Intense Ion Beams Research Articles

Experimental setup for interaction between highly charged ions and laser-produced plasma near Bohr velocity energy region

Ion energy loss in the interaction between highly charged ions and dense plasma near Bohr velocity energy region is one of the important physical problems in the field of high-energy density physics driven by intense heavy ion beams. Based on the 320 kV experimental platform at the Institute of Modern Physics, Chinese Academy of Sciences, a new experimental setup was built for the research of interaction between ions and laser-produced plasma near the Bohr velocity, where the ion energy loss and charge state distribution can be experimentally investigated. In this paper we introduce the new setup in detail, including the generation and controlling of pulsed ion beam ( ≥ 200 ns); the preparation of high-density laser plasma target (10<sup>17</sup>—10<sup>21</sup> cm<sup>–3</sup>); the diagnostics of plasma and the developed high energy resolution ion measurement system (< 1%). In the experiment, the charge distribution of Xe<sup>15+</sup> ions with 4 MeV penetrating through the laser-produced Al plasma target is measured. The charge-state analysis device observes different results without and with the plasma, in which the outgoing Xe ion charge-state changes correspondingly from the 15+ to 10+, thus the electron capture process is believed to be dominant. In addition, the proton energy loss is also measured by using the magnetic spectrometer, showing that the experimental energy loss is about 2.0 keV, 30% higher than those theoretical predictions , which can be attributed to the fact that in the near Bohr velocity energy regime, the first-order Born approximation condition is not valid, thus the Bethe model and SSM model are inapplicable to the experimental results. In future, a systematic study will be performed based on our ions-plasma ineteraction setup, and the energy loss and charge state data will be introduced.

Slow extraction modelling for NIMMS hadron therapy synchrotrons

The Next Ion Medical Machine Study (NIMMS) is an umbrella R&D programme for CERN accelerator technologies targeting advanced accelerator options for proton and light ion therapy. In collaboration with the European programme HITRIplus, one area of study is slow extraction which is required to deliver a uniform beam spill for radiotherapy treatment. Several techniques use the third-order resonance to extract hadrons; these include betatron core driven extraction and radiofrequency knock-out. Flexible simulation tools using these techniques were prepared and initially benchmarked with results from the literature that used the Proton-Ion Medical Machine Study (PIMMS) design. The limits of the current PIMMS design were then pushed to evaluate its compatibility to deliver 10x higher intensity ion beams, and using increased extraction rates.

Integration of the scattering chamber of the NUMEN experiment

The NUMEN experiment points to measure Double Charge Exchange reaction (DCE) cross sections with heavy-ion beams interacting with specific isotopes of interest for Neutrinoless Double Beta Decay process (0νββ). To achieve this, NUMEN requires a complete upgrade to MAGNEX spectrometer in INFN-LNS and a high intensity ion beam. This work focuses on the design of a new scattering chamber where the ion beam will interact with the target precisely positioned by an automatic system. The target will be cooled by a custom system based on HOPG and a cryo-cooler. The fist integration of the chamber with all its components has been done at INFN section of Turin to check compliance with the requirements and to study the procedures for the target replacement. Some results of this tests will be presented.

Improved 26Al and 10Be cathode performance and data analysis at KIST

Addition of a metal powder interface between solid metal cathode and sample powder was investigated for26Al and10Be analysis by accelerator mass spectrometry (AMS). Cathode quality and consistency improved, leading to more intense, stable and longer-lived ion beam currents, while cathode matrix sensitivity to powder fineness, homogeneity and precipitate to metal powder mixing ratios was reduced. Now, ratios of 1:0.75–2 for Al2O3 + Ag in Cu cathodes and 1:0.9–4 for BeO + Nb in Al or Cu cathodes are optimal. Furthermore, a survey of sputter energies showed that 5 keV–6 keV greatly increases cathode life, current stability, and cathode consumption efficiency for both BeO and Al2O3as opposed to the widely used 7 keV for High Voltage Engineering SO110 ion sources. Finally, some data flagging criteria that have recently been incorporated into the26Al and10Be internal data analysis software are explained.

Study and improvements of a radially coupled coaxial Fast Faraday cup design toward lower intensity beams

A radially coupled coaxial fast Faraday cup design was presented in Carneiro et al. [Int. J. Mod. Phys. A 34(36), 1942013 (2019)] for high-intensity non-relativistic proton beams. In this work, we discuss a modification of that design in the context of a relatively lower intensity ion beam for longitudinal charge profile measurements. Particle-in-cell and time domain electromagnetic simulations of the new design with a focus on avoiding field dilution while generating enough signal for relatively lower intensity ion beams at the upcoming High Current Injector Program at the Inter-University Accelerator Center, New Delhi [A. Roy, Curr. Sci. 76(2), 149–153 (1999); Kanjilal et al., in 3rd Asian Particle Accelerator Conference (Pohang Accelerator Laboratory, 2004), p. 73], is discussed. Profile distortions from secondary electron emission are estimated, and strategies to suppress them are discussed.

Simulation of beam extraction and space charge effect in an electromagnetic isotope separator

Space charge effect of intense ion beam has critical influence on separation efficiency in the electromagnetic isotope separator. In this paper, a ribbon beam extraction system with slit electrodes for an electromagnetic isotope separator was designed and studied. The extracted beam currents were varied from 10 to 40 mA and the corresponding extracted beam energies were 40 keV and 100 keV respectively. The simulated output beam density distributions were used in the subsequent multi species particle transmission simulation with the space charge effect included. The separated isotope beam spot distributions at the focal plane were simulated under different space charge compensation factors and thus the optimum operation gas pressures in vacuum box were roughly estimated. For the case of high intensity and high power isotope beam collection, an isotope collector with a deceleration electrode was proposed to mitigate the effect of high power beam bombardment and the resultant temperature rising on the collector surface.

Comparison of gaseous contamination of thin tungsten and gold coatings deposited from ablated plasma generated by Intense Pulsed Ion Beams

The paper presents experimental results on C, N and O contamination in thin tungsten and gold coatings deposited on GaAs substrates from ablated plasma generated by intense pulsed ion beams accelerated in a magnetically insulated diode. The coating thickness was controlled by energy-dispersive X-Ray Fluorescence analysis. Depth profiles of C, N and O concentrations in the coatings were determined using quantitative Auger Electron Spectroscopy (AES) with ion sputtering. Non-destructive charged particle activation analysis via the nuclear reactions 12C(d,n)13N, 14N(d,n)15O and 16O(d,n)17F, induced by 3 MeV deuterons of extracted from a cyclotron was used to calibrate the AES determination of C, N and O. The gold coating was found to be devoid of detectable amounts of all gases, while carbon dominated by an order of magnitude over nitrogen and oxygen in tungsten coatings. Carbon contamination increased linearly with an increase in the number of ion shots applied. It was concluded that the main source of gas contamination is the residual atmosphere of the working chamber and the purest coatings can be obtained at the highest deposition rates per shot. A significant increase of oxygen admixture was found in the tungsten coatings after the samples were stored in the ambient atmosphere for 25 years. The storage did not affect the purity of the gold coating, but carbon seemed to diffuse from the Au/GaAs interface to the coating surface.

Carbonate clumped isotope analysis using isotope dilution

The large sample size requirement is a major obstacle while conducting the measurement of isotopic abundances in carbonates for clumped isotope thermometry using MAT 253 isotope ratio mass spectrometer employing McCrea type setup or improved break-seal method at a reaction temperature of 25 °C. A long integration time at high (∼10000 mV) major ion beam intensity permits the highest analytical precision but requires a large sample size for CO2. However, in several instances, carbonate availability is restricted in the natural environment like foraminifera, otoliths, ostracods, etc., in sediment cores, prohibiting the application of the thermometry. Here we introduce a new isotope dilution method for stable and clumped isotope analysis for small size carbonates at a precision of ±0.005‰. In this method, two reference carbonate materials (MAR J1 and OMC) are quantitatively mixed with known proportions or weight fractions. The high-temperature reference carbonate (MAR J1) is treated as a spike end member, whereas the low-temperature carbonate reference is considered as unknown. The spike is identified based on similarity in mineralogy with the sample and well-defined isotopic composition as constrained by its formation temperature. These two carbonates used here are internal laboratory standards and are homogeneous, independently ascertained based on long-term reproducibility of δ13CVPDB and δ18OVPDB values lying within 0.002‰ and 0.003‰ respectively. These two reference carbonate powders have δ13CVPDB and δ18OVPDB values, which differ from each other by ∼6.3‰. The Δ47 values of these carbonates are 0.395‰ and 0.587‰, respectively. In our experiment, we observe a linear relationship governing δ13CVPDB and δ18OVPDB values of a mixture with a known weight fraction; however, Δ47 values follow a non-linear mixing trend upon exceeding the weight fraction ≥0.4 of the low-temperature carbonate (OMC). The linear trend allows the prediction of the Δ47 value of the unknown carbonate powders using a binary mixing model within an acceptable precision of 0.01–0.02‰ necessary for clumped isotope measurement. This new approach provides an alternative method of analyzing small size (∼3 mg) carbonate powder extending the application of the break-seal method for analysis at major ion beam intensity of 10000 mV. Here we demonstrate the application of this method for accurate determination of both stable and clumped isotopic composition of various low-temperature carbonates, including a deep-sea coral, an otolith, and ETH-3 reference carbonate.

A velocity map imaging spectrometer for measuring absolute differential cross sections for ion-induced electron emission from molecules.

In this paper, we present a newly developed crossed beam experimental setup that utilizes the velocity map imaging (VMI) technique to simultaneously measure both the kinetic energy and emission angle of electrons emitted from atoms or molecules upon ion collision. The projectile ion beam with keV to MeV kinetic energy orthogonally crosses the neutral target beam produced by an effusion cell. The emitted electrons are extracted and analyzed by a multi-electrode VMI spectrometer. By monitoring the target density, the projectile ion beam intensity, and the beams' overlap, we are able to measure absolute differential cross sections for collision-induced electron emission from molecules. The characterization of the setup and the methodology will be presented as well as first results for electron emission from uracil upon 0.98 MeV/u 12C4+ collision.

Improving Photoelectrochemical Activity of Magnetron-Sputtered Double-Layer Tungsten Trioxide Photoanodes by Irradiation with Intense Pulsed Ion Beams.

The photoelectrochemical (PEC) activity of metal oxide photoelectrodes for water-splitting applications can be boosted in several different ways. In this study, we showed that PEC activity can be significantly improved with a double-layer (crystalline-amorphous) configuration of WO3 thin films irradiated with intense pulsed ion beams (IPIB) of a nanosecond duration. It was found that IPIB irradiation promotes the formation of crystalline and sponge-like WO3 structures on the surface. Due to an increase in the active surface and light scattering in irradiated samples, photocurrent generation increased by ~80% at 1.23 reversible hydrogen electrodes (RHE).

Charge breeder of Electron Cyclotron Resonance type: A new application to produce intense metal ion beams for accelerators

Metal ion beams are more and more requested by physicists (Nuclear Physics, Material Physics) for their experiments. At GANIL, they are produced by Electron Cyclotron Resonance (ECR) Ion Sources for the two accelerator machines: ECR4 & ECR4M (Sortais et al., 1989) [1] for the Cyclotrons and PhoenixV3 for the Linac (Thuillier et al., 2016) [2]. One of the challenges is to produce these beams with high global efficiency: today, total ionization efficiency varies between ∼1% and ∼28% regarding the method carried out. A new alternative would be the 1＋/N＋ method studied intensively for the past twenty years in the framework of Radioactive Ion Beam (RIB) production. In this article, the primary results leading to the proof of principle of that technique applied to the production of metal ion beams is presented.

Preliminary Study for Improving Electron Emission Threshold of Metallic Electrodes Treated by Intense Pulsed Ion Beam

Preliminary Study for Improving Electron Emission Threshold of Metallic Electrodes Treated by Intense Pulsed Ion Beam

Navigate Flying Molecular Elephants Safely to the Ground: Mass-Selective Soft Landing up to the Mega-Dalton Range by Electrospray Controlled Ion-Beam Deposition.

The prototype of a highly versatile and efficient preparative mass spectrometry system used for the deposition of molecules in ultrahigh vacuum (UHV) is presented, along with encouraging performance data obtained using four model species that are thermolabile or not sublimable. The test panel comprises two small organic compounds, a small and very large protein, and a large DNA species covering a 4-log mass range up to 1.7 MDa as part of a broad spectrum of analyte species evaluated to date. Three designs of innovative ion guides, a novel digital mass-selective quadrupole (dQMF), and a standard electrospray ionization (ESI) source are combined to an integrated device, abbreviated electrospray controlled ion-beam deposition (ES-CIBD). Full control is achieved by (i) the square-wave-driven radiofrequency (RF) ion guides with steadily tunable frequencies, including a dQMF allowing for investigation, purification, and deposition of a virtually unlimited m/z range, (ii) the adjustable landing energy of ions down to ∼2 eV/z enabling integrity-preserving soft landing, (iii) the deposition in UHV with high ion beam intensity (up to 3 nA) limiting contaminations and deposition time, and (iv) direct coverage control via the deposited charge. The maximum resolution of R = 650 and overall efficiency up to Ttotal = 4.4% calculated from the solution to UHV deposition are advantageous, whereby the latter can be further enhanced by optimizing ionization performance. In the setup presented, a scanning tunneling microscope (STM) is attached for in situ UHV investigations of deposited species, demonstrating a selective, structure-preserving process and atomically clean layers.

Study of beamlets extracted from a multi-aperture and five-stage acceleration system.

A beam optics study using the ITER-relevant high intense negative ion beams, such as 1MeV, 200 A/m2, has been performed experimentally and analytically using a multi-aperture and five-stage accelerator. Initially, multi-beamlets generated from this accelerator were deflected in various directions due to the magnetic field and space charge repulsion between beams and showed various divergences. These had limited the pulse length and the beam energy. Compensation methods of the beamlet deflections have worked effectively and contributed to achieving the ITER requirement, the divergence angle of <7 mrad, and the deflection angle of <1 mrad for 1MeV beam. The beam pulse has been gradually extended from 1 to 100s and is now going to a longer pulse based on these results. One of the remaining issues is to understand and suppress peripheral components of the beam, namely, the halo, and to reduce the local heat loads observed around the aperture edge. This halo component has been successfully distinguished from the beam core by using a newly developed beam emittance measurement system for high intense beams. By combining this measured beam emittance and the beam simulation, it was clarified for the first time that the halo components are generated in an area of 1mm width from the aperture edge.

Proceedings of the 19th International Conference on Ion Sources, Vancouver, BC, Canada, 2021

The 19th International Conference on Ion Sources was hosted by TRIUMF in Vancouver, BC, Canada, September 20 to September 24, 2021.The biennial conference series covers the physics and technology of ion sources for scientific research and applications. With the conference being the main event within the ion sources community, it offers a forum for the exchange of ideas and the establishing of collaborations. New developments and advancements have been presented and discussed. As in previous conferences of this series, all aspects of ion sources have been covered in the categories• Fundamental processes in ion sources and plasmas• Production of high intensity ion beams• Production of highly charged ion beams• Negative ion sources• Ion sources for fusion• Radioactive ion sources, charge breeders and polarized beams• Beam formation, extraction, transport, and diagnostics• Applications of ion sources• Key technologies for ion sourcesDue to restrictions on traveling and meeting sizes caused by health regulations during the COVID-19 pandemic, the conference was held as a virtual conference. Talks have been presented via ZOOM and two poster sessions were held within the remote meeting platform “Gather town”, which was also open for discussions among participants outside the plenary sessions.The main session on electron beam ion sources was dedicated to the memory of Professor Dr. Evgeny Denisovich Donets who, to our great regret, passed away in June 2021. Professor Donets was the inventor of the electron beam ion source and one of the initiators of this conference series. He was a longtime member of the international advisory committee. His memory will be highly regarded within the ion source community.List of International advisory committee, Scientific program committee, Local organizing committee are available in this pdf.

Space Charge Compensation Study of High Intensity Ion Beams

The space charge effect is one of the key factors affecting ion beam transport and ion beam quality, especially for low-energy high-intensity ion beams. It can be partially compensated by the secondary electrons produced from the ionization of residual gas molecules in the beam pipe, and we are interested in the accurate value of this compensation degree. In this paper, we use a Three-grid Energy Analyzer (TEA) to measure the secondary ion energy distribution of the beam, which corresponds to the compensated beam potential distribution. To have accurate evaluation of the compensation degree, it is essential to adopt a proper transverse distribution of the ion beam, other than using the Gaussian theorem for uniform beams. The results of a space charge compensation degree study for singly charged ion beams with a 2.45GHz microwave ion source and for multiply charged ion beams with a high charge state ECR ion source are presented.

Status and prospects of the 60 GHz SEISM ion source

SEISM is a unique ECR ion source operating at a frequency of 60 GHz. The prototype is based on a simple magnetic geometry, the cusp, allowing the use of polyhelix coils (developed with LNCMI, Grenoble) to generate the closed ECR surface at 2.14T. The plasma is sustained by a high intensity HF pulse (up to 300kW). Previous experiments at LNCMI have successfully demonstrated the establishment of the nominal magnetic field and the extraction of ion beams with a current density up to 1 A cm-2. The presence of afterglow peaks was also observed, proving the existence of ion confinement in a CUSP ECR source. An experimental campaign is carried out in 2021 using a new transport line designed to improve the transmission of the beam to the new detectors. Short and long-term research plans are presented to transform this high current density into a high intensity ion beam that can be used for accelerators of the future.

Diagnostics for multiple frequency heating and investigation of underlying processes.

The development of new facilities routinely challenges ion source designers to build and operate sources that can achieve ever higher beam intensities and energies. Electron cyclotron resonance ion sources have proven to be extremely capable in meeting these challenges through the production of intense beams of medium and high-charge state ions. As performance boundaries are pushed, source stability becomes an issue as does the technology required to meet the challenge. Multiple frequency heating, the simultaneous use of two or more plasma heating frequencies, is a powerful tool in meeting the simultaneous need of intensity and stability. Relatively straightforward to utilize, the technique has been employed at numerous facilities to increase beam current and achievable charge state while also stabilizing the plasma. Its application has expanded the operational boundaries of existing and next generation sources, demonstrating that these devices have not yet achieved their full operational potential. To better understand the underlying physics, the diagnostics used to probe the source operational boundaries and the plasma properties have become increasingly sophisticated. In concert with detailed modeling, they are beginning to provide insight into the heating mechanism and, with that, the prospect of future advances.

Completion of JT-60SA construction and contribution to ITER

Construction of the JT-60SA tokamak was completed on schedule in March 2020. Manufacture and assembly of all the main tokamak components satisfied technical requirements, including dimensional accuracy and functional performances. Development of the plasma heating systems and diagnostics have also progressed, including the demonstration of the favourable electron cyclotron range of frequency (ECRF) transmission at multiple frequencies and the achievement of long sustainment of a high-energy intense negative ion beam. Development of all the tokamak operation control systems has been completed, together with an improved plasma equilibrium control scheme suitable for superconducting tokamaks including ITER. For preparation of the tokamak operation, plasma discharge scenarios have been established using this advanced equilibrium controller. Individual commissioning of the cryogenic system and the power supply system confirmed that these systems satisfy design requirements including operational schemes contributing directly to ITER, such as active control of heat load fluctuation of the cryoplant, which is essential for dynamic operation in superconducting tokamaks. The integrated commissioning (IC) is started by vacuum pumping of the vacuum vessel and cryostat, and then moved to cool-down of the tokamak and coil excitation tests. Transition to the super-conducting state was confirmed for all the TF, EF and CS coils. The TF coil current successfully reached 25.7 kA, which is the nominal operating current of the TF coil. For this nominal toroidal field of 2.25 T, ECRF was applied and an ECRF plasma was created. The IC was, however, suspended by an incident of over current of one of the superconducting equilibrium field coil and He leakage caused by insufficient voltage holding capability at a terminal joint of the coil. The unique importance of JT-60SA for H-mode and high-β steady-state plasma research has been confirmed using advanced integrated modellings. These experiences of assembly, IC and plasma operation of JT-60SA contribute to ITER risk mitigation and efficient implementation of ITER operation.

Effect of MeV ion induced heating on secondary electron emission from Si surface and estimation of local temperature

We report the variation of secondary-electron yield and target temperature with the variation of ion beam intensity during 100 MeV N+5 bombardment on Si surfaces. Theoretical understanding of secondary-electron emission during ion bombardment predicts no variation of yield with ion beam intensity. We discovered that the variation of secondary-electron yield arises due to the rise of local temperature at ion impact sites of the target. The secondary-electron yield first decreases with the increase of ion beam current but subsequently, it increases with the further rise of beam current. The initial decrease is due to the temperature-dependent change of electrochemical potential of Si. The considerable increase of the secondary-electron yield with a further increase of ion beam current is caused by local surface heating and subsequent additional thermionic electron emission. We have estimated the surface temperature of ion-impact sites by separating the thermionic electron current from the collisional secondary electron current.