Determination Of Plasma Parameters Research Articles

177Lu-EC0800 Combined with the Antifolate Pemetrexed: Preclinical Pilot Study of Folate Receptor Targeted Radionuclide Tumor Therapy

Targeted radionuclide therapy has shown impressive results for the palliative treatment of several types of cancer diseases. The folate receptor has been identified as specifically associated with a variety of frequent tumor types. Therefore, it is an attractive target for the development of new radionuclide therapies using folate-based radioconjugates. Previously, we found that pemetrexed (PMX) has a favorable effect in reducing undesired renal uptake of radiofolates. Moreover, PMX also acts as a chemotherapeutic and radiosensitizing agent on tumors. Thus, the aim of our study was to investigate the combined application of PMX and the therapeutic radiofolate (177)Lu-EC0800. Determination of the combination index (CI) revealed a synergistic inhibitory effect of (177)Lu-EC0800 and PMX on the viability of folate receptor-positive cervical (KB) and ovarian (IGROV-1) cancer cells in vitro (CI < 0.8). In an in vivo study, tumor-bearing mice were treated with (177)Lu-EC0800 (20 MBq) and a subtherapeutic (0.4 mg) or therapeutic amount (1.6 mg) of PMX. Application of (177)Lu-EC0800 with PMXther resulted in a two- to four-fold enhanced tumor growth delay and a prolonged survival of KB and IGROV-1 tumor-bearing mice, as compared to the combination with PMXsubther or untreated control mice. PMXsubther protected the kidneys from undesired side effects of (177)Lu-EC0800 (20 MBq) by reducing the absorbed radiation dose. Intact kidney function was shown by determination of plasma parameters and quantitative single-photon emission computed tomography using (99m)Tc-DMSA. Our results confirmed the anticipated dual role of PMX. Its unique features resulted in an improved antitumor effect of folate-based radionuclide therapy and prevented undesired radio-nephrotoxicity.

Direct in vitro and in vivo comparison of 161Tb and 177Lu using a tumour-targeting folate conjugate

The radiolanthanide (161)Tb (T 1/2 = 6.90 days, Eβ(-) av = 154 keV) was recently proposed as a potential alternative to (177)Lu (T 1/2 = 6.71 days, Eβ(-) av = 134 keV) due to similar physical decay characteristics but additional conversion and Auger electrons that may enhance the therapeutic efficacy. The goal of this study was to compare (161)Tb and (177)Lu in vitro and in vivo using a tumour-targeted DOTA-folate conjugate (cm09). (161)Tb-cm09 and (177)Lu-cm09 were tested in vitro on folate receptor (FR)-positive KB and IGROV-1 cancer cells using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) viability assay. In vivo (161)Tb-cm09 and (177)Lu-cm09 (10 MBq, 0.5 nmol) were investigated in two different tumour mouse models with regard to the biodistribution, the possibility for single photon emission computed tomography (SPECT) imaging and the antitumour efficacy. Potentially undesired side effects were monitored over 6 months by determination of plasma parameters and examination of kidney function with quantitative SPECT using (99m)Tc-dimercaptosuccinic acid (DMSA). To obtain half-maximal inhibition of tumour cell viability a 4.5-fold (KB) and 1.7-fold (IGROV-1) lower radioactivity concentration was required for (161)Tb-cm09 (IC50 ~0.014 MBq/ml and ~2.53 MBq/ml) compared to (177)Lu-cm09 (IC50 ~0.063 MBq/ml and ~4.52 MBq/ml). SPECT imaging visualized tumours of mice with both radioconjugates. However, in therapy studies (161)Tb-cm09 reduced tumour growth more efficiently than (177)Lu-cm09. These findings were in line with the higher absorbed tumour dose for (161)Tb-cm09 (3.3 Gy/MBq) compared to (177)Lu-cm09 (2.4 Gy/MBq). None of the monitored parameters indicated signs of impaired kidney function over the whole time period of investigation after injection of the radiofolates. Compared to (177)Lu-cm09 we demonstrated equal imaging features for (161)Tb-cm09 but an increased therapeutic efficacy for (161)Tb-cm09 in both tumour cell lines in vitro and in vivo. Further preclinical studies using other tumour-targeting radioconjugates are clearly necessary to draw final conclusions about the future clinical perspectives of (161)Tb.

PLASMA CHARACTERISTICS IN SQUARE PULSE ARC DISCHARGE OF PLASMA CATHODE ELECTRON SOURCE DEVICE

Plasma parameters in Plasma Cathode Electron Source Device (PCESD) are very important things because they will determine the eficiency of its electron extraction. Square pulse mode of PCESD’s arc discharge plasma current can be obtained by using Pulse Forming Network (PFN) circuits which is called Arc Discharge Power Supply (ADPS). The square pulse mode is necessity to simplify in electron irradiation dose calculation. ADPS is connected with Hollow Anode Chamber (HAC) which is placed inside of PCESD to produce arc discharge plasma. The value of arc discharge plasma current is the main key to determine plasma parameters that can be measured by using Rogowski coil. The value of the arc discharge plasma current is IADPS = 206.30 A with pulse width  = 80 μs. Whereas the plasma parameters values inside of the HAC are: the electron plasma density ne = (16.85  1019) m-3, electron plasma temperature Te = 2.609 eV, electron plasma frequency fe = 116.74 GHz, and Debye length λD = 9.958 µm respectively.

STUDY OF EFFECTS OF DIFFERENT REACTIONS ON PLASMA PARAMETERS IN D–T MAGNETIC CONFINEMENT FUSION

The consideration of the three main nuclear reactions of the hydrogen isotopes ( D(D, n) 3 He , D(D, p)T and T(D, n) 4 He ) only leads to wrong results for determination of plasma parameters in magnetic confinement fusion reactors. The nuclear reaction 3 He(D, p) 4 He influences the amount of produced tritium since it makes an important contribution to the charged particle energy deposition and to the temperatures. In this paper, we have considered different nuclear reactions of Deuterium–Tritium (D–T) fusion in tokamak reactor. This study has been carried out on the base of the particle and power balance equations in a zero-dimensional model then plasma parameters have been calculated. Finally, the obtained results have been compared with the theoretical results reported by other researchers.

Characterization of transient discharges under atmospheric-pressure conditions applying nitrogen photoemission and current measurements

The plasma parameters such as electron distribution function and electron density of three atmospheric-pressure transient discharges namely filamentary and homogeneous dielectric barrier discharges in air, and the spark discharge of an argon plasma coagulation (APC) system are determined. A combination of numerical simulation as well as diagnostic methods including current measurement and optical emission spectroscopy (OES) based on nitrogen emissions is used. The applied methods supplement each other and resolve problems, which arise when these methods are used individually. Nitrogen is used as a sensor gas and is admixed in low amount to argon for characterizing the APC discharge. Both direct and stepwise electron-impact excitation of nitrogen emissions are included in the plasma-chemical model applied for characterization of these transient discharges using OES where ambiguity arises in the determination of plasma parameters under specific discharge conditions. It is shown that the measured current solves this problem by providing additional information useful for the determination of discharge-specific plasma parameters.

Characterization of an asymmetric parallel plate radio-frequency discharge using a retarding field energy analyzer

A retarding field energy analyzer is used to characterize an asymmetric, 13.56 MHz driven, capacitively coupled, parallel plate discharge operated at low pressure. The characterization is carried out in argon discharges at 10 and 20 mTorr where the sheaths are assumed to be collisionless. The analyzer is set in the powered electrode where the impacting ion and electron energy distributions are measured for a range of discharge powers. A circuit model of the discharge is used to infer important electrical parameters from the measured energy distributions, including electrode excitation voltages, plasma potential and sheath potentials. Analytical models of the ion energy distribution in a radio-frequency sheath are used to determine plasma parameters such as sheath width, ion transit time, electron temperature and ion flux. A radio-frequency compensated Langmuir probe is used for comparison with the retarding field analyzer measurements.

Spectroscopic characterization of an atmospheric pressure μ-jet plasma source

A new method for determination of plasma parameters under atmospheric pressure conditions is formulated and applied for characterization of a radio-frequency μ-jet plasma source using He/O2 mixture. By applying absolutely calibrated optical emission spectroscopy and numerical simulation, the gas temperature in the active plasma region and plasma parameters (electron density and electron distribution function) are determined. The steady-state concentrations of different species such as oxygen atom and ozone in the plasma channel and in the effluent of the plasma source are calculated using measured plasma parameters and gas temperature. On the other hand, spatial distribution of steady-state densities of these species are measured using emission and absorption spectroscopy. A comparison of the results thus obtained and the validation of the new method against two-photon absorption laser-induced fluorescence spectroscopy measurements are discussed. In addition, the influence of the surface processes and gas flow regime on the loss of the active species in the plasma source are discussed.

Application of electrostatic Langmuir probe to atmospheric arc plasmas producing nanostructures

The temporal evolution of a high pressure He arc producing nanotubes was considered and the Langmuir probe technique was applied for plasma parameter measurements. Two modes of arc were observed: cathodic arc where discharge is supported by erosion of cathode material and anodic arc which is supported by ablation of the anode packed with carbon and metallic catalysts in which carbon nanotubes are synthesized. Voltage-current (V-I) characteristics of single probes were measured and unusually low ratio of saturation current on positively biased probe to that on negatively biased of about 1–4 was observed. This effect was explained by increase of measured current at the negatively biased probe above the level of ion saturation current due to secondary electron emission from the probe surface. Since utilization of standard collisionless approach to determine plasma parameters from the measured V-I characteristic is not correct, the electron saturation current was used to estimate the plasma density.

Diagnostics of plasma produced by femtosecond laser pulse impact upon a target with an internal nanostructure

X-ray diagnostics of the interaction of femtosecond laser pulses with intensities of 1016–1018 W/cm2 with CO2 clusters and frozen nanosize water particles is carried out. The stage of cluster expansion and the formation of a plasma channel, which governs the parameters of the formed X-ray radiation source and accelerated ion flows, is studied. The measurements are based on recording spatially resolved X-ray spectra of H- and He-like oxygen ions. Utilization of Rydberg transitions for spectra diagnostics makes it possible to determine plasma parameters on a time scale of t ∼ 10 ps after the beginning of a femtosecond pulse. The role of the rear edge of the laser pulse in sustaining the plasma temperature at a level of ∼100 eV in the stage of a nonadiabatic cluster expansion is shown. The analysis of the profiles and relative intensities of spectral lines allows one to determine the temperature and density of plasma electrons and distinguish the populations of “thermal” ions and ions that are accelerated up to energies of a few tens of kiloelectronvolts. It is shown that the use of solid clusters made of frozen nanoscale water droplets as targets leads to a substantial increase in the number of fast He-like ions. In this case, however, the efficiency of acceleration of H-like ions does not increase, because the time of their ionization in plasma exceeds the time of cluster expansion.

Effects of Astragalus Polysaccharides, Achyranthes bidentata Polysaccharides, and Acantbepanax senticosus Saponin on the Performance and Immunity in Weaned Pigs

Two trials were conducted to study the effects of two Chinese herbal polysaccharides, Astragalus polysaccharides (APS) and Achyranthes bidentata polysaccharides (ABPS), and one Chinese herbal saponin, Acantbepanax senticosus saponin (ASS), on the immunity and growth performance of weaned pigs. Experiment 1 was a 14-day growth assay, in which 32 weaned pigs were randomly allocated to one of four dietary treatments: i) 0.05% talcum powder control; ii) 0.05% APS; iii) 0.05% mixture of APS and ASS in a 1:1 ratio by weight; and iv) 0.05% mixture of APS, ASS, and ABPS in a ratio of 1:1:1 by weight. Blood samples were collected on day 14 to determine plasma parameters. Feed intake, body weight gain, and feed efficiency were also determined. Experiment 2 was a 21-day immunity assay, in which 16 weaned pigs were randomly allotted to one of two dietary treatments: i) 0.05% talcum powder control; and ii) 0.05% mixture of APS and ASS in a 1:1 ratio by weight. On day 21, pigs were challenged with lipopolysaccharide (LPS) and 3 h later blood samples were collected and analyzed for lymphocyte proliferation as well as interleukin 6 (IL-6), insulin-like growth factor 1 (IGF-1), growth hormone (GH), and cortisol levels. In Experiment 1, feeding Chinese herbal polysaccharides and saponin increased growth performance of the pigs. The effects of the mixture of APS and ASS were especially notable, as there was a significant improvement in growth performance compared with the control (p 0.05). In Experiment 2, Chinese herbal polysaccharides and saponin showed immunostimulating effects. The level of cortisol, GH, and IGF-I were significantly increased (p>0.05), and the level of IL-6 showed a significant decrease (p<0.05) in the APS and ASS treatment after the LPS challenge. The mixture of APS and ASS could stimulate the blood lymphocyte proliferation significantly whether the LPS was injected or not (p<0.05). These results show that Chinese herbal extracts can improve growth performance and stimulate immunity of weaned pigs. A mixture of APS and ASS, compared with APS alone, could be a new kind of immunostimulant for weaned pigs, which could result in greater positive effects on their growth performance and immunity.

Application of a collisional radiative model to atomic hydrogen for diagnostic purposes

Optical emission spectroscopy is one of the standard diagnostic methods to determine plasma parameters. In hydrogen plasmas often the intensity of the Balmer lines is recorded. To analyze such measurements population models for the hydrogen atom are needed. The flexible package Yacora is used to construct a new collisional radiative model for low pressure, low temperature hydrogen plasmas. This model includes six possible excitation channels: effective excitation of H, recombination of H + , dissociative excitation of H 2 , dissociative recombination of H 2 + , dissociative recombination of H 3 + and mutual neutralization of H - and H x + . The model is applied to a uniform ECR plasma with high dissociation degree and low ionization degree, i.e. electron collision excitation from H is the dominant excitation channel. The cross sections for this channel taken from literature showed a non-physical discontinuity at electron energies close to the threshold energy. This discontinuity has been removed by using a smoothing procedure. For known plasma parameters the deviation between measured and calculated population densities decreases significantly by using the smoothed data. Furthermore, the agreement of the electron density deduced from the ratio H β / H γ with results of other diagnostic methods is enhanced dramatically.

Comparison of plasma parameters determined with a Langmuir probe and with a retarding field energy analyzer

A comparison is made between plasma parameters measured with a retarding field energy analyzer (RFEA), mounted at a grounded electrode in an inductive discharge, and a Langmuir probe located in bulk plasma close to the analyzer. Good agreement between measured plasma parameters is obtained for argon gas pressure in the range 2–10 mTorr. Parameters compared include time averaged plasma potential, the tail of the electron energy distribution function (EEDF), the electron temperature and the ion flux. This highlights the versatility of the RFEA for determining plasma parameters adjacent to the surface where probe measurements are not easily made. Combination of the probe and energy analyzer has enabled the measurement of the EEDF to a higher energy than otherwise possible.

A new approach to solar wind monitoring

The monitoring of solar wind parameters is a key problem of the space weather program. We are presenting a new solution of plasma parameter determination suitable for small and fast solar wind monitors. The first version will be launched during the SPECTR-R project into a highly elongated orbit with apogee ∼350,000 km. The method is based on simultaneous measurements of the total ion flux and ion integral energy spectrum by six identical Faraday cups. Three of them are dedicated to determination of the ion flow direction, the other three (equipped with control grids supplied by a retarding potential) are used for determination of the density, temperature, and speed of the plasma flow. The version under development is primarily designed for the measurements in the solar wind and tail magnetosheath, thus for velocities range from 270 to 750 km/s, temperatures from 1 to 30 eV, and densities up to 200 cm −3. However, the instrument design can be simply modified for measurements in other regions with a substantial portion of low-energy plasma as a subsolar magnetosheath, cusp or low-latitude boundary layer. Testing of the engineering model shows that the proposed method can provide reliable plasma parameters with a high time resolution (up to 8 Hz). The paper presents not only the method and its technical realization but it documents all advantages and peculiarities of the suggested approach.

Spectroscopic observations of coronal waves and coronal mass ejections

It is common to use imaging instruments such as EUV and X-ray imagers and coronagraphs to study large-scale phenomena such as coronal mass ejections and coronal waves. Although high resolution spectroscopy is generally limited to a small field of view, its importance in understanding global phenomena should not be under-estimated. I will review current spectroscopic observations of large-scale dynamic phenomena such as global coronal waves and coronal mass ejections. The aim is to determine plasma parameters such as flows, temperatures and densities to obtain a physical understanding of these phenomena.

Determination of Plasma Parameters during Deposition of ZnO Films by Ceramic and Metallic Targets and Correlation with Film Properties

While magnetron sputtering is a commonly used tool for the deposition of thin films in research and production, the development of suitable models describing film growth on the substrate progresses slowly. One of the major reasons is the complexity of the process, in which energy and particles are delivered to the substrate in a variety of ways. Nevertheless, these effects are essential for film growth and will determine the quality of obtained films. In this article, an example for the characterization of a deposition process with a comparably simple and cost effective method is shown. The total energy flux to the substrate was measured by a thermal probe; plasma parameters were studied by means of Langmuir probe measurements.

プラズマと分光分析 Ｉ．概論

This intensive course gives fundamentals of plasma physics for plasma spectroscopy and its advanced applications such as inductively-coupled plasma atomic emission spectrometry, laser-induced plasma spectroscopy, optical emission spectrometry with glow discharges, etc. The theory of the optical methods used in the plasma diagnostics and the methods for determining plasma parameters such as electron temperature, plasma density, etc. will be described. This course is composed of the series six times and the first part reviews the fundamentals of plasma physics.

Langmuir probe measurements at incomplete rf-compensation

Low-pressure radio-frequency (rf) discharges are widely used in material processing. Internal parameters of such discharges may be determined by Langmuir probes. Due to the varying plasma potential in rf-discharges only time-averaged probe characteristics may be measured. The usual evaluation of such disturbed characteristics gives incorrect plasma parameters. Often the rf-compensation of the probe used to avoid distortions of the characteristic is incomplete and a certain rf-influence remains. It is shown that the distortion of a probe characteristic because of an rf-signal across the probe sheath may be described in general by the convolution of the undistorted characteristic with an apparatus function which is determined by the shape of the signal. Using this concept of convolution, the effect of rf-fluctuations on the probe characteristic and its derivatives may easily be explained and methods for the approximated determination of plasma parameters from characteristics distorted by rf-influence may be derived. The methods are demonstrated by testing calculations and experimental examples.

Spectroscopic and Imaging Study of Combined W and Mo$X$-pinches at 1 MA$Z$-pinch Generators

Experiments with X-pinches made with both Mo and W wires have been performed on 1-MA pulsed power generators at Cornell University and University of Nevada, Reno. X-ray images and spectra have been studied and compared for three different configurations of X-pinch loads with Mo and W wires. For all X-pinches, the image size decreases with decreasing wavelength and photoconducting diode (PCD) signals show multiple bursts except for one variant of the mixed Mo and W configurations. Time-gated, as well as time-integrated, images indicate the presence of radiation from energetic electrons. Previous experience with application of L-shell Mo modeling to various Z- and X-pinch experiments helped to determine plasma parameters in the X-pinches studied here, and permitted identification of M-shell W spectral features useful for plasma parameter estimation

Soft x-ray generation by a tabletop Nd:YAG/glass laser system

The advent and development of ultra-intense tabletop laser systems has played a significantrole in recent decades thanks to the wide number of applications and studies in which thesesystems were demonstrated to be appropriate. Among these, one of the main applicationsof ultra-intense radiation is generation of plasma by solid, liquid or gaseous targets. Theby-product of x-radiation found many different applications such as spectroscopy, imaging,microlithography, microscopy, radiographies (in particular of biological samples),radiation–matter interaction, fundamental plasma parameter determination, astrophysics,inertial confinement fusion, high energy physics, quantum electrodynamics, and manyothers.In the following a brief description of our tabletop Nd:YAG/glass apparatus (facility of theQuantum Electronic and Plasma Laboratory of the University of Rome ‘Tor Vergata’),together with x-ray conversion efficiency studies for different targets, are reported.

Ablative PPT. New quality, new perspectives

An adequate physical model for the ablative pulsed plasma thrusters (APPT) processes was developed as a result of complex theoretical and experimental studies conducted by RIAME for the processes of plasma acceleration in the APPT and determination of plasma parameters, electric currents, magnetic fields, volumetric electromagnetic forces inside and outside the discharge channel. Possibility for reaching higher thrust efficiency values for such thrusters due to the transfer from oscillative discharge to a quasi-aperiodic discharge was proved by test. Such transfer favors better matching for the distributions of volumetric electromagnetic forces and accelerated plasma (propellant) in the thruster. Analysis for the ways to increase the APPT operating process efficiency is presented. An important role of the elements of external power supply circuit for increasing thruster efficiency is shown. The studies conducted allowed development for the models of highly efficient APPT of new generation characterized by specific thrust pulse of up to 15– 22 km / s and thrust efficiency of up to 25–35%, which differ by high stability of operating process, design, technologic and operational simplicity, and low cost. Development of flight models of a highly efficient APPT for the Russian small spacecraft of “Vulkan” type was started.