Sing Lee

INTI International University | inti · Centre for Plasma Research

A palm top plasma focus (PF) device (100 J, 5 kV, 59 kA, ~1.5 kg) with tapered anode was demonstrated in a study earlier by (Rout et al., 2013). To simulate that device, we use the Lee code (RADPFV5.16). The computed current trace is fit to Rout’s measured current trace at 2.25 Torr deuterium ( D <sub xmlns:mml="http://www.w3.org/1998/Math/MathML"...

The fluence of a deuteron beam emitted from three dense plasma focus (DPF) devices, PF-1000, MPEF-12 kJ and PF-2.7 kJ, versus deuterium gas pressure was simulated and studied using the adapted Lee model code (RADPFV6.16FIB). The computed fluences were then compared to the reported measured values of these devices at certain distances from the pinch...

Newly obtained results on hot and dense deuterium and deuterium-neon plasma compression in a z-pinch electrical discharge configuration are presented. The investigated plasma was generated and compressed using 269 high-current discharges in a medium-sized (dense) plasma focus device. The experimental chamber of the device was filled with deuterium...

Numerical experiments using the Lee model code were carried out to compute the total D–D fusion neutron yield versus initial deuterium pressure for nine different plasma focus devices [PF50, AACS, PF400J, PF2.2, UNU-ICTP, PFZ200, PF24, PF78, Poseidon]. The computed data were compared with the published experimental results. In addition, the maximum...

This work is dealing with numerical experiments on D-D fusion neutron yield versus initial deuterium pressure for nine different plasma focus devices and compares them with the published experimental results. The scaling laws for the D-D fusion neutron production, in terms of storage energies E0 and pinch current Ipinch were derived. The scaling of...

In this study, the Lee code is used to compute the characteristics soft x-ray yield (Ysxr) production for nitrogen (N2), oxygen (O2), neon (Ne), and argon (Ar) and bremsstrahlung radiation for hydrogen (H2), deuterium (D2), and helium (He) with pressure variation in PF1000 of 2.5–2.6 MA for D2. In the calculation of characteristic soft x-ray, the c...

In this study, numerical experiments on ion beam features emitted from nine Dense Plasma Focus devices were carried out using the Lee model code (version RADPFV5.16FIB). A simulation (numerical experiment) and connected fitting procedure of a total discharge current waveform was presented on the example of the PF-24 device, and summary data concern...

It has been reported that over a range of 3–280 kJ, neutron-optimized deuterium plasma focus machines operate with a near constant speed factor S = 89 ± 8 kA cm⁻¹ per (torr)0.5. This near-constant value of S is consistent with a narrow range of peak axial speeds approximately 10 cm μs⁻¹ and peak radial speeds 20–30 cm μs⁻¹, resulting in focus pinch...

Existing conventional megajoule plasma focus machines with 2–3 MA are producing fusion neutron yields of several times 10 ¹¹ in deuterium operation, the fusion yields being predominantly beam-gas target. Increasing the current to 10 MA and using 50%-50% D-T mixture would scale the neutron yield towards 10 ¹⁶ D-T fusion neutrons. In this work, we de...

Argentina Nano Focus Machine is a small plasma focus machine used as an intense neutron source. To understand the working of its plasma dynamics, the Lee model code is used. The results obtained from the Lee code agree reasonably well with the experimental data in terms of the peak current, radial start time and the pinch duration. Additionally, th...

The article presents new results for plasma radiative compression in high-current discharges in the z-pinch configuration. The results are based on the 113 discharges performed in the plasma-focus PF-24 device operated with D2, Ar and (100%-x)D2+xAr mixtures, with Ar pressure fractions x ≈ 3–60% (mole fractions). The constant initial total pressure...

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...

The measured current wave shapes of PF1000 plasma focus discharged at 16 kV in deuterium in the pressure range 1.05 – 1.2 Torr are fitted to the computed current wave shapes using the Lee model code. Very good fit is achieved which suggests that the code is configured very well for the PF1000 for these shots. This is borne out by the computed neutr...

In this paper, the concept of producing a textured tool with a plasma focus machine is investigated for hardness and built-up-edge results. A textured cutting tool is required to have two important characteristics: texture and hardness. The purpose of the texture is to provide a suitable tool surface for a film of solid lubricant to anchor itself....

The effects of the atomic number of the fill gas on hard x-ray and ion beam emission from a 2.2 kJ plasma focus were studied. Hydrogen, Nitrogen and Argon gases were used in the experiment. The anode voltage and discharge current were measured to calculate plasma inductance and to study the pinching regime in the three gases. The results showed tha...

In this paper, a total of 5 Dense Plasma Focus (DPF) machines, working in argon gas which uses Mather type anode (7 energy range), were analysed using numerical experimentation (Lee Codes). Three important scaling laws relating the all line yield to the peak current, pinch current and energy input into the plasma were obtained. The scaling laws act...

Material hardening is a topic of much interest. In this paper, material hardening on AISI 1020 low carbon steel was done using INTI plasma focus (INTI PF) machine. It was found that the best distance for optimum hardening was to place the sample material 4 cm from the anode at a pressure of 1 Torr when the plasma machine is operating at 12 kV as it...

Atomic energy commission of syria (AECS) PF‐1, 2 devices were operated in N2 and Ar gases at pressures varied between 0.1–1 mbar and applied voltage of 15 kV on the capacitors bank with capacitance of 25 μF. The voltage, current, and current derivative curves were digitally recorded by Ohmic voltage divider and two Rogowskii coils; one with a big n...

Many experiments have been carried out on the (16.8 kJ, 17 kV) dense plasma focus PF-24 device operated with pure deuterium and deuterium-argon admixture. The main purpose of the work was to investigate the influence of the doping argon on the average total neutron yields experimentally and numerically. The 103 discharges (34 for D <sub xmlns:mml="...

This program was designed to introduce a plasma platform to examine the field programmable gate array (FPGA) of the link boards typically used at the CERN’s Large Hadron Collider (LHC). Pulsed plasma systems with accelerating gradient of 1 kV/ μm generate high-intensity, high-energy radiation beams. Single-event upset (SEU) is caused by radiation d...

Comparative study of fast focus mode (FFM)and slow focus mode (SFM)of INTI Plasma Focus device at 12 kV, based on Lee Model, are presented in this paper. Results of numerical experiments for D, Ne, and Ar gases at different pressure ranges show that as a rule-of-thumb, diameter-optimized SFM is considered to occur when fast plasma stream speed gene...

The modified version of Lee model code is used in numerical experiments for characterizing and optimizing neon soft X-ray yield (Ysxr) of the United Nations University/International Center for Theoretical Physics Plasma Focus Facility (UNU/ICTP PFF) device operated at 14 kV and 30 μF. In our present work, the neon yield Ysxr is improved with an opt...

This paper shows the correlation of the characteristic Ne soft X-ray (SXR) signal pulse with computed dynamics of the plasma focus using doped neon in Ne (97.5%)/Kr (2.5%) admixtures. The Lee model code is coupled with a specifically designed correlation excel template. The results show that typically, the characteristic Ne SXR pulse signal starts...

A dense plasma focus (DPF) machine, being a source of a powerful ion beam, can be useful in the modification of the surface properties of materials. Experimental investigations were carried out with a 3.3 kJ Mather-type DPF operating in nitrogen at a low chamber pressure with low carbon steel as the target material. It was found that the DPF ion be...

A capacitor bank discharges a current which is a sinusoidal function, lightly damped by unavoidable circuit resistance. When powering a plasma focus, the current waveform is further damped by the axial motion typically during the rising part of the current. The radial phase, with severe rate of change of inductance due to a rapidly collapsing curre...

The measured current traces of two low energy machines namely the AECS PF-2 and INTI PF are used for studying of the produced electron beam features using the modified Lee code (RADPFV5.15REB) at different conditions. The fitting procedures between measured and computed current traces are made for each point of pressure. In the case of AECS PF-2 wo...

The plasma focus (PF) emerged as a potential prospect to produce radionuclide, but the experimental data are not significant in favor of practical medical radioactivity. Empirical scaling grants a set of magnetic lens to enhance the nuclear activity. The experimental radioactivity of low-energy devices is in the range of kilobecquerel and rises to...

A series of experiments were carried out using the middle energy (dense) plasma focus device PF-24 with deuterium as a working gas under pressure in a range between 2 and 5 mbar for 17 kV of charging voltage. The relationship between these operating deuterium pressures in reference to the total neutron yield (Yn) was estimated. The 5-phase Lee code...

In this numerical experiment using Lee Model code, different parameters of the argon plasma such as pinch temperature, pinch density, peak and pinch current, tube voltage and pinch duration are explored. The radiation losses are explored by comparison of piston trajectories that predicts radiation cooling with a true picture of the pinch phase. In...

The measured current waveforms of PF1000 plasma focus operating in neon are first fitted to the computed currents using the Lee model for the pressures of 0.5 and 0.8 torr. The fitting fixes the model parameters. The code is then run to study and to optimize the soft X-ray yield from (~ 352 kJ) PF1000 device. The maximum characteristic soft X-ray (...

In this chapter we review numerical experiments using the Lee Model code. We describe the contributions made by this code in the past 30 years in the light of overall work on simulations already documented in the area of plasma focus. The plasma focus exhibits interesting phenomena ranging from electromagnetically driven dynamics to copious radiati...

In this work, damage results of four 12 mm × 12 mm × 5 mm PLANSEE double forged tungsten target samples exposed in INTI PF device at different distances from anode operating in the fast focus mode at 12 kV, 2.5 Torr deuterium are presented. SEM and EDX images and analysis show the extent of damage on the exposed tungsten surface. Micro-cracks up to...

Data from the 2002 Imperial College plasma focus (ICpf) are used to study the dynamics of axial and radial phase as functions of pressure. The speeds are found to deviate from the ideal constant current electromagnetic rule of v ~ P0-n, (where $n = 0.5$) with the modulus going below 0.5, due to the back-electromotive force varying the peak drive cu...

Measured current waveforms at different neon pressures from two different plasma focus (PF) devices, namely, NX2 and NX1 are used for analysis using the Lee code. The model parameters of mass (fm and fmr) and current (fc and fcr) in axial and radial phase, respectively, are obtained by fitting the computed current waveform to the measured current w...

The Lee model is extended to study and characterize the electron beams emitted from plasma-focus devices. It is then first applied to characterize the electron beams emitted from low and high-energy plasma focus operated with deuterium gas. The numerical experiments on NX2 device at 15 torr of deuterium give the following results: electron fluence...

In this work, the design and construction of a 50 Ω fast Faraday cup and its results in correlation with the Lee Model Code for fast ion beam and ion time of flightmeasurements for a Deuterium filled plasma focusdevice are presented. Fast ion beam properties such as ion flux, fluence, speed, and energy at 2–8 Torr Deuterium are studied. The minimum...

The indicative values of reduced Pease–Braginskii (P–B) currents are estimated for a nitrogen and oxygen plasma focus. The values of depletion times indicate that in N2 and O2 with estimated 3–4% of pinch energy radiating away over the duration of the pinch, we may expect some cooling effects leading to small reductions in radius ratio. In other ga...

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-Dneutrons in INTI plasma focusdevice with clear and high signal...

The dense plasma focus is blessed not only with copious multi-radiations ranging from electron and ion beams,x-rays both soft and hard, fusionneutronsD-D and D-T but also with the property of enhanced compression from radiative collapse leading to HED (high energy density) states. The Lee code has been used in extensive systematic numerical experim...

In this paper, we use Lee’s 5 phase model code to configure both the India Bhabha Atomic Research Center (BARC) Plasma focus machine operating in the pressure (P0) range from 1 Torr to 14 Torr as well as the Imperial College Plasma Focus Machine operating in the pressure (P0) range from 0.5 Torr to 6 Torr to compare the computational neutron yield...

The compression of the plasma focus pinch is a dynamic process, governed by the electrodynamics of pinch elongation and opposed by the negative rate of change of current dI/dt associated with the current dip. The compressibility of the plasma is influenced by the thermodynamics primarily the specific heat ratio; with greater compressibility as the...

The radial reflected shock phase begins when the inward shock front (IS) which is collisional hits the central axis and a reflected shock (RS) is produced that moves radially outward. This phase ends and the pinch phase begins when the outward moving RS front meets the inward moving magnetic piston. The Lee code approximates the RS phase by taking...

The influence of the power terms Joule heating and radiative losses on the pinch radius in plasma focus devices is studied. Numerical experiments were carried out using the Lee model on three plasma focus devices spanning a large range of storage energy (PF400, INTI PF, PF1000) with different filling gases (N, O, Ne, Ar, Kr, Xe). Six possible regim...

Computed results of beam ion current density are compared with the measured values for a range of pressures (0.13–1.33 mbar) and a range of distances (3–9 cm) downstream of the plasma compression commonly called the pinch in literature dealing with electromagnetically compressed dense plasmas. Partial agreement is found to an extent not reported be...

Numerical experiments have been systematically carried out using the modified Lee model code on PF-400J and other plasma focus devices operated with deuterium gas. The ion beam properties (ion beam energy, ion beam flux, ion beam fluence, beam ion number, ion beam current, power flow density, and damage factor) of the plasma focus have been studied...

Radiative collapse in the plasma focus (PF) pinch creates extreme high energy density (HED) in the laboratory. The Pease–Braginskii current is that current flowing in a hydrogen pinch which is just large enough for bremsstrahlung to balance Joule heating; this threshold value being 1.4 MA. For high-Z gases undergoing strong line-radiation the radia...

A large number of experimental investigations have been carried out on plasma focus devices especially at low energy level of several kJ or over 100 kJ. There are few machines operating in the middle energy range of 10–50 kJ, where the neutron yield typically in the order of 108–109 per shot. This paper reviews the optimisation process of two diffe...

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...

We looked at early days of UM Plasma- from its founding by Prof Thong Saw Pak, through its coming of age with first Physics PhD in Malaysia, achieving international status and recognition by ICTP as ICAC-UM. We looked at the Lee code, initiated as part of the 3 kJ UNU ICTP PFF (one of UM Plasma’s major science transfer packages) in the 80’s and ach...

Reduced Pease-Braginskii currents are estimated for a linear pinch in a range of gases, namely, D, He, Ne, Ar, Kr, and Xe. A characteristic depletion time is defined as the time it takes for the plasma focus (PF) pinch energy to be radiated away. This quantity is used as an indicator for expectation of radiative collapse. The depletion times in var...

Experimental studies of discharges in the plasma focus facility with neon filling and respective numerical simulations employing the radiative Lee code are reported. The pinch currents exceed the Pease-Braginskii current, which indicates that radiative losses are larger than heating and that contraction of the formed plasma should occur. Both of th...

Comparative study of Fast Focus Mode (FFM) and Slow Focus Mode (SFM) of INTI Plasma Focus device at 12 kV, based on Lee Model Code, are presented in this paper. Results of numerical experiments for D, Ne, and Ar in the pressure ranges of 1 to 14 Torr for D, 1 to 5.5 Torr for Ne, and 0.2 to 2.4 Torr for Ar show that as a rule-of-thumb, diameter-opti...

In this study, by using argon and nitrogen as the filling gases in a Mather type dense plasma focus device at different values of pressure and charging voltage, two different kinds of pinch regimes were observed for each of the gases. The physics of the pinch regimes could be explained by using the two versions of the Lee’s computational model whic...

A numerical analysis of a plasma focus device with step anode as the central electrode is carried out with Lee Model Code for a stepped central electrode configuration. The snowplow model is employed to describe the dynamics of current sheath between the electrodes using momentum conservation of the swept gases. The discharge current and the tube v...

In published literature, there has been scant data on radial trajectory of the plasma focus and no comparison of computed with measured radial trajectory. This paper provides the first such comparative study. We compute the trajectories of the inward-moving radial shock and magnetic piston of UMDPF1 plasma focus and compare these with measured data...

In plasma focus (PF), the thermodynamic parameters such as ion fraction α, effective ionic charge number Zeff, and effective specific heat ratio ɣ at different temperatures may be calculated by corona model (CM). In the Lee model code, the neon Zeff and ɣ are stored in subroutines using convenient tables and polynomials derived from the CM (we call...

Neutron yield is enhanced by reduction of the short-circuit plasma focus inductance , which in turn increases the pinch current . Numerical experiments are carried out to optimize the neutron production using the Lee model on small plasma focus devices (several kilojoules), such as UNU/ICTP PFF, NX2, and LDiana. The maximum neutron yield is obtaine...

The dense plasma focus is a copious source of multi-radiations with many potential new applications of special interest such as in advanced SXR lithography, materials synthesizing and testing, medical isotopes and imaging. This paper reviews the series of numerical experiments conducted using the Lee model code to obtain the scaling laws of the mul...

The soft X-ray yield versus pressure curves of NX1 and NX2 plasma focus machines have been measured and published for different pressures and electrode configurations. In this work, the numerical experiments are carried out, using Lee model code. The Lee model code is configured for each of these devices NX1 and NX2 by fitting computed total discha...

A large number of experimental investigations have been carried out on plasma focus devices especially at low energy level of several kJ or over 100 kJ. There are few machines operating in the middle energy range of 10–50 kJ, where the neutron yield typically in the order of 108–109 per shot. This paper reviews the optimisation process of two diffe...

As a radiation source the plasma focus PF is operated in time-matched regime TMR. Maximum energy is pumped into the compression, resulting in large inductive voltages Vmax, high temperatures and copious multi-radiations. In this Fast Focus Mode (FFM), targets in front of anode are subjected to strong bursts of fast ion beams (FIB), post-pinch fast...

Being an intense source of neutrons, soft x-rays, ion beams and fast plasma streams, the plasma focus promises applications such as fusion energy, advanced microlithography, materials synthesizing and testing, radiation diagnostics, medical isotopes and imaging. This paper reviews the scaling laws of neutrons, soft x-rays, ion beams and fast plasma...

A range of plasma focus machines from the 200 J FMPF3 through the 2 kJ NX2 to the 20 kJ NX3 are operated at the National Institute of Education in Singapore. The neutron yield Yn versus pressure P curves for these machines have been measured and published. We use the Lee code to compute these Yn versus P curve for each machine after fitting a compu...

Numerical experiments are carried out, using the Lee model code to compute the neutron yield Yn of PF1000 as a function of pressure. Computed results are compared with available published results of neutron yield. Relevant plasma focus properties such as peak discharge current Ipeak, pinch current Ipinch, pinch ion density ni and energy input into...

In this paper, we explain how we have fitted Lee‘s 5-phase and 6-phase model code to analyze the current waveforms of 6 small plasma focus machines (below 500Joules) working in deuterium gas medium. Using the information from the code fitted to these current waveforms, the scaling laws for these small- energy machines were obtained as follows Yn ~...

Ion beams emitted from the low-inductance kJ NX2 plasma focus have been numerically characterized and trends of these beams in various gases have been reported. In this paper, the ion beams from high-inductance kJ plasma focus machines AECS PF2 and INTI operated with various gases are studied. The obtained results show that the beam ions mean energ...

The code couples the electrical circuit with plasma focus (PF) dynamics, thermodynamics and radiation. It is energy-, charge- and mass-consistent and accounts for the effects of transit times of small disturbances and plasma self-absorption. It has been used in design and interpretation of Mather-type PF experiments and as a complementary facility...

The work on these numerical experiments was carried out using the Lee model code as a tool to compute the neon soft x-ray production in INTI plasma focus device. The computed pinch properties of plasma curves versus pressure are presented and discussed particularly in terms of the gross properties of the plasma focus including peak discharge curren...