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Acceleration of radioisotopes opens up research on synthesis of elements at the explosion of supernovaJun. 18, 2008High Energy Accelerator Research Organization (KEK) and Japan Atomic Energy Agency (JAEA) have succeeded in accelerating radioisotopes of indium-123 (half-life of 6 seconds) and barium-143 (half-life of 14 seconds), using Tokai Radioactive Ion Accelerator Complex (TRIAC), for the first time in the world. Overview Short-lived isotopes of indium and barium were produced by bombarding a uranium target with a proton beam accelerated with the tandem accelerator. Acceleration of radioisotopes requires that those isotopes are extracted and separated as ions with a charge state of 1+, and then converted with a highly charge state of about 20+. JAEA has developed an ion-source for producing 1+ ions of radioisotopes by diffusing and evaporating them from the uranium target rapidly. KEK has developed a charge breeder, producing highly charged ions by bombarding 1+ ions with high-energy electrons in the plasma. These developments allowed us to accelerate short-lived isotopes with the intensities of about 10000 per second and to supply them to experiments. Accelerators for short-lived isotopes are classified broadly into two types. One is a re-acceleration type; short-lived isotopes are stopped in the target and then re-accelerated. The other is a fragmentation type; short-lived isotopes are transported as the velocity recoiled out from the target. TRIAC is the former type, which supplies a high-quality and variable-energy beam. TRIAC is racing with this type of accelerators constructed in USA, Canada and EU. It is inferred that elements heavier than iron come into existence at the place with extremely high neutron density created by the explosion of supernova. Under such a circumstance, neutrons are absorbed by short-lived isotopes. The present success of accelerating short-lived indium and barium isotopes enabled us to simulate nuclear reactions between neutrons and short-lived isotopes, opening up research on the origin of elements in universe. |
