First Radioactive Beam at ISAC
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TRILIS, "TRIUMF's Resonant Ionization Laser Ion Source" adds several tunable, pulsed lasers to the surface ionization source, such that all complexity of TRILIS is serviceable and far removed from the high temperature, radiation environment of the isotope production target. The delivery of 1.5*103 atoms/s of 62Ga (116 ms half-life) from the target-resonant laser ion source combination demonstrates the new possibilities for beam delivery, with an intensity enhancement of 2×, combined with a 20× suppression of the 62Cu isobaric contaminant over pure surface ionization.
This marks an important milestone for the isotope separator and accelerator facility (ISAC) as this opens up the availability of a wide range of radioactive isotopes that previously could not be ionized. Figure 1 shows that on top of the alkali metals and alkaline earths, now also most of the transition metals, lanthanides and actinide elements can be ionized. Thus more elements from the isotope production of the ISAC targets can be extracted as ion beams for experiments.
This marks an important milestone for the isotope separator and accelerator facility (ISAC) as this opens up the availability of a wide range of radioactive isotopes that previously could not be ionized. Figure 1 shows that on top of the alkali metals and alkaline earths, now also most of the transition metals, lanthanides and actinide elements can be ionized. Thus more elements from the isotope production of the ISAC targets can be extracted as ion beams for experiments.
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| Fig. 3. | The TRILIS laser system consists of one high power frequency doubled Nd:YAG laser (green), which simultaneously pumps three state of the art titanium:sapphire lasers, and associated frequency tripling. The tunable TiSa lasers and frequency tripling unit were developed with Mainz University and built at TRIUMF, as no commercial lasers are available to meet the specific RILIS requirements. |
The technique of "Resonant Ionization Mass Spectrometry", with its high selectivity and sensitivity, is key to the new laser ion source. Unlike conventional ion sources, resonant laser ionization uses the optical spectroscopic fingerprint for each element to provide selective ionization. Element-selective ionization, combined with the ISAC mass-separator provides new isotope beams of superior purity - which is essential to many high precision nuclear physics measurements.
The opportunity presented by the on-line test for TRILIS beam was seized by the 8π nuclear spectroscopy collaboration to measure the unknown nuclear branching ratios of 62Ga. About one year ahead of schedule TRILIS proves that state of the art, all solid-state laser systems are capable of providing the laser power and reliability needed for on-line ion-source operation. This has been the first time that such an all solid-state laser system has been used for on-line production of radioactive beams. The high repetition-rate, tunable, titanium:sapphire (TiSa) lasers are a special development for laser ion sources by our collaborators at the University of Mainz (Germany). The joint laser development continues.
The opportunity presented by the on-line test for TRILIS beam was seized by the 8π nuclear spectroscopy collaboration to measure the unknown nuclear branching ratios of 62Ga. About one year ahead of schedule TRILIS proves that state of the art, all solid-state laser systems are capable of providing the laser power and reliability needed for on-line ion-source operation. This has been the first time that such an all solid-state laser system has been used for on-line production of radioactive beams. The high repetition-rate, tunable, titanium:sapphire (TiSa) lasers are a special development for laser ion sources by our collaborators at the University of Mainz (Germany). The joint laser development continues.
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| Fig. 2. | Laser excitation scheme used for beam delivery in Dec 2004. With only one prototype frequency tripling unit a factor of 2× in 62Ga ion yield and a 20× suppression of the 62Cu background was achieved over surface ionization. |
