ISAC (accelerator)

ISAC (accelerator). The ISAC (Isotope Separator and Accelerator) facility is a world-leading radioactive ion beam (RIB) facility located at the TRIUMF national laboratory in Vancouver, Canada. It was the first facility of its kind to couple an isotope separator on-line to a high-power proton cyclotron, enabling pioneering research in nuclear physics, nuclear astrophysics, and materials science. Since beginning operations, ISAC has established Canada as a central hub for experiments with rare isotopes, attracting an international community of scientists.

Overview

The ISAC facility is designed to produce, separate, and accelerate short-lived radioactive isotopes for fundamental and applied research. Its core concept involves using a high-intensity proton beam from the TRIUMF 500 MeV cyclotron to create rare isotopes via spallation, fission, or fragmentation reactions in thick production targets. These isotopes are then ionized, mass-separated, and delivered to low-energy experiments or further accelerated by a linear accelerator (linac) complex. This unique capability allows scientists to study the properties of nuclei far from stability, probing the limits of nuclear existence and the processes that create elements in cosmic rays and stellar nucleosynthesis. The facility operates multiple experimental stations concurrently, supporting a diverse program that also includes research in condensed matter physics and radionuclide development for medical imaging.

History and development

The development of ISAC was driven by the late-20th century scientific push to explore the nuclear landscape away from the valley of stability. Conceptual planning at TRIUMF began in the late 1980s, with formal approval and construction of the initial ISAC-I facility occurring between 1995 and 1998. The first radioactive beams were delivered in 1999, marking a significant achievement for the Canadian nuclear physics community. A major expansion, known as ISAC-II, was approved in the early 2000s to add a superconducting linac for higher-energy beams, with its first phase commissioned in 2005. This evolution was supported by key collaborations with institutions like Argonne National Laboratory and funding from the National Research Council and the Canada Foundation for Innovation. The ongoing Advanced Rare IsotopE Laboratory (ARIEL) project at TRIUMF will further augment ISAC's capabilities with additional proton beams.

Technical specifications

The ISAC facility's technical chain begins with a high-power proton beam from the TRIUMF 500 MeV cyclotron, which can deliver up to 100 μA onto a variety of production targets, such as silicon carbide or tantalum. The produced isotopes are extracted and ionized using either a surface ionization source or a versatile laser ionization technique known as TRIUMF's Ion Guide Laser Ion Source (TRILIS). A high-resolution magnetic separator then purifies the beam by mass-to-charge ratio. For acceleration, the ISAC-I linac consists of a Radio Frequency Quadrupole (RFQ) and a Drift Tube Linac (DTL), providing beams up to 1.8 MeV/u. The ISAC-II superconducting linac adds a series of Quarter-Wave Resonator (QWR) and Half-Wave Resonator (HWR) cryomodules, boosting beam energies up to 20 MeV/u for medium-mass ions and over 10 MeV/u for heavier species like uranium.

Scientific research and applications

Research at ISAC spans several frontiers of modern science. In nuclear astrophysics, measurements of reaction rates and nuclear masses for isotopes like carbon-11 and oxygen-15 directly inform models of explosive stellar events such as novae and X-ray bursts. The facility's low-energy beam lines host precise laser spectroscopy experiments, like those using the TITAN (TRIUMF's Ion Trap for Atomic and Nuclear science) setup, to measure nuclear charge radii and moments. The DRAGON (Detector of Recoils And Gammas Of Nuclear reactions) separator has been instrumental in studying radiative proton and alpha capture reactions crucial to stellar nucleosynthesis. Applied research includes the implantation of radioactive probes for studies of semiconductor defects and the development of novel isotopes for positron emission tomography (PET), contributing to advancements in materials engineering and nuclear medicine.

Facility and infrastructure

The ISAC facility is housed within the main TRIUMF complex on the campus of the University of British Columbia. It comprises several interconnected halls and bunkers designed for radiation containment. Key infrastructure includes the target station and primary isotope separator, multiple low-energy experimental beam lines, and the linear accelerator tunnels for ISAC-I and ISAC-II. The facility is supported by specialized laboratories for detector development, a high-performance computing center for data analysis, and a dedicated cryogenics plant for the superconducting accelerators. ISAC operates as a user facility under the guidance of an international program advisory committee, with beam time allocated to researchers from institutions worldwide, including CERN, GSI Helmholtz Centre for Heavy Ion Research, and RIKEN. Category:Particle accelerators Category:Research facilities in Canada Category:Nuclear physics facilities