HILAC

HILAC. The Heavy Ion Linear Accelerator (HILAC) was a pioneering linear particle accelerator constructed at the Lawrence Berkeley National Laboratory (then the University of California Radiation Laboratory) in the late 1950s. It was specifically designed to accelerate heavy ions, such as those of carbon, nitrogen, and oxygen, to energies sufficient for nuclear research, enabling the synthesis of new elements. The machine played a foundational role in the discovery of several transuranium elements and was a direct technological precursor to the SuperHILAC and the Bevalac.

History and development

The concept for the HILAC emerged from the post-war nuclear physics program at the University of California, Berkeley, under the leadership of figures like Edwin McMillan and Albert Ghiorso. Its development was driven by the need to extend the study of nuclear reactions beyond the light ions accessible with existing machines like the cyclotron. Key design work was led by engineers and physicists including Wayne Meinke and Robert Thornton, drawing on principles from earlier accelerators like the Alvarez linear accelerator. Construction began in 1955, and the HILAC achieved its first beam in 1957, becoming operational for research shortly thereafter. Its success was part of a broader accelerator-building era that included projects at institutions like the Argonne National Laboratory and Brookhaven National Laboratory.

Design and operation

The HILAC was a room-temperature, drift-tube linear accelerator operating on the principle of Wideröe-type acceleration. Ions produced in a specialized Ion source at the injector end were accelerated through a series of cylindrical copper drift tubes housed inside a large vacuum tank. A high-frequency radio frequency power source, operating at 70 MHz, created an oscillating electric field in the gaps between the tubes. As the particles gained energy and velocity, the physical lengths of the drift tubes increased progressively to maintain synchronization with the RF field, a design principle also used in the proton linear accelerator. The machine accelerated ions to a final energy of 10.4 MeV per atomic mass unit.

Scientific contributions and discoveries

The HILAC was instrumental in the discovery and synthesis of new chemical elements, cementing Berkeley's reputation in heavy ion physics. In 1958, a team led by Albert Ghiorso, Glenn T. Seaborg, and others used the accelerator to bombard a curium target with carbon ions, resulting in the first identification of element 102, later named nobelium. Subsequent campaigns using targets of californium and berkelium with beams of boron and nitrogen ions led to the discovery of lawrencium in 1961. The HILAC also produced crucial data on nuclear reaction mechanisms, fission barriers, and the properties of exotic nuclei, contributing significantly to the field of nuclear chemistry.

Later evolution and legacy

The original HILAC operated until 1971, when it was decommissioned to serve as the injector for a major upgrade: the SuperHILAC. This new machine, which began operation in 1972, featured an improved design with two parallel accelerator lines and could reach higher energies and intensities. The SuperHILAC itself later became the injector for the Bevalac in 1974, a unique facility that combined the SuperHILAC with the Bevatron synchrotron to create the world's first relativistic heavy-ion collider. This lineage established a continuous heavy-ion research program at Berkeley that paved the way for modern facilities like the Relativistic Heavy Ion Collider at Brookhaven National Laboratory and the research conducted at CERN.

Technical specifications

The HILAC was approximately 68 feet (21 meters) in length. It accelerated ions with a mass-to-charge ratio (A/q) up to 8, covering elements from helium to argon. Its final output energy was 10.4 MeV per atomic mass unit, corresponding to a total energy of about 120 MeV for carbon ions. The machine utilized a radio frequency power source operating at a frequency of 70 MHz, with a peak power demand in the megawatt range. The vacuum system maintained a pressure of approximately 10⁻⁶ Torr to minimize beam scattering. Its ion sources were capable of producing intense beams from a variety of gaseous and solid feed materials.

Category:Particle accelerators Category:Lawrence Berkeley National Laboratory Category:Nuclear physics