Ausbeuten radioaktiver Nuklide wurden an zwei verschiedenen Anlagen gemessen: dem Ruckstosseparator LOHENGRIN am Institut Laue Langevin in Grenoble und am on-line Isotopenseparator ISOLDE am CERN in Genf. Am LOHENGRIN wurden die Ausbeuten leichter geladener Teilchen in der neutroneninduzierten ternaren Spaltung verschiedener Aktinidentargets bestimmt: 233U, 235U, 239Pu, 241Pu und 245Cm. Dazu werden dunne Targets in einen hohen Neutronenfluss eingebracht. Die produzierten Kerne verlassen die Targets mit dem Ruckstos, den sie in der Kernspaltung erhalten. Die Intensitat wird bei verschiedenen Energien und Ionenladungszustanden vermessen. Nach Korrekturen fur die experimentelle Akzeptanz, den zeitlichen Verlauf der Spaltrate und der Bevolkerung der Ionenladungszustaende werden die Ausbeuten uber die Verteilung der kinetischen Energie integriert. Ein Vergleich der so gewonnenen Ausbeuten mit den Vorhersagen verschiedener ternarer Spaltmodelle zeigt dass die Ausbeuten der haufigsten Nuklide gut vorhergesagt werden. Andererseits unterschatzen die Modelle deutlich die Produktion von "exotischen" Kernen mit einem extremen N/Z Verhaeltnis. Daher ist eine Uberarbeitung dieser Modelle notwendig. Die gesammelten Daten bieten eine gute Grundlage um verbesserte Modelle zu testen. Im zweiten Teil der Arbeit wurden Ausbeuten von radioaktiven Nukliden an der "ISOL" (isotope separation on-line) Anlage ISOLDE bestimmt. Hier treffen hochenergetische Protonen (1.0 oder 1.4 GeV) auf Targets aus verschiedenen Materialien und verursachen diverse Kernreaktionen. Die dabei produzierten radioaktiven Kerne werden in den dicken Targets gestoppt und konnen bei hohen Temperaturen herausdiffundieren und freigesetzt werden. Anschliesend werden sie ionisiert, elektrostatisch auf 60 keV beschleunigt und nach der Masse separiert. Nun konnen sie an verschiedene Experimentierplatze verteilt werden und dienen einer Vielzahl von Anwendungen. Die Messung dieser Strahlintensitaten wird weniger genutzt um den Mechanismus der Produktion (Spaltung, Spallation oder Fragmentation) zu untersuchen, sondern um die Verluste die auf dem Weg von der Produktion zur Freisetzung auftreten besser zu verstehen und zu reduzieren. Im Gegensatz zu einem Ruckstosseparator schwanken diese Verluste stark zwischen verschiedenen Isotopen. Um die nutzbare Strahlintensitat zu erhohen ist eine sorgfaltige Optimierung vieler Faktoren notwendig: der chemischen Zusammensetzung und mikroskopischen Beschaffenheit des Targetmaterials, der Temperatur der Target- und Ionenquelleneinheit, des Typs und der Betriebsparameter der Ionenquelle, etc. Die erzielten Ausbeuten und mogliche Verbesserungen werden diskutiert anhand einiger Elemente: Be, Al, Mn, Ni, Cu, Ga, Cd, In, Sn, Cs and Fr. Ein wichtiger Beitrag zur effizienten und selektiven Separation vieler metallischer Elemente ist die RILIS Technik (Resonanzionisationslaserionenquelle). Ihre Anwendungen konnen sogar erweitert werden, um selbst Isomere zu trennen oder um Atomspektroskopie mit radioaktiven Isotopen zu betreiben. Mit diesen intensiven und "reinen" radioaktiven Ionenstrahlen wurden verschiedene neue Resultate in der Kernphysik erzielt. Diese umspannen fast die gesamte Nuklidkarte und beinhalten eine neue Bestimmung der Lebensdauer und der Emissionswahrscheinlichkeit fur beta-verzogerte Neutronen von 12Be T(1/2) = 21.34(23) ms, Pn = 0.48(+0.12-0.10)%), eine grobe Bestimmung der magnetischen Momente von 70gCu (mu = (+)1.8(3) mu_N) und 70mCu (|mu| = 1.2(3) mu_N), die Untersuchung der beta-verzoegerten Neutronenemission der neutronenreichen Kupfer-Isotope 73-78Cu mit dem ersten Nachweis der beta-verzogerten Neutronenemission von 73Cu, der ersten Messung der Lebensdauern von 149Cs (T(1/2) = 112(3)ms) und 150Cs (T(1/2) = 82(7)ms) und dem Nachweis neuer Gammalinien im Zerfall von 232Fr.

Ausbeuten und Spektroskopie radioaktiver Isotope bei LOHENGRIN und ISOLDE

A beam monitor detector prototype based on doped silica fibres coupled to optical fibres has been designed, constructed and tested, mainly for accelerators used in medical applications. Scintillation light produced by Ce and Sb doped silica fibres moving across the beam has been measured, giving information on beam position, shape and intensity. Mostly based on commercial components, the detector is easy to install, to operate and no electronic components are located near the beam. Tests have been performed with a 2 MeV proton pulsed beam at an average current of 0.8 μA. The response characteristics of Sb doped silica fibres have been studied for the first time.

A beam monitor detector based on doped silica and optical fibres

A beam monitor detector prototype based on doped silica fibres coupled to optical fibres has been designed, constructed and tested, mainly for accelerators used in medical applications. Scintillation light produced by Ce and Sb doped silica fibres moving across the beam has been measured, giving information on beam position, shape and intensity. Mostly based on commercial components, the detector is easy to install, to operate and no electronic components are located near the beam. Tests have been performed with a 2 MeV proton pulsed beam at an average current of 0.8 {\mu}A. The response characteristics of Sb doped silica fibres have been studied for the first time.

Today, two basically different methods have been developed for production of accelerated radioactive ion beams (RIB). The fragmentation of intense heavyion beams, in which the forward momentum impa...

Radioactive ion-beam projects based on the two-accelerator or ISOL principle

Modern experiments with secondary radioactive beams create new demands on beam diagnostics which has to provide on-line information on the low-intensity beams. We describe here a beam diagnostics system developed for the REX-ISOLDE facility (CERN), based on the observation of secondary electrons produced by a beam, impinging onto a foil. Results of tests with different beams of various energies and intensities are reported.

A beam diagnostic system for low-intensity radioactive beams

Recent developments of the EXCYT project

The aim of the EXCYT project (EXotics with CYclotron and Tandem) is the development of a facility for producing and accelerating exotic beams from 0.2 up to 8 MeV/amu. EXCYT is based on the “two accelerators” method. A K = 800 Superconducting Cyclotron (CS), axially injected by the ECR ion source SERSE, will deliver the primary beam. Such a beam will produce the required nuclear species in a modified ISOLDE type target-source complex. When required, a 15 MV Tandem Van der Graaff will accelerate the secondary beams. Both accelerators are existing and operational at Laboratorio Nazionale del Sud (LNS). Concerning the status of the project, progress has been made in most of the key issues of the project, like the construction of SERSE, cyclotron upgrading, modification of the existing building, high resolution mass separator, and diagnostic equipment for low energy, low intensity beams.

The ISOL exotic beam facility at LNS: the EXCYT project

We report on the test results obtained with a prototype beam profiler based on a thin slit and a CsI scintillator, read out by means of a compact photomultiplier. Such a device has proven to be suitable to perform ion beam diagnostics at low and very low intensities. In particular, our device is suitable for being used in the energy and intensity ranges expected at the EXCYT radioactive ion beam facility, that is currently under development at LNS Catania.

A self-calibrating ion beam profiler based on a csi scintillator

We report on the test results obtained with a prototype beam profiler based on a glass scintillating fibre and a compact photomultiplier, particularly suitable for the low intensity beam diagnostics needed in the framework of the EXCYT radioactive ion beam facility currently under development at the LNS in Catania.

Low intensity ion beam profiling with glass scintillating fibres.

Construction of a composite wall detector to be used with the intermediate energy beams of the LNS Superconducting Cyclotron-the energy resolution for the large area (20*30 cm/sup 2/) plastic scintillator, 2 cm thick, used as energy measurement detector, was measured. This detector is coupled to a Hybrid Photo Diode (HPD), acting as a photoconverter device, by means of a light guide of suitable shape and dimension. Two kind of configurations of the light guide were tested, one with the light guide glued on the smaller surface 2*20 cm/sup 2/, and one with the light guide glued on the larger surface 20*30 cm/sup 2/.

http://ieeexplore.ieee.org/iel4/5472/14772/00672626.pdf

Energy resolution measurements in the MACISTE detector

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