602 research outputs found
Fragmentation of exotic oxygen isotopes
Abrasion-ablation models and the empirical EPAX parametrization of projectile fragmentation are described. Their cross section predictions are compared to recent data of the fragmentation of secondary beams of neutron-rich, unstable 19,20,21O isotopes at beam energies near 600 MeV/nucleon as well as data for stable 17,18O beams
From direct to absolute mass measurements: a study of the accuracy of ISOLTRAP
For a detailed study of the accuracy of the Penning trap mass spectrometer ISOLTRAP all expected sources of uncertainty were investigated with respect to their contributions to the uncertainty of the final result. In the course of these investigations, cross-reference measurements with singly charged carbon clusters C were carried out. The carbon cluster ions were produced by use of laser-induced desorption, fragmentation, and ionization of C fullerenes and injected into and stored in the Penning trap system. The comparison of the cyclotron frequencies of different carbon clusters has provided detailed insight into the residual systematic uncertainty of \acro{ISOLTRAP} and yielded a value of . This also represents the current limit of mass accuracy of the apparatus. Since the unified atomic mass unit is defined as 1/12 of the mass of the C atom, it will be possible to carry out absolute mass measurements with \acro{ISOLTRAP} in the future.\\[1\baselineskip] PACS: 07.75.+h (Mass spectrometers and related techniques), 21.10.Dr (Binding energies and masses), 32.10.Bi (Atomic masses, mass spectra, abundances, and isotopes), 36.40.Wa (Charged clusters)
On a cryogenic noble gas ion catcher
In-situ purification of the gas used as stopping medium in a noble gas ion
catcher by operating the device at low temperatures of 60 to 150 K was
investigated. Alpha-decay recoil ions from a 223Ra source served as energetic
probes. The combined ion survival and transport efficiencies for 219Rn ions
saturated below about 90 K, reaching 28.7(17) % in helium, 22.1(13) % in neon,
and 17.0(10) % in argon. These values may well reflect the charge exchange and
stripping cross sections during the slowing down of the ions, and thus
represent a fundamental upper limit for the efficiency of noble gas ion catcher
devices. We suggest the cryogenic noble gas ion catcher as a technically
simpler alternative to the ultra-high purity noble gas ion catcher operating at
room temperature.Comment: Submitted to Nucl. Instrum. Meth. Phys. Res.
Pion emission in 2H, 12C, 27Al, gamma pi+ reactions at threshold
The first data from MAX-lab in Lund, Sweden on pion production in
photonuclear reactions at threshold energies, is presented. The decrease of the
total yield of pi+ in gamma + 12C, 27Al reactions below 200 MeV as well as
differential, dsigma/dOmega, cross sections follow essentially predictions from
an intranuclear cascade model with an attractive potential for pion-nucleus
interaction in its simplest form. Double differential, d2sigma/dOmegadT, cross
sections at 176 MeV show, however, deviations from the model, which call for
refinements of nuclear and Coulomb potentials and possibly also for coherent
pion production mechanisms.Comment: 19 pages, 7 figure
Measurement of nuclide cross-sections of spallation residues in 1 A GeV 238U + proton collisions
The production of heavy nuclides from the spallation-evaporation reaction of
238U induced by 1 GeV protons was studied in inverse kinematics. The
evaporation residues from tungsten to uranium were identified in-flight in mass
and atomic number. Their production cross-sections and their momentum
distributions were determined. The data are compared with empirical
systematics. A comparison with previous results from the spallation of 208Pb
and 197Au reveals the strong influence of fission in the spallation of 238U.Comment: 20 pages, 10 figures, background information at
http://www-wnt.gsi.de/kschmidt
Direct mass measurements beyond the proton drip-line
First on-line mass measurements were performed at the SHIPTRAP Penning trap
mass spectrometer. The masses of 18 neutron-deficient isotopes in the
terbium-to-thulium region produced in fusion-evaporation reactions were
determined with relative uncertainties of about , nine of them
for the first time. Four nuclides (Ho and Tm) were
found to be proton-unbound. The implication of the results on the location of
the proton drip-line is discussed by analyzing the one-proton separation
energies
Strong suppression of nuclear-charge changing interactions for 18 TeV/ c In ions channeled through a bent Si crystal
Abstract We present experimental results giving evidence for the strong reduction—a factor of more than 20—of nuclear-charge changing interactions for 18 TeV In 49+ ions channeled through a silicon crystal bent to 7.5, 11.9 and 19.8 mrad. A very small fraction of the deflected ions suffer electromagnetic or nuclear interactions leading to proton loss while traversing the 60 mm long crystal, even though its thickness corresponds to about 0.13 nuclear interaction lengths for an amorphous material. By considering the deflected ions only, we show experimentally that the nuclear-charge pickup reaction believed to be induced by virtual photons is a short-range phenomenon
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