Ion Beam Emission Research Articles

Simulation and Measurement of Carbon Ion Beam Emittance in the Channel of Radiobiological Research at the Accelerator Complex U-70

The technique for determining the emittance of carbon ion beams by measuring their transverse dimensions at the end of the air gap of the channel is described. The inverse transformation of phase ellipses is considered, taking into account multiple Coulomb scattering of particles and the presence of dispersion in the carbon ion beam. The values of betatron emittance before the first quadrupole lens are given and compared with data obtained by direct calculation starting from the inner target. Inaccuracies in the calculated and measured emittance values are discussed. Simulations and measurements were performed at beam energies of 200, 300, and 400 MeV/nucleon in front of the target.

A method of real-time monitoring beam output stability of intense pulsed ion beam

Intense pulsed ion beam (IPIB) technology has made remarkable progress in surface modification, mixing, polishing, film deposition, and nano powder synthesis in recent years. However, the surface properties of materials under IPIB irradiation are highly sensitive to beam intensity variations. Deviations from acceptable parameter range can change the surface characteristics and increase prevalence of defects. Consequently, the real-time online monitoring of beam stability during irradiation experiments and promptly identifying of pulses exhibiting significant parameter jitter are of significance in accurately analyzing results and optimizing surface modification. This study presents a fast-response pulse X-ray diagnostic system by employing EJ-200 plastic scintillator, 9266FLB photomultiplier tube, and Tektronic TDS 2024 four-channel oscilloscope. Single particle test demonstrates that the system achieves a time resolution of 6 ns, meeting the requirements for temporal response to detecting pulse X-ray signals with a half-width of ~80 ns. By adjusting the insulation magnetic field strength of the ion diode, the IPIB output level is regulated. The diagnostic system successfully captures X-rays emitted by the external magnetic insulated ion diode operating at different output levels. Simultaneously, the ion beam energy density is measured by using an infrared camera. To mitigate diagnostic errors stemming from target ablation, the maximum energy density is controlled to be below 1.32 J/cm<sup>2</sup>. Analysis results establish a positive correlation between X-ray intensity and ion beam energy density. This relationship arises from the influence of the insulating magnetic field adjustment on the diode's operating voltage, which subsequently affects the bremsstrahlung radiant intensity and ion beam emission intensity. This correlation offers the potential for the real-time monitoring of IPIB beam output stability by utilizing X-ray signals. To further corroborate the synchronized changes in pulse X-ray intensity and ion beam intensity, Faraday cup is employed as an alternative to infrared imaging method for measuring ion current density. Results demonstrate that the amplitude of the X-ray signal changes synchronously with fluctuations of ion current density. It is worth noting that when the output intensity of ion beam deviates significantly (more than 10% of the preset value), the diagnostic system will respond quickly. These findings validate the efficacy of the proposed non-interceptive diagnostic method of real-time monitoring the intense pulsed ion beam output stability.

Effect of the Gap Size between the Cathode and the Wehnelt Cylinder Bore on the Emittance of the Thermionic Electron Gun

This paper includes simulating an electron gun design to investigate the effect of the distance between the cathode and the Wehnelt cylinder bore on the quality of the ion beam emittance and to obtain the best distance of that geometrical factor. A study of a group of designs was conducted to find this distance. The SIMION8.0 program has been used to calculate the trajectories of the electrons with initial kinetic energy of (0.1 eV) and electron current of (1×10-12 A). The investigation also includes comparisons between the equipotential line trajectories for each design as well as the field distribution and the electron trajectories. The best emittance distance was concluded to be (3 mm).

Effect of Solenoidal Magnetic Field on Time Evolution of Ion Beam Emittance in Laser Ion Source

Applying a solenoidal magnetic field to a laser ion source is a method to produce a high current beam. In this study, we measured the effect of the solenoidal magnetic field on the time evolution of the ion beam emittance using the double-slit method for the laser ion source. Ablation plasma was produced by irradiating an Al target with an Nd:YAG laser. From the emittance measurements, the phase difference shown in the time evolution of the emittance ellipses increased as the ion current increased by applying a magnetic field. In addition, the emittance increased with increasing time range for the averaged current in the waveform. However, the emittance using the averaged current in a pulse was almost constant with the magnetic field. These results indicate that the brightness of the beam increased as the ion beam current increased using the solenoidal magnetic field.

Emittance growth caused by phase modulation in bunched electron beam cooling

The demand for electron coolers operating at much higher energies than previously achieved necessitates the use of radio-frequency (RF) fields for electron acceleration resulting in the bunched electron beams. Differences in the time structure of ion and electron bunches and variations in their relative timing significantly affect the cooling process. Experiments on ion beam cooling with a short electron bunch have been carried out in the CSRm storage ring at IMP (Lanzhou). Longitudinal painting by the electron bunch phase modulation is found leading to a significant ion beam loss. We show that the space charge field variations of the bunched electron beam play a major role in the ion beam emittance growth while cooling. In this paper, we study the dependency of the ion beam emittance growth on the electron beam parameters and present results of numerical simulation which support experimental observations.

Copper ion beam emission in solid electrolyte Rb4Cu16I6.5Cl13.5

Copper ion conducting solid electrolyte Rb4Cu16I6.5Cl13.5 was prepared by means of mechano-chemical method. The structure and morphology of the powder was investigated by x-ray diffraction and scanning electron microscopy. The grain size was estimated to be 0.2–0.9 μm and the ionic conductivity at room temperature was approximately 0.206 S/cm. The solid electrolyte Rb4Cu16I6.5Cl13.5 was exploited for copper ion beam generation. The copper ion emission current of several nA was successfully obtained at acceleration voltages of 15 kV and temperature of 197 °C in vacuum of 2.1 × 10−4 Pa. A good linear correlation between the logarithmic ion current (log I) and the square root of the acceleration voltage (U acc) at high voltage range was obtained, suggesting the Schottky emission mechanism in the process of copper ion beam generation.

Angular Distribution of Ion Beam Emission From Dense Plasma Focus Device: An Investigation by the Vlasov–Maxwell Equations

The Vlasov–Maxwell (VM) equations have been solved by the forward semi-Lagrangian (FSL) method to calculate the argon ion beam angular distribution in the dense plasma focus (DPF) device. The validity of the VM employment was investigated through the Dreicer field, the mean free path, and the Debye length of the plasma pinch. The simulations have shown that the ion beams were emitted in a direct way at the initial pressures of 10 and 20 Pa. The ion beam angular distribution expanded for pressures bigger than 20 Pa. It has been shown that this was because the radial component of the electric field inside the pinch was increased and the axial component of the electric field was decreased by increasing the initial pressure of the working gas. The places of the ion beam micro-sources (hotspots) have been illustrated by means of the ion and electron density profiles.

Magnetic axis measurement of the high precision coil for the High Intensity heavy-ion Accelerator Facility electron cooler

Electron cooling method is used for the High Intensity heavy-ion Accelerator Facility (HIAF), in order to reduce the beam emittance and momentum spread of heavy ion beams, hence to improve the accuracy and luminosity of nuclear physics and atomic physics experiments. The magnetic field homogeneity of the cooling section is the key parameter related to the cooling effect. A new type of cooling section solenoid composed of several coils was used in the HIAF electron cooling device to produce a high parallelism magnetic field. In this paper, a device for the magnetic field axis measurement of high-precision coils is presented. The geometric symmetrical axis of the coil is measured by a positioning device. The radial and axial magnetic field distribution in the center plane of the coil is measured by the rotating Hall probes. Finally, the relative angle between the coil magnetic field axis and the geometric symmetrical axis is calculated by the measurement results. The accuracy of the measured angle is within ±0.10 mrad. The measured angle of the prototype coil is (1.28±0.10) mrad, which satisfies the physics requirement.

Transverse electron cooling of heavy molecular ions

Transverse electron cooling of heavy molecular ions has been studied at the Test Storage Ring (TSR). Electron beams from a cold GaAs:(Cs,O) photocathode, with kinetic energies down to 31 eV, have been used for cooling of singly-charged ions of masses up to 41 u. We believe that these are the heaviest singly-charged ions for which successful electron cooling has been reported so far. Transverse ion-beam emittances ≪1 μm were reached after typically several seconds of cooling time. The measured transverse cooling rates agree with a simple binary-collision model, assuming a transverse electron temperature of approximately 1 meV/kB. The results serve as benchmark for electron cooling at the new Cryogenic Storage Ring, which uses the same photocathode electron source and is targeting singly-charged ions of even higher mass.3 MoreReceived 10 January 2021Accepted 29 March 2021DOI:https://doi.org/10.1103/PhysRevAccelBeams.24.050101Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Open access publication funded by the Max Planck Society.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasBeam coolingBeam diagnosticsPhysical SystemsAccelerators & storage ringsElectron sourcesStorage ringsAccelerators & Beams

Study the effect of cathode electrode aperture shapes on ion beam properties using SIMION program

Abstract This work was concerned with a simulation study of different cathode electrode aperture shapes (pierce, reversed pierce, cone, reversed cone, triangle, reversed triangle, rectangle, circle, and sphere), which confirms that, pierce and cone shapes are the best extraction apertures. The minimum values of ion beam diameter and ion beam emittance, at collector plate which placed at 30 mm distance from cathode electrode were obtained using pierce and cone shapes. Also, the distance of the ion beam trajectories focal point was studied using different shapes for cathode aperture, which found to be decrease with increasing of the voltage applied to the cathode electrode. The main parameter in this study was the applied voltage to the cathode electrode. It was found that the observed changes on the ion beam parameters in the range 100 - 1500 V, but higher than these values the behavior of diameter, emittance and focal point of the ion beam were quasi-saturated. Also, it was found that the general behavior of ion beam diameter and its emittance nearly the same.

Ion Acceleration Parameter of the Plasma Focus Device

High-energy ion beam emission above megaelectronvolts from the plasma focus strongly correlated with the transient impedance developed across the plasma column. Ion acceleration parameter is formulated based on the experimental ion spectrum coupled to the pinch simulation, to estimate the mean ion energy E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mn</sub> from the accelerating potential V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</sub> . The experimental plasma impedance of 200- 500 mΩ sets off E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mn</sub> =(3→ 8)V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</sub> for sub-kJ to MJ-scale plasma focus devices. Adjustment of the parameter during the radiation phase speeds up or slows down E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mn</sub> and therefore alters the acceleration characteristics of the plasma focus ion emissions. Simultaneously, extensive measures through the magnetic spectrometry along with the space charge formulation on a diode ensure a reasonable level of the data quality on plasma focus ion beams.

Effect of filling gas on hard x-rays and ion beam emission from a 2 kJ plasma focus device

ABSTRACT The effects of the atomic number of the fill gas on hard x-ray and ion beam emission from a 2.2 kJ plasma focus were studied. Hydrogen, Nitrogen and Argon gases were used in the experiment. The anode voltage and discharge current were measured to calculate plasma inductance and to study the pinching regime in the three gases. The results showed that the heavier gas in the machine increases the duration of x-ray radiation, ion beam emission, and results in larger pinching plasma inductance. The Lee model suggests that the increase in the pinching plasma inductance can be explained by the occurrence of radiation collapse in the pinch operated with Argon gas. It is postulated that the occurrence of anomalous plasma heating may stop plasma compression and prevent the plasma from a complete collapse to reach near-zero radius.

Dynamics of ion beam emission in a low pressure plasma focus device

The plasma that accelerates and compresses in the formation of the pinch in dense plasma focus devices has been found to be an abundant source of multiple radiations like ion beams and x-rays. In this work, the ion beam and x-ray emissions from a 2.7 kJ (13.5 kV, 30 µF) plasma focus device operated at pressure below 1 mbar were investigated. The time profile of the ion beam emission was analysed from the simultaneously measured ion beam, soft and hard x-ray signals using biased ion collectors, BPX 65 silicon PIN diode and a scintillator-photomultiplier tube assembly. Time resolved analysis of the emissions revealed that the emission of the ion beam corresponded to several different pinching instances. Two components of the ion beam were identified. An ion beam of lower energy but higher intensity was emitted followed by an ion beam of higher energy but lower intensity in the first plasma pinch. The ion beam emitted from the first plasma pinch also has higher energy than subsequent plasma pinches. The emission was found to be associated with the amplitude of voltage spike. The results from ion beam and electron beams suggest that they were emitted by the same localized electric field induced in the pinched plasma. The strongest plasma focus discharge indicated by sharp voltage spike of high amplitude and highest ion beam energy were both observed at 0.2 mbar. The average energy of the ion beam obtained is (53 ± 13) keV. At this optimum condition, the ions beam with the highest energy also led to the highest hard x-ray emission.

Optimization of Vertical Acceptance of the Static Mass Analyzer

Axial aberration of the ion-optical system of a static mass analyzer is one of the factors limiting the transmittance and sensitivity of the device because of a need in significantly decreasing the vertical component of the ion beam emittance to get the required mass spectral resolution. We described an algorithm for selecting the optimal collimating system of the mass analyzer, which effectively decreases the contribution of axial aberration with minimal loss of the intensity of mass spectral lines.

Efficacy of radial matching section in enhancing RFQ cooler acceptance and optimization of its injection optics

Radio Frequency Quadrupole (RFQ) cooler is a device used for reducing transverse and longitudinal emittance of ion beams. The cooler employs a time varying field and as a result of which the acceptance ellipse, as seen by the beam while entering the cooler, is dependent on the RF phase. Acceptance ellipses having different orientations corresponding to the changing RF phase have a much smaller phase independent central overlapping area, so the real transmission for an injected DC beam into the RFQ cooler gets reduced. In RFQ linacs radial matching section has long been used for matching “time independent” DC input beam to the “time dependent” RF structure. Our simulation study shows that a similar radial matching section at the entrance of RFQ cooler can enhance the transmission for a DC beam into the RFQ cooler. Optimization of length of the radial matching section and the corresponding deceleration and injection optics shows an enhancement of more than two times in the area of time independent acceptance ellipse for ions over a mass range of 0A=4 to 240. Such innovative design could play a significant role in experiments with rare ion beams which are produced in miniscule quantities.

Negative Ion Beam Emittance Calculations

Computer simulations are commonly used to support design and optimisation of powerful negative ion sources for the needs of future thermonuclear reactors like e. g. ITER. The aim of the paper was to study changes of produced beam quality (described by its emittance and brightness) with the geometry of the extraction system as well as extraction voltage. A two-dimensional Particle-in-Cell (PIC) method based code was applied to model Hions and electrons extraction from the ion source plasma chamber through the opening with bevelled surface. The root-meansquare emittance of the extracted beam was calculated according to Chasman and Lapostolle approach. Ion beam phase space portraits were also presented to enrich the discussion. Growth of ion (electron) beam emittance was observed both with the increasing radius of the extraction opening and the inclination of its bevelled surfaces. This degradation of beam quality is partially balanced by increasing extracted Hion current. On the other hand, increasing length of the extraction channel improves the beam quality. It was demonstrated that for wider extraction opening the Hion beam consist of two parts coming form the two different regions of the chamber. According to calculated beam brightness the optimal wall inclination was found to be near 26o in the studied case. The decrease of the beam emittance saturates for larger channel length values. In the considered case the optimal channel length was h = 1.7 mm. The evolution of ion beam emittance and brightness shows that the best beam quality is achieved for extraction voltages between 0.5 kV and 2 kV.

Halo removal experiments with hollow electron lens in the BNL Relativistic Heavy Ion Collider

A hollow electron beam has been proposed as an active control tool to remove the beam halo from high-energy, high-current hadron or ion machines (such as the High-Luminosity Large Hadron Collider). To study the halo removal rate and assess the effect on the ion beam core, one of the two electron lenses in the Relativistic Heavy Ion Collider was changed from a Gaussian beam profile to a hollow profile. We describe the design and verification of the hollow electron beam parameters as well as the methods to minimize the hollow beam profile distortions, which can result in an ion beam emittance increase. The hollow beam alignment with the ion beam by using a backscattered electron detector has been demonstrated. Furthermore, experiments were carried out to explore the efficiency of the halo removal by scanning the current and inner radius of the hollow electron beam, which is pulsed either every turn or every nth turn. The effects of the hollow electron beam on the ion beam emittance and luminosity were also assessed experimentally by scanning the inner radius of the electron beam.

Ion-beam Investigation in a 1.5-kJ Dense Plasma Focus Device

An investigation of energetic ion beam emission from a low-energy (1.5 kJ) Mather-type plasma focus (PF) device operating with argon gas is studied with an operating pressure ranging from 2 × 10−2 to 1 Torr. The device has been energized by 30.84-μF capacitors charged up to 10 kV, giving a peak discharge current up to 120 kA with a rise time of 3 μs. A Faraday cup (FC) and its operation has been studied. This device is utilized to perform time-of-flight (TOF) measurements in order to characterize the beams of charged particles. The FC is placed at 20 cm from the tip of anode electrode at 0° with respect to anode axis to detect the ions. The FC operating in bias ion collector mode has been developed for measuring and characterizing pulsed ion beam. Energy and velocity of ions are determined with the TOF method, taking into account distance from the center electrode to the detection plane. The surface morphology of the pristine and irradiated ZnOCo0.04 samples is investigated as imaged by scanning electron microscope (SEM). The untreated sample showed rather relatively smooth surface; meanwhile, the SEM micrographs of bombarded samples display numerous small voids on the surface of the ZnOCo0.04 samples as a result of ion beam emission from PF device. X-ray fluorescence analysis showed that there are some new elements appeared on the surface of the sample after exposed to the ion beam; these elements and their concentrations are recorded. The surface roughness values for the pristine and the irradiated ZnOCo0.04 sample with Ar ion beam at different plasma shots are measured. A Vickers microhardness tester is used to measure the surface hardness, and the results demonstrate a significant increase in the hardness depending on the ion dose and decreases by increasing the applied load at 0° angular position.

Ion Beam Emittance for an Ion Source with a Conical Hot Cavity

Ion Beam Emittance for an Ion Source with a Conical Hot Cavity

First results of upgraded beam emission spectrometer on EAST

The beam emission spectroscopy (BES) system that shares the collection optics with the core charge exchange recombination spectroscopy (cCXRS) has recently been upgraded on EAST. The enhanced system aims at the simultaneous measurements of the neutral beam emission from the co-current and counter-current neutral beam injection (NBI) as well as the active charge exchange line (Dα, n = 3→2, 656.1 nm) from the interaction of the main ions and the injected neutral beam. The operating spectral band of the system is 656.1 ± 6 nm, with respect to the maximum Doppler shift and stark splitting induced by the highest energy of 80 keV for deuterium beam. Strong edge Dα line is effectively suppressed by one curved chromate strip (˜3% transmission and ˜83 μm width) on the fused silica. Main ion Dα emission and beam emission spectra are acquired simultaneously without any saturation of the signal on the detector. In this paper, an overview of the upgraded spectrometer will be shown and the first experimental results are presented.