Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Pushing the boundaries of the isotope frontier

09.08.2010
Many of Earth’s 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.

Discovery of 45 rare neutron-rich isotopes provides clues to the stellar formation of heavy elements

Many of Earth’s 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 periodic table. Now, with the discovery of 45 new, rare isotopes by a team of scientists lead by Toshiyuki Kubo at RIKEN’s Nishina Center in Wako, hopes are high to establish an understanding of the nuclear process that produces roughly half the elements heavier than iron. The discoveries, published in the Journal of the Physical Society of Japan1, are some of the first results from the Radioactive Isotope Beam Factory (RIBF), a next-generation heavy-ion accelerator designed to explore the structure of exotic, neutron-rich isotopes.

Stellar insights

All of the known elements and their isotopes are collected in the ‘Table of Nuclides’, a continuously updated chart that is organized according to how many protons and neutrons each isotope contains.

The RIBF was designed to explore the outer limits of this chart, near the so-called neutron ‘drip-line’, where nuclei can be produced only by collisions in particle accelerators. These nuclei contain so many neutrons they survive for only fractions of a second before decaying to more stable forms.

Neutron-rich isotope research is important for understanding how stars produce elements of the periodic table. Fusion, where two high-energy nuclei merge, occurs in stars and can form elements up to iron. However, scientists believe that roughly half of the elements heavier than iron are produced by the so-called ‘r-process’, where r stands for rapid. During the r-process, a nucleus is bombarded and bloated with neutrons so rapidly that it has no time to stabilize by beta decay; instead, it decays through a series of unstable intermediate nuclei. According to theoretical models, many of the rare isotopes discovered using the RIBF act as the intermediate nuclei in the r-process.

“If we understand the structure of the nuclei of these new neutron-rich isotopes, we can better understand the path and pace of the r-process and how the process is constrained by temperature and density,” says Mike Famiano, a member of Kubo’s team.

The rapid-fire flux of neutrons required for the r-process likely only occurs at the interior of exploding stars called supernova. As such, the RIBF research is providing a unique glimpse into a rare and distant stellar process.

Break and measure

The RIBF produces rare isotopes by accelerating ionized uranium-238—an element heavy enough to break into other large nuclei—to close to the speed of light and then smashing these ions into a target of beryllium or lead. The collision causes the uranium nucleus to undergo fission and split into smaller nuclear ‘fragments’ that are collected and analyzed in the fractions of a second before they decay.

It was in such fragments that Kubo and colleagues discovered the 45 new isotopes, which span the periodic table from manganese to barium. To produce fragments over this wide range, Kubo’s team designed a means of identifying the nuclear fragments quickly and accurately, and the RIBF accelerator group designed a cyclotron capable of accelerating uranium.

The RIBF cyclotron uses powerful superconducting magnets to cycle the uranium ions through an accelerating voltage multiple times, until the ions reach speeds 70% of the speed of light.

The ‘brains’ of the RIBF is the in-flight separator, dubbed ‘BigRIPS’, which analyzes the fragments of the fissile uranium. Superconducting magnets in the separator force the fast-moving nuclei to fan out with different curvatures, allowing the team to determine the atomic number and the ratio of charge to mass of each nucleus—some of which were produced only once in the collision.

Kubo and his team’s results not only provide insights into the stellar production of heavy elements, but also enable them to test the limits of theoretical models for more stable nuclei. Kubo says they will next focus on the new isotopes palladium-128 and nickel-79 because they are similar to the nuclei with a so-called ‘magic’ number of neutrons or protons—2, 8, 20, 28, 50 and 82—which are extraordinarily stable. Palladium-128 has 82 neutrons, while nickel-79 has one more than the magic number of 50 neutrons. Near the neutron drip-line, however, nuclei may have different magic numbers, a possibility that the new isotopes will allow nuclear physicists to test.

A pioneer

As the first next-generation accelerator for studying rare isotopes, the RIBF is in prime position to keep opening new doors in nuclear physics research. Similar facilities are under construction in Germany and in the US and Kubo points out that the teams working at three new-generation facilities are already collaborating with each other. Given the funding necessary to plan, design and construct such large facilities—on the order of 500 million US dollars (50 billion yen)—the results from RIKEN’s RIBF will continue to provide motivational fuel for these efforts.

“The discovery of new, rare isotopes is the first validation of the extended capability of these new-generation facilities,” explains Kubo. The aim now is to increase the intensity of the uranium beam at RIBF by 1,000 times higher than present. “We expect to discover many new isotopes and expand the frontier of nuclear physics to a large extent.”

About the Researcher

Toshiyuki Kubo

Toshiyuki Kubo was born in Tochigi, Japan, in 1956. He received his BS degree in physics from The University of Tokyo in 1978, and his PhD degree from the Tokyo Institute of Technology in 1985. He joined RIKEN as an assistant research scientist in 1980, and was promoted to research scientist in 1985 and to senior research scientist in 1992. He spent time at the National Superconducting Cyclotron Laboratory of Michigan State University in the USA as a visiting physicist from 1992 to 1994. In 2001, he became leader of the BigRIPS team, and was promoted to group director of the research instruments group at the RIKEN Nishina Center in 2007. He is in charge of the design, construction, development and operation of major research instruments, as well as related infrastructure and equipment, at the RIKEN Nishina Center. His current research focuses on the production of rare isotope beams, in-flight separator issues, and the structure and reactions of exotic nuclei.

An image of a supernova in Spiral Galaxy M100. The high neutron flux in supernova is needed for the process that underlies the synthesis of roughly half the elements heavier than iron.
Copyright : credit: ESO/NASA

Journal information
1. Ohnsihi, T., Kubo, T., Kusaka, K., Yoshida, A., Yoshida, K., Ohtake, M., Fukuda, N., Takeda, H., Kameda, D., Tanaka, K., et al. Identification of 45 new neutron-rich isotopes produced by in-flight fission of a 238U beam at 345 MeV/nucleon. Journal of the Physical Society of Japan 79, 073201 (2010)

gro-pr | Research asia research news
Further information:
http://www.researchsea.com/html/article.php/eml/1/aid/5419/cid/1
http://www.researchsea.com

More articles from Physics and Astronomy:

nachricht Measured for the first time: Direction of light waves changed by quantum effect
24.05.2017 | Vienna University of Technology

nachricht Physicists discover mechanism behind granular capillary effect
24.05.2017 | University of Cologne

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A quantum walk of photons

Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.

The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....

Im Focus: Turmoil in sluggish electrons’ existence

An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.

We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.

Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...

Im Focus: World's thinnest hologram paves path to new 3-D world

Nano-hologram paves way for integration of 3-D holography into everyday electronics

An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...

Im Focus: Using graphene to create quantum bits

In the race to produce a quantum computer, a number of projects are seeking a way to create quantum bits -- or qubits -- that are stable, meaning they are not much affected by changes in their environment. This normally needs highly nonlinear non-dissipative elements capable of functioning at very low temperatures.

In pursuit of this goal, researchers at EPFL's Laboratory of Photonics and Quantum Measurements LPQM (STI/SB), have investigated a nonlinear graphene-based...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

 
Latest News

Physicists discover mechanism behind granular capillary effect

24.05.2017 | Physics and Astronomy

Measured for the first time: Direction of light waves changed by quantum effect

24.05.2017 | Physics and Astronomy

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

VideoLinks
B2B-VideoLinks
More VideoLinks >>>