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Lawrence, the creator of the cyclotron, also tried to bring the first color TV to American consumers. The story of his efforts reveals how the history of television was connected to physics and the military.

The article describes the experiments carried out during last years at the accelerator complex DC-60 of Astana branch of the INP (Nur-Sultan, Kazakhstan Republic), to provide intense ion beams of metals with the use of volatile organometallic compounds (Metal Ions from Volatile Compounds) – MIVOC. As a result of performed work for the first time at DC-60 cyclotron a beams of nickel, iron, silicon, cobalt, chromium, titanium, germanium and hafnium ions were produced.

Optimization of the central region of the DECY-13 cyclotron has been carried out. Optimization is done by changing the geometry or the configuration of the components of central region (puller and beam guide position). Different configurations result in different distributions of electric field. The amount of ejected particles from the central region will be different for different configurations. A parameter that can be used to see the number of ejected particles is the phase width, since the particle accelerating electric field oscillate with respect to time. The electric field distribution for this simulation is obtained from potential simulation of central region using electrostatic solver from OPERA3D software. One particle trajectory simulation was performed using the 4th order Runge Kutta written in Scilab, with the initial kinetic energy of the particle is set to be 3 eV. The results show that the configuration with a 1 mm shift of puller 2 and beam guide 2 to the negative x, y axis is the optimal configuration. This configuration provides a 34o phase width, precise trajectory through the puller gap and optimal axial motion of the particles. It is also known that 40 kV is the most optimal voltage to obtain the largest phase width.

The Centre for Accelerator Science and Technology (PSTA) will conduct an experiment for proton beam energy measurement of its cyclotron facility (DECY-13) using copper foil activation technique. This method generates neutron and gamma radiation. Thus, radiation shielding is required for safety provision. The previous work had investigated the radiation shielding for DECY-13 using analytical methods. However, it needs another method to verifiy its result. In this work, we had conducted particle transport simulation using the Particle and Heavy Ion Transport code System (PHITS) to validate the analytical methods. Based on simulation, to fulfil the safety criteria of maximum dose rate of 20 µSv/h at the distance of 300 cm, it needs 8 blocks of K500 concrete shielding with total thickness of 120 cm resulted in the dose rate of 19.1 µSv/h. This value is 99% matched the analytical methods (based on the previous investigation) of 121.19 cm. Thus, PHITS had successfully validated the analytical methods for investigating the radiation shielding of DECY-13 cyclotron.

Center for Accelerator Science and Technology is developing Indonesia first cyclotron prototype for radioisotope production. One of the crucial components of the cyclotron that is a magnet has been constructed. The constructed magnet needs to be shimmed to achieve the isochronous magnetic field so that the particles can reach their final energy. For this purpose, some pole shape modifications were performed. The magnetic field was measured using a 2D Cartesian coordinate mapping system and analyzed in the static orbit and accelerated orbit. The static equilibrium orbit analysis shows that the magnetic field close to the isochronous field with the phase shift ± 15 degrees. Meanwhile, the accelerated orbit analysis shows that the particle can reach the final energy event though there are some dense trajectories in some region.

Low pressure, low-temperature plasma (LTP) with a spatially varying transverse magnetic filter field configuration has a wide range of applications. In such devices, the magnetic field value is low enough that it magnetizes only the electrons and not the ions, and works as an electron filter by limiting the flux of hot electrons. Due to the gradient of the transverse magnetic filter field, the electron cyclotron frequencies are also changing with location and in some places it comes close to different collision frequencies. A parallel 2D-3V Particle-in-Cell Monte Carlo Collision (PIC MCC) kinetic model based code has been developed to study plasma transport in a negative ion source where a spatially varying transverse magnetic filter field is considered in a source geometry similar to that of ROBIN (RF Operated Beam source in INdia). Various collision dependent physical phenomena, having different time scales and length scales are studied. In this article, we are reporting instabilities, observed near the filter field region. It is also observed that the frequencies of those instabilities are close to some of the electronic and ionic collision frequencies which may create resonant phenomena in the magnetic filter region and influence the cross-field transport, and heating.

Electron cyclotron (EC) waves are studied in the Saturn’s magnetosphere. The method use of kinetic approach has been adopted toevaluate the dispersion relation, growth rate of the waves. We show the wave frequency is near the gyro frequency of the electron cyclotron wave they are right hand circularly polarized. The present study of the investigation is to examine the effect of parallel electric field (EII) in view of the observations in Saturn magnetosphere has been applied by Cassini. It is observed that the effect of increasing the Saturn’s radii (Rs) with parallel electric field is to decrease the growth/damping rate of the EC waves. The results are interpreted for the space plasma parameters appropriate to the Cassini of the Saturn’s magnetosphere plasma.

Electromagnetic ion cyclotron waves have been studied for relativistic ring distribution in the presence of parallel AC electric field by using the method of characteristic solutions and kinetic approach. The dispersion relation and the growth rate has been derived and calculated for magnetosphere of Saturn. The effect of AC frequency on the Doppler shifting frequency has been discussed. The new results have been explained for a ring distribution function rather than the bi-Maxwellian or loss cone distribution function. The effective parameters for the generation of EMIC waves are not only the temperature anisotropy but also the relativistic factor, AC field frequency, ratio of cold to warm particles number density which has been discussed in result and discussion section.

Radio frequency (RF) power in the ion cyclotron range of frequencies (ICRF) is one of the primary auxiliary heating techniques for Experimental Advanced Superconducting Tokamak (EAST). In this paper, we will present an overview of the main experimental results from recent campaign on EAST. 1) A dedicated experiment for more than 10MW operations has been carried out on EAST. The major aspects linked to the use of the EAST auxiliary heating systems: ICRF,LHCD and NBI are presented with emphasis on ICRF and LH. The challenges for ICRF coupling on EAST will be described at the low densities typically used for long pulse operation with lithium wall conditioning. 2)This paper also summarizes effects of ICRF power on LH coupling and modification of heat loads on EAST. 3) Co-current rotation driven by ICRF are observed in both L-mode and H-mode discharges. Co-current rotation can be generated by ICRF heating in LHCD plasma. Different rotation behavior observed in LHCD discharges. ICRF can also induce counter-current rotation in LHCD L-mode discharges. 4) A high-frequency magnetic probes (HFBs) system has been developed and successfully applied to detect ion cyclotron emission (ICE) in D-NBI injection experiments in the 2018 experimental campaign of EAST. ICE driven by fast D-NBI ions and fusion born ions are observed on EAST.5) In Hydrogen minority in Deuterium plasma, the interaction of fast wave and fast D-NBI ions is detected on EAST. Acceleration of fast D ions is confirmed by increased neutron yield.

64Cu is a cyclotron-produced radionuclide suitable for positron emission tomography (PET) and internal radiotherapy. We have been focused on 64Cu radioisotope due to its favorable nuclear characteristics (β+ emission, 18% and β− emission, 39%). Moreover, the electron capture (43%) implies Auger electron emission with high linear energy transfer in the targeted cells. Also, the 12.7 hours half-life allows a good uptake and distribution of the radiopharmaceuticals to obtain qualitative images with high contrast. The production of no-carrier-added 64Cu via the 64Ni(p,n)64Cu nuclear reaction using a variable energy cyclotron (TR-19, ACSI, Canada) was studied in our work involving the implementation of a fully automated solid target irradiation and processing system. In this paper we report the validation of the process for the automated production and purification of 64Cu produced in a variable energy (14-19 MeV) cyclotron, using a commercially available automated solid target system (ALCEO, Comecer S.p.A, Italy), comprising modules for electrodeposition, pneumatic transfer, irradiation unit, dissolving and purification. The obtained 64CuCl2 solution complies with the requirements of a radiopharmaceutical for medical applications. The process is to be translated for production of other copper radioisotopes of medical interest.

One of the performance limiting factors in Ion Cyclotron Range of Frequencies (ICRF) systems for thermonuclear fusion reactors is the voltage holding capability of the launchers. Increased voltage stand-off, hence power density of ICRF launchers, would be a desirable feature for future fusion reactors. This contribution showcases the design of IBEX (ICRF Breakdown EXperiment), an experimental set-up for fundamental studies on Radio-Frequency vacuum arcs, with particular focus on the effect of an external plasma in the triggering mechanism. The experiment consists of a quarter-wavelength resonator, able to produce up to 43 kV RMS at 46 MHz. The device will be used for basic understanding of the arc mechanism in RF structures subjected to strong ion fluxes.

In the present study, cross-sections were evaluated for the production of the active indium isotopes: 111In (t1/2=2.83 days) and 114In (t1/2=71.9 S) via a bombardment of an enriched Cadmium target with proton beams upto70MeV. Utilizing high cyclotron yield and the optimum cyclotron energy range was chosen for the production of Indium isotopes. The best reactions for producing 111In is 112Cd (p,2n)111In, and for 114In is 116Cd (p,3n)114In. The programs which evaluating cross-sections and the yield were built using Matlab in the present work. The cross-sections of (p,xn) reactions for the production of indium isotopes were assessed depending upon the empirical data taken from the EXFOR library, which is belonging to the International Atomic Energy Agency (IAEA).

Electromagnetic ion cyclotron (EMIC) waves with temperature anisotropy were studied in Saturn’s non-uniform magnetic layer. After the kinetic method, after injecting a cold plasma beam into the Saturn system, the growth rate of the EMIC wave was theoretically studied. An expression of the dispersion relation is drawn by using the method of the characteristic solution. Therefore, in this paper, a ring distribution is used instead of the usual Maxwellian distribution. The focus of this study is on the oblique propagation of EMIC waves, whose temperature anisotropy, ion energy density, and propagation angle vary with the direction of the magnetic field. The study found that these parameters support the growth rate of EMIC waves in the Saturn magnetosphere. Numerical analysis also shows that as the number density of cold plasma and the number of thermal plasmas increase, the growth rate of EMIC waves also increases. These results apply to the application of space plasma environments and magnetospheric systems for detailed comparison of planetary studies.

Lower hybrid (LH) wave has been widely used for non-inductive current drive in modern tokamak experiments with high power injection. LH parametric instability (PI) has been observed in many LH experiments and considered as the most likely candidate which causes the decrease of LH current drive efficiency. Traditional LH PI theories are mostly based on the electrostatic model given the fact that the slow wave branch in LH frequency range is a quasi-electrostatic wave. However, electrostatic description is not accurate for the plasma parameters of scraped-off layer(SOL) region where LH PIs are observed in current fusion experiments. Thus, in this work, we include the electromagnetic correction for slow wave and build up the corresponding nonlinear dispersion relation of PI. The electromagnetic effects on two major decay channels, i.e., ion sound quasi-mode (ISQM) and ion cyclotron quasi-mode (ICQM) are discussed.

The encounter between Voyager and Saturn’s environment reveals the presence of electromagnetic ion cyclotron waves (EMIC) in the magnetosphere of Saturn. Cassini provides evidence of dynamic particle injection in Saturn’s internal magnetosphere. Previous theoretical studies have suggested that EMIC waves may explain the loss of relativistic electron populations. However, recent observations indicate that although the EMIC wave is responsible for the significant loss of super-relativistic electrons, the relativistic electron population is almost unaffected. In this paper, we study the effects of EMIC waves and relativistic particles on these waves in the plasma, which propagate obliquely relative to Saturn’s magnetic field. The particles are assumed to be trapped and follow ring distribution function. Using the kinetic approach, the expressions of dispersion relation and growth rate are derived. Various parameters affecting the growth of EMIC waves has been studied. The effect of drift velocity has also been studied in this case.

Experiments in DIII-D have measured the width of the power deposition and current drive profiles for electron cyclotron (EC) waves by modulating the gyrotrons and fitting the periodic response of the electron temperature profile or motional Stark effect signals to a linearized diffusion equation. The measured EC power deposition widths are scattered around the predicted values, including both narrower and wider cases. The average width for single gyrotron modulation is ≈88% of the theoretical value from ray tracing, while the average width for multiple gyrotron modulation is ≈127% of theory; aiming misalignment between the different EC launchers may explain why multi-gyrotron measurements are wider than for single gyrotrons. The measured EC current drive widths have nearly the same amount of profile broadening (≈131% of theory, on average) as does multi-gyrotron power deposition. Finally, while the measured locations of EC current drive are well centered on the expected values, the measured heating locations are skewed to larger radius. This difference may be due to rapid heat pulse propagation causing an inherent outward bias to the deduced power deposition profile, whereas magnetic flux diffusion has less effect on current drive measurements.

A multipurpose Cyclotron was proposed as a Malaysian national accelerator facility for radio-isotope production, alpha therapy, neutron science, material science and mutation. The requirements of the facility with the basic parameters are discussed here.

Ion cyclotron emission (ICE) detection system has been successfully designed and used on the Experimental Advanced Superconducting Tokamak (EAST). Experiments were performed in deuterium target plasmas, with the neutral heating beam consisting of 100% deuterium atoms accelerated up to 55-70 keV. The spectrum analyzer was used to detect the spectrogram of ICE signals with the operation frequencies of 10 MHz and 100 MHz. The spectrogram of ICE signals contains very strong and narrow emission lines, which correspond to successive cyclotron harmonics of deuterons at the outer midplane (major radius R∼2.20 m). In addition, experimental observations of correlations with edge-localized modes also support that the excitation region of the ICE is located near the plasma edge.

Ion Cyclotron Range of Frequencies (ICRF) strap antennas are routinely adopted in most of the existing nuclear fusion experiments, even though their main goal, i.e. to couple high power to the plasma (MW), is often limited by rather severe drawbacks due to high fields on the antenna itself and on unmatched part of the feeding lines directly connected to the antenna. In this work, we propose, describe, prototype and measure an ICRF strap antenna based on the high impedance surfaces concept that is matched at a specific tunable frequency. The adopted high-impedance structure, positioned between the strap and the backwall, is a metallic patch displaced on top of a dielectric block and grounded by means of a vertical post, in a mushroom-like shape. This structure presents a high impedance, within a given very narrow frequency band, such that the image currents are in-phase with the currents of the strap itself, thus determining a significant efficiency increase. After a general description on the properties of high impedance surfaces applied to ICRF antennas, we describe the optimization steps, carried on by means of numerical codes, to define an antenna configuration suitable for a nuclear fusion experiment. The antenna has been then manufactured and measured; strengths and weaknesses of the proposed solution are outlined.

Building on Alcator C-Mod experience and using the emerging technology of high-temperature superconducting magnet, SPARC is designed to be a compact (R0 = 1.65 m), high field (B0 = 12 T) pulsed tokamak to carry out D-T burning experiments and to demonstrate net-gain from fusion energy. Ion cyclotron range of frequency (ICRF) heating is proposed as the sole auxiliary heating method based on its success on Alcator C-Mod as well as TFTR and JET during their D-T operations. Among all the heating methods, ICRF heating is the only practical and proven method that can heat high density and high field plasmas in SPARC for both the pre-tritium operation and D-T operation. The pre-conceptual design (V0) of the ICRF system has 12 four-strap antennas. Each antenna will be powered by two 2-MW transmitters. Total RF source power (f ~ 120 MHz) will be ≥ 50 MW. Because of high edge density, the antenna loading is expected to be similar to that on Alcator C-Mod, resulting in relatively low voltage on the antennas and in the transmission lines. The single-pass-absorption (SPA) of the fast waves is much higher than that on Alcator C-Mod for the same plasma composition. For D-T burning plasmas with a small amount of 3He, combining the 2nd harmonic T heating and minority 3He heating and in some cases, fundamental D heating, will have good absorption under most plasma conditions. There exists a large parameter space in 3He concentration, k|| and RF frequency for reliable heating. To minimize the impact of impurities, we will use the latest techniques in antenna design and operation scheme, including aligning antenna straps to the magnetic field and tailoring antenna spectra. Ferrite tuners will be implemented in the transmission lines for real-time antenna matching during transient events like L-H transitions and ELMs.

The Cassini spacecraft observed electromagnetic ion cyclotron waves in Saturn’s inner magnetosphere. EMIC waves have frequencies close to the frequency of water-group ions, they are left-handed, and, in most areas, they propagate to the ambient magnetic field at small angles. Their origins are explained by the ion cyclotron instability generated by the water group ions extracted from Saturn’s neutral clouds. These waves propagate no more than 5° at an oblique angle to the magnetic field. These fluctuations can be identified as the n = 2 mode resulting from the ring distribution of the picked-up ions. In this work, we studied the characteristics of these waves. We also use kinetic method analysis to assess growth rates. The results obtained for the demonstration values of the parameters suitable for the Saturn magnetosphere have been calculated and discussed. It is assumed that temperature anisotropy is an additional free energy source for ion cyclotron instability. Regardless of the magnitude, the AC frequency can significantly affect the growth rate. The drift velocity also seems to affect the growth rate. This result is important to explain the VLF emissions observed over a wide frequency range.

International audience; Nonlinear interaction between kinetic instabilities in partially magnetized plasmas in the presence of multiply charged ion streams is investigated using kinetic simulations. It was observed by Hara and Tsikata [Phys. Rev. E 102, 023202 (2020)] that the axial ion–ion two-stream instability due to singly and doubly charged ion streams, coupled with the azimuthal electron cyclotron drift instability (ECDI), enhances cross-field electron transport. In the present study, it is observed that the addition of triply charged ions (as a third ion species) contributes to damping of the excited modes, leading to a reduction in the cross-field electron transport. The net instability-driven electron transport is shown to be a function not only of the azimuthal modes, such as the ECDI, but of the multiple ion species that dictate the development of additional plasma waves. It is found that trapping of the higher ion charge states within the plasma waves results in broadening of the ion velocity distribution functions.

A fully relativistic model of electron cyclotron current drive (ECCD) efficiency based on the adjoint function techniques is considered. Numerical calculations of the current drive efficiency in a tokamak by using the variational approach are performed. A fully relativistic extension of the variational principle with the modified test function for the Spitzer function with momentum conservation in the electron–electron collision is described in general tokamak geometry. The model developed has generalized that of Marushchenko et al., which is extended for arbitrary temperatures and covers exactly the asymptotic for u≫1 when Zeff≫1, and is suited to ray-tracing and beam-tracing calculations. As a demonstration, the new model is applied in one of widely used ray-tracing codes, TORAY-GA, and yields distinct improvement on the fidelity for the calculation of ECCD in the hybrid operating scenario for the China fusion engineering test reactor.

A typical problem of the development of high-harmonic short-wavelength gyrotrons, namely, the competition between the operating wave and a parasitic fundamental-harmonic wave, is studied. A specific case of the excitation of a far-from-cutoff parasitic wave in the backward-wave oscillator regime is considered.

The paper describes an implementation of a long mirror-based variant of cyclotron autoresonance which permits a local temporary change in the mirror`s induction and provides a mode for filling the trap with primary plasma, and for the generation of plasma bunches with an energetic electron component and their accumulation within a single cavity. The approach does not require injection of external particles into the acceleration zone as particles can be generated directly within the mirror using specialized conditions of electron cyclotron resonance (ECR) as part of the operational mode. A detailed study of the spectral-angular distribution of Bremsstrahlung in various operational modes has been undertaken. The results of this study permit the optimal value of the time sequence between the leading edge of the pulsed magnetic field and the microwave pulse to be determined, which ensures the optimal mode of electron trapping in the cyclotron autoresonance mode. Bremsstrahlung radiation recorded in the transverse direction has a significantly higher intensity of photons and energy compared to the longitudinal direction during the acceleration and subsequent confinement mode of plasma bunches. The observed changes in the intensity and spectral distribution of the Bremsstrahlung, which depend on the values of the operating parameters for acceleration, afford the possibility to define the dependence of the number of initial plasma particles trapped by cyclotron autoresonance for the different operating modes. The results will improve our understanding of the processes taking place at various stages of the operational modes. In general, such studies are important for gaining an improved understanding of the mechanisms of generation and confinement of hot electron plasma bunches with an energetic electron component for autoresonant interaction in a long mirror.

In saturated Ohmic confinement regime of the experimental advanced superconducting tokamak, significant changes in the relative electron temperature fluctuations T e / T ¯ e, measured by a correlation electron cyclotron emission system, have been observed. It was found that T e / T ¯ e is strongly dependent on the normalized electron temperature and density gradient, R / L T e = R ∇ T e / T e and R / L n e = R ∇ n e / n e. T e / T ¯ e stay at a high level when R / L T e is within the range of 17 − 25 and R / L n e is within the range of 4 − 6. It has been also observed that the energy confinement degradation is correlated with the increase in electron temperature fluctuations. The linear stability analysis results show that the electron temperature fluctuations are mainly attributed to the ion temperature gradient modes.

The radial density profile of pre-thermal quench (pre-TQ) early-time non-thermal (hot) electrons is estimated by combining electron cyclotron emission and soft x-ray data during the rapid shutdown of low-density ( n e ≲ 10 19 m − 3 ) DIII-D target plasmas with cryogenic argon pellet injection. This technique is mostly limited in these experiments to the pre-TQ phase and quickly loses validity during the TQ. Two different cases are studied: a high (10 keV) temperature target and a low (4 keV) temperature target. The results indicate that early-time, low-energy (∼10 keV) hot electrons form ahead of the argon pellet as it enters the plasma, affecting the pellet ablation rate; it is hypothesized that this may be caused by rapid cross field transport of argon ions ahead of the pellet or by rapid cross field transport of hot electrons. Fokker–Planck modeling of the two shots suggests that the hot electron current is quite significant during the pre-TQ phase (up to 50% of the total current). Comparison between modeled pre-TQ hot electron current and post-TQ hot electron current inferred from avalanche theory suggests that hot electron current increases during the high-temperature target TQ but decreases during the low-temperature target TQ. The uncertainties in this estimate are large; however, if true, this suggests that TQ radial loss of hot electron current could be larger than previously estimated in DIII-D.

Electromagnetic ion cyclotron (EMIC) waves have been studied in this manuscript which are triggered by hot proton thermal anisotropy having energy ranging from 7 to 26 keV with a minimum resonant energy of 6.9 keV. However, an opposite effect can be observed for the hot protons for energy less than the minimum resonant energy. When the intensity of EMIC waves is large, the cold protons (ions) having low-energies can be energized by the EMIC waves. The possible reasons for this energization are the phase bunching of low energy ions with EMIC waves and the generation of electric fields at the relaxation time of substorm. As a consequence, these undetectable protons now become detectable, and the number density and temperature anisotropy of the protons also increase within the energy range from 1 to 100 eV. Accordingly, the helium ions are also energized by the EMIC waves.

This study shows the feasibility of a beam emission spectroscopy (BES) diagnostic in the Helically Symmetric eXperiment (HSX) stellarator for obtaining the spatiotemporal structure of density fluctuation. A beam emission simulation was applied to HSX plasmas to design and optimize viewing chords and to estimate the beam emission spectrum. A Doppler-shifted beam emission spectrum was measured from a 30 kV, 4 A diagnostic neutral beam injected into HSX plasmas. The beam emission was measured with a high-time-resolution avalanche photodiode (APD) assembly to determine the feasibility of BES in HSX. For HSX plasmas heated by 28 GHz electron cyclotron heating, a mode around f = 15 kHz was observed in the BES signal. The coherence between the BES signal and the density fluctuation measured by an interferometer system was significant. A plan for improving the BES system to enable the measurement of higher frequency related to turbulent transport is presented. The array of sightlines proposed in this study can be used to measure beam emission with a Doppler shift larger than 3 nm (blue shift), which enables the use of a wide passband interference filter to obtain higher throughput. The adoption of a large objective optics and a chilled APD assembly will improve the signal-to-noise ratio.

We present magnetoresistance studies of the quasi-two-dimensional organic conductor $\kappa$-(BETS)$_2$Mn[N(CN)$_2$]$_3$, where BETS stands for bis\-(ethylene\-dithio)\-tetra\-selena\-fulvalene. Under a moderate pressure of 1.4\,kbar, required for stabilizing the metallic ground state, Shubnikov - de Haas oscillations, associated with a classical and a magnetic-breakdown cyclotron orbits on the cylindrical Fermi surface, have been found at fields above 10\,T. The effective cyclotron masses evaluated from the temperature dependence of the oscillation amplitudes reveal strong renormalization due to many-body interactions. The analysis of the relative strength of the oscillations corresponding to the different orbits and its dependence on magnetic field suggests an enhanced role of electron-electron interactions on flat parts of the Fermi surface., Comment: 6 pages, 4 figures

The Isotope Decay-At-Rest (IsoDAR) experiment is a short baseline neutrino experiment designed to measure neutrino oscillations by placing a high flux anti-neutrino source near a kiloton scale scintillator detector. A high current proton beam will be used to produce the large number of anti-neutrinos needed. Reaching the design goal of 10 mA of 60 MeV protons on target requires advancements in accelerator technology. This will be achieved using a high intensity H2+ ion source followed by a radio-frequency quadrupole and spiral inflector to axially inject ions into a compact cyclotron. This high current cyclotron could also be applied to producing valuable isotopes in quantities that are beyond the reach of existing technology. We will discuss the results of our latest studies of this injection system. This work is being presented on behalf of the IsoDAR collaboration.The Isotope Decay-At-Rest (IsoDAR) experiment is a short baseline neutrino experiment designed to measure neutrino oscillations by placing a high flux anti-neutrino source near a kiloton scale scintillator detector. A high current proton beam will be used to produce the large number of anti-neutrinos needed. Reaching the design goal of 10 mA of 60 MeV protons on target requires advancements in accelerator technology. This will be achieved using a high intensity H2+ ion source followed by a radio-frequency quadrupole and spiral inflector to axially inject ions into a compact cyclotron. This high current cyclotron could also be applied to producing valuable isotopes in quantities that are beyond the reach of existing technology. We will discuss the results of our latest studies of this injection system. This work is being presented on behalf of the IsoDAR collaboration.

This paper reports the detection and measurement of neutron-induced isotopes in the vault wall of the CS-30 cyclotron located at King Faisal Specialist Hospital and Research Centre (KFSHRC). The aim was to avoid the harmful effects of radiation on employees working with the cyclotron and on faculty members and students using it for nuclear physics research and industrial applications. In addition, emitted radioactivity values are essential in future experiments, as background levels to be subtracted from collected data. Detection was performed using a portable gamma ray spectroscopy system consisting of a NaI(Tl) detector (CANBERRA, model: 802-4) coupled with a digitizer (CAEN, model: N6730) at a counting time of 10 minutes for each point on the wall. The points were at the orientation of 0° with respect to the incoming proton beams and all at 1.5 m above the floor. The results indicate that Co-60, Co-56, Mn-56, Fe-53 are the major radionuclides contributing to the gamma radiation emitted from the wall of cyclotron vault. The link between these isotopes and their corresponding elements was established using the branching index technique. It was found that some isotopes detected were the daughters of elements constituting a very small proportion of the concrete structure such as iron (0.50%), while the elements representing the bulk of the concrete showed no radioactivity. No other significant radioactive sources were detected in the wall. The maximum exposure measured on the wall surface was much less than the permissible occupational exposure for radiation workers.

Accelerator-based Ion Beam Analysis (IBA) has been actively used at the Cyclotron Institute (CI) at Texas A&M University (TAMU) to support the undergraduate research program. PIXE (Particle Induced X-ray Emission) and PIGE (Particle Induced Gamma-ray Emission) are examples of traditional ion beam techniques for elemental analysis. In the past year, our laboratory has assembled PIXE and PIGE experiments with the intention of collaborating with other departments and universities in the study of contaminants’ pathways to the environment and characterization of materials and, in addition, contribute didactically to undergraduates involved in the project. The implementation of routine PIXE and PIGE analysis at the CI allows students to perform elemental composition studies nondestructively, for a large number of samples in a variety of matrices (environmental or biological) with minimal time and sample preparation. The experiments were performed at the TAMU CI, using the K150 cyclotron. Each matrix was bombarded with a proton beam that ranged from 3.6 - 6.3 MeV, with an intensity between 5 - 9 nA and a beam spot size of 5 - 10 mm. The resulting x- and gamma-rays were measured with SiPIN, SOO and CdTe high-performance x- and gamma-ray detectors, located at 45° and 135° with respect to the beam direction. We will discuss our recent projects in detail and the impact they have on the research program and on undergraduate education.Accelerator-based Ion Beam Analysis (IBA) has been actively used at the Cyclotron Institute (CI) at Texas A&M University (TAMU) to support the undergraduate research program. PIXE (Particle Induced X-ray Emission) and PIGE (Particle Induced Gamma-ray Emission) are examples of traditional ion beam techniques for elemental analysis. In the past year, our laboratory has assembled PIXE and PIGE experiments with the intention of collaborating with other departments and universities in the study of contaminants’ pathways to the environment and characterization of materials and, in addition, contribute didactically to undergraduates involved in the project. The implementation of routine PIXE and PIGE analysis at the CI allows students to perform elemental composition studies nondestructively, for a large number of samples in a variety of matrices (environmental or biological) with minimal time and sample preparation. The experiments were performed at the TAMU CI, using the K150 cyclotron. Each matrix was bombard...

In low-power short-wavelength gyrotrons with weak intensity of the electron–wave interaction, determining of the optimal parameters of the system is a result of a trade-off between the enhancement of the electron efficiency and the increase in the Ohmic loss share with an increasing cavity length. In this paper, we investigate the question of whether it is more advantageous to use operating regimes with a higher current at a fixed electron beam power, or whether it is better to increase the accelerating voltage. The answer to the question is determined strictly by the number of the operating cyclotron harmonic of the gyrotron.

Controlling and mitigating plasma disruptions are a matter of serious concern for tokamak operation since they can cause serious damage to the machine. Dedicated experiments on disruption mitigation have been carried out in ADITYA (R = 75 cm, a = 25 cm), an Ohmically heated circular limiter tokamak. A rapid growth of magneto hydrodynamic (MHD) modes is found to be the major cause of disruptions in ADITYA tokamak. Stimulated disruptions induced by hydrogen gas puffing are successfully mitigated through stabilization of these MHD modes by applying a biased-electrode placed inside the last-closed flux surface prior to the gas injection. However, as biased electrodes cannot be placed inside the plasma in bigger tokamaks, the application of ion-cyclotron waves (ICWs) prior to disruption has been successfully attempted to mitigate disruptions through stabilization of MHD modes in ADITYA tokamak. The amplitude of MHD modes (m/n = 3/1, 2/1) is significantly reduced upon the application of ICW prior to disruption, and the stimulated disruptions are successfully mitigated by preventing the growth and overlapping of these MHD modes. These experimental results demonstrate that MHD driven disruptions may be mitigated due to stabilization of m = 2 modes by ponderomotive force of the IC waves.

Interest in gyrotron operation at cyclotron harmonics is motivated by the users' desire to reduce the magnetic fields required for operation at a given frequency. However, operation at harmonics is more complicated than at the fundamental resonance because in harmonic gyrotrons there are many parasitic modes at the fundamental, which can be prone to excitation. The present study is devoted to the analysis of automodulation instability in harmonic gyrotrons. Such instability may occur, for example, when in the vicinity of the desired second harmonic mode there is a pair of parasitic modes at the fundamental, for the frequencies and azimuthal indices of which some specific conditions are met. In this paper, the equations describing this instability are derived in the cold-cavity approximation. The study is then focused on a second harmonic gyrotron with the parameters optimal for efficient operation. For such a gyrotron, the region of instability is determined in the plane of frequency mismatches between the operating and parasitic modes. This treatment performed within the framework of the general theory is complemented by consideration of some gyrotrons operating in specific modes, which are surrounded by specific sideband modes at the fundamental.

Experimental and modeling investigations of high βp scenarios on DIII-D and EAST tokamaks show advantages in high energy confinement, avoidance of n = 1 MHD, and core-edge integration with reduced heat flux, making this scenario an attractive option for China Fusion Engineering Test Reactor steady-state operation. Experiments show that plasmas with high confinement and high density can be achieved with neutral beam injection on DIII-D (βp ∼ 2.2, βN ∼ 3.5, fBS ∼ 50%, fGw ∼ 1.0, and H98y2 ∼ 1.5) and pure RF power on EAST (βP ∼ 2.0, βN ∼ 1.6, fBS ∼ 50%, fGw ∼ 0.8, and H98y2 > 1.3). By tailoring the current density profile, a q-profile with local (off-axis) negative shear is achieved, which yields improved confinement and MHD stability. Transport analysis and simulation suggest that the combination of a high density gradient and high Shafranov shift allows turbulence stabilization and higher confinement. Using on-axis Electron Cyclotron Heating injection, tungsten accumulation is avoided on EAST, and this is reproduced in modeling. Reduced heat flux (by > 40%) and maintenance of high core confinement is achieved with active feedback control of the radiated divertor, an important result for long pulse operation in tokamaks. The improved physics understanding and validated modeling tools are used to design a 1 GW steady-state scenario for CFETR.

In strong electromagnetic fields, unique plasma phenomena and applications emerge, whose description requires recently developed theories and simulations [Y. Shi, Ph.D. thesis, Princeton University (2018)]. In the classical regime, to quantify effects of strong magnetic fields on three-wave interactions, a convenient formula is derived by solving the fluid model to the second order in general geometry. As an application, magnetic resonances are exploited to mediate laser pulse compression, using which higher intensity pulses can be produced in wider frequency ranges, as confirmed by particle-in-cell simulations. In even stronger fields, relativistic-quantum effects become important, and a plasma model based on scalar quantum electrodynamics (QED) is developed, which unveils observable corrections to Faraday rotation and cyclotron absorption in strongly magnetized plasmas. Beyond the perturbative regime, lattice QED is extended as a numerical tool for plasma physics, using which the transition from wakefield acceleration to electron-positron pair production is captured when laser intensity exceeds the Schwinger threshold., APS DPP 2020 Invited Talk TI01.00001

Magnetic flux ropes have been successfully created with plasma guns in the newly commissioned PHAse Space MApping (PHASMA) experiment. The flux ropes exhibit the expected m = 1 kink instability. The observed threshold current for the onset of this kink instability is half of the Kruskal–Shafranov current limit, consistent with predictions for the non-line tied boundary condition of PHASMA. The helicity, paramagnetism, and growth rate of the observed magnetic fluctuations are also consistent with kink instability predictions. The observed fluctuation frequency appears to be a superposition of a real frequency due to a Doppler shift of the kink mode arising from plasma flow ( ∼ 2 kHz) and a contribution from a wave mode ( ∼ 5 kHz). The dispersion of the wave mode is consistent with an Alfven wave. Distinct from most previous laboratory studies of flux ropes, the working gas in PHASMA is argon. Thus, the ion cyclotron frequency in PHASMA is quite low and the frequency of the Alfvenic mode plateaus at ∼ 0.5 of the ion gyro frequency with increasing background magnetic field strength.

Utilizing variable-frequency channels, e.g., yttrium iron garnet (YIG) bandpass filters, in the intermediate frequency (IF) section of an electron cyclotron emission (ECE) radiometer facilitates flexibility in the volume viewed by the ECE channels as well as high resolution electron temperature and temperature fluctuation measurements in tokamaks. Fast modulating electron cyclotron emission (FMECE), a stand-alone IF section with eight channels, is a novel application of YIG filters for real-time electron temperature gradient and gradient scale length measurements. Key to FMECE is a simultaneous input/output data acquisition unit, as well as a modified type of YIG filters, which is capable of fast switching of their center (set) frequencies with a frequency slew rate of 600 µs/GHz. A new FMECE has been implemented and tested on the DIII-D tokamak, demonstrating its capability in real-time gradient measurements. The data presented here shows that FMECE can identify flattening in the electron temperature profile; the latter can be used as a sensor for real time monitoring and control of plasma instabilities. Implementation and application are planned for the EAST tokamak.

The ion cyclotron emission diagnostic on the DIII-D tokamak comprises seven single-turn loops that measure high-frequency (1-100 MHz) magnetic field fluctuations that are often excited by energetic particles in the plasma. The raw voltage signals induced in the loops in response to these fluctuations travel through a series of cables, isolation transformer DC blocks, low-pass filters, and finally a digitizer before being analyzed in frequency space. The diagnostic has been recently upgraded, most notably to include four additional graphite tile loops and a new eight-channel digitizer. The previous three loops are all on the low-field side of the tokamak. The measurement capabilities of the system have been expanded by the addition of a new horizontally oriented loop on the low-field side, an additional toroidal loop on the low-field side, and two toroidal loops on the high-field side. These loops will be used to provide approximate mode polarization, improved toroidal mode number calculations, and information on modes in inward-shifted plasmas, respectively.

In collision-poor space plasmas protons with an excess of kinetic energy or temperature in direction perpendicular to background magnetic field can excite the electromagnetic ion cyclotron (EMIC) instability. This instability is expected to be highly sensitive to suprathermal protons, which enhance the high-energy tails of the observed velocity distributions and are well reproduced by the (bi-)Kappa distribution functions. In this paper we present the results of a refined quasilinear (QL) approach, able to describe the effects of suprathermal protons on the extended temporal evolution of EMIC instability. It is thus shown that suprathermals have a systematic stimulating effect on the EMIC instability, enhancing not only the growth rates and the range of unstable wave-numbers, but also the magnetic fluctuating energy density reached at the saturation. In effect, the relaxation of anisotropic temperature becomes also more efficient, i.e., faster in time and closer to isotropy., Comment: 10 pages, 7 figures, Submitted to Physics of Plasmas

The plasma current is ramped up primarily by a 28 GHz electron cyclotron wave (ECW) in the Q-shu University experiment Steady-State Spherical Tokamak (QUEST), with multiple harmonic resonance layers from the second to the fourth stay in the plasma core. A steering antenna comprising two quasi-optical mirrors enhances the power density of ECWs. The ECW beam is injected obliquely from the low-field side where the parallel refractive index is N ∥ = 0.75 at the second-harmonic resonance layer. Analysis of the resonance condition has found that energetic electrons moving forward along the magnetic field resonate more effectively than those moving backward. Such symmetry breaking is consistent with the results of the current ramp-up experiment. The peak plasma current reaches I p > 70 kA, constantly injecting a beam of radio frequency power of 100 kW. Ray-tracing by the TASK/WR code demonstrates that the power of the 28 GHz extraordinary mode is absorbed by energetic electrons via single-pass cyclotron absorption.

We present the design for a rapid proton energy modulator with radiofrequency accelerator cavities, which can deliver the proton radiation dose to varied depth in human tissues much faster than traditional mechanical beam energy degraders. The proton energy modulator is designed as a multi-cell 1-m long accelerator working at 2.856 GHz. Each individual accelerator cavity is powered by a 400 kW compact klystron to provide an accelerating/decelerating gradient of 30 MV/m. The high gradient is enabled by the individual power coupling regime, which provides a high shunt impedance. Beam dynamics simulations were performed, showing that the energy modulator can provide ±30 MeV of beam energy change for a 150 MeV, 7 mm long (full length) proton bunch, and the total energy spread of 3 MeV is satisfactory to clinical needs. A prototype experiment of a single cell has been built and tested, and the low-power microwave measurement results agree very well with simulations. The energy modulator is optimized for the 150 MeV cyclotron proton beam, while this approach can work with different beam energies.

It is shown that in the general case the conditions of cyclotron resonances should be formulated with regard to the influence of intense electromagnetic fields, if present, on the particle motion. Moreover, the greater is the wave field strength, the more significantly such effects are pronounced. These effects lead to the appearance of qualitatively new features in the particle dynamics. Such features include regularization of the particle dynamics, particularly a stepwise structure appears in the time dependencies of momenta and energy. The second feature concerns a new generation mechanism of regimes with dynamical chaos. This mechanism differs from the known mechanisms that arise as a result of the intersection of homoclinic structures. The new mechanism appears when particle trajectories pass the point associated with the singular solution of the equations under consideration (at the points of such solutions, the uniqueness theorem is violated).