Separated Sector Cyclotron Research Articles

γ-ray emission in proton-induced nuclear reactions on [formula omitted]C and Mylar targets over the incident energy range, Ep = 30 – 200 MeV. Astrophysical implications

We have measured the γ-ray line production cross sections in proton-induced nuclear reactions on various target nuclei (12C, 16O, 24Mg, 28Si, 56Fe) of chemical elements abundant in astrophysical sites (solar flares, the interstellar medium, cosmic compact objects) over the incident energy range of Ep = 30 – 200 MeV. We carried out experimental campaigns in joint collaboration at the K = 200 separated sector cyclotron of iThemba LABS using a high-energy resolution, high-efficiency detection array composed of 8 Compton-suppressed clover detectors comprising 32 HP-Ge crystals for recording the γ-ray energy spectra. In the current paper, we focus on γ-ray de-excitation lines produced in proton irradiations of natC and Mylar targets, in particular, on the prominent 4.439 and 6.129 MeV lines of 12C and 16O which are among the strongest lines emitted in solar flares and in interactions of low-energy cosmic rays (LECRs) with the gas and dust of the inner galaxy. We report new γ-ray production experimental cross section data for ten nuclear γ-ray lines that we compare to previous low-energy data sets from the literature, to the predictions of the TALYS code of nuclear reactions and to a semi-empirical compilation. In the first approach, performing calculations with default input parameters of TALYS we observed substantial deviations between the predicted cross sections and experimental data. Then, using modified optical model potential (OMP) and nuclear level deformation parameters as input data we generated theoretical excitation functions for the above two main lines fully consistent with experimental data. In contrast, the experimental data sets for the other eight analyzed lines from the two proton-irradiated targets exhibit significant deviations with the predicted cross section values. We also report line-shape experimental data for the line complex observed at Eγ = 4.44 MeV in irradiations of the two targets. Finally, we emphasize the astrophysical implications of our results.

Targetry for the in-beam activation of tracer particles for positron emission particle tracking

Positron emission particle tracking measures the trajectory of a single radioactively labelled tracer particle by coincident detection of emitted annihilation photons. The technique enables the non-invasive study of dense opaque flows, with the tracer acting as a small neutrally buoyant flow-follower. The University of Cape Town has established a PEPT facility at iThemba LABS, utilising tracer particles produced through radiochemical methods, and measured using adapted positron tomographs. An activation approach producing the positron emitter 18F inside glass target spheres of diameter between 5.0 and 10 mm using accelerated beams of alpha-particles has been explored. The reaction 16O(O, x)18F is used, exploiting the high concentration of natural oxygen and the correspondingly high cross-sections for 18F formation. A standard target holder for the batch production of radionuclides at iThemba LABS was modified, reducing the entrance window thickness, allowing ingress of circulating cooling water, and adapted for a primary tparticle beam of 100 MeV energy delivered by the separated sector cyclotron (SSC) of iThemba LABS. Two-hour bombardment at nominal beam current 0.8 eµA produced activities up to ~ 110 MBq (3 mCi), with over 95% of the activity being 18F.

Excitation functions of natNi(p, x) reactions in the energy range of 75–100 MeV

Stacked-foil activation technique and high-resolution gamma spectrometry were used to investigate new excitation functions of proton-induced nuclear reactions on natNi targets in the energy range of 75–100 MeV. The stack foils were irradiated with 100 MeV protons at the separated-sector cyclotron of the Institute of Modern Physics, Chinese Academy of Sciences, China. The proton intensity for each nickel foil was determined using the natNi(p, x)57Ni monitor reaction. The cross-sections of the natNi(p, x)56Ni, 55,57,58Co, and 54Mn reactions were calculated and compared with the existing literature data presented in the Experimental Nuclear Reaction Data (EXFOR). Furthermore, evaluated nuclear data of the PADF-2007, ENDF/B-VIII.0, and JENDL-4.0/HE libraries as well as theoretical calculations of the TALYS code were used. Overall, our experimental data agree with the majority of the literature data. The results of TALYS code as well as the ENDF/B-VIII.0 and JENDL-4.0/HE libraries could reproduce most of the experimental trend, whereas the results of PADF-2007 library could not do so. The new experimental results provide cross-sections for proton-induced natNi reactions in the energy range of 75–100 MeV and could serve as a technical assistance for radionuclide production and radiation safety practices.

Excitation function of proton induced reactions on iron in the energy range 85–100 MeV

Excitation functions of the natFe (p, x) 52,54Mn, 55Co, 51Cr, 52Fe, and 46Sc reactions were measured at the proton energy of 87, 94 and 100 MeV, using the stacked foil activation technique followed by the off-line γ-ray spectrometry. The experiment was carried out on the separated sector cyclotron at the Institute of Modern Physics, Chinese Academy of Sciences. The natNi (p, x)57Ni and natAl (p, x)22Na reactions with known cross sections was used to monitor the proton beam intensity. The results from this work were compared with the existing literature data available in EXFOR data library and were found to be in good agreement. TALYS-1.95 is able to reproduce, in most cases, the experimental trend. Our experimental results were also compared with evaluated nuclear data from the ENDF/B-VIII.0, JENDL-4.0/HE, and PADF-2007 libraries as a function of proton energy, which reproduced the trend of the excitation functions of the experimental natFe (p, x) reaction cross-sections. These data expand our knowledge on the related excitation functions to confirm the existing trends and to give additional experimental values on a wider energy range.

High-Current Light-Ion Cyclotron for Applications in Nuclear Security and Radioisotope Production

In this article, we propose the conceptual design, with supporting beam dynamics results, of a normal conducting, separated-sector cyclotron with a strong-focusing field gradient designed to accelerate light ions with a charge-to-mass ratio of 1/2 up to 15-20 MeV/u. The design can support a host of applications for therapy, radiobiology, material science, and instrumentation development. The light-ion species, which can include a mixed ion beam, can be dynamically chosen to provide a range of characteristic signals appropriate for specific material identification such as special nuclear materials. A conservative baseline concept is presented which has been optimized for radioisotope production of alpha emitters and theranostic radiopharmaceuticals. The modular design is also demonstrated to be scalable in gross physical parameters by a factor of 2-3, thereby reducing the size, weight, and power requirements (SWaP) and enabling near-term security applications.

Multi-physics analysis and experiment of a CW four-rod RFQ

The new injector SSC-LINAC is under design and construction to improve the efficiency and intensity of beams for the Separated-Sector Cyclotron (SSC). This will be accomplished with a normal conducting radio-frequency quadrupole (RFQ) accelerator. To match with the SSC, the RFQ must be operated on Continuous Wave (CW) mode with a frequency of 53.667 MHz. A four-rod structure was adopted for small dimensions of the cavity. While, it was a huge challenge on CW mode. A multi-physics theoretical analysis, including RF, thermal, structural and frequency shift coupling analysis, have been completed in response to the safe and stable operation of the RFQ. The experimental measurement of frequency shift has been also completed, which is consistent with the simulation. In this paper, the results of theoretical analysis and experiment are reported in detail.

Experimental study of tritium activity concentration in cooling water of heavy ion research facility in Lanzhou

Cooling water of Heavy Ion Research Facility in Lanzhou is the media of choice for absorbing heat generated by a multitude of accelerator components. During the operation, tritium is produced by the secondary neutrons in the accelerator loop of accelerator cooling water, which is uniformly distributed in the water system in the form of hydrogen tritium oxide. The purpose of this study is to establish a rigorous method to measure the low levels of tritium in the accelerator cooling water system. The cooling water samples of Sector Focusing Cyclotron and Separated Sector Cyclotron of Heavy Ion Research Facility in Lanzhou, as well as the natural levels of tritium, were measured successfully, using Quantulus1220 ultra-low-level background liquid scintillation spectrometer. The electrolytic enrichment method was employed to measure the tritium activity concentrations of the cooling water samples. Moreover, the minimum detectable activity concentration and the counting rate efficiency curve of the liquid scintillation spectrometer were obtained to ensure reliability. In this work, we provide a reference to establish the related standards and specifications for monitoring the tritium levels in heavy-ion accelerator cooling water system.

Study of orbit properties and intense beam dynamics in a high current separated sector proton cyclotron

This paper outlines a simple method based on analytical formulations to find out the physics design of a separated sector cyclotron. Formulations are developed to determine the magnet sector shape and equilibrium orbit properties for a chosen orbital frequency and a peak magnetic field in the magnet sector. Stability analysis of single particle motion without space charge effect has been performed and allowed values of sector angles are determined. The dynamics of space charge dominated beam in the separated sector proton cyclotron are explored by using beam envelope equations that includes radial and longitudinal coupling. Evolution of the rms beam envelopes and emittances has been studied as a function of the beam current for various sector geometry. The envelope equations and perturbed equations of motion around the matched beam envelopes have been utilized to obtain the matched beam conditions at different values of the beam current.

Development of New Target Stations for the South African Isotope Facility

The development of new target stations for radioisotope production based on a dedicated 70 MeV commercial cyclotron (for protons) is described. Currently known as the South African Isotope Facility (SAIF), this initiative will free the existing separated-sector cyclotron (SSC) at iThemba LABS (near Cape Town) to mainly pursue research activities in nuclear physics and radiobiology. It is foreseen that the completed SAIF facility will realize a three-fold increase in radioisotope production capacity compared to the current programme based on the SSC.

The design and implementation of a broadband digital low-level RF control system for the cyclotron accelerators at iThemba LABS

iThemba LABS has successfully designed a new broadband digital low-level RF control system for cyclotrons, that operates over the wide frequency range of 2–100 MHz and can achieve peak–peak amplitude and phase stabilities of 0.01% and 0.01°, respectively.The presented system performs direct digital synthesis (DDS) to directly convert the digital RF signals to analog RF and local-oscillator (LO) signals with 16-bit amplitude accuracy, programmable in steps of 1μHz and 0.0001°. Down-conversion of the RF pick-up signals to an optimal intermediate frequency (IF) of 1 MHz and sampling of the IF channels by 16-bit, single sample-latency 10 MHz ADCs was implemented to allow digital high-speed low-latency in-phase/quadrature (I/Q) demodulation of the IF channels within the FPGA. This in turn allows efficient real-time digital closed-loop control of the amplitude and phase of the RF drive-signal to be achieved.The systems have been successfully integrated at iThemba LABS into the K=8 and K=10 injector cyclotrons (SPC1, and SPC2), the K=200 separated sector cyclotron (SSC), the SSC flat-topping system, the pulse-selector system and the AX,J, and K-line RF bunchers.The systems have led to a substantial improvement in the beam quality of the SSC at iThemba LABS with a reduction in beam losses by more than 90%. The design, implementation and performance is discussed.

Sawtooth-wave prebuncher with dual-gaps in Linac injector for HIRFL-SSC

An RFQ structure is normally composed of radial matcher, shaper, gentle buncher and accelerator section with changing cell geometry. Bunching is started in the shaper, and adiabatic bunching is done in gentle buncher section. The beam preforms from DC beam to bunch beam through the RFQ and the longitudinal emittance for the ions linacs is defined initially in the RFQ, in which the beam bunch has been shaped. In the present SSC-Linac injector, an RFQ has been designed to accelerate the continuous beam from 3.728 keV/u to 143 keV/u. The heavy ions beam is injected into the SSC (Separated Sector Cyclotron) with the kinetic energy of 1.025 MeV/u after four IH DTLs. The rf frequency of the SSC is 13.417 MHz, and the frequency of the heavy ions RFQ is set to four times of the rf frequency of the SSC. In order to increase the longitudinal capture efficiency of the SSC and suppress the longitudinal emittance at the exit of RFQ, an external MHB (Multi-Harmonics Buncher) is proposed in front of the RFQ. The fundamental frequency of the MHB is the same as the rf frequency of the cyclotron. The scheme of dual-gaps prebuncher with the sawtooth waveform is firstly carried out through multi-harmonics synthetic technology. The multi-particle beam dynamic simulations of the MHB have been done by the BEAMPATH code.

Magnetic system of a superconducting separated-sector cyclotron for hadron therapy

The development of a cyclotron magnetic system based on superconducting sector magnets is discussed. The cyclotron is conceived as a booster accelerator of a source of 12С6+ ions with energy of 400MeV/nucleon for the purposes of hadron therapy. The results of preliminary investigations aimed at developing such a facility have been reported in our previous papers. In this paper, we consider various configurations of the booster’s magnetic system for various field levels. We also analyze the effects of the positions and shapes of superconducting coils on the magnetic field and select the optimum configuration for the cyclotron’s magnetic system.

Octupole correlations in N=88Dy154 : Octupole vibration versus stable deformation

We report on low-spin states of $^{154}\mathrm{Dy}$ populated via the reaction $^{155}\mathrm{Gd}$ $(^{3}\mathrm{He},4n)$ with a beam energy of 37.5 MeV from the Separated Sector Cyclotron at iThemba Laboratory. The AFRODITE \ensuremath{\gamma}-ray spectrometer was used to establish new $E1$ transitions between bands of opposite parity. The measurements broaden the $N=88$ systematics on the relationship between the first excited positive-parity pairing isomer band and the lowest-lying negative-parity band as the nuclear quadrupole deformation decreases with increasing proton number. In a region of strong octupole correlations the data suggest that the spectroscopy of $N=88$ nuclei is driven by stable octupole deformations and not by vibrations.

On-line test using multi-foil SiC target at iThemba LABS

In a collaboration between the INFN-SPES project and iThemba LABS, an on-line test of the power dissipation of a multi-slice target concept for radioactive-ion beam production has been performed. Using the 66MeV proton beam from the iThemba LABS Separated Sector Cyclotron, a total power of 4kW was deposited in the target complex, consisting of 13 Silicon Carbide (SiC) discs of about 1 millimetre thickness housed in a graphite cylinder. The results of the measurements fully validate thermal FEM simulations and confirm that the multi-foil target system is a reliable and affordable device for second-generation ISOL-RIB facilities like SPES.

Design, fabrication, and beam commissioning of a continuous-wave four-rod rf quadrupole

A new heavy-ion linac within a continuous-wave (CW) 4-rod radio-frequency quadrupole (RFQ) was designed and constructed as the injector for the separated-sector cyclotron (SSC) at the Heavy Ion Research Facility at Lanzhou (HIRFL). In this paper, we present the development of and the beam commissioning results for the 53.667 MHz CW RFQ. In the beam dynamics design, the transverse phase advance at zero current, σ0⊥, is maintained at a relatively high level compared with the longitudinal phase advance (σ0∥) to avoid parametric resonance. A quasi-equipartitioning design strategy was applied to control the emittance growth and beam loss. The installation error of the electrodes was checked using a FARO 3D measurement arm during the manufacturing procedure. This method represents a new approach to measuring the position shifts of electrodes in a laboratory environment and provides information regarding the manufacturing quality. The experimental results of rf measurements exhibited general agreement with the simulation results obtained using CST code. During on-line beam testing of the RFQ, two kinds of ion beams (Ar408+ and O165+) were transported and accelerated to 142.8 keV/u, respectively. These results demonstrate that the SSC-Linac has made a significant progress. And the design scheme and technology experiences developed in this work can be applied to other future CW RFQs.20 MoreReceived 22 May 2015DOI:https://doi.org/10.1103/PhysRevAccelBeams.19.010402This 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 SocietyPhysics Subject Headings (PhySH)Physical SystemsAccelerator applicationsPulsed-power acceleratorsAccelerators & Beams

Heavy Ions Research Facility in Lanzhou (HIRFL)

Heavy ions accelerator has greatly scientific significance in nuclear physics, atomic physics and astrophysics. It is also of great social needs in many application fields, such as nuclear detection, radiation medicine and medical physics. In addition, Heavy ions accelerator has important application prospects in the interdisciplinary fields of nuclear physics, nuclear technology, radiation biology, material science, biology and agriculture. Therefore, heavy ions accelerator makes great contributions to the promotion of human development and social progress. At present, there are more than 30 large scale heavy ions accelerators. And the main overseas heavy ions accelerators are the BNL-RHIC in the United States, the RIKEN-RIBF in Japan, the MSU-FRIB in the United States, the GANIL-SPIRAL2 in France and the FAIR in Europe which is under construction. In China, however, there are the BRIF in Beijing and the HIRFL in Lanzhou being operation and High Intensity heavy-ion Accelerator Facility (HIAF) which will be built in Huizhou. Heavy Ions Research Facility in Lanzhou (HIRFL), one of the most important research facilities for nuclear physics in the world, is the largest scale heavy-ion accelerator facility with the most ion species and the highest ion energy in China at present. And its main parameters have reached international advanced level. HIRFL is composed of ECR ion source, sector focused cyclotron (SFC), separated sector cyclotron (SSC), radioactive ion beam lines RIBLL1 and RIBLL2, cooler storage rings CSRm and CSRe, and many terminals. HIRFL can accelerate all ion species and provide high quality stable beams and radioactive beams with many ion species and broad energy ranges to carry on the heavy-ion physics and crossing discipline research. This paper is mainly to present the status of HIRFL and its progress, and the development of heavy-ion accelerator facilities at home and abroad are also introduces briefly.

The beam commissioning of a CW high charge state heavy ion RFQ

The SSC-LINAC project is launched at Institute of Modern Physics in China to develop one new linear accelerator (LINAC) injector for separated sector cyclotron (SSC). It includes a high charge state ion source, a CW RFQ and a DTL section, and is designed to accelerate ions up to 580keV/u. Now the ion source and the RFQ cavity have been installed in the main hall and the beam commissioning has been carried out. Two kinds of ions have been tested, 16O5+ and 40Ar8+. The experiment result of 16O5+ is: the measured beam current is 180μA at entrance of RFQ and 150μA at exit of RFQ. The output energy of 16O5+ is 141.89keV/u. The measured beam current is 210μA at entrance of RFQ and 198μA at exit of RFQ for 40Ar8+. The output energy of 40Ar8+ is 142.78keV/u. The experiment results agree with the design parameters of RFQ very well. This paper presents: the design consideration of beam dynamics, RF and cooling structure design; measurement of the cold model; high power test of RFQ and beam commissioning result.

The study of acceptance and the transmission efficiency of separated sector cyclotron

In this paper we present the study of the transversal and longitudinal acceptance and the transmission efficiency in the injection, acceleration, and extraction systems in the separated sector cyclotron of the heavy ion research facility in Lanzhou, China. The study of cyclotron acceptance is done for 238U36+ with energy of 97 MeV/u and for 70Zn10+ with energy of 5.62 MeV/u under the theoretical isochronous and real magnetic field distribution. From the simulation results it can be seen that the transmission efficiency and the acceptances of separated sector cyclotron can be improved by redesign the curvature of MSI3 deflector or by introducing the magnet shim in MSI3 deflector region to change the distribution of the inner magnetic field.

A vertical-beam target station and high-power targetry for the cyclotron production of radionuclides with medium energy protons

A vertical-beam target station (VBTS) is described to exploit the high-intensity proton beams delivered by the upgraded separated-sector cyclotron of iThemba LABS for the production of longer-lived, high value radionuclides such as 22Na, 68Ge and 82Sr. Aspects of the targetry are discussed as well as a beam splitter, which makes it possible to perform radionuclide production bombardments simultaneously in two irradiation vaults. With tandem targets in two stations, four targets can be bombarded simultaneously. The delivery of 66MeV proton beams of higher intensity has been realized by installing fixed frequency, flat-top RF resonators on both the main cyclotron and an injector cyclotron. The increase in beam intensity also required new non-destructive diagnostic components in the relevant high-energy beamlines. An overview is given of the current radionuclide production target stations, their similarities and differences and the role of the VBTS in the production programme.

Beam dynamics simulation of HEBT for the SSC-linac injector

The SSC-linac (a new injector for the Separated Sector Cyclotron) is being designed in the HIRFL (Heavy Ion Research Facility in Lanzhou) system to accelerate 238U34+ from 3.72 keV/u to 1.008 MeV/u. As a part of the SSC-linac injector, the HEBT (high energy beam transport) has been designed by using the TRACE-3D code and simulated by the 3D PIC (particle-in-cell) Track code. The total length of the HEBT is about 12 meters and a beam line of about 6 meters are shared with the exiting beam line of the HIRFL system. The simulation results show that the particles can be delivered efficiently in the HEBT and the particles at the exit of the HEBT well match the acceptance of the SSC for further acceleration. The dispersion is eliminated absolutely in the HEBT. The space-charge effect calculated by the Track code is inconspicuous. According to the simulation, more than 60 percent of the particles from the ion source can be transported into the acceptance of the SSC.