Proton Cyclotron Research Articles

Design and field measurement of a dipole magnet for a newly developed superconducting proton cyclotron beamline

The design, field quality optimization, multipole field analysis, and field measurement of a dipole for a newly developed superconducting proton cyclotron (SC200) beamline are presented in this paper. The maximum magnetic field of the dipole is 1.35 T; the bending radius is 1.6 m with a proton beam energy in the range of 70–200 MeV. The magnetic field was calculated with 2D and 3D simulations, and measured with a Hall mapping system. The pole shim and end chamfer were optimized to improve the field quality. Based on the simulated results, the multipole field components in the good-field region were studied to evaluate the field quality. The results showed that the field quality is better than ± 5 × 10−4 at 1.35 T with shimming and chamfering. For the transverse field homogeneity, the third-order (B3) and fifth-order (B5) components should be controlled with symmetrical shims. The second-order (B2) component was the main disturbance for the integral field homogeneity; it could be improved with an end chamfer. The magnet manufacturing and field measurement were performed in this project. The measurement results demonstrated that the magnetic design and field quality optimization of the 45° dipole magnet can achieve the desired high field quality and satisfy the physical requirements.

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%.

Nonlinear wave interactions generate high-harmonic cyclotron emission from fusion-born protons during a KSTAR ELM crash

The radio frequency detection system on the KSTAR tokamak has exceptionally high spectral and temporal resolution. This enables measurement of previously undetected fast plasma phenomena in the ion cyclotron range of frequencies. Here we report and analyse a novel spectrally structured ion cyclotron emission (ICE) feature in the range 500 MHz to 900 MHz, which exhibits chirping on sub-microsecond timescales. Its spectral peaks correspond to harmonics l of the proton cyclotron frequency fcp at the outer midplane edge, where l = 20–36. This frequency range exceeds estimates of the local lower hybrid frequency fLH in the KSTAR deuterium plasma. The new feature is time-shifted with respect to a brighter lower-frequency chirping ICE feature in the range 200 MHz (8fcp) to 500 MHz (20fcp), which is probably driven (Chapman et al 2017 Nucl. Fusion 57 124004) by 3 MeV fusion-born protons undergoing collective relaxation by the magnetoacoustic cyclotron instability (MCI). Here we show that the new, fainter, higher-frequency chirping ICE feature is driven by nonlinear wave coupling between different neighbouring spectral peaks in the lower-frequency ICE feature. This follows from bispectral analysis of the measured KSTAR fields, and of the field amplitudes output from particle-in-cell (PIC) simulations of the KSTAR edge plasma containing fusion-born protons. This reinforces the identification of the MCI as the plasma physics process underlying proton harmonic ICE from KSTAR, while providing a novel instance of nonlinear wave coupling on very fast timescales.

A new X-ray look into four old pulsars

We report on the X-ray properties of four rotation-powered pulsars with characteristic ages in the range 0.3–5 Myr, derived from the analysis of XMM–Newton archival observations. We found convincing evidence of thermal emission only in the phase-averaged spectrum of PSR B0114+58, which is well fitted by a blackbody with temperature kT = 0.17 ± 0.02 keV and emitting radius R = 405+110−90 m, consistent with the size of its polar cap. The three other considered pulsars, PSR B0628−28, PSR B0919+06, and PSR B1133+16, have phase-averaged spectra that can be described well by single power laws with photon index Γ ~ 3. The 3σ upper limits on the bolometric luminosity of a possible thermal component with temperatures in the range ~0.05−2 keV are Lbol ≲ 3.2 × 1028 erg s−1 and Lbol ≲ 2.4 × 1029 erg s−1, for PSR B0628−28 and PSR B0919+06, respectively. On the other hand, we found possible evidence that the pulsed emission of PSR B0628−28 is thermal. Two absorption lines at ~0.22 keV and ~0.44 keV are detected in the spectrum of PSR B1133+16. They are best interpreted as proton cyclotron features, implying the presence of multipolar components with a field of a few 1013 G at the neutron star polar caps. We discuss our results in the context of high-energy emission models of old rotation-powered pulsars.

Magnetic and Thermal Design of HTS Quadrupole Magnet for Newly Developed Superconducting Proton Cyclotron Beam Line

A magnetic and thermal design of high-temperature superconducting (HTS) quadrupole magnet for newly developed superconducting proton cyclotron was presented in this research. With superconducting technology, the design can reduce the magnet size and remove the heat loads more efficiently. Calculations are conducted with finite element method (FEM) to study the quadrupole magnet’s magnetic and thermal properties. For the magnet cold-mass and cryostat system, the heat load is mainly generated by conduction and radiation. Multilayer thermal insulation and G10 supports are used to restrict them. The magnetic field distribution in the HTS coils is calculated to consider the critical current degradation of the YBCO tapes. The effects on the field gradient quality in relation to the pole tip profile and end chamfer are analyzed. The sixth multipole component in the integral field can be improved with end chamfer. Finally, a 20 T/m HTS quadrupole magnet with integral field uniformity less than 0.05% out to 75% of the inscribed radius is proposed.

Electron Heating in Low Mach Number Perpendicular Shocks. II. Dependence on the Pre-shock Conditions

Abstract Recent X-ray observations of merger shocks in galaxy clusters have shown that the post-shock plasma is two-temperature, with the protons being hotter than the electrons. In this work, the second of a series, we investigate the efficiency of irreversible electron heating in perpendicular low Mach number shocks, by means of two-dimensional particle-in-cell simulations. We consider values of plasma beta (the ratio of thermal and magnetic pressures) in the range 4 ≲ β p0 ≲ 32, and sonic Mach number (the ratio of shock speed to pre-shock sound speed) in the range 2 ≲ M s ≲ 5, as appropriate for galaxy cluster shocks. As shown in Paper I, magnetic field amplification—induced by shock compression of the pre-shock field, or by strong proton cyclotron and mirror modes accompanying the relaxation of proton temperature anisotropy—can drive the electron temperature anisotropy beyond the threshold of the electron whistler instability. The growth of whistler waves breaks the electron adiabatic invariance, and allows for efficient entropy production. We find that the post-shock electron temperature T e2 exceeds the adiabatic expectation by an amount (here, T e0 is the pre-shock temperature), which depends only weakly on the plasma beta over the range 4 ≲ β p0 ≲ 32 that we have explored, as well as on the proton-to-electron mass ratio (the coefficient of ≃0.044 is measured for our fiducial , and we estimate that it will decrease to ≃0.03 for the realistic mass ratio). Our results have important implications for current and future observations of galaxy cluster shocks in the radio band (synchrotron emission and Sunyaev–Zel’dovich effect) and at X-ray frequencies.

LINUS, the Integrated LNL Neutron Source facility

LINUS is a project at the INFN Legnaro National Laboratories (LNL, Italy) to create a suite of different neutron sources (LSNS, NEPIR, SLOWNE) driven by existing accelerators. LSNS, driven by a 40 mA, 5 MeV proton RFQ, will use Li and Be targets to deliver cold, thermal, epithermal and fast neutrons. The SPES high current (0.75 mA), 70 MeV proton cyclotron will drive the NEPIR and SLOWNE facilities. NEPIR will alternatively deliver quasi mono-energetic neutrons with energy peak down to 20 MeV, and a neutron beam with a continuous energy distribution similar to that of neutrons present in the Earth atmosphere in the accessible energy range. SLOWNE is an intense neutron source for applications outside the LSNS range.

A Potential Cyclotron Resonant Scattering Feature in the Ultraluminous X-Ray Source Pulsar NGC 300 ULX1 Seen by NuSTAR and XMM-Newton

Abstract Based on phase-resolved broadband spectroscopy using XMM-Newton and NuSTAR, we report on a potential cyclotron resonant scattering feature (CRSF) at E ∼ 13 keV in the pulsed spectrum of the recently discovered ultraluminous X-ray source (ULX) pulsar NGC 300 ULX1. If this interpretation is correct, the implied magnetic field of the central neutron star is B ∼ 1012 G (assuming scattering by electrons), similar to that estimated from the observed spin-up of the star, and also similar to known Galactic X-ray pulsars. We discuss the implications of this result for the connection between NGC 300 ULX1 and the other known ULX pulsars, particularly in light of the recent discovery of a likely proton cyclotron line in another ULX, M51 ULX-8.

The Role of Proton Cyclotron Resonance as a Dissipation Mechanism in Solar Wind Turbulence: A Statistical Study at Ion-kinetic Scales

Abstract We use magnetic field and ion moment data from the MFI and SWE instruments on board the Wind spacecraft to study the nature of solar wind turbulence at ion-kinetic scales. We analyze the spectral properties of magnetic field fluctuations between 0.1 and 5.4 Hz during 2012 using an automated routine, computing high-resolution 92 s power and magnetic helicity spectra. To ensure the spectral features are physical, we make the first in-flight measurement of the MFI “noise-floor” using tail-lobe crossings of the Earth’s magnetosphere during early 2004. We utilize Taylor’s hypothesis to Doppler-shift into the spacecraft frequency frame, finding that the spectral break observed at these frequencies is best associated with the proton cyclotron resonance scale, 1/k c , rather than the proton inertial length, d i , or proton gyroscale, ρ i . This agreement is strongest when we consider periods where , and is consistent with a spectral break at d i for and at ρ i for . We also find that the coherent magnetic helicity signature observed at these frequencies is bounded at low frequencies by 1/k c , and its absolute value reaches a maximum at ρ i . These results hold in both slow and fast wind streams, but with a better correlation in the more Alfvénic fast wind where the helicity signature is strongest. We conclude that these findings are consistent with proton cyclotron resonance as an important mechanism for dissipation of turbulent energy in the solar wind, occurring at least half the time in our selected interval. However, we do not rule out additional mechanisms.

Statistical Study of Low‐Frequency Electromagnetic Cyclotron Waves in the Solar Wind at 1 AU

AbstractElectromagnetic cyclotron waves (ECWs) near the proton cyclotron frequency are common wave activities in the solar wind and have attracted much attention in recent years. This paper investigates 82,809 ECWs based on magnetic field data from the Solar Terrestrial Relations Observatory‐A mission between 2007 and 2013. Results show that ECWs may last for just a few seconds or incessantly for several tens of minutes. The time fraction of ECW storms among all solar wind is about 0.9%; the storms are obtained with the duration threshold of 10 min, amplitude criterion of 0.032 nT, and time separation limit of 3 min for combination of intermittent ECWs. Most of ECWs have their amplitudes less than 1 nT, while some ECWs have large amplitudes comparable to the ambient magnetic field. The distributions of the durations and amplitudes of these ECWs are characterized by power law spectra, respectively, with spectrum indexes around 4. Statistically, there seems to be a tendency that ECWs with a longer duration will have a larger amplitude. Observed ECW properties are time dependent, and the median frequency of left‐hand ECWs can be lower than that of right‐hand ECWs in some months in the spacecraft frame. The percentage of left‐hand ECWs varies in a large range with respect to months; it is much low (26%) in a month, though it frequently exceeds 50% in other months. Characteristics of ECWs with concurrent polarizations are also researched. The present study should be of importance for a more complete picture of ECWs in the solar wind.

Fast Magnetosonic Waves Observed by Van Allen Probes: Testing Local Wave Excitation Mechanism

AbstractLinear Vlasov theory and particle‐in‐cell (PIC) simulations for electromagnetic fluctuations in a homogeneous, magnetized, and collisionless plasma are used to investigate a fast magnetosonic wave event observed by the Van Allen Probes. The fluctuating magnetic field observed exhibits a series of spectral peaks at harmonics of the proton cyclotron frequency Ωp and has a dominant compressional component, which can be classified as fast magnetosonic waves. Furthermore, the simultaneously observed proton phase space density exhibits positive slopes in the perpendicular velocity space, ∂fp/∂v⊥>0, which can be a source for these waves. Linear theory analyses and PIC simulations use plasma and field parameters measured in situ except that the modeled proton distribution is modified to have larger ∂fp/∂v⊥ under the assumption that the observed distribution corresponds to a marginally stable state when the distribution has already been scattered by the excited waves. The results show that the positive slope is the source of the proton cyclotron harmonic waves at propagation quasi‐perpendicular to the background magnetic field, and as a result of interactions with the excited waves the evolving proton distribution progresses approximately toward the observed distribution.

Survey of the Favorable Conditions for Magnetosonic Wave Excitation

AbstractThe ratio of the proton ring velocity (VR) to the local Alfven speed (VA), in addition to proton ring distributions, plays a key factor in the excitation of magnetosonic waves at frequencies between the proton cyclotron frequency fcp and the lower hybrid resonance frequency fLHR in the Earth's magnetosphere. Here we investigate whether there is a statistically significant relationship between occurrences of proton rings and magnetosonic waves both outside and inside the plasmapause using particle and wave data from Van Allen Probe‐A during the time period of October 2012 to December 2015. We also perform a statistical survey of the ratio of the ring energy (ER, corresponding to VR) to the Alfven energy (EA, corresponding to VA) to determine the favorable conditions under which magnetosonic waves in each of two frequency bands (fcp < f ≤ 0.5 fLHR and 0.5 fLHR < f < fLHR) can be excited. The results show that the magnetosonic waves in both frequency bands occur around the postnoon (12–18 magnetic local time, MLT) sector outside the plasmapause when ER is comparable to or lower than EA, and those in lower‐frequency bands (fcp < f ≤ 0.5 fLHR) occur around the postnoon sector inside the plasmapause when ER/EA > ~9. However, there is one discrepancy between occurrences of proton rings and magnetosonic waves in low‐frequency bands around the prenoon sector (6–12 MLT) outside the plasmapause, which suggests either that the waves may have propagated during active time from the postnoon sector after being excited during quiet time, or they may have locally excited in the prenoon sector during active time.

Experimental study about single event functional interrupt of ferroelectric random access memory induced by 30-90 MeV proton

Ferroelectric random access memory (FRAM) is a promising memory for space application. The performance of FRAM under irradiation environment should be investigated, especially under proton irradiation environment, which dominates the particles in the space environment. The experiments on single event effects are carried out for two types of FRAMs (FM22L16 and FM28 V100) based on the proton cyclotron of China institute of atomic energy. Both dynamic and static mode are tested for each chip under the irradiation of proton in an energy range from 30 MeV to 90 MeV. Single event upsets (SEUs) and single event functional interrupts (SEFIs) are observed only on FM22L16, where the SEFI is recorded as a significantly transient error with or without memory cell upsets. The SEFI can be subdivided into soft SEFI and hard SEFI according to whether those significantly transient errors disappear or not when the irradiation is paused. Single event effect performances of FM22L16 are accurately described, and the SEFI cross section in an energy range from 50 MeV to 90 MeV is obtained experimentally. The cross section of SEFI increases with proton energy increasing and reaches 10<sup>-3</sup>/cm<sup>2</sup> at 90 MeV. To further study the mechanism of SEFI, the pulsed laser beam with a wavelength of 1064 nm is used to pinpoint the sensitive area of SEFI in the FRAM. Pulsed laser experiment is easy to carry out when single pulsed laser radiates on the device from the back side. Results show that a certain part in peripheral circuit is detected as a sensitive area to SEFI. The sensitive area could be a register or buffer which is vulnerable to irradiation. Only SEUs are observed when the pulsed laser radiates others area of peripheral circuit and memory cell. A hypothesis that a micro latch-up in the CMOS-based peripheral circuit leads to the SEFI is proposed to explain the test results, for the CMOS-based peripheral circuit is sensitive to irradiation. The further reason is the energy deposition in silicon substrate by protons with energies ranging from 30 MeV to 90 MeV through nuclear reaction, which triggers the silicon controlled rectifier structure in the FRAM peripheral circuit. According to the hypothesis, a transient current should be generated in the peripheral circuit when the micro latch-up happens. The transient current is observed on the output of device by using a high frequency oscilloscope which demonstrates the reasonability of the hypothesis.

Use of a medical positron emission tomography cyclotron to perform proton-induced X-ray emission analysis

We explored whether medical positron emission tomography (PET) cyclotron proton beams could be used for proton-induced X-ray emission (PIXE) analysis. The beam current of the medical PET cyclotron is high, as required for radioisotope production, and is not commonly used for PIXE analysis. We successfully extracted stable proton beams of low intensity by using the ion source of a medical cyclotron to exploit proton impurities in deuteron gas. We performed 20-MeV PIXE analysis of a biological sample (used tea leaves). Elements lighter than Sr could be detected with high sensitivity ([Formula: see text]14 ppm) using a silicon drift detector. We thus showed that a medical cyclotron widely used for PET diagnosis could be employed for PIXE analysis of biological samples.

Electron Heating in Low-Mach-number Perpendicular Shocks. I. Heating Mechanism

Abstract Recent X-ray observations of merger shocks in galaxy clusters have shown that the postshock plasma has two temperatures, with the protons hotter than the electrons. By means of two-dimensional particle-in-cell simulations, we study the physics of electron irreversible heating in low-Mach-number perpendicular shocks, for a representative case with sonic Mach number of 3 and plasma beta of 16. We find that two basic ingredients are needed for electron entropy production: (1) an electron temperature anisotropy, induced by field amplification coupled to adiabatic invariance; and (2) a mechanism to break the electron adiabatic invariance itself. In shocks, field amplification occurs at two major sites: at the shock ramp, where density compression leads to an increase of the frozen-in field; and farther downstream, where the shock-driven proton temperature anisotropy generates strong proton cyclotron and mirror modes. The electron temperature anisotropy induced by field amplification exceeds the threshold of the electron whistler instability. The growth of whistler waves breaks the electron adiabatic invariance and allows for efficient entropy production. For our reference run, the postshock electron temperature exceeds the adiabatic expectation by , resulting in an electron-to-proton temperature ratio of . We find that the electron heating efficiency displays only a weak dependence on mass ratio (less than drop, as we increase the mass ratio from up to ). We develop an analytical model of electron irreversible heating and show that it is in excellent agreement with our simulation results.

Phase-dependent absorption features in X-ray spectra of X-ray Dim Isolated Neutron Stars

A detailed phase-resolved spectroscopy of archival XMM–Newton observations of X-ray Dim Isolated Neutron Stars (XDINSs) led to the discovery of narrow and strongly phase-dependent absorption features in two of these sources. The first was discovered in the X-ray spectrum of RX J0720.4-3125, followed by a new possible candidate in RX J1308.6+2127. Both spectral lines have similar properties: they are detected for only ∼ 20% of the rotational cycle and appear to be stable over the timespan covered by the observations. We performed Monte Carlo simulations to test the significance of these phase-variable features and in both cases the outcome has confirmed the detection with a confidence level > 4.6σ. Because of the narrow width and the strong dependence on the pulsar rotational phase, the most likely interpretation for these spectral features is in terms of resonant proton cyclotron absorption scattering in a confined high-B structure close to the stellar surface. Within the framework of this interpretation, our results provide evidence for deviations from a pure dipole magnetic field on small scales for highly magnetized neutron stars and support the proposed scenario of XDINSs being aged magnetars, with a strong non-dipolar crustal B-field component.

Compact high current proton cyclotron and associated beam dynamics

A compact proton cyclotron of 1 MeV, 5 mA is being developed at VECC is an R{&}D project to study and settle various problems related with the transport, injection and acceleration of high current beams in a cyclotron. Proton beam from 2.45 GHz microwave ion source (already operating with 8 mA @ 80 keV) will be first bunched using a sinusoidal buncher and then will be injected axially in the central region of the cyclotron where a spiral inflector will place the beam on the proper orbit. In this paper we discuss the design of the magnet of 1 MeV cyclotron, simulation results of beam transmission through the spiral inflector and the results of studies on the behaviour of transverse envelopes of space charge dominated beam along the accelerated orbits. Efforts have been made to obtain the proper matching conditions at the central region by optimizing the input beam parameters of the injected beam. The maximum beam current that can be accelerated through the available aperture of the cyclotron focusing channel has also been estimated.

Study of the Variation of Material layer Compotition and Thickness Related Neutron Flux and Gamma Radiation

Optimation of simulation design of collimator is corresponding to 30 MeV cyclotron generator. The simulation has used the variation of the thickness materials layers that was applied at treatment room’s door. The purpose of the variation and thickness of the material in this simulation to obtain optimum results for the shielding design in the irradiation chamber. The layers that we used are Pb-Fe and Pb-SS312. Simulation on cancer treatment is used with monte carlo simaulation MCNPX. The spesifications that we used for cyclotron is the spesification of the HM-30 Proton Cyclotron from Sumitomo Heavy Industries Ltd. The variation of the thickness materials layers that was applied at treatment room’s door are Pb remains 4cm while Fe and SS312 varies between 2 cm, 4 cm, 6 cm respectively. This simulation of Fe layer on Pb was give good result in measurement simulation at 4 cm thickness.

Sub-microsecond temporal evolution of edge density during edge localized modes in KSTAR tokamak plasmas inferred from ion cyclotron emission

During edge localised mode (ELM) crashes in KSTAR deuterium plasmas, bursts of spectrally structured ion cyclotron emission (ICE) are detected. Usually the ICE spectrum chirps downwards during an ELM crash, on sub-microsecond timescales. For KSTAR ICE where the separation of spectral peak frequencies is close to the proton cyclotron frequency at the outer plasma edge, we show that the driving population of energetic ions is likely to be a subset of the 3 MeV fusion protons, born centrally on deeply passing orbits which drift from the core to the edge plasma. We report first principles modelling of this scenario using a particle-in-cell code, which evolves the full orbit dynamics of large numbers of energetic protons, thermal deuterons, and electrons self-consistently with the electric and magnetic fields. The Fourier transform of the excited fields in the nonlinear saturated regime of the simulations is the theoretical counterpart to the measured ICE spectra. Multiple simulation runs for different, adjacent, values of the plasma density under KSTAR edge conditions enable us to infer the theoretical dependence of ICE spectral structure on the local electron number density. By matching this density dependence to the observed time-dependence of chirping ICE spectra in KSTAR, we obtain sub-microsecond time resolution of the evolving local electron number density during the ELM crash.

Whistler Mode Waves Below Lower Hybrid Resonance Frequency: Generation and Spectral Features

AbstractEquatorial noise in the frequency range below the lower hybrid resonance frequency, whose structure is shaped by high proton cyclotron harmonics, has been observed by the Cluster spacecraft. We develop a model of this wave phenomenon which assumes (as, in general, has been suggested long ago) that the observed spectrum is excited due to loss cone instability of energetic ions in the equatorial region of the magnetosphere. The wavefield is represented as a sum of constant frequency wave packets which cross a number of cyclotron resonances while propagating in a highly oblique mode along quite specific trajectories. The growth (damping) rate of these wave packets varies both in sign and magnitude along the raypath, making the wave net amplification, but not the growth rate, the main characteristic of the wave generation process. The growth rates and the wave amplitudes along the ray paths, determined by the equations of geometrical optics, have been calculated for a 3‐D set of wave packets with various frequencies, initial L shells, and initial wave normal angles at the equator. It is shown that the dynamical spectrum resulting from the proposed model qualitatively matches observations.