P. Schury

Single-reference high-precision mass measurement with a multi-reflection time-of-flight mass spectrograph

A multi-reflection time-of-flight mass spectrograph, competitive with Penning trap mass spectrometers, has been built at RIKEN. We have performed a first online mass measurement, using 8Li+ (T1/2 = 838 ms). A new analysis method has been realized, with which, using only 12C+ references, the mass excess of 8Li was accurately determined to be 20947.6(15)(34) keV (dm/m = 6.6 x 10-7). The speed, precision and accuracy of this first online measurement exemplifies the potential for using this new type of mass spectrograph for precision measurements of short-lived nuclei.

Restoration of RI‐beams from a projectile fragment separator by Laser Ionization gas Catcher‐PALIS‐

A fragment separator at heavy ion accelerator facilities is a versatile instrument to provide wide variety of radioactive isotope (RI) beams. However, more than 99.99% of precious RI‐ions are simply dumped in the slits or elsewhere in the fragment separator. A novel concept to restore such RI‐ions for parasitic slow RI‐beams is proposed. Installation of a laser ionization gas catcher in the vicinity of the first or second focal point of the fragment separator enables to collect dead isotopes in the slits. The design concept and expected performance are discussed.

Wide-band mass measurements with a multi-reflection time-of-flight mass spectrograph

Abstract We introduce a new concomitant referencing mode for operating a multi-reflection time-of-flight mass spectrograph (MRTOF-MS), wherein the reference and analyte ions are interleaved on a cycle by cycle basis. Using this mode, we demonstrate an improved technique for performing wide bandwidth mass measurements via MRTOF-MS. This new technique offers a simplified analysis and high accuracy.

First online multireflection time-of-flight mass measurements of isobar chains produced by fusion-evaporation reactions: Toward identification of superheavy elements via mass spectroscopy

P. Schury, 2 M. Wada, 2 Y. Ito, D. Kaji, P.-A. Söderström, A. Takamine, F. Arai, H. Haba, S. Jeong, S. Kimura, H. Koura, H. Miyatake, K. Morimoto, K. Morita, 5 A. Ozawa, M. Reponen, T. Sonoda, T. Tanaka, 5 and H. Wollnik Institute of Physics, University of Tsukuba, Ibaraki 305-8571, Japan RIKEN Nishina Center for Accelerator-Based Science, Wako, Saitama 351-0198, Japan Institute of Particle and Nuclear Studies (IPNS), High Energy Accelerator Research Organization (KEK), Ibaraki 305-0801, Japan Advanced Science Research Center, Japan Atomic Energy Agency, Ibaraki 319-1195, Japan Kyushu University, Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan New Mexico State University, Las Cruces, NM 88001, USA (Dated: November 15, 2017)

First Direct Mass Measurements of Nuclides around Z=100 with a Multireflection Time-of-Flight Mass Spectrograph

The masses of ^{246}Es, ^{251}Fm, and the transfermium nuclei ^{249-252}Md and ^{254}No, produced by hot- and cold-fusion reactions, in the vicinity of the deformed N=152 neutron shell closure, have been directly measured using a multireflection time-of-flight mass spectrograph. The masses of ^{246}Es and ^{249,250,252}Md were measured for the first time. Using the masses of ^{249,250}Md as anchor points for α decay chains, the masses of heavier nuclei, up to ^{261}Bh and ^{266}Mt, were determined. These new masses were compared with theoretical global mass models and demonstrated to be in good agreement with macroscopic-microscopic models in this region. The empirical shell gap parameter δ_{2n} derived from three isotopic masses was updated with the new masses and corroborates the existence of the deformed N=152 neutron shell closure for Md and Lr.

New mass anchor points for neutron-deficient heavy nuclei from direct mass measurements of radium and actinium isotopes

The masses of the exotic isotopes Ac210−214 and Ra210−214 have been measured with a multireflection time-of-flight mass spectrograph. These isotopes were obtained in flight as fusion-evaporation products behind the gas-filled recoil ion separator GARIS-II at RIKEN. The new direct mass measurements serve as an independent and direct benchmark for existing α-γ spectroscopy data in this mass region. Further, new mass anchor points are set for U and Np nuclei close to the N=126 shell closure for a future benchmark of the Z=92 subshell for neutron-deficient heavy isotopes. Our mass results are in general in good agreement with the previously indirectly determined mass values. Together with the measurement data, reasons for possible mass ambiguities from decay-data links between ground states are discussed.

Universal Slow RI-Beam Facility at RIKEN RIBF for Laser Spectroscopy of Short-Lived Nuclei

A universal slow RI‐beam facility (SLOWRI) for precision atomic spectroscopy is being built at the RIKEN RI‐beam factory. The facility will provide a wide variety of low‐energy nuclear ions of all elements produced by projectile fragmentation of high‐energy heavy‐ion beams and thermalized by an RF‐carpet ion guide. At prototype SLOWRI, radioactive Be isotope ions produced at 1 GeV were decelerated and cooled in an ion trap down to 1 μeV by employing laser cooling. The ground state hyperfine structures of 7Be+ and 11Be+ were measured accurately by laser microwave double resonance spectroscopy. Measurements of the S1/2→P1/2, P3/2 transition frequencies of 7,9,10,11Be+ ions are also in progress aiming at the study of the nuclear charge radii. Other possible experiment at SLOWRI, such as mass spectroscopy, are also discussed.

Performance of Ion Surfing Rf-carpets for High-Energy RI Beam Gas Catcher

High-energy radioactive isotopes have been used in ion trap-based precision experiments after being stopped in a large gas cell. The stopped ions of these isotopes can be extracted from the large gas cell as a low-energy ion beam. To transport and extract these ions quickly and efficiently, electric fields are required to guide them. In this respect, an rf-carpet (RFC) method utilizing a dc potential gradient is a standard technique. However, such a method is restricted to longer half-life isotopes because of the transport time owing to the upper limit on the dc gradient that can be supported before electric discharges occur in the large gas cell. To study short half-life isotopes, an RFC featuring faster transport is required. Recently, a hybrid technique wherein the dc gradient is replaced by a traveling potential wave was proposed, called ion surfing. Recently, we have demonstrated the transport and extraction of K ions using a circular RFC in 20 mbar of He gas pressure. However, in a practical gas cell, the gas pressure is higher by one order of magnitude. In this study, the transport and extraction of K and Cs ions with the ion surfing method were tested in high pressure He gas using a 100 mm cylinder electrode to create a push electric field Epush and a circular RFC of 80 mm diameter. In addition, we compared the effect of an RFC of a fine pitch with one of a rough pitch. The fine pitch RFC consists of 0.08 mm wide ring electrodes with 0.16 mm pitch and 0.32 mm diameter orifice, whereas the rough pitch RFC consists of 0.16 mm wide ring electrodes with 0.32 mm pitch and 0.64 mm diameter orifice.

rp Process and Masses of N{approx_equal}Z{approx_equal}34 Nuclides

High-precision Penning-trap mass measurements of the

Precision hyperfine structure spectroscopy of Be isotopes at SLOWRI prototype and prospects of SLOWRI at RIKEN

N\ensuremath{\approx}Z\ensuremath{\approx}34