Now showing 1 - 10 of 91
  • Publication
    Open Access
    D(3He,p)4He and D(d,p)3H fusion in a small plasma focus operated in a deuterium helium-3 gas mixture
    A 3 kJ plasma focus was operated with a 3He-D2 gas mixture, with partial pressures in the ratio of 2:1, corresponding to an atomic number ratio of 1:1 for 3He and D atoms. The fusion reactions D(3He,p)4He and D(d,p)3H were measured simultaneously using CR-39 polymer nuclear track detectors placed inside a pinhole camera positioned on the forward plasma focus axis. A sandwich arrangement of two 1000 μm thick CR-39 detectors enabled the simultaneous registration of two groups of protons with approximate energies of 16 MeV and 3 MeV arising from the D(3He,p)4He and D(d,p)3H reactions, respectively. Radial track density distributions were obtained from each CR-39 detector and per-shot average distributions were calculated for the two groups of protons. It is found that the D(3He,p)4He and D(d,p)3H proton yields are of similar magnitude. Comparing the experimental distributions with results from a Monte Carlo simulation, it was deduced that the D(3He,p)4He fusion is concentrated close to the plasma focus pinch column, while the D(d,p)3H fusion occurs relatively far from the pinch. The relative absence of D(d,p)3H fusion in the pinch is one significant reason for concluding that the D(3He,p)4He fusion occurring in the plasma focus pinch is not thermonuclear in origin. It is argued that the bulk of the D(3He,p)4He fusion is due to energetic 3He2+ ions incident on a deuterium target. Possible explanations for differing spatial distributions of D(3He,p)4He and D(d,p)3H fusion in the plasma focus are discussed.
      390  125
  • Publication
    Open Access
    PMT-scintillator system set up for D-D neutron TOF measurements in INTI plasma focus device
    (2017)
    Damideh, Vahid
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    Saw, Sor Heoh
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    Sadighzadeh, Asghar
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    Jalil Ali
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    ; ;
    Lee, Sing
    This paper summarizes a Photomultiplier-Scintillator diagnostic system for use in our plasma focus experiments at the Center for Plasma Research INTI IU. The system features an anode-grounded high pulse linearity voltage divider and uses NE102A plastic scintillators. It has detected D-D neutrons in INTI plasma focus device with clear and high signal to noise ratio. Neutron TOF of 120 ns has been measured from the time difference between hard x-ray pulse peak and neutron peak time over a flight path of 2.6±0.01 m; giving energy of 2.5±0.1 MeV for these side-on neutrons.
      305  131
  • Publication
    Embargo
    Tailored heterostructured Ni3N-NiO nano-frameworks for boosting electrocatalytic oxygen evolution via surface-modulated plasma strategy
    (Springer, 2024)
    Ouyang, Bo
    ;
    Qin, Haonan
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    Sun, Chao
    ;
    Deng, Yilin
    ;
    Li, Ang
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    Zhu, Jipeng
    ;
    Kan, Erjun
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    The facile reconfiguration of phases plays a pivotal role in enhancing the electrocatalytic production of H2 through heterostructure formation. While chemical methods have been explored extensively for this purpose, plasma-based techniques offer a promising avenue for achieving heterostructured nano-frameworks. However, the conventional plasma approach introduces complexities, leading to a multi-step fabrication process and challenges in precisely controlling partial surface structure modulation due to the intricate interaction environment. In our pursuit of heterostructures with optimized oxygen evolution reaction (OER) behavior, we have designed a facile auxiliary insulator-confined plasma system to directly attain a Ni3N-NiO heterostructure (hNiNO). By meticulously controlling the surface heating process during plasma processing, such approach allows for the streamlined fabrication of hNiNO nano-frameworks. The resulting nano-framework exhibits outstanding catalytic performance, as evidenced by its overpotential of 320 mV at current densities of 10 mA cm-2, in an alkaline environment. This stands in stark contrast to the performance of sNiNO fabricated using the conventional plasma method. Operando plasma diagnostics, coupled with numerical simulations, further substantiate the influence of surface heating due to auxiliary insulator-confinement of the substrate on typical plasma parameters and the formation of the Ni3N-NiO nanostructure, highlighting the pivotal role of controlled surface temperature in creating a high-performance heterostructured electrocatalyst.
      11  9
  • Publication
    Open Access
    Repetitive operation of a dense plasma soft x-ray source for micromachining
    (2005-07)
    Wong, D.
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    ;
    Patran, Alin Constantin
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    Hassan, S. M.
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    Zhang, T.
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    ;
    Lee, Sing
    ;
    ;
    The NX2 device, a low energy plasma focus, at the Nanyang Technological University in Singapore, was used as a soft X-ray (SXR) source for micromachining. The gas used was neon which produced SXRs in a narrow spectral range of 0.9 - 1.6 keV. The SXR yield from repetitive operation of the NX2 device was monitored and measured using a cost effective multi-channel SXR spectrometric system. The system consists of filtered BPX65 PIN diodes, with the associated electronics --- an integrator, sample and peak holder, analogue switch, an A/D converter and a microcontroller. The system enables easy shot-to-shot statistical analysis under repetitive operation at adjustable preset trigger frequencies. A total of 4000 shots were fired at 0.5 Hz, using the same gas filling. The SXR production was at an average yield of 60 J/shot and a maximum single-shot yield of more than 100 J. The SXRs emitted by the NX2 device was used for contact micromachining, producing structures with an excellent aspect ratio of up to 20:1 on 25 μm SU-8 resist.
      133  127
  • Publication
    Metadata only
    Substrate orientation dependent characteristics of half-metallic and metallic superlattices [La0. 7Sr0. 3MnO3/LaNiO3] 10
    (2022)
    Das, Shaona
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    Tanguturi, Ranganadha Gopalarao
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    Ghosh, Sayandeep
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    Dokala, Ravi Kiran
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    Medwal, Rohit
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    Gupta, Surbhi
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    Yan, Zhuo
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    Qi, Yan
    ;
    ;
    Thota, Subhash
    We report a detailed study on the orientation dependent growth characteristics, electronic structure, transport, magnetic, and vibrational excitations in atomically flat interfaces of [La0.7Sr0.3MnO3/LaNiO3]10 superlattices (SLs) coherently grown on (001/011/111)-SrTiO3 substrates by the pulsed laser deposition technique. X-ray reflectometry confirms the periodic superlattice stacks from the Kiessig interference fringes and well-defined even interfaces between the nickelate and manganite layers. A complex local atomic environment across the interfaces was noticed, yet trivalent La, divalent Sr, and mixed valent Ni2+/3+ and Mn3+/4+ electronic states prevail at the core level with enhanced relative intensity ratio of the Mn ions in the superlattices grown on (111) oriented SrTiO3 substrates as compared to those grown on (001) and (011) oriented SrTiO3. The temperature (5≤T≤300K) dependence of electrical resistivity 𝜌(𝑇) analysis reveals 3D variable range hopping model [𝜌(T)=𝜌0exp(T0/T)(1/4)] with large magnitude of hopping energies (≥40 meV) for the SL-111 system associated with the high energy gap developed by the accumulation of disorderness in the individual constituents of polar layers. Moreover, all SL systems exhibit reduced ferromagnetic ordering temperatures (67≤T𝐶≤110K) with a low-temperature anomaly (11.4≤T∗≤22K) and a substantial enhancement in the effective exchange interaction (J𝑒𝑓𝑓∼3.52meV) having altered ground state-spin configuration S∼1/2 different from S=3/2 of La0.75Sr0.25MnO3. Nevertheless, the SL-011 system exhibits large anisotropy field H𝐾∼18kOe and cubic anisotropy constant K1∼9.3×103J/m3 in comparison to the other two orientations. The second order two-phonon interaction driven by the local polaronic distortion causes significant changes in the vibrational excitations of the investigated system. Nonetheless, most of the Raman modes follow the substrate-induced, highly oriented epitaxial growth pattern except for two modes 𝜈4 (326cm−1) and 𝜈8 (728cm−1), which slightly differ in the case of SL-111 superlattices.
    WOS© Citations 2Scopus© Citations 2  112
  • Publication
    Open Access
    Generalized brewster angle effect in thin-film optical absorbers and its application for graphene hydrogen sensing
    (2019)
    Sreekanth, Kandammathe Valiyaveedu
    ;
    Mohamed ElKabbash
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    Medwal, Rohit
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    Zhang, Jihua
    ;
    Letsou, Theodore
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    Strangi, Giuseppe
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    Hinczewski, Michael
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    ;
    Guo, Chunlei
    ;
    Ranjan Singh
    Generalized Brewster angle (GBA) is the incidence angle at polarization by reflection for p- or s-polarized light takes place. Realizing s-polarization Brewster effect requires a material with magnetic response which is challenging at optical frequencies since the magnetic response of materials at these frequencies is extremely weak. Here, we experimentally realize GBA effect in the visible using a thin-film absorber system consisting of a dielectric film on an absorbing substrate. Polarization by reflection is realized for both p- and s- polarized light at different angles of incidence and multiple wavelengths. We provide a theoretical framework for the generalized Brewster effect in thin-film light absorbers. We demonstrate hydrogen gas sensing using a single layer graphene film transferred on a thin-film absorber at the GBA with ~1 fg/mm2 aerial mass sensitivity. The ultrahigh sensitivity stems from the strong phase sensitivity near point-of-darkness, particularly at the GBA, and the strong light-matter interaction in planar nanocavities. These findings depart from the traditional domain of thin-films as mere interference optical coatings and highlight its many potential applications including gas sensing and biosensing.
    WOS© Citations 37Scopus© Citations 44  265  72
  • Publication
    Metadata only
    Rational design of hierarchically structured dual-encapsulated CoMoO4 nanosheets via in situ plasma tuning for efficient Li+ storage
    (2021)
    Ouyang, Bo
    ;
    Wang, Ying
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    Wang, Xi
    ;
    Zhang, Zheng
    ;
    Liu, Feng
    ;
    Fang, Zhi
    ;
    Kan, Erjun
    ;
    Engineering electrodes with desirable nanostructures are regarded as an urgent challenge to achieve enhanced electrical conductivity, stable structural integrity, and advanced performance for Li+ storage. Various approaches with processing complexity and multiple reactions have suffered serious limitation in industrialization. Here, we develop a facile carbon plasma (C-plasma) strategy combined with controlled reaction temperature to achieve in situ hierarchical metallic nanoparticles and graphene-encapsulated CoMoO4 nanosheets (hCCO). The nano-frameworks of Co3Mo and graphene shell are simultaneously modulated via simply controlling reaction temperature. The incorporation of nanoalloy component effectively enhances the conductivities of nanosheet, and uniformly coated graphene releases the structural stress caused by conversion reaction of metal oxides, maximizing the capacity utilization. The synergetic combination of these advantages enables the synthesized hCCO to deliver excellent electrochemical performances. Our C-plasma exhibits a great potential in tuning nano-architectures with high-performance Li+ storage behavior.
    WOS© Citations 2  193
  • Publication
    Open Access
    Optimization of neon soft X-ray emission from 200 J plasma focus device for application in soft X-ray lithography
    (2014)
    Shenbaga Manogara Pandian Kalaiselvi
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    Talebitaher, A.
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    ;
    The Fast Miniature Plasma Focus (FMPF) device is basically made up of coaxial electrodes with centrally placed anode and six cathode rods surrounding them concentrically. They are enclosed in a vacuum chamber, filled with low pressure operating gas. However, in our experiments, these cathode rods were removed to investigate the influence of them on neon soft X-ray (SXR) and hard X-ray (HXR) emission from the device. On removal of cathode rods, the cathode base plate serves as cathode and the plasma sheath is formed between the anode and the base plate of cathode. Neon was used as the operating gas for our experiments and the FMPF device used is of 235 J energy capacities. The experimental results showed that the FMPF device was able to focus better and the SXR emission efficiency was five times higher without cathode rods than with cathode rods. On the contrary, HXR emission did not vary with and without cathode rods. This observed phenomenon was further cross-checked through imaging of plasma dynamics, with and without cathode rods. FMPF device consists of 4 Pseudo Spark Gap (PSG) switches, which need to operate synchronously to deliver high voltage from capacitors to the anode. It was also seen that, the presence or absence of cathode rods also influence the synchronous operation of PSG switches. It also implies that this is one definite way to optimize the SXR emission from the FMPF device. This study reveals an important finding that, cathode rods play a vital role in the formation of plasma sheath with consequential influence on the radiation emission from plasma focus devices. Enhancement of the X-ray emission from this device is definitely a stepping stone in the realization of this device for industrial applications such as X-ray lithography for semiconductor industries.
      422  215
  • Publication
    Unknown
    Balanced NOx– and proton adsorption for efficient electrocatalytic NOx– to NH3 conversion
    (ACS Publications, 2023)
    Hu, Yue
    ;
    Liu, Jiawei
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    Lee, Carmen
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    Luo, Wenyu
    ;
    Dong, Jinfeng
    ;
    Liang, Zhishan
    ;
    Chen, Mengxin
    ;
    Hu, Erhai
    ;
    Zhang, Mingsheng
    ;
    Soo, Debbie Xiang Yun
    ;
    Zhu, Qiang
    ;
    Li, Fengkun
    ;
    ;
    Ng, Man-Fai
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    Zhong, Lixiang
    ;
    Han, Bo
    ;
    Geng, Dongsheng
    ;
    Yan, Qingyu
    Electrocatalytic nitrate (NO3–)/nitrite (NO2–) reduction reaction (eNOx–RR) to ammonia under ambient conditions presents a green and promising alternative to the Haber–Bosch process. Practically available NOx– sources, such as wastewater or plasma-enabled nitrogen oxidation reaction (p-NOR), typically have low NOx– concentrations. Hence, electrocatalyst engineering is important for practical eNOx–RR to obtain both high NH3 Faradaic efficiency (FE) and high yield rate. Herein, we designed balanced NOx– and proton adsorption by properly introducing Cu sites into the Fe/Fe2O3 electrocatalyst. During the eNOx–RR process, the H adsorption is balanced, and the good NOx– affinity is maintained. As a consequence, the designed Cu–Fe/Fe2O3 catalyst exhibits promising performance, with an average NH3 FE of ∼98% and an average NH3 yield rate of 15.66 mg h–1 cm–2 under the low NO3– concentration (32.3 mM) of typical industrial wastewater at an applied potential of −0.6 V versus reversible hydrogen electrode (RHE). With low-power direct current p-NOR generated NOx– (23.5 mM) in KOH electrolyte, the Cu–Fe/Fe2O3 catalyst achieves an FE of ∼99% and a yield rate of 15.1 mg h–1 cm–2 for NH3 production at −0.5 V (vs RHE). The performance achieved in this study exceeds industrialization targets for NH3 production by exploiting two available low-concentration NOx– sources.
      12
  • Publication
    Unknown
    Classification tasks using input driven nonlinear magnetization dynamics in spin Hall oscillator
    (2023)
    Mohan, John Rex
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    Mathew, Arun Jacob
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    Nishimura, Kazuma
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    Feng, Ruoyan
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    Medwal, Rohit
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    Gupta, Surbhi
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    ;
    Fukuma, Yasuhiro
    The inherent nonlinear magnetization dynamics in spintronic devices make them suitable candidates for neuromorphic hardware. Among spintronic devices, spin torque oscillators such as spin transfer torque oscillators and spin Hall oscillators have shown the capability to perform recognition tasks. In this paper, with the help of micromagnetic simulations, we model and demonstrate that the magnetization dynamics of a single spin Hall oscillator can be nonlinearly transformed by harnessing input pulse streams and can be utilized for classification tasks. The spin Hall oscillator utilizes the microwave spectral characteristics of its magnetization dynamics for processing a binary data input. The spectral change due to the nonlinear magnetization dynamics assists in real-time feature extraction and classification of 4-binary digit input patterns. The performance was tested for the classification of the standard MNIST handwritten digit data set and achieved an accuracy of 83.1% in a simple linear regression model. Our results suggest that modulating time-driven input data can generate diverse magnetization dynamics in the spin Hall oscillator that can be suitable for temporal or sequential information processing.
    WOS© Citations 2Scopus© Citations 2  42  59