{"id":2481,"date":"2010-08-08T22:22:54","date_gmt":"2010-08-08T20:22:54","guid":{"rendered":"http:\/\/localhost\/azgad\/wordpress\/?p=2481"},"modified":"2010-08-08T22:25:48","modified_gmt":"2010-08-08T20:25:48","slug":"pushing-the-boundaries-of-the-isotope-frontier-discovery-of-45-rare-neutron-rich-isotopes-provides-clues-to-the-stellar-formation-of-heavy-elements","status":"publish","type":"post","link":"https:\/\/azgad.com\/?p=2481","title":{"rendered":"Discovery of 45 rare neutron-rich isotopes provides clues to the stellar formation of heavy elements"},"content":{"rendered":"

.
\nMany of Earth\u2019s resources, from copper to more precious metals, are often
\ntaken for granted, but the only place to make more of these elements lies at
\n the interior of stars. Despite this cosmological reality, however, scientists are
\n yet to fully understand the stellar process that produces many of the heavier
\n elements in the periodic table. Now, with the discovery of 45 new, rare isotopes
\n by a team of scientists lead by Toshiyuki Kubo at RIKEN\u2019s Nishina Center in
\n Wako, hopes are high to establish an understanding of the nuclear process
\n that produces roughly half the elements heavier than iron. The discoveries,
\n published in the Journal of the Physical Society of Japan1, are some of the first
\n results from the Radioactive Isotope Beam Factory (RIBF), a next-generation
\nheavy-ion accelerator designed to explore the structure of exotic, neutron-rich
\nisotopes.
\n.
\nStellar insights<\/strong>
\n.
\nAll of the known elements and their isotopes are collected in the \u2018Table of Nuclides\u2019,
\na continuously updated chart that is organized according to how many protons
\nand neutrons each isotope contains.
\nThe RIBF was designed to explore the outer limits of this chart, near the so-called
\n neutron \u2018drip-line\u2019, where nuclei can be produced only by collisions in particle
\naccelerators. These nuclei contain so many neutrons they survive for only fractions
\nof a second before decaying to more stable forms.
\n.
\nNeutron-rich isotope research is important for understanding how stars produce elements
\n of the periodic table. Fusion, where two high-energy nuclei merge, occurs in stars and
\ncan form elements up to iron. However, scientists believe that roughly half of the elements
\nheavier than iron are produced by the so-called \u2018r-process\u2019, where r stands for rapid.
\n.
\n During the r-process, a nucleus is bombarded and bloated with neutrons so rapidly that it has
\nno time to stabilize by beta decay; instead, it decays through a series of unstable intermediate
\n nuclei. According to theoretical models, many of the rare isotopes discovered using the RIBF
\n act as the intermediate nuclei in the r-process.
\n\u201cIf we understand the structure of the nuclei of these new neutron-rich isotopes, we can better
\nunderstand the path and pace of the r-process and how the process is constrained by
\ntemperature and density,\u201d says Mike Famiano, a member of Kubo\u2019s team.
\n.
\nThe rapid-fire flux of neutrons required for the r-process likely only occurs at the interior of
\nexploding stars called supernova (Fig. 3). As such, the RIBF research is providing a unique
\n glimpse into a rare and distant stellar process.
\n.
\nBreak and measure<\/strong>
\n.
\nThe RIBF produces rare isotopes by accelerating ionized uranium-238\u2014an element heavy
\n enough to break into other large nuclei\u2014to close to the speed of light and then smashing
\n these ions into a target of beryllium or lead. The collision causes the uranium nucleus to
\n undergo fission and split into smaller nuclear \u2018fragments\u2019 that are collected and analyzed
\n in the fractions of a second before they decay.
\n.
\nIt was in such fragments that Kubo and colleagues discovered the 45 new isotopes, which span
\n the periodic table from manganese to barium. To produce fragments over this wide range,
\nKubo\u2019s team designed a means of identifying the nuclear fragments quickly and accurately,
\n and the RIBF accelerator group designed a cyclotron capable of accelerating uranium.
\n.
\nThe RIBF cyclotron uses powerful superconducting magnets to cycle the uranium ions
\nthrough an accelerating voltage multiple times, until the ions reach speeds 70% of the speed
\nof light.
\n.
\nThe \u2018brains\u2019 of the RIBF is the in-flight separator, dubbed \u2018BigRIPS\u2019, which analyzes the
\n fragments of the fissile uranium. Superconducting magnets in the separator force the
\nfast-moving nuclei to fan out with different curvatures, allowing the team to determine the
\natomic number and the ratio of charge to mass of each nucleus\u2014some of which were
\n produced only once in the collision.
\n.
\nKubo and his team\u2019s results not only provide insights into the stellar production of heavy
\nelements, but also enable them to test the limits of theoretical models for more stable nuclei.
\nKubo says they will next focus on the new isotopes palladium-128 and nickel-79 because
\n they are similar to the nuclei with a so-called \u2018magic\u2019 number of neutrons or protons\u20142, 8,
\n20, 28, 50 and 82\u2014which are extraordinarily stable. Palladium-128 has 82 neutrons, while
\nnickel-79 has one more than the magic number of 50 neutrons. Near the neutron drip-line,
\n however, nuclei may have different magic numbers, a possibility that the new isotopes
\nwill allow nuclear physicists to test.
\n.
\nA pioneer<\/strong>
\n.
\nAs the first next-generation accelerator for studying rare isotopes, the RIBF is in prime
\nposition to keep opening new doors in nuclear physics research. Similar facilities are
\nunder construction in Germany and in the US and Kubo points out that the teams
\nworking at three new-generation facilities are already collaborating with each other.
\n Given the funding necessary to plan, design and construct such large facilities\u2014on
\n the order of 500 million US dollars (50 billion yen)\u2014the results from RIKEN\u2019s RIBF
\nwill continue to provide motivational fuel for these efforts.
\n.
\n\u201cThe discovery of new, rare isotopes is the first validation of the extended capability
\nof these new-generation facilities,\u201d explains Kubo. The aim now is to increase the
\n intensity of the uranium beam at RIBF by 1,000 times higher than present. \u201cWe
\nexpect to discover many new isotopes and expand the frontier of nuclear physics
\n to a large extent.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":"

. Many of Earth\u2019s resources, from copper to more precious metals, are often taken for granted, but the only place to make more of these elements lies at the interior of stars. Despite this cosmological reality, however, scientists are yet to fully understand the stellar process that produces many of the heavier elements in the … <\/p>\n

\u05d4\u05de\u05e9\u05d9\u05db\u05d5 \u05d1\u05e7\u05e8\u05d9\u05d0\u05d4<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"categories":[10],"tags":[142,513,293,49],"class_list":["post-2481","post","type-post","status-publish","format-standard","hentry","category-10","tag-142","tag-513","tag-293","tag-49","nodate","item-wrap"],"_links":{"self":[{"href":"https:\/\/azgad.com\/index.php?rest_route=\/wp\/v2\/posts\/2481","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/azgad.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/azgad.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/azgad.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/azgad.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=2481"}],"version-history":[{"count":3,"href":"https:\/\/azgad.com\/index.php?rest_route=\/wp\/v2\/posts\/2481\/revisions"}],"predecessor-version":[{"id":2484,"href":"https:\/\/azgad.com\/index.php?rest_route=\/wp\/v2\/posts\/2481\/revisions\/2484"}],"wp:attachment":[{"href":"https:\/\/azgad.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=2481"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/azgad.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=2481"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/azgad.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=2481"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}