Stuart Victor Springham

Stuart Victor Springham
National Institute of Education (NIE), Singapore | nie · Natural Sciences

About

173
Publications
15,067
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2,404
Citations
Citations since 2016
16 Research Items
893 Citations
2016201720182019202020212022050100150200
2016201720182019202020212022050100150200
2016201720182019202020212022050100150200
2016201720182019202020212022050100150200
Introduction
Skills and Expertise

Publications

Publications (173)
Conference Paper
Here we report the emission properties of low-dimensional perovskite materials: quantum dots and two-dimensional perovskites under high energy excitation from X-, gamma-ray, alpha particle, and thermal neutron, aimed towards fast-timed imaging and particle detection applications. 1. Introduction Scintillators are materials that down-convert high en...
Article
Full-text available
This paper is a sequel to the 1998 review paper “Scientific status of the Dense Plasma Focus” with 16 authors belonging to 16 nations, whose initiative led to the establishment of the International Center for Dense Magnetized Plasmas (ICDMP) in the year 2000. Its focus is on understanding the principal defining characteristic features of the plasma...
Article
Zirconium and beryllium fast-neutron activation detectors are used to investigate the fusion neutron emission from the NX3 Plasma Focus (PF) device operated in deuterium gas, with 7.2 kJ bank energy. Both Zr and Be activation cross-sections increase with energy, but with different trends, enabling an effective neutron energy Eneff to be inferred fr...
Article
Two-dimensional (2D) hybrid lead bromide perovskites are candidates for high light yield, fast scintillators. In this paper, we discuss the effect of commensurate Lithium doping (1:1 Li:Pb precursor ratio) on the scintillation properties of two previously reported high light yield 2D-perovskite crystals, PEA2PbBr4 and BA2PbBr4. The effect of Lithiu...
Article
Two-dimensional (2D) hybrid lead bromide perovskites are candidates for high light yield, fast scintillators. In this paper, we discuss the effect of commensurate Lithium(Li)-doping (1:1 Li:Pb precursor ratio) on the scintillation properties of two previously reported high light yield 2D-perovskite crystals, PEA2PbBr4 and BA2PbBr4. The effect of Li...
Conference Paper
Here we report the emission properties of perovskite quantum dots and two- dimensional perovskites under high energy excitation from X-, gamma-ray, alpha particle and thermal neutron, aimed towards fast-timed imaging and particle detection applications.
Article
Two-dimensional (2D) hybrid lead halide perovskites are potential candidates for high light yield scintillators as they have small bandgaps between 3 and 4 eV and large exciton-binding energy. Here we discuss the scintillation properties from a total of eleven organic/inorganic hybrid perovskite crystals with two already reported crystals, (PEA)2Pb...
Article
Full-text available
Two-dimensional lead halide perovskites have demonstrated their potential as high-performance scintillators for X-and gamma-ray detection, while also being low-cost. Here we adopt lithium chemical doping in two-dimensional phenethylammonium lead bromide (PEA)2PbBr4 perovskite crystals to improve the properties and add functionalities with other rad...
Chapter
This chapter describes some techniques and diagnostics for neutron and proton detection. It is more focused on DD fusion reaction products that comprise ~2.5 MeV neutron and ~3 MeV proton. Moreover, due to authors’ experience, it is tried to elaborate some experiments and results specifically on plasma focus device. For neutron detection, in additi...
Article
The deuterium-deuterium (DD) fusion neutron yield and anisotropy were measured on a shot-to-shot basis for the NX2 plasma focus (PF) device using two beryllium fast-neutron activation detectors at 0° and 90° to the PF axis. Measurements were performed for deuterium gas pressures in the range 6–16 mbar, and positive correlations between neutron yiel...
Conference Paper
The deuterium-deuterium (DD) fusion neutron yield and its anisotropy were measured for the NX2 plasma focus (PF) device by using two compact beryllium fast neutron activation detectors (designed and implemented by the authors) at 0° and 90° to the PF axis. The contribution to the fusion yield produced by the accelerated deuteron beam emitted from t...
Article
Full-text available
A sub-kilo-Joule plasma focus device (FMPF-3, 14 kV/235 J) was operated with deuterium–krypton admixtures (of 1, 2 and 5 % Kr by volume) to study the influence of admixture ratio on neutron yield (Y n). Experiments were performed for different insulator sleeve lengths and cathode geometries. The results reveal that for a carefully optimized electro...
Article
Laser shadowgraphy has been used to investigate the plasma sheath dynamics in a miniature plasma focus device (FMPF-3, 14 kV/235 J). The occurrence of magneto-hydro-dynamics instabilities are compared for pure deuterium versus deuterium-krypton admixture operation, over the range of gas pressures 2-12 mbar. A cathode-less geometry was also tested t...
Conference Paper
The PLANSEE double forged W samples were irradiated at different distances (5, 10, 15 and 20 cm) from the anode top for fixed 50 focus shot using a single shot 10 kJ NX3 plasma focus (PF) device with deuterium as the filling gas. The NX-3 PF device is dri ven by a 100 μF, 20 kJ modular capacitor bank which is capable of delivering peak current in t...
Conference Paper
The spatial distribution of DD fusion in a 1.6 kJ plasma focus (PF) device is investigated using the coded aperture imaging (CAI) technique, enabling single shot fusion images to be obtained. Simultaneously, two beryllium fast-neutron activation detectors are employed to measure neutron yield and anisotropy. The coded mask patterns used are based o...
Article
We classify all coded masks onto which cyclic difference sets can be wrapped periodically using a generalization of the Finger and Prince construction. In particular, we establish simple numerical criteria which determine whether any given mask can be wrapped periodically in this way and, for each mask which can, we provide explicit constructions w...
Article
Full-text available
This paper presents the synthesis of iron oxide nanoparticles using the atmospheric microplasma (AMP). The properties of iron oxide nanoparticles synthesized using AMP are compared with particles (i) formed in as-prepared solution and (ii) prepared using thermal decomposition method. Iron oxide nanoparticles prepared by all the 3 treatment methods...
Article
(ZnO)1−x (Co3O4)x≤0.05 thin-film series were deposited in vacuum Ar–O2 and N2 environment using the pulsed-laser deposition (PLD) technique. Bulk pellets were prepared by the solid-state reaction technique by mixing ZnO and Co3O4 powder and further utilized for deposition of thin films. XRD patterns of pellets exhibit homogeneous ZnCoO phase format...
Article
The present study is focused on the copper-doped ZnO system. Bulk copper-doped ZnO pellets were synthesized by a solid-state reaction technique and used as target material in pulsed laser deposition. Thin films were grown for different Cu doped pellets on sapphire substrates in vacuum (5×10−5 mbar). Thin films having (002) plane of ZnO showed diffe...
Conference Paper
form only given. The optical investigation of the plasma dynamics in breakdown, axial and radial phases of fast miniature plasma focus (FMPF-3) device under repetitive opeartion is being performed by means of laser shadowgraphy. Uniform parallel light beams are provided by using a monochrome (532 nm) Nd:YAG short pulsed laser (120 ps). A Phantom V2...
Article
We introduce the new concept of a row-spaced mask, where a number of blank rows are interposed between every pair of adjacent rows of holes of a conventional cyclic difference set based coded mask. At the cost of a small loss in signal-to-noise ratio, this can substantially reduce the number of holes required to image extended sources, at the same...
Patent
An activation detector for fast-neutrons has a yttrium target exposed to a neutron source. Fast-neutrons which have energy in excess of 1 MeV (above a threshold energy level) generate gamma rays from a nuclear reaction with the yttrium, the gamma rays having an energy level of 908.96 keV, and the resultant gamma rays are coupled to a scintillator w...
Article
This paper reports the results of characterization and optimization experiments carried out on a newly developed NX-3 dense plasma focus device (20 kJ at 20 kV, a quarter time period of ~ 3 μs, and 10 kJ/600 kA at 14 kV) at the Plasma Radiation Source Laboratory, NIE, Nanyang Technological University, Singapore. Initial experiments were conducted w...
Article
Full-text available
The effect of laser energy fluence on the onset and growth of Rayleigh-Taylor (RT) instabilities in laser induced Fe plasma is investigated using time-resolved fast gated imaging. The snow plow and shock wave models are fitted to the experimental results and used to estimate the ablation parameters and the density of gas atoms that interact with th...
Article
The Coded Aperture Imaging (CAI) technique has been applied with CR-39 nuclear track detectors to image alpha particle source spatial distributions. The experimental setup comprised: a 226Ra source of alpha particles, a laser-machined CAI mask, and CR-39 detectors, arranged inside a vacuum enclosure. Three different alpha particle source shapes wer...
Article
Full-text available
The coded aperture imaging (CAI) technique has been used to investigate the spatial distribution of DD fusion in a 1.6 kJ plasma focus (PF) device operated in, alternatively, pure deuterium or deuterium-krypton admixture. The coded mask pattern is based on a singer cyclic difference set with 25% open fraction and positioned close to 90 Degree-Sign...
Conference Paper
form only given. A comparative study of DD fusion in a 1.6 kJ plasma focus (PF) device operated with pure deuterium and a deuterium-krypton (D-Kr) admixture has been performed. Fast-neutron beryllium activation detectors positioned at 0° and 90° to the PF axis measured the time-integrated neutron yield and anisotropy. Typical fusion yields were in...
Article
The coded aperture imaging (CAI) technique has been applied to investigate the spatial distribution of DD fusion in a deuterium filled 1.6 kJ plasma focus (PF) device operated in its neutron-optimized regime. The coded mask has been fabricated in Havar alloy with 20 × 20 pixels and 57 square holes (14% open area) using a Singer-set Cyclic Differenc...
Article
We present a derivation of the signal-to-noise ratio (SNR) of a cyclic difference set (CDS) based coded mask which is simpler than that given in the literature, and which applies to any distribution of flux against the mask, not just Poisson statistics as is currently the case. We also present a derivation of a formula for the ratio of the SNR of a...
Article
A high performance high repetition rate plasma focus device with significant time averaged neutron yield and greater shot to shot reproducibility could be a highly valuable neutron source for Homeland Security applications. The single module fast miniature plasma focus ‘FMPF-2’ (2.4 μF, 56 ± 3 nH, 89 kA @ 14.0 kV, T/4~575 ns) was upgraded to four m...
Article
A compact fast neutron detector based on beryllium activation has been developed to perform accurate neutron fluence measurements on pulsed DD fusion sources. It is especially well suited to moderate repetition-rate (3×104cm−2, the statistical uncertainty in the fluence measurement is better than 1%. A small plasma focus device has been employed as...
Article
The structural and photoluminescence analyses were performed on un-doped and Mn doped ZnO thin films grown on Si (1 0 0) substrate by pulsed laser deposition (PLD) and annealed at different post-deposition temperatures (500–800 °C). X-ray diffraction (XRD), employed to study the structural properties, showed an improved crystallinity at elevated te...
Article
Titanium dioxide (TiO2 ) nano-clusters of average size 120 nm in the form of thin films were prepared using a repetitive dense plasma focus (DPF) device at room temperature. The films were deposited on silicon substrate at a distance of 25 cm from the anode top. A total of 100 DPF deposition shots were used to prepare the films, and the average thi...
Article
form only given. The research and development of compact repetitive miniature plasma focus devices, with stored energy from few tens to few hundred joules, is becoming increasingly important because of their potential applications as portable neutron source for explosive and contraband material detection. In this paper, we report the neutron emissi...
Article
form only given. Preliminary experimental results of a new, high energy, dense plasma focus device NX-3 that has recently been made operational at Plasma Radiation Source Lab, NIE, Nanyang Technological University, Singapore is reported. The NX-3 capacitor bank stores 20kJ energy in eight modules (of 2.5kJ each) and cumulatively delivers peak curre...
Article
form only given. The Coded Aperture Imaging (CAI) technique, which was originally developed for x-ray and γ-ray astronomy, has been applied to investigate the spatial distribution of DD fusion in a 1.6 kJ (1-3×108 n/shot) Plasma Focus device. The coded mask pattern is based on a Singer cyclic difference set with 341 open pixels in 91×15 array (25%...
Article
Pulsed laser deposition synthesized ZnO thin films, grown at 400°C substrate temperature in different oxygen gas pressures, were irradiated with 6 shots of pulsed nitrogen ions obtained from 2.94kJ dense plasma focus to achieve the nitrogen doping in ZnO. Structural, compositional and optical properties of as-deposited and nitrogen ion irradiated Z...
Article
Full-text available
Pulsed laser generated Fe plasma plumes have been studied near the target surface using time-resolved imaging. Afast gated intensified CCD camera is used to capture the images with a gate width of 2ns. The plasma plumes were generated using a Q-switched Nd-YAG laser at 1064nm with a fluence of ∼2kJ/cm2. The expansion studies were done up to a dista...
Article
Full-text available
The magnetic nanoparticles of Fe/FeCo/FePt, in the past, in a PLD system were grown by us using argon ambient gas pressure of about 0.1–75.0 mbar, as the ambient gas pressure can be used to tune the energy of the incident plasma plume species, the expansion volume, the growth duration, etc. which can control the particle size. In present paper, we...
Article
Study of expansion dynamics of pulsed-laser ablation plasmas from Fe and graphite targets is presented. A 532 nm Q-switched Nd:YAG laser with fluence of 30 J cm−2 is used to ablate the Fe and graphite targets in various Ar ambient gas pressures. Plasma ablation parameters for the two target materials are estimated using snow-plow and shock-wave mod...
Article
High-energy deuterons from a small plasma focus device (1.7 kJ) have been used for short-lived radioisotope production. For the 12C(d, n)13N reaction, 40 kBq of 13N was obtained by bombarding a graphite target at a 1-Hz shot repetition rate for 30 s. This could be increased to 10 MBq at a 16-Hz repetition rate. Plasma focus devices operating with h...
Article
Full-text available
A time resolved imaging study of pulsed laser ablated Fe and Al plasma plumes with specific interest in the splitting of plumes into the slow and fast moving components as they expand through the background argon gas at different pressures is reported. The material ablation was achieved using a Q-switched Nd:YAG (yttrium aluminum garnet) laser oper...
Article
The time-integrated imaging of pinched plasma column in the NX2 plasma focus device is performed using a general-purpose digital SLR camera with neutral density filters (ND 0.9). Although it is very simple, some useful information is obtained from the pinch phase of plasma focus device, and the images are compared with the neutron yield, electron,...
Article
Full-text available
Yttrium is presented as an absolute neutron detector for pulsed neutron sources. It has high sensitivity for detecting fast neutrons. Yttrium has the property of generating a monoenergetic secondary radiation in the form of a 909 keV gamma-ray caused by inelastic neutron interaction. It was calibrated numerically using MCNPX and does not need perio...
Article
A detailed and precise study of high energy deuteron beams from a plasma focus device shows that they follow a non-power law distribution, unlike most of the other works. This is in agreement with our previous studies using a direct and unambiguous diagnostic of the activation yield-ratio technique. It is possible that the E−n dependence effectivel...
Article
Full-text available
The Dense Plasma Focus (DPF) was independently discovered by J. Mather1 and N. V. Filippov2 in the early 60's. The DPF represents one of the most interesting and important applications of plasma physics to fusion and multi-radiation sources1-4. Nearly forty years of experiments have demonstrated the ability of (even table-top) DPF devices to produc...
Article
The Letter reports the first ever application of low energy miniature plasma focus device as a deposition facility for nanostructured thin films. We demonstrate successful utilization of a 120 J fast miniature plasma focus device as a novel facility for the deposition of magnetically soft FeCo thin films. Different gas types and the substrate mater...
Article
Full-text available
A direct synthesis of (001) oriented nanostructured CoPt thin films has been successfully achieved using a 880 J pulsed Dense Plasma Focus (DPF) device operating in a non-optimized focus mode with a low charging voltage of about 8 kV. The (001) oriented fit structured L10 phase nanostructured CoPt thin films have been synthesized directly in as-dep...
Article
In this paper, we report the experimental demonstration of enhancement in time averaged neutron yield by an order of magnitude, using the fast miniature plasma focus FMPF-2 in repetitive mode. The newly developed FMPF-2 device (2.4 µF, 56 nH, 13.8 kV, T/4 ~ 575 ns) operates up to 10 Hz in the quasi-continuous mode. Using pure deuterium as the fuell...
Article
In this work, the intense deuteron beam from a plasma focus device is investigated by the activation yield-ratio technique. It is shown that boron-carbide (B4C) and boron-nitride (BN) are complimentary targets for high energy deuteron beam studies. For deuteron spectra of the form dNd/dE∝E−n, when deuteron spectra decrease relatively gradually (n6)...
Article
The effects of the different number (1, 2 and 3) of H+ ion irradiation shots on pulsed laser deposited FePt thin films, using pulsed plasma focus device, are investigated. The FePt thin films were exposed to energetic H+ ions in a plasma focus device at a fixed distance of 4cm from the top of central electrode. It was deduced that single shot ion i...
Article
Full-text available
A repetitive NX2 dense plasma focus (DPF) device, operating at a low voltage of 8 kV with a stored energy of capacitor bank in the sub-kilojoule range (~880 J), was successfully used to deposit nanostructured magnetic CoPt thin films. The samples were synthesized at different filling hydrogen gas pressures and using different numbers of plasma focu...
Article
Full-text available
High energy neutrons, more than 2.45 MeV from deuteron-deuteron fusion reaction, have been measured in backward direction of plasma focus devices in many laboratories. However the experimental evidence for high energy deuterons responsible for such neutrons has not been reported so far. In this brief communication, backward high energy deuteron bea...
Article
In this Letter we report the effect of two different cathode structures – tubular and squirrel cage, on neutron output from a miniature plasma focus device. The squirrel cage cathode is typical of most DPF sources, with an outer, tubular envelope that serves as a vacuum housing, but does not carry current. The tubular cathode carries the return cur...
Article
A systematic investigation of expansion dynamics of plasma plume, generated by a Q-switched Nd–YAG laser at 532 nm with a fluence of ~30 J cm−2 on Fe target, was done for three different ambient pressures of 2 × 10−4, 2 and 20 mbar of Ar using fast gated intensified charge coupled device imaging. The experimental observations are then fitted with t...
Article
Summary form only given. A table top miniature plasma focus device FMPF-1 has been successfully used as a portable, pulsed hard X-ray source for fast radiography applications. It has 2.4 muF capacitor bank formed by 4 capacitors, operates at _14 kV charging voltage and delivers ~80 kA peak discharge current in a quarter time period of ~400 ns. The...
Article
Summary form only given. The Coded Aperture Imaging (CAI) technique is used to study the spatial distribution of fusion reactions in a 3 kJ Plasma Focus device operated in its neutron-optimized regime (11 kV and 14 mbar D2 gas). A coded mask (8times8 mm2, 20times20 pixel) was fabricated in a high strength alloy using micro- electro- discharge machi...
Article
Summary form only given. Successful deposition of nano-phase crystalline TiO2 thin films on polymeric substrates, polymethylmethacrylate (PMMA) and knitted polyethylene (PE) at room temperature was achieved using the dense plasma focus (DPF) device. Deposition was achieved using argon- oxygen gas mixture in the ratio of 9:1 after evacuating the cha...
Article
Summary form only given. Magnetic spectrometry using polymer nuclear track detectors is used for high-resolution measurement of the energy spectrum of deuterons (> 250 keV) emitted from the pinch-column of the NX2 plasma focus (PF). The spectrum is measured for single PF shots. A 25 mum pinhole images the deuteron source on the spectrometer. This p...
Article
Summary form only given. Energetic single shot H+ ion irradiation in dense plasma focus device (DPF) has been proved as an effective method for modification of pulsed laser deposition (PLD) synthesized FePt thin films. In our experiment, a UNU/ICTP dense plasma focus device was employed for pulsed ion irradiation with the charging voltage of 14 kV...
Article
In order to gain insight into the possible neutron production mechanism in sub-kilojoule miniature plasma foci, the anisotropy in neutron and hard x-ray emissions from a newly developed fast miniature plasma focus device (2.4 µF, 27 nH, T/4 ~ 400 ns, 12–15 kV, 170–270 J, total mass ~25 kg) is investigated. The system produces an average neutron yie...
Article
Full-text available
Published literature shows that the neutron yield of the plasma focus has been modeled in two papers using a thermonuclear mechanism. However, it is more widely held that plasma focus neutrons are produced mainly by non-thermalized mechanisms such as beam–target. Moreover these papers use several parameters which are adjusted for each machine until...
Article
Full-text available
The anisotropies of neutron and high energy deuteron emissions from the NX2 plasma focus device [ M. V. Roshan et al., Phys. Lett. A 373, 851 (2009) ] are studied. The nuclear activation of graphite targets is used to measure the fluences of high energy deuterons in the axial and radial directions. Two bismuth germanate scintillation detectors conn...
Article
High-energy deuterons from a small (1.7 kJ) plasma focus device were studied by nuclear activation of a boron-carbide target. The ratio of 10B(d,n)11C and 12C(d,n)13N yields indicates a deuteron spectrum decreasing rapidly between 400 keV and 1 MeV. This spectrum could take the form of dNd/dE∝E−n with n≈9.
Article
Full-text available
This work presents a novel method for determining bulk etch rate of CR-39 during prolonged etching by masking the surface with a ferrofluidic film held in position by magnetostatic forces. The CR-39 etching conditions were 6.25M NaOH solution for 24h at temperatures ranging from 50 to 80°C. After etching, the heights of the resulting un-etched plat...
Article
FePt nanoparticles, in the forms of nanoparticle agglomerates and floccules-like nanoparticle networks, can be synthesized by pulsed laser deposition (PLD) at different ambient gas pressures. Backward plume deposition (BPD), as special target–substrate geometry, can achieve higher uniformity in terms of agglomerate size and size distribution, compa...
Article
Full-text available
FePt thin films are exposed to pulsed energetic H+ ion beam from plasma focus. In irradiated films, the phase transition from the low Ku disordered face-centered-cubic structure to high Ku ordered face-centered-tetragonal phase was achieved at 400 °C with the order parameter S ranging from 0.73 to 0.83, high coercivity of about 5356 kA/m, high nega...
Article
High energy ions and energetic plasma irradiation of aluminum cathode inserts have been accomplished in nitrogen and argon filled plasma focus device. The Filippov-type plasma focus facility, Dena, with 288 μF capacitor bank and charging voltage of 25 kV (90 kJ maximum storage energy) was first optimized for strong ion beam generation for nitrogen...
Article
Magnetic spectrometry using polymer nuclear track detectors is used for high-resolution measurement of the energy spectrum of deuterons emitted from the pinch-column of the NX2 plasma focus (PF). The spectrum is measured for single PF shots. A 25 mum pinhole images the deuteron source on the spectrometer. Deuteron tracks are measured with an automa...
Article
Full-text available
FePt thin films are exposed to pulsed energetic H + ion beam from plasma focus. In irradiated films, the phase transition from the low K u disordered face-centered-cubic structure to high K u ordered face-centered-tetragonal phase was achieved at 400 °C with the order parameter S ranging from 0.73 to 0.83, high coercivity of about 5356 kA/m, high n...