Sessions - DPG-Tagungen

Nuclear Physics Monday
Group Report HK 2.2 Mon 16:15 A
New results from direct mass measurements at GSI — •Yu.A.
Litvinov 1 , H. Geissel 1,2 , M. Matoˇs 1 , Yu.N. Novikov 3 , Z. Patyk 1 ,
T. Radon 1 , C. Scheidenberger 1 , F. Attallah 1 , K. Beckert 1 , P.
Beller 1 , F. Bosch 1 , D. Boutin 1 , T. Buervenich 4 , M. Falch 5 ,
T. Faestermann 6 , B. Franzke 1 , M. Hausmann 4 , E. Kaza 1 , T.
Kerscher 5 , O. Klepper 1 , H.-J. Kluge 1 , C. Kozhuharov 1 , K.-L.
Kratz 7 , S.A. Litvinov 1 , K.E.G. Löbner 5 , G. Münzenberg 1,7 , L.
Maier 6 , F. Nolden 1 , T. Ohtsubo 8 , A. Ostrowski 7 , A. Ozawa 9 , B.
Pfeiffer 7 , M. Portillo 1 , J. Stadlmann 1 , T. Suzuki 8 , M. Steck 1 ,
S. Typel 1 , D. Vieira 4 , H. Weick 1 , M. Winkler 1 , H. Wollnik 2 ,
and T. Yamaguchi 1 — 1 GSI Darmstadt — 2 JLU Giessen — 3 PNPI St.
Petersburg — 4 LANL Los Alamos — 5 LMU München — 6 TU München
— 7 JGU Mainz — 8 Niigata University — 9 RIKEN Saitama
A report will be given on the progress in direct mass measurements
with Isochronous (IMS) and Schottky (SMS) Mass Spectrometry at the
FRS-ESR. The mass surface of rather long-lived (T1/2 ≥ 1 s) neutrondeficient
nuclides, consisting of about 450 nuclei from Kr to At, was
measured with a precision of 30 keV by time-resolved SMS. Using known
decay energies, masses of 140 nuclides could be determined in addition.
114 masses were obtained for the first time. New masses of about 40
short-lived uranium fission fragments were measured by IMS with a precision
of about 250 keV. The measured data give the unique opportunity
to check and to improve modern mass models, to locate the proton and
two-proton drip-lines for heavy isotopes and moreover to perform investigations
of the isospin dependence of nuclear pairing energies.
Group Report HK 2.3 Mon 16:45 A
Absolute mass measurements of exotic nuclides at 10 −8 precision
with ISOLTRAP — •Klaus Blaum for the ISOLTRAP collaboration
— CERN, Division EP, 1211 Geneva 23, Switzerland — GSI,
Planckstraße 1, 64291 Darmstadt, Germany
ISOLTRAP is a Penning trap mass spectrometer installed at
ISOLDE/CERN for on-line mass measurements of short-lived radionuclides.
The precise determination of nuclear binding energies far from
stability includes nuclei that are produced at rates of 100 ions/s and
with half-lives well below 100 ms. The mass resolving power reaches 10 7
and the uncertainty of the resulting mass values has been pushed down
to 1 · 10 −8 [1,2].
A number of scientific highlights have been obtained recently, as e.g.
the mass measurement of 32 Ar (T1/2 = 98ms) and 74 Rb (T1/2 = 65ms).
Both provide important input for fundamental tests of the weak interaction,
for example with regards to the conserved vector current (CVC)
hypothesis and the unitarity of the Cabibbo-Kobayashi-Maskawa (CKM)
matrix. Furthermore, the high resolving power of ISOLTRAP allowed us
to prepare an isomerically pure ion beam. This opens a new field in nuclear
physics at low energies. In combination with the resonant ionization
laser ion source we were able to solve via high-precision mass measurements
the long-outstanding assignment puzzle between the ground state
and the two low-lying isomeric states in 70 Cu. The status of ISOLTRAP
as well as recent results will be presented.
[1] F. Herfurth et al., J. Phys. B 36 (2003) 931.
[2] K. Blaum et al., Nucl. Instrum. Methods 204 (2003) 478.
HK 2.4 Mon 17:15 A
Schottky mass measurements of neutron-rich nuclides between
lead and uranium — •E. Kaza 1 , F. Attallah 1 , K. Beckert 1 ,
P. Beller 1 , F. Bosch 1 , D. Boutin 1 , T. Faestermann 2 , B.
Franczak 1 , B. Franzke 1 , H. Geissel 1,3 , M. Hausmann 4 , M.
Hellstrvm 1 , O. Klepper 1 , H.-J. Kluge 1 , C. Kozhuharov 1 ,
K.-L. Kratz 5 , Yu.A. Litvinov 1 , L. Maier 2 , M. Matoˇs 1 , G.
M—nzenberg 1,5 , F. Nolden 1 , Yu.N. Novikov 6 , A.N. Ostrowski
5 , T. Ohtsubo 7 , A. Ozawa 8 , B. Pfeiffer 5 , M. Portillo 1 ,
C. Scheidenberger 1 , J. Stadlmann 1 , M. Steck 1 , T. Suzuki 7 ,
K. S—mmerer 1 , D. Vieira 4 , H. Weick 1 , M. Winkler 1 , H.
Wollnik 3 , and T. Yamaguchi 1 — 1 GSI Darmstadt — 2 TU M—nchen
— 3 JLU Giessen — 4 LNAL Los Alamos — 5 JGU Mainz — 6 PNPI
St.Petersburg — 7 Niigata University — 8 RIKEN Saitama
Relativistic heavy ions are produced from projectile fragmentation of a
672-690 MeV/u 238 U beam on a 4g/cm 2 Be target and separated according
to their magnetic rigidity in the fragment separator FRS. After being
injected into the experimental storage ring ESR, their velocity spread
is reduced by electron cooling. Thus the mass over charge ratio of the
ions becomes proportional to their revolution frequency which is acquired
with Schottky pick-ups.
Analysing the frequency spectra yields several previously unknown
masses of Th, Ac and Ra isotopes with typically 50 keV precision. Observing
the time evolution of the intensity of the isotopes allows their
halflife estimation, which also confirms their identification.
HK 2.5 Mon 17:30 A
Super-FRS, the Next-Generation Rare Isotope In-flight Facility
at GSI — •M. Winkler for the Super–FRS/NUSTAR collaboration
— GSI Darmstadt
The projectile fragment separator FRS at GSI has successfully contributed
to a broad scientific programme in heavy-ion physics and applications
at relativistic energies. The limitations of the present facility
are the relatively low intensities for primary beams and the low transmission
for rare isotope beams characterized by a large emittance, such
as fission fragments. The planned new international accelerator facility
at GSI [1] will solve these shortcomings. It will provide primary beams
of all projectiles up to uranium accelerated up to 2 GeV/u for nuclear
structure physics. The maximum intensities of these projectiles beams
will be (1-3)×10 12 /s depending on the energy, mass and charge state.
The planned new SUPERconducting projectile FRagment Separator [2],
Super-FRS, is a large acceptance in-flight facility providing spatially separated
rare-isotope beams for several experimental areas:
a) the high-energy branch including a high-resolution spectrometer to
perform reaction studies b) the low-energy branch for spectroscopy with
energy-bunched rare isotope beams c) the ring branch for precision experiments
with stored and cooled beams, including reactions with light
hadrons and electrons.
In this contribution we present the main characteristics of the Super-
FRS including the production target, degrader, and diagnostic systems.
[1] http://www.gsi.de/gsi-future/cdr/
[2] H. Geissel et al, Nucl. Instr. and Meth., B204(2003)71-85
HK 2.6 Mon 17:45 A
Half-life measurements of fully-ionized 207 Tl atoms — •D.
Boutin 1 , L. Maier 2 , T. Yamaguchi 1,3 , F. Bosch 1 , C. Scheidenberger
1 , K. Beckert 1 , P. Beller 1 , T. Faestermann 2 , B.
Franczak 1 , H. Geissel 1,4 , E. Kaza 1 , P. Kienle 2 , O. Klepper 1 , C.
Kozhuharov 1 , Yu.A. Litvinov 1 , M. Matos 1 , G. Münzenberg 1,5 ,
F. Nolden 1 , Yu.N. Novikov 6 , T. Ohtsubo 7 , W. Plass 4 , M. Portillo
1 , V. Shishkin 1 , J. Stadlmann 1 , M. Steck 1 , K. Takahashi 8 ,
H. Weick 1 , and M. Winkler 1 — 1 GSI Darmstadt — 2 TU München
— 3 Saitama University — 4 JLU Giessen — 5 JGU Mainz — 6 PNPI St
Peterburg — 7 Niigata University — 8 MPIK Heidelberg
For the understanding of the nucleosynthesis in stars, radioactive decays
play an important role. However in the stellar medium the extreme
temperatures and pressures lead to the stripping of most of the electrons
from the atoms, which can lead to a dramatic change in their β-decay
probabilities. In particular in highly-ionized atoms the bound-β − channel
opens up .
Half-life measurements of fully-ionized 207 Tl 81+ were performed with
time-resolved Schottky Mass Spectrometry (SMS) at the FRS-ESR facility
in GSI. The acceptance of the Experimental Storage Ring (ESR) allowed
to observe both the continuum-β − decay (to 207 Pb 82+ ) and boundβ
− decay (to 207 Pb 81+ ) of this nuclide, and consequently to evaluate the
partial half-lives and the branching ratios. The isomeric state of fullyionized
207 Tl (T1/2 = 1.33 s for the neutral atom) and its decay to the
ground state could be also observed. The experimental results will be
discussed and compared with theoretical predictions.
HK 2.7 Mon 18:00 A
Exotic nuclei from the Super-FRS studied in the storage rings
of the future international accelerator facility at GSI — •H.
Weick and H. Simon for the EXEL / NUSTAR collaboration — GSI,
Darmstadt
High intensity beams of rare isotopes will be produced, separated inflight
and injected into the new storage ring complex of the future international
accelerator facility at GSI. Precision mass and lifetime measurements
of exotic nuclei can be performed in the CR and NESR storage
rings. Very short-lived nuclei can be investigated without cooling in the
isochronous mode of the CR. Nuclear reactions with the internal target
in the NESR will be used to study the nuclear structure and the dynamic
properties of the stored rare isotopes. A main advantage of such investigations
in storage rings is the possibility to use thin targets without
losing luminosity which allows high resolution measurements and to look
at very low momentum transfer. A new field will be opened up by scattering
experiments of electrons on cooled exotic nuclei in the eA-collider.