Electron Beam Characteristics Research Articles

Phenomena observed in electron EBRT using a pulse-by-pulse radioluminescence dosimetry system with cloud-based analytics

The pulse-by-pulse characteristics of electron beams from a clinical linear accelerator (linac) at high dose rates are crucial for ensuring precise dose delivery in radiation therapy. In this research, we employ a radioluminescence scintillator made from Ge-doped silica optical fiber to analyse electron beams at standard therapy dose rates 600 cGy/min with energy of 15 MeV. The scintillator is combined with a photomultiplier tube (PMT) and a photon-counting setup to achieve microsecond (μs) gating times, providing high temporal resolution. For sub-microsecond (sub-μs) temporal resolution, we utilize a multi-pixel photon counter and a rapid digital oscilloscope. Our study examines the peak time and the time it takes for pulses to return to baseline, uncovering the effects of afterglow at elevated dose rates and its potential implications for dosimetry precision. Our results indicate that monitor chambers, which have lower temporal resolution than the radioluminescence system outlined in this study, may struggle to accurately track high-rate dose delivery, emphasizing the necessity for advanced monitoring methods in FLASH radiotherapy. The dosimetric data was further analysed for deeper analytics on a cloud-based system. The dosimetric data underwent advanced analysis on a cloud-based platform, employing a prototype analytics software system comprised of Dosi-Client and Dosi-Cloud Backend components for real-time data acquisition and processing. This innovative approach revealed significant insights into radiation dosimetry, including the detection of anomalies through a reconstruction convolutional autoencoder, enhancing the precision and reliability of dosimetric measurements.

LOW INTENSITY BEAMS OF ELECTRONS AND POSITRONS IN THE ENERGY RANGE UP TO 100 MeV AT IHEPNP FACILITY

The article considers possible characteristics of low-intensity secondary positron and electron beams, which can be obtained using an electron accelerator with energy of ~100 MeV and average current of some μA. Preliminary simulation shows that using a tungsten converter of 2X0 thick and collimation of secondary particles beam, such accelerator allows one to get electron and positron secondary beams with energy of ~ 5…70 MeV, intensity of ~10-6-8 from the primary electron beam intensity, and energy spread of about some percent. Such low-intensity beams can be used for researches in the field of interaction of radiation with amorphous ubstances and crystals, testing detectors and scintillation materials.

Design, manufacturing, evaluation, and performance of a 3D-printed, custom-made nozzle for laser wakefield acceleration experiments.

Laser WakeField Acceleration (LWFA) is extensively used as a high-energy electron source, with electrons achieving energies up to the GeV level. The produced electron beam characteristics depend strongly on the gas density profile. When the gaseous target is a gas jet, the gas density profile is affected by parameters, such as the nozzle geometry, the gas used, and the backing pressure applied to the gas valve. An electron source based on the LWFA mechanism has recently been developed at the Institute of Plasma Physics and Lasers. To improve controllability over the electron source, we developed a set of 3D-printed nozzles suitable for creating different gas density profiles according to the experimental necessities. Here, we present a study of the design, manufacturing, evaluation, and performance of a 3D-printed nozzle intended for LWFA experiments.

An Investigation of High-Z Material for Bolus in Electron Beam Therapy

Electron beams are frequently used for superficial tumors including: primary skin cancers, surgical scars, cutaneous lymphomas and benign conditions like keloids. However, due to electron beam characteristics the surface dose is 75-95% of the prescribed dose depending on beam energy thus requiring placement of bolus to augment surface dose. Various types of boluses; wet gauge/towel, superflab, superstuff, aquaplast, 3D printed plastics, customized dot-decimal bolus, thermoshield, brass and tantalum wire mesh are commonly used in clinics with variable difficulties that are not perfect. As majority of these devices do not snug to the skin contour and create air-gap that is known to produce significant dose perturbations creating hot and cold spot. The variable dosimetry has cosmetic implications and potentially increased risk of recurrence. A new cloth-like high-Z materials; Tungsten, (Z = 74) and Bismuth, (Z = 83) impregnated with silicone gel are now commercially available which is investigated in this study for bolus purpose. Commercially available, super soft silicone-gel based submillimeter thin Tungsten and Bismuth sheets were investigated for bolus properties in electron beams in the range of 6-12 MeV using 10x10 cm2 applicator. These materials were tested on various body contour for perfect snug without any air traps. Using parallel plate ion chamber measurements were performed in a solid water phantom on a medical linear accelerator machine. Depth dose characteristics were measured to optimize the thickness for surface dose to be 100% for selected electron therapy. Surface dose for a 10x10 cm2 cone for 6, 9, 12 MeV beams were measured to be 75.1%, 80.1% and 86.2%, respectively. Silicone-gel Tungsten and Bismuth sheets produce significant electrons thus increasing surface dose. Based on measured depth dose, our data showed that Tungsten sheets of 0.14 mm, 0.18 mm and 0.2 mm and Bismuth sheets of 0.42 mm, 0.18 mm and 0.2 mm provide 100% surface dose for 6, 9 and 12 MeV beams, respectively without any changes in depth dose except increasing surface dose. The new Tungsten and Bismuth based silicone-gel clothlike sheets are extremely soft but high tensile metallic bolus materials that can fit flawlessly on any skin contour without any air trap or variable thickness or spillage of the water as in conventionally used wet gauge. Only 0.2 mm thick sheets are needed for 100% surface dose without degradation of the depth dose characteristics. These materials are reusable and ideal for bolus in electron beam treatment. This investigation opens a new frontier in designing new bolus materials optimum for patient treatment.

Influence of gas pressure and gas type on pseudospark electron beam

Pseudospark discharge is a discharge that occurs in the left band of the Paschen curve. According to previous studies, an electron beam will be generated in the initial stage of pseudospark discharge. This electron beam has the advantages of high energy, high current and self-confinement. It has a promising application in high-power microwave sources, surface treatment of metal materials, etc. To investigate the characteristics of this electron beam, a pseudospark discharge experimental platform is established in this paper. A pseudospark chamber is designed for pseudospark discharge. To trigger the discharge, a high voltage pulse trigger signal is generated by an avalanche transistor Marx circuit and a trigger unit is designed to generate trigger electrons. Faraday Cup is utilized to collect the electron beam and measure the electron waveform. In order to quantitatively characterize the electron beam, we define six electron beam characteristics, including trigger delay, peak current, electron beam charge, electron beam width, electron beam loop current ratio and electron beam loop charge ratio. To investigate the influence of gas pressure and gas type on electron beam characteristics, we experimentally obtained results of electron beam characteristics for different gas pressures and gas type. We mainly investigated the change rule of the electron beam characteristics when the gas pressure changes between 6 Pa and 20 Pa and the similarities and differences of the electron beams under the two gas environments, argon and nitrogen. We find that gas pressure can be used for the modulation of electron beam time delay. The width of the electron beam in the case of nitrogen has a very stable relationship with the gas pressure. Gas pressure and gas type are two important means of controlling the characteristics of pseudospark electron beams.

Using PRIMO to determine the initial beam parameters of Elekta Synergy linac for electron beam energies of 6, 9, 12, and 15 MeV.

The purpose of this research was to establish the primary electron beam characteristics for an Elekta Synergy linear accelerator. In this task, we take advantage of the PRIMO Monte Carlo software, where the model developed contains the majority of the component materials of the Linac. For all energies, the Elekta Linac electron mode and 14 × 14 cm2 applicator were chosen. To obtain percentage depth dose (PDD) curves, a homogeneous water phantom was voxelized in a 1 × 1 × 0.1 cm3 grid along the central axis. At the reference depth, the dose profile was recorded in 0.1 × 1 × 1 cm3 voxels. Iterative changes were made to the initial beams mean energy and full width at half maximum (FWHM) of energy in order to keep the conformity of the simulated and measured dose curves within. To confirm simulation results, the Gamma analysis was performed with acceptance criteria of 2 mm - 2%. From the validated calculation, the parameters of the PDD and profile curve (R100, R50, Rp, and field size) were collected. Initial mean energies of 7.3, 9.85, 12.9, and 15.7 MeV were obtained for nominal energies of 6, 9, 12, and 15, respectively. The PRIMO Monte Carlo model for Elekta Synergy was precisely validated. PRIMO is an easy-to-use software program that can calculate dose distribution in water phantoms.

Simulation of Emission Processes in Strong Electromagnetic Fields

The problem of calculating the processes of electron emission from metal surfaces in strong electromagnetic fields is considered with allowance for relativistic effects. One of the methods of simulation in these processes is the particle method combined with grid calculation of fields on the basis of Maxwell’s equations. Similar techniques have been developed since the 1960s to the present. However, existing approaches have certain limitations. In this work, for an axisymmetric geometry of the generating system, a new numerical technique simulating the processes of electron emission from metal cathode surfaces is presented. The technique uses the representation of large smoothed Gaussian particles and implements the calculation of electromagnetic fields on Cartesian spatial grids. The software implementation is oriented to parallel computing. The aim of numerical experiments was to determine the parameters of electron emission. Diode and triode cylindrical systems were chosen as test problems. In numerical calculations, the spatiotemporal characteristics of relativistic electron beams generated by emission processes are obtained, including the reproduction of the Child–Langmuir current. The numerical technique developed has confirmed its correctness and efficiency.

Effect of Non-Ideal Electron Beam Characteristics on the Performance of a Megawatt-Power Gyrotron with an External Monochromatic Signal

Effect of Non-Ideal Electron Beam Characteristics on the Performance of a Megawatt-Power Gyrotron with an External Monochromatic Signal

Quantitative analysis of the wave polarization effect on electron capture in a laser acceleration channel

The main purpose of this paper is to explore thoroughly the polarization effect in the capture and acceleration scenario (CAS) scheme using Jones vectors, as well as to conduct a quantitative study of the characteristics of electron beams interacting with EM fields with any polarization states. The simulation provides a circulating hollow electron beam suitable for high-energy particle physics experiments. In this paper, by properly injecting low-energy free electrons into the acceleration channel of a laser pulse in optimal polarization state with an intensity of a0≡eE0/m0cω0=15, a satisfactory result was achieved compared to other works that used extra-high intensity laser pulses (a0≃100). It was observed that the characteristics of the output beam for circular polarization, compared to other polarizations, have more advantages, such as showing less energy spread and spatial divergence, although the mean energy in this case is lower than in other polarizations. Moreover, for a circularly polarized (CP) field, the total fraction of CAS electrons can reach over 98% of the incident electrons. These features demonstrate that the circular polarization in the CAS scheme provides greater acceleration efficiency.

Effect of Welding Speed and Post-Weld Heat Treatment on Microstructural and Mechanical Properties of Alpha+Beta Titanium Alloy EB Welds

The current work aims to examine the influence of various welding speeds (500, 700, and 800 mm/min) on the microstructure and mechanical characteristics of electron beam–welded Ti-6Al-4V alloy joints. The base metal microstructure was composed of a slightly elongated α phase and a transformed β phase, whereas the fusion zone (FZ) exhibited an acicular martensitic α′ microstructure. This is due to faster cooling rates in the FZ associated with electron beam welding. The welds prepared with a 800 mm/min welding speed showed higher strength and lower ductility [yield strength (YS): 959 ± 6 MPa, ultimate tensile strength (UTS): 993 ± 5 MPa, percent elongation (%El): 8] compared to those prepared with 500 mm/min (YS: 909 ± 4 MPa, UTS: 956 ± 5 MPa, %El: 11). This was due to a decrease in the width of the α-platelets in the FZ owing to faster cooling rates at higher welding speeds. For all welding speeds, samples that underwent post-weld heat treatment (PWHT) displayed a noteworthy reduction in both UTS and hardness values compared to all the as-welded samples. However, the welds at lower welding speeds showed lower strength and higher ductility (YS: 868 ± 5 MPa, UTS: 922 ± 4 MPa, %El: 13) compared to higher welding speeds (YS: 892 ± 5 MPa, UTS: 938 ± 6 MPa, %El: 9) after PWHT. This is due to the formation of the diffusional product α + β phase in the FZ, as evidenced by the transmission electron microscope results.

Effect of carbon nanotubes on curing characteristics of low energy electron beam curing CFRPs

AbstractLow energy electron beam (E‐Beam) curing process has been considered a promising fabrication technology in high‐efficiency and low‐cost OOA curing, but still not been widely used in industrial applications, mainly limited by the poor mechanical properties of the CFRP resulting from the poor toughness of the low‐energy E‐Beam curable resin. This paper extended the excellent effect of carbon nanotubes (CNTs) toughened resin to the E‐Beam curable resin system, and focused on the influence law and mechanism of CNTs on the curing characteristics of the resin. Theoretical analysis showed that the carboxylated CNTs affect the curing characteristics by participating in the chain transfer link of the cationic curing process. According to the DSC experimental results, the activation energy of the curing reaction of the resin were reduced from 136.2 kJ·mol−1 without adding CNTs to 123.9 kJ·mol−1, 118.3 kJ·mol−1, 112.8 kJ·mol−1 and 105.8 kJ·mol−1 at 0.25 wt.%, 0.5 wt.%, 0.75 wt.% and 1 wt.% of CNTs adding amount respectively, due to which the curing degree of the E‐Beam curable CFRPs were improved with the increase of CNTs contents. Considering the E‐Beam dose attenuation and its influence on curing characteristics, prepregs were irradiated single‐sided or both sided for efficient preparation of E‐Beam cured CFRP components subsequently, for which the curing degree along the prepreg thickness were investigated through the curing reaction kinetic models and DSC experiments. This study will provide research basis for parameter optimization of CNTs contents, and performance improvement of E‐Beam cured CNTs/CFRP.

Characteristics of electron beams accelerated by parallel and antiparallel circularly polarized Laguerre–Gaussian laser pulses

Characteristics of electron beams accelerated by parallel and antiparallel circularly polarized Laguerre–Gaussian laser pulses

Controllable electron self-injection in laser wakefield acceleration with asymmetric gas-jet nozzle

AbstractBeam charge control in the staging of laser wakefield acceleration (LWFA) is a crucial technique for developing full-optical jitter-free high-energy electron accelerators. Precise control of total charge in pre-accelerated electron bunches is necessary to achieve practical electron beam characteristics in the final acceleration stage(s). In contrast to the well-known cathode techniques in conventional accelerators, in LWFA the electron injection results from non-linear processes originating from plasma wave breaking. Therefore, the development of charge control requires a deep understanding of the electron self-injection processes and applications of non-trivial tools. The use of asymmetric gas-jet nozzles seems to be a promising way in developing charge control via tuning the target parameters such as plasma density, density slope, and acceleration length. Here, we demonstrate and characterize controllable electron self-injection, owing to a parametric resonance in slantwise density gas jets irradiated by 50 TW femtosecond laser pulses. The measured characteristics of the electron bunches, in which charge and energy distribution depend on the gas density and gas density gradient, agree well with those obtained by multidimensional particle-in-cell simulation and confirm the possibility of charge control.

Fast Time Response Full Absorption Faraday Cup and Its Application in the Measurement of Intensive Electron Beam Diodes

A magnetically insulated transmission line (MITL) is an inevitable choice for ultra-high power density energy transmissions. Its working process is complex, with an obvious influence on the working process of electron beam diodes and other load devices. The power coupling process of an electron beam diode driven by an MITL is a difficult problem in pulse power applications. No research is available on the electron beam characteristics of its anode. In this paper, a fast time response full absorption Faraday cup was developed. An intense electron beam measurement waveform showing the multi-stage characteristics was obtained through measurements using the Faraday cup absorber as the anode of the electron beam diode. The stage characteristics of the beam were in good agreement with the vacuum transmission, magnetic insulation formation, and multi-stage process of the stable magnetic insulation. The beam intensity corresponded with the conduction current of the cathode. It was obviously smaller than the current of the anode. The results reflected the influence of the different processes of the magnetic insulation on the transmission line on the beam waveforms in the diode area and provided a reference for the power transmission of the power device and the load system design.

BEAM-PLASMA REACTORS FOR FUNCTIONAL GRADIENT MATERIALS PRODUCTION

Application and perspectives of beam-plasma chemical rectors generating cold hybrid plasma for production of functionally graded polymeric materials for tissue engineering and regenerative medicine are considered. Oxygen hybrid plasma was produced by joint action of a continuous or intermittent electron beam and a capacity coupled radio-frequency (RF) gas discharge (13.56 MHz) on gaseous media at moderate pressures (~ 1000 Pa). The scanning electron beam (accelerating voltage, 30 kV, and beam current, 1-1.5 mA) was injected through the grid of the active RF electrode; polymeric samples were placed in the gap between electrodes of the RF-discharge system. Electron beam characteristics, namely, scanning mode and power, can instantly and independently control the reaction volume geometry as well as concentrations of active plasma particles. Methods for such control by means of the scanning of intermittent electron beams are described. As a result, the RF discharge can be accurately localized on the desirable zone of the polymeric surface forming abruptly structured patterns or smooth gradients of functionalities, while radiation and thermal damages of polymers are prevented. The approach was tested using polymethylmethacrylate, polyethylenterphtalate, and polycarbonate samples, and the changes in the chemical composition and hydrophilic properties of their surfaces were shown, which are associated with the improvement of biocompatibility of the plasma-modified polymers.

Single-shot measurements of pulse-front tilt in intense ps laser pulses and its effect on accelerated electron and ion beam characteristics (invited).

We report recent single-shot spatiotemporal measurements of laser pulses, including pulse-front tilt (PFT) and spatial chirp, taken at the Compact Multipulse Terawatt laser at the Jupiter Laser Facility in Livermore, CA. STRIPED FISH, a device that measures the complete 3D electric field of fs to ps laser pulses on a single shot, was adapted to near infrared for these measurements. We present the design of the instrument used for these experiments, the on-shot measurements of systematic high-order PFT, and shot-to-shot variations in the measurements of spatiotemporal couplings. Finally, we simulate the effect of PFT in target normal sheath acceleration experiments. These simulations showed that pulse front tilt can steer hot electrons, shape the distribution of the accelerating sheath field, and increase the variability of cutoff energy in the resulting proton spectra. While these effects may be detrimental to experimental accuracy if the pulse front tilt is left unmeasured, hot electron steering shows promise for precision manipulation of the particle source for a range of applications, including irradiation of secondary targets for opacity measurements, radiography, or neutron generation.

Stress corrosion characteristics of electron beam welded titanium alloys joints in NaCl solution

The Ti6321 titanium alloy has stress corrosion sensitivity in 3.5% NaCl solution, and the sample with cracks will fracture in a short time. The aim of this paper is to reveal the key factors affecting the stress corrosion resistance and clarify the stress corrosion mechanism of different regions of the joint by studying the crack propagation and stress corrosion critical stress intensity factor of the different regions of titanium alloy welded joint. Stress corrosion cracking, fracture and crack propagation path of electron beam welded titanium alloy joint were analyzed, characteristics of microstructure, texture and electrochemical were studied. The results indicated that the stress corrosion intensity factor KISCC of the weld metal is >76.50 MPa • m 1 / 2 , and the maximum KISCC value of heat affected zone is 51.62 MPa • m 1/2 , so KISCC of weld metal is better than heat affected zone. The crack growth rate of weld metal is slightly higher than that of heat affected zone. The fractured surface of weld metal has no obvious stress corrosion characterization, while heat affected zone has. The propagation path of weld metal is more zigzag than that of heat affected zone. The results reveal that microstructure, texture and electrochemical properties are the main reasons for stress corrosion. • The stress corrosion of titanium alloy electron beam welded joint in different regions has been studied. • The stress corrosion resistance of weld metal is significantly higher than heat affected zone, which is related to composition, microstructure and microtexture. • The stress corrosion crack mechanism of titanium alloy welded joint is the combined action of crack propagation and potential corrosion under stress.

Effect of the Spatial Arrangement of Floating Builds with Minimum Support on the Microstructural and Mechanical Characteristics of Electron Beam Additively Manufactured Biomedical Ti-6Al-4V Alloys.

In this study, normal and floating builds of Ti-6Al-4V were fabricated by electron beam additive manufacturing. The effects of the spatial arrangement on the microstructure, mechanical properties, and surface roughness of the parts were investigated. Both the normal and floating builds exhibited an α+β lamellar microstructure, but the normal builds had finer grains compared to the floating builds. The microstructural characteristics were correlated with the thermal history, specifically the cooling rate, resulting from the connection plate (S45C for the normal builds and the powder bed for the floating builds). The compressive yield strength and hardness of the normal builds were higher than those of the floating builds, regardless of build location owing to the grain refinement effects on the normal builds. The top surface (TS) of the sample was smoothest, and the lateral surface of the sample was the roughest for both the normal and floating builds; however, the roughness of the TS and bottom surface samples did not differ significantly between normal and floating builds. There were no noticeable differences in the microstructure and mechanical properties of the builds in five different positions, that is, the center and four corners. Finally, these findings were used to develop a set of conceptual spatial arrangement designs, including floating builds, to optimize the microstructure and mechanical properties.

Formation of Sheet Helical Electron Beams for High-Power Planar Gyrotrons

Planar magnetron-injection gun forming a powerful (3 MW) sheet helical electron beam (HEB) for 140 GHz gyrotron was designed. Modified scheme of an electron beam analyzer based on the retarding electric field method was developed to measure the electron beam characteristics, including pitch-factor and velocity spread. Experimental results are in good agreement with theoretical predictions and demonstrate feasibility of formation of a wide (20 mm) sheet HEB with an energy of 100 keV, a current of 30 A and a pitch-factor of above 1.2 – 1.3.

A Carbon-Nanotube Cold-Cathode Reflex Klystron Oscillator: Fabrication @ X-Band and Returning Electron Beam Realization

This paper presents the design and fabrication of a reflex klystron oscillator based on a carbon nanotube (CNT) cold-cathode. An X-band klystron oscillator structure is assembled with a CNT cold-cathode electron gun with an electrostatic focusing, a re-entrant cavity as anode, and a repeller. The electron gun adopts a convex CNT film emitter as the cathode. A re-entrant cavity resonating at 8.376 GHz is fabricated. The study mainly focuses on the returning electron beam in the klystron oscillator structure. The experimental results of variations of the anode current and returning electron beam amplitude with repeller voltage are presented. It is demonstrated that a higher extracting voltage of the cold-cathode has an important influence on the returning electron beam. To decelerate electron velocity from the extracting voltage, increasing negative focusing voltage and focusing electrode height in the electron gun can improve the returning electron beam characteristics.