into one focused beam. The remote IF gain control system utilizes the digital microcontroller (MCU) technique to regulate the signal amplitude for each signal channel. The gain parameters of amplifiers are adjustable, and the feedback of working status in the IF system will be sent to MCU in real time for safe operation. The gain parameters could be controlled either by the Ethernet remote way or directly through the local control interface on the system. Preliminary experimental results show the effectiveness of the remote controlled multichannel DBS system.

Visible wide-angle view imaging system for the first plasma on the HL-2M tokamak.

The wide-angle view imaging system, in terms of a tangential view diagnostic with field of view (FOV) of 56.8° and a downward-looking diagnostic from the top of the machine with FOV of 94.7°, has been newly constructed for the first plasma of the HL-2M tokamak achieved in December 2020. Its mission in this stage is to monitor the plasma evolution during its startup, sustainment, and disruption in the visible spectral range as well as the plasma-wall interaction. For the latter ultrawide view diagnostic, nearly three-quarters of the divertor region and half the area of the inner wall are in the view range. Both the diagnostics are characterized by a similar optical structure, i.e., the light emission from the plasma is collected by a front-end lens and transferred through an imaging fiber bundle to the camera. This optical structure is suitable for application in the complex tokamak environment mainly because the fiber bundle is flexible. Photos of glow discharges are acquired prior to the first plasma for testing the FOVs in the vacuum vessel. The spatial resolution is ∼4mm for the tangential view diagnostic and ∼10mm for the downward-looking diagnostic. The temporal resolutions, ranging from 90 to 360 Hz by changing the region of interest or binning acquisition mode of the color camera, are applied to record the plasma evolutions and/or dust creation events during the first plasma campaign.

Development of a tunable multi-channel Doppler reflectometer on J-TEXT tokamak.

Doppler reflectometer is a powerful diagnostic tool to study the turbulence for tokamak plasmas. It can provide information on the density fluctuation, the poloidal rotation, the radial electric field, its shear, etc. A tunable multi-channel V-band (50-75 GHz) Doppler reflectometer system has been developed on the J-TEXT tokamak for the measurement under various toroidal magnetic fields. A universal serial bus controlled synthesizer is used as a source that can adjust the probing frequency remotely. This Doppler reflectometer can measure the plasma in 0.3 < ρ < 1 . Its radial resolution is <2 cm, and k⊥ is ∼ 4-12 cm-1. Based on the Doppler reflectometer, the perpendicular turbulence propagation velocity, the profile of the radial electric field, the geodesic acoustic mode, and some other phenomena have been observed on J-TEXT.

Experimental study of perturbative particle transport in the HL-2A tokamak.

Perturbative particle transport experiment has been performed in the HL-2A tokamak by using supersonic molecular beam injection (SMBI) as an external particle source. The spatiotemporal evolution of edge density perturbation is traced and the particle source and the flux-gradient relation are obtained experimentally. The flux-gradient relation is found to be far from the diffusive model and three different transport processes are revealed, including pinch-dominant process, diffusion-pinch process and intermittent decays.

Fast charge exchange recombination spectroscopy on HuanLiu-2A tokamak.

A Fast Charge eXchange Recombination Spectroscopy (CXRS) diagnostic with eight radial channels has been implemented on a HuanLiu-2A (HL-2A) tokamak with a time resolution of up to 10 kHz monitoring helium II spectra or 1 kHz monitoring carbon VI spectra. The crucial aspects of the fast CXRS are to improve the spectral intensity and the acquisition frequency. The spectral intensity has been greatly enhanced by customized fiber bundles. The main boost in optimizing the acquisition frequency is achieved by binning more pixel rows of the charge coupled device (CCD) representing one radial channel and by reducing the effective image area of the CCD. Consequently, the sawtooth oscillations of ion temperature and rotation velocity are continuously observed for the first time in the HL-2A tokamak.

CircPSM3 inhibits the proliferation and differentiation of OA chondrocytes by targeting miRNA-296-5p.

OBJECTIVE: Osteoarthritis (OA) is a common chronic bone and joint disease. Circular RNA is a type of non-coding RNA that forms a circular structure with covalent bonds. There is growing evidence that circRNA can function as a functional RNA and play an important role in the occurrence and development of osteoarthritis chondrocytes. However, the exact role of circRNA on OA remains to be studied. PATIENTS AND METHODS: Quantificational real-time polymerase chain reaction (qRT-PCR) was used to determine the expression levels of CircPSM3 and miRNA-296-5p in OA chondrocytes. Cell proliferation was detected by the Cell Counting Kit (CCK8), and BMP2, BMP4, BMP6 and RUN2 molecular levels in OA chondrocytes were detected by qRT-PCR and Western Blot (WB). Direct targets of CircPSM3 and miRNA-296-5p in OA chondrocytes were measured by Luciferase reporter assay. RESULTS: CircPSM3 expression was upregulated in OA cartilage tissue and cells. Low expression of CircPSM3 promoted the proliferation and cell differentiation of OA chondrocytes. Meanwhile, miRNA-296-5p was down-regulated in OA cartilage tissue and cells. The Luciferase reporter gene showed that CircPSM3 could target miRNA-296-5p. The expression level of CircPSM3 and miRNA-296-5p showed a negative correlation. Further research found that a high expression of miRNA-296-5p could effectively promote the proliferation and cell differentiation of OA chondrocytes. Furthermore, miRNA-296-5p inhibitors reversed the effect of si-CircPSM3 on the proliferation and differentiation of OA chondrocytes, while miRNA-296-5p inhibitors enhanced the effect of si-CircPSM3 on the proliferation and differentiation of OA chondrocytes. CONCLUSIONS: CircPSM3 was upregulated in OA chondrocytes. CircPSM3 participated in the proliferation and differentiation of OA chondrocytes through targeted binding to miRNA-296-5p. CircPSM3 may become a potential therapeutic target for osteoarthritis treatment.

An eight-channel correlation electron cyclotron emission diagnostic for turbulent electron temperature fluctuation measurement in HL-2A tokamak.

A new correlation electron cyclotron emission (CECE) diagnostic has recently been installed on the HL-2A tokamak in order to study electron temperature fluctuations. Eight radial locations are measured simultaneously through eight pairs of correlated channels. Multiplexers are employed in the intermediate frequency section instead of the conventional separated filter banks to meet strict cross-isolation specifications and lower insertion loss. Relative electron temperature fluctuations are observed by CECE for the first time on the HL-2A by using the spectral decorrelation method. The achieved minimum detectable fluctuation level is up to (T̃e/Te)min∼0.5%. When studying electron temperature fluctuations in the core region with gas puffing, the cross-power spectra show that the amplitude of the electron temperature fluctuation increases in a high temperature and low density plasma. Further analysis demonstrates that the electron temperature gradient ∇Te drives the electron temperature fluctuations together with electron heat transport.

High-sensitivity far-forward collective scattering diagnostic on HL-2A tokamak.

The multichannel formic acid (HCOOH, λ = 432.5 µm) laser interferometer and Faraday-effect polarimeter on HL-2A tokamak have been developed to measure the far-forward collective scattering from electron density fluctuations. The far-forward collective scattering system provides eight channels of line-integrated electron density fluctuations, covering the wave-number range: k⊥ < 1.6 cm-1. With the new diagnostic, the density fluctuations caused by plasma energetic particles and turbulence have been routinely observed in HL-2A experiments.

Efficacy of multimodal perioperative analgesia protocol with periarticular medication injection and nonsteroidal anti-inflammatory drug use in total knee arthroplasty.

BACKGROUND: This research examined multimodal analgesia and the use of nonsteroidal anti-inflammatory drugs (NSAIDs) for early analgesic effect and rehabilitation after total knee arthroplasty (TKA). METHODS: A total of 110 patients who were scheduled to undergo TKA were randomly divided into two groups, experimental group and control group. The experimental group received a periarticular multimodal drug injection containing 200 mg ropivacaine, 30 mg ketorolac tromethamine, 0.3 mg epinephrine, and 5 mg hexadecadrol during surgery. The control group received an equal volume of normal saline. All the patients received an analgesia pump and moderate NSAIDs. Resting and motion numeric rating scale (NRS) scores, knee joint range of motion, length of postoperative hospital stay, patient satisfaction, total nonsteroidal anti-inflammatory consumption, and side effects were recorded. RESULTS: The experimental group exhibited significant improvement in pain NRS scores during rest and exercise several days postoperatively. The range of joint motion was more flexible in the experimental group, and the length of postoperative hospital stay was shorter (9.25 ± 1.99 days vs. 10.44 ± 2.62 days, P < 0.05). Patients in the experimental group consumed fewer NSAIDs (965 mg vs. 1325 mg, P < 0.05) and reported greater satisfaction with the surgery. CONCLUSION: Intraoperative periarticular injection with multimodal drugs significantly relieved pain after surgery and reduced the requirements for NSAIDs. This injection also improved patient satisfaction and the range of joint motion with no apparent risks following TKA.

Note: Real-time wavelength matching system designed for the motional Stark effect polarimeter on HL-2A tokamak.

A 7-channel motional Stark effect diagnostic based on dual photo-elastic modulators is installed and operated routinely for rather low beam energy and magnetic field on the HL-2A tokamak, with a spatial resolution of ∼3 cm and a temporal resolution of 10 ms. The instrument observes the σ component of the full energy Dα from the first or the fourth ion source of a neutral beam injector. However, the change in beam energy during a discharge causes variation of the Doppler shift with the maximum of 1 Å, which leads to the polarization fraction drop from 30%-40% to 10% and then makes the signal-to-noise ratio of the system become very poor. Therefore, a real-time wavelength matching system is designed to promote polarization fraction. The beam emission spectra are filtered by using a monochrometer in real time. And a narrowband filter is tilted by using an absolutely calibrated rotator through beam energy in order to make sure that the deviation of wavelength matching is less than 0.1 Å.

Bayesian tomography and integrated data analysis in fusion diagnostics.

In this article, a Bayesian tomography method using non-stationary Gaussian process for a prior has been introduced. The Bayesian formalism allows quantities which bear uncertainty to be expressed in the probabilistic form so that the uncertainty of a final solution can be fully resolved from the confidence interval of a posterior probability. Moreover, a consistency check of that solution can be performed by checking whether the misfits between predicted and measured data are reasonably within an assumed data error. In particular, the accuracy of reconstructions is significantly improved by using the non-stationary Gaussian process that can adapt to the varying smoothness of emission distribution. The implementation of this method to a soft X-ray diagnostics on HL-2A has been used to explore relevant physics in equilibrium and MHD instability modes. This project is carried out within a large size inference framework, aiming at an integrated analysis of heterogeneous diagnostics.