Physics Research at FSU
Experimental Nuclear Physics
The Experimental Nuclear Physics group at FSU
The United States is entering a golden age for nuclear physics. Physicists are now examining nuclei that display remarkable sizes, shapes and behaviors using advanced accelerator facilities and detector equipment available at Florida State University’s Superconducting Linear Accelerator and at other laboratories around the world. From these observations, scientists are achieving a deep understanding of how protons and neutrons interact in nuclei. They are learning how the quarks and mesons contained in the nucleus affect nuclear behavior and mining new knowledge about the most fundamental structures in nature using the Continuous Electron Beam Accelerator Facility at the Thomas Jefferson National Laboratory in Virginia. At the Relativistic Heavy Ion Collider at Brookhaven National Laboratory, nuclei are heated in collisions to temperatures so high that the protons and neutrons evaporate into individual quarks and gluons, forming a fluid that replicates the conditions existing in the first microseconds of the universe. Experiments in which atomic nuclei are spun at some of the highest angular velocities ever recorded in a nucleus are performed at FSU’s own Superconducting Linear Accelerator using a gamma-ray detection facility which includes state-of-the-art Ge detector technology.
FSU physicists are also using the world’s most powerful gamma-ray "microscope", GAMMASPHERE, located at Argonne National Laboratory near Chicago. High angular velocity induces novel effects involving nuclear correlations (superfluidity), exotic shapes (superdeformation), and the interplay of single particle and collective degrees of freedom. The FSU faculty members involved in this work are Dr. Mark Riley and Dr. Sam Tabor.
FSU physicists are looking at exotic nuclei that have imbalances in the numbers of protons and neutrons that are so large that they are only weakly bound. These nuclei have shapes that are quite different from those observed in stable nuclei and give us critical new information about how the protons and neutrons in nuclei interact. Nuclei which are proton- or neutron-rich can have "halos" or "skins" of protons or neutrons at the nuclear surface. In addition, the nuclear "shell structure", which in stable nuclei is similar to the electron shell structure found in atoms, may change significantly in nuclei far from stability. Information about proton- and neutron-rich nuclei is also important in understanding the nuclear reactions which power stars and produce the elements and the structure of neutron stars. Some experiments are performed at the FSU Superconducting Linear Accelerator with the laboratory’s array of germanium gamma-ray detectors. Other experiments are performed at the National Superconducting Cyclotron Laboratory, the world’s leading laboratory for the study of fast beams of exotic nuclei, which is located at Michigan State University. Yet other experiments are done at the Grand Accelerateur National d’Ions Lourds (GANIL), a French National nuclear physics laboratory located in the city of Caen. FSU faculty members involved in this work include Dr. Paul Cottle, Dr. Kirby Kemper, Dr. Mark Riley, Dr. Grigory Rogachev, Dr. Sam Tabor, and Dr. Ingo Wiedenhover.
Research by FSU nuclear physicists is also focused on astrophysical topics. The fuel of stellar nova-explosions, X-ray bursts or super-nova explosions are very short-lived nuclei, which in nature only exist during these stellar events. Therefore, many of their properties are unknown, which induces significant uncertainties in the theoretical calculations of stellar explosions. That is about to change when a large-scale national laboratory called RIA (Rare Isotope Accelerator) is realized, which will be dedicated to the research with these short-lived isotopes. The FSU nuclear physics group will also be among the leading users of RIA when it becomes operational. In the meantime in Tallahassee, Dr. Ingo Wiedenhover working together with colleagues in the nuclear research group is establishing an experimental program to answer some of those interesting questions (before everybody else gets a shot at it with RIA). The group has built a facility called RESOLUT at the FSU superconducting linear accelerator laboratory, which allows us to produce and purify high quality beams of short-lived, exotic nuclei.
The FSU Nuclear Physics Program is playing a major role in the effort to produce and detect the quark-gluon plasma - the state of matter that existed a few microseconds after the Big Bang and before the universe cooled enough to form protons and neutrons - in collisions of 100 GeV/nucleon gold nuclei at the Relativistic Heavy Ion Collider (RHIC), which began operations in 2000. An important component of the PHENIX detector - one of the two largest detectors at RHIC - was constructed at the FSU Nuclear Physics Laboratory’s own machine shop. FSU’s Dr. Tony Frawley is presently has the title of Run Coordinator for PHENIX. As Run Coordinator, Dr. Frawley is the scientist in charge of the day-to-day operation of the detector.
FSU physicists are exploring the hadronic nuclear matter utilizing the continuous electron beam accelerator at Thomas Jefferson National Laboratory. They are working to uncover how quarks and gluons behave in atomic nuclei with electron scattering and photproduction experiments. Dr. Volker Crede and Dr. Paul Eugenio are leaders in the effort to double the energy of Jefferson Lab's accelerator, which will make possible the production of a whole new class of matter-- gluonic matter. A major part of the Jefferson Lab upgrade is the construction of a hermetic detector (GlueX Experiment) in a new experimental hall (Hall D) which will be used to detect this new family of matter. Dr. Eugenio's expertise in partial wave analysis allows FSU to build on its strengths in theoretical and computational physics and apply these techniques to further enhance the nuclear research at CLAS, Jefferson Lab's large acceptance spectrometer in Hall B, and eventually to take full advantage of the upgrade to Jefferson Lab.
The combination of faculty expertise in atomic physics, laser physics and nuclear physics has made it possible to construct the world’s most productive source of polarized heavy ions. The laser optically-pumped polarized lithium source produces intense beams of Li-6 and Li-7 in which the nuclear spins are aligned. These beams are used to probe the scattering reactions between the lithium and other complex nuclei, expanding our knowledge about how protons and neutrons interact in colliding nuclei.
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