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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2010

Active Correlation Technique: Status and Development

During the recent years, at the FLNR (JINR) a successful cycle of experiments has been accomplished on the synthesis of the superheavy elements with Z = 112-118 with {sup 48}Ca beam. From the viewpoint of the detection of rare decays and background suppression, this success was achieved due to the application of a new radical technique--the method of active correlations. The method employs search in a real-time mode for a pointer to a probable correlation like recoil-alpha for switching the beam off. In the case of detection in the same detector strip an additional alpha-decay event, of 'beam OFF' time interval is prolonged automatically.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2010

Observation of new neutron-rich isotopes at the NSCL

Recently, increased primary beam intensities at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University and advances in experimental techniques allowed probing further into unknown regions of the table of the isotopes with fragmentation and in-flight fission reactions. Recent measurements at the NSCL have demonstrated that primary beams of {sup 48}Ca at 141 MeV/u and {sup 76}Ge at 132 MeV/u can be used to produce new isotopes {sup 40}Mg, {sup 42,43}Al, {sup 44}Si, {sup 52}Ar, {sup 50}Cl, {sup 52,53}Ar, {sup 55,56}K, {sup 57,58}Ca, {sup 59,60,61}Sc, {sup 62,63}Ti, {sup 65,66}V, {sup 68}Cr, {sup 70}Mn in the proximity of the neutron dripline. Also, experiments with {sup 238}U(81 MeV/u) and {sup 208}Pb(86 MeV/u) beams in order to measure production yields and possibly observe several neutron rich isotopes in the first time have recently been performed at the NSCL. A search for new neutron-rich isotopes with {sup 48}Ca and {sup 76}Ge beams was carried out using the recently developed two-stage fragment separator technique.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

Note: Effect of hot liner in producing {sup 40,48}Ca beam from RIKEN 18-GHz electron cyclotron resonance ion source

In order to produce a high-intensity and stable {sup 48}Ca beam from the RIKEN 18-GHz electron cyclotron resonance ion source, we have begun testing the production of a calcium beam using a micro-oven. To minimize the consumption rate of the material ({sup 48}Ca), we introduced the “hot liner” method and investigated the effect of the liner on the material consumption rate. The micro-oven was first used to produce the {sup 48}Ca beam for experiments in the RIKEN radioisotope beam factory, and a stable beam could be supplied for a long time with low consumption rate.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2010

New Research Opportunities at RIKEN RI Beam Factory

RIKEN RI Beam Factory (RIBF) is an accelerator complex including the part that has been working for about 20 years. The new facility is dedicated to provide beams of unstable nuclei very far from the stability valley with newly-built high-power driver accelerators. The new part of RIBF has started operation in the end of 2006 after 10 years construction. The new facility of RIBF successively boosts the beam energy up to 345 MeV/nucleon for all chemical elements up to uranium. The first experimental result, production of new neutron-rich isotopes {sup 125}Pd and {sup 126}Pd, was obtained in May 2007 with {sup 238}U beams, followed by a measurement in November 2008 with a improved beam intensity producing about thirty new isotopes. The first secondary reaction experiments have been performed in December 2008 with intense {sup 48}Ca beams. The current capability in producing nuclei far from the stability is exceeding the one of any other facilities in the world, and will even be enhanced to reach the level where about 1000 unknown isotopes can be created. Several new experimental installations are planned or being constructed.

43 PARTICLE ACCELERATORS↗
DOE OSTI2010

Effects of elastic and inelastic NN scattering cross sections on {pi}{sup -}/{pi}{sup +} ratios in heavy-ion collisions at intermediate energies

Based on the isospin-dependent Boltzmann-Uehling-Uhlenbeck transport model and the scaling model according to nucleon effective mass, effects of elastic and inelastic NN scattering cross sections on {pi}{sup -}/{pi}{sup +} in the neutron-rich reaction of {sup 48}Ca+{sup 48}Ca at a beam energy of 400 MeV/nucleon are studied. It is found that cross-section effects of both NN elastic and inelastic scatterings affect {Delta}{sub 1232}, {pi}{sup -} and {pi}{sup +} production, as well as the value of {pi}{sup -}/{pi}{sup +}.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Investigation of low-lying electric dipole strength in the semimagic nucleus {sup 44}Ca

The dipole-strength distribution in the semimagic nucleus {sup 44}Ca has been measured up to 10 MeV excitation energy in photon-scattering experiments using bremsstrahlung and monoenergetic 100% linearly polarized photon beams. The combination of both measurements allows a clear determination of spin and parity quantum numbers of the excited states as well as absolute cross sections and transition probabilities. The results show that the majority of the dipole strength in {sup 44}Ca below 10 MeV is due to E1 transitions while M1 strength plays only a minor role. The experimental results are compared to the strength in the neighboring doubly magic nuclei {sup 40,48}Ca and to microscopic calculations within the extended theory of finite Fermi systems in order to investigate the evolution of the low-lying E1 strength in this isotopic chain. Both, experiment and calculations, show a nontrivial dependence of the total E1 strength as a function of the neutron number.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2010

Penning trap mass measurements on nobelium isotopes

The Penning trap mass spectrometer SHIPTRAP at GSI Darmstadt allows accurate mass measurements of radionuclides, produced in fusion-evaporation reactions and separated by the velocity filter SHIP from the primary beam. Recently, the masses of the three nobelium isotopes {sup 252-254}No were determined. These are the first direct mass measurements of transuranium elements, which provide new anchor points in this region. The heavy nuclides were produced in cold-fusion reactions by irradiating a PbS target with a {sup 48}Ca beam, resulting in production rates of the nuclei of interest of about one atom per second. In combination with data from decay spectroscopy our results are used to perform a new atomic-mass evaluation in this region.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2010

Noncollective aligned and antialigned states in {sup 125}I

High-spin states in {sup 125}I were populated using the reaction {sup 82}Se({sup 48}Ca,p4n) at a beam energy of 200 MeV and {gamma}-ray coincidence events were acquired with the Gammasphere spectrometer. The level scheme of {sup 125}I was extended considerably. In particular, maximally aligned states involving all eleven particles outside the {sup 114}Sn core were observed. Comparison with cranked Nilsson-Strutinsky calculations suggests that three of these states are the final I{sub max} states in terminating bands with all spin vectors aligned along a common axis. In two of these, one spin vector is antialigned and points in the opposite direction. In one of the states two spin vectors are antialigned. This is the first observation of a state with such a structure.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Automation of experiments at Dubna Gas-Filled Recoil Separator

Approaches to solving the problems of automation of basic processes in long-term experiments in heavy ion beams of the Dubna Gas-Filled Recoil Separator (DGFRS) facility are considered. Approaches in the field of spectrometry, both of rare α decays of superheavy nuclei and those for constructing monitoring systems to provide accident-free experiment running with highly radioactive targets and recording basic parameters of experiment, are described. The specific features of Double Side Silicon Strip Detectors (DSSSDs) are considered, special attention is paid to the role of boundary effects of neighboring p–n transitions in the “active correlations” method. An example of an off–beam experiment attempting to observe Zeno effect is briefly considered. Basic examples for nuclear reactions of complete fusion at {sup 48}Ca ion beams of U-400 cyclotron (LNR, JINR) are given. A scenario of development of the “active correlations” method for the case of very high intensity beams of heavy ions at promising accelerators of LNR, JINR, is presented.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

{gamma} spectroscopy around doubly magic {sup 48}Ca by heavy-ion transfer reactions

{gamma} spectroscopy of neutron-rich nuclei around {sup 48}Ca is performed by the heavy-ion transfer reaction {sup 48}Ca on {sup 64}Ni at 282 MeV, with the PRISMA-CLARA setup at Legnaro Laboratory. Angular distributions, polarizations and lifetimes analysis probe spin and parities of several excited states, shading lights on their configuration. In the one neutron transfer channels, {sup 49}Ca and {sup 47}Ca, states arising by coupling a single particle to the 3{sup -} phonon of {sup 48}Ca are observed, showing the robustness of nuclear collectivity in rather light systems. The work demonstrates the feasibility of complete in-beam {gamma}-spectroscopy with heavy-ion transfer reactions and provides a method that can be further exploited in the future with heavy targets and radioactive beams.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Fast optical transport of ultracold molecules over long distances

Abstract Optically trapped laser-cooled polar molecules hold promise for new science and technology in quantum information and quantum simulation. Large numerical aperture optical access and long trap lifetimes are needed for many studies, but these requirements are challenging to achieve in a magneto-optical trap (MOT) vacuum chamber that is connected to a cryogenic buffer gas beam source, as is the case for all molecule laser cooling experiments so far. Long distance transport of molecules greatly eases fulfilling these requirements as molecules are placed into a region separate from the MOT chamber. We realize a fast transport method for ultracold molecules based on an electronically focus-tunable lens combined with an optical lattice. The high transport speed is achieved by the 1D red-detuned optical lattice, which is generated by interference of a focus-tunable laser beam and a focus-fixed laser beam. Efficiency of 48(8)% is realized in the transport of ultracold calcium monofluoride (CaF) molecules over 46 cm distance in 50 ms, with a moderate heating from 32(2) μ K to 53(4) μ K. Positional stability of the molecular cloud allows for stable loading of an optical tweezer array with single molecules.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2014

Operational test of micro-oven for {sup 48}Ca beam

In order to supply a high-intensity and stable {sup 48}Ca beam from the RIKEN 18-GHz electron cyclotron resonance ion source, we are conducting operational tests of a micro-oven. A mixture of CaO and Al powders is placed into the crucible of the micro-oven and heated to produce metallic calcium by a reductive reaction. The successful production of a calcium beam was confirmed. In addition, we reduced the material consumption rate by using a so-called “hot liner,” and we enhanced the beam intensity by applying a negative voltage bias to the micro-oven, the effect of which is similar to the effect of a “biased disk.”.

43 PARTICLE ACCELERATORS↗
DOE OSTI2013

A spectrometer on chemical vapour deposition-diamond basis for the measurement of the charge-state distribution of heavy ions in a laser-generated plasma

This article reports on the development and the first applications of a new spectrometer which enables the precise and time-resolved measurement of both the energy loss and the charge-state distribution of ion beams with 10 < Z < 30 at energies of 4-8 MeV/u after their interaction with a laser-generated plasma. The spectrometer is based on five 20 Multiplication-Sign 7 mm{sup 2} large and 20 {mu}m thick polycrystalline diamond samples produced via the Chemical Vapour Deposition (CVD) process and was designed with the help of ion-optical simulations. First experiments with the spectrometer were successfully carried out at GSI using {sup 48}Ca ions at an energy of 4.8 MeV/u interacting with a carbon plasma generated by the laser irradiation of a thin foil target. Owing to the high rate capability and the short response time of the spectrometer, pulsed ion beams with 10{sup 3}-10{sup 4} ions per bunch at a bunch frequency of 108 MHz could be detected. The temporal evolution of the five main charge states of the calcium ion beams as well as the corresponding energy loss values could be measured simultaneously. Due to the outstanding properties of diamond as a particle detector, a beam energy resolution ({Delta}E/E) Almost-Equal-To 0.1% could be reached using the presented experimental method, while a precision of 10% in the energy loss and charge-state distribution data was obtained.

36 MATERIALS SCIENCE↗
DOE OSTI2010

Production of neutron-rich Ca, Sn, and Xe isotopes in transfer-type reactions with radioactive beams

The production cross sections of neutron-rich isotopes {sup 52,54,56,58,60}Ca, {sup 136,138,140,142}Sn, and {sup 146,148,150,152}Xe are predicted for future experiments in the diffusive multinucleon transfer reactions {sup 86,90,92,94}Kr, {sup 124,130,132,134}Sn, {sup 136,140,142,146}Xe, and {sup 138,144,146}Ba+{sup 48}Ca with stable and radioactive beams at incident energies close to the Coulomb barrier. Because of the small cross sections, the production of neutron-rich isotopes requires the optimal choice of projectile-target combinations and bombarding energies.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2010

Search for the Origin and Limits of Nuclei at the NSCL

The recent production of the most neutron-rich nuclei by the fragmentation of {sup 48}Ca and {sup 76}Ge beams at Michigan State are presented. The cross sections were measured for a large range of nuclei including fifteen new isotopes that are the most neutron-rich nuclides of magnesium, aluminum, silicon, and the elements from chlorine to manganese. The cross sections of several new nuclei were found to be enhanced relative to a simple thermal evaporation framework that was previously shown to describe similar production cross sections. This difference indicates that precursor excited nuclei in the region around {sup 62}Ti that decay to the observed nuclei may be more stable than predicted by current mass models. The enhanced stability may be evidence for a new island of inversion similar to that centered on {sup 31}Na. The NSCL at Michigan State University was recently selected to be the site of the next generation radioactive beam facility, FRIB, for the United States. A brief overview of the proposed facility and some of its capabilities are presented.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Precision lifetime measurements of the first 2{sup +} and 4{sup +} states in {sup 56}Cr at the N=32 subshell closure

Excited states in {sup 56}Cr have been populated after {sup 48}Ca({sup 11}B,p2n) reactions at a beam energy of 32 MeV. The Cologne plunger device surrounded by a {gamma}-detector array of one EUROBALL cluster detector and five Ge detectors was employed to determine lifetimes with the recoil distance Doppler shift method. {gamma}{gamma}-coincidence data were analyzed using the differential decay curve method and precise lifetimes for the first 2{sup +} and 4{sup +} state of {tau}=5.49(14) ps and {tau}=3.15(11) ps, respectively, were extracted. The corresponding B(E2; 2{sup +}{yields}0{sup +})=11.33(31) W.u. quantifies with a high accuracy the puzzling discrepancy between experimental B(E2) values in N=32 isotones and theoretical results from large-scale shell model calculations employing modern effective nucleon-nucleon interactions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Single-particle and collective structures in {sup 55}Cr and {sup 55}V

Excited states in {sup 55}V and {sup 55}Cr have been populated via pn and 2n evaporation channels, respectively, following the fusion of a {sup 48}Ca beam at 172 MeV with a {sup 9}Be target. Level schemes have been deduced for the two nuclides to excitation energies of 7467 ({sup 55}V) and 12226 keV ({sup 55}Cr), with spins of 27/2{sup +} and 33/2{sup +}, respectively. Negative-parity states are compared with shell-model calculations using three different effective interactions in the full fp model space. Negative-parity levels of {sup 55}Cr are explained in terms of single-particle fp-shell configurations outside N=28 and N=32 cores. Positive-parity states in both isotopes show evidence for the involvement of neutron g{sub 9/2} configurations. In the case of {sup 55}Cr, a quasirotational structure based on the 1/2{sup +}[440] Nilsson orbital is observed up to the terminating state. In {sup 55}V, positive-parity states do not exhibit well-developed collective features, and the observation of octupole decays is an indication of their importance in transitions from neutron g{sub 9/2} configurations to the fp shell. Experimental results are compared with the predictions of a traditional shell model, the projected shell model, and total-Routhian-surface calculations.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗