Cyclotron Magnetic Field Research Articles

Central Region of the С-250 Cyclotron

The peculiarities of modeling of the central region and hydrogen ion beam dynamics for the cyclotron C-250 designed for operation in a wide energy control range of 30-250 MeV are considered. On the basis of modeling of ion beam dynamics in the energy control range, the optimal configuration of the central region of the accelerating system of the C-250 cyclotron is determined. The developed central region fulfills the requirements to ensure sufficient vertical focusing of particles by the electric field while capturing the beam in a wide phase range. The deviation of the centers ofparticle orbits from the geometric center of the cyclotron is 2-3 mm for the whole range of regulation of the cyclotron magnetic field.

Results of Reconstruction of U400M Cyclotron Magnetic Structure

U400M isochronous cyclotron was create on the base of U300 classic cyclotron and is under operation at FLNR, JINR since 1996. U400M cyclotron is intended for accelerating the ion beams with A/Z= 2.286 – 9 to energy W = 80 – 6 MeV/nucl. Cyclotron have H-type main magnet with 4-meter pole diameter and 4 pairs of spiral type sectors. In 2022 year, the reconstruction of cyclotron magnetic structure was held on. The reconstruction included the replacement of magnet main coil, mapping and correction of cyclotron magnetic field. In the frame of the mapping, the magnetic field was corrected to improve its average radial distribution and to compensate the first harmonic. For cyclotron magnetic field mapping the automatic measurement system, based on 14 Hall probes, was used.

Magnetic field of DECY-13 from numerical extrapolation of the measurement result for beam trajectory simulations in central region

DECY-13 cyclotron is a radioisotope production cyclotron developed by PSTA. In a cyclotron, it is important to understand magnetic fields and electric field distribution for the proton beam trajectories. This paper describes the distribution of the magnetic field from the experimental measurement. Magnetic field has been converted into 3-dimensional data by extrapolation. Data validation was done by comparing the Opera3D simulation and used in simulations of the beam trajectories. Simulations were carried out by using Scilab 5.4.1 and the Runge-Kutta (RK4) approximation method. The parameters used in DECY-13 cyclotron were 40 kV Dee voltage with a radiofrequency (RF) 77.66 MHz and a fourth-harmonics type. The calculations and simulations result showed the beam could pass through the puller at the distance of the ion source with a puller was 6 mm and the optimum distance of 4 mm. The largest difference in error at z = 6 mm was 0.023 T of the average magnetic field 1.275 T. The phase acceptance in horizontal and vertical motion in the central region was about 38 Degrees from -19° to 19°. This experimental and simulation data could be used as a reference for DeCY-13 cyclotron magnetic and electric field distribution profiles.

Tuning of cyclotron resonant frequency and magnetic field of medical cyclotron

The high-frequency resonant cavity is affected by factors such as beam load, gravity and heat loss caused by cavity deformation during the actual operation of the medical cyclotron. The resonant frequency will shift to a certain extent, resulting in the high-frequency operation frequency varying with the resonant frequency of the resonator cavity. In order to meet the requirements for isochronous acceleration, the magnetic field strength should also be changed correspondingly when the high-frequency operation frequency changes, that is, the magnitude of the magnet current needs changing accordingly, so that the particle cyclotron frequency matches the high-frequency resonant frequency to overcome the sliding phase. Firstly, the static magnetic field model is established by finite element simulation software to simulate the average magnetic field of cyclotron under different magnet currents. Then the relationship between the magnetic field and the resonant frequency is theoretically analyzed. Finally, the relationship between the magnet current and the resonant frequency is obtained when the magnet current varies in a small interval. According to the optimal magnet current corresponding to different resonance frequencies, the automatic frequency tracking of magnet current is completed. In the case of ensuring the maximum carbon film beam, the optimal magnet current corresponding to different resonance frequencies is obtained, which makes the theory validated. According to the relationship, the magnet current is automatically adjusted, which overcomes the slip phase and ensures the stable output of the Faraday beam. The method enables the magnet current to be quickly and accurately find and track the cavity frequency, overcomes the slip phase caused by the frequency offset, and completes the stable output of the beam.

Reconstruction of the U400M Cyclotron Complex: Influence of Parameters of the New U400M Electromagnet Winding on the Cyclotron Magnetic Field

The U400M cyclotron complex has been operating at FLNR, JINR, since 1992. At present, its reconstruction is under preparation, which includes replacing the main winding of the cyclotron electromagnet. This paper considers the results of three-dimensional calculations demonstrating the influence of the coil position on the main and fringe magnetic fields of the cyclotron.

Study on deposition of Al2O3 films by plasma-assisted atomic layer with different plasma sources

In this paper, Al2O3 thin films are deposited on a hydrogen-terminated Si substrate by using two home-built electron cyclotron resonance (ECR) and magnetic field enhanced radio frequency plasma-assisted atomic layer deposition (PA-ALD) devices with Al(CH3)3 (trimethylaluminum, TMA) and oxygen plasma used as precursor and oxidant, respectively. The thickness, chemical composition, surface morphology and group reactions are characterized by in situ spectroscopic ellipsometer, x-ray photoelectric spectroscopy, atomic force microscopy, scanning electron microscopy, a high-resolution transmission electron microscope and in situ mass spectrometry (MS), respectively. We obtain that both ECR PA-ALD and the magnetic field enhanced PA-ALD can deposit thin films with high density, high purity, and uniformity at a high deposition rate. MS analysis reveals that the Al2O3 deposition reactions are not simple reactions between TMA and oxygen plasma to produce alumina, water and carbon dioxide. In fact, acetylene, carbon monoxide and some other by-products also appear in the exhaustion gas. In addition, the presence of bias voltage has a certain effect on the deposition rate and surface morphology of films, which may be attributed to the presence of bias voltage controlling the plasma energy and density. We conclude that both plasma sources have a different deposition mechanism, which is much more complicated than expected.

Slow Current Discharges and Quenching of the MSU Superconducting Cyclotron Gas-Stopper Magnet

The Michigan State University cyclotron gas-stopper magnet generates a strong focusing cyclotron magnetic field that permits an ion beam of up to 100 MeV/u to enter the magnet and have most of its energy reduced by low-pressure helium gas. The magnet has two superconducting coil cryostats mounted within warm iron poles and a warm split iron return yoke. The coils are connected in series using room temperature cables. The peak magnet stored energy is 3.5 MJ. The magnet has been tested to its full operating current of 180 A. During tests, the magnet discharged inadvertently three times. Two low-current discharges caused the magnet current to decay through the power supply system. A discharge at 180 A quenched the magnet, because the quench protection system caused the magnet to discharge across a 1.25-Ω resistor. This fired the cold quench protection diodes within the cryostat, quenching both coils. The magnetic field in the gap was measured as the magnet discharged. For the two low-current discharges, the magnetic field followed the current in the external magnet circuit. During a quench, the magnetic field decay rate was much slower than the external circuit current decay rate.

Minimization of the measurement errors induced by the cyclotron magnetic field measurement system

Systematic errors caused by the deficiencies of the measurement equipment are occurring relatively often in the engineering practice. The magnetic field measurement system of the VINCY Cyclotron has been designed well; however, due to the practical limitations in the machining process fabrication errors are imminent. We present our experiences with the produced measurement system and the techniques used for the detection and correction of errors. A change in the measuring protocol is suggested in order to overcome otherwise unavoidable errors caused by measuring system machining imperfections.

Calculation and Analysis of a Self-Shielded 13-MeV Cyclotron Magnetic Field

A self-shielded four-sector 13-MeV cyclotron magnet has been designed for positron-emission tomography (PET). Compared with the previous one, which was built for the first time in Korea in 2003, this newly designed cyclotron is superior because it is compact and the stray field is reduced. An isochronous field was achieved by placing several side shims and by slightly varying the vertical magnet gap along the radius of the cyclotron. We show that the phase excursion is maintained within ±5 rf degrees and that the vertical and the horizontal focusing frequencies are suciently away from harmful structural resonances. The expected total power consumption, which is less than 15 kW, is moderate.

DC-60 heavy ion cyclotron complex: The first beams and project parameters

The construction of the DC-60 Heavy Ion Cyclotron for the Interdisciplinary Scientific Research Complex (ISRC) in Astana started in early 2004. The cyclotron was manufactured and tested at the Flerov Laboratory of Nuclear Reactions (FLNR) in Dubna. The main units were delivered to Astana and assembled in the ISRC building in the summer of 2006. The cyclotron was turned on in September, 2006. The first heavy ion beams in the whole A/Z and energy ranges were accelerated and extracted in December, 2006.The complex, based on the DC-60 cyclotron, is intended for applied and fundamental research using accelerated heavy ion beams ranging from Carbon to Xenon with energies in the range of 0.34–1.77 MeV/nucleon, as well as for experiments on the channel of low energy ion beams, where the ion extraction voltage supplied by the ECR source reaches 25 kV. The energy variation of the accelerated ions is accomplished by changing the ion charge. The possibility of smoothly tuning the ion energy by ±30% of its nominal value can be seen by changing the cyclotron magnetic field. Within the framework of commissioning the DC-60 cyclotron, a number of experiments were carried out with accelerating charged particle beams in the main points of the working diagram The acceleration modes for Nitrogen, Argon, and Krypton (14N2+, 40Ar4+, 40Ar5+, 40Ar7+, 84Kr12+) ions on the 4th and 6th harmonics of RF accelerating voltage in the whole range of magnetic field variation were investigated. A Krypton accelerated ion beam (84Kr12+) with a current of up to 2 μA was extracted into the beam transport channel, matched, and transported to a technological facility for polymer film irradiation. An irradiation field with the required particle flux density and homogeneity was provided by 2 scanner magnets, and the experimental irradiation of polymer films was carried out. The operational modes, with magnetic fields corrected by radial correcting coils of cyclotron, were investigated.

Positron emission isotope production cyclotron in DLNP JINR (Status Report)

A C10-cyclotron for radioisotope production is under construction at the Dzhelepov Laboratory of Nuclear Problem, Joint Institute for Nuclear Research (DLNP JINR). It is a compact isochronous cyclotron for accelerating H− ions to the energy of about 10 MeV. The magnetic system, vacuum chamber and accelerating system is being built now. Results of the calculation and forming of the cyclotron magnetic field and the study of the beam dynamics from an ion source to an extraction system in calculated magnetic field are presented.

Automatic system for the mapping of the VINCY cyclotron magnetic field

The VINCY Cyclotron is the main part of the TESLA Accelerator Installation at the Vinca Institute of Nuclear Sciences in Belgrade. It is an isochroous cyclotron for the acceleration of both light and heavy ions. The pole of its magnet has the diameter of 2000 mm; its bending limit is 134 MeV, while its focusing limit is 73 MeV. This paper describes the magnetic field measurement system that has been used for the shimming of the VINCY Cyclotron magnet i.e., for precise shaping of its sectors and plugs. It is an automatic measurement system based on the Hall-probe that moves in the median plane between the poles of the magnet. We have used this system to obtain precise maps of the magnetic field for different operating regimes of the cyclotron needed in the process of shimming. The overall measurement uncertainty was estimated to be in the range of ?0.02%.

Calibration of the simulation model of the VINCY cyclotron magnet

The MERMAID program will be used to isochronise the nominal magnetic field of the VINCY Cyclotron. This program simulates the response, i. e. calculates the magnetic field, of a previously defined model of a magnet. The accuracy of 3D field calculation depends on the density of the grid points in the simulation model grid. The size of the VINCY Cyclotron and the maximum number of grid points in the XY plane limited by MERMAID define the maximumobtainable accuracy of field calculations. Comparisons of the field simulated with maximum obtainable accuracy with the magnetic field measured in the first phase of the VINCY Cyclotron magnetic field measurements campaign has shown that the difference between these two fields is not as small as required. Further decrease of the difference between these fields is obtained by the simulation model calibration, i. e. by adjusting the current through the main coils in the simulation model.

New inflector for axial injection in cyclotron

A new type of inflector for the system of axial injection of the cyclotron is presented. Similar to the commonly used spiral and hyperbolic inflectors, the reference particle in the new inflector moves on an electrostatic equipotential surface. The peculiarity is that the particle trajectory is a plane curve, despite the curling affect of a cyclotron magnetic field. The distribution of the inflector electric potential and the shape of the electrodes are expressed by exact analytical formulas. Due to the simple trajectory and analytical frame, the presented inflector may be simpler to use (and may be in its manufacturing) than the spiral inflector. The inflector is more compact as compared with the hyperbolic inflector.

Shape optimization of the magnetic channel of a superconducting cyclotron

In this paper, the optimization of the shape of the magnetic channel inside a superconducting cyclotron is performed. The objective is to ensure a proper shaping and reduction of the intensity of the cyclotron magnetic field so as to facilitate the extraction of the charged particles. The optimization problem is solved by following two different approaches: a genetic algorithm and a simulated annealing approach. The relative advantages of each of the methods employed for the optimization of the magnetic channel are discussed.

Analytic representation of cyclotron magnetic field

A model has been developed for the rapid but accurate calculation of the static magnetic field in the Chalk River cyclotron. The field is expressed in terms of elementary functions which can be handled efficiently in differential-algebra trajectory integrations. Maxwell's equations are satisfied exactly. Each of seven subdivisions of the superconducting coils is treated by a moment expansion about a central circle. Each pole is modeled as a uniformly magnetized semi-infinite prism. Monopoles and dipoles at the vertices of the polygonal pole faces correct for departures from the true pole shape. Uniform distributions of dipole strength along the edges of the pole-face polygons correct for the local inappropriateness of the assumption of uniform magnetization. The contributions of the yoke and of other relatively distant parts of the structure to the held in the region of particle acceleration are represented by low-order polynomials. Some of the source parameters are obtained by fitting to the measured values of B/sub z/ in the horizontal plane of symmetry.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Pressure surface distortion by applied ion cyclotron waves and magnetic field asymmetries

In magnetic confinement devices the pressure surfaces must obey the parallel current constraint. In a tandem mirror, nonquadrupole magnetic field components or ion cyclotron range of frequencies (ICRF) ponderomotive effects enter the parallel current equation in a nontrivial way. The extra terms cause a shift of the plasma column and/or distortion of the pressure surface shape. These effects are examined for three cases of interest: magnetic error fields due to misaligned coils, axial asymmetries in the quadrupole or solenoidal fields, and azimuthally asymmetric ponderomotive effects associated with applied ICRF waves. The ambipolar potential can compensate for asymmetries and permit lowest order isorrhopic equilibria in some cases, but if the passing density between cells is too small (np/na&amp;lt;rTa/eΦRc) this cannot occur and the flux surfaces of the cells disconnect.

Poloidal electric field generated by electron cyclotron heating in a collisional tokamak plasma

The poloidal electric field generated by electron heating in a collision dominated tokamak plasma is calculated by the adjoint method. The physical mechanism is elucidated as due to a combination of the Doppler shifted cyclotron resonance and magnetic field inhomogeneity. For uniform rf field on a flux surface, the normalized electrostatic potential is found to be much smaller than the inverse aspect ratio for realistic power levels.

Analysis of the magnetic field and studies of the beam dynamics for H − ions in the University of Manitoba cyclotron

Beam orbit dynamics investigations for H − ions in the completely redesigned central region of the University of Manitoba cyclotron were carried out. The methods and the results of these studies are presented along with an analysis of the cyclotron magnetic field that was previously mapped in 1984.

Zero degree neutron time-of-flight facility at RCNP

An outline of the 0° neutron time-of-flight facility at RCNP is briefly described. A technique has been developed for obtaining a narrow beam burst width by detuning the isochronous cyclotron magnetic field. An overall subnanosecond time resolution has been achieved for 50–80 MeV proton beams. Applications have been made to polarization transfer experiments for the (p, n) reaction at 0°.