Beam Optics Study Research Articles

Beam Optics Study during Long-Pulse MeV-Class Beam Operation for the ITER HNB

Neutral beam injectors for ITER require the beam divergence to be less than 7 mrad for both D− and H− negative ion beams. The time evolution of beam optics parameters of ITER-relevant high intensity has not been well understood due to the material capabilities of heat load. In this study, the time evolution of beam divergence has been successfully observed with the ITER-relevant perveance beam parameter for 0.5 MeV and 100 seconds pulse. For this purpose, a beam monitoring system based on a visible camera, which has been newly developed and installed in the MeV Test Facility, is used. As a result of this experiment, it is experimentally found that the time evolution of beam divergence exists even if the Iacc and heat load to beam dump are stable. To reduce the time evolution of beam optics, the feed-back control of Iext is under development in order to suppress the variation of conditions in the ion source.

Study of coil configuration and local optics effects for the GaToroid ion gantry design

GaToroid, a novel gantry configuration for hadron therapy, is based on superconducting coils that generate a toroidal magnetic field to deliver the beam to the tumour location. Designing the complex GaToroid coils requires careful consideration of the local beam optical effects. We present a Python-based tool for charged particle transport in complex electromagnetic fields. The code implements fast tracking in arbitrary three-dimensional field maps, and it does not require a definition of specific or regular reference trajectories, as is generally the case for accelerator physics codes. The tool was used to characterise the beam behaviour inside the GaToroid system: to automatically determine the reference trajectories in the symmetry plane and analyse three-dimensional beam dynamics around these trajectories. Beam optical parameters in the field region were compared for various magnetic configurations of GaToroid. This paper introduces the new tracker and shows the benchmarking results. Furthermore, first-order beam optics studies for different arrangements demonstrate the main code features and serve for the design optimisation.

Beam optics studies for a novel gantry for hadron therapy

The design of smaller and less costly gantries for carbon ion particle therapy represents a major challenge to the diffusion of this treatment. Here we present the work done on the linear beam optics of possible gantry layouts, differing for geometry, momentum acceptance, and magnet technology, which share the use of combined function superconducting magnets with a bending field of 4 T. We performed parallel– to–point and point–to–point optics matching at different magnification factors to provide two different beam sizes at the isocenter. Moreover, we considered the orbit distortion generated by magnet errors and we introduced beam position monitors and correctors. The study, together with considerations on the criteria for comparison, is the basis for the design of a novel and compact gantry for hadrontherapy.

Beam optics study for a potential VHEE beam delivery system

VHEE (Very High Energy Electron) therapy can be superior to conventional radiotherapy for the treatment of deep seated tumours, whilst not necessarily requiring the space and cost of proton or heavy ion facilities. Developments in high gradient RF technology have allowed electrons to be accelerated to VHEE energies in a compact space, meaning that treatment could be possible with a shorter linac. A crucial component of VHEE treatment is the transfer of the beam from accelerator to patient. This is required to magnify the beam to cover the transverse extent of the tumour, whilst ensuring a uniform beam distribution. Two principle methodologies for the design of a compact transfer line are presented. The first of these is based upon a quadrupole lattice and optical magnification of beam size. A minimisation algorithm is used to enforce certain criteria on the beam distribution at the patient, defining the lattice through an automated routine. Separately, a dual scattering-foil based system is also presented, which uses similar algorithms for the optimisation of the foil geometry in order to achieve the desired beam shape at the patient location.

Study of beamlets extracted from a multi-aperture and five-stage acceleration system.

A beam optics study using the ITER-relevant high intense negative ion beams, such as 1MeV, 200 A/m2, has been performed experimentally and analytically using a multi-aperture and five-stage accelerator. Initially, multi-beamlets generated from this accelerator were deflected in various directions due to the magnetic field and space charge repulsion between beams and showed various divergences. These had limited the pulse length and the beam energy. Compensation methods of the beamlet deflections have worked effectively and contributed to achieving the ITER requirement, the divergence angle of <7 mrad, and the deflection angle of <1 mrad for 1MeV beam. The beam pulse has been gradually extended from 1 to 100s and is now going to a longer pulse based on these results. One of the remaining issues is to understand and suppress peripheral components of the beam, namely, the halo, and to reduce the local heat loads observed around the aperture edge. This halo component has been successfully distinguished from the beam core by using a newly developed beam emittance measurement system for high intense beams. By combining this measured beam emittance and the beam simulation, it was clarified for the first time that the halo components are generated in an area of 1mm width from the aperture edge.

Supervised learning-based reconstruction of magnet errors in circular accelerators

Magnetic field errors and misalignments cause optics perturbations, which can lead to machine safety issues and performance degradation. The correlation between magnetic errors and deviations of the measured optics functions from design can be used in order to build supervised learning models able to predict magnetic errors directly from a selection of measured optics observables. Extending the knowledge of errors in individual magnets offers potential improvements of beam control by including this information into optics models and corrections computation. Besides, we also present a technique for denoising and reconstruction of measurements data, based on autoencoder neural networks and linear regression. We investigate the usefulness of supervised machine learning algorithms for beam optics studies in a circular accelerator such as the LHC, for which the presented method has been applied in simulated environment, as well as on experimental data.

Long-pulse diagnostic calorimeter for the negative ion source testbed BATMAN upgrade.

The RF-driven negative ion source testbed BATMAN upgrade is being developed at IPP Garching in the framework of the ion source development for ITER and DEMO neutral beam injection systems. The testbed has recently been enhanced to allow for steady state operation with a focus on beam optics studies. The previous titanium sublimation pumps and inertial calorimeter limited the beam pulse length to about 6s every 3min. The upgrade comprises a long-pulse compatible, actively cooled diagnostic calorimeter. This has been designed and is currently being manufactured to substitute the inertially cooled calorimeter that has limited diagnostic capabilities. The new diagnostic calorimeter consists of a copper plate with dimensions of 910 × 660 × 25mm3 placed about 2m from the ion source extraction grids, and through a novel solution, it will provide a 2D profile of beam power density with a 20mm spatial resolution. Water flowing through cooling channels embedded in the copper plate will actively cool the calorimeter, which is loaded with about 160 kW beam power at ITER-relevant current density, but 45 kV acceleration. A fraction of the beam will pass through many small apertures (ø2mm) positioned in the calorimeter plate and will be collected by thin (0.2mm) copper foils attached to the calorimeter back side. Evaluation of power density will be performed by measuring the temperature of the heat flux foils with a high-resolution infrared camera observing the calorimeter from the back side and calibrated by thermocouples.

Beam optics of a superconducting proton-therapy gantry with a large momentum acceptance

In proton therapy, the last part of the beam transport system is installed on a rotatable gantry, so that the beam can be aimed at the tumor from different angles. Since such a gantry system consists of many dipole and quadrupole magnets, it is typically a 100–200 tons device of more than 10 m in diameter. The use of superconducting (SC) magnets for proton therapy allows gantries to be significantly lighter and potentially smaller, which is attractive for this medical application. In addition to that, SC combined function magnets enable beam optics with a very large momentum acceptance. The latter can be advantageous for patient treatment, since the irradiation time can then be significantly reduced by avoiding magnet current changes. To design such an achromatic system, we performed precise high-order calculations. To reach the required accuracy and to check consistency of the obtained results, we have used different simulation tools in our iterative design approach. Here, we will describe our beam optics calculations in the code COSY Infinity and particle tracking using OPAL (open source software from PSI) in 3D field maps obtained from detailed magnet calculations performed in Opera. Our method has shown to be advantageous in a complicated beam optics study and it reduces the risk of systematic errors in a design.

The “Physics Beyond Colliders” Projects for the CERN M2 Beam

Physics Beyond Colliders is an exploratory study aimed at exploiting the full scientific potential of CERN’s accelerator complex up to 2040 and its scientific infrastructure through projects complementary to the existing and possible future colliders. Within the Conventional Beam Working Group (CBWG), several projects for the M2 beam line in the CERN North Area were proposed, such as a successor for the COMPASS experiment, a muon programme for NA64 dark sector physics, and the MuonE proposal aiming at investigating the hadronic contribution to the vacuum polarisation. We present integration and beam optics studies for 100 – 160 GeV/c muon beams as well as an outlook for improvements on hadron beams, which include RFseparated options and low-energy antiproton beams and radiation studies for high intensity beams. In addition, necessary beam instrumentation upgrades for beam particle identification and momentum measurements are discussed.

Beam optics studies and lattice design of the 1 GeV H- injector linac for ISNS

Abstract In this paper, we discuss a general methodology to make a compact design of the 1 GeV, 1 MW H- superconducting injector linac for the Indian Spallation Neutron Source (ISNS) project, by following the n o n - e q u i p a r t i t i o n e d design approach, where the emittance growth of the beam is controlled through appropriate adjustment of the strength of lattice elements. Analytical studies of the stability of mismatched envelope oscillations have been performed for a three dimensional beam bunch, which, to the best of our knowledge, is not reported earlier. A rigorous beam halo analysis based on Particle Core Model (PCM) is also presented, considering the actual periodicity of the ISNS lattice, in order to estimate the maximum radial extent of the halo particle.

Performance validation of the iron-dominated, normal-conducting 45°dipole magnets in the ReA3 HEBT line at NSCL, MSU

Abstract The Re-Accelerator (ReA3) facility at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University (MSU) delivers rare isotope and stable beams ranging from 0.3 MeV/u to 6 MeV/u to experimental end stations. The High Energy Beam Transport (HEBT) line into the ReA3 experimental hall houses several quadrupole magnets, dipole magnets, and combined function horizontal and vertical corrector magnets. All of these are iron-dominated, resistive type magnets. This paper describes the magnetic performance of 45°dipole magnets installed in both the vertical and horizontal section of the ReA3 beamline. The computed field map and the derived data provide a reference for the operational setting of the magnet and input for the beam optics study. The field measured by both Hall and NMR probes agrees well with the calculations suggesting that the magnet performance meets the design specification.

Beam optics study for energy selection system of SC200 superconducting proton cyclotron

To meet the demands on proton therapy in Russia and China, JINR and ASIPP have started to develop a proton therapy facility based on an isochronous superconducting proton accelerator. A 200 MeV/500 nA proton beam will be extracted from the SC200 superconducting proton cyclotron. Due to the energy of the cyclotron being fixed, an energy selection system (ESS) is employed to degrade such energy in order to match the particle energy to a shallower depth. In this article, calculation of beam optics, analysis of beam transmission, and correction of orbit distortion are presented. Studies show that the main factors influencing transmission efficiency of the SC200 ESS beamline are the degrader, collimator, slit, vacuum system, beam diagnostic system, and trajectory correction system. Through the beam optics study, the designed ESS beamline can provide 70–200 MeV proton beam to a treatment room, with a maximum emittance of 24 π mm mrad. Also, the controllable momentum spread ranges from 0.1 to 1.0%, which is equivalent to an energy spread from 0.193 to 1.93%. The transmission efficiency about 0.204% can be obtained when the emittance is 24 π mm mrad with an energy spread of ± 0.6%.

A beam optics study of a modular multi-source X-ray tube for novel computed tomography applications

A modular implementation of a scanning multi-source X-ray tube is designed for the increasing number of multi-source imaging applications in computed tomography (CT). An electron beam array coupled with an oscillating magnetic deflector is proposed as a means for producing an X-ray focal spot at any position along a line. The preliminary multi-source model includes three thermionic electron guns that are deflected in tandem by a slowly varying magnetic field and pulsed according to a scanning sequence that is dependent on the intended imaging application. Particle tracking simulations with particle dynamics analysis software demonstrate that three 100 keV electron beams are laterally swept a combined distance of 15 cm over a stationary target with an oscillating magnetic field of 102 G perpendicular to the beam axis. Beam modulation is accomplished using 25 μs pulse widths to a grid electrode with a reverse gate bias of −500 V and an extraction voltage of +1000 V. Projected focal spot diameters are approximately 1 mm for 138 mA electron beams and the stationary target stays within thermal limits for the 14 kW module. This concept could be used as a research platform for investigating high-speed stationary CT scanners, for lowering dose with virtual fan beam formation, for reducing scatter radiation in cone-beam CT, or for other industrial applications.

Beam optics study of a negative ion source for neutral beam injection application at ASIPP

In order to study the generation and extraction of negative ions for neutral beam injection application, a negative ion source is being designed and constructed at Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP). Through a four electrode grids system inside the accelerator, a negative ion beam will be extracted and accelerated up to −60kV on a reduced scale extraction area of 12×50cm2 (the area of PG apertures is 185cm2). The beam optics is a key issue for the accelerator design, and greatly determine the source experimental performance in term of beam current, heat load on the grid, beam divergence, and so on. In this paper, the trajectories of electrons and negative ions were simulated in the electrode grids of the negative ion source. The filter capability of electron deflection magnet on the co-extracted electrons is evaluated and confirmed. The negative ion beam optics was designed according to the calculated results of beam divergence and beam radius along the beamlet in different acceleration voltages. The deflection effect of the electron deflection magnet on the negative ion beam was investigated in the single beamlet case and multi-beamlets case.

Orbit error correction on the high energy beam transport line at the KHIMA accelerator system

For the purpose of treatment of various cancer and medical research, the synchrotron based medical machine under the Korea Heavy Ion Medical Accelerator (KHIMA) project have been conducted and is going to treat the patient at the beginning of 2018. The KHIMA synchrotron is designed to accelerate and extract the carbon ion (proton) beam with various energy range, 110 up to 430 MeV/u (60 up to 230 MeV). A lattice design and beam optics studies for the High Energy Beam Transport (HEBT) line at the KHIMA accelerator system have been carried out with WinAgile and the MAD-X codes. Because the magnetic eld errors and the mis-alignments introduce to the deviations from the design parameters, these error sources should be treated explicitly and the sensitivity of the machine's lattice to di erent individual error sources is considered. Various types of errors which are static and dynamic one have been taken into account and have been consequentially corrected with a dedicated correction algorithm by using the MAD-X program. As a result, the tolerances for the diverse error contributions have been speci ed for the dedicated lattice components in the whole HEBT lines.

1 MeV, 10 kW DC electron accelerator for industrial applications

Several modern applications of radiation processing like medical sterilization, rubber vulcanization, polymerization, cross-linking and pollution control from thermal power stations etc. require D.C. electron accelerators of energy ranging from a few hundred keVs to few MeVs and power from a few kilowatts to hundreds of kilowatts. To match these requirements, a 3 MeV, 30 kW DC electron linac has been developed at BARC, Mumbai and current operational experience of 1 MeV, 10 kW beam power will be described in this paper. The LINAC composed mainly of Electron Gun, Accelerating Tubes, Magnets, High Voltage source and provides 10 kW beam power at the Ti beam window stably after the scanning section. The control of the LINAC is fully automated. Here Beam Optics study is carried out to reach the preferential parameters of Accelerating as well as optical elements. Beam trials have been conducted to find out the suitable operation parameters of the system.

Design and Manufacture of a Main Beam Quadrupole Model for CLIC

The Main Beam Quadrupole (MBQ) magnets represent one of the most populated families of Compact Linear Collider (CLIC) magnets. In total more than 4000 units of 4 different types with the same bore radius of 5 mm and field gradient of 200 T/m but with different magnetic length are needed. An extremely high precision and mechanical stability are necessary in order to fulfill the magnetic and stabilization requirements as defined in the beam optics studies. A magnet design has been proposed and several quadrupole prototypes of different length have been produced targeting a high mechanical precision. Magnetic calculation, constructional design and the first test results are presented.

Positive ion extraction from plasma source and its application in fusion research

Neutral Beam Injection (NBI) is well established technique for heating tokamak plasma and is used in all fusion research programs [1–2]. In our Steady state Superconducting Tokamak (SST) machine [3], neutral hydrogen beam power of 0.5 MW at 30 kV is required to raise plasma ion temperature of ∼1 keV. Future upgrade of the SST will require 1.7 MW of Ho at 55 kV. To fulfill this requirement, an ion extractor system (heart of any NBI system) has been designed to extract 35A H+ beam current at 30 kV and of 90 A at 55 kV respectively [4]. In this paper, we have described the physics and ion beam optics study for an ion extraction system suitable for above mentioned long dynamic range of acceleration voltage. The ion beam optics simulation result is used as an input to the engineering design. After fabrication, its performance test has been done. The experimental results are in very good agreement with beam optics simulation.

Design of an ion extractor system for a prototype ion source experiment for SST-1 neutral beam injector

An ion extractor system has been designed for the steady state superconducting tokamak (SST-1) neutral beam injector (NBI) for an experiment using a prototype ion source with fully integrated regulated high voltage power supply (RHVPS) and data acquisition and control system (DACS) developed at Institute for Plasma Research (IPR) to obtain experience of NB operation. The extractor system is capable of extracting positive hydrogen ion beam of ∼10 A current at ∼20 kV. This paper presents the beam optics study for detailed design of an ion extraction system which could meet this requirement. It consists of 3 grid accel– decel system, each of the grid has 217 straight cylindrical holes of 8 mm diameter. Grids are placed on a specially designed G-10 block; a fiber reinforc plastic (FRP) isolator of outer diameter of 820 mm and 50 mm thickness. Provisions are made for supplying high voltage to the grid system through the embedded feed-throughs. Extractor system has been fabricated, mounted on the SST-1 neutral beam injector and has extracted positive hydrogen ion beam of 4 A at 20 kV till now.

Magnetic fields and beam optics studies of a 250 MeV superconducting proton radiotherapy cyclotron

A 250 MeV superconducting cyclotron for the proton radiation therapy was designed at the Michigan State University (MSU) for use at the Paul Scherrer Institut. This work was based on the conceptual design carried out at the MSU in 1994. The previous design was refined to finalize the magnet configuration and to optimally arrange cyclotron elements for the actual construction. The spiral angle of the pole was reduced, the new hill-edges and valley shims being introduced. The magnetic fields were highly isochronized using a least square fitting routine involving a schematic shimming scheme. The resulting reference field was adequate for the elaborate study of beam optics. The optics simulation predicted that extraction efficiency of above 80% was achievable for a beam with the initial phase width of 20°. The vertical deflector was investigated located in the central region to control the beam intensity with tracking of beam phase spaces. Some measurement results for the constructed cyclotron were found in a good agreement with those of the optics study.