Discovery of a nuclear isomer in 65Fe with penning trap mass spectrometry

A new long-lived isomeric state in (65)Fe has been discovered with Penning trap mass spectrometry and high-precision mass measurements of the neutron-rich isotopes (63-65)Fe and (64-66)Co have been performed with the Low-Energy Beam and Ion Trap Facility at the NSCL. For the new isomer in (65)Fe an excitation energy of 402(5) keV has been determined from the measured mass difference between the isomeric and ground states. The mass uncertainties of all isotopes have been reduced by a factor of 10-100 compared to previous results. In the case of (64)Co the previous mass value was found to deviate by about 5 standard deviations from the new measurement.     

ISOLTRAP: A tandem penning trap mass spectrometer for radioactive isotopes

The masses of over sixty short-lived Rb, Sr, Cs, Ba, Fr and Ra isotopes have been measured at the on-line mass separator ISOLDE at CERN/Geneva by determination of their cyclotron frequency in the tandem Penning trap system ISOLTRAP. Resolving powers exceedingm/m(FWHM)=10⁶ and accuracies of typically m/m=10^–7 could be achieved. ISOLTRAP can also act as an isomer separator, as proven for the cases of⁸⁴Rb and⁷⁸Rb.     

Polarization and trapping of weakly bound atoms in penning trap fields

The ATHENA and ATRAP groups at CERN recently reported the production of weakly bound antihydrogen atoms in a non-neutral positron-antiproton plasma. This Letter derives an equation of motion for weakly bound atoms in the electric and magnetic fields of the plasma and trap. The atoms are polarized by the electric field and can be trapped radially in the edge region of the plasma where the electric field is maximum.     

Recent high-precision Penning trap mass measurements performed at LEBIT

Collected here are all publications related to high-precision Penning trap mass measurements performed at LEBIT which were published from 2007 to 2009.     

Penning trap mass spectrometry for nuclear structure studies

High-precision mass measurements as performed at the Penning trap mass spectrometer ISOLTRAP at ISOLDE/CERN are an important contribution to the investigation of nuclear structure. Precise nuclear masses with less than 0.1 ppm relative mass uncertainty allow stringent tests of mass models and formulae that are used to predict mass values of nuclides far from the valley of stability. Furthermore, an investigation of nuclear structure effects like shell or sub-shell closures, deformations, and halos is possible. In addition to a sophisticated experimental setup for precise mass measurements, a radioactive ion-beam facility that delivers a large variety of short-lived nuclides with sufficient yield is required. An overview of the results from the mass spectrometer ISOLTRAP is given and its limits and possibilities are described.      

The method of separated optical fields for two-level atoms

The paper investigates the observation of coherent radiation in separated fields for the case of two-level atoms. The coherent radiation is due to polarization transfer at large distances. The Doppler phase angle is cancelled due to a phase jump at the nonlinear interaction of the fields with the atoms. A peak in intensity with a width inversely proportion to the flight time arises at the line center. The paper was reported at the 5th Vavilov Conference on Nonlinear Optics, Novosibirsk, USSR (June 1977).     

Penning阱存储离子的灵敏探测

对Ｐｅｎｎｉｎｇ阱中存储离子的探测原理和技术进行了研究,得到了较高探测灵敏度和较高信器比的Ｈ＋ｎ（ｎ＝１,２,３,４）离子谱,为开展离子与中性气体原子（或分子）碰撞过程等课题的研究创造了条件。     

Octupolar excitation of ion motion in a penning trap

The excitation of the motion of ions in a Penning trap at twice their cyclotron frequency, 2ν _c , by means of an azimuthal octupolar RF field has been studied with the LEBIT facility at the NSCL. The possibility of such an RF octupolar excitation has been verified. Compared to ion excitation at ν _c by means of quadrupolar fields an increased resolving power is observed in the cyclotron resonance curves, which may have important implications for Penning trap mass measurements. Numerical simulations have been used to characterize important properties of this type of excitation in detail and to predict the behavior of the ion motion under realistic conditions. Good agreement with the experimental results is observed.      

Observation of Ramsey resonance absorption in three separated laser fields produced by a corner reflector

Experimental observation of optical Ramsey interference in saturated absorption of methane in a low-pressure gas cell with three spacially separated laser beams at 3.39 μm is reported.     

Axialization of laser cooled magnesium ions in a penning trap

We report the first demonstration of the axialization of laser cooled ions in a Penning trap. Axialization involves the application of a small radial quadrupole drive which couples the cyclotron and magnetron motions. This enhances the laser cooling, allowing tighter confinement of the ions to the central axis of the trap than is otherwise possible. Using an intensified charge-coupled device (ICCD) camera we have imaged the axialization process for the first time. For a single ion, we recorded a large decrease of the magnetron amplitude corresponding to a reduction in ion temperature of approximately 2 orders of magnitude to an upper limit of order 10 mK. We have discovered dynamics specific to the laser cooled system which depend critically on the axial drive frequency and amplitude.     

Dynamics of a charged particle bunch in a penning trap

The Lagrangean equations for gas dynamics of a spherical bunch of charged particles in a Penning trap are solved. The solution describes the pulsation of an inhomogeneous particle bunch whose center behaves as a spatial oscillator in a coordinate system rotating with the Larmor frequency.     

Penning阱存储离子的高分辨分析

根据Penning阱中存储和探测离子的原理,研究改善离子谱分辨率的有效措施,发现离子谱的分辨率与LC振荡回路的Q值、阱中离子的密度及LC回路的谐振频率等因素有关.实验中,谐振频率为480千赫兹,Q在120左右,电子束流在40微安左右,真空度合适时,得到了较高分辨率的离子谱.最后对离子谱进行了辨认,离子分别是H+3,H+5,H+6,H+7.     

ISOLTRAP: An on-line Penning trap for mass spectrometry on short-lived nuclides

ISOLTRAP is a Penning trap mass spectrometer for high-precision mass measurements on short-lived nuclides installed at the on-line isotope separator ISOLDE at CERN. The masses of close to 300 radionuclides have been determined up to now. The applicability of Penning trap mass spectrometry to mass measurements of exotic nuclei has been extended considerably at ISOLTRAP by improving and developing this double Penning trap mass spectrometer over the past two decades. The accurate determination of nuclear binding energies far from stability includes nuclei that are produced at rates less than 100 ions/s and with half-lives well below 100ms. The mass-resolving power reaches 10⁷ corresponding to 10keV for medium heavy nuclei and the uncertainty of the resulting mass values has been pushed down to below 10^-8. The article describes technical developments achieved since 1996 and the present performance of ISOLTRAP.     

Recent developments in ion detection techniques for Penning trap mass spectrometry at TRIGA-TRAP

The highest precision in the determination of nuclear and atomic masses can be achieved by Penning trap mass spectrometry. The mass value is obtained through a measurement of the cyclotron frequency of the stored charged particle. Two different approaches are used at the Penning trap mass spectrometer TRIGA-TRAP for the mass determination: the destructive Time-Of-Flight Ion Cyclotron Resonance (TOF-ICR) technique and the non-destructive Fourier Transform Ion Cyclotron Resonance (FT-ICR) method. New developments for both techniques are described, which will improve the detection efficiency and the suppression of contaminations in the case of TOF-ICR. The FT-ICR detection systems will allow for the investigation of an incoming ion bunch from a radioactive-beam facility on the one hand, and for the detection of a single singly charged ion in the Penning trap on the other hand.     

Optimization of a quadrupole ion storage trap as a source for time-of-flight mass spectrometry

Designs of a quadrupole ion trap (QIT) as a source for time-of-flight (TOF) mass spectrometry are evaluated for mass resolution, ion trapping, and laser activation of trapped ions. Comparisons are made with the standard hyperbolic electrode ion trap geometry for TOF mass analysis in both linear and reflectron modes. A parallel-plate design for the QIT is found to give significantly improved TOF mass spectrometer performance. Effects of ion temperature, trapped ion cloud size, mass, and extraction field on mass resolution are investigated in detail by simulation of the TOF peak profiles. Mass resolution (m/Δm) values of several thousand are predicted even at room temperature with moderate extraction fields for the optimized design. The optimized design also allows larger radial ion collection size compared with the hyperbolic ion trap, without compromising the mass resolution. The proposed design of the QIT also improves the ion-laser interaction volume and photon collection efficiency for fluorescence measurements on trapped ions.     

Technical developments for an upgrade of the LEBIT Penning trap mass spectrometry facility for rare isotopes

The LEBIT (Low Energy Beam and Ion Trap) facility is the only Penning trap mass spectrometry (PTMS) facility to utilize rare isotopes produced via fast-beam fragmentation. This technique allows access to practically all elements lighter than uranium, and in particular enables the production of isotopes that are not available or that are difficult to obtain at isotope separation on-line facilities. The preparation of the high-energy rare-isotope beam produced by projectile fragmentation for low-energy PTMS experiments is achieved by gas stopping to slow down and thermalize the fast-beam ions, along with an rf quadrupole cooler and buncher and rf quadrupole ion guides to deliver the beam to the Penning trap. During its first phase of operation LEBIT has been very successful, and new developments are now underway to access rare isotopes even farther from stability, which requires dealing with extremely short lifetimes and low production rates. These developments aim at increasing delivery efficiency, minimizing delivery and measurement time, and maximizing use of available beam time. They include an upgrade to the gas-stopping station, active magnetic field monitoring and stabilization by employing a miniature Penning trap as a magnetometer, the use of stored waveform inverse Fourier transform (SWIFT) to most effectively remove unwanted ions, and charge breeding.     

Penning阱离子谱中奇异峰分析

本文报道Penning离子阱中离子谱出现的奇异峰,提出鉴别它的方法,分析其产生的原因和消除它的可能性,还利用该机制设计出具有高分辨率的探测存储离子的新方法.