Abstract
A test stand for development of ion sources for radioactive beams is currently being commissioned at Argonne. It is located at the Physics Division’s Dynamitron accelerator which will be used as a neutron generator with a flux of up to 1011 neutrons per second created by reactions of 4 MeV deuterons on various targets with beam currents of up to 100 μA. The primary targets will be located adjacent to heated secondary targets inside an on-line ion source. With this neutron-generator facility it will be possible to produce radioactive beams of various isotopes, such as He6, Na24, and neutron-rich fission fragments. For example, with a secondary target of uranium carbide containing 25 g of natural or depleted uranium the yields of individual isotopes in the target will be about 107/s for isotopes such as Sn132, Xe140, and Cs142, near the peak of the fission distribution. The ion sources to be evaluated will be located within a shielded cave with walls consisting of 30 cm of steel plus 60 cm of concrete to attenuate the prompt neutron radiation by a factor of about 104. Secondary beams of radioactive fission fragments with intensities on the order of 106/s per isotope will be extracted in the 1+ charge state at energies of 20 keV and mass separated with a Danfysik mass separator. Light isotopes, such as He6 and Na24, can be produced via (n,α) and (n,p) reactions on appropriate target materials. Commissioning began with measurements of fission yields from primary targets of C, Be, BeO, and BN. A surface ionization source which is a variation of the one used in the TRISTAN on-line mass seperator facility at Brookhaven National Laboratory has been installed and tested with stable Rb and Cs beams. The isotope separator was also commissioned with these beams. The development program will include emittance measurements and source optimization, initially with stable beams, and target-delay-time and release-efficiency measurements for various target/secondary-beam systems.
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