A collaboration involving the Biomedical Research Foundation, Science Applications International Corporation, Fermi National Accelerator Laboratory, and the University of Washington is developing an accelerator for producing isotopes for Positron Emission Tomography (PET) scans. The Medium Energy Beam Transport (MEBT) section of this accelerator takes a small beam from a first RFQ acceleration device and matches it into a small 3D-acceptance at a second RFQ section. The beam transport system was designed to prevent beam losses due to emittance growth. The system includes two bending dipoles and seven quadrupoles of three different types. This report contains a brief description of the MEBT magnets and their electric, magnetic and thermal properties. The magnet measurements show that each of the magnets meets the system requirements.

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Magnet development for the BRF positron emission tomography accelerator

An RFQ linac has been built that accelerates 3He to 105 MeV for production of C, N, O, F isotopes for PET The accelerator produces 70 μs pulses, at 360 Hz, a 25% duty cycle, with a peak current of ∼6 mAe The RFQ delivers ∼100 μAe A recirculating water target has been evaluated for production of 18F and low specific activity 15O Recoil chemistry within the target has been evaluated to improve 15O specific activity Gas targets have also been tested for production of 15O 13N is made from carbon Several target materials have been evaluated for producing 11C, including C, B and Be The challenges of targetry for this high current, low energy machine led us to evaluate large, high aspect ratio windows and grid supports The 3He RFQ is a useful research machine for testing targets for pulsed, high power density, low LET beams

Production of PET radionuclides using a 10.5 MeV {sup 3}He RFQ accelerator

The /sup 3/He RFQ linac for production of positron-emitting radioactive isotopes accelerates singly-ionized /sup 3/He/sup +/ ions to an energy of 1 MeV in a 212.5-MHz RFQ. The ions are then stripped to form doubly-ionized /sup 3/He/sup ++/ in a gas-jet stripping cell, and transported by the MEBT to the 425-MHz RFQ string for acceleration to 10.5 MeV. The stripper cell utilizes a mechanical injector to provide gas pulses to a nozzle. The directed gas jet passes across the beam into a scavenge section which pumps away the gas. The MEBT is an achromatic, isochronous transport section based on two 270-degree bend magnets. It provides bunched and focused beam to the 425-MHz RFQ string.

Charge stripper and MEBT for the /sup 3/He RFQ accelerator

Improvements in the Fermilab operating 400-MeV linear accelerator injector are required to achieve the beam intensity and emittance requirement of the Proton Driver design study. It has been determined that these requirements can be achieved by replacing the components in the linac below 10 MeV. An improved H/sup -/ ion source with an electrostatic transport to a two-section radio-frequency quadrupole (RFQ) accelerator, with the RFQ sections separated by a magnetic five-dimensional phase-space imaging system as used in an earlier Fermilab/SAIC PET Project, and a new 10-MeV drift-tube linac cavity have been studied. It appears possible that an H/sup -/ intensity of 4.5/spl times/10/sup 13/ ions per pulse with an improvement in beam emittance from the present system can be achieved with the proposed changes.

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Low energy improvements to the Fermilab 400-MeV linear accelerator

Project status of the 3He ++ 10.5 MeV RFQ Linear Accelerator for the production of PET isotopes will be presented. The accelerator design was begun in September of 1995 with a goal of completion and delivery of the accelerator to BRF in Shreveport, Louisiana by the summer of 1997. The design effort and construction is concentrated in Lab G on the Fermilab campus. Some of the high lights include a 25 mA peak current 3He + ion source, four RFQ accelerating stages that are powered by surplus Fermilab linac RF stations, a gas jet charge doubler, and a novel 540 degree bending Medium Energy Beam Transport (MEBT). The machine is designed to operate at 360 Hz repetition rate with a 2.5% duty cycle. The average beam current is expected to be 150-300 micro amperes electrical, 75-150 micro amperes particle current. HISTORY

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A 3he ++ rfq accelerator for the production of pet isotopes

Production of positron emitting radioactive isotopes /sup 18/F, /sup 15/O, /sup 11/C and /sup 13/N for use in positron emission tomography is important for medical imaging. The present state of the production art is to use cyclotrons to accelerate deuterons to an energy range in the 10's of MeV and impinge the deuterons on appropriate targets. An alternative approach is to use a cascade of RFQ's to accelerate /sup 3/He ions to 10-MeV as the bombarding particles. Due to the lower background radiation, a /sup 3/He accelerator requires far less shielding than a cyclotron, in addition to other advantages. This paper will discuss briefly the end to end ion optics design of an RFQ based /sup 3/He PET accelerator. Emphasis will be on the medium energy beam transport (MEBT) portion. The MEBT required a solution to the difficult problem of matching two RFQ's while allowing room for a gas jet stripper. Our solution to this problem could be modified to allow a match between high power RFQ's and linacs, a problem faced by several possible future accelerators.

J. F. Ostiguy

Papers

Ion optical design of the BRF-FNAL-SAIC-UW PET accelerator