Single-ended Van De Graaff Research Articles

LABEC, the INFN ion beam laboratory of nuclear techniques for environment and cultural heritage

The LABEC laboratory, the INFN ion beam laboratory of nuclear techniques for environment and cultural heritage, located in the Scientific and Technological Campus of the University of Florence in Sesto Fiorentino, started its operational activities in 2004, after INFN decided in 2001 to provide our applied nuclear physics group with a large laboratory dedicated to applications of accelerator-related analytical techniques, based on a new 3 MV Tandetron accelerator. The new accelerator greatly improved the performance of existing Ion Beam Analysis (IBA) applications (for which we were using since the 1980s an old single-ended Van de Graaff accelerator) and in addition allowed to start a novel activity of Accelerator Mass Spectrometry (AMS), in particular for 14C dating. Switching between IBA and AMS operation became very easy and fast, which allowed us high flexibility in programming the activities, mainly focused on studies of cultural heritage and atmospheric aerosol composition, but including also applications to biology, geology, material science and forensics, ion implantation, tests of radiation damage to components, detector performance tests and low-energy nuclear physics. This paper describes the facilities presently available in the LABEC laboratory, their technical features and some success stories of recent applications.

Improvement of the High Fluence Irradiation Facility at the University of Tokyo

This paper reports the modification of the High Fluence Irradiation Facility at the University of Tokyo (HIT). The HIT facility was severely damaged during the 2011 earthquake, which occurred off the Pacific coast of Tohoku. A damaged 1.0MV tandem Cockcroft-Walton accelerator was replaced with a 1.7MV accelerator, which was formerly used in another campus of the university. A decision was made to maintain dual-beam irradiation capability by repairing the 3.75MV single-ended Van de Graaff accelerator and reconstructing the related beamlines. A new beamline was connected with a 200kV transmission electron microscope (TEM) to perform in-situ TEM observation under ion irradiation.

Photopages

Ion-atom collision experiments require, in many cases, accelerated light heavy ions of various charge states in the energy region of a few MeV. These types of beams can be produced using Penning ion sources combined with a charge state selector in the terminal of single ended Van de Graaff accelerators. We propose, in addition, the use of stripper targets in different locations in the beam transport system. In the present paper the experimental results obtained with pre-analyser and post-analyser strippers are presented and the performances of such systems are discussed.

JANNUS: A multi-irradiation platform for experimental validation at the scale of the atomistic modelling

The Joint Accelerators for Nanosciences and NUclear Simulation project was started in 2002 in the frame of collaboration between CEA and CNRS. Due to the scientific skills developed for a long time, two experimental sites have been considered: (1) at Saclay, three electrostatic accelerators are being coupled, a new 3 MV Pelletron machine equipped with a multi-charged ion source, a 2.5 MV single ended Van de Graaff and a 2.25 MV tandem and (2) at Orsay, a 2 MV tandem and a 190 kV ion implanter are being coupled together with a 200 kV transmission electron microscope to allow simultaneous co-irradiation and observation. A brief review is first presented on multi-irradiation facilities available in the world. Then, a technical description of the new experimental facilities being installed is given. The main experiments we intend to carry out using mono, dual or triple irradiation configurations in different nuclear application fields and especially in the fusion domain will be further presented.

JANNUS: experimental validation at the scale of atomic modelling

Ion irradiation is well suited to simulate neutron irradiation because primary knock-on atoms (PKA) produced by neutron collisions are self ions of the target. As the main difference, the energy spectrum of ion-produced PKAs is somewhat broader than in the case of fast neutrons. Studies of the combined effects of target damaging, ion implantation effects, helium and hydrogen production, and the occurrence of nuclear reactions should be performed by co-irradiation experiments (dual or triple beam irradiation). The JANNUS project (Joint Accelerators for Nanosciences and NUclear Simulation) was started in 2002 in the frame of a collaboration between CEA (Commissariat à l'Énergie Atomique) and CNRS–IN2P3 (Centre National de la Recherche Scientifique–Institut National de Physique Nucléaire et de Physique des Particules). Two experimental sites are involved. At Saclay, three electrostatic accelerators are being coupled: a new 3 MV Pelletron™ machine equipped with an ECR multi-charged ion source, a 2.5 MV single ended Van de Graaff and a 2.25 MV General Ionex tandem. At Orsay, the 2 MV tandem ARAMIS and the 190 kV ion implanter IRMA are being coupled with a 200 kV TECNAI™ transmission electron microscope to allow simultaneous co-irradiation and observation. This paper will first discuss both advantages and limitations of the use of ion beam irradiation to simulate neutron irradiation. A technical description of both set-ups is then presented, and some details will be given concerning multi-irradiation facilities running worldwide. The main application fields of JANNUS will be further detailed. To cite this article: Y. Serruys et al., C. R. Physique 9 (2008).

PRELIMINARY STUDY OF RIVER WATER IN GOLD MINING AREAS OF CAMBODIA

In Cambodia, artisanal mining has recently come to a social concern because of the possibility to cause environmental degradation and human health problems. The General Department of Mineral Resources of Cambodia is collecting environmental specimens in mining sites to watch the situation. This time, four water samples from Sampov Loon and one from Memong mining site were sent from the Department to Hiroshima University, Japan, and the samples were analyzed by means of PIXE at the University. A volume of 10 μl from each sample was separated and dropped onto 4 μm polypropylene backing foil. The measurement was carried out by using 2.5 MV single-ended Van de Graaff accelerator. A Si(Li) detector (active area, 80mm2; sensitive depth, 5mm; Be -window's thickness, 25 μm; resolution, 167 eV fwhm at 5.9 keV) was used for both of in vacuo PIXE and non-vacuum external beam PIXE measurement. A computer code PIXS was used for the quantification. The result indicates that there are at least two kinds of water in Sampov Loon and one of them possibly represents polluted condition.

The external beam microprobe facility in Florence: Set-up and performance

An external beam microprobe facility, based on a quadrupole doublet supplied by Oxford Microbeam Ltd, has been installed on a new beamline at the 3 MV single-ended Van de Graaff accelerator in Florence. The goal was to obtain a beam with a spot size on target of 10–20 μm and a current in the order of at least 1 nA, in order to allow PIXE, PIGE and RBS elemental analysis in air or in a helium atmosphere. The beam was extracted from the vacuum lines through a 0.1 μm thick Si 3N 4 window to minimise lateral straggling. The design goals have been successfully achieved; the measurements of the beam spot characteristics in vacuum as well as in air and in helium atmosphere, are here reported.

Micron-scale analysis of SiC/SiC f composites using the new Lisbon nuclear microprobe

A new nuclear microprobe has now been commissioned at ITN, Lisbon. This paper first describes the layout and modes of operation of the new microprobe, which is located on a 3.1 MV single-ended Van de Graaff accelerator. Within two days of first commissioning the microprobe, a spatial resolution of ∼1.5 μm was achieved for backscattering analysis, and a resolution of ∼1.0 μm for transmission work. The steps taken to produce this resolution, and the remaining factors, which further limit it are discussed. The first results from this microprobe for the spatially resolved analysis of SiC/SiC f ceramic composites are presented here. These materials have applications in fusion technology and structural changes were investigated after exposure to lithium orthosilicate and lithium titanate breeder materials in fusion relevant conditions. Ti and Cr rich precipitates could be found in the samples that were exposed to lithium titanate.

The Schonland Micro-Scanning Ion Beam Analysis Facility

The Schonland Micro-Scanning Ion Beam Analysis Facility is used for interdisciplinary research, uniting physics and many other disciplines. It has a unique dual accelerator input configuration. A wide range of high energy heavy and light ions is available from an EN Tandem van de Graaff accelerator with 6.0 MV terminal voltage. Light ions at lower energy but with much increased luminosity are available from a 2.5 MV single-ended van de Graaff accelerator. The sample chamber is equipped to image radiation and particles from a wide range of ion-beam interactions with matter. These include the ion beam analytical techniques of RBS, ERDA, PIXE, NRA, SecEM and STIM. Some of these techniques have been performed tomographically or under channeling conditions. Sub- or near-micron spot sizes for many of these techniques are available. The user interface to the sample chamber is highly automated, allowing safe and friendly interaction. The OMDAQ system developed at Oxford University is dedicated to on-line acquisition and preliminary analysis of singles spectra. The Physics Analysis Workstation (PAW + +) system developed for CERN and ported to a CAMAC-PC environment manages the more sophisticated multi-parameter acquisition and post-processing.

The Debrecen scanning proton microprobe facility and its applications to geological samples

The recently installed scanning proton microprobe of the Institute of Nuclear Research (ATOMKI) in Debrecen is supplied with proton beam from a home-made 5 MV single ended Van de Graaff accelerator, while focusing and scanning the beam is achieved by the commercially available system from Oxford Microbeams Ltd. including quadrupole doublet focusing lenses, slits, scanning coils and a PC-based data acquisition package. Its first PIXE application was made in micromineralogy, in the study of spherules. Spherules in different geological and geographical situations may have various extraterrestrial origin. Several of these objects uncovered in the western part of Hungary have been analysed. Cosmic origin can be supposed for the majority of the findings.

The new ATOMKI scanning proton microprobe

The scanning proton microprobe of the institute of nuclear research (ATOMKI) in Debrecen is based on an Oxford Microbeams coupled quadrupole doublet focussing system built up to the 0° beam line of the 5 MV single ended Van de Graaff accelerator. With the setup described here PIXE analysis, Rutherford backscattering spectrometry and detection of backscattered secondary electrons can be carried out simultaneously. A modified version of the PIXYKLM computer program developed in the institute is used for the evaluation of the PIXE spectra. Applications discussed are related to investigations performed on metal archaeological samples and individual aerosol particles.

The National University of Singapore nuclear microscope facility

The National University of Singapore nuclear microscope facility is based around a HVEC AN2500 single ended Van de Graaff accelerator and an Oxford Microbeams coupled quadrupole triplet focusing system. Particle induced X-ray emission (PIXE), nuclear or Rutherford backscattering spectrometry (RBS) and scanning transmission ion microscopy (STIM) can be carried out simultaneously. Data acquisition is carried out using a simple but flexible PC based system (Oxford Microbeams DAQ) and the data is analysed using a combined RUMP and GUPIX PC based interactive package (NUSDAN) acting under WINDOWS. Resolution tests using a calibration grid and a multi layer integrated circuit have shown the facility to be capable of 600 nm spot sizes for 2 MeV protons at currents suitable for microanalysis.

A new high energy implantation facility for materials research at the CRN, Strasbourg

A 5 MV implanter has been installed at the Centre de Recherches Nucléaires (CRN) of Strasbourg in collaboration with Vivirad-High-Voltage in the framework of the European Network on Ion Beam Processing of Semiconductors. This single-ended Van de Graaff is built using a new concept of discrete electrodes and is equipped with a microwave ion source. A first beam line with an electrostatic scanning device has been constructed. The end station containing a goniometric wafer holder is coupled with the 4 MV accelerator to allow in situ implantation and analysis by nuclear techniques. The possibility of low temperature operations and control is also available. The performance of the machine will be reported and applications in material modification and analysis will be described. Particular attention will be paid to effects of high energy implantation in semiconductors (range, defects, amorphization-recrystallization). Further developments and applications in other fields will be presented.

A new generation of single-ended Van de Graaff accelerators for ion implantation and ion beam analysis

High voltage Engineering Europa B.V., The Netherlands developed a new generation of single-ended Van de Graaff accelerators for ion implantation and ion beam analysis. The new HVEE Van de Graaff accelerators are equipped with a unique (patented) ion source exchange system capable of handling four lands of ion sources, mass separation at high voltage level and an X-ray intensity suppression system. The accelerators are able to produce a large variety of continuously, homogeneous and highly collimated mass-analyzed ion beams of several hundred μA in the energy range from 50 keV up to l MeV (l MV model) or from 100 keV up to 2 MeV (2 MV model), using singly charged ions, whereby the maximum energy can be easily reached and maintained without conditioning and virtually no X-rays are produced. Combined with two dedicated end stations (one for ion beam analysis using RBS, channeling, NRA and PIXE, and one with an automatic wafer-handling system for both single-wafer implantation and batch processing), these systems are very suitable for research as well as industrial applications.

Light heavy-ion and molecular beams from a radio-frequency ion source

A single ended Van de Graaff accelerator fitted with a radio-frequency ion source of probeless extraction geometry has been tested as a source of light heavy-ion and molecular beams in different charge states. It has been proved in Rutherford scattering analysis of the magnetically resolved beam components that the high energy double charged beam is mixed with a beam of low energy molecular fragments of the same momentum. Conclusions are drawn on how such sources can be applied in ion-atom collision physics and nuclear microanalysis.

IBA using a small tandem and a single-ended Van de Graaff

Using an NEC 5SDH-2 tandem and an upgraded KN-4000 single-ended Van de Graaff machine we are investigating the depth profiles of 1,2H, 4He and 6,7Li which have been implanted or dispersed into silicon wafers, SiO2/Si, SiO2/magnetic bubble garnet, soda-lime glass and stainless steel. The tandem is used to generate an 8 MeV 16O beam for ERD measurements of these light elements and also a 15N4+ beam for profiling hydrogen by means of the 1H(15N, αγ)12C reaction. The Van de Graaff has a maximum terminal voltage of 4.75 MV and accelerates 15N2+ ions for 1H profiling and 3He+ ions for highly sensitive 2H measurements by means of the 2H(3He, pα) reaction. An RBS investigation is running instead of PIXE experiments which have been terminated some years ago. We are using two types of homemade cold-cathode Penning-type ion source (PIG). The one has a side-extraction design for the tandem, and the other is an end-extraction source for the Van de Graaff. Owing to very low gas consumption, both sources are suitable for generation of ions of expensive isotopes such as 3He and 15N. We will report the experience with IBA using both types of electrostatic machines.

Beam-envelope calculations of space-charge loaded beams in MeV dc ion-implantation facilities

MeV dc ion accelerators are being developed that can deliver a beam current up to several hundred micro-amperes. At the low-energy part of the accelerator, the beam transport is space-charge dominated rather than emittance dominated. A system of differential equations has been derived, based on the Kapchinski-Vladimirski equations, which describe the envelope of a space-charge loaded ion beam, taking a longitudinal electrical field in an accelerating tube into account. The equations have been used to design the accelerator of a high-current 1 MV heavy-ion implantation facility. Furthermore, the design of a 2 MV accelerator is presented, which is used for analyzing techniques such as RBS and PIXE. Both facilities are based on single-ended Van de Graaff accelerators.

The University of North Texas Ion Beam Modification and Analysis Laboratory

The University of North Texas Ion Beam Modification and Analysis Laboratory consists of three accelerators. These are: a 200 kV, 10 MA Cockcroft-Walton, a 2.5 MV single-ended Van de Graaff machine and a newly installed National Electrostatics Corporation Model 9-SDH-2, 3 MV tandem. The tandem accelerator was received in November of 1987 and acceptance tests were completed in December of 1987. The tandem — and the 2.5 MV Van de Graaff — are now both installed in a new 7000 ft 2 laboratory in the physics building. The tandem which will be used for many of the activities in the laboratory was purchased with a rf charge exchange (Alphatross) source and a SNICS-type cesium ion sputter source. Each of these sources injects through a 30° magnet into a 90° analysis magnet and then into the tandem accelerator. This configuration gives the high mass resolution which is needed for the AMS system. A table will be shown that overviews the analyzed beams that have been obtained to date with the tandem accelerator. A summary of the beam lines that are being constructed for all the activities of the laboratory will also be given. These include: accelerator mass spectrometry (AMS), nuclear reaction analysis (NRA), Rutherford backscattering and channeling (RBS&C), particle-induced X-ray emission (PIXE), high-energy ion implantation (HEII) and atomic collision physics.

High energy implantation: Present and future facilities

Accelerators of the tandem type are in common use for high energy ion implantation. The necessary charge exchange at two stages limits the maximum ion current to < 1 mA. A single ended Van de Graaff can deliver ion currents up to 1 mA. The time-consuming opening of the pressurized tank for ion source exchange or service has been avoided in our l MV HVEE accelerator by a high-pressure load lock. This adapted version of the Van de Graaff accelerator is now in use for MeV implantation in semiconductors and metals. Future facilities requiring higher ion energy and more beam current are likely to use rf instead of dc acceleration. After the successful operation of a 115 kV so-called MEQALAC accelerator, a prototype multiple beam 1 MeV rf accelerator is under construction at our Institute. Dc type and different rf accelerators like RFQ, variable phase linac and MEQALAC are compared. MEQALAC is an acronym for a rf linac with electrostatic focusing and with multiple beams.

Multiply-charged heavy ion beams from a “Dirty bottle” ion source in a single-ended Van de Graaff

With only simple modifications, standard rf ion sources can be used in single-ended accelerators to produce useful currents of argon beams of charge up to + 5. If the ion source bottle is dirty from previous use, multiply-charged ion beams of the contaminants are also observed in useful quantities with pure argon as the source gas, although they may interfere with control of the machine on the argon beams.