ISOLDE Research Articles

New developments of 11C post-accelerated beams for hadron therapy and imaging

Hadron therapy was first proposed in 1946 and is by now widespread throughout the world, as witnessed with the design and construction of the CNAO, HIT, PROSCAN and MedAustron treatment centres, among others. The clinical interest in hadron therapy lies in the fact that it delivers precision treatment of tumours, exploiting the characteristic shape (the Bragg peak) of the energy deposition in the tissues for charged hadrons. In particular, carbon ion therapy is found to be biologically more effective, with respect to protons, on certain types of tumours. Following an approach tested at NIRS in Japan [1], carbon ion therapy treatments based on 12C could be combined or fully replaced with 11C PET radioactive ions post-accelerated to the same energy. This approach allows providing a beam for treatment and, at the same time, to collect information on the 3D distributions of the implanted ions by PET imaging. The production of 11C ion beams can be performed using two methods. A first one is based on the production using compact PET cyclotrons with 10–20MeV protons via 14N(p,α)11C reactions following an approach developed at the Lawrence Berkeley National Laboratory [2]. A second route exploits spallation reactions 19F(p,X)11C and 23Na(p,X)11C on a molten fluoride salt target using the ISOL (isotope separation on-line) technique [3]. This approach can be seriously envisaged at CERN-ISOLDE following recent progresses made on 11C+ production [4] and proven post-acceleration of pure 10C3/6+ beams in the REX-ISOLDE linac [5]. Part of the required components is operational in radioactive ion beam facilities or commercial medical PET cyclotrons. The driver could be a 70MeV, 1.2mA proton commercial cyclotron, which would lead to 8.1×10711C6+ per spill. This intensity is appropriate using 11C ions alone for both imaging and treatment. Here we report on the ongoing feasibility studies of such approach, using the Monte Carlo particle transport code FLUKA [6,7] to simulate pristine Bragg Peaks of 11C, in order to compare its performance with 12C, in the context of hadron therapy.

Target materials for exotic ISOL beams

The demand for intensity, purity, reliability and availability of short-lived isotopes far from stability is steadily high, and considerably exceeding the supply. In many cases the ISOL (Isotope Separation On-Line) method can provide beams of high intensity and purity. Limitations in terms of accessible chemical species and minimum half-life are driven mainly by chemical reactions and physical processes inside of the thick target. A wide range of materials are in use, ranging from thin metallic foils and liquids to refractory ceramics, while poly-phasic mixed uranium carbides have become the reference target material for most ISOL facilities world-wide. Target material research and development is often complex and especially important post-irradiation analyses are hindered by the high intrinsic radiotoxicity of these materials. However, recent achievements have proven that these investigations are possible if the effort of different facilities is combined, leading to the development of new material matrices that can supply new beams of unprecedented intensity and beam current stability.

A combined experimental and numerical approach for the control and monitoring of the SPES target during operation at high temperature

The SPES project at INFN-LNL aims at the production of neutron-rich Radioactive Ion Beams (RIBs) using the ISOL (Isotope Separation On Line) technique. A 40MeV 200μA proton beam will directly impinge a uranium carbide target, generating approximately 1013 fissions per second. The target system is installed under vacuum inside a water-cooled chamber, and have to maintain high working temperatures, close to 2000°C. During operation the proton beam provides the heating power required to keep the target at the desired temperature level. As a consequence, its characteristics have to be strictly controlled in order to avoid undesired overheating. According to the original design of the control system, the proton beam can be suddenly interrupted in case of out of range vacuum or cooling water flow levels. With the aim to improve the reliability of the control system a set of temperature sensors has been installed close to the target. Their types and installation positions were defined taking into consideration the detailed information coming from a dedicated thermal–electric model that allowed to investigate the most critical and inaccessible target hot-spots.This work is focused on the definition and experimental validation of the aforementioned numerical model. Its results were used to appropriately install two type C thermocouples, a PT100 thermo-resistance and a residual primary beam current detector. In addition the numerical model will be used for the definition of appropriate thresholds for each installed temperature sensor, since it allows to define a relationship between the locally measured values with the overall calculated temperature field. In case of over temperatures the monitoring system will send warning signals or in case interrupt the proton beam.

Progress in the design and construction of SPES at INFN-LNL

INFN-LNL is constructing an ISOL (Isotope Separation On Line) facility delivering neutron rich ion beams at 10AMeV or beyond, making use of the linear accelerator ALPI as the secondary accelerator. The facility includes a direct ISOL target based on UCx and able to reach 1013fissions/s. In parallel, an applied physics facility will be developed, with applications in medicine and neutron production. The SPES project is a national facility, approved and funded. Commissioning with the first exotic species is expected in 2019. The primary accelerator is a commercial cyclotron, which will send a 40MeV, 200μA proton beam onto an UCx target, connected to SIS, PIS and LIS ion sources. The extracted beam is purified through a Low Resolution Mass Separator (LMRS, i.e. a Wien filter and a dispersive dipole), a beam cooler and a High Resolution Mass Separator (HRMS) and sent to an ECR charge breeder to boost the exotic beam charge state. The highly charged exotic beam is further separated in a MRMS (Medium Resolution Mass Separator) and injected into a 100% duty cycle RFQ and into the existing superconducting linac ALPI, which will be refurbished and upgraded to be an efficient exotic beam accelerator. The upgrade of ALPI will give ∼10AMeV energy to 132Sn19+, taken as the reference ion beam. The paper presents the status of the design and construction of the SPES facility.

Developments towards in-gas-jet laser spectroscopy studies of actinium isotopes at LISOL

To study exotic nuclides at the borders of stability with laser ionization and spectroscopy techniques, highest efficiencies in combination with a high spectral resolution are required. These usually opposing requirements are reconciled by applying the in-gas-laser ionization and spectroscopy (IGLIS) technique in the supersonic gas jet produced by a de Laval nozzle installed at the exit of the stopping gas cell. Carrying out laser ionization in the low-temperature and low density supersonic gas jet eliminates pressure broadening, which will significantly improve the spectral resolution. This article presents the required modifications at the Leuven Isotope Separator On-Line (LISOL) facility that are needed for the first on-line studies of in-gas-jet laser spectroscopy. Different geometries for the gas outlet and extraction ion guides have been tested for their performance regarding the acceptance of laser ionized species as well as for their differential pumping capacities. The specifications and performance of the temporarily installed high repetition rate laser system, including a narrow bandwidth injection-locked Ti:sapphire laser, are discussed and first preliminary results on neutron-deficient actinium isotopes are presented indicating the high capability of this novel technique.

The commissioning of the BRISOL facility

The Beijing Radioactive ion beam facility Isotope Separator On-Line (BRISOL) is a radioactive ion beam facility based on a 100MeV cyclotron providing 100μA proton beam bombarding a thick target to produce radioactive nuclei, which are transferred into an ion source to produce a singly-charged ion beam. The construction and installation of BRISOL was completed in March 2014. The commissioning of the BRISOL facility with stable beams has been carried out in the last year. The ion source, the separator and the beam-line were tested with a 39K+ stable beam. The tests and the current status of the BRISOL facility will be presented in this paper.

α-decay study of Tl

α-decay spectroscopy of Tl has been performed at the CERN isotope separator on-line (ISOLDE) facility. New fine-structure α decays have been observed for both isotopes. α-decay branching ratios of 0.089(19)%, 0.047(6)% and 1.22(30)% have been deduced for the (10−), (7+) and (2−) states respectively in 184Tl and a lower limit of 0.49% for the α-decay branching ratio of 182Tl. A new half-life of 9.5(2) s for the (2−) state in 184Tl and 1.9(1) s for the low-spin state in 182Tl has been deduced. Using α–γ coincidence analysis, multiple γ rays were observed de-exciting levels in Au fed by Tl α decays. The γ transitions connecting these low-lying states in Au are essential to sort the data and possibly identify bands from in-beam studies in these isotopes. Owing to the complex fine-structure α decays and limited knowledge about the structure of the daughter nuclei, only partial level schemes could be constructed for both gold isotopes in the present work. Reduced α-decay widths have been calculated and are compared with values obtained in neighboring odd-A and even-A thallium isotopes. Except for the allowed α decay of the 184Tl (10−) state, the other fine-structure α decays observed in this study are hindered. This points to strong structural changes between parent thallium and daughter gold isotopes.

Recent great impact by an Isotope Separator On-Line (ISOL) in nuclear and radiochemistry.

On April 9 2015, the Letter article titled "Measurement of the first ionization potential of lawrencium, element 103" is now published at News and Views on Nature (2015) which has been performed by our remarkably Japanese colleagues of nuclear and radiochemistry at JAEA (Japan Atomic Energy Agency). In this review, the author will state that the isotope separator on-line (ISOL) our regularly used, one of mass separation techniques, with a thermal surface ionization makes possible for determining the ionization potential of lawrencium based on the fruitful fundations of developing the ISOL system until now and also ever studying searches for unknown nuclei and these nuclear decay properties around actinide region in the past 20 years.

Fission yield measurements at IGISOL

The fission product yields are an important characteristic of the fission process. In fundamental physics, knowledge of the yield distributions is needed to better understand the fission process. For nuclear energy applications good knowledge of neutroninduced fission-product yields is important for the safe and efficient operation of nuclear power plants. With the Ion Guide Isotope Separator On-Line (IGISOL) technique, products of nuclear reactions are stopped in a buffer gas and then extracted and separated by mass. Thanks to the high resolving power of the JYFLTRAP Penning trap, at University of Jyvaskyla, fission products can be isobarically separated, making it possible to measure relative independent fission yields. In some cases it is even possible to resolve isomeric states from the ground state, permitting measurements of isomeric yield ratios. So far the reactions U(p,f) and Th(p,f) have been studied using the IGISOL-JYFLTRAP facility. Recently, a neutron converter target has been developed utilizing the Be(p,xn) reaction. We here present the IGISOL-technique for fission yield measurements and some of the results from the measurements on proton induced fission. We also present the development of the neutron converter target, the characterization of the neutron field and the first tests with neutron-induced fission.

A resonant ionization laser ion source at ORNL

Multi-step resonance laser ionization has become an essential tool for the production of isobarically pure radioactive ion beams at the isotope separator on-line (ISOL) facilities around the world. A resonant ionization laser ion source (RILIS) has been developed for the former Holifield Radioactive Ion Beam Facility (HRIBF) of Oak Ridge National Laboratory. The RILIS employs a hot-cavity ion source and a laser system featuring three grating-tuned and individually pumped Ti:Sapphire lasers, especially designed for stable and simple operation. The RILIS has been installed at the second ISOL production platform of former HRIBF and has successfully provided beams of exotic neutron-rich Ga isotopes for beta decay studies. This paper reports the features, advantages, limitations, and on-line and off-line performance of the RILIS.

New lifetime measurements inPd109and the onset of deformation atN=60

Several new subnanosecond lifetimes were measured in Pd-109 using the fast-timing beta gamma gamma (t) method. Fission fragments of the A = 109 mass chain were produced by bombarding natural uranium with 30 MeV protons at the Jyvaskyla Ion Guide Isotope Separator On-Line (IGISOL) facility. Lifetimes were obtained for excited states in Pd-109 populated following beta decay of Rh-109. The new lifetimes provide some insight into the evolution of nuclear structure in this mass region. In particular, the distinct structure of the two low-lying 7/2(+) states occurring systematically across the Pd isotopic chain is supported by the new lifetime measurements. The available nuclear data indicate a sudden increase in deformation at N = 60 which is related to the strong p-n interaction between pi g(9/2) and vg(7/2) valence nucleons expected in this region.

Prototyping of beam position monitor for medium energy beam transport section of RAON heavy ion accelerator

A heavy ion accelerator, RAON is going to be built by Rare Isotope Science Project in Korea. Its target is to accelerate various stable ions such as uranium, proton, and xenon from electron cyclotron resonance ion source and some rare isotopes from isotope separation on-line. The beam shaping, charge selection, and modulation should be applied to the ions from these ion sources because RAON adopts a superconducting linear accelerator structure for beam acceleration. For such treatment, low energy beam transport, radio frequency quadrupole, and medium energy beam transport (MEBT) will be installed in injector part of RAON accelerator. Recently, development of a prototype of stripline beam position monitor (BPM) to measure the position of ion beams in MEBT section is under way. In this presentation, design of stripline, electromagnetic (EM) simulation results, and RF measurement test results obtained from the prototyped BPM will be described.

RFQ design for the RAON accelerator’s ISOL system

The heavy-ion accelerator RAON has the advantage of having both an in-flight (IF) and an isotope separator on-line (ISOL) system. Two radio frequency quadrupoles (RFQs) will be installed in the RAON: the main linear accelerator (LINAC) RFQ will be used to accelerate the two-charge state 238U for the IF system, while the post-accelerator RFQ will be used to accelerate low-current isotope beams from the ISOL system. In this paper, the post-accelerator RFQ design for the ISOL system is reported. A beam current of 1 pμA was used, and the input beam and the output beam energies were 5 keV/u and 400 keV/u, respectively. Moreover, the design was optimized by reducing the total length and power, adjusting the beam quality. To quantify the influence of thermal expansion on the frequency, we calculated the frequency difference according to deference between the vane’s tip and the body’s diameter.

The RIB production target for the SPES project

Facilities making use of the Isotope Separator On-Line (ISOL) method for the production of Radioactive Ion Beams (RIB) attract interest because they can be used for nuclear structure and reaction studies, astrophysics research and interdisciplinary applications. The ISOL technique is based on the fast release of the nuclear reaction products from the chosen target material together with their ionization into short-lived nuclei beams. Within this context, the SPES (Selective Production of Exotic Species) facility is now under construction in Italy at INFN-LNL (Istituto Nazionale di Fisica Nucleare — Laboratori Nazionali di Legnaro). The SPES facility will produce RIBs mainly from n-rich isotopes obtained by a 40 MeV cyclotron proton beam (200 μA) directly impinging on a uranium carbide multi-foil fission target. The aim of this work is to describe and update, from a comprehensive point of view, the most important results obtained by the analysis of the on-line behavior of the SPES production target assembly. In particular an improved target configuration has been studied by comparing different codes and physics models: the thermal analyses and the isotope production are re-evaluated. Then some consequent radioprotection aspects, which are essential for the installation and operation of the facility, are presented.

Production of exoctic fragments by photofission process combined with stopping gas cell at ELI-NP facility

Extreme Light Infrastructure Nuclear Physics (ELI-NP) facility is being built at Bucharest-Magurele, which then allow us to do research about nuclear physics using a new set of research tools: high power laser system and high brilliance gamma beams. One of day-one experiment proposed at this facility is to study the photofission of actinide by the high-intensity gamma beam through measurement of mass and beta decay. In addition, ternary fission will be also studied. In particular, the measurements of exotic neutron-rich nuclei produced by photofission, especially isotopes of refractory elements, is of great interest and requires the development of an IGISOL-type (Ion guide isotope separation online). In this report, we will present benchmark simulation of photofission rate and rates of related background processes.

Lattice design and beam dynamics studies of the high energy beam transport line in the RAON heavy ion accelerator

In RAON heavy ion accelerator, beams generated by superconducting electron cyclotron resonance ion source (ECR-IS) or Isotope Separation On-Line (ISOL) system are accelerated by lower energy superconducting linac and high energy superconducting linac. The accelerated beams are used in the high energy experimental hall which includes bio-medical and muon-SR facilities, after passing through the high energy beam transport lines. At the targets of those two facilities, the stable and small beams meeting the requirements rigorously are required in the transverse plane. Therefore the beams must be safely sent to the targets and simultaneously satisfy the two requirements, the achromatic condition and the mid-plane symmetric condition, of the targets. For this reason, the lattice design of the high energy beam transport lines in which the long deflecting sections are included is considered as a significant issue in the RAON accelerator. In this paper, we will describe the calculated beam optics satisfying the conditions and present the result of particle tracking simulations with the designed lattice of the high energy beam transport lines in the RAON accelerator. Also, the orbit distortion caused by the machine imperfections and the orbit correction with correctors will be discussed.

Thermal conductivity and emissivity measurements of uranium carbides

Thermal conductivity and emissivity measurements on different types of uranium carbide are presented, in the context of the ActiLab Work Package in ENSAR, a project within the 7th Framework Program of the European Commission. Two specific techniques were used to carry out the measurements, both taking place in a laboratory dedicated to the research and development of materials for the SPES (Selective Production of Exotic Species) target. In the case of thermal conductivity, estimation of the dependence of this property on temperature was obtained using the inverse parameter estimation method, taking as a reference temperature and emissivity measurements. Emissivity at different temperatures was obtained for several types of uranium carbide using a dual frequency infrared pyrometer. Differences between the analyzed materials are discussed according to their compositional and microstructural properties. The obtainment of this type of information can help to carefully design materials to be capable of working under extreme conditions in next-generation ISOL (Isotope Separation On-Line) facilities for the generation of radioactive ion beams.

Internal decay of the(10−)intruder state inTl184

Decay spectroscopy of $^{184}\mathrm{Tl}$ has been performed at the CERN Isotope Separator On-Line (ISOLDE) facility. An excitation energy of 506.1(1) keV and a half-life of 47.1(7) ms of the intruder based $({10}^{\ensuremath{-}})$ state have been extracted. The internal decay characteristics of this state are determined and discussed, extending the systematics of such states in the even-mass thallium nuclei below neutron midshell at $N=104$. The retardation factors of the isomeric $M2$ and $E3$ transitions are deduced and compared with retardation factors in neighboring odd-mass and even-mass thallium isotopes. The new information is combined with a review of hindered and unhindered $\ensuremath{\alpha}$-decay data of $^{187--192}\mathrm{Bi}$ populating levels in daughter nuclei $^{183--188}\mathrm{Tl}$ and supports the interpretation of the intruder character of the $({10}^{\ensuremath{-}})$ state in $^{184}\mathrm{Tl}$.

Beijing radioactive ion facility and basic nuclear physics research prospects

Both radioactive nuclear beam physics and nuclear astrophysics are the frontiers in basic research of physics, which promote the development of radioactive nuclear beam facilities. Here we briefly introduce radioactive nuclear beam physics and nuclear astrophysics, and compare the isotope separation on line (ISOL) and projectile fragmentation (PF) methods to produce radioactive nuclear beams. In addition, we review the pre-existing ISOL-type facilities and introduce Beijing radioactive ion facility (BRIF) and its perspective in basic research of nuclear physics.

Design of post linac to driver linac transport beam line in rare isotope accelerator.

We investigated the design of a beam transport line connecting the post linac to the driver linac (P2DT) in the Rare Isotope Accelerator (RAON). P2DT beam line is designed by 180° bending scheme to send the radioactive isotope separation on-line (ISOL) beams accelerated in the Linac-3 to Linac-2. The beam line is designed as a 180° bend for the transport of a multi-charge state (132)Sn(+45,+46,+47) beam. We used the TRACE 3-D, TRACK, and ORBIT codes to design the optics system, which also includes two bunchers and ten sextupole magnets for chromaticity compensation. The transverse emittance growth is minimized by adopting mirror symmetric optics and by correcting second-order aberrations using sextupoles. We report on the multi-charge state beam transport performance of the designed beam line. The main characteristics of the P2DT line are to minimize beam loss and the growth of emittance, and for charge stripping. Beam optics for P2DT is optimized for reducing beam loss and charge stripping. As Linac-3 may accelerate the stable beam and radioactive beam simultaneously, P2DT line also transports the stable beam and radioactive beam simultaneously. Thus, we need a RF switchyard to send the stable beam to the ISOL target and the radioactive beam to the high-energy experimental area in Linac-2 end.