Search results for "IONIZATION"
showing 10 items of 1255 documents
Isothermal flow of helium II through plane slits
1972
Measurements are reported on the isothermal, gravitational flow of liquid He II through narrow plane slits. The employed superleak consists of ring-shaped Hostaphan foils packed in layers. The distance between the foils is varied by pressure. The performance of the measurements and the observance of the isothermal conditions are described. The velocity of the superfluid component of He II is calculated in dependence on the width of the slits, the temperature and the hydrostatic pressure. Especially the critical velocity is considered.
Direct Ionization Impact on Accelerator Mixed-Field Soft-Error Rate
2020
We investigate, through measurements and simulations, the possible direct ionization impact on the accelerator soft-error rate (SER), not considered in standard qualification approaches. Results show that, for a broad variety of state-of-the-art commercial components considered in the 65-16-nm technological range, indirect ionization is still expected to dominate the overall SER in the accelerator mixed-field. However, the derived critical charges of the most sensitive parts, corresponding to ~0.7 fC, are expected to be at the limit of rapid direct ionization dominance and soft-error increase.
A highly-segmented ΔE-time-of-flight wall as forward detector of the 4π-system for charged particles at the SIS/ESR accelerator
1993
Abstract At the SIS/ESR accelerator facility at GSI in Darmstadt the 4π-detector system FOPI is under construction at present. It is designed for the investigation of central collisions of heavy ions in the energy range up to 2 A GeV. As phase I of this detector a forward wall has been built and used in various experiments. It comprizes a total number of 764 scintillators with an additional shell of 188 thin ΔE -detectors in front of it and covers the full azimuth of the polar angles from 1° to 30°. The velocity and the nuclear charge of the fragments are determined by a combined time-of-flight and ΔE measurement.
A heavy-ion identification system for the detection of rare events
1990
Abstract A large area detection system is described which consists of twelve low-pressure multi-wire proportional counters and is used in the search for exotic super-massive nuclei. The experiments are based on Rutherford backscattering of heavy ions, preferably 208Pb or 238U, from various target samples. The measured parameters of a detected particle are its time-of-flight, scattering angle, and specific ionization. From this information the mass of the target nucleus can be inferred. The present experimental sensitivity for the detection of exotic nuclei with at least twice the mass of the projectile is about 10−12 relative to the number of nucleons.
Observation of a dramatic hindrance of the nuclear decay of isomeric states for fully ionized atoms
2003
Abstract The half-lives of isomeric states of fully ionized 144Tb, 149Dy and 151Er have been measured. These nuclides were produced via fragmentation of about 900 MeV/u 209Bi projectiles, separated in flight with the fragment separator (FRS) and stored in the cooler ring (ESR). The decay times of the cooled fragments have been measured with time-resolved Schottky spectrometry. We observed for the first time drastic increases of the half-lives of bare isomers by factors of up to 30 compared to their neutral counterparts. This is due to the exclusion of the strong internal conversion and electron-capture channels in the radioactive decay of these bare nuclei. The experimental results are in g…
Cubic boron nitride: A new prospective material for ultracold neutron application
2009
Abstract At the ultracold neutron (UCN) source of the TRIGA research reactor in Mainz, we have measured for the first time the material optical wall-potential of cubic boron nitride. The measurements were performed with a time-of-flight (TOF) spectrometer. The samples investigated had a wall-potential of ( 305 ± 15 ) neV . This value is in good agreement with the result extracted from neutron reflectometry data and theoretical expectations. Because of its high critical velocity for UCN and its good dielectric characteristics, cubic boron nitride coatings (isotopically enriched) will be useful for a number of applications in UCN experiments.
Model independent determination of the spin of theTa180naturally occurring isomer
2006
The hyperfine structures of the 33715.27 ${\mathrm{cm}}^{\ensuremath{-}1}$ and 33706.47 ${\mathrm{cm}}^{\ensuremath{-}1}$ transitions from the ground state of singly ionized Ta have been measured by collinear laser spectroscopy. The structures were found to contain a large second order contribution. From fitting the observed hyperfine components for both $^{181}\mathrm{Ta}$ and the $^{180}\mathrm{Ta}$ naturally occurring isomer it was possible to determine the first and second order hyperfine structure coefficients. As no model independent determination of the nuclear spin of the $^{180}\mathrm{Ta}$ isomer has been performed, fitting was attempted for a range of spins. A clear chi-squared m…
$\beta$ - decay of the M$_{T}$=-1 nucleus $^{58}$Zn studied by selective laser ionization
1998
$\beta$ - decay of $^{58}$Zn has been studied for the first time. A new laser ion-source concept has been used to produce mass-separated sources for $\beta$ and $\gamma$ - spectroscopy. The half-life of $^{58}$Zn was determined to be 86(18) ms. Comparisons are made with previous data from charge-exchange reactions. Our Gamow-Teller strength to the 1$^{+}$ state at 1051 keV excitation in $^{58}$Cu agrees well with the value extracted from a recent ($^{3}$He, t) study. Extensive shell-model calculations are presented.
High resolution spectroscopy of rydberg states in indium I
1985
Two-photon laser spectroscopy in a dense indium vapour allowed to investigatenp2P1/2, 3/2 states (n=27–35) for113, 115In with a thermionic diode. Precise data on the fine structure splitting of these states and the isotope shift of the two photon transitions have been obtained. The fine structure splitting shows a hydrogenic behaviour. By using the result of our isotope shift measurement in combination with literature values, level isotope shifts with reference to the ionization limit are deduced and analysed with respect to the different contributions.
Breakdown transient study of plasma distributions in a 2.45 GHz hydrogen discharge
2015
Plasma distribution transients associated with the breakdown of a 2.45 GHz hydrogen discharge similar to high current microwave ion sources are studied by means of an ultra-fast frame image acquisition system in visible light range. Eight different plasma distributions have been studied by photographing the 2D projections of the discharge through a transparent plasma electrode. The temporal evolution of images in Balmer-alpha and Fulcher band wavelengths have been recorded associated to atomic and molecular excitation and ionization processes. Some unexpected plasma distributions transient behaviors during breakdown are reported.