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Erzeugung exotischer Atomkerne
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Der Ursprung der Elemente
Nukleosynthese nach dem Urknall
Kernfusion in Sternen
Neutroneneinfang in Roten Riesensternen oder
Supernovae
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Geburt und Tod der Sterne
Zwiebelschalenstruktur kurz vor Explosion
8M?? M ? 15M? Supernova II 1.4M?? Mcore?
2M? Neutronen Stern
M ??15M? Supernova IIa M ?? 2M? Schwarzes Loch
M ? ?8M? Roten Riese
Weißer Zwerg
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Der Ursprung der Elemente
number of protons
Nucleosynthese in Supernova-Explosionen Schnelle
r Neutroneneinfang durch instabile
(neutronenreiche) Isotope
number of neutrons
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Reaktionsmechanismen zur Erzeugung radioaktiver
Strahlen
Protonen-indizierte Reaktionen
Schwerionen-induzierte Reaktionen
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Fragmentation im Fluge
Ionen-Separation on-line ISOL
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Zwei moderne Methoden zur Erzeugung und
Untersuchung seltener Isotope
Gestoppte und wiederbeschleunigte Ionen Ionen
Separation Online (ISOL)
Fragmentation im Fluge (IF)
Relativistische Schwerionenstrahlen
Intensive Protonenstrahlen
Heißes, dickes Target Targetfragmentation
Dünnes Target Projektilfragmentation
Ionenquelle
ms - s
Fragmentseparator
Massenseparator geringer Auflösung
?s
Ionenkühlung
Speicherring
Ionenfallen
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Konzepte für ISOL
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ISOLDE (CERN)
Strahl aus dem PS Booster Verbund aus 4 kleinen
Synchrotrons liefert 1 GeV Protonen, 3.2?1013/s
(alle 1.2 s)
Some of the targets used at ISOLDE consist of
molten metals kept at temperatures from 700o C
and up to about 1400o C. Such targets are
characterized by a relatively long release time
of the produced isotopes and a typical time
constant of the release is about 30 seconds.
Faster release times, in the order of one second
or less, can be obtained, if target material in
the form of refractory metal powder, metals or
carbides is used at temperatures above 2000o C.
An expected decrease in the release time due to
the "shock-wave" effect of the pulsed proton beam
has been observed. Time constants down to some
tenths of a second can be reached for the fastest
targets.
Oberflächen-Ionenquelle
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ISOLDE at the PS-BOOSTER The basic principle of
ISOLDE is that radioactive nuclides are produced
in spallation, fission or fragmentation reactions
with a thick target placed in the external proton
beam of 1 GeV. To most nuclear and high-energy
physicists, the word "target" evokes the idea of
a passive foil or rod, but here the target is, in
reality, a small chemical factory that, under
intense bombardment, supplies the radioactive
beam, that after magnetic analysis, is steered to
the experiments. The large range in solids of
high-energy protons and also the reactions
induced by secondaries are essential in providing
ISOLDE with intensities that, in general, cannot
be matched by other machines.
The proton injector for ISOLDE, the PS Booster,
is a stack of four small synchrotrons
pre-accelerating protons, delivered by a Linac,
to 1 GeV before injection into the CERN Proton
Synchrotron (PS). PS in turn supplies particles
to all CERN's high-energy machines. The PSB gives
one pulse of 3.21013 protons every 1.2 seconds.
Up to half of the pulses in the 12 pulses long
super cycle to the PS is brought to bombard the
ISOLDE target. This gives an equivalent of about
2 microA dc beam. The transfer of ISOLDE from the
600 MeV dc proton beam at the CERN SC to the time
structure, with a short high density proton pulse
at low repetition rate, increased the release
time of the produced radioactivity from the
target. This increased predominantly the
production of very short-lived species and makes
the ISOLDE beam bunched. In addition it allows
"background free" experiments between the pulses
because the neutrons, which are the main sources
of background, die out in the first 100 ms after
the beam burst. The target technique developed at
the SC ISOLDE is, in most cases, directly
applicable with the new beam.
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ISOLDE at the PS-BOOSTER The basic principle of
ISOLDE is that radioactive nuclides are produced
in spallation, fission or fragmentation reactions
with a thick target placed in the external proton
beam of 1 GeV. To most nuclear and high-energy
physicists, the word "target" evokes the idea of
a passive foil or rod, but here the target is, in
reality, a small chemical factory that, under
intense bombardment, supplies the radioactive
beam, that after magnetic analysis, is steered to
the experiments. The large range in solids of
high-energy protons and also the reactions
induced by secondaries are essential in providing
ISOLDE with intensities that, in general, cannot
be matched by other machines.
The proton injector for ISOLDE, the PS Booster,
is a stack of four small synchrotrons
pre-accelerating protons, delivered by a Linac,
to 1 GeV before injection into the CERN Proton
Synchrotron (PS). PS in turn supplies particles
to all CERN's high-energy machines. The PSB gives
one pulse of 3.21013 protons every 1.2 seconds.
Up to half of the pulses in the 12 pulses long
super cycle to the PS is brought to bombard the
ISOLDE target. This gives an equivalent of about
2 microA dc beam. The transfer of ISOLDE from the
600 MeV dc proton beam at the CERN SC to the time
structure, with a short high density proton pulse
at low repetition rate, increased the release
time of the produced radioactivity from the
target. This increased predominantly the
production of very short-lived species and makes
the ISOLDE beam bunched. In addition it allows
"background free" experiments between the pulses
because the neutrons, which are the main sources
of background, die out in the first 100 ms after
the beam burst. The target technique developed at
the SC ISOLDE is, in most cases, directly
applicable with the new beam.
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The laser ion source has been developed to ionize
isotopes of elements which could not be ionized
efficiently by any of the other types of ion
sources or to obtain a purified beam. This is
possible because the laser ion source works only
on the atoms of the element the laser wavelengths
are tuned for (chemical selectivity), the
isobaric contamination is therefore reduced down
to small amounts, which are caused by surface
ionization inside the tube where laser ionization
takes place and which needs moderate heating. The
laser system consists of copper vapor lasers,
tunable dye lasers and non linear crystals for
frequency doubling or tripling offering the
possibility for most efficient two or three step
ionization.
The plasma ion source is used to ionize elements
that cannot be surface-ionized. The plasma is
produced by a gas mixture (typical Ar and Xe)
that is ionized by electrons being accelerated
between the transfer line and the extraction
electrode by supplying an anode voltage of about
130 V. For the optimization of this process an
additional magnetic field is used (SRCMAG).
Plasma ion sources have been used in combination
with most target materials.
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The heart of an on-line isotope separator is its
target and ion source. The target should assure a
fast liberation of the radioactive nuclei
produced in large amounts of target material. The
combination with the ion-source should be able to
produce an ion beam which preferably should only
contain isotopes from one chemical element. The
development of this experimental technique is a
field of radiochemistry, which also involves
metallurgy, high temperature chemistry and
surface physics. The ISOLDE group has developed
many different advanced target-ion-source
combinations, which have allowed the users of the
facility to study radioisotopes from more than 60
different elements. the elements for which beams
are available at ISOLDE today are indicated in
the periodic table, which also allows to obtain
information on the produced quantities. Some of
the targets used at ISOLDE consist of molten
metals kept at temperatures from 700o C and up to
about 1400o C. Such targets are characterized by
a relatively long release time of the produced
isotopes and a typical time constant of the
release is about 30 seconds. Faster release
times, in the order of one second or less, can be
obtained, if target material in the form of
refractory metal powder, metals or carbides is
used at temperatures above 2000o C. An expected
decrease in the release time due to the
"shock-wave" effect of the pulsed proton beam has
been observed. Time constants down to some tenths
of a second can be reached for the fastest
targets.
The surface ion source is the simplest set-up for
ionizing atoms produced in the target. The
ionizer consists only of a metal tube ("line"),
for example tantalum or tungsten, which has a
higher work function than the atom that should be
ionized. Depending on the line's material it can
be heated up to 2400o C. Surface ion sources have
been used in combination with most of the
different target materials.
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Separatoren an ISOLDE (CERN)
The second separator, the High Resolution
Separator (HRS), is equipped with two bending
C-magnets with bending angles 90 and 60
degrees, respectively. At the moment one single
mass, with a resolution of about M/?M5.000, can
be separated routinely with the HRS separator.
The calculated beam profiles for the masses 99,
100 and 101 are shown in the figure. It will be
possible to achieve a maximal resolution of more
than 30.000.
The ISOLDE PS-Booster facility is equipped with
two isotope separators. The General Purpose
Separator (GPS) is designed to allow three beams,
within a mass range of 15, to be selected and
delivered to the experimental hall. The magnet is
double focussing H-magnet with a bending angle of
70 and a mean bending radius of 1.5 m. The mass
resolving power is M/?M2400.
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Konzepte für Separation im Fluge
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Erzeugung hochgeladener Isotope an der GSI
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Beispiel 78Ni
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Br - DE - Br Separation Method
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Reichweite und Energieverlust geladener
Teilchen in Materie nach Bethe-Bloch
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Der Fragmentseparator der GSI
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GSI Kombination von relativistischen
Ionenstrahlen, Fragmentseparator und
Speicherring (oder Neutronendetektor)