Beam Accelerator Research Articles

Overview of the Rare isotope Accelerator complex for ON-line experiments (RAON) project

A new rare-isotope beam (RIB) accelerator complex, RAON, is being constructed in the Institute for Basic Science (IBS) in Korea. RAON is equipped with both isotope separation online (ISOL) and in-flight fragmentation (IF) systems and ultimately combines them to provide more neutron-rich (than any single mode operation) ion beams to the users. However, due to the delay in developing high-energy superconducting cavities and cryomodules, it was decided to proceed with the RAON construction project in two phases. In the first phase, the low-energy accelerator system, ISOL, and all experimental setups will be completed by the end of 2022. In the second phase, the high-energy superconducting system will be completed by 2029 or later. In this contribution, the status of the accelerators, RIB production systems, and experimental instruments for RAON is summarized.

Development of an acrylic emulsion paint added with cellulosic dispersion treated with an electron beam accelerator

Paint is a prevalent type of surface of coating well known to most peoPaint is a prevalent type of surface of coating well known to most people. It is an easy-to-apply product, with excellent physical and chemical resistance and a wide range of applications. The function of a paint is to protect and beautify amongst other properties. Paints are formed using five components: resin, pigments, fillers, solvents and additives. This work deals with a specific type of paint, composed of a water-based acrylic emulsion, whose film formation is by coalescence and used to coat walls and other surfaces. The aim of this innovative research was to evaluate the effect of the addition of cellulosic dispersion of waste paper tissues treated by electron beam irradiation to an acrylic emulsion-based paint. The methodology used was a case study carried out at the Nuclear and Energy Research Institute that consisted of adding aqueous dispersions of cellulosic wipes with mass concentrations varying from 0.1% to 10% in deionized water, and treated by electron beam processing with absorbed doses from 5 kGy to 50 kGy. The results obtained followed the parameters of the Abrafati Sectorial Quality Program. The main sample parameters analyzed were specific density, which reached an average of 1.35 g/cm3; and covering power, whose value of 93.55% was above the specified limit (minimum of 90%). Among other results obtained, improvements in appearance, applicability and functionality were significant. It was concluded that this research constitutes an incremental improvement to the acrylic emulsion paints segment, and environmental sustainability, through the reuse of cellulosic tissue residues

A novel damage detection technique for laminated composite beams under the action of a moving load

The present paper investigates damage detection in laminated composite beams under the action of a moving load. A novel approach is introduced to present damage indices by utilizing the dynamic response of the beam. The equations of motion for the beam have been derived by considering in-plane and out-of-plane deformations, rotary inertia, and shear effects. To obtain the solution, the finite element method, in conjunction with the Newmark algorithm, has been employed. Three damage indices, namely the Displacement Variation Index (DVI), Velocity Variation Index (VVI), and Acceleration Variation Index (AVI) have been introduced. These indices are utilized to detect the location of damage based on the beam's displacement, velocity, and acceleration, respectively. Furthermore, the proposed approach enables to detect single and multiple damages at different severities, locations, and boundary conditions. Likewise, it is applicable to various velocities of moving forces and can effectively operate in both normal and noisy conditions. The results of this investigation demonstrate that the proposed damage indices are able to accurately detect damage along the entire length of the beam without prior knowledge of its healthy state. It is noteworthy that the acceleration-based index, among the indices proposed in this study, exhibits the highest efficiency in determining the precise location of the damage under operational conditions.

Improved compact representation method for Monte Carlo phase spaces

Phase space files used in particle Monte Carlo simulations can be large, and thereby awkward to distribute and slow to load into memory. To circumvent this, compact source models and phase space representations have been developed. In this study, the aim is to increase the versatility of a previously presented method, based on principal component analysis whitening, by evaluating several modifications to the method on simulated cone-beam computed tomography projection images. Scaling the phase space components before whitening was seen to give the largest improvement and allowed for accurate modelling of phase spaces with a shifted detector and/or a bowtie filter present, configurations where the original method struggled. The modified method reproduced results using the original phase space to within a few percent both in energy fluence on the detector and in simulated projection and scatter images of a patient pelvis, without obvious position-dependence of the errors. Hence, the modified method was deemed sufficiently accurate for most applications relying on cone-beam computed tomography simulations. The final aim is to use the more versatile method for a broader range of phase space-based applications such as linear accelerator beam simulations and room shielding calculations.

Radiation‐Induced Admicellar Graft Polymerization of 2‐Hydroxyethyl Methacrylate onto Polyvinylidene Fluoride Membranes Using an Electron Beam Accelerator

AbstractThe efficiency of admicellar graft polymerization in functionalizing polyvinylidene fluoride (PVDF) membranes was explored. The effect of 2‐hydroxyethyl methacrylate (HEMA) concentration and the absorbed dose was investigated using a simultaneous method of radiation‐induced graft polymerization. The degree of grafting increased with raising the absorbed dose and HEMA concentration. The Fourier transform infrared (FTIR) peak for C–O stretch and the asymmetric and symmetric stretching of the C–O–C bridge, respectively, proved the presence of poly(2‐hydroxyethyl methacrylate) (PHEMA) on the modified PVDF. As the grafting yield increased, rougher surfaces were observed. According to contact angle analysis, the grafted membrane with a higher grafting yield outperformed the low grafting yield membrane in terms of water flux and hydrophilicity.

Beamline and vacuum system design of HEBT for the A-FNS accelerator

The Advanced Fusion Neutron Source (A-FNS) project is progressing at the QST Rokkasho institute, Japan. The A-FNS will conduct fusion neutron irradiation tests of materials for a fusion demonstration reactor (DEMO reactor). For these tests a high intensity deuteron beam accelerator is used to produce a high neutron flux with the neutron energies around 14 MeV. The accelerator system accelerates a deuteron beam to a beam energy of 40 MeV, guides the beam towards a liquid lithium target and shapes the uniform beam at the Li target using a magnet system.Two of the main considerations for the A-FNS high energy beam transport (HEBT) design are protection of the Superconducting Radio-Frequency linear accelerator (SRF) and vacuum system design for the interface of the HEBT and the target system. For the A-FNS, back streaming of Li vapor from the windowless free surface of the Li target is a concern. In addition, widely different vacuum pressure must be maintained between the accelerator system and the target system. This paper shows the detailed design of the A-FNS HEBT section regarding these considerations.

Supervisor watchdog circuit to monitor an accelerator beam and control the safety interlock system

A supervisor watchdog circuit was developed to both monitor the dose and temperature at an accelerator beamline and provide signals to the safety interlock system of the accelerator. The implementation involved a D type flip-flop and subsequent logic gates to monitor the input and output signal states. It used a series of LEDs to inform the user about the state of the system and to enable identification of issues causing the beamline to shut down. The design allowed for a manual circuit restart to be performed to continue signal monitoring and accelerator operation. The supervisor watchdog circuit was installed at the tandem accelerator of the Reactor Materials Testing Laboratory at Queen’s University to monitor the beam properties during nuclear materials irradiation experiments. The scope for future improvements of the circuit such as automatic circuit restart in case of power fluctuations and addition of new signals is discussed.

Monitoring linear accelerator beam with daily quality assurance phantom

This paper aims to analyze the output constancy of a medical linear accelerator using PTW, and to study the suitability as a daily quality assurance device. It is assumed that the device is sensitive enough to detect minor variations in central axis beam, flatness, symmetry, and beam quality factor. PTW, QUICKCHECKwebline is the most efficient wireless device used in daily quality assurance. The measurements of output doses of photons ( 6MV and 15 MV) and electrons (6,9,12, and 15MeV) from a medical linear accelerator before the daily treatment have been graphically analyzed. This study assures the output stability of Varian Clinac iX 2100 CD linear accelerator at Bhaktapur Cancer Hospital, Bhaktapur, Nepal. The beam flatness, symmetry, beam quality factor, and central axis of photon and electron beam have been analyzed for 10x10cm2 and 20x20cm2 field size in separate ways. Among the measurements, observed parameters lie under the tolerance limit as recommended by American Association of Physicists in Medicine viz. ±3%. The outcomes of the measurements are in the acceptable range for the treatment procedure of patients.

Topology Optimization Using a Normalized Gaussian Network of Iron Yoke for Magnetic Field Design of an Accelerator Superconducting Magnet

Field quality in the order of 10 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{-4}$</tex-math></inline-formula> is required for a superconducting dipole magnet to keep the beam stable in an accelerator. An iron yoke usually is employed to enhance the magnetic field and reduce the fringe field. As the superconducting magnet provides a field that is higher than 2 T, the field quality is distorted by the saturation effect of the iron yoke during the beam acceleration. Field tuning holes are adopted to the iron yoke to adjust the magnetic flux so as to keep the field error variation flat in the region from the injection field to the top field. It is time costly in terms of computing to determine the initial shape and search for the best solution that satisfies design requirements. This paper presents a topology optimization method using a non-dominated sorting genetic algorithm for the iron yoke design of an accelerator superconducting magnet. The shape of the iron yoke is represented by using the normalized Gaussian network to achieve smoothness of the material distribution. This method is applied to a superconducting bending magnet for a compact heavy-ion synchrotron in which the field errors are required to be lower than 2.5 unit and 3.5 unit at the point of injection field and the top field, respectively. As a result, a smooth shape of the iron yoke is obtained by this method; both field error at the top field and the field error variation are mitigated by the method.

Cascaded solenoid acceleration of vortex laser-driven collimated proton beam

Efficient cascaded proton acceleration driven by an intense Laguerre–Gaussian (LG) laser is realized in combined three-dimensional particle-in-cell simulations and CST STUDIO SUITE (CST) simulations. CST simulations show that there is no divergent force component in the transverse direction in the coil center. Therefore, the collimated proton beam driven by the LG laser in the first stage benefits from the uniform beam acceleration in the second stage. By contrast, the proton beam with larger divergence disperses to the outside of the coil because of the divergent force near the coil wire in the Gaussian laser case. Finally, a quasi-monoenergetic proton beam with a higher flux is generated by the LG laser, which is much better than the Gaussian laser case. The obtained proton beam can potentially be used in some special applications, such as proton radiography, fast ignition of fusion targets, biomedical applications, and production of warm dense matter.

Testing high-resolution transverse profile monitors by measuring the dependence of the electron beam size on the beam energy at SwissFEL

Transverse profile monitors are essential devices to characterize particle beams in accelerators. Here, we present an improved design of beam profile monitors at SwissFEL that combines the use of high-quality filters and dynamic focusing. We reconstruct the profile monitor resolution in a gentle way by measuring the electron beam size for different energies. The results show a significant improvement of the new design compared to the previous version, from 20 to 14 µm.

Numerical Simulations of the Acceleration of Fast Protons and of the Excitation of Nuclear Reactions 11B(p, 3a) and 11B(p, n)C11 at the Intensities of Picosecond Laser Radiation in the Range 1018-1019 W/cm2

Results of numerical simulations for acceleration of proton beams at the irradiation of Al target by a superintense laser pulse are presented. There is a good agreement with the experimental data in a broad range of laser intensities from I = 1018 W/cm2 to I = 1019 W/cm2 at the fixed laser pulse duration. The obtained parameters of proton beams were used for calculation of the total yield of a particles and neutrons for the nuclear reactions 11B(p, 3a) and 11B(p, n)C11C at the collisions of proton beams with boron targets. It is shown that the number of a particles escaping boron target and arriving at track detectors is less than 5of the total amount of a particles, because the majority of these particles remain inside the target owing to ionization losses. The derived values of the yield ofparticles’ which arrive at detectors are in good agreement with the experimental data. We also calculate the total yield of neutrons in the reaction 11B(p, n)C11C. It is found that, at the intensity I = 1019 W/cm2 of the picosecond laser pulse, the yield is equal to Nn = 1.4 × 108 , this value is approximately of 3% of the total yield of a particles.

Radiation dosimetry for quality control of silicon wafer using electron beam

Dosimetry studies using electron beams were performed with energies of up to 3 MeV, 2mA with various trolley speeds on the silicon wafer. The silicon wafer came with diameters of 152.4 and 203.2 mm with a thickness of 0.5 mm. The irradiations were performed by utilising the EPS 3000 Cockcroft-Walton type 3.0 MeV, 90 kwatts electron beam (EB) accelerator. Plastic film dosimeter, cellulose triacetate (CTA) was used as a dosimeter with a UV-vis spectrophotometer as the readout system. The dose setting in this investigation was ~100 kGy for 152.4 mm diameter and ~160 kGy for 203.2 mm diameter, which was based on the requirements of the customer. The acceptable dose value was set (± 10%) for better performance of the silicon wafer. It was important to comply with the international standards protocol for dosimeters in radiation processing dosimetry. The results showed that the dose and temperature decreased with increasing the speed. The optimum dose for both diameter of wafers when irradiate at electron beam current of 2 mA and the voltage of 3 MeV is at speed of 0.89 m/min. Based on these studies, it was found that it is important to control the speed of the trolley as it affects the irradiation conditions (e.g., temperature and dose measurements).

Towards self-consistent modelling of negative ion beam acceleration

Neutral beams are a valuable option to provide heat and current drive to a magnetically confined plasma. In addition they can be used as a diagnostics for the positive ion temperature and, in case of nuclear fusion reactions, for the amount of helium ash. In the case of ITER, stringent requirements are set on the acceptable beam divergence and aiming in order to propagate such beams up to the tokamak itself. Besides the well-known dependence of the beamlet optics on the beam energy and perveance, other important features affecting the optics are the ion spatial and velocity distribution at the plasma boundary facing the extractor, the so-called plasma meniscus. In a caesiated negative ion source, this distribution is influenced both by the birth energy of the negative ions and by the ion transport in the plasma itself. In this work we use a test particle code to investigate the negative ion transport up to the plasma meniscus and we use a standard ray-tracing code to trace the test particles that reached the meniscus inside the electrostatic accelerator. The coupling of the two codes is iterated up to numerical convergence. By this procedure, the angular distribution of the accelerated particles is found to be much more similar to the experimental ones than the one obtained by simple ray-tracing simulations.

Dose Profiles Distribution of 6 MV Linear Accelerator Using Monte Carlo Code System for Optimum Treatment planning in Radiotherapy Department

Monte Carlo (MC) radiotherapy treatment planning has become practical in medical physics, particularly with the rapid development of computer technology. Requires detailed knowledge of linear medical accelerators (Linacs) beam radiation. In the present work the basic dosimetric properties of the 6-MV photon beam and the Varian Clinic 600CLinac were examined. The dosimetric features of interest are, the absorbed dose from the central axis, beam profiles, photon blockers, electron and positron, mean energy, spectral distribution, and isodose curves. Varian Clinic 600C Linac is simulated using the OMEGA BEAMnrc MC code system. Detailed spectra of phase space profiles of a photon beam with a field of view of 10 cm × 10 cm were modeled, simulated and finally analyzed using BEAMdp. The central axis depth dose curves, dose profiles and isodose curves for photon beams in the aqueous phantom were also recorded and analyzed using the DOSXYZnrc, STATDOSE and DOSXYZ_SHOW code. This study demonstrates that MC can generate phase space data files that can be used to generate accurate MC dose distributions for photon beams produced using a high-powered clinical linear accelerator in a water phantom or in patients for radiotherapy.

Development of a single-ended magnetic alloy loaded cavity in the Japan Proton Accelerator Research Complex rapid cycling synchrotron

Abstract The Japan Proton Accelerator Research Complex (J-PARC) Rapid Cycling Synchrotron (RCS) employs magnetic alloy (MA) loaded cavities. We realize multi-harmonic rf driving and beam-loading compensation owing to the broadband characteristics of the MA. The currently installed cavity is the conventional type, which is designed to be driven by tube amplifiers in a push–pull operation. The push–pull operation has some advantages, i.e., suppressing a higher harmonic distortion without the beam acceleration and shortening the cavity length. However, a disadvantage arises at the high intensity beam acceleration where the multi-harmonic rf driving causes a severe imbalance of the anode voltage swing and restricts the tube operation. Although we have achieved an acceleration for the design beam power of 1 MW, the imbalance becomes an issue in increasing the beam power further. We have developed a single-ended MA cavity to avoid such difficulty. The cavity has no tube imbalance intrinsically and it is found that the power consumption to drive the cavity can be reduced compared with the conventional one.

Feedforward resonance control for the European X-ray free electron laser high duty cycle upgrade

The High Duty Cycle (HDC) upgrade is a proposed improvement to the existing European X-ray Free Electron Laser (EuXFEL) to extend the pulsed RF duty factor from the actual value of around 1% to more than 5% up to Continuous Wave (CW). To implement this upgrade, the loaded quality factor (QL) of the superconducting cavities will increase by more than one order of magnitude. This will result in shrinking the cavity bandwidth to values as low as a few Hertz. Since the Lorentz Force Detuning (LFD) experienced during the accelerating field buildup is of hundreds of Hertz, the Low-Level RF (LLRF) system has to accurately track and control the cavity resonance frequency to obtain the desired accelerating gradient. Moreover, ponderomotive instabilities have to be suppressed to achieve stability during beam acceleration. Since LFD is a repetitive disturbance in cavity frequency, the correction to its effects can be implemented as a feedforward compensation on the piezoelectric tuners of the cavity. Initial results on the simulation of feedforward resonance control in the HDC regime are discussed in this proceeding.

Microwave ion source with dual helical antenna for diagnostics neutral beam of ALBORZ tokamak

An efficient ion source of the diagnostic neutral beam injection (DNBI) is designed and simulated for Alborz Tokamak, based on the microwave plasma source. The diagnostic neutral beam is designed for use in some diagnostics system such as charge-exchange recombination spectroscopy (CXRS), Rutherford Scattering (RS), and Motional Stark Effect (MSE) of Alborz Tokamak. In this work, a new helical antenna is designed and simulated for a microwave plasma source, to reach a plasma density of order8.23×1017m−3. The microwave plasma source is employed by the high-efficient ion beam accelerator. In this simulation, three-electrodes in different potentials of 20 kV, −2 kV, and grounded respectively, are used as extraction system of the ion beam source. According to our design, nine apertures grids are considered for the accelerator system. The simulation results show that, the system can extract an ion beam with energy and current of 20 keV and 60 mA respectively. The extracted ion beam consists of nine beamlets, where the beam waist and the current of each of them are calculated about 3 mm and 6.5 mA, respectively. The results of this work indicate that the ion beam with minimum divergence angle of 32 mrad can be generated by the proposed ion beam source.

Influence of positive ions on the beamlet optics for negative-ion neutral beam injectors

Neutral beam injectors are based on the neutralization of ion beams accelerated at the desired energy. In the case of the ITER heating and diagnostic neutral beams, the target heating power translates into stringent requirements on the acceptable beamlet divergence and aiming to allow the beam to reach the fusion plasma. The beamlets composing the accelerated beam are experimentally found to feature a transverse velocity distribution exhibiting two Gaussian components: the well-focused one is referred to as the core component while the rest of the beam, the halo, describes beam particles with much worse optics. The codes that simulate beam extraction and acceleration usually assume that the negative ions move towards the plasma meniscus with a laminar flow (no transverse velocity) or that the transverse velocity distribution can be modelled as a Maxwellian and that the current density is uniformly illuminating the meniscus; under such approximations, the presence of highly divergent components cannot be explained. In this work, we develop a simple test-particle tracing code with Monte Carlo collisions, named ICARO (for Ions Coming Around), to study the transport of negative ions in the extraction region and derive the spatial and velocity distribution of the negative ions at the meniscus (i.e. the plasma boundary where a beamlet is extracted). In particular, the origin of the beamlet halo and its dependence on the source parameters are discussed, highlighting as a key parameter the energy distribution of positive ions in the source plasma.

Improved calibration of rf cavities for relativistic electron beams: Effects of secondary corrections and experimental verification

In the aspect of longitudinal beam bunching, the bunching strength can be controlled by the rf cavity phase and voltage. However, these machine parameters are different from those that interact with the beam itself. In order to gain control of the beam-cavity interaction, cavity calibration must be performed. Furthermore, it relies on fitting the beam energy gain versus cavity phase to a calibration function. Under the conventional assumption of relativistic beam conditions, the calibration function is a first harmonic sinusoidal function (a sinusoidal function with a period of $2\ensuremath{\pi}$). However, this expression is insufficient for a high-voltage bunching cavity. Due to beam acceleration inside the cavity, an energy bias and a second harmonic function should be included to modify the conventional calibration function, even for a relativistic electron beam. In this paper, we will derive this modification and provide a comparison to both the Coherent Electron Cooling Experiment and the impact-t simulation, respectively.