The recent creation of ARIBE has brought together existing access activities provided by the AIM-facility (Accélerateur d’Ions Multichargés) in Grenobleand the LIMBE-facility (Ligne d’Ions Multichargés de Basse Energie) in Caen. It was the aim to optimise the access for users and to construct a high-performing infrastructure at GANIL. Thus, ARIBE unifies the equipment existing in both laboratories and profits from the expertise of both teams. The restructuring process ended in 2005, celebrated by the organisation of an international workshop on ‘Interdisciplinary Research with Low Energy Ion Beams', IRSIB05.
New building housing the ARIBE facility
The ARIBE infrastructure is an installation which delivers low-energy ion beams of high quality to internal and external user groups. It is located in hall D on the site of GANIL (Grand Accélérateur National des Ions Lourds) situated in Caen in France. The access activity represents one of the main objectives of the laboratory CIRIL (Centre de Recherche Interdisciplinaire Ions Lasers), which is responsible for the running and the permanent improvement of this infrastructure.
A part of the ARIBE-facility (LHI) is shown below. The installation disposes of different types of ECR ion sources supplying in total eight beam lines. The three characteristics which make the infrastructure unique on a world-wide level are: Intense beams of highly charged atomic ions at keV up to MeV energies, mono-energetic highly charged ions at eV energies and mass-selected beams of various types of metallic or semiconductor clusters (under development).
The LHI beam lines drive multicharged ions from a high performance ECR ion source (SUPERSHYPIE) which can deliver highly charged atomic ions with high intensities at energies between 3 and 25 keV per charge into 7 different beam lines. Typical ion beams are Ar 17+ with 80 nA and Xe 30+ with 1 µA at the experimental site.
For details, see: L. Maunoury et al, ‘A new facility for low-energy beams’, Rev. Sci. Instrum. 73, 561 (2002)
LHI beam line
The TBE-device is equipped with a CAPRICE-ECR-ion source which delivers ion beams of highly charged atomic ions with a very narrow energy spread (1eV/charge). The mass selected ions can be decelerated in a short beam line down to energies of about 1eV per charge, thus opening new fields of applications. Exemplary data are: beams of Ar16+, 180pA, beam diameter: 2 mm, emittance: 20 π mm mrad, energy: 6.8 eV/charge, energy spread: 1.2 eV/charge.
For details, see H. Lebius, et al, Rev. Sci. Instrum. 74, 2276 (2003)
This beam line delivers mass-selected beams of singly charged clusters. Either positively or negatively charged clusters from metals, refractory materials or semiconductors are produced in a discharge source (magnetron) combined with the gas aggregation chamber[4]. The cluster beams are expected to serve for deposition of mass-selected clusters on substrates as well as for experiments in fundamental research.
In a European comparison, the infrastructure ARIBE can deliver beams of ions in high charge states (max.: ~35) with high intensities (~µA). This allows to study interactions of ions with thin targets like effusive or collimated beams of atomic particles (electron beams, ion beams or cluster beams). Ions in high charge states are very often used as a tool to multi-ionise and prepare other atomic systems. This can be done without appreciable energy transfer. This method allows to study the stability and the fragmentation of cold, highly charged systems.
eV-beams of highly charged ions have become available recently. The developed system is unique in Europe and will help to attract new users from nearby fields. Very slow multiply charged ions can be seen as a powerful tool for application in fields like surface chemistry, biological damage studies, cluster interactions, as a specific amount of potential energy (depending on the projectile charge) can be deposited very locally.
At present, cluster beams are not available at other European infrastructures giving access to the community on a regular basis. This instrumentation will allow us to study in more detail cluster-cluster collisions, charge instabilities in clusters and to deposit clusters by soft-landing techniques on surfaces or in rare-gas matrices, thus ensuring the opening of the infrastructure to other fields.
Summarising, ARIBE will not only serve the European community working in the field of atomic and molecular physics, but also in fields like irradiation damage, low-intensity irradiation, nano-structuring of surfaces linked to nano-electronic applications or surface modification and surface treatment.
Attribution of beam time is organised by a local committee, beam time attributed within the TA-programme by the PSP of ITS-LEIF. The first one attributes beam time twice a year through the peer review of a selection board. A typical requested beam time is of the order of 2 to 3 weeks, depending on the complexity of the experiment. Due to the strong demand a part of the proposals has been rejected or the demanded beam time has been reduced (up to 50 %), another part had to be postponed into the next programming period.
In order to assist the users during their stay, the infrastructure nominates a technician and a scientist who support the user group during the installation of the experiment, the running of the experiment as well as during its de-installation. For larger experiments a team of technicians is available for the period of installation and demounting. A specific group helps the users in aligning their experiments with respect to the beam lines.
The nominated physicist contacts the user group before the arrival in order to discuss details of the experiment which require specific preparations (conformity with security rules, supply with gases or liquid nitrogen, exact connection flanges needed, etc..). He will also assist the user team in the case of arising problems during the running of the experiment trying to find a local solution (electronics, vacuum parts, software or acquisition systems...).
Upon their arrival, the users get a short introductory course on the operation of the ion sources and the control of the guiding system for the ion beam. In particular, they are informed on the operation of valves and on the measures to be taken in the case of emergency. During the experiment, the research teams use an acquisition room, to which all important data from the experiment (ion current values measured at different positions, counting signals, further electrical signals) are transferred. In addition, the user can see on a screen display the status of the ion source and the beam line parameters, and can in certain cases interact directly with the beam parameters and settings. A multi-parameter acquisition system, which has the multihit-capability and which is well adapted for coincidence studies on an event-by-event basis is at the disposition of the user groups.
The research groups are accommodated in the guest house of GANIL at a low-cost price. Either they can use a kitchen facility or they can take advantage of the GANIL-restaurant. A meeting room is available close to the experimental area with connection to the Internet. The scientific environment is characterised by the presence of CIRIL, a centre for interdisciplinary research with ions and lasers, and the GANIL, the large national heavy ion accelerator in France. Thus, this site represents a fruitful symbioses of different research directions. Groups with outstanding expertise in the field of atomic and molecular physics, for cluster and biomolecules studies, in surface physics and material research, for the irradiation of biological tissues and polymers and solids and finally in the field of nuclear physics. Due to the organisation of regular seminars in these different fields of research and due to discussions with the present scientists, the user groups do have the possibility to integrate concepts and to follow new ideas which have been developed in close-by fields.
ARIBE Equipments
The ARIBE facility is divided into three parts : the very low energy beam line LTBE, the high intensities beam lines LHI and the cluster beam line LAST. In the following, there is a brief description of each beam line.
It is composed of an ECR ion source which is able to provide multiply charged ions in high charge state (up to Xe30+). There is a diagnostic box to characterize the ion beam and to prepare its shape before entering the decelerating lens system. This ion optical system serves to slow down the ions and to focus them at an image plan, which can be moved in a range of 20 cm. It is possible to decelerate the beam starting from 20 keV/q down to a few eV/q with a size of about 3 mm.
All the system is computer assisted with a new control-command system developed for this beam line. Some typical examples are shown in the following figure; the ion currents have been measured with the LEIF-Faradaycup (behind 2 apertures with a diameter of 2 mm placed at a distance of 50 mm).
These beam lines are supplied by an ECR ion source which is able to provide multiply charged ions in high charge states with high intensity. This means that intensities in the range of eµA for charge state equal or higher than 30+ can be provided. The energies are variable between 3*q keV and 25*q keV. There are seven beam lines among which two are totally composed of magnetic systems. The others contain magnetic as well as electrostatic optical systems. Concerning the magnetic beam lines, the ion beam transmissions (between the faraday cup located after the analyzing magnet and the end of the beam line) are 80% and 60%. The beam spot size can be varied from a few mm up to 40 mm and the focal plane of the beam can be moved within a large range (several tens of cm). Concerning the other beam lines, there is a switching magnet which can deliver the beam to five beam lines, three out of which are equipped with double Einzel lenses in order to obtain long focal distances. The other two lines terminate with a single Einzel lens and are more adapted to smaller experimental devices. Each beam line is equipped with diagnostic boxes : faraday cup, set of horizontal and vertical steerers , set of movable apertures.
Ion |
Intensity eµA (analyse dipole exit) |
Intensity eµA |
He2+ |
1500 |
1200 |
O7+ |
140 |
112 |
Ar17+ |
0.1 |
0.08 |
Kr24+ |
4.5 |
3.6 |
Xe30+ |
1 |
0.8 |
This beam line delivers beams of mass-selected, singly charged clusters. Either positively or negatively charged clusters from metals, refractory materials or semiconductors are produced in a discharge source (magnetron) combined with the gas aggregation chamber. Actually the mass selection is made by pulsed time-of-flight system which can work in the KHz-range and which can deliver cluster beam intensities in the nA to pA range. The cluster beams are expected to serve for deposition of mass-selected clusters on substrates as well as for collision experiments in fundamental research. In near future, continuous cluster beams will become available based on the used of a quadrupol mass filter adapted for his mass units (up to 9000 amu).
The following list identifies instrumentation which is available at the infrastructure ARIBE and which can be used (in collaborations) for user experiments:
Wiley-McLaren: large acceptance; mass resolution ~ 2000 at m=2000 amu
Reflectron: limited transmission; mass resolution ~ 14000
Under construction: Electrospray Ion Source