Atomic Beam Merging and Suppression of Alkali Contaminants in Multi Body High Power Targets: Design and Test of Target and Ion Source Prototypes at ISOLDE

Abstract

The next generation of high power ISOL-facilities will deliver intense and pure radioactive ion beams. Two key issues of developments mandatory for the forthcoming generation of ISOL target-ion source units are assessed and demonstrated in this thesis. The design and production of target and ion-source prototypes is described and dedicated measurements at ISOLDE-CERN of their radioisotope yields are analyzed. The purity of short lived or rare radioisotopes suffer from isobaric contaminants, notably alkalis which are highly volatile and easily ionized elements. Therefore, relying on their chemical nature, temperature controlled transfer lines were equipped with a tube of quartz that aimed at trapping these unwanted elements before they reached the ion source. The successful application yields high alkali-suppression factors for several elements (ie: 80, 82mRb, 126, 142Cs, 8Li, 46K, 25Na, 114In, 77Ga, 95, 96Sr) for quartz temperatures between 300ºC and 1100ºC. The enthalpies of adsorption on quartz were measured for Rubidium and Caesium. The enthalpies ΔHad (Rb) = -242 ± 20 kJ/mol and ΔHad (Cs) = -145 ± 20 kJ/mol are in good agreement with those obtained by isothermal chromatography. For proton beam power of the order of 100 kW such as foreseen in the EURISOL-DS project for direct ISOL targets, multi-body target units connected to a single ion-source are proposed. The so-called “Bi-Valve” target prototype aims to benchm ark the engineering tools required to simulate effusion related decay losses and to validate the multi body target concept. Four isotopes were investigated online: 34,35Ar and 18,19Ne. The efficiency of the double line merging was found to be in the range of 75 to 95%. The diffusion (analytical) and effusion (Monte Carlo) code RIBO provided the profile of the effusion distribution of the isotopes within the Bi-Valve unit for the different operation modes. A mathematical expression for the probability, p(t) that an isotope diffuses and effuses through the system is proposed. The simulated release efficiencies were in agreement with the experimental ones for 34, 35Ar at 95% thus opening the way to the engineering of multi body target units for future facilities.

Full text

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CERN-THESIS-2010-057
10/12/2009

UNIVERSITÉ PARIS XI
École Doctorale
Rayonnements & Environnement

No SUDOC : 2009PA112253





Atomic Beam Merging and Suppression of Alkali Contaminants in Multi
Body High Power Targets:
Design and Test of Target and Ion Source Prototypes at ISOLDE

Thèse
présentée pour l’obtention du grade de
Docteur en Sciences de l’Université Paris XI Orsay
par
Elian J. A. BOUQUEREL


















Soutenue le 10 Décembre 2009
Membres du Jury
Bernard BERTHIER - Directeur de thèse
Pierre BRICAULT - Rapporteur
Pierre DESESQUELLES - Président de Jury
Jacques LETTRY - Superviseur
Marc LOISELET - Rapporteur
Thierry STORA - Superviseur

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Page 3

Atomic Beam Merging and Suppression of Alkali Contaminants in Multi
Body High Power Targets: Design and Test of Target and Ion Source
Prototypes at ISOLDE













Author: Elian J. A. BOUQUEREL - CERN Marie Curie Fellow (FP6) /PhD Student,
Ecole Doctorale Rayonnements et Environnement, Paris-Sud XI.
Thesis Director:
Rapporteur:
President of Jury: Pierre DESESQUELLES - IPN-Orsay, Paris
Supervisor: Jacques LETTRY - CERN, EN Department, Geneva, Switzerland.
Rapporteur: Marc LOISELET - Centre de Recherches du Cyclotron, Louvain-la-Neuve,
Belgium.
Supervisor: Thierry STORA - CERN, ISOLDE, Geneva, Switzerland.


No SUDOC: 2009PA112253

Bernard BERTHIER, Research Director, IPN-Orsay, Paris-Sud XI.
Pierre BRICAULT - TRIUMF, Vancouver, Canada.
December 2009

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Abstract


The next generation of high power ISOL-facilities will deliver intense and pure
radioactive ion beams. Two key issues of developments mandatory for the forthcoming
generation of ISOL target-ion source units are assessed and demonstrated in this thesis. The
design and production of target and ion-source prototypes is described and dedicated
measurements at ISOLDE-CERN of their radioisotope yields are analyzed.
The purity of short lived or rare radioisotopes suffer from isobaric contaminants,
notably alkalis which are highly volatile and easily ionized elements. Therefore, relying on
their chemical nature, temperature controlled transfer lines were equipped with a tube of
quartz that aimed at trapping these unwanted elements before they reached the ion source.
The successful application yields high alkali-suppression factors for several elements (ie: 80,
82mRb, 126, 142Cs, 8Li, 46K, 25Na, 114In, 77Ga, 95, 96Sr) for quartz temperatures between 300ºC
and 1100ºC. The enthalpies of adsorption on quartz were measured for Rubidium and
Caesium. The enthalpies ΔHad (Rb) = -242 ± 20 kJ/mol and ΔHad (Cs) = -145 ± 20 kJ/mol are
in good agreement with those obtained by isothermal chromatography.
For proton beam power of the order of 100 kW such as foreseen in the EURISOL-DS
project for direct ISOL targets, multi-body target units connected to a single ion-source are
proposed. The so-called “Bi-Valve” target prototype aims to benchmark the engineering tools
required to simulate effusion related decay losses and to validate the multi body target
concept. Four isotopes were investigated online: 34,35Ar and 18,19Ne. The efficiency of the
double line merging was found to be in the range of 75 to 95%. The diffusion (analytical) and
effusion (Monte Carlo) code RIBO provided the profile of the effusion distribution of the
isotopes within the Bi-Valve unit for the different operation modes. A mathematical
expression for the probability, p(t) that an isotope diffuses and effuses through the system is
proposed. The simulated release efficiencies were in agreement with the experimental ones
for 34, 35Ar at 95% thus opening the way to the engineering of multi body target units for
future facilities.

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Résumé
La prochaine génération d’installation ISOL ‘haute puissance’ délivrera des faisceaux
d’ions radioactifs intenses et purs. Deux points clés de développements nécessaires pour la
prochaine génération d’unités de cibles et sources d’ions ISOL sont testés et démontrés dans
cette thèse. La conception et la production de prototypes sont décrites et les mesures de leurs
radioisotopes effectuées à ISOLDE-CERN sont analysées.
La pureté des radioisotopes rares ou ayant une courte durée de vie souffre de
contaminations isobariques, parmi lesquelles, les alcalins qui appartiennent aux éléments
hautement volatiles et facilement ionisables. En tenant compte de leur nature chimique, des
lignes de transferts ont été équipées avec un tube de quartz pour retenir ces éléments avant
que ceux-ci n’atteignent la source d’ions. L’application a montré avec succès la suppression
des alcalins avec un facteur important pour différents éléments (ex: 80, 82mRb, 126, 142Cs, 8Li,
46K, 25Na, 114In, 77Ga, 95, 96Sr) à des températures de quartz allant de 300ºC à 1100ºC. Les
enthalpies d’adsorption du quartz ont été mesurées pour le Rubidium et le Césium. Les
enthalpies ΔHad (Rb) = -242 ± 20 kJ/mol et ΔHad (Cs) = -145 ± 20 kJ/mol sont en accords
avec celles obtenues par chromatographie isotherme.
Pour un faisceau de protons avec une puissance de 100 kW, comme celui envisagé
dans le projet EURISOL-DS, des unités de cibles constituées de plusieurs parties connectées
à une seule source d’ions sont proposées. Le prototype de cible appelé Bi-Valve a pour
objectif de valider les outils d’ingénierie requis pour simuler l’effusion des pertes par
désintégrations et le concept d’une cible à plusieurs compartiments. Le Bi-Valve est une
double cible et ligne de transfert se jetant dans une seule source d’ions FEBIAD. Quatre
isotopes ont été étudiés en ligne : 34,35Ar et 18,19Ne. L’efficacité de la double ligne a été
mesurée allant de 75 à 95%. La diffusion (analytique) et l’effusion (Monte Carlo) étudiées
avec le Code RIBO a permis l’élaboration du profil de la distribution de l’effusion des
isotopes à travers le Bi-Valve pour différents modes opératoires. Une expression
mathématique de la probabilité, p(t), qu’un isotope diffuse et effuse à travers le système est
proposée. Les efficacités de relâchement simulées ont été en accord avec l’expérience pour le
34, 35Ar à 95% et ouvre donc le chemin à l’élaboration d’unités à cibles multiples pour de
futures installations.

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Contents


Introduction ........................................................................................................... 11

Chapter 1. ISOL Method and Radioactive Ion Beam (RIB) Production at ISOLDE-
CERN .................................................................................................................... 15
1.1
1.2
The PS Booster ........................................................................................................... 16
Mechanisms of nuclear reactions ................................................................................ 17
1.2.1
Impact parameter, cross section and isotope production ...................................... 17
1.2.2
Spallation, fission, fragmentation and fusion-evaporation ................................... 20
1.2.3
Reactions used at ISOLDE ................................................................................... 22
1.3
ISOLDE facility .......................................................................................................... 23
1.3.1
Targets and materials ............................................................................................ 23
1.3.2
Transfer lines ........................................................................................................ 27
1.3.3
Ion sources ............................................................................................................ 27
1.4
Mass separation ........................................................................................................... 34
1.5
Physics at ISOLDE ..................................................................................................... 36

Chapter 2. Fundamental Processes Affecting the Release of Isotopes to Produce
a RIB ..................................................................................................................... 37
2.1
2.2
2.3
2.4
Beam purity ................................................................................................................. 38
Release properties and decay losses through a target-ion source unit ........................ 39
Diffusion process ........................................................................................................ 40
Effusion process .......................................................................................................... 42
2.4.1
Conductance of a transfer line .............................................................................. 42
2.4.2
Adsorption phenomena ......................................................................................... 43
2.4.3
Effusion of a radioactive element ......................................................................... 46
2.5
Models of the release function .................................................................................... 49

Chapter 3 Purification of a RIB by Alkali Suppression in a Quartz Line Target . 51
3.1
Development of a quartz (SiO2) transfer line ............................................................. 52
3.1.1
Choice of the trapping material and geometry of the line .................................... 52
3.1.2
Thermal characteristics of a tube of SiO2 into a Ta transfer line .......................... 54

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3.2
Suppression of the alkali contamination by a temperature controlled quartz line ...... 61
3.2.1
Trapping of the 79, 80, 82mRb and 126, 142Cs contaminants ........................................ 61
3.2.2
Trapping of other alkalis: 8Li, 46K and 25Na ......................................................... 63
3.3
Production of 122,126 Cd and 75 Zn ................................................................................ 65
3.4
Retention of 95, 96 Sr, 77 Ga and 114 In by the quartz ..................................................... 66
3.5
Enthalpies of adsorption for the Rb and Cs onto SiO2 ............................................... 67
Chapter 4 Effusion and Decay Losses of a Multi Body Target Coupled to one
Ion Source ............................................................................................................. 71
4.1
Design of a dual target-transfer line unit (Bi-Valve) .................................................. 73
4.1.1
Isotope production and energy deposition in a double CaO target ....................... 73
4.1.2
Engineering of the Bi-Valve ................................................................................. 75
4.1.3
Settings of the FEBIAD Ion Source with Ar/Xe and Kr gases ............................. 81
4.2
Release of 34, 35Ar and 18, 19Ne noble gases from the Bi-Valve ................................... 82
4.2.1
Tightness and symmetry of the double target-line measured with 34, 35Ar. .......... 82
4.2.2
Impact of the operating modes on ion source efficiencies and yields of 18, 19Ne
and 34, 35Ar ............................................................................................................. 84
4.2.3
Time structures, impact of the dual transfer line on the effusion process and
decay losses ........................................................................................................... 85
Conclusions and Outlook ...................................................................................... 93
Bibliography .......................................................................................................... 97

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Remerciements
Cette thèse marque l’aboutissement d’un intéressant et long parcours universitaire qui m’a donné
la chance de découvrir et de côtoyer des personnes de différents horizons: Montpellier, Glasgow, Belfast,
Genève…

Je tiens tout d’abord à remercier mon superviseur, Jacques Lettry (CERN) pour m’avoir accueilli
au sein de l’équipe ISOLDE et donné l’opportunité de travailler à l’élaboration de ces prototypes dans le
cadre du programme de Bourse Européenne, Marie Curie (projet HIGHINT). Je remercie Thierry Stora
pour m’avoir guidé et conseillé tout au long de ces recherches et Richard Catherall, chef de Section RBS.

Merci à Bernard Berthier, Directeur de Recherche à l’IPN d’Orsay, pour avoir accepté d’être mon
directeur de thèse ; merci pour ses conseils, sa patience et sa disponibilité. Mes remerciements vont aussi
aux membres du Jury, plus particulièrement aux rapporteurs Pierre Bricault et Marc Loiselet pour avoir
accepté cette mission qui nécessite beaucoup de temps. Merci à Pierre Desesquelles pour être le Président
du jury et à Michel Davier, conseiller aux thèses à l’Université Paris XI, pour ses conseils.
Merci à mon collègue de bureau, Etam Noah pour son amitié, son aide, sa patience et pour avoir
supporté mes ‘excès de folie’ et mes plantes pendant toutes ces années.
Je remercie l’équipe de développement de cibles/sources RBS-ISOLDE pour sa formidable
atmosphère, son accueil et sa compétence ; merci notamment à Daniel Carminati, Bernard Crépieux,
Ermano Barbero, Liviu Penescu, Stefano Marzari, Herta Richter, Luca Bruno, Mats Lindroos, Mike
Owen, Sandrina Fernandes, Tim Giles, Martin Eller…Merci à l’équipe PH-ISOLDE dont Alex Helert,
Manuela Turrions Nieves & Luis Fraile, Karl Johnston (et Anne-Gaelle), Ulli Koester, Mélanie Marie-
Jeanne, Dina Lopes, Gry Tveten, Frederic Wenander, Guilherme Correia, Ligia Amorim, Ana Marques,
Sarah Naimi, Martin Breteinfeld & Tania Mendonça. Merci aux ingénieurs en charge d’ISOLDE: Erwin
Siesling, Magnus Eriksson, Pascal Fournier, Emiliano Piselli...Je remercie l’équipe CERN-FLUKA pour
m’avoir gentiment aidé dans l’apprentissage du code : Vasilis Vlachoudis, Adonai Herrera, Mario
Santana Leitner, Sylvestre Catin et Anna Mackney. Merci à Luisella, Alessio, Ketil, Elias, Roberto,
Markus, Francesco, Daniel…et ainsi qu’à Virginie pour les pauses-café agréables.
Je remercie Marie Sklodowska Curie (1867-1934) sans qui cette bourse et ce programme n’aurait
jamais existé.

Merci à mes amis pour leur présence, leur support et leur compréhension : Larissa, Marina, Marc,
Erika, Candys, William, Kerri-Ann, João, Diana, Agathe, Alex, Marie. Merci à eux, et pardon à ceux
que j’ai pu malencontreusement oublier…
Je remercie mes parents pour leurs encouragements et leur soutien sans faille aucune dans tout ce
que j’entreprends depuis mon premier cri.

Je remercie cette inépuisable et formidable source artistique qu’est la musique et les nombreux
groupes qui m’ont été un apport non négligeable en énergie et en créativité tout au long de ces travaux. Je
remercie entre autres Amorphis, Indochine, Dark Tranquillity, Therion, Muse et Radiohead d’exister.
‘’La musique donne une âme à nos cœurs et des ailes à la pensée’’ (Platon).

Je dédie enfin cette thèse à ma tante, Yolande Bourrel; je suis sûr que ce manuscrit va lui donner
une occasion de parler de moi là où elle se trouve.

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The scientific community has a growing interest in the study of radioactive nuclei far from
the stability region. Nuclei far from stability play decisive roles in astrophysical
nucleosynthesis that build up heavier elements than Lithium (stars and supernovae). The
study of exotic nuclei contributes to the understanding of the isotopes present on Earth.
Radioactive Ion Beams (RIBs) concern numerous domains such as nuclear physics, nuclear
astrophysics, weak interaction physics, solid state physics and life sciences. After being
produced, the nuclides of interest are electromagnetically mass-separated from the other
reaction products and distributed to the experimental physics community and/or post-
accelerated.
The physics of radioisotopes is the natural continuity of the studies started by Henri
Becquerel, when observing the radioactivity of Uranium in 1896 [Bec-96] and afterwards by
Pierre and Marie Curie when isolating Polonium and Radium in 1898 [Cur-98]. In 1934,
Irene Curie and Frederic Joliot were the first physicists to create unstable nuclei in their
laboratory [Jol-34]. The idea of coupling a target to an ion source from an electromagnetic
mass separator was first developed in the Niels Bohr institute in 1951 [Kof-51]. In the late
60’s, Isotope Separators On Line facilities were built and linked to accelerators mainly in
Europe. At ISOLDE-CERN (Geneva) this concept was demonstrated to be working
efficiently [Rav-75] leading to controlled, high intensity beams of RIBs available to scientists
for precision measurements.

RIBs can be produced with a wide variety of techniques. Typically the isotopes of interest are
produced in a nuclear reaction (between an accelerated primary projectile beam and a
stationary target). The two main production mechanisms are the Isotope Separation On Line
(ISOL) method and the In Flight method. In the ISOL method, radioactive ions are produced
essentially at rest in a thick target which is bombarded with energetic primary particles from
an accelerator. After diffusing out of the target, effusing through the transfer line and being
ionised, the radioactive ions are accelerated in a post-accelerator.
For the In-Flight method an energetic heavy-ion beam is fragmented while passing through a
thin target. After mass, charge and momentum selection in a fragment separator the selected
ions are analysed.
Introduction

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INTRODUCTION

Radioactive Ion Beams are present and developed all around the world.



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Low energy RIB facilities:
IGISOL (Ion Guide Isotope Separator On-Line) at JYFL (University of Jyväskylä)
[Moo-05] is a facility that delivers RIBs of short-lived exotic nuclei, in particular the neutron-
rich isotopes from the fission reaction. The beam is cooled, bunched and isobarically purified.
The isobaric purification is achieved in by a Penning trap placed after the RF-cooler element.
SLOWRI (Slow RI-beam facility) is being built at the RIKEN RI-Beam Factory
(RIBF). It will provide slow, high-purity and small emittance ion beams of all elements [Rik-00]
IRIS (Investigation of Radioactive Isotopes at Synchrocyclotron) on-line isotope
separator facility at the PNPI (Petersburg Nuclear Physics Institute)-Gatchina produces nuclei
far from stability by interaction of 1 GeV protons with uranium targets with a typical proton
current of 100 μA [Pan-02].
Facilities with post-accelerated RIBs:
SPIRAL (Système de Production d’Ions Radioactifs Accélérés en Ligne) at GANIL
(Grand Accélérateur National d’Ions Lourds) is an ISOL and post-accelerator facility. It
combines a target-ion source assembly and a particle accelerator, CIME (Cyclotron pour Ions
de Moyenne Energie). The facility delivers radioactive beams with energies in the range
between 1.7 and 25 A MeV [Vil-01].
ISOLDE facility at CERN uses proton beams up to 4 μA from the PS Booster [Iso-
00]. The RIBs are produced from 25 available target materials and 4 types of ion sources (See
Chapter 1), and are distributed to the experimental physics area or/and post accelerated by a
linear accelerator, REX-ISOLDE, up to 3.1 MeV/u [Rex-00].
ISAC at TRIUMF (Canada's National Laboratory for Particle and Nuclear Physics)
[Sch-1996] uses ISOL and post-acceleration schemes. It produces short-lived exotic nuclei
through a reaction between the primary proton beam and a thick target. Additional
experiments measure precise lifetimes of exotic nuclei. The first beam was achieved in 1997
with 0.5 µA of proton current on the production target, nowadays the current on target
reaches up to 100 µA [Sho-02].
The cyclotron facility at Louvain-la-Neuve [Loi-96] was based on a cyclotron
accelerating 30 MeV protons to produce the desired exotic element in suitable targets with an
intensity up to 300 μA and a post-accelerator. The activities in this facility ended in 2009.
HRIBF (Holifield Radioactive Ion Beam Facility) at ORNL (Oak Ridge National
Laboratory) [Car-08] produces neutron-rich radioactive nuclei via proton-induced fission of
uranium in a low-density matrix of UC. Recently developed RIBs include 25Al from a silicon
carbide target and isobarically pure beams of neutron-rich Ge, Sn, Br and I isotopes from a
uranium carbide target. Post-acceleration is made by 26 MeV tandem.

These facilities produce hundreds RIBs, and almost all the stable elements of the periodical
table have been studied. Since then, experimental nuclear physics has developed from the
technological progress of the accelerators of light particles and nuclei of heavy ions.
Other new facilities are planned worldwide. They will be designed to handle higher activities
for the radioactive nuclei produced in the primary target than is available at the actual, so
called first-generation, facilities [Nup-00]. In Europe this is structured by the Nuclear Physics
European Collaboration Committee (NuPECC) and in the United States by the Department of
Energy. Both have independently recommended the construction of a ‘second-generation’
facility, the EURISOL Design Study is based on the ISOL principle. It is a collaboration of
21 institutes and laboratories within Europe (full participants), with additional 21 institutions
either in Europe, North America and Asia (as contributors) [Eur-01]. The aim of such a study
is to increase the intensity with respect to existing facilities (from 100 μA to few mA of 1
GeV primary proton beam) [Gue-02]. A CW Linac up to 150 A MeV is planed to perform
post-acceleration process. The Rare-Isotope Accelerator (RIA) study is proposed in the USA

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INTRODUCTION

to produce intense RIBs accelerating beams of protons to 900 MeV to bombard thick targets.
(post-acceleration by a Linac up to 8-15 A MeV) [Nol-02].

Ongoing projects are:
SPIRAL2 which will accelerate 5 mA deuterons up to 40 MeV and 1 mA heavy ions
up to 14.5 MeV/u. Thick and thin targets will produce RIB (neutron induced fission of UC,
direct interaction of deuterons in a UC target and interaction of heavy ion beam with a target)
[Lec-08].
The FRIB (Facility for Rare Isotope Beams) at MSU (Michigan State University) will
use 400 kW of incoming power beam [Yor-09].
ISAC2 at TRIUMF will be an extension of the existing ISAC facility and will accelerate
RIBs up to 6.5 MeV/u for masses up to 150 [Lax-03].
HIE ISOLDE is an upgrade of the current ISOLDE facility at CERN; incoming beam
power will reach 10 kW (from Linac 4) to 40 kW (from LP-SPL) and post-acceleration up to
10 MeV/u for the 850 different available isotopes [Hie-00].
FAIR (Facility for Antiproton and Ion Research) at GSI will use existing SIS ring as
the injector to 2 further rings. RIB production will be achieved using the in-flight technique.
Uranium ions will be accelerated to 2 GeV/u for 238U28+ and 34 GeV/u for 238U92+ [Fai-00].
SPES (Selective Production of Exotic Species) at LNL (Legnaro National
Laboratories) is a project planning to accelerate proton beams to 40 MeV towards the ISOL
target. RIBs will be post-accelerated to 15 MeV/u in the linac ALPI [Spe-00].

The experiments described in this thesis were performed at the ISOLDE facility,
where more than 800 isotopes (73 elements) are produced making the facility one of the
world leaders in the low-energy radioactive ion beam research. It hosts a programme that
ranges from basic nuclear structure to weak interaction studies [Iso-00].
The target station is the heart of ISOLDE in which a 1 or 1.4 GeV proton beam from CERN's
PS booster accelerator strikes a target to produce a range of isotopes. The radioactive isotopes
produced by nuclear reactions in the stationary target diffuse out of it due to thermal energy.
Once on the surface of the target material, the isotopes effuse out of the target volume
through the transfer line and reach the ion source. Typically, targets are heated up to very
high temperatures (<2300ºC) to enhance the diffusion-effusion process. Atoms of interest are
then extracted, ionised and separated before they are steered to experiments. ISOLDE
produces radioactive beams of a variety of species by combining a range of target materials
with efficient and selective ion sources such as RILIS [Fed-06] to obtain the best possible
purity. However in certain cases, isobaric impurities prevent a proper utilisation for physics.
Thus new techniques of purification are mandatory.

The production of radioactive beams is a specialised field. It is important to design
targets which can withstand the high primary beam power and produce the desired ion
species by suitable material selection. Ion-extraction is particularly difficult if the ions have a
short lifetime. With the aim of producing good RIBs, the quest for ion sources with high
chemical selectivity, efficiency and long lifetime with emphasis on the beam optical
properties are the highest priorities. The beam intensity of short-lived isotopes is strongly
affected by decay losses due to time delay between in-target production and ion beam
extraction. The development of models for calculating the release efficiencies expressing the
decay losses due to diffusion from the target and effusion to the ion source is of key
importance for the design and performance prediction of future targets. The demand from
physics for higher particle or isotope production is driving facilities to higher accelerator
powers and more intense primary beams on targets. Indeed, the future generation of targets
will need to handle an incoming proton beam having a higher power than what is operated in
the current facilities. This will imply important changes in the development and design of the
target-ion sources used to deliver such ion beams.



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INTRODUCTION




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This thesis deals with two target-ion source units which have been developed with the
aim of anticipating and investigating RIB production at the future generations of ISOL
facilities in the framework of The European Marie Curie Program, HIGHINT (High
Intensity) project. Chapter 1 discusses the principles of the ISOL technique and the nuclear
reactions involved when sending a proton beam onto target materials. The facility of
ISOLDE-CERN and its physics are highlighted. Chapter 2 presents the fundamental
processes which affect the purity and the release properties of a RIB. The two main
parameters, diffusion and effusion, are presented as being the dominating phenomena
influencing RIB quality. EURISOL will operate at high power (100 kW on direct targets and
4 MW on converter). The direct targets will be used to produce primarily the proton-rich
radioactive ion beams. Delivering purer RIBs is therefore mandatory. To achieve this
purification task a target-transfer line unit having a quartz insert to trap alkali contamination
has been built and tested at ISOLDE, Chapter 3 presents the development and results of this
experiment. Hundreds of kW of incoming power will imply the use of multiple containers
merging in a single ion source to dissipate the heat generated by the impact of the proton
beam. It is then mandatory to know how the effusion process and the isotope decay losses are
affected by such a design. Chapter 4 presents a dual target-transfer line prototype which was
developed and tested at CERN-ISOLDE as a precursor of this concept.

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ISOL Method and Radioactive Ion Beam (RIB) Production at ISOLDE-
CERN

















Chapter 1