Balanced detector is a fundamental component for the accurately measuring quantum state fluctuations, especially quantum noise, which is crucial for future quantum-enhanced interferometric gravitational wave detectors utilizing squeezed light. By using a transimpedance amplifier (TIA) model core for balanced detection, a detailed theoretical and practical analysis is conducted on the electronic factors that affect the performance of the detector in the target ultra-low-frequency range. The TIA stage is meticulously designed using a highperformance integrated operational amplifier characterized by low offset voltage drift. In order to ensure the critical gain stability for ultra-low-frequency operation, this design adopts low temperature-drift metal foil resistors. Subsequent voltage amplification is achieved using a noninverting amplifier configuration to attain the necessary high electrical gain, while strictly managing overall electronic noise. By recognizing the criticality of common-mode noise rejection for quantum noise measurements, the photodiode (PD) nonlinear response compensation mechanism is analyzed and optimized. This is achieved through the innovative implementation of a differential fine-tuning circuit (DFTC) coupled with an adjustable bias voltage (ABV) compensation scheme. Experimental validation confirms the effectiveness of the optimized design. The compensation scheme utilizing DFTC and ABV successfully achieves a high common mode rejection ratio (CMRR) exceeding 75 dB@500 Hz. Crucially, the detector achieves an electronic noise spectral density of 3.5 x 10(-5) V/Hz(1/2) within the 1 mHz(-1) Hz band, exceeding the requirements for laser intensity noise (1 x 10(-4) V/Hz(1/2)) in space-based gravitational wave detection. Furthermore, the detector demonstrates high gain capability and bandwidth: with an incident detection light power of 4 mW, the balanced detector achieves a gain of 20 dB maintained in a wide frequency range from 1 mHz to 1 MHz. This work presents the design, detailed analysis, and experimental realization of optimized balanced detectors specifically tailored for high-sensitivity measurements in the millihertz gravitational wave frequency band. The achieved low electronic noise base below 1 Hz and high CMRR meet the key requirements for future space-based gravitational wave detectors to detect squeezed states of light. This optimized balanced detector provides important components and technical support for the next-generation space-based gravitational wave detection and millihertz squeezed light characterization.

Neutral Beam Injection(NBI)is an important auxiliary heating and driving method for Tokamak devices.The ionization of neutral atoms determines the neutral beam heating(energy and particle deposition profile)andcurrent drive efficiency.In general,the attenuation characteristics of the neutral beam are simulated by using the background plasma parameters and neutral beam parameters,and then the heating and current driving effects of the Tokamak neutral beam are analyzed.Beam emission spectroscopy is a series of characteristic spectral lines radiated by the excitation and deexcitation process of electron and ion collision of neutral beam-injected plasma.The strength of Beam emission spectroscopy is affected by plasma density,temperature,energy beam,beam density and other factors,so neutral beam attenuation can be acquired using the beam emission spectrum.This paper analyses neutral beam attenuation under different plasma densities and different neutral beam energies on EAST.Comparing the experimental and Simulation of Spectra(SOS)results,the experimental and simulation results are in good agreement.The feasibility of obtaining neutral beam attenuation characteristics by measuring the Beam emission spectroscopy is verified.

Plasma spontaneous rotation significantly affects confinement performance and stability in tokamaks. Effectively inducing this rotation is essential for stabilizing resistive wall modes (RWMs) and ensuring the stable operation of the International Thermonuclear Experimental Reactor (ITER). Recent experiments conducted on the Korea Superconducting Tokamak Advanced Research (KSTAR) device demonstrated that resonant magnetic perturbations (RMPs) can induce neoclassical toroidal viscosity (NTV) torque under certain conditions, successfully driving plasma rotation. Similarly, on the Experimental Advanced Superconducting Tokamak (EAST), an increase in plasma rotation in the direction of the plasma current has been observed following RMP application. However, unlike the KSTAR findings, the NTV torque simulations for EAST are two orders of magnitude lower than experimental measurements, indicating additional mechanisms beyond NTV may drive the observed plasma rotations. In this paper, to investigate these mechanisms, momentum balance, causality, and statistical analyses are performed at EAST. An increase in rotation velocity is found to correlate with significant changes in the E x B flow, matching the RMP-induced torque distribution. This alignment suggests that residual stress, arising from variations in E x B shear, may cause the observed rotation to increase. The effects of stochastic fields on multi-scale turbulence are considered as a possible explanation for correlations between E x B velocity and toroidal rotation. Stochastic fields appear to enhance the inertia of large-scale turbulence while driving small-scale turbulence to maintain quasi-neutrality. The resulting turbulent Reynolds stress, generated by small-scale turbulence, may account for the increases of the observed velocity during RMP application. Statistical analysis further highlights the importance of island width in understanding the threshold RMP current in ramping-up RMP experiments, supporting the conclusion that turbulence-driven E x B shear-related residual stress is the key mechanism of driving plasma rotation following RMP application. ExB

A new front-end ASIC named ”PIST” (pico-second timing) has been successfully developed using 55 nm CMOS technology for the silicon photomulplier (SiPM) readout with a single channel with a major aim of fast timing. We performed extensive tests to evaluate the timing performance of a dedicated test stand equipped with a PIST chip. The results show that the system timing resolution can reach sub 10 ps for large SiPM signals, while the PIST intrinsic timing resolution is better than 5 ps. The PIST dynamic range has been further extended using the time-over-threshold (ToT) technique. Meanwhile, we fully characterised a new commercially available SiPM-readout 32-channel ASIC for developments of future high-granularity crystal calorimetry, including the single photon calibration and the dynamic range of different gain regions. Other promising potentials include fast timing resolution, fast readout speed and low power dissipation. Comprehensive measurements were made with a laser beam and high-energy particle beams with crystals and SiPMs. First testing results show that this chip has an excellent signal-to-noise and a large dynamic range. This contribution will introduce the ASICs as well as dedicated test stands and also present highlighted results including the timing resolution, single photon calibration and dynamic range.

In this paper, the impact of the back-gate voltage (Vb) on the low-frequency (1/f) noise is evaluated for the 180 nm double silicon-on-insulator (DSOI) NMOS, fabricated with various thicknesses of first buried oxide (BOX1) layer (145/50 nm). Both positive and negative V b increased the measured normalized drain current power spectral density (PSD) for more than ten-fold in DSOI standard devices with 145 nm BOX1, while the normalized PSD decreases with V b going up in devices with 50 nm BOX1. By comparing with CNF+CMF model, interface trap density and the Coulomb scattering coefficient are extracted with the back-gate voltage applied. The interface trap density increases in standard devices for both positive and negative V b , but decreases with increasing back-gate biasing from - 10 V to 10 V in devices with 50 nm BOX1. The interface trap density shows a similar back-gate coupling effect with threshold voltage under the influence of different thickness of BOX1. The CNF and CMF noise variation under back-gate voltage can be explained by the significant fluctuation in drain current.

A pico-second timing (PIST) front-end electronic chip has been developed using 55nm CMOS technology for future electron-positron collider experiments (namely Higgs factories). Extensive tests have been performed to evaluate the timing performance of a dedicated SiPM-readout system equipped with a PIST chip. The results show that the system timing resolution can achieve 30ps for SiPM signals corresponding to minimum-ionizing particles (MIP) level (200p.e.) and better than 10ps for signals larger than 800p.e., while the PIST intrinsic timing resolution is 4.76±0.09ps. The time-over-threshold (ToT) response of the PIST ASIC has been attained, which can cover the SiPM response spanning from ∼560p.e. to ∼25,000p.e..

This short communication presents an analog front-end (AFE) circuit used in the switched-capacitor array (SCA) for the waveform sampling ASIC. The idea to use in SCA-AFE native transistors which are common in today's CMOS technologies offers a feasible solution to the issue of achieving picosecond time resolution with a low supply voltage. The circuit features a MOS capacitor and a source follower both of which are implemented with the native transistors, and a simple rail-to-rail comparator. A prototype PISTWAVE1 ASIC is designed in a 55 nm CMOS with a single 1.2 V supply voltage, the experimental results show the ASIC achieves a dynamic range of 0.1∼1.1 V, a 65.3 dB signal-to-noise ratio (SNR) with voltage calibration and a less than 10 ps time resolution. The overall power consumption is less than 10 mW/channel at a sampling rate of nearly 6 GS/s.

For more than two decades, amplifier–discriminator application-specific integrated circuits (ASICs) have been demonstrated to be the optimal choice for time measurement in high-energy physics experiments. With the requirement of time resolution further evolving toward the picosecond and subpicosecond ranges, circuit innovation has become increasingly essential. We present a picosecond timing (PIST1) ASIC, using the conventional amplifier–discriminator architecture and optimized for the readout of silicon photomultipliers (SiPMs) in the electromagnetic calorimeter (ECAL) for future Higgs factories such as the circular electron positron collider (CEPC). Further circuit developments are made to enable the ASIC to operate under minimal power with reduced supply voltage. A comprehensive analysis of the noise in the signal link is also conducted, and the findings are presented. A single-channel prototype is designed in the 55-nm CMOS with a single 1.2-V supply voltage. The standalone ASIC testing highlights a time resolution of 4.20± 0.04 ps for a minimum ionizing particle (MIP) which is equivalent to 32-pC charge. In addition, a linear time-over-threshold (ToT) response from 1 to 12 MIP is attained, and a typical 15-mW power consumption is realized.

Sawtooth oscillation is one of the most important magneto-hydrodynamic (MHD) instabilities in Tokamak plasma, which can result in the periodic relaxation of the temperature and density of the core plasma when the safety factor on the magnetic axis (q0) is lower than unity. Owing to the periodic relaxation of the plasma core parameters, sawtooth oscillations are beneficial to avoiding impurity accumulation in plasma core. However, the large sawtooth crash may trigger off other MHD instabilities, like tearing modes (TMs) or neoclassical tearing modes (NTMs), which is a matter of concern for the plasma stability. Therefore, it is essential to control sawtooth oscillations for ensuring safe operation in the future Tokamaks such as ITER. The resonant magnetic perturbation (RMP) is widely used to control edge-localized modes (ELMs) and divertor heat flux in Tokamak. The application of RMP has also been found to affect the sawtooth behaviors. This paper studies the influence of RMP coils at n = 2 on sawtooth behaviors in experimental advanced superconducting Tokamak (EAST), where n is the toroidal mode number of the applied RMP. It is found that the phase difference between upper RMP coil and lower RMP coil (\begin{document}$ \Delta {\phi }_{{\rm{U}}{\rm{L}}}\left(^\circ\right)={\phi }_{{\rm{U}}}\left(^\circ\right)-{\phi }_{{\rm{L}}}\left(^\circ\right) $\end{document}) is a notable parameter of affecting sawtooth behavior. The experiments for scanning the phase difference \begin{document}$ \Delta {\phi }_{{\rm{U}}{\rm{L}}} $\end{document} are carried out. When the phase difference \begin{document}$ \Delta {\phi }_{{\rm{U}}{\rm{L}}} $\end{document} of RMP at n = 2 is changed, the sawtooth period and amplitude become subsequently different. The minimum sawtooth period and amplitude appear at \begin{document}$\Delta {\phi }_{{\rm{U}}{\rm{L}}}=270^\circ$\end{document}. At the same time, neutron yields measured by neutron diagnostic system have the same trend as sawtooth behavior during RMP phase difference scanning. The plasma response to RMP at n = 2 is analyzed by using the MARS-F code. The results show that the plasma responses much strongly at the \begin{document}$\Delta {\phi }_{{\rm{U}}{\rm{L}}}=270^\circ$\end{document}. The loss of fast ion, caused by RMP coils, is possibly stronger at the \begin{document}$\Delta {\phi }_{{\rm{U}}{\rm{L}}}=270^\circ$\end{document} than that at other phase difference \begin{document}$ \Delta {\phi }_{{\rm{U}}{\rm{L}}}. $\end{document} The loss of fast ion can reduces its stabilization effect on sawtooth behavior, which results in the reduction of the sawtooth period and amplitude. Further research is needed to optimize the sawtooth control method with RMP to make it compatible with plasma performance.

The LE is the low energy telescope that is carried on Insight -HXMT. It uses swept charge devices (SCDs) to detect soft X-ray photons. LE’s time response is caused by the structure of the SCDs. With theoretical analysis and Monte Carlo simulations we discuss the influence of LE time response (LTR) on the timing analysis from three aspects: the power spectral density, the pulse profile and the time lag. After the LTR, the value of power spectral density monotonously decreases with the increasing frequency. The power spectral density of a sinusoidal signal reduces by a half at frequency 536 Hz. The corresponding frequency for quasi-periodic oscillation (QPO) signals is 458 Hz. The root mean square (RMS) of QPOs holds a similar behaviour. After the LTR, the centroid frequency and full width at half maxima (FWHM) of QPOs signals do not change. The LTR reduces the RMS of pulse profiles and shifts the pulse phase. In the time domain, the LTR only reduces the peak value of the cross-correlation function while it does not change the peak position; thus it will not affect the result of the time lag. When considering the time lag obtained from two instruments and one among them is LE, a 1.18 ms lag is expected caused by the LTR. The time lag calculated in the frequency domain is the same as that in the time domain.

We present the observational results from a detailed timing analysis of the black hole candidate EXO 1846–031 during its outburst in 2019 with the observations of Insight -HXMT, NICER and MAXI . This outburst can be classified roughly into four different states. Type-C quasi-periodic oscillations (QPOs) observed by NICER (about 0.1–6 Hz) and Insight -HXMT (about 0.7–8 Hz) are also reported in this work. Meanwhile, we study various physical quantities related to QPO frequency. The QPO rms–frequency relationship in the energy band 1–10 keV indicates that there is a turning pointing in frequency around 2 Hz, which is similar to that of GRS 1915+105. A possible hypothesis for the relationship above may be related to the inclination of the source, which may require a high inclination to explain it. The relationships between QPO frequency and QPO rms, hardness, total fractional rms and count rate have also been found in other transient sources, which can indicate that the origin of type–C QPOs is non-thermal.

A black hole X-ray binary produces hard X-ray radiation from its corona and disk when the accreting matter heats up. During an outburst, the disk and corona co-evolves with each other. However, such an evolution is still unclear in both its geometry and dynamics. Here we report the unusual decrease of the re fl ection fraction in MAXI J1820 + 070, which is the ratio of the coronal intensity illuminating the disk to the coronal intensity reaching the observer, as the corona is observed to contrast during the decay phase. We postulate a jet-like corona model, in which the corona can be understood as a standing shock where the material fl owing through. In this dynamical scenario, the decrease of the re fl ection fraction is a signature of the corona ’ s bulk velocity. Our fi ndings suggest that as the corona is observed to get closer to the black hole, the coronal material might be out fl owing faster.

In the above article [1], on p. 1181, Fig. 7 appears the same as Fig. 6, which is incorrect. Instead, Fig. 7 should appear as below.

As China's first X-ray astronomical satellite, the Hard X-ray Modulation Telescope (HXMT), which was dubbed as Insight-HXMT after the launch on June 15, 2017, is a wide-band (1-250 keV) slat-collimator-based X-ray astronomy satellite with the capability of all-sky monitoring in 0.2-3 MeV. It was designed to perform pointing, scanning and gamma-ray burst (GRB) observations and, based on the Direct Demodulation Method (DDM), the image of the scanned sky region can be reconstructed. Here we give an overview of the mission and its progresses, including payload, core sciences, ground calibration/facility, ground segment, data archive, software, in-orbit performance, calibration, background model, observations and some preliminary results.

Low-frequency quasi-periodic oscillations (LFQPOs) are commonly found in black hole X-ray binaries, and their origin is still under debate. The properties of LFQPOs at high energies (above 30 keV) are closely related to the nature of the accretion flow in the innermost regions, and thus play a crucial role in critically testing various theoretical models. The Hard X-ray Modulation Telescope (Insight-HXMT) is capable of detecting emissions above 30 keV, and is therefore an ideal instrument to do so. Here we report the discovery of LFQPOs above 200 keV in the new black hole MAXI J1820+070 in the X-ray hard state, which allows us to understand the behaviours of LFQPOs at hundreds of kiloelectronvolts. The phase lag of the LFQPO is constant around zero below 30 keV, and becomes a soft lag (that is, the high-energy photons arrive first) above 30 keV. The soft lag gradually increases with energy and reaches 0.9s in the 150-200 keV band. The detection at energies above 200 keV, the large soft lag and the energy-related behaviors of the LFQPO pose a great challenge for most currently existing models, but suggest that the LFQPO probably originates from the precession of a small-scale jet.

The recently discovered neutron star transient Swift J0243.6+6124 has been monitored by the Hard X-ray Modulation Telescope. Based on the obtained data, we investigate the broadband spectrum of the source throughout the outburst. We estimate the broadband flux of the source and search for possible cyclotron line in the broadband spectrum. However, no evidence of line-like features is found up to 150 keV. In the absence of any cyclotron line in its energy spectrum, we estimate the magnetic field of the source based on the observed spin evolution of the neutron star by applying two accretion torque models. In both cases, we get consistent results with B similar to 10(13) G, D similar to 6 kpc and peak luminosity of >10(39) erg s(-1), which makes the source the first Galactic ultraluminous X-ray source hosting a neutron star.

In this paper we present the enhanced X-ray Timing and Polarimetry mission—eXTP. eXTP is a space science mission designed to study fundamental physics under extreme conditions of density, gravity and magnetism. The mission aims at determining the equation of state of matter at supra-nuclear density, measuring effects of QED, and understanding the dynamics of matter in strong-field gravity. In addition to investigating fundamental physics, eXTP will be a very powerful observatory for astrophysics that will provide observations of unprecedented quality on a variety of galactic and extragalactic objects. In particular, its wide field monitoring capabilities will be highly instrumental to detect the electro-magnetic counterparts of gravitational wave sources. The paper provides a detailed description of: (1) the technological and technical aspects, and the expected performance of the instruments of the scientific payload; (2) the elements and functions of the mission, from the spacecraft to the ground segment.

This paper designs a 4M-pixel/s 4-channel X-ray CCD readout circuit.In each channel,there are two modulators work alternatively to speed up the readout rate.Using modulator structure containing shifted loop delay (SLD)makes it easier to realize the required conversion speed.In order to achieve the required data processing speed and obtain the smaller filter area,the structure of the down sampling filter is carefully optimized.The 4- channel X-ray CCD readout system based on the incrementalΣΔ converter is implemented using the 2P4M0.35 μm process.The circuit works under supply voltage of 3.3Vand clock frequency of 64MHz.The post-simulation results show that its equivalent input-referred noise is 13.53μV and the integral nonlinearity is 0.009 6％.The whole system's power consumption is 1.35W.

Finding the electromagnetic (EM) counterpart of binary compact star merger, especially the binary neutron star (BNS) merger, is critically important for gravitational wave (GW) astronomy, cosmology and fundamental physics. On Aug. 17, 2017, Advanced LIGO and Fermi /GBM independently triggered the first BNS merger, GW170817, and its high energy EM counterpart, GRB 170817A, respectively, resulting in a global observation campaign covering gamma-ray, X-ray, UV, optical, IR, radio as well as neutrinos. The High Energy X-ray telescope (HE) onboard Insight -HXMT (Hard X-ray Modulation Telescope) is the unique high-energy gamma-ray telescope that monitored the entire GW localization area and especially the optical counterpart (SSS17a/AT2017gfo) with very large collection area (~1000 cm 2 ) and microsecond time resolution in 0.2-5 MeV. In addition, Insight -HXMT quickly implemented a Target of Opportunity (ToO) observation to scan the GW localization area for potential X-ray emission from the GW source. Although Insight -HXMT did not detect any significant high energy (0.2-5 MeV) radiation from GW170817, its observation helped to confirm the unexpected weak and soft nature of GRB 170817A. Meanwhile, Insight -HXMT/HE provides one of the most stringent constraints (~10 ‒7 to 10 ‒6 erg/cm 2 /s) for both GRB170817A and any other possible precursor or extended emissions in 0.2-5 MeV, which help us to better understand the properties of EM radiation from this BNS merger. Therefore the observation of Insight -HXMT constitutes an important chapter in the full context of multi-wavelength and multi-messenger observation of this historical GW event.