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GSI-Nachrichten 03-1999
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Spectacular news about new elements
In the past 12 months spectacular news was reported
from the Joint Institute for Nuclear Research in Dubna and from the Lawrence Berkeley
Laboratory in Berkeley. At the end of 1998, Dubna announced the production of isotope
289-114 after bombarding a plutonium-244 target with a calcium-48 beam. It was only a
few months later that additional information was released on the synthesis of the
neighbouring isotope 287-114, which is lighter by two neutrons. Even more spectacular
was the news from Berkeley at the end of May. There, after directing a krypton-86 beam
onto lead-208, three decay chains were observed which were attributed to the production
of element 293-118. If confirmed, these results would imply a revolutionary progress in
heavy element research.
More...
Decay chains of the elements 110, 111, and 112 produced at GSI together with
the new data from Dubna and Berkeley. The Dubna and Berkeley chains end in a hitherto
unknown region of the nuclear chart. Thus, they do not allow an unambiguous identification
of the newly produced isotopes. The colours indicate: yellow = a-decay, red = b-decay,
green = fission, white = decay mode unknown.
Like a string of beads
Highly charged ions circulating in storage rings
have opened up new and previously unimaginable perspectives in atomic and nuclear physics.
Examples are the precision spectroscopy of hydrogen-like heavy ions, as well as the mass
measurements and the investigations into the decay properties of radioactive nuclides,
which belong to the highlights of recent research at the Experimental Storage Ring (ESR).
Another interesting phenomenon has recently been observed at the ESR: the transition of
cooled ion beams to a Coulomb-ordered state. In this state, the ions circulate like a
string of beads without the possibility of passing each other.
More...
Electron cooler in the Experimental Storage Ring (ESR). For very low
particle numbers, a transition of the cooled ion beams to a Coulomb-ordered state was
observed.
Tumour therapy
In December 1997, the first two patients were
treated at GSI with a carbon-ion beam. Following these pilot irradiations, a clinical study
started in August 1998. The aim of this clinical study is to demonstrate the superiority
compared to conventional photon irradiation of ion beam therapy for selected indications.
More...
New QED tests
A major focus in the atomic physics program of GSI
is on precision tests of quantum electrodynamics (QED) in strong electric and magnetic
fields. So far, these experiments concentrated on measurements of binding energies and
transition energies in highly charged heavy ions, as well as on laser spectroscopy of the
hyperfine structure in heavy systems. The determination of the electronic g-factor in
hydrogen-like ions provides a complementary method of probing QED in strong electromagnetic
fields.
More...
Set-up of the Penning-trap experiment. An electron beam in the interior of
the gold-plated copper cylinder produces hydrogen-like C5+ ions via collisional ionisation.
With the electron beam switched off again, all charged particles are then removed except
for the single C5+ ion needed for the measurement. To determine the g-factor, the C5+ ion
is stored in the Penning-trap located in the center of the copper cylinder (see lower
three ring electrodes). The experiment was performed in collaboration with the University
of Mainz.
CERES measures lepton pairs
For the investigation of relativistic heavy-ion
collisions, GSI takes part in two experiments at the CERN Super Proton Synchrotron
(SPS)‹CERES /NA45 and NA49. The CERES/NA45 experiment investigates dielectrons in the
region of low invariant masses. In and below the mass region of the ρ-meson the dilepton
rates in intermediate-mass and heavy systems are enhanced compared to the expectation
from hadronic decays, whereas no deviations are found for proton-induced reactions. A
possible origin is the change of the properties of the vector mesons ρ and ω in hot and
dense matter connected with a restoration of chiral symmetry. Mass resolution and
statistics of the experiment have been further improved to clarify the origin of the
medium modification of the vector mesons.
More...
Dilepton spectra for Pb-Au reactions. The enhancement factor deduced from
the 1996 data is slightly lower compared to the 1995 run. At the same time the statistical
and systematic errors are reduced with respect to the previous measurement.
Short intense ion bunches for plasma research
When short intense pulses of heavy ions are directed
on a target, the target material is heated up and converted to a dense plasma. The
investigation of this extreme state of matter is the subject of the plasma physics group
at GSI.
More...
Compressor cavity developed at GSI. The blue rings indicate the
soft-magnetic metal tapes (VITROVAC), which are used as inductive load. Due to the high
saturation field strength of this material, the required rf voltage of some 40 kV can be
obtained. At the same time, the rf power losses are minimised. Employing six of these
cavities, the total rf voltage of 240 kV needed to compress the bunches to a length of
50 ns will be provided.
Inertial confinement fusion with heavy-ion beams
Accelerators have the potential to contribute to in
the enormously growing energy market of the 21st century, if inertial confinement fusion
can be shown to be competitive with fossil and other nuclear alternatives. It is expected
that ignition of fusion targets and energy gain will be demonstrated within the next
decade by the powerful laser facilities now under construction at Livermore and Bordeaux.
The development of a suitable driver with high efficiency and high repetition rate
capability, however, remains a challenging issue. At present, heavy- ion accelerators are
considered to be the most promising option for such an inertial fusion driver. In this
context, GSI initiated a Study Group to investigate, on an advanced level, the feasibility
for a Heavy Ion Driver for Inertial Fusion (HIDIF) in 1995. This collaboration of research
groups in France, Germany, Italy, Russia, Spain, the UK, the United States, and at CERN
published a comprehensive report at the end of 1998.
More...
HIDIF scenario for an ignition facility, consisting of a rf linac, two
stacks of 3 (or 6) storage rings, and induction bunch compressors for final focusing
onto the target. The linac delivers bismuth ions with an energy of 10 GeV that fill the
storage rings to accumulate the total beam energy of 3 MJ. After extraction, the ion
bunches are synchronised, compressed and then focused onto the target.
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