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GSI-Nachrichten 03-1997
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IUPAC Announces the Names for the Heaviest Elements
GSI Proposals for Elements 107 to 109 Finally Accepted
Traditionally the discoverer of a new chemical element is also allowed to name it. However,
for the very heavy, artificially produced elements above atomic number 100 there was some
discussion about the priority of the discoveries, in particular between research groups at
Berkeley, California and Dubna near Moscow. In some instances, this led to the existence of
different names proposed for the same element.
From 1986 to 1992 an international working group - the Transfermium Working Group -
whose aim was to find generally accepted names for the elements with atomic numbers 101 to
109, addressed the question of priority. This was done on behalf of the International
Unions for Pure and Applied Chemistry and Physics (IUPAC and IUPAP).
After a critical evaluation of the element discoveries of the past 30 years, the
Transfermium Working Group declared the GSI researchers around Peter Armbruster,
Gottfried Münzenberg, and Sigurd Hofmann unequivocally the discoverers of the elements
with atomic numbers 107, 108, and 109, which were first detected in the years 1981 to
1984. Following this, in September 1992, the GSI scientists submitted their proposal
for the names of these elements to IUPAC.
More...
View into the Wideroe Section of the UNILAC
Identification of Heavy Ions using a Cherenkov Detector
The usage of Cherenkov detectors allows a very
efficient identification of radioactive nuclei at the fragment separator of GSI. This
new method was developed at the TU Munich, and recently successfully tested. The fragment
separator at the GSI uses the projectile fragmentation method with great success to produce
short lived radioactive nuclei and supply them as a secondary beam to other experiments.
More...
The figure shows a typical ring shaped intensity distribution of the light
which is produced by a single fragment as it traverses the radiator in the RICH
detector.
The Production of Intense Beam
Pulses in the SIS Enables New Advances in Plasma Physics
Hydrodynamic Expansion Observed for a Lead Target
Accelerator physicists at GSI have recently tested a new synchrotron acceleration mode
which opens up much-improved opportunities for plasma physics experiments. Using this
mode, the ion bunches, accelerated in the SIS, were transformed into an even more intense
pulse with a pulse length of roughly 250 nanoseconds.
After firing these ion packets at thin lead targets, hydrodynamic expansion was observed
in a metal target for the first time. Temperatures of several thousand Kelvin and pressures
of some hundred kilobars were reached inside the lead plates, representing an increase of
almost an order of magnitude in comparison to previous experiments.
In combination with the high intensity programme the new technique will allow target
temperatures of more than a hundred thousand Kelvin and pressures of a megabar to be
reached.
More...
The first target experiment with a single ion pulse at 300 MeV/u beam
energy. The schematic arrangement of the experiment, the hydrodynamic expansion of the
lead target after 32 microseconds and the pulse profile of the ion beam at the target,
as measured with a fast beam transformer, are shown.
Heavy Ions in Laser Light
Test Stand for Quantum Electrodynamics in Strong Fields
Over the last few years, storage rings such as GSI's ESR Experimental Storage Ring have
provided a large number of completely new experimental possibilities. One of these is
laser spectroscopy of heavy ions circulating at high velocities in the storage ring.
In experiments of this kind, the narrow-band nature of the laser light allows extremely
precise spectroscopy. In many cases, the high ion velocity simplifies the application
of the laser. Analogous to the perception of a car driver driving past a sound source,
who hears the sound shifted to a higher frequency as he approaches, and to a lower
frequency as he speeds away, the absorption of the light is effectively shifted to a
shorter or a longer wavelength.
In the ESR, this Doppler shift is so large that visible light shone with or against
the direction of the ion beam appears as infrared or ultraviolet light, respectively.
In conjunction with the electron cooler, which produces the required beam quality in
the circulating beam, it is possible to exploit the entire potential of laser spectroscopy
with regard to rapidly moving ions in the ESR.
One area of particular interest is precision spectroscopy of hyperfine structure
splitting in hydrogen-like heavy ions. For the first time, these measurements permit
Quantum Electrodynamics (QED), the quantum theory of the electromagnetic interaction,
to be tested in the region of extremely strong electric and magnetic fields - a region
which can only be reached with highly-charged heavy ions.
More...
A glimpse inside the ESR laser laboratory: for the excitation of the
hyperfine transition in hydrogen-like 207Pb81+ the green light of a frequency-doubled
Nd:YAG laser was shone in the direction of flight of the ions. In this experiment, it
was also possible simultaneously to excite the transition in the other direction. To
accomplish this, the green light of the Nd:YAG laser was converted into a red and an
infrared beam in a so-called optical parametric oscillator (OPO). A narrow-band dye
laser, the red laser beam of which can also be recognized, was used to narrow the laser
line width.
Relativistic Beams of Exotic Nuclei
A Powerful Tool for Nuclear Structure Physics
The production of exotic nuclei beyond the region of nuclei known today, and the study of
their properties have a long tradition at GSI. The best-known examples are the experiments
to synthesize the heaviest elements - those with atomic numbers 107 to 112. Besides the
structure of such exotic nuclei, such investigations also focus on astrophysical
questions such as the stellar nucleo-synthesis.
Since the addition of the SIS heavy ion synchrotron to the GSI facilities, the most
important tool for these experiments has been the fragment separator, where relativistic
beams of exotic nuclei can be produced and separated into isotopically-pure components.
In conjunction with the ESR experimental storage ring and the various experimental
facilities in the target hall, this facility has opened up unique opportunities for
nuclear structure research.
Moreover, these opportunities will be considerably extended in the course of the
present intensity upgrade programme. GSI will thus be able to strengthen its position as
one of the world's leading laboratories as far as the study of radioactive secondary
beams is concerned.
More...
A total of 75 targets of different elements with differing thicknesses
can be installed at the target station at the entrance of the fragment separator. Each of
the cylindrical targets, which have a diameter of two centimeters, can be moved into the
path of the ion beam with millimeter precision using step motor control. If required, the
target holder can also be exchanged by remote control.
Higher Intensities at the Synchrotron
The Prospects for the Coming Years
The increase in intensities at the synchrotron is one of the current priority projects of
GSI. This project is based on a multiple programme, which comprises, apart from new
developments in the field of the ion sources, the implementation of an electron cooler
into the SIS ring and the substitution of the Wideroe section of the UNILAC by new
efficient linear accelerator structures. This was reported in detail in GSI
Nachrichten 6/96.
Ever since, this project has advanced according to schedule. Already at the beginning
of this year, the electron cooler, the major parts of which were manufactured at the
Budker Institute for Nuclear Physics (BINP) at Novosibirsk, was delivered to GSI.
Moreover, many components of the new prestripper section have already been received
and are currently tested.
More...
Electron cooler for the SIS: Preparations are presently made for its
implementation into the synchrotron which is scheduled for the beginning of 1998. The
electron cooler was constructed in collaboration with the Budker-Institute in Novosibirsk.
It will allow both the intensities to be increased and the beam quality to be improved.
The photograph was taken during the field mapping of the magnets, after the cooler had
been assembled for tests in the target hall.
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