"Long before it's in the papers"
May 09, 2008

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Designer isotopes push frontiers

May 9, 2008
Courtesy U.S. National Science Foundation
and World Science staff

De­sign­er la­bels have ca­chet, and that may now be as true in phys­ics as in fash­ion.

The fu­ture of nu­clear phys­ics lies in de­sign­er iso­topes—the new tech­nol­o­gy of cre­at­ing rare vari­ants of chem­i­cal el­e­ments, ac­cord­ing to Mich­i­gan State Uni­ver­s­ity phys­i­cist Brad­ley Sher­rill. The vari­ants, called iso­topes, are de­signed to solve spe­cif­ic prob­lems and un­leash new tech­nolo­gies.

Par­t­i­cles are ac­cel­er­at­ed to up to half the speed of light as part of the rare-iso­tope cre­a­tion pro­cess at the Na­tion­al Su­per­con­duct­ing Cy­clo­tron Lab­o­ra­to­ry at Mich­i­gan State Uni­ver­si­ty in East Lan­sing, Mich. (Cour­te­sy NSCL)
Iso­topes are atoms of an el­e­ment that dif­fer only in their con­tent of sub­a­tom­ic par­t­i­cles called neu­trons. This dif­ference leaves the el­e­ment’s chem­i­cal prop­er­ties and name un­changed but does af­fect its ra­dioac­ti­vity, or ten­den­cy to dis­in­te­grate or “de­cay.”

“We have de­vel­oped a re­mark­a­ble ca­pa­bil­ity over the last 10 or so years that al­lows us to build a spe­cif­ic iso­tope to use in re­search,” said Sher­rill, who is as­so­ci­ate di­rec­tor for re­search at the uni­ver­s­ity’s Na­tional Su­per­con­duct­ing Cy­clo­tron Lab­o­r­a­to­ry. 

Sher­rill out­lined some of the pos­si­bil­i­ties and what it will take to get there in an ar­ti­cle in the May 9 edi­tion of the re­search jour­nal Sci­ence.

An­oth­er new re­search ar­ea known as nanotech­nol­o­gy is get­ting a lot of at­ten­tion for its as­ton­ish­ing abil­i­ties to build ob­jects with in­di­vid­ual atoms and mo­le­cules, Sher­rill not­ed. But he ar­gued that nanotech­nol­o­gy hardly is the last word in small. 

At facil­i­ties such the Cy­clo­tron Lab­o­r­a­to­ry, he wrote, sci­en­tists are mak­ing rare iso­topes by recre­at­ing the chem­i­cal changes that go on in the nu­clear fur­naces deep with­in stars. Rare iso­topes don’t al­ways ex­ist in na­ture, but can be coaxed out with high-en­er­gy col­li­sions cre­at­ed by spe­cial machines. 

Ad­vanc­es in bas­ic nu­clear sci­ence al­ready have led to med­i­cal tech­nolo­gies such as PET, or pos­i­tron emis­sion to­mog­ra­phy, Sher­rill wrote. These are scans that use spe­cial iso­topes to tar­get spe­cif­ic types of tu­mors. To cre­ate PET, sci­en­tists had to pro­duce an iso­tope with a spe­cif­ic ra­dioac­ti­vity that de­cayed quickly and safely enough to in­ject in the body.

The next step for U.S. nu­clear sci­ence will be the Facil­ity for Rare Iso­tope Beams, a cen­ter for the study of nu­clear struc­ture and nu­clear as­t­ro­phys­ics, Sher­rill wrote. The facil­ity is ex­pected to be built by the U.S. De­part­ment of En­er­gy in the next dec­ade, he added.

Cur­rent rare-i­so­tope re­search sup­ported by U.S. Na­tional Sci­ence Founda­t­ion at the Cy­clo­tron Lab­o­r­a­to­ry “en­ables us to push for­ward our un­der­stand­ing of nu­clei at the fron­tiers of sta­bil­ity, with di­rect con­nec­tions to the pro­cesses that pro­duce the el­e­ments in our world and that un­der­lie the life cy­cle of stars,” said Brad­ley Keis­ter, a pro­gram of­fic­er in founda­t­ion’s Phys­ics Di­vi­sion. “Ap­plica­t­ions to so­ci­e­tal ar­e­as in­clud­ing med­i­cine and se­cur­ity have tra­di­tion­ally gone hand in hand with these ever-advancing ca­pa­bil­i­ties.”

In the Sci­ence piece, Sher­rill wrote that ag­gres­sively pur­su­ing rare iso­tope re­search is a na­tional im­per­a­tive. “These are iso­topes that are not easy to pro­duce,” Sher­rill wrote. “A wid­er range of avail­a­ble iso­topes should ben­e­fit the fields of biomed­i­cine (by pro­duc­ing an ex­pand­ed port­fo­li­o of radioiso­topes), in­terna­t­ional se­cur­ity (by pro­vid­ing the tech­ni­cal un­der­pin­ning to nu­clear fo­ren­sics spe­cialists) and nu­clear en­er­gy (by lead­ing to bet­ter un­der­stand­ing of the sort of nu­clear re­ac­tions that will pow­er clean­er, next-genera­t­ion re­ac­tors).”

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Designer labels have cachet, and that may now be as true in physics as in fashion. The future of nuclear physics lies in designer isotopes—the new technology of creating rare variants of chemical elements, according to Michigan State University physicist Bradley Sherrill. These variants, called isotopes, are designed to solve specific problems and open doors to new technologies. Isotopes are atoms of an element that differ only in their content of subatomic particles called neutrons. This difference leaves the element’s chemical properties and name unchanged but does affect its radioactivity, or tendency to disintegrate or “decay.” “We have developed a remarkable capability over the last 10 or so years that allows us to build a specific isotope to use in research,” said Sherrill, who is associate director for research at the university’s National Superconducting Cyclotron Laboratory. Sherrill outlined some of the possibilities and what it will take to get there in an article in the May 9 edition of the research journal Science. Another new research area known as nanotechnology is getting a lot of attention for its astonishing abilities to build objects with individual atoms and molecules, Sherrill noted. But he argued that nanotechnology hardly is the last word in small. At facilities such the Cyclotron Laboratory, he wrote, scientists are making rare isotopes by recreating the chemical changes that go on in the nuclear furnaces deep within stars. Rare isotopes don’t always exist in nature, but can be coaxed out with high-energy collisions created by special machines. Advances in basic nuclear science already have led to medical technologies such as PET, or positron emission tomography, Sherrill wrote. These are scans that use special isotopes to target specific types of tumors. To create PET, scientists first had to create an isotope with a specific radioactivity that decayed quickly and safely enough to inject in the body. The next step for U.S. nuclear science will be the Facility for Rare Isotope Beams, a center for the study of nuclear structure and nuclear astrophysics, Sherrill wrote. The facility is expected to be built by the U.S. Department of Energy in the next decade, he added. Current rare-isotope research supported by U.S. National Science Foundation at the Cyclotron Laboratory “enables us to push forward our understanding of nuclei at the frontiers of stability, with direct connections to the processes that produce the elements in our world and that underlie the life cycle of stars,” said Bradley Keister, a program officer in foundation’s Physics Division. “Applications to societal areas including medicine and security have traditionally gone hand in hand with these ever-advancing capabilities.” In the Science piece, Sherrill wrote that aggressively pursuing rare isotope research is a national imperative. “These are isotopes that are not easy to produce,” Sherrill wrote. “A wider range of available isotopes should benefit the fields of biomedicine (by producing an expanded portfolio of radioisotopes), international security (by providing the technical underpinning to nuclear forensics specialists) and nuclear energy (by leading to better understanding of the sort of nuclear reactions that will power cleaner, next-generation reactors).”