Electron Density Measurements Research Articles

On the use of pulsed DC bias for etching high aspect ratio features

Inductively coupled plasmas (ICPs) containing Cl2 are widely used for plasma etching in the semiconductor industry. One common issue during plasma etching is aspect ratio dependent etching (ARDE), which is generally attributed to variation in the flux of etchant species to the bottom of features with different dimensions. Insufficient fluxes of neutral etchants to the bottom of high aspect ratio features can also result in sputtering, which tends to distort the feature profile. This article addresses two issues relevant to Cl2 ICP and plasma etching in these plasmas. First, a comprehensive set of diagnostics is used to validate a model for Cl2 ICP for gas pressure between 3 and 90 mTorr. The plasma diagnostics include microwave resonant hairpin probe-based measurements of electron density, photolysis-calibrated two-photon laser induced fluorescence measurement of Cl density, photo-detachment-based measurement of Cl− density, and laser diode absorption spectroscopy of argon metastable species to measure the gas temperature. Consistent with the experiments, the model shows that the electron density peaks near the center of the chamber at low gas pressure due to rapid diffusion. The electron density peak moves under the coils at higher pressures. Using the validated Cl2 model, we investigate ICPs with rectangular pulsed DC voltage for bias. It is shown that the Cl flux at the bottom of a trench decreases significantly with increasing aspect ratio of the trench. Neutral to ion flux ratio is therefore low at the bottom of higher aspect ratio trenches. The duty cycle of the pulsed bias waveform is found to be an effective means of increasing the neutral to energetic ion flux ratio, which should help with ARDE and sputter reduction.

Unexpected XPS Binding Energy Observations Further Highlighted by DFT Calculations of Ruthenocene-Containing [IrIII(ppy)2(RCOCHCORc)] Complexes: Cytotoxicity and Crystal Structure of [Ir(ppy)2(FcCOCHCORc)

The series of iridium(III) complexes, [Ir(ppy)2(RCOCHCOR')], with R = CH3 and R' = CH3 (1), Rc (2), and Fc (3), as well as R = Rc and R' = Rc (4) or Fc (5), and R = R' = Fc (6), ppy = 2-phenylpyridinyl, Fc = FeII(η5-C5H4)(η5-C5H5), and Rc = RuII(η5-C5H4)(η5-C5H5), has been investigated by single-crystal X-ray crystallography and X-ray photoelectron spectroscopy (XPS) supplemented by DFT calculations. Here, in the range of 3.74 ≤ ΣχR ≤ 4.68, for Ir 4f, Ru 3d and 3p and N 1s orbitals, binding energies unexpectedly decreased with increasing ΣχR (ΣχR = the sum of Gordy group electronegativities of the R groups on β-diketonato ligands = a measure of electron density on atoms), while in Fe 2p orbitals, XPS binding energy, as expected, increased with increasing ΣχR. Which trend direction prevails is a function of main quantum level, n = 1, 2, 3…, sub-quantum level (s, p, d, and f), initial state energies, and final state relaxation energies, and it may differ from compound series to compound series. Relations between DFT-calculated orbital energies and ΣχR followed opposite trend directions than binding energy/ΣχR trends. X-ray-induced decomposition of compounds was observed. The results confirmed good communication between molecular fragments. Lower binding energies of both the Ir 4f7/2 and N 1s photoelectron lines are associated with shorter Ir-N bond lengths. Cytotoxic tests showed that 1 (IC50 = 25.1 μM) and 3 (IC50 = 37.8 μM) are less cytotoxic against HeLa cells than cisplatin (IC50 = 1.1 μM), but more cytotoxic than the free β-diketone FcCOCH2COCH3 (IC50 = 66.6 μM).

Hot Uniaxial Pressing and Pressureless Sintering of AlCrCuFeMnNi Complex Concentrated Alloy-A Comparative Study.

External pressure is often applied during sintering to obtain materials with improved properties. For complex concentrated alloys (CCAs), this processing step is commonly performed in vacuum. However, this can promote the evaporation of elements and increase the oxide content, thereby degrading the properties of the alloy. In this study, we compared the microstructures and properties of AlCrCuFeMnNi CCA samples obtained by hot uniaxial pressing sintering (HPS) and pressureless sintering (PLS) using a helium atmosphere purified by an oxygen getter system. The powders were prepared from mixtures of CrFeMn, AlNi and Cu and sintered by HPS at 900 °C for 1 h with an applied pressure of 30 MPa and by PLS at 1050 °C for 1 h. The samples were characterised using X-ray diffraction, scanning and transmission electron microscopy, energy-dispersive X-ray spectroscopy, electron backscattering diffraction, density measurements and hardness tests. It was found that the oxygen getter system promoted oxygen partial pressure values at sintering temperatures similar to those of a mixture of 90% helium and 10% hydrogen. The HPS allowed us to obtain almost fully dense samples with a smaller average grain size and finer distribution of aluminium oxides than PLS. These differences increased the hardness of the samples sintered under pressure.

Utilization of D2 molecular band emission for electron density measurement

D2 molecular band emission observed at a wavelength range of λ∼557−643nm is utilized to measure electron density, ne, in D plasmas of the PISCES-A and PISCES-RF linear plasma devices. The D2 band is divided at λ=593nm to make an intensity ratio, D2L (∼557–593nm)/D2R (∼593–643nm), where D2L consists predominantly of the g3Σg+3dσ, h3Σg+3sσ, i3Πg3dπ, j3Δg3dδ→c3Πu2pπ transitions, while D2R mainly includes the d3Πu3pπ→a3Σg+2sσ Fulcher band emission. It is experimentally found that D2L/D2R depends strongly on ne with little Te dependence in ranges of ne∼(0.031−6.1)×1018 m−3 and Te∼2.3−13.9eV. This observed trend is consistent with collisional-radiative model calculations using Yacora on the Web.

Characterization of optical depth for laser produced plasma extreme ultraviolet source

This study investigates the emission mechanism of laser-produced plasma extreme ultraviolet source (LPP-EUV). In the experiment, the EUV radiation is generated by a 1064 nm laser interacting with slab Sn target. The EUV emission is characterized by EUV energy monitors and an EUV spectrometer. The dependency of CE on laser intensity and plasma relative optical depth is explored by a plasma emission-absorption layer model. The dependency is confirmed by an optical interferometry measurement of plasma electron density for the first time. Our work provides a method for characterizing and optimizing the optical depth of laser driven EUV source.

Speed and accuracy investigations of neural network algorithms for ionospheric modelling at an equatorial region

Neural networks are very efficient tools for modeling, including ionospheric modeling. The training algorithm is important for achieving the optimum performance of the trained network. This research is therefore meant to evaluate and compare the performances of ten neural network training algorithms based on their prediction accuracies, and the duration/times taken by each of the algorithms to establish the optimum result. The neural networks were trained using electron density measurements by Radio Occultation (RO) technique from the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites. Data for the period 2006 through 2021 was used. The networks were trained using about 2.9 million data points collected from the Kano region, Nigeria (5-degree rectangular region around geographic: 12.00° N, 8.59° E) after performing data quality control. The training algorithms considered in the work include: Bayesian Regularization (BR); Broyden-Fletcher-Goldfarb-Shanno Quasi-Newton (BFG); Conjugate Gradient with Powell/Beale (CGB); Fletcher-Reeves Conjugate Gradient (CGF); Gradient descent with momentum and adaptive learning rate (GDX); Levenberg Marquardt (LM); One Step Secant (OSS); Polak-Ribiére Conjugate Gradient (CGP); Resilient Backpropagation (RP); and Scaled Conjugate Gradient (SCG). The results showed that the BR and the LM algorithms gave the best performances in minimizing the errors of prediction (the mean RMSEs are respectively 112 and 114 ×103 electrons/cm3), but the RP algorithm, which came third in terms of accuracy, was significantly faster than both the LM and BR algorithms. The worst-performing algorithm in terms of accuracy was the GDX algorithm, although it was the fastest algorithm. The BFG algorithm was the worst-performing algorithm in terms of a combination of speed and accuracy. The developed neural network model was validated using ionosonde electron density measurements obtained from Ilorin, Nigeria (geographic: 8.5° N, 4.5° E; geomagnetic: 1.8° S). A comparison of the neural network, the NeQuick, and the IRI model predictions relative to the ionosonde measurements indicate that the neural network model was the best-performing model; the NN model predictions minimized the mean absolute errors (MAEs) in ∼44% of 399 ionosonde profiles investigated, the IRI model did so in ∼32%, and the NeQuick did so in ∼24%. The MAEs of the NeQuick however exhibited the best (least) variance. In overall, the NN model gave the least (best) mean of the MAEs (∼73 × 103 cm−3), compared to ∼82 × 103 cm−3 given by both the NeQuick and the IRI models, further supporting the idea that neural networks are excellent for present-day ionospheric modeling.

Measurement of electron and neutral particle densities using a two-color optical fiber interferometer.

A two-color homodyne Mach-Zehnder optical fiber interferometer is developed for the measurement of electron and neutral particle densities in a high-density capsule θ-pinch device. The interferometer leverages the disparate contributions of distinct particles to the refractive index across two discrete wavelengths of 1310 and 1550nm and incorporates the contributions of both electron and neutral particle densities to the phase shift in the plasma. The temporal evolutions of line-integrated electron and neutral argon densities are successfully measured by the interferometer. Comparing the electron density waveforms under various working gas pressures as well as the results obtained using the monochromatic and two-color measurements, it is inferred that the influence of neutral particle density can be neglected when measuring the electron density using a long-wavelength laser. Moreover, the maximum electron density is linearly correlated with the capacitor bank voltage for the θ-pinch device (5-9kV). Overall, the proposed interferometer is capable of simultaneously measuring the electron and neutral particle densities.

High precision phase difference calculation based on adaptive mixed-radix All-phase FFT for Tokamak plasma electron density measurement

In many Tokamak devices, laser interferometers, such as HCN, DCN, CO2, etc, are employed to measure the plasma electron density by calculating the phase difference between the reference signal and the detector signal. This paper proposes an adaptive All-phase fast Fourier transform (Ap-FFT) method in the electronic density of the plasma. And analyze the reasons why the multi-frequency measurement phase is inaccurate. The proposed method can reduce the accuracy of phase calculation by adjusting the conversion length and mixed-radix to reduce the spectrum leakage and grid effect. At the same time, the experimental data verifies the correctness of the calculation results of this method, and it shows that the measurement uncertainty of the method is 10% higher than the 1024-point Ap-FFT, and 15% higher than the 1024-point FFT. This method can be effectively applied to the measurement of the electronic density of an ionic plasma for plasma and provides a valuable reference for other phase detection systems and equipment.

First Thomson scattering results from AWAKE’s helicon plasma source

Abstract We present the first results of electron density and temperature measurements obtained from Thomson scattering at the helicon plasma source (HPS) for the AWAKE project. These measurements are compared to simulation results from a 1D power and particle balance model (PPM), confirming that the plasma can be fully sustained by collisional power dissipation. The variations in plasma parameters under different experimental conditions are evaluated in the PPM framework. We discuss current limitations of the model and propose possible improvements. Additionally, we suggest modifications to the existing HPS setup to enhance axial plasma homogeneity.

Bayesian-inverted laser Thomson scattering measurements indicate electrostatic erosion pathways in magnetically-shielded Hall effect thrusters

Magnetically shielded Hall effect thrusters suffer from pole erosion as their life-limiting mechanism. However, the dominant physical mechanism causing this erosion remains unclear, limiting the ability create designs that mitigate erosion and the predictive accuracy of simulations used to aid in design. This paper provides spatially resolved laser Thomson scattering measurements of electron temperature and density in the near field plume of a magnetically shielded Hall effect thruster, traversing the front pole region from the discharge channel centerline to the cathode centerline. The signals are inverted in a Bayesian framework, and the data are compared qualitatively and quantitatively to simulations of the same Hall effect thruster. Based on the electron momentum equation, electron pressure gradient is used as a proxy for the electron-predicted electrostatic potential gradient. To within the accuracy of this approximation, the electron pressure has a minimum immediately in front of the front pole. Hence, ions have an electrostatic potential avenue from the discharge region to the front pole, validating this mechanism of pole erosion.

Numerical investigation of vacuum ultra-violet emission in Ar/O2 inductively coupled plasmas

Abstract Controlling fluxes of vacuum ultraviolet (VUV) radiation is important in a number of industrial and biomedical applications of low pressure plasma sources because, depending on the process, VUV radiation may be desired, required to a certain degree, or unwanted. In this work, the emission of VUV radiation from O atoms is investigated in low-pressure Ar/O2 inductively coupled plasmas via numerical simulations. For this purpose, a self-consistent Ar/O2 plasma-chemical reaction scheme has been implemented in a zero dimensional plasma chemical kinetics model and is used to investigate VUV emission from excited O atoms (3s 5S 2 0 and 3s 3S 1 0 ) at 130 and 135 nm. The model is extensively compared with experimental measurements of absolute VUV emission intensities, electron densities and Ar excited state densities. In addition, oxygen VUV emission intensities are investigated as a function of pressure, Ar/O2 mixture, and power deposition and the dominant reaction pathways leading to oxygen VUV emission are identified and described. In general terms, absolute oxygen VUV emission intensities increase with power and oxygen fraction over the ranges investigated and peak emission intensities are found for pressures between 5–50 Pa. The emission is dominated by the 130 nm resonance line from the decay of the O(3s 3S 1 0 ) state to the ground state. Besides, at low pressure (0.3–1 Pa), the flux of oxygen VUV photons to surfaces is much lower than that of positive ions, whereas oxygen VUV fluxes dominate at higher pressure, ≳ 5–50 Pa depending on O2 fraction. Finally, oxygen atom fluxes to surfaces are, in general, larger than those of VUV photons for the parameter space investigated.

Perpendicular Electrical Conductivity in the Topside Ionosphere Derived from Swarm Measurements

The study of the physical properties of the topside ionosphere is fundamental to investigating the energy balance of the ionosphere and developing accurate models to predict relevant phenomena, which are often at the root of Space Weather effects in the near-Earth environment. One of the most important physical parameters characterising the ionospheric medium is electrical conductivity, which is crucial for the onset and amplification of ionospheric currents and for calculating the power density dissipated by such currents. We characterise, for the first time, electrical conductivity in the direction perpendicular to the geomagnetic field, namely Pedersen and Hall conductivities, in the topside ionosphere at an altitude of about 450 km. For this purpose, we use eight years of in situ simultaneous measurements of electron density, electron temperature and geomagnetic field strength acquired by the Swarm A satellite. We present global statistical maps of perpendicular electrical conductivity and study their variations depending on magnetic latitude and local time, seasons, and solar activity. Our findings indicate that the most prominent features of perpendicular electrical conductivity are located at low latitudes and are probably driven by the complex dynamics of the Equatorial Ionisation Anomaly. At higher latitudes, perpendicular conductivity is a few orders of magnitude lower than that at low latitudes. Nevertheless, conductivity features are modulated by solar activity and seasonal variations at all latitudes.

Investigating the Effects of Temperature, Azodicarbonamide, Boron Nitride, and Multilayer Film/Foam Coextrusion on the Properties of a Poly(Hydroxyalkanoate)/Poly(Lactic acid) Blend

Poly(hydroxyalkanoates) (PHAs) are emerging as sustainable materials in packaging and medical device industries. Nevertheless, the high cost and the need to improve the mechanical properties have limited their widespread use. Blending with other bio-based polymers, such as poly(lactic acid) (PLA), has been proposed in previous studies. This study investigates the effects of temperature, azodicarbonamide (AZ, foaming agent), boron nitride (BN, filler), and multilayer film/foam coextrusion on the properties of a blend containing an amorphous PHA and PLA. The effect of twin-screw micro-compounder temperature (185 °C & 205 °C) and BN concentrations of 1, 2, 3, 5, and 10 wt% (185 °C) on the properties of the PHA/PLA blend were investigated using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and tensile testing. Design of experiments (DoE) was used to find the optimal concentrations of AZ and BN (205 °C) using JMP® software. The response surface analysis predicted an optimal design based on the target response levels (modulus, tensile strength, strain at break, and toughness). This formulation was prepared and characterized using DSC, TGA, tensile, and melt flow index (MFI) measurements. Finally, this formulation was processed via film/foam coextrusion and examined using scanning electron microscopy (SEM) and density measurements. This study demonstrated that AZ and BN can be used to manipulate the mechanical properties and crystallinity of PHA/PLA blends, while reducing the overall material cost via density reduction (20–21% for the optimal formulation). Furthermore, reducing the concentration of AZ using the I-optimal design in this study could alleviate the toxicity concerns for food packaging.

Investigation of the global climatologic performance of ionospheric models utilizing in-situ Swarm satellite electron density measurements

The Swarm constellation is a triplet of satellites, flying, since their final configuration reached in April 2014, at altitudes of about 420 to 490 km (the lower pair) and about 500 to 530 km (the upper satellite). All the three satellites provide in-situ measurements of the plasma density in the topside ionosphere using Langmuir Probe sensors onboard the Electrical Field Instrument. The present study is a comprehensive investigation into the climatologic performance of three ionospheric models when compared to the Swarm satellite in-situ measurements. The models are the International Reference Ionosphere (IRI) model, a quick run ionospheric electron density model (NeQuick), and a 3-dimensional electron density model based on artificial neural network training of COSMIC (Constellation Observing System for Meteorology, Ionosphere, and Climate) satellites radio occultation measurements (3D-NN). The mean monthly quiet-time latitudinal profile of Swarm measurements was computed by binning the Swarm electron density measurements in 15-degree longitudes starting from longitude −180° in steps of 15° to 180°, and corresponding model predictions were obtained. The data used in the study covers the years 2014, 2016, 2019, and 2022, capturing various phases of the solar activity cycle. Results from the study show that modelled electron density predictions from all three climatologic models are fairly good representations of the Swarm satellite measurements, with some exceptions in which the models underestimate or overestimate the Swarm satellite values. The IRI model performed best at the northern hemisphere mid latitude, and it overestimated the Swarm measurements at altitudes of ∼ 450 km, especially at the southern hemisphere mid and high latitudes. The NeQuick performed best during the night times, and it overestimated the Swarm measurements, especially at the mid latitudes. The NeQuick was also observed to overestimate the Swarm measurements during the winter solstices at both hemispheres, which is June solstice in the southern hemisphere and December solstice in the northern hemisphere. Overall, the 3D-NN model most often performed better than the IRI model and the NeQuick, especially during the day times and during the high solar activity year (2014), but it underestimated the Swarm measurements, especially at the low and mid latitudes. For all categories explored in the study, the 3D-NN consistently performed better than the other two models. The NeQuick performed better than the IRI model at altitude of satellite B, while the IRI model performed slightly better than the NeQuick at altitude of satellites A and C. The NeQuick also performed better than the IRI model in the local time category, whereas the IRI model performed better than the NeQuick in categories of season, solar activity, and longitudinal sector.

Electron density measurement of Ar, N2, O2, and Ar mixtures (with N2 and O2) gas in inductively coupled plasma (ICP) using terahertz time domain spectroscopy

In this study, an inspection method using terahertz waves was proposed for the diagnosis of electron density using inductively coupled plasma (ICP). Plasma with low and high electron density for Ar, N2, O2, and Ar mixed (with N2 and O2) gases was generated by varying the RF power of the ICP and mass flow rate. Based on the theoretical analysis about propagation characteristics of the THz waves in Ar, N2, O2, and Ar mixed (with N2 and O2) gas plasma, the electron density of the ICP was measured according to RF power and mass flow rate. These results were verified using a Langmuir probe that can measure the electron density distribution.

Inter-ELM pedestal turbulence dynamics dependence on q95 and temperature gradient

A series of dedicated experiments from the DIII-D tokamak provide spatially and temporally resolved measurements of electron density and temperature, and multiscale and multichannel fluctuations over a wide range of conditions. Measurements of long wavelength density fluctuations in the type-I ELMing H-mode pedestals routinely reveal a coexistence of multiple instabilities that exhibit dramatic different dynamic behaviors as q95 and temperature gradients are varied, apparently responsible for limiting pedestal temperature profiles. Two distinct frequency bands of density fluctuations are modulated by an ELM cycle with frequency above 200 kHz propagating in the electron diamagnetic direction in the lab frame (electron mode) and below 200 kHz propagating in the ion diamagnetic direction (ion mode). The electron mode amplitude peaks near the electron temperature gradient region and increases with q95 which seems to be correlated with the increased χe at higher q95, similar to the characteristics expected for the micro-tearing mode (MTM). At higher q95, during the inter-ELM period, the ion mode decays at the later phase of the ELM cycle. Consistently, the poloidal correlation length of the ion mode is also found to reduce, which suggests the possible E × B flow shear suppression of the ion mode at the later phase of the ELM cycle as the Er well recovers. In contrast, the electron mode grows during the ELM cycle and reaches saturation at around 50%–60% of the ELM period. Linear gyrokinetic simulations find the MTMs to be the most unstable mode in the pedestal electron temperature gradient region. The higher q95 and lower magnetic shear destabilize the MTMs. These observations provide key insights into the underlying physics of multifield properties and a rich dataset of experimental ‘fingerprints’ that enable new tests of theoretical pedestal models and lead to the development of a predictive model for pedestal formation on the ITER and future burning plasma experiments.

A dataset of alternately located segments in protein crystal structures

Protein Data Bank (PDB) files list the relative spatial location of atoms in a protein structure as the final output of the process of fitting and refining to experimentally determined electron density measurements. Where experimental evidence exists for multiple conformations, atoms are modelled in alternate locations. Programs reading PDB files commonly ignore these alternate conformations by default leaving users oblivious to the presence of alternate conformations in the structures they analyze. This has led to underappreciation of their prevalence, under characterisation of their features and limited the accessibility to this high-resolution data representing structural ensembles. We have trawled PDB files to extract structural features of residues with alternately located atoms. The output includes the distance between alternate conformations and identifies the location of these segments within the protein chain and in proximity of all other atoms within a defined radius. This dataset should be of use in efforts to predict multiple structures from a single sequence and support studies investigating protein flexibility and the association with protein function.

First spectroscopic study of HFRC plasma

An advanced spectral diagnostic system was developed to measure the electron temperature (T e), electron density (N e), and ion temperature (T i) of the Huazhong University of Science and Technology field-reversed configuration plasma. The system consists of an optic fiber spectrometer with a wide spectral band and a 670 mm focal length high throughout Czerny–Turner monochromator equipped with both a 3600 g mm−1 grating and a 2400 g mm−1 grating to measure the line spectrum. Accompanying these components is an electron-multiplying charge-coupled device camera to capture spectral data. The relative intensity of the optical fiber spectrometer was calibrated using a standard luminance source, and the wavelength calibration of the spectrometer was accomplished using a Hg/Ar lamp. This diagnostic setup was configured to measure electron density based on the Stark effect of Hγ (n = 5 → n = 2; 434.04 nm). Doppler broadening of an O III (2s22p(2P0)3p → 2s22p(2P0)3s; 375.988 nm) emission line was measured and analyzed to obtain the ion temperature, and electron temperatures were estimated from the relative strength of Hβ (n = 4 → n = 2; 486.14 nm) (Dβ) and Hγ (Dγ) spectral lines when the electron density was obtained from Stark effect measurements. The initial experimental results indicate that the highest electron temperature of the formation region was approximately 8 eV, the electron density of the colliding-and-merging region was approaching 1020 m−3, and the ion temperature reached about 40 eV.

Design of a real-time frequency stabilization system for dual laser-based interferometer on EAST.

This study addresses the challenge of intermediate frequency (IF) instability in the far-infrared polarimeter/interferometer (POINT) of the Experimental Advanced Superconducting Tokamak (EAST) to ensure the accuracy and stability of electron density measurements. Sudden and extensive IF shifts of the lasers can cause instability and even measurement errors of the diagnostic system. This paper introduces a comprehensive solution for stabilizing IF fluctuations. First, analog IF is converted into digital form using an analog-to-digital converter, and the digitalized signal is processed by a digital signal system based on a ZYNQ processor. The exact value of the IF is obtained by acquiring the point of maximum amplitude through the fast Fourier transform method, while the ZYNQ processor loaded with a fuzzy control algorithm will precisely adjust the laser cavity length via piezoelectric ceramics, achieving frequency stabilization within a target range. Comparative analyses confirm the method's efficacy in managing sudden frequency shifts, maintaining stability within 850 ± 100kHz (a central frequency of 850kHz, fluctuating within a range of ±100kHz), with a control speed of 0.5s per action and robust against variations up to 270kHz. This efficient and rapid control mechanism fulfills the critical need for IF stabilization, ensuring the stability and precision of the POINT system in the EAST discharge experiments.

Development of ultra-short pulse reflectometry on the Experimental Advanced Superconducting Tokamak (EAST).

Microwave reflectometry is an invaluable diagnostic tool for measuring electron density profiles in large fusion devices. Density fluctuations near the plasma cutoff layer, particularly those that are time-varying on the timescale of the reflectometry measurement, can result in distortions in phase and/or amplitude of the reflected waveform, which present challenges to the accuracy of the reconstructed profile. The ultra-short pulse reflectometry (USPR) technique eliminates the time-varying issue in that reflectometry data are collected on a nanosecond timescale, essentially freezing the fluctuations in place. An X-mode dedicated 32-channel USPR system has been developed and installed on the EAST, covering the operation frequency range from 52 to 92GHz. This system enables high-resolution density profile measurements in the plasma pedestal and scrape-off layer, with resolutions reaching 5mm and 1 μs, respectively. Laboratory testing of the system performance has been conducted, demonstrating the potential of the USPR technique to provide accurate and high-temporal-resolution density profiles in challenging plasma environments.