Accelerated Ion Beams Research Articles

Temperature stabilization of a K110 variable energy cyclotron magnet.

For a large-scale cyclotron using normal conducting magnet coils, 10 h or more are required to obtain a highly stable magnetic field because heat transfer from the coils changes the temperature of the magnets gradually. To suppress the heat transfer and stabilize the magnet temperature in the TIARA K110 cyclotron, water-cooled copper plates were inserted between the main coil and the magnetic yoke. The heat generated by the main coil depends on its circulating current, which depends on the accelerated ion beam. To stabilize the magnet temperature, a technique was developed to control the temperature of the cooling water of the copper plates depending on the main coil current. Consequently, the temperature of the magnet was stabilized successfully to 24 ± 0.3 °C for various ion beams, and the magnetic field was maintained at ΔB/B = 1 × 10-5 after a few hours from initiating cyclotron operation.

IAEA activities in support of nuclear physics research and applications

Facilitation of development and promotion of nuclear applications for peaceful purposes and related capacity building are among the IAEA missions where Physics Section contributes most. The relevant activities fall under the IAEA’s program ‘nuclear science’ and cover four main thematic areas: applications of particle accelerators, sustainable utilization of research reactors, controlled fusion research and technology, and nuclear instrumentation. The Section also operates the Nuclear Science and Instrumentation Laboratory (NSIL) at Seibersdorf, located approximately 40 km south of Vienna. NSIL’s primary mission is to assist IAEA Member States to establish, operate and maintain various nuclear instrumentation and spectrometry-based techniques in support of a wide range of applications such as materials This paper will illustrate through a number of selected examples how the IAEA supports nuclear physics research and diverse applications in order to address key development priorities in many areas of societal importance and economic growth of the developing countries. In addition, some future plans on enhancing capabilities of the Nuclear Science and Instrumentation Laboratory as part of Physics Section will be highlighted, in particular by establishment of the neutron science facility and considerations for a compact ion beam accelerator.

Wide-range tracking and LET-spectra of energetic light and heavy charged particles

We developed a highly-selective technique to measure the energy loss and linear-energy-transfer (LET) spectra of energetic charged particles in high-resolution and over a large collection of particle-event types. Precise and wide-range spectral and tracking measurements were performed with a single semiconductor pixel detector. The quantum-counting sensitivity, high-granularity and per-pixel spectrometric response of the Timepix ASIC chip enable the detailed spectral-tracking registration of single charged particles across the detector semiconductor sensor. Both the deposited energy along the particle trajectory (energy loss) and the path length of the particle track across the semiconductor sensor are precisely measured for each particle. This allows for the determination of the particle LET in silicon in high accuracy and over a wide-range of energies, particle types and directions. The tracking and energy loss response together with the resolving power at the particle-event level make it possible to selectively provide LET distributions of the light and heavy charged particle components in mixed-radiation and omnidirectional fields. This technique applies to energetic (E > 10 MeV/u) charged particles generating tracks greater than the pixel size and incident at non-perpendicular direction (>20∘) to the sensor plane. The technique applies also to electrons of energy above few MeV as well as highly energetic and minimum-ionizing-particles (MIPs). We make use of existing and in part newly collected data at well-defined radiation fields with proton and light ion beam accelerators. Flexible measurements, ease of deployment and online response are possible by the use of compact readout electronics such as the miniaturized radiation camera MiniPix (size < 8 cm, weight < 50 g) operable by any PC. Results are given for protons and light ions (He, C) of selected energies above 10 MeV/u and directions (2π FoV). We include also electrons (20 MeV). Selective and detailed LET spectra are produced over a wide range (10−1 to 102 keV/μm) in silicon.

A Study on the Performance of the Cryostat System for the 28-GHz Electron Cyclotron Resonance Ion Source at the Korea Basic Science Institute

The BIBA (Busan Ion Beam Accelerator) is a compact linear accelerator facility using the 28 GHz ECRIS (Electron Cyclotron Resonance Ion Source) at the KBSI (Korea Basic Science Institute). The superconducting magnets of the 28 GHz ECRIS produce high magnetic fields for strong confinement of plasmas in an ion source chamber. For stable operation of the superconducting magnets, performance of cryostat system is very essential. However, the cryostat system produces significant quantities of the heating due to conduction from room temperature. In addition, part of the X-ray radiation produced by the collisions of the electrons within the ion source chamber is absorbed by the cold mass of the superconducting magnet, leading to an additional heat load in the cryostat system. In this paper, a study on the performance of the cryostat system for 28 GHz ECRIS is performed to improve the cooling efficiency of the cryostat system.

Laser-driven collisionless shock acceleration of ions from near-critical plasmas

This paper overviews experimental and numerical results on acceleration of narrow energy spread ion beams by an electrostatic collisionless shockwave driven by 1 μm (Omega EP) and 10 μm (UCLA Neptune Laboratory) lasers in near critical density CH and He plasmas, respectively. Shock waves in CH targets produced high-energy ∼50 MeV protons (ΔE/E of ≤30%) and 314 MeV C6+ ions (ΔE/E of ≤10%). Observation of acceleration of both protons and carbon ions to similar velocities is consistent with reflection of particles off the moving potential of a shock front. For shocks driven by CO2 laser in a gas jet, ∼30 MeV peak in He ion spectrum was detected. Particle-in-cell simulations indicate that regardless of the target further control over its density profile is needed for optimization of accelerated ion beams in part of energy spread, yield and maximum kinetic energy.

Modification of diazoquinone-novolac photoresist films by boron ion implantation

Diazoquinone-novolac photoresist films implanted with B+ ions were studied by the method of attenuated total reflection (ATR). Films of positive photoresist FP9120 with a thickness h of 1.0 and 2.5 mm were deposited by centrifuging on p-type silicon plates with (111) orientation. Implantation with 60 keV B+ions in the dose range of 1015–1016 cm–2 in the constant ion current mode (current density 4 mA/cm2 ) was carried out at room temperature in a residual vacuum not worse than 10–5 Pa using the «Vesuvius-6» ion beam accelerator. The attenuated total reflection spectra were recorded in the range 400 – 4000 cm–1 by ALPHA spectrophotometer (Bruker Optik GmbH, Germany) at room temperature. It was shown that ion implantation leads to intensive transformation of the photoresist beyond the range of ions, which is characterized by the appearance in the spectrum of intense bands with peaks at 2151 and 2115 cm–1, due to stretching vibrations of double cumulative bonds, in particular С——С——О. In the implanted samples, a shift to the low-energy region of the maxima of the stretching vibrations of C—H bonds, plane deformation vibrations of O—H bonds and pulsating vibrations of the carbon skeleton of aromatic rings as well as the redistribution of intensities between closely spaced maxima, were observed.

A hybrid simulation of carbon ion beams generation, acceleration and the evaluation of the ignition condition

We have investigated the acceleration of quasi-monoenergetic ion beams. LPIC++ code has been used to simulate the radiation pressure acceleration hole-boring mechanism. To reach the quasi-monoenergetic ion beam used for ionic fast ignition, the beams with low energy spread and suitable peak energy are the best choice. Effective parameters including intensity for laser, thickness, density and charge state for foil have been evaluated to have a stable acceleration. Based on the results, optimal quasi-monoenergetic ion beams of the laser with an intensity of 1.9 ×1021 W / cm2, pure carbon foil with 0.56μm thickness, and density 15 have been selected with the average energy 624 MeV and 720 MeV. Also, by applying the Deira-4 code, the potential of the aforementioned beams with different ignition energies from 8.5-11 kJ has been studied. For the pre-compressed DT fuel capsule with the density 300 g/cm3 and initial temperature 1keV, the ignition conditions have been considered. Subsequently, we found that the ignition threshold conditions for multi-peak beams are more favorable than those of the ideal single-peak beams. It is shown that the ignition energy threshold of multi-peak beams is about 10 kJ, which is more than the ignition energy for the ideal single-peak beams that are close to 7 kJ.

Acceleration of high charge ion beams with achromatic divergence by petawatt laser pulses

Author(s): Steinke, S; Bin, JH; Park, J; Ji, Q; Nakamura, K; Gonsalves, AJ; Bulanov, SS; Thevenet, M; Toth, C; Vay, JL; Schroeder, CB; Geddes, CGR; Esarey, E; Schenkel, T; Leemans, WP | Abstract: © 2020 authors. Published by the American Physical Society. We present a study of laser-ion acceleration, where an increased laser spot size leads to sheath field geometries that accelerate ion beams of narrow and achromatic divergence at unprecedented charge densities, resulting from the high aspect ratio of the laser spot size to the acceleration distance. Matching the laser pulse length to the transverse laser spot size mitigated laser sweeping across the target front side and optimized the acceleration, with maximum energies deviating significantly from a linear intensity scaling.

Beam commissioning and analysis of a continuous-wave window-type deuteron radio-frequency quadrupole

As high-intensity beams are required for various applications, high-power, high-current, continuous-wave (CW) radio-frequency quadrupole (RFQ) accelerators have become a research focus in recent years and also a direction for development in the future. To master and accumulate the advanced technology in design, fabrication and operation of high-current CW RFQs, the RFQ group at Peking University has built a window-type CW RFQ, operating at 162.5[Formula: see text]MHz, to accelerate a 50-mA deuteron beam from 50[Formula: see text]keV to 1[Formula: see text]MeV. It is the first relatively high-frequency window-type CW RFQ in the world. A [Formula: see text] ion beam extracted from an electron cyclotron resonance (ECR) ion source was used for the beam commissioning because deuteron beam acceleration will produce a serious radiation risk. We compared and analyzed the measurement results obtained during the beam commissioning with simulations. The data show good consistency in many respects. For the discrepancies, we explain the issues in detail. We achieved stable and robust acceleration of about 1.5[Formula: see text]mA CW [Formula: see text] for 1[Formula: see text]h. Finally, we discuss the differences between [Formula: see text] ion beam acceleration and deuteron beam acceleration.

Achievement of high power and long pulse negative ion beam acceleration for JT-60SA NBI.

Long pulse acceleration of hydrogen negative ion beams with the power density over 70 MW/m2 and the pulse length over 100 s has been demonstrated for the first time by using a multi-aperture 3-stage accelerator. Such long pulse acceleration was achieved by integrating the design of beam optics and voltage holding capability to meet the requirements of JT-60SA. By using the newly designed accelerator for JT-60SA, voltage holding at 500 kV with beam acceleration was stably sustained even after 5 g of cesium was seeded, and heat load on each acceleration grid was reduced below the allowable level for long pulse, less than 5% of total acceleration power. As a result, 500 keV, 154 A/m2 for 118 s beam acceleration was achieved, which satisfies the requirement of the negative ion source for JT-60SA. This pulse length of such high-power density beams is longest in the world. In addition, the result contributes to the long pulse acceleration of multi-stage electrostatic accelerators, such as 1 MeV negative ion accelerator for ITER.

Acceleration of carbon ion beams by an ultraviolet laser under conditions relevant for ion fast ignition of inertial fusion

The properties of carbon ion beams produced by a 100-kJ, 1-ps, KrF ultraviolet laser under conditions relevant for ion fast ignition (IFI) of DT fusion are numerically investigated using the 2D3V particle-in-cell code, and the possibility of achieving the ion beam parameters required for IFI is tested. The numerical simulations of carbon ion acceleration were carried out for flat carbon targets of various thicknesses (LT) and for various laser beam apertures (dL) on the target, while the laser pulse duration and energy were fixed. It was found that both the radiation pressure acceleration (RPA) mechanism and the sheath acceleration mechanism significantly affects the characteristics of the ion beam, with the RPA dominating in the case of thicker targets (LT ∼ 10–30 μm). The ion beam parameters depend to a significant extent on the target thickness and the distance from the target. The mean and maximum ion energy decrease with the increase of LT from 3 μm to 30 μm, while the ion beam intensity, the beam energy fluence and the total energy of the “useful part” of the ion beam (with an aperture ⩽ 50 μm) reach maximum values at LT ∼ 5–10 μm. For the optimal value of LT and a small distance x from the target (x ∼ LT), the ion beam parameters are close to or higher than what is required for IFI. However, due to the angular divergence of the ion beam, the beam intensity and fluence decrease with an increase in the distance from the target, and at x ⩾ 0.5 mm the beam parameters are below the values required for fusion ignition. To reach these values, higher laser energies and/or more sophisticated schemes of ion acceleration are required.

Shielding of energy deposition by ablation of plastics under intense pulsed ion beam irradiation

With high power density in solid targets, intense pulsed ion beam with a pulse length of hundreds of ns and cross-sectional energy density of several J/cm2 may induce surface ablation and this effect can be used for thin-film preparation and nanopowder synthesis. Nevertheless, with ablation by the pulsed ion beam, the energy deposition of ions in targets may be affected and this further toughens the analysis of ablation and related material response in applications and ion beam diagnostics. In this study, the energy deposition of nanosecond pulsed ion beam composed of protons and carbon ions on stainless steel and plastics on BIPPAB-450 pulsed ion beam accelerator was investigated with infrared diagnostics. It is revealed that on plastics, under nanosecond IPIB irradiation with energy density of 1.5 J/cm2, ablation plume can be formed at the beginning stage of beam irradiation and the ablation plume may impose strong stopping to the ions in the pulsed ion beam and thus the energy deposition of the ion beam is shielded from reaching the target with over 80% of the beam energy screened. The influence of this energy shielding effect on applications such as beam measurement and material treatment was discussed reasonably.

Focusing of intense pulsed ion beam by magnetically insulated diode for material research

The cross-sectional distribution and focusing properties of intense pulsed ion beam by an active magnetically insulated diode for material modification is presented. The ion beam accelerator BIPPAB-450 uses the surface flashover of polymers as the ion source, generates intense pulsed ion beam composed of protons and carbon ions with a pulse length of 120 ns, ion energy up to 450 keV, energy density up to 3 J/cm2. By the strong flash thermal effects on the surface of materials, the ion beam can be used for the surface treatment and ablation related application. The cross-sectional distribution of the ion beam was measured by infrared imaging method. The results on the focusing of the diode reveal the distribution in the plasma generation on the anode surface. Comparative study on beam focusing during transportation was made and it is demonstrated that by using a copper beam limiter, the maximum beam energy density can be increased by a factor of nearly 1.5. The change in the beam phase-space distribution by the limiter is also exhibited and the influence on beam diagnostics and optimization is discussed reasonably.

The ablation of plastics by intense pulsed ion beam

With strong flash heating effects, intense pulsed ion beam (IPIB) may induce ablation on the solid surface and it is the basis of applications such as surface cleaning, nanopowder preparation and thin-film synthesis with IPIB. In this study, the ablation of polymethyl methacrylate (PMMA) by IPIB was investigated with varied beam energy density on pulsed ion beam accelerator BIPPAB-450 to study the ablation of IPIB under strong ablation. With thermal imaging measurement, it is revealed that when energy reaches a certain threshold, the ablation plume generated on the target surface may impose a shielding effect on the ion beam energy from depositing in the target. It is verified by thermal field simulation that for the low evaporation temperature and high thermal resistance, intense ablation plume may be generated on the surface of plastics under low IPIB energy density or at the early stage of IPIB irradiation. Ablation mass measurement demonstrated that under irradiation of IPIB with a pulse length of 120 ns, ion energy up to 450 keV, energy density up to 3.8 J/cm2, the mass loss of the target increases with the rise of IPIB energy density. Under the irradiation of a series of pulses, the mass loss of PMMA increases proportionally. Unlike ablation on metals by direct beam energy deposition, the ablation of plastics by IPIB endures more stages and the ablation may be more achieved by the heated ablation plasma by beam irradiation.

Multi-jet gas cooling of in-beam foils or specimens: CFD predictions of the convective heat-transfer coefficient

An experiment was designed to investigate the possible enhancement of the convective heat-transfer coefficient by utilizing multiple, parallel jets in the cooling of a small heated surface, such as typically induced by an accelerated ion beam on a thin foil or specimen. The hot spot was provided using a small electrically heated plate. It was found that heat-transfer calculations by means of simple empirical methods based on dimensional analysis are not useful in this case and that advanced computational fluid dynamics (CFD) mod-elling is essential to interpret the results. It is shown that enhanced convective cooling can indeed be obtained with a multi-jet configuration as compared to a single-jet configuration but only under very selective conditions. An improperly designed multi-jet configuration can also provide significantly reduced cooling relative to the single-jet case and the estimation of the behavior of any particular jet geometry is eminently non-intuitive. CFD provides acceptable quantitative results and seem to be the only tool available to gain an understanding of these complex flows where simple models and “rules of thumb” cannot be relied upon. – LA-UR-18-29455

Laser-driven neutrons for time-of-flight experiments?

Neutron beams, both pulsed and continuous, are a powerful tool in a wide variety of research fields and applications. Nowadays, pulsed neutron beams are produced in conventional accelerator facilities in which the time-of-fight technique is used to determine the kinetic energy of the neutrons inducing the reactions of interest.In the last decades, the development of ultra-short (femtosecond) and ultra-high power (&gt; 1018W/cm2) lasers has opened the door to a vast number of new applications, including the production and acceleration of pulsed ion beams. These have been recently used to produce pulsed neutron beams, reaching fluxes per pulse similar and even higher than those of conventional neutron beams, hence becoming an alternative for the pulsed neutron beam users community. Nevertheless, these laser-driven neutrons have not been exploited in nuclear physics experiments so far.Our main goal is to produce and characterize laser-driven neutrons but optimizing the analysis, diagnostic and detection techniques currently used in conventional neutron sources to implement them in this new environment. As a result, we would lay down the viability of carrying out nuclear physics experiments using this kind of sources by identifying the advantages and limitations of this production method.To achieve this purpose, we plan to perform experiments in both medium (50TW@L2A2, in Santiago de Com-postela) and high (1PW@APOLLON, in Paris) power laser facilities.

First acceleration of heavy ion beams with a superconducting continuous wave HIM/GSI CW-linac

In the future a new superconducting (sc) continuous wave (cw) high intensity heavy ion Linac should provide ion beams with a max. beam energy above the coulomb barrier for the Super Heavy Element (SHE) program at GSI Helmholtzzentrum für Schwerionenforschung. Key features of this new Linac are the acceleration of different ions from protons to uranium as well as a smooth energy variation from 3.5 to 7.3 MeV/u for design ions with a mass-to-charge ratio A/q = 6 and even above for lighter ions. As a first step a newly developed superconducting 15-gap Crossbar H-cavity (CH-cavity) operated at 217 MHz has been successfully tested with heavy ion beam up to the design beam energy of 1.85 MeV/u for the first time. The design energy gain of 3.5 MV within a length of less than 70 cm has been validated with heavy ion beams of up to 1.5 pμA. The measured beam parameters showed excellent beam quality, while a dedicated beam dynamics layout provides beam energy variation between 1.2 and 2.2 MeV/u. The beam commissioning is a milestone of the R&D work of Helmholtz Institute Mainz (HIM) and GSI in collaboration with Goethe University Frankfurt (GUF) and the first step towards a sc heavy ion cw-Linac with variable beam energy. The first tests under cryogenic conditions of the next two CH-cavities have already been started at GUF in a vertical cryostat. The results of the first successful heavy ion beam acceleration with a superconducting CH-cavity will be presented.

Preface

The 14th International Conference on Heavy Ion Accelerator Technology, HIAT’18, took place at Institute of Modern Physics (IMP) of the Chinese Academy of Sciences, China, from Sunday to Friday, 21st to 26th Oct., 2018.HIAT conference provides a platform for scientists, engineers, students and industrial partners to present and discuss the latest developments of heavy ion accelerator. Over 100 delegates and 20 industry exhibits present at this conference. Following the tradition of the HIAT conference series, scientific program consists of invited and contributed oral sessions, poster sessions and discussion sessions.IMP was founded in Lanzhou in l957. As a national laboratory, IMP operates one major national research facility - the Heavy Ion Research Facility at Lanzhou (HIRFL). A series of remarkable results have been obtained at HIRFL. After a half century of development, IMP has become the most important research center for heavy ion sciences in China. Based on the developments and experience with heavy ion beam accelerators, IMP also takes charge of several new national projects: HIAF, CiADS. We have established active and fruitful collaboration with more than 40 universities and institutions in the worldwide.We thanks for your participation. We are also deeply grateful to our Exhibitors and Sponsor companies for their financial support.SincerelyYuan He Co-chair, HIAT2018

Ion beam analysis of fusion plasma-facing materials and components: facilities and research challenges

Following the IAEA Technical Meeting on ‘Advanced Methodologies for the Analysis of Materials in Energy Applications Using Ion Beam Accelerators’, this paper reviews the current status of ion beam analysis (IBA) techniques and some aspects of ion-induced radiation damage in materials for the field of materials relevant to fusion. Available facilities, apparatus development, future research options and challenges are presented and discussed. The analysis of beryllium and radioactivity-containing samples from future experiments in JET or ITER represents not only an analytical but also a technical challenge. A comprehensive list of the facilities, their current status, and analytical capabilities comes alongside detailed descriptions of the labs. A discussion of future issues of sample handling and the current status of facilities at JET complete the technical section.To prepare the international IBA community for these challenges, the IAEA technical meeting concludes the necessity for determining new nuclear reaction cross-sections and improving the inter-laboratory comparability by defining international standards and testing these via a round-robin test.

Beam Dynamics Simulation in the LINAC-100 Accelerator Driver for the DERICA Project

The results of uranium ion beam dynamics simulation in front-end and superconducting sections of the accelerator-driver LINAC-100 for the new rare isotope facility DERICA (JINR, Dubna) are presented. The optimum parameters are chosen for the buncher accelerator with radiofrequency quadrupole focusing (RFQ) for uranium ion beam acceleration from the ion source up to the energy of 570 keV/nucleon. LINAC-100 modular superconducting part layout for uranium beam acceleration from 3 to 100 MeV/nucleon is obtained. The energies for the stripper section installation are chosen.