High-intensity Ion Beam Research Articles

Modeling of carbon penetration into silicon structure under the action of pulsed high-intensity ion beam

Abstract The action of high-intensity beam of carbon ions on a silicon sample is studied by means of a numerical modelling revealing formation of the in-depth carbon concentration profile in crystal lattice of silicon. We investigated three ways of the profile forming: short-pulsed ion implantation, recoil atoms mechanism and thermal diffusion of the carbon atoms adsorbed on the silicon surface. The latter is the result of high temperature gradient associated with the action of pulsed high-intensity ion beam. It is argued that the diffusion process plays the major role in forming of the concentration profile in the pre-surface layer of a silicon sample.

Preliminary Measurement of Space Charge Neutralization Level for Proton Beam

For high-intensity low-energy ion beams, space charge effect is a main cause of beam divergence and emittance growth. Fortunately, residual gas molecules in the drift space tend to be ionized and neutralize the beam space charge spontaneously. The level of Space Charge Neutralization (SCN) is measured through the detection of created secondary ion energy distribution in the beam region. A so-called non-interceptive Three-grid Energy Analyzer (TEA) has been designed and manufactured at Institute of Modern Physics, Chinese Academy of Sciences (IMP). This paper will present the details of the TEA detector and the application to diagnose proton beam SCN level in the Low Energy Beam Transport (LEBT) line. As a preliminary result, for an 18.5 mA proton beam a best compensating point appears at the vacuum pressure of 1.510*3 Pa. And the neutralization level is advanced with the growth of beam current in a constant vacuum pressure.

Carbon saturation of silicon target under the action of pulsed high-intensity ion beam

The action of the pulsed high-intensity ion (carbon) beam on the silicon target is investigated by means of the theoretical model. The forming of the carbon concentration profile in depth of the silicon sample is modelled. It is argued, that there are two ways of the profile forming: short-pulsed ion (carbon) implantation and diffusion of the carbon atoms adsorbed on the silicon surface. It is shown, that the carbon atoms adsorbed on the silicon surface and diffused into the silicon target play the main role in the concentration profile forming.

Influence of high intensity ion beam irradiation on impact toughness of 12Cr1MoV steel

The impact toughness of non-treated and irradiated 12Cr1MoV steel Charpy specimens has been studied in the range of temperatures from 20 C to 600 C. It was revealed that the ion beam treatment of steel deteriorates the impact toughness by 5–40 % at the tested temperature range. The physical regularities of irradiation effect on microhardness and hardness of the treated surface were investigated. It was also found out that irradiated specimens fracture via more brittle mechanism, which is related to both more severe stress–strain state at the notch tip and gradient alteration of properties in the subsurface layer.

Injection and stability of high-intensity ion beams in synchrotrons with electron cooling

The electron cooling-stacking injection is one of the most widely used injection methods applied in forming high-intensity cooled ion beams in the synchrotrons. The maximum available ion intensity in the synchrotron is determined by the lifetime of ions and the cooling-stacking efficiency. The formation of cooled high-intensity beams is constrained by instability, leading to a strong reduction in the ion lifetime. The results of experimental investigations and simulations of the cooling-stacking injection and stability of high-intensity cooled ion beams in synchrotrons with electron cooling are discussed.

Phase Composition and Mechanical Properties Modification in Cr/Ti System by Short-Pulsed High Intensity Ion Beams Treatment

In the present the results of research of structure, phase composition and microhardness measurement of the surface layers of the Cr/Ti system treated by short-pulsed high intensity ion beams (HPIB) are presented. It was shown that the HPIB impact on a “coating/substrate” system can serve as an affective way to produce near-surface alloys in the metals. In particular, in the Cr/Ti system the formation of solid solution β-Ti (Cr) as well as titanium carbide TiCx was revealed. The found changes in structure and phase composition of titanium caused by the HPIB impact allow to increase its microhardness in 2 times.

Experimental tests of the modernized VASSILISSA separator (SHELS) with the use of accelerated 50Ti ions

A high intensity ion beam of 50Ti ions was obtained using the ECR ion source on the U400 cyclotron. The experimental tests using accelerated 50Ti ions were performed with a modernized VASSILISSA separator (SHELS). Data has been obtained on the transmission coefficients of recoil nuclei synthesized in complete fusion reactions. Estimates from ion optical calculations performed in the design phase of the project of modernizing the separator are completely confirmed.

Design of the RAON accelerator systems

The RAON is the name of the heavy ion accelerator facility under construction in Korea that includes the In-flight Fragment (IF) and Isotope Separation On-Line (ISOL) facilities to support cutting-edge research in various science fields. The superconducting linac is the driver for the IF facility that can accelerate beams from proton to uranium with 200 MeV/u, 400 kW (for uranium beam). A 70-MeV, 1-mA H− cyclotron is the driver for the ISOL facility and is followed by a post-accelerator consisting of s superconducting linac that can accelerate rare-isotope (RI) beams and deliver them to experimental halls. These facilities provide high-intensity stable ion and rare isotope (RI) beams for domestic and international users. In this paper, design and prototyping efforts for the RAON accelerator systems are presented.

Design of a neutrino source based on beta beams

“Beta beams” produce collimated pure electron (anti)neutrino beams by accelerating beta active ions to high energies and having them decay in a racetrack shaped storage ring of 7 km circumference, the decay ring. EUROnu beta beams are based on CERN infrastructures and existing machines. Using existing machines may be an advantage for the cost evaluation, but will also constrain the physics performance. The isotope pair of choice for the beta beam is He6 and Ne18. However, before the EUROnu studies one of the required isotopes, Ne18, could not be produced in rates that satisfy the needs for physics of the beta beam. Therefore, studies of alternative beta emitters, Li8 and B8, with properties interesting for a beta beam have been proposed and have been studied within EUROnu. These alternative isotopes could be produced by using a small storage ring, in which the beam traverses a target, creating the Li8 and B8 isotopes. This production ring, the injection linac and the target system have been evaluated. Measurements of the cross section of the reactions to produce the beta beam isotopes show interesting results. A device to collect the produced isotopes from the target has been developed and tested. However, the yields of Li8 and B8, using the production ring for production of Li8 and B8, is not yet, according to simulations, giving the rates of isotopes that would be needed. Therefore, a new method of producing the Ne18 isotope has been developed and tested giving good production rates. A 60 GHz ECRIS prototype, the first in the world, was developed and tested for ion production with contributions from EUROnu. The decay ring lattices for the Li8 and B8 have been developed and the lattice for He6 and Ne18 has been optimized to ensure the high intensity ion beam stability.43 MoreReceived 15 April 2014DOI:https://doi.org/10.1103/PhysRevSTAB.17.071002This article is available under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.Published by the American Physical Society

Formation of nanoscale carbon structures in the surface layer of metals under the impact of high intensity ion beam

This work represents the results of phase composition and the mechanical properties of tungsten and titanium after high-intensity pulsed ion beam (HPIB) treatment. It was shown that nanoscale carbide particles are formed under the HPIB influence in the surface layers of metals. Raising the pulse number results in increase of volume fraction of the carbide phases. The microhardness is 1.5–2 times more than the initial value and wear resistance of the metals improves in response to alloying of tungsten and titanium with carbon atoms accompanied by the formation of carbides.

A new compact structure for a high intensity low-energy heavy-ion accelerator

A new compact accelerating structure named Hybrid RFQ is proposed to accelerate a high-intensity low-energy heavy ion beam in HISCL (High Intensive heavy ion SuperConducting Linear accelerator), which is an injector of HIAF (Heavy Ion Advanced Research Facility). It is combined by an alternative series of acceleration gaps and RFQ sections. The proposed structure has a high accelerating ability compared with a conventional RFQ and is more compact than traditional DTLs. A Hybrid RFQ is designed to accelerate 238U34+ from 0.38 MeV/u to 1.33 MeV/u. The operation frequency is described to be 81.25 MHz at CW (continuous wave) mode. The design beam current is 1.0 mA. The results of beam dynamics and RF simulation of the Hybrid RFQ show that the structure has a good performance at the energy range for ion acceleration. The emittance growth is less than 5% in both directions and the RF power is less than 150 kW. In this paper, the results of beam dynamics and RF simulation of the Hybrid RFQ are presented.

Development of the ion source for cluster implantation

Bernas ion source development to meet needs of 100s of electron-volt ion implanters for shallow junction production is in progress in Institute for Theoretical and Experimental Physics. The ion sources provides high intensity ion beam of boron clusters under self-cleaning operation mode. The last progress with ion source operation is presented. The mechanism of self-cleaning procedure is described.

Sputtering angle effects by Kr mixing in N+ ion beam on the lifetime of nitrided carbon stripper foils

Nitrided carbon stripper (NCS) foils with high nitrogen content were produced by ion beam sputtering of reactive nitrogen gas. Such foils seem to be very useful as strippers in high-intensity heavy ion accelerators. We have conducted comprehensive research, development, and production of such foils with high reproducibility. Krypton, a heavy noble gas, was mixed with the reaction nitrogen gas (IBSRN) in the ion beam sputtering process to produce stripper foils with short sputtering deposition time and long lifetimes in the high intensity ion beam irradiation. With the (N2 + Kr) mixed gas ions we investigated the influence of different sputtering angles (α) on the lifetime of the NCS-foils in case of poly-graphite material. The lifetime measurement of these foils of 20 ± 5 μg/cm2 was performed with a 3.2 MeV Ne+ ion beam as usual. The foils made at a sputtering angle of 15° showed a maximum of 11.0 and 7.5 C/cm2 average charge density, respectively, which corresponded to about 275 and 187 times the lifetime of the best commercially available foils.

Reduction of isotopically enriched 50Ti-dioxide for the production of high-intensity heavy-ion beam

Titanium-50 (50Ti) is an important and often requested ion beam for nuclear physics’ experiments. While natural titanium of very high purity is available in different forms; enriched material can only be bought as the dioxide or the tetrachloride. These compounds cannot be processed from currently available ion sources with a sufficient beam quality and sufficient beam intensity for a long time. We describe here the process of converting titanium dioxide into the metal, the material analysis of the starting material as well as of the reduced material. Despite varying contamination levels of silicon, chlorine, and tin in the primary materials, we obtained high yields of metallic titanium with different contamination levels. The obtained metallic 50Ti was applied at the accelerator UNILAC for the production of a high intensity ion beam for several month of beam time.

Key elements of space charge compensation on a low energy high intensity beam injector

Space charge effect (SCE) along the beam line will decrease beam quality. Space charge compensation (SCC) with extra gas injection is a high-efficiency method to reduce SCE. In this paper, we will report the experimental results on the beam profile, potential distribution, beam emittance, and beam transmission efficiency of a 35 keV∕90 mA H(+) beam and a 40 keV∕10 mA He(+) beam compensated by Ar∕Kr. The influence of gas type, gas flow, and injection location will be discussed. Emphasis is laid on the consideration of SCC when designing and commissioning a high intensity ion beam injector. Based on measured data, a new definition of space charge compensation degree is proposed.

K-130 Cyclotron vacuum system

The vacuum system for K-130 cyclotron has been operational since 1977. It consists of two sub-systems, main vacuum system and beam line vacuum system. The main vacuum system is designed to achieve and maintain vacuum of about 1 × 10−6 mbar inside the 23 m3 volume of acceleration chamber comprising the Resonator tank and the Dee tank. The beam line vacuum system is required for transporting the extracted beam with minimum loss. These vacuum systems consist of diffusion pumps backed by mechanical pumps like roots and rotary pumps. The large vacuum pumps and valves of the cyclotron vacuum system were operational for more than twenty five years. In recent times, problems of frequent failures and maintenance were occurring due to aging and lack of appropriate spares. Hence, modernisation of the vacuum systems was taken up in order to ensure a stable high voltage for radio frequency system and the extraction system. This is required for efficient acceleration and transportation of high intensity ion beam. The vacuum systems have been upgraded by replacing several pumps, valves, gauges and freon units. The relay based control system for main vacuum system has also been replaced by PLC based state of the art control system. The upgraded control system enables inclusion of additional operational logics and safety interlocks into the system. The paper presents the details of the vacuum system and describes the modifications carried out for improving the performance and reliability of the vacuum system.

Intense beams from gases generated by a permanent magnet ECR ion source at PKU

An electron cyclotron resonance (ECR) ion source is designed for the production of high-current ion beams of various gaseous elements. At the Peking University (PKU), the primary study is focused on developing suitable permanent magnet ECR ion sources (PMECRs) for separated function radio frequency quadrupole (SFRFQ) accelerator and for Peking University Neutron Imaging Facility. Recently, other kinds of high-intensity ion beams are required for new acceleration structure demonstration, simulation of fusion reactor material irradiation, aviation bearing modification, and other applications. So we expanded the ion beam category from O(+), H(+), and D(+) to N(+), Ar(+), and He(+). Up to now, about 120 mA of H(+), 83 mA of D(+), 50 mA of O(+), 63 mA of N(+), 70 mA of Ar(+), and 65 mA of He(+) extracted at 50 kV through a φ 6 mm aperture were produced by the PMECRs at PKU. Their rms emittances are less than 0.2 π mm mrad. Tungsten samples were irradiated by H(+) or He(+) beam extracted from this ion source and H∕He holes and bubbles have been observed on the samples. A method to produce a high intensity H∕He mixed beam to study synergistic effect is developed for nuclear material irradiation. To design a He(+) beam injector for coupled radio frequency quadruple and SFRFQ cavity, He(+) beam transmission experiments were carried out on PKU low energy beam transport test bench and the transmission was less than 50%. It indicated that some electrode modifications must be done to decrease the divergence of He(+) beam.

Process dynamics and thermodynamics of charged particle beams which remain equipartitioned

This paper examines the process dynamics and thermodynamics of charged particle beams which remain equipartitioned. Considering a high-intensity ion beam in a space-charge dominated regime and with an initially large mismatched RMS beam size, we observe a fast increasing spatial anisotropy of the beam. Since space-charge interactions in a high-intensity linear accelerator can lead to energy equipartition between the degrees of freedom, this anisotropization phenomena suggest a kind of route to equipartition. In this paper we show that the particle-particle resonances and mode-particle resonances lead to the anisotropization of the beam, that is, both the envelope ratio and the emittance ratio are different from one. We propose that this anisotropy is responsible for the beam’s equipartitioning. The results suggest that the beam remains equipartitioned when it exhibits a macroscopic anisotropy, which is characterized by the following properties: the development of an elliptical shape with increasing size along a direction, the presence of a coupling between transversal emittances, halo formation along a preferential direction, stationarity of the temperature and a growth of the entropy in the cascade form. We call the state characterized by these properties as an anisotropic equipartition state.

Development of the carbon foils as charge strippers for high-intensity uranium ion beams

A carbon foil (C-foil) is commonly used as a charge stripper in the heavy-ion accelerators. Since 2005, the polymer-coated carbon foils (PCC-foils) have been fabricated at Nishina Center to prepare larger and thicker C-foils than those previously used as charge strippers. However, the multi-layer PCC-foils did not have sufficiently long life-time. Since August 2009, a new magnetron sputtering system is used to fabricate a thick C-foil. The foils coated with polymer are used as strippers. Life-times of the new single-layer PCC-foils under the uranium beam were measured in two configurations: at the first one a small piece of C-foil was attached to a fixed holder and in the second one a large C-foil was attached to a “rotating-cylinder stripper” device. The properties of the new single-layer PCC-foils and the results of the life-time measurements are reported in this contribution.

High Energy Density Physics Studies at the Facility for Antiprotons and Ion Research: the HEDgeHOB Collaboration

AbstractThe forthcoming Facility for Antiprotons and Ion Research (FAIR) at Darmstadt, is going to be a unique accelerator facility that will deliver high quality, strongly bunched, well focused, intense beams of heavy ions that will lead to unprecedented specific power deposition in solid matter. This will generate macroscopic samples of High Energy Density (HED) matter with fairly uniform physical conditions. These samples can be used to study the thermophysical and transport properties of HED matter. Extensive theoretical work has been carried out over the past decade to design numerous dedicated experiments to study HED physics at the FAIR, which has provided the basis for the HEDgeHOB (High Energy Density Matter Generated by Heavy Ion Beams) scientific proposal. This work is still in progress as the feasibility studies for more experimental schemes are being carried out.Another, very important research area that will benefit tremendously from the FAIR facility, is the production of radioactive beams. A superconducting fragment separator, Super–FRS is being designed for the production and separation of rare radioactive isotopes. Unlike the HED targets, the Super–FRS production target should not be destroyed or damaged by the beam, but should remain intact during the long experimental campaign. However, the high level of specific power deposited in the production target by the high intensity ion beam at FAIR, could cause serious problems to the target survival. These HED issues related to the Super–FRS production target are also discussed in the present paper (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)