36,401 research outputs found
Prediction of the thermal release of transactinide elements (112 ≤ Z ≤ 116) from metals
Metallic catcher foils have been investigated on their thermal release capabilities for future superheavy element studies. These catcher materials shall serve as connection between production and chemical investigation of superheavy elements (SHE) at vacuum conditions. The diffusion constants and activation energies of diffusion have been extrapolated for various catcher materials using an atomic volume based model. Release rates can now be estimated for predefined experimental conditions using the determined diffusion values. The potential release behavior of the volatile SHE Cn (E112), E113, Fl (E114), E115, and Lv (E116) from polycrystalline, metallic foils of Ni, Y, Zr, Nb, Mo, Hf, Ta, and W is predicted. Example calculations showed that Zr is the best suited material in terms of on-line release efficiency and long-term operation stability. If higher temperatures up to 2773K are applicable, tungsten is suggested to be the material of choice for such experiment
Size distribution of sputtered particles from Au nanoislands due to MeV self-ion bombardment
Nanoisland gold films, deposited by vacuum evaporation of gold onto Si(100)
substrates, were irradiated with 1.5 MeV Au ions up to a fluence of
ions cm and at incidence angles up to
with respect to the surface normal. The sputtered particles were collected on
carbon coated grids (catcher grid) during ion irradiation and were analyzed
with transmission electron microscopy and Rutherford backscattering
spectrometry. The average sputtered particle size and the areal coverage are
determined from transmission electron microscopy measurements, whereas the
amount of gold on the substrate is found by Rutherford backscattering
spectrometry. The size distributions of larger particles (number of
atoms/particle, 1,000) show an inverse power-law with an exponent of
-1 in broad agreement with a molecular dynamics simulation of ion impact
on cluster targets.Comment: 13 pages, 8 figures, Submitted for publication in JA
Development of a thermal ionizer as ion catcher
An effective ion catcher is an important part of a radioactive beam facility
that is based on in-flight production. The catcher stops fast radioactive
products and emits them as singly charged slow ions. Current ion catchers are
based on stopping in He and H gas. However, with increasing intensity of
the secondary beam the amount of ion-electron pairs created eventually prevents
the electromagnetic extraction of the radioactive ions from the gas cell. In
contrast, such limitations are not present in thermal ionizers used with the
ISOL production technique. Therefore, at least for alkaline and alkaline earth
elements, a thermal ionizer should then be preferred. An important use of the
TRIP facility will be for precision measurements using atom traps. Atom
trapping is particularly possible for alkaline and alkaline earth isotopes. The
facility can produce up to 10 s of various Na isotopes with the
in-flight method. Therefore, we have built and tested a thermal ionizer. An
overview of the operation, design, construction, and commissioning of the
thermal ionizer for TRIP will be presented along with first results for
Na and Na.Comment: 10 pages, 4 figures, XVth International Conference on Electromagnetic
Isotope Separators and Techniques Related to their Applications (EMIS 2007
Catch Shares in Action: Alaska Halibut and Sablefish Fixed Gear Individual Fishing Quota Program
The Alaska Halibut and Sablefish Fixed Gear Individual Fishing Quota Program (IFQ Program) was one of the first to include a variety of design elements to meet key social goals while also contributing to decreasing overcapitalization and increasing the value of the fishery. Some of the key design elements include low concentration limits, restrictions on trading, strict shareholder eligibility requirements and more. The program also allocates a percentage of the shares to the Community Development Quota (CDQ) program, which includes 65 eligible communities organized into six groups and was designed to ensure fishing access, support economic development, alleviate poverty, and provide economic and social benefits to residents of western Alaska communities (North Pacific Fishery Management Council, n.d, A)
Ultrasonic Planetary Core Drill: Overview and Results from Field Trial
In the effort to explore the subsurface of terrestrial bodies, we seek to obtain better samples from ever greater depths. Many organisations are working towards technologies that can achieve this goal whilst ensuring compatibility with the likely requirements of planetary landers in terms of mass, power, and dimensions.
The Ultrasonic Planetary Core Drill (UPCD) was an FP7 funded project which aimed to develop such a planetary sub-surface sample acquisition system, developing the required drill hardware and testing it in a Mars analogue environment in Antarctica.
The objective was to reach 30cm and containerise the samples using the least possible power, while operating at low weight-on-bit. This has been broadly achieved within a conceptually-deployable package
Performance of the neutron polarimeter NPOL3 for high resolution measurements
We describe the neutron polarimeter NPOL3 for the measurement of polarization
transfer observables with a typical high resolution of 300 keV
at 200 MeV.
The NPOL3 system consists of three planes of neutron detectors.
The first two planes for neutron polarization analysis are made of 20 sets of
one-dimensional position-sensitive plastic scintillation counters with a size
of 100 cm 10 cm 5 cm, and they cover the area of 100
100 .
The last plane for detecting doubly scattered neutrons or recoiled protons is
made of the two-dimensional position-sensitive liquid scintillation counter
with a size of 100 cm 100 cm 10 cm.
The effective analyzing powers and double scattering
efficiencies were measured by using the three kinds
of polarized neutrons from the , , and reactions at = 198 MeV.
The performance of NPOL3 defined as
are similar to that of the
Indiana Neutron POLarimeter (INPOL) by taking into account for the counter
configuration difference between these two neutron polarimeters.Comment: 28 pages, 18 figures, submitted to Nucl. Instrum. Methods Phys. Res.
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