Bulletin of the American Physical Society
4th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Volume 59, Number 10
Tuesday–Saturday, October 7–11, 2014; Waikoloa, Hawaii
Session 1WB: Developments in Confinement Techniques for Precision Low-Energy Nuclear Physics Experiments with Radioactive Ion Beams |
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Chair: Maxime Brodeur, University of Notre Dame Room: Kohala 2 |
Tuesday, October 7, 2014 9:00AM - 9:30AM |
1WB.00001: OROCHI experiment: Laser spectroscopy of RI atoms in superfluid helium for measurements of nuclear spins and electromagnetic moments Invited Speaker: Takeshi Furukawa We have been developing a new laser spectroscopy technique named as OROCHI (Optical RI-atom Observation in Condensed Helium as Ion-catcher) for measurements of nuclear spins and electromagnetic moments of low yield exotic radioisotopes (RIs). In this technique, we use superfluid helium (He II) liquid as a stopping material of RI beam in which in-situ laser spectroscopy of the RI atoms stopped in He II is carried out. The characteristic features of He II, i.e. high trapping efficiency of He II liquid for accelerated ion beams and the characteristics of atomic spectra in He II, enables us to measure the nuclear spins and moments of the extremely low yield RIs. So far, we have demonstrated the feasibility of our method to deduce the nuclear spins and moments with stable Rb, Cs, Ag and Au isotopes supplied into He II by laser sputtering technique. In addition, we have also succeeded in observing laser-radiowave/microwave double resonance signals of $^{84-87}$Rb atoms injected into He II as energetic ion beam. In these on-line experiment, the $^{84-87}$Rb isotope beams (intensity: up to 10$^{5}$ particles/s) were provided with RIPS beamline in RIKEN, and introduced into He II filled in a cryostat. Special care was taken in controlling the stopping position of injected Rb isotopes. Aluminum energy degraders of varied thickness from 0 to 0.8 mm were placed upstream of the beam injection window of the He II cryostat for optimizing the stopping position The $^{84-87}$Rb atoms stopped and then neutralized in He II were optically pumped and polarized with circularly polarized pumping laser light whose wavelength were tuned to 780 nm, D1 absorption line of Rb atoms in He II. The polarized atoms were subjected to irradiation of radiowave or microwave, and then we demonstrated the double resonance spectroscopy for observing the Zeeman transition of $^{84-87}$Rb atoms and the hyperfine transition of $^{87}$Rb, respectively In this presentation we will show the details of OROCHI technique and the present status of our development, in particular the result of the recent on-line experiment. [Preview Abstract] |
Tuesday, October 7, 2014 9:30AM - 10:00AM |
1WB.00002: SIPT---An Ultrasensitive Mass Spectrometer for Rare Isotopes Invited Speaker: Ryan Ringle Over the last few decades, advances in radioactive beam facilities like the Coupled Cyclotron Facility at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University (MSU) have made short-lived, rare-isotope beams available for study in various science areas, and new facilities, like the Facility for Rare Isotope Beams (FRIB) under construction at MSU, will provide even more exotic rare isotopes. The determination of the masses of these rare isotopes is of utmost importance since it provides a direct measurement of the binding energy of the nucleons in the atomic nucleus. For this purpose we are currently developing a dedicated Single-Ion Penning Trap (SIPT) mass spectrometer at NSCL to handle the specific challenges posed by rare isotopes. These challenges, which include short half-lives and extremely low production rates, are dealt with by employing the narrowband FT-ICR detection method under cryogenic conditions. Used in concert with the 9.4-T time-of-flight mass spectrometer, the 7-T SIPT system will ensure that the LEBIT mass measurement program at MSU will make optimal use of the wide range of rare isotope beams provided by the future FRIB facility, addressing such topics as nuclear structure, nuclear astrophysics, and fundamental interactions. [Preview Abstract] |
Tuesday, October 7, 2014 10:00AM - 10:30AM |
1WB.00003: Search for a permanent EDM with laser cooled radioactive atom Invited Speaker: Yasuhiro Sakemi To explore the mechanism for the generation of the matter-antimatter asymmetry in the universe, the study on fundamental symmetry violation using the trapped radioactive atoms with laser cooling techniques is being promoted. An Electric Dipole Moment (EDM) of the elementary particle is a good prove to observe the phenomena beyond the Standard Model. A finite value of EDM means the violation of the time reversal symmetry, and the CP violation under the CPT invariance. In paramagnetic atoms, an electron EDM results in an atomic EDM enhanced by the factor of the 3rd power of the charge of the nucleus due the relativistic effects. A heaviest alkali element francium (Fr), which is the radioactive atom, has the largest enhancement factor K $\sim$ 895 in atomic system. Then, we are developing a high intensity laser cooled Fr factory at Cyclotron and Radioisotope Center (CYRIC), Tohoku University to search for the EDM of Fr with the accuracy of 10-29 e cm. To overcome the current accuracy limit of the EDM, it is necessary to realize the high intensity Fr source and to reduce the systematic error due to the motional magnetic field and inhomogeneous applied field. To reduce the dominant component of the systematic errors mentioned above, we will confine the Fr atoms in the small region with the Magneto-Optical Trap (MOT) and optical lattice using the laser cooling and trapping techniques. The construction of the experimental apparatus is making progress, and the new thermal ionizer already produces the Fr of $\sim$ 10 6 ions/s with the primary beam intensity 200 nA. The extracted Fr ion beam is transported to the neutralizer, which is located 10 m downstream, and the produced neutral Fr atoms are introduced into the MOT to load the next trapping system such as the optical dipole force trap and optical lattice. The coherence time will be increased in the laser trapping system, and the present status of the experiment will be reported. [Preview Abstract] |
Tuesday, October 7, 2014 10:30AM - 11:00AM |
1WB.00004: COFFEE BREAK |
Tuesday, October 7, 2014 11:00AM - 11:30AM |
1WB.00005: TAMU-TRAP: an ion trap facility for Weak Interaction and Nuclear Physics Studies Invited Speaker: Praveen Shidling In the low-energy regime, precision measurements of nuclear $\beta $-decay continue to be an efficient tool to search for new physics beyond the standard electroweak model and is the most abundant weak interaction phenomenon. The $\beta $-decay experiments carried out until now can be explained by a time reversal-invariant pure V-A interaction with maximal violation of parity. Nevertheless, experimental error bars still leave sufficient room for the possible existence of other types of weak interaction in beta decay. The primary goal of the TAMU-TRAP facility is to test the standard model for a possible admixture of a scalar type of interaction by measuring the $\beta $-$\nu $ correlation parameter, a$_{\mathrm{\beta \nu }}$, in T$=$2 super-allowed $\beta $-delayed proton emitters. The a$_{\mathrm{\beta \nu }}$ correlation parameter can be inferred by measuring the proton energy spectrum. Low energy radioactive ion beam (RIB) will be delivered to the facility through the Heavy Ion guide, which is part of the T-REX(TAMU-Reaccelerated EXotics) upgrade project. The main components of the facility are an RFQ (cooler/buncher) and a Penning trap system. The measurement trap will be a large-bore cylindrical Penning trap with 90 mm radius, larger than any existing Penning trap. This geometry will allow for full radial containment of decay products of interest. The trap geometry is also suitable for a wide range of nuclear physics experiments. Additional goals for this system are mass and lifetime measurements. Presently, the TAMUTRAP setup is under construction and is being coupled to the T-REX upgrade project. Several parts of the beamline have been tested using an offline ion source. A brief overview of the TAMU-TRAP set-up, its current status, and the status of the T-REX upgrade project will be presented. [Preview Abstract] |
Tuesday, October 7, 2014 11:30AM - 12:00PM |
1WB.00006: MRTOF for high-precision mass measurements at RIKEN Invited Speaker: Yuta Ito At RIKEN, a multi-reflection time-of-flight mass spectrograph (MRTOF) has been developed for mass measurements of short-lived ($T_{1/2} \ll 100$~ms) and low-yield nuclei. By using a pair of electrostatic mirrors which create an energy isochronous condition, the flight path for an ion pulse could be extended indefinitely and it's possible to achieve reasonably large resolving powers ($m/\Delta m>150,000$) in shorter observation time, e.g., $\sim$2.3~ms for $A/q=40$ [1], than could be achieved by other techniques. Recently, online mass measurements of unstable nuclei using single-reference method were performed [2] and an advanced wide-band mass measurement technique have been developed [3]. Based on these developments and the success of experiments, two MRTOF projects are now ongoing at RIKEN: mass measurements of trans-Uranium nuclei at GARIS-II and of r-process nuclei at BigRIPS/SLOWRI. We hope that with mass measurements with the MRTOF over the wide region from light to superheavy, one can drastically extend the mass information, and understand nuclear structures and astrophysical process in detail. We will present current status and future outlook. \\[4pt] [1] P.\ Schury et al., Nucl.\ Instrum.\ Meth.\ B 335, 39 (2014) \\[0pt] [2] Y.\ Ito et al., Phys.\ Rev.\ C 88, 011306 (2013) \\[0pt] [3] P.\ Schury et al., Int.\ J.\ Mass Spectrom.\ 359, 19 (2014) [Preview Abstract] |
Tuesday, October 7, 2014 12:00PM - 12:30PM |
1WB.00007: Measurements of $\beta $-delayed neutron emission probabilities using a Paul trap Invited Speaker: Nicholas Scielzo Neutrons emitted following the $\beta $ decay of neutron-rich isotopes play an important role in many fields of basic and applied science. Studies of these $\beta $-delayed neutrons are needed to better understand the structure of exotic nuclei and how the isotopes synthesized in r-process environments decay back to stability to produce the isotopic abundances observed today. In addition, precise studies of fission products provides valuable information for nuclear energy and stockpile stewardship applications. However, the data available today for individual nuclei is limited - for the vast majority of neutron emitters, the energy spectrum has not been measured and some recent measurements have uncovered discrepancies in $\beta $-delayed neutron branching ratios. Radioactive ions held in an ion trap are an appealing source of activity for improved studies of this $\beta $-delayed neutron emission process. When a radioactive ion decays in the trap, the recoil-daughter nucleus and emitted particles emerge from the approximately 1-mm$^{\mathrm{3}}$ trap volume with minimal scattering and propagate unobstructed through vacuum. These properties allow, for the first time, the momentum and energy of the emitted neutron to be precisely reconstructed from the nuclear recoil. By loading neutron-rich fission-product beams from the CARIBU facility at Argonne National Laboratory into a specially-designed radiofrequency quadrupole ion trap system, a program of $\beta $-delayed neutron spectroscopy in this largely unexplored region of the nuclear chart can be performed. This recoil-ion technique will be described and results from recent measurements at CARIBU and future prospects will be discussed. [Preview Abstract] |
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