Study of the Soft and Hard X-Ray Emitted by APF Plasma Focus Device in Different Pressures

In this paper, an investigation on the X-rays emitted in different pressures by APF plasma focus devices using filtered PIN-diodes and fast plastic scintillation detector is reported. The highest X-ray emission was observed in the pressure of 1.6 torr and the behavior of X-ray intensities registered by different filters versus applied pressure were seemed to be similar. The X-ray angular distribution was bimodal, peaked approximately at ±18°. The intensity of X-rays decreased abruptly along the central axis of the device where the cylindrical plasma pinch was formed.     

Neon Soft X-Ray Yield Optimization from PF-SY1 Plasma Focus Device

Based on the consideration of that for operation of the plasma focus in neon, a focus pinch compression temperature of 200–500 eV (2.3 × 10⁶–5 × 10⁶ K) is suitable for good yield of neon soft X-rays (SXR), numerical experiments have been investigated on the plasma focus device PF-SY1 using the latest version Lee model code. The Lee model code is firstly applied to characterize the PF-SY1 Plasma Focus. Keeping the bank parameters and operational voltage unchanged but systematically changing other parameters, numerical experiments were performed finding the optimum Y _sxr was 0.026 J. Thus we expect to increase the neon Y _sxr of PF-SY1 from its present typical operation; without changing the capacitor bank and the electrode configuration merely by changing the operating pressure. The Lee model code was also used to run numerical experiments on PF-SY1 with neon gas for optimizing soft X-ray yield with reducing L ₀, varying z ₀ and ‘a’. From these numerical experiments we expect to increase the neon Y _sxr of PF-SY1 with reducing L ₀, from the present 0.026 J at L ₀ = 1600 nH to maximum value of near 26 J at an achievable L ₀ = 10 nH.     

Angular Distribution of Argon Ions and X-Ray Emissions in the Apf Plasma Focus Device

Angular distribution of ion beam emission from an argon gas-filled plasma focus devices has been investigated using an array of five Faraday cups. The argon ion beam emission is found to be highly pressure-dependent and reaches its maximum at the pressure of 1 torr. The ions flux decreased as the working pressure increased; the maximum ion density at 1 torr was estimated to be around 9.24 × 10²⁴ ions/steradian. Also, the study on the angular distribution of X-rays has been carried out using TLD-100 dosimeters. The intensity of ions reduced significantly at angles higher than ±11° but the X-ray distribution was bimodal, peaked approximately at ±15°.     

Numerical Experiments on Neon Soft X-Ray Optimization of AECS-PF2 Plasma Focus Device

Numerical experiments have been investigated on modified AECS-PF2 with neon filling gas using the latest version of Lee model. The model was applied to characterize the 2.8 kJ plasma focus AECS-PF2, finding a neon soft X-ray yield (Y_sxr) of 0.04 J in its typical operation. By numerical experiments the optimum combination of pressure of 0.57 Torr, anode length of 9 cm and anode radius of 1.57 cm was found. The optimum Y_sxr found also to be 0.87 J. Thus we expect to increase the neon Y_sxr of AECS-PF2 22-fold from its present typical operation; without changing the capacitor bank, merely by changing the electrode configuration. The Lee model code was also used to run numerical experiments on AECS-PF2 with neon gas for optimizing soft X-ray yield with reducing L₀, varying z₀ and ‘a’. From these numerical experiments we expect to increase the neon Y_sxr of AECS-PF2 with reducing L₀, from the present 0.04 J at L₀ = 280 nH to maximum value of near 21 J at an achievable L₀ = 15 nH at the pressure 2.8 Torr.     

Characterization of the Soft X-Ray Emission from the APF Plasma Focus Device Operated in Neon

Experimental results related to soft X-ray (SXR) properties of Neon plasma on the APF plasma focus device is presented. The experiments were carried on over wide range of neon pressure and at voltages 11, 12 and 13 kV six filtered photo PIN diodes and pin-hole camera. For the charging voltages of 11–13 kV with 2.17–3.04 kJ stored energy, the optimum operating pressure in neon is found to be in the range of 3.5–5 torr. The behavior of SXR intensities was registered by different filters and found out that Al-Mylar 6 μm and Cu 10 μm has the highest and lowest amount of X-ray transmission, respectively.     

Comprehensive Study on Soft X-Ray Emission from Admixtures of Nitrogen and Neon Gases in the APF Plasma Focus Device

The present work is an investigation on the effect of working gas composition as well as applied voltage and operating pressure on the behavior of SXR emitted from the APF device. Three volumetric ratios(90:10), (75:25), and (50:50) of nitrogen:neon (N₂:Ne) admixture were used with operating conditions at applied voltages of 11, 12, and 13 kV and operating pressures of 1.5, 2, 2.5, 3, 3.5, 4, 4.5, and 5 torr. Using (N₂:Ne) gas mixture ratios of (90:10) and (75:25) and at applied voltage of 11 kV, the optimum pressure for maximum intensity of SXR was 3.5 torr. However, for the percentage of (50:50), it shifts to higher pressure of 4 torr. At higher applied voltages of 12 and 13 kV, the optimum pressures shift to higher values, 4 torr for both volumetric ratios (90:10) and (75:25), and 4.5 torr for the ratio of (50:50). It was found that the intensity of SXR increases with the increase of neon (Ne) percentage in the admixture of (N₂:Ne) and applied voltage. The highest intensity was for the volumetric ratio of (50:50) operating at the voltage of 13 kV. Our results illustrated that mixing neon (Ne) with nitrogen (N₂) as the working gas in the PF is a power source of SXR emission.     

Experimental Study of Hard X-ray Emission with Different Anode Tips in APF Plasma Focus Device

To investigate the effect of different anode tips on the hard X-ray (HXR) emission from APF plasma focus device (16 kV, 36 μf, and 115 nH) we considered two shapes of anode tips, i.e., flat or conic, with Cu, Al and W anode tip materials. The highest HXR intensity was observed with conic W anode insert and the lowest with flat Al anode insert. In comparison with the hollow anode tube the HXR signals obtained from flat and especially conic W inserts nearly tending to have the same intensity along the axis of the device. Therefore the shape and the material of the anode tip has significant effect on the production of HXR emissions. This study show that the employment of a convenient shape of anode tip results to more isotropic emission of HXR.     

Application of Plasma Focus Device in Fast Industrial Radiography

This paper deals with application of the plasma focus (PF) devices in fast industrial radiography. The results of radiography of a fan unit in both static and rotating states are presented. To do this, an X-ray video camera and the hard X-ray emission due to a PF device have been used. Moreover, the gray levels of the radiograph have been employed to find out the average effective X-ray energy in radiography of the rotating fan.     

The Effect of Applied Voltage and Operating Pressure on Emitted X-Ray from Nitrogen (N<Subscript>2</Subscript>) Gas in APF Plasma Focus Device

In the present work, the effect of applied voltage and operating pressure on behaviour of X-rays emitted from nitrogen gas (N₂) used in APF plasma focus facility is investigated. It was found that the optimum conditions for high emissions of SXR and HXR from the plasma focus (PF) are different. At four applied voltages of 10, 11, 12, and 13 kV, the optimum pressures for SXR and HXR emissions of nitrogen gas (N₂) were obtained. At lower voltages, 10, and 11 kV optimum pressure for SXR emission was 3.5 torr while for HXR emission was 2.5 torr. At higher voltages, 12, and 13 kV, the optimum pressures shift to higher values at 4 and 3 torr for SXR and HXR emissions, respectively. Among the applied voltages, the least intensity of both SXR and HXR was at voltage 10 kV and the most intensity was for 13 kV which confirm with increasing voltage, the intensity of X-ray emission increases. Also the results obtained by images of pin-hole camera were in compatible with the results of detected signals by different filtered Pin-diodes and Scintillation detector. Our results illustrate that the voltage and the pressure are effective parameters in X-ray emission from the PF.     

不同初始温度下氩等离子体演化过程研究

本文对不同初始温度下氩等离子体中主要粒子随时间的演化规律进行数值模拟,跟踪各主要成分粒子的浓度随时间的变化,得到放电后氩等离子体中主要带电粒子和中性粒子浓度随时间的变化规律。计算结果表明,氩等离子体化学反应达到平衡所需时间随初始温度升高逐渐减少,活性粒子Ar⁺浓度随时间不断增大,Ar^*、Ar^**浓度随时间先增大后减小,最终趋于稳定值达到平衡状态。     

Ion Beam Emission in a Low Energy Plasma Focus Device

The characteristics of the Ar ion beam generated in a low energy plasma focus device were investigated. A Mather-type PF device filled with argon gas driven by an 11 μF single capacitor bank was used. A Faraday cup, operating in the bias ion collector mode, is used to estimate the energy spectrum and ion flux along the PF axis. The results of the experiments show the dependence of the energy spectrum on the gas pressure and the anode shape.     

Spatial and Excitation Variations for Different Applied Voltages in an Atmospheric Neon Plasma Jet

A neon plasma jet was generated in air,driven by a 9 kHz sinusoidal power supply.The characteristics of the plasma plume and the optical spectra with plasma propagation for different applied voltages were investigated.By increasing the applied voltage,the plasma plume first increases and then retracts to become short and bulky.The shortened effect of Ne plasma plume(about 10 mm) for the further voltage increasing is more apparent than that of He(about3 mm) and Ar(about 1 mm).Emission intensity of the N_2(337 nm) increases with the applied voltage,gradually substituting the emission intensity of Ne(702 nm and 585 nm) as the noticeable radiation.At the nozzle opening,the Ne(702 nm) emission dominates,while the Ne(585 nm)emission is most noticeable around the tip of the plasma plume.The spatial distribution of the three spectral lines indicates that Ne(702 nm) emission decreases dramatically with plasma propagation while Ne(585 nm) and N_2(337 nm) emissions reach their maxima at the middle of the plasma plume.The results indicate that the Ne(702 nm) emission is much more sensitive to the average electron temperature and the density of the high-energy electrons,so it changes greatly at the tube nozzle and little at the tip region as the voltage increases.The population of high-energy electrons,the average electron temperature,the collision with air molecules and the Penning effect between Ne metastables and air molecules may explain their different variations with plasma propagating and voltage increasing.     

Experimental Observation of Hot Spots in a Filippov-Type Plasma Focus Device

In this paper we have presented the experimental results of hot spots observation in different working conditions in Filippov-type Plasma Focus Device “Dena” (90 kJ, 25 kV), analyzing of these results have shown that the working conditions have great influence on hot spots formation. In using the pure gases like D₂, Ar, Kr and Ne the formation of hot spots has been seen rarely, and it can be related to impurities like vapoured metal from the anode surface, also in using the light impurities hot spots were not formed, and only for the heavy impurities like Kr the formation of hot spots have been observed. The discharge voltage also plays an important role in hot spots formation, for voltages less than 16 kV, hot spots have not been observed. Also, using the conic insert anode leads to more and distinct hot spots than the case of flat one. The best results of hot spot observation in these experiments have been achieved by using a conic insert anode and D₂ + 1% Kr as working gas.     

A Study on Plasma Polymerization of Acrylic Acid Using APF Plasma Focus Device

The most conventional way for polymerization of acrylic acid on different substrates is using RF devices and introducing of other devices is under way. In this work we have a new study on formation of polymer Acrylic Acid using APF plasma focus device. The formation of plasma polymer acrylic acid is discussed using results obtained from attenuated total reflectance infrared spectroscopy (ATR). The results show that after 15 shots, nitrogen pulses performed polymerization on the specimens and the main peaks of ATR spectra assured poly acrylic acid formation on SBR substrate.     

Preparation of Titanium Carbide Thin Film Using Plasma Focus Device

In this work, we report titanium carbide (TiC) formation on the stainless steel—304 substrates by using a low energy (2 kJ) Mather-type plasma focus (PF) device. The argon–acetylene admixture (in 3:1 ratio) was used as the filling gas at a pressure of 1 torr. The thin films were deposited with different number of focus deposition shots (5, 15 and 25 shots), at 0° angular position with respect to the anode axis and at constant distance from the anode tip (10 cm). Deposited thin films have been investigated for their structure by X-Ray diffractometry (XRD) and surface morphology by scanning electron microscopy (SEM) and atomic force microscopy (AFM) analysis. The average size of crystallites (from XRD), crystalline growth of structures (from SEM), and size of grains and surface roughness (from AFM) were investigated, which increase by increasing the number of focus deposition shots.     

Prospects for 13N Production in a Small Plasma Focus Device

In this paper, the feasibility of ¹³N radioisotope production by a small plasma focus device for using in positron emission tomography (PET) has been studied. A large quantity of experimental data on the deuteron beam emission in dense plasma focuses are summarized and has been used in estimation of deuteron energy spectrum, intensity and angular distribution. The induced activity of ¹³N by ¹²C(d,n)¹³N reaction in an external solid target is calculated for different ‘m’ values (the power in energy distribution function of deuterons), and for a repetition rate plasma focus. A small plasma focus can produce ¹³N radionuclides in the order of 10 kBq in one shot, and it can be increased to few 10 MBq in a rep rate working mode with f = 10 Hz after 600 s operating time. Whereas a typical PET scan in myocardial blood perfusion assessment requires about 4 GBq radiopharmaceutical of ¹³N, it is concluded that a small plasma focus device, even with repetition frequency of f = 10 Hz can’t produce adequate ¹³N activity for this special PET imaging. Nonetheless, higher producible activities in higher energy PF devices and by endogenous production methods (i.e., nuclear reactions are induced inside the pinch itself) maybe result to introduction of an optimized repetitive high energy plasma focus as an alternative for cyclotrons in this special application.     

Numerical Experiments on Oxygen Plasma Focus: Scaling Laws of Soft X-Ray Yields

Numerical experiments have been investigated on UNU/ICTP PFF low energy plasma focus device with oxygen filling gas. In these numerical experiments, the temperature window of 119–260 eV has been used as a suitable temperature range for generating oxygen soft X-rays. The Lee model was applied to characterize the UNU/ICTP PFF plasma focus. The optimum soft X-ray yield (Y_sxr) was found to be 0.75 J, with the corresponding efficiency of about 0.03 % at pressure of 2.36 Torr and the end axial speed was v_a = 5 cm/μs. The practical optimum combination of p₀, z₀ and ‘a’ for oxygen Y_sxr was found to be 0.69 Torr, 4.8 cm and 2.366 cm respectively, with the outer radius b = 3.2 cm. This combination gives Y_sxr ~ 5 J, with the corresponding efficiency of about 0.16 %. Thus we expect to increase the oxygen Y_sxr of UNU/ICTP PFF, without changing the capacitor bank, merely by changing the electrode configuration and operating pressure. Scaling laws on oxygen soft X-ray yield, in terms of storage energies E₀, peak discharge current I_peak and focus pinch current I_pinch were found over the range from 1 kJ to 1 MJ. It was found that the oxygen soft X-ray yields scale well with $ {\text{Y}}_{\text{sxr}} = 2 \times 10^{ - 7} {\text{I}}_{\text{pinch}}^{3.45} $ and $ {\text{Y}}_{\text{sxr}} = 6 \times 10^{ - 7} {\text{I}}_{\text{peak}}^{ 2. 9 2} $ for the low inductance (L₀ = 30 nH) (where yields are in J and currents in kA). While the soft X-ray yield scaling laws in terms of storage energies were found to be as $ {\text{Y}}_{\text{sxr,O}} = 5.354 \times {\text{E}}_{0}^{1.12} $ (E₀ in kJ and Y_sxr in J) with the scaling showing gradual deterioration as E₀ rises over the range. The oxygen soft X-ray yield emitted from plasma focus is found to be about 8.7 kJ for storage energy of 1 MJ. The optimum efficiency for soft X-ray yield (1.1 %) is with capacitor bank energy of 120 kJ. This indicates that oxygen plasma focus is a good soft X-ray source when properly designed.     

Study of Dense Nitrogen Plasma Irradiation of Aluminum Targets by APF Plasma Focus Device

The nitridation of Al surfaces is obtained by irradiating nitrogen ions from APF device. The Vickers Micro-Hardness values are improved approximately three times for the nitrided samples comparing to the non-nitrided ones. The X-ray diffraction analysis is carried out in order to explore the phase changes in the near surface structure of the metals. The Nuclear Reaction Analysis shows the depth of the nitride composed on the metal surfaces clearly and quantitatively. The results of Scanning Electron Microscopy indicate changes in surface morphology which are the emergence of a smooth and uniform film scattered on the surface of the nitrided specimens.     

Simultaneity of Spark Gap Switch Firing in the Dense Plasma Focus Device

To gain insight into the synchronization, simultaneity, and switching behavior of the individual switch, two TIA-525 Optical/Electrical converters have been recently introduced to DPF experiments at Lawrenceville Plasma Physics (LPP). These electronic devices, attached to two spark gap switches through optical fibers, detect light sampled from the switch firing and convert it to amplified voltage signals. We observed that in terms of simultaneity and synchronization, the firing behavior and quality of the pair of switches monitored are not the same. Some switches, among the twelve that are being used, fired at the trigger voltage within few tens of ns while the others fired much later (after ~1–2 μs) and are triggered at or after the pinch voltage rise. The results from the present work show evidence of pinch voltage triggering the switches. Since the pinch voltage is over three times the voltage of the capacitors, this voltage triggers those capacitors that do not fire during the regular high voltage trigger pulse. This, we suggest, could affect the efficiency of the device as it simply drains the reserved energy in the system. We present results of an empirical study of spark gap switch firing as well as the total current that is followed using the Rogowski coil.