Electron Beam Output Research Articles

Quality Control Analysis of Linear Accelerator Radiotherapy Device in the Department of Radiotherapy at Pasar Minggu District Hospital

Radiation accidents pose a significant risk, often stemming from inadequate calibration of radiation output, procedural lapses, and faults in radiation monitoring systems. Addressing these risks is pivotal, particularly in radiotherapy, where the precise functioning of linear accelerator (Linac) devices is crucial. This study delves into the quality control procedures applied to the Linac radiotherapy device within the Department of Radiotherapy at Pasar Minggu District Hospital. Drawing upon the renowned reference standards set by the AAPM Task Group 142 and BAPETEN Regulation No. K2N.2/MT-08, this research, conducted in November 2022, rigorously evaluated the mechanical, dosimetry, and safety aspects of the Linac device. The examination encompassed critical elements, including gantry angles, optical distance indicators, laser precision, collimator angles, light field size, and photon and electron beam outputs. Safety features such as door interlocks, audiovisual indicators, and radiation alert systems were scrutinized. The analysis reveals a reassuring finding: the Linac device at Pasar Minggu District Hospital adheres commendably to tolerance limits specified by reference standards across all measured parameters, indicating robust performance in mechanics, dosimetry, and safety. This meticulous quality control regimen has proven highly effective in ensuring the device's operational integrity and safety, affirming its reliability for precise radiotherapy treatments.

Modified calibration protocols in electron beam dosimetry: comparison with IAEA TRS-398 and AAPM TG-51

This study aimed to compare absolute calibration outputs based on the protocols of the International Atomic Energy Agency (IAEA) Technical Report Series (TRS)-398, the American Association of Physicists in Medicine (AAPM) Task Group (TG)-51, and modified calibration approach. The electron beam output calibration followed the IAEA TRS-398 and AAPM TG-51 protocols, both of which required cylindrical chambers and parallel plates. However, the use of cylindrical chambers is not recommended at low energies because of the large fluence-correction factor. TG-51 recommended cross-calibration of the parallel-plate chamber against the cylindrical chamber in a high-energy electron beam. In 2020, an electron beam dosimetry modification was introduced that used a cylindrical ionisation chamber at all energies and updated the data for beam quality conversion factors. This modification provided a lower deviation than that reported in AAPM TG-51. Thus, the modified calibration based on TRS-398 was applied in the present study, which yielded results below the permissible tolerance. The beam calibration at 6, 8, 10, 12, and 15 MeV energies was carried out for two Elekta linear accelerators.. Electron beam dosimetry followed the AAPM TG-51 and TRS-398 protocols, and modified calibration were performed to measure the dose at the maximum depth expressed in dose/monitor units (cGy/MU). Charge-reading measurements were measured using ionisation chambers PTW 30013, IBA CC13, and Exradin A11. The average absorbed dose ratios were 1.004 and 1.009 using the modified calibration and TRS-398 and modified calibration and TG-51, respectively. Therefore, based on IAEA TRS-398, the results were below the tolerance limit (±2%).

Modified electron beam output calibration based on IAEA Technical Report Series 398.

PurposeThe recently worldwide standard measurement of electron beam reference dosimetry include the International Atomic Energy Agency (IAEA) Technical Report Series (TRS)‐398 and Association of Physicists in Medicine (AAPM) Task Group (TG)‐51 protocols. Muir et al. have modified calibration methods for electron beam calibration based on AAPM TG‐51. They found that the use of cylindrical chambers at low energy gave acceptable results. In this study, we propose and report a modified calibration for electron beam based on IAEA TRS‐398, the standard reference dosimetry protocol worldwide.MethodsThis work was carried out with energies of 6, 8, 10, 12, and 15 MeV. The electron beam is generated from Elektra Synergy Platform and Versa HD linear accelerator. The charge readings were measured with PTW 30013, IBA CC13, Exradin A1Sl, and Exradin A11 chambers connected to the electrometer. The dose calculation uses an equation of modified calibration for electron beam using the updated kQ factor in previous work. The absorbed dose to water for electron beam is expressed in dose per monitor unit (cGy/MU). Thus, we compared dose per monitor unit (D/MU) calculation using a modified calibration to TRS‐398.ResultsIn this work, we have succeeded in implementing the modified calibration of electron beam based on TRS‐398 by applying a cylindrical chamber in all energy beams and using the updated kQ factor. The ratio of the absorbed dose to water between original and modified calibration protocols of TRS‐398 (D w) for the cylindrical chamber was 1.002 on the Elekta Synergy Platform and 1.000 on the Versa HD while for the parallel‐plate chamber it was 1.013 on the Elekta Synergy Platform and 1.014 on the Versa HD. Based on these results, both the cylindrical and parallel‐plate chambers are still within the tolerance limit allowed by the TRS‐398 protocol, which is ±2%. Therefore, modified calibration based on TRS‐398 gives acceptable results and is simpler to use clinically.

Software for optimization of beam output during electron beam welding of thin-walled structures

This work is devoted to the issue of beam output optimization during electron beam welding of thin-walled structures. Authors develop a model for optimizing the electron beam output mode, which considers the dynamics of the thermal process in the welded joint zone and depends on the electron beam input mode, the geometric dimensions of the product, and the technological parameters used in the welding process. Based on the proposed approach, a prototype of a software control system for electron beam welding with optimization of the electron beam output was implemented, which allows control at all stages of the technological process.

Dosimetric characterization of medical linear accelerator Photon and Electron beams for the treatment accuracy of cancer patients

In radiotherapy treatment planning process, quality assessment (QA) is indispensable for achieving accuracy and avoidance of treatment errors. In this perspective, present study focused on the Photon and Electron beams characterization of a medical linear accelerator (LINAC) to ascertain dosimetric QA in Absolute and Reference dosimetry. In this connection, the beam outputs were investigated in terms of Dmax and Dw,max (dose at depth dmax) in absolute dosimetry for Photon and Electron beams, respectively. In accordance with the measured Dmax and Dw,max parameters, Photon and Electron beam outputs were standardized to ensure standard output of 1 cGy/MU. In reference dosimetry, the parametric evaluation was performed for dosimetric QA in terms of percent depth dose (PDD), beam profile flatness and symmetry, output factors: Scp, Sc, Sp with varying field size (FS) ranging from 4´4 cm2 to 40´40 cm2 normalized at FS 10´10 cm2 for the 6 MV and 10 MV Photon beams. The measured PDDs at 10 cm depth (D10) were found to be 66.8% and 73.6% for 6 MV and 10 MV Photon beams, respectively, with significantly small deviation of 1% and 0.8% in comparison with an international PDD protocol of British Journal of Radiology-25 (BJR -25). In the case of Electron beams characterization, PDD was verified with 10´10 cm2 cone/applicator, beam profile flatness and symmetry were analyzed at the field sizes ranging from 6´6 cm2 to 25´25 cm2 normalized at 10´10 cm2 cone/applicator, and Electron cone ratios were investigated for a given cone/applicator relative to the 15´15 cm2 one for the 6, 9, 12, 15 MeV Electron energies. The PDDs of all the Electron beams revealed reasonable consistency with manufacturer’s estimations of 90%, 80%, and 50% PDDs at various depths of ionization.

Production and Monitoring of Neutron Flux by Activation Detectors

The neutron generation technique was tested on the microtron M-10 with an output electron beam of 8.7 MeV. Given the low energy that the microtron can provide to electrons, the bremsstrahlung induced photonuclear reaction 9Be (γ, n), which has a low threshold, was chosen for neutron generation. Cobalt and indium targets were tested as activation detectors to estimate the neutron flux density. In the cobalt target, the isomeric state of 60mCo with an energy of 58.6 keV and a half-life of 10.5 minutes is well activated. Two well-known additional gamma lines of standard cobalt source permit to clarify the absolute value of the neutron flux. The activated indium target has four gamma lines bound to the 116mIn isomer β- decaying with the half-life of 54.4 minutes, what is convenient for measurement of gamma spectrum. Despite the low energy of the output electron beam, at a beam intensity of 5 μA it is possible to obtain an almost isotropic neutron flux of 107 n/(s∙cm2).

Production of permanent vacuum-tight connections: copper–aluminum, copper-titanium by diffusion welding for use in microwave electro–vacuum device nodes

The aim of this work is obtaining vacuum-tight CuTi and CuAl connections used for the manufacture of components applied in microwave electro-vacuum devices, for example as electron beam output windows for soldered electron guns.

The concept of an electron beam I/O control system to optimize the weld formation in the process of electron beam welding

The processes that occur during the electron beam welding are very complex. The main problem of electron beam welding is obtaining a reproducible cross section of the weld. This place is subjected to rigorous quality control during the welding of thin-walled joints. In particular, it is required to solve the problem of the welded joint optimal formation on the electron beam input/output section. The development of the mathematical models for the electron beam input and output modes, their joint use as a justification for the choice of the latter modes will allow a reasonable approach to the seam optimal formation in the area under consideration. In the framework of this study, the concept of an electron beam input-output control system for a weld optimizing in the electron beam welding process is presented. Within the framework of this concept, it mathematical and algorithmic software have to be developed for electron beam welding of thin-walled aerospace structures in terms of the electron beam input/output. Such approach will improve the quality of formed integral joints, as well as reduce the complexity of setting up the technological process of electron beam welding. It has to be developed and verified the mathematical models of temperature distribution under various modes of an electron beam input and output, models for optimizing input and output modes of an electron beam, and a software system prototype using the obtained models.

Hollow high-quality electron beam generation by cyclotron autoresonance in laser-induced acceleration

In this study, the dynamics of electrons by a focused Gaussian laser pulse in the presence of an ultrashort axial magnetic field have been investigated numerically. The cyclotron resonance of the electrons due to the external magnetic field were theoretically investigated. An optimized magnetic field can enhance the electron energy gradient with ultra-low scattering. The simulation provides a circulating hollow electron beam suitable for high-precision and high-energy particle physics experiments. The features of output electron beam such as mean energy gain, energy spectra, spatial emittance and angular scattering distribution were examined and their concerning physical explanations have been presented. It has been found that an electron bunch with about MeV initial energy becomes a compressed electron beam with about 3 GeV energy, after interacting with the laser pulse applied by a nanosecond pulsed magnetic field.

A compact electron beam driver based on the annular parallel-plate pulse forming lines

A compact electron beam driver based on an annular parallel-plate pulse forming line (APPPFL) was presented in this paper. Compared with the traditional system, the characteristics of compactness and flat-top waveform output have been achieved by using APPPFLs, which can generate a high voltage quasirectangular pulse up to 20 kV with a width of 60 ns, a rising edge of 10 ns at a lower matched load with an impedance of 1.25 Ω. The key part of the driver is the Marx generator, which consists of 37 stages, each of the stages consisting of an APPPFL, a gas spark switch, two charging inductors, and a nylon insulator that provides insulation between two stages as well as mechanical support. The generator is charged synchronously with positive and negative voltages to reduce the difficulty of the insulation design. When the APPPFL of each stage was charged up to ±20 kV, the output voltage and current of the electron beam driver are 680 kV and 15 kA at a 46 Ω planar diode load, respectively, and the power of the output electron beam is 10 GW. The repetition frequency operation of the electron beam driver has also been investigated.

Directions in plasma wakefield acceleration.

This introductory article is a synopsis of the status and prospects of particle-beam-driven plasma wakefield acceleration (PWFA). Conceptual and experimental breakthroughs obtained over the last years have initiated a rapid growth of the research field, and increased maturity of underlying technology allows an increasing number of research groups to engage in experimental R&D. We briefly describe the fundamental mechanisms of PWFA, from which its chief attractions arise. Most importantly, this is the capability of extremely rapid acceleration of electrons and positrons at gradients many orders of magnitude larger than in conventional accelerators. This allows the size of accelerator units to be shrunk from the kilometre to metre scale, and possibly the quality of accelerated electron beam output to be improved by orders of magnitude. In turn, such compact and high-quality accelerators are potentially transformative for applications across natural, material and life sciences. This overview provides contextual background for the manuscripts of this issue, resulting from a Theo Murphy meeting held in the summer of 2018. This article is part of the Theo Murphy meeting issue 'Directions in particle beam-driven plasma wakefield acceleration'.

Theoretical Study and Monte Carlo Simulation on the Dynamic Process of a Novel Multipacting Cathode for High-Current Diode

The prototype and configuration design of a novel multipacting cathode producing a ring-like electron beam for high-current diode are presented. The whole dynamic process of the moving secondary electron on the multipacting cathode surface is theoretically investigated and numerically simulated using the Monte Carlo method. The results indicate that the prototype of the novel multipacting cathode for high-current diode is feasible. Under the interactions of the applied electric field (~MV/m) in axial and radial directions and the guiding magnetic field (~T) in axial direction, the seed electrons from the triple junctions move with spiral advancing trajectories along axial direction. Electron number can be effectively increased by each impact on the coating surface with high secondary electron emission yield coefficient. This phenomenon will achieve electron current amplification with the ring-like electron beam output till multipacting enters into saturation. The simulated characteristic parameters of the secondary electron and the working range of the multipacting cathode agree with the theoretical results. Under the typical condition, the moving distance of the secondary electron is on the order of submillimeters, the fight time is on the order of picoseconds, and the spread speed is on the order of 106 to 107 m/s. In addition, the multipacting saturation mechanism is analyzed, and the emission current density is roughly estimated to ~kA/cm2. Enhancing the magnitude of applied electric field in radial direction can effectively improve the emission current density.

The technology of forming Ti-Nb layers on the surface of titanium alloy plates using a high-voltage electron beam output into a protective argon medium

The structure and properties of layers obtained by electron-beam melting of titanium-niobium powder mixtures in a protective argon medium are studied in the work. The method allows cladding traces 16.5 … 17.5 mm wide with a maximum thickness of 3.5 … 4.5 mm. The concentration of niobium in the formed surface layers is 6.6 and 13.8%. The cladded material has a predominantly lamellar structure. The production of layers in the protective medium of argon makes it possible to increase the microhardness level, as well as the corrosion resistance of titanium in boiling solutions of nitric and sulfuric acid.

On-site audits to investigate the quality of radiation physics of radiation therapy institutions in the Republic of Korea

PurposeTo investigate and improve the domestic standard of radiation therapy in the Republic of Korea. MethodsOn-site audits were performed for 13 institutions in the Republic of Korea. Six items were investigated by on-site visits of each radiation therapy institution, including collimator, gantry, and couch rotation isocenter check; coincidence between light and radiation fields; photon beam flatness and symmetry; electron beam flatness and symmetry; physical wedge transmission factors; and photon beam and electron beam outputs. ResultsThe average deviations of mechanical collimator, gantry, and couch rotation isocenter were less than 1mm. Those of radiation isocenter were also less than 1mm. The average difference between light and radiation fields was 0.9±0.6mm for the field size of 20cm×20cm. The average values of flatness and symmetry of the photon beams were 2.9%±0.6% and 1.1%±0.7%, respectively. Those of electron beams were 2.5%±0.7% and 0.6%±1.0%, respectively. Every institutions showed wedge transmission factor deviations less than 2% except one institution. The output deviations of both photon and electron beams were less than ±3% for every institution. ConclusionsThrough the on-site audit program, we could effectively detect an inappropriately operating linacs and provide some recommendations. The standard of radiation therapy in Korea is expected to improve through such on-site audits.

Radiotherapy reference dose audit in the United Kingdom by the National Physical Laboratory: 20 years of consistency and improvements

Background and Purpose Audit is imperative in delivering consistent and safe radiotherapy and the UK has a strong history of radiotherapy audit. The National Physical Laboratory (NPL) has undertaken audit measurements since 1994 and this work examines results from these audits. Materials and Methods This paper reviews audit results from 209 separate beams from 82 on-site visits to National Health Service (NHS) radiotherapy departments conducted between June 1994 and February 2015. Measurements were undertaken following the relevant UK code of practice. The accuracy of the implementation of absorbed dose calibration across the UK is quantified for MV photon, MeV electron and kV x-ray radiotherapy beams. Results Over the measurement period the standard deviation of MV photon beam output has reduced from 0.8 % to 0.4 %. The switch from air kerma- to absorbed dose-based electron code of practice contributed to a reduction in the difference of electron beam output of 0.6 % (p < 0.01). The mean difference in NPL to local measurement for radiation output calibration was less than 0.25 % for all beam modalities. Conclusions The introduction of the 2003 electron code of practice based on absorbed dose to water decreased the difference between absolute dose measurements by the centre and NPL. The use of a single photon code of practice over the period of measurements has contributed to a reduction in measurement variation. Within the clinical setting, on-site audit visits have been shown to identify areas of improvement for determining and implementing absolute dose calibrations.

Generation of ultrafast broadband small angle hundreds MeV electron bunches from laser wakefield acceleration

Electrons can be accelerated to a GeV level in centimeters by plasma wakefield driven by laser. With the development of chirped pulse amplification technique, the accelerating field can reach 100 GV/m. The laser driven wakefield acceleration experiments with ionization injection are carried out using 68 TW (1.7 J, 25 fs) laser and a mixture gas of 99% He and 1% N2. In experiment, the output electron beam has broadband spectrum with a maximum cut-off energy of about 290 MeV and a maximum output energy is quite stable in a certain range of laser focal positions. Two-dimensional particle-in-cell simulation is carried out. It is found that the longitudinal phase space is occupied by the continuously injected electrons and the phase space distribution is quite stable after the laser has propagated several millimeters inside plasma. This acceleration process can lead to quite stable maximum output energy of electron beam. These experiments reveal the physical nature of continuous ionization injection, which is very important for improving the performance of ionization injection.

Electron beam output of an ELEKTA Sli-Plus linear accelerator for irregular shaped fields and for extended SSD

Introduction A dosimetric study of the electron beam output of the ELEKTA Sli-Plus linear accelerator is being presented: (a) when customized electron cutouts are used in order to shape the field, (b) when the treatment is performed in extended Source-Skin Distance. Purpose We have investigated how the machine output varies when electron cutouts of different shapes and sizes are inserted into the beam with the aim to establish a method to predict the beam output in similar circumstances. In order to determine the effective SSDs and the position of the effective point source, the Inverse Square Law (ISL) method has been used for all electron energies and applicators in order to correct the output at extended SSDs applying the ISL correctly. Materials and methods An extended set of output measurements has been performed using electron beams blocked by customized electron cutouts. Measurements have also been carried out in a water phantom at the depth of maximum dose as a function of the air gap g between the far end of the applicator and the phantom surface. Measurements have been compared to calculations with the Oncentra Masterplan treatment planning system. Results & conclusion Our results indicate that the electron beam output does not vary significantly with the insertion of an electron cutout into the beam and therefore, the monitor units determined for a given electron applicator can be used for the blocked beam as well. Monitor Units can also be safely determined by using the SSD eff in order to account for the change in output and depth-dose distribution. Disclosure The authors declare that they have no conflict of interest or any relationship that may bias their presentation.

Design study of double-layer beam trajectory accelerator based on the Rhodotron structure

In this paper, the conceptual design of a new structure of industrial electron accelerator based on the Rhodotron accelerator is presented and its properties are compared with those of Rhodotron-TT200 accelerator. The main goal of this study was to reduce the power of RF system of accelerator at the same output electron beam energy. The main difference between the new accelerator structure with the Rhodotron accelerator is the length of the coaxial cavity that is equal to the wavelength at the resonant frequency. Also two sets of bending magnets were used around the acceleration cavity in two layers. In the new structure, the beam crosses several times in the coaxial cavity by the bending magnets around the cavity at the first layer and then is transferred to the second layer using the central bending magnet. The acceleration process in the second layer is similar to the first layer. Hence, the energy of the electron beam will be doubled. The electrical power consumption of the RF system and magnet system were calculated and simulated for the new accelerator structure and TT200. Comparing the calculated and simulated results of the TT200 with those of experimental results revealed good agreement. The results showed that the overall electrical power consumption of the new accelerator structure was less than that of the TT200 at the same energy and power of the electron beam. As such, the electrical efficiency of the new structure was improved.

Measurement of Energy Parameters for Electron Gun Heater Currents and Output Dose Rate for Electron Beams from a Prototype Linac

The dosimetric characteristics were experimentally evaluated for electron beams from the prototype linac developed for radiotherapy units. This paper focuses on the electron beam output and energy variations as a function of electron gun heater current. The electron energy was derived from its mean and most probable energies measured by film dosimetry. The electron beam output at the maximum electron energy was measured with the plane parallel ionization chamber in water using TRS-398 dosimetry protocol. The mean energy and the most probable energy of the electron beam were 6.54∼3.31 MeV and 5.94∼2.80 MeV at electron gun current of 2.02∼2.50 A respectively. The output dose rate for an electron beam of mean energy 6.54 MeV was 5.41 Gy/min ±1.5% at the reference depth in water.

Measurement of Electron Beam Output for the Prototype Compact Linac

1 This work was supported by the National Research Foundation of Korea (DIRAMS) grant funded by the Korea government(MSIP)(No. 50495-2015). Received 17 February 2015, Revised 9 March 2015, Accepted 13 March 2015 Correspondence: Dong Hyeok Jeong (physics7@empas.com) Tel: 82-51-720-5813, Fax: 82-51-720-5826 cc This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Measurement of Electron Beam Output for the Prototype Compact Linac