One of the world's deepest underground liquefied petroleum gas (LPG) storage cavern projects has been built near the city of Visakhapatnam in India. Storage is based on the hydraulic containment principle using water pressure. This paper discusses the design aspects and various phases involved in construction. The general outline, significance of the facility and basic principles of storage are described, including the initial exploration works, complementary site investigations, basic engineering design and the design changes made during construction. Health, safety and environment as well as quality aspects are considered. The sequence and methods adopted to construct diaphragm walls for the foreshafts, sinking for the rock shafts, installation of the water curtain tunnel and excavation for the main storage cavern are described. The scope and construction methodologies are explained and the challenges and complexities of the underground project, a first for south Asia, are considered. Achievements and areas where there is scope for improvements are discussed. Finally, the advantages of such projects, critical success factors and special issues needing attention are presented.

6H-silicon carbide (SiC) schottky diodes were irradiated at room temperature (RT) with proton, alpha and carbon particles to fluences in the range of 108–1013 ions/cm2. Both radiative and non-radiative traps are generated due to damage caused by the incident ions. Ionluminescence performed at RT revealed that radiative traps with photon emission energy of 2.32 eV appear after radiation. Electroluminescence measurement indicated that at RT the influence of non-radiative defects dominated over the radiative ones. Ion beam induced charge collection was used to investigate the charge collection efficiency of these diodes. Reduction in the charge pulse height is compared with calculation of non-ionising energy loss (NIEL). NIEL is a good measure of the displacement damage introduced in SiC materials by ionising particles. There is no significant difference in the radiation hardness of n-type and p-type 6H-SiC schottky diodes when irradiated with 2 MeV alpha particles.

The high-energy ion nanoprobe LIPSION at the University of Leipzig has been operational since October 1998. Its magnetic quadrupole lens system, arranged as a separated Russian quadruplet, has been developed by the Microanalytical Research Centre (MARC), Melbourne. The ultrastable single-ended 3.5 MV SINGLETRON™ accelerator (High Voltage Engineering Europa) supplies H+ and He+ ion beams with a beam brightness in the range of 10–20 Arad−2m−2eV−1 [D.J.W. Mous, R.G. Haitsma, T. Butz, R.-H. Flagmeyer, D. Lehmann, J. Vogt, Nucl. Instr. and Meth. B 130 (1997) 31]. Due to this high brightness, the excellent optical properties of the focusing system of the nanoprobe and the suppression of mechanical vibrations, lateral resolutions of 100 nm for the low current mode (STIM) and 340 nm at a current of 10 pA (PIXE, RBS, SEI modes) were achieved. Further improvements are expected.

Molecular hydrogen ions were first used in nuclear microprobe STIM imaging to enhance contrast. These beams have also been used for PIXE and other techniques of microprobe imaging, although the high-energy electrons associated with the molecules caused problems with charge integration. This paper discusses the use of asymmetric molecular ion beams, to utilise the properties of molecular break-up for enhanced materials analysis. In particular the use of the deuterium-hydrogen (DH+) molecule for STIM imaging to provide increased image contrast and improved density measurement for specimens of widely varying areal densities is discussed.

Trace element contamination and other defects trap photo-induced charge in photovoltaic materials and devices. With few exceptions, trace elements have a strongly degrading influence on device performance at concentrations below the minimum detectable limit for even the most sensitive ion beam analytical techniques. However, grain boundaries in polycrystalline silicon solar cells may getter trace impurities from surrounding grains and may achieve detectable concentration levels. By combining Proton Induced X-ray Emission (PIXE) to image impurities with Ion Beam Induced Charge (IBIC) to image the charge collection efficiency the existence of spatial correlations between impurity distributions and charge collection efficiency may be investigated. Using these methods we find that the distribution of impurities in a commercial polycrystalline solar cell suggests a correlation between some elements and the variations in charge collection efficiency.

 The radiation hardness of diode array devices based on silicon on insulator technology and bulk technology was investigated. The devices were exposed to 24 GeV/c protons (at CERN) up to a fluence of 4.1 10 13 p/cm. Charge collection following irradiation indicated a significant reduction in minority carrier lifetime. The damage constant was calculated using alpha particle spectroscopy methods. These experiments demonstrate that such a device has sufficient radiation hardness to be used in medical radiation oncology applications as a microdosimeter.

A nuclear microprobe, with a focused MeV ion beam, may be used to perform microchanneling measurements on small crystals less than 50 μm in diameter. Information can be provided that is difficult to obtain by other techniques. The measurements can be used to provide information about the crystal structure and orientation. Also, the crystal quality and lattice location of dopants can be measured. One barrier to more widespread application of the technique is that the small size of the crystal imposes stringent restrictions on the amount of lateral movement tolerable as a crystal axis is tilted into alignment with the analysis beam. Two novel techniques for overcoming this problem are discussed and contrasted here. Both techniques involve angular scanning of the ion beam.

The assessment of mechanisms for radiation damage in both biological and semiconductor systems is much enhanced by ensuring that each cell or memory unit is hit by one and only one ion. Such "single ion" systems operate by detecting the passage of an ion and using the signal to deflect the beam upstream thus ensuring that only a single ion is injected to the system at a time. For biological investigations of the effects of single ion impact on living cells, the ion needs to be extracted from the vacuum of the accelerator through a thin window into the atmosphere. The requirements on such a window are: (a) that it be thin enough to allow the passage of the ion through it without excessive energy loss; (b) that it possess mechanical strength sufficient to survive the pressure differential; and (c) that upon passage of the ion through it, a sufficiently large signal is generated to ensure a 100% efficient detection of the passage of the ion.This set of demanding requirements can be met by a thin diamond window fabricated by CVD technique, taking advantage of the high secondary electron yield of B-doped diamond. In the present work, we report on the use of B-doped diamond membranes for this purpose. (C) 1998 Elsevier Science S.A.

This paper presents some recent results in the investigation of MeV ion microprobe imaging techniques at the Micro-Analytical Research Centre MARC in Melbourne, Australia. In the first section we investigate the use of molecular hydrogen beams as tools for scattering contrast STIM imaging. The second section deals with the use of post-specimen scanning as a means of quantitatively imaging transmission channeling patterns.

A reconstruction technique to calculate accurate tomograms of a sample, at a voxel scale, from tomographic experiments that involve probe-sample interactions of any degree of complexity is proposed. The properties of the reconstruction technique that accomplish this are outlined. The first guess to the solution is calculated directly from the reconstructed experimental projection data. To improve the accuracy of the approximate solution at every iteration, projection data are calculated by simulating the tomographic experiment, rather than by using a projection matrix. Calculating the ratio of the reconstructed experimental projection data to the reconstructed simulated projection data provides correction factors at every voxel. The approximate solution is multiplied by these correction factors. This correction formulation is identical to that used in the image-space reconstruction algorithm technique. High spatial resolution and accurate solutions are achieved by not implementing any form of smoothing. Instead, a novel technique is used to reduce the noise in the tomograms substantially. We call this reconstruction technique the discretized image-space reconstruction algorithm. This reconstruction technique provides a means to calculate the mass density and elemental composition tomograms of microscopic samples properly, utilizing the wealth of information measured in scanning transmission ion microscopy and particle-induced x-ray emission tomography experiments. To demonstrate the efficacy of this reconstruction technique, examples of scanning transmission ion microscopy tomography experiments are presented.

The secondary electron emission from a 2 μm thick boron-doped diamond film under ion (4.6–7.7 MeV He+)impact is reported. The yield under ions impact is found to be remarkably high, stable over a period of many months, and independent of which side of the film (i.e., growth or substrate side) is exposed to the ion flux. By taking advantage of the high secondary-electron yield, the passage of each ion through the film could be detected with an efficiency of close to 100%, which to the best of our knowledge is the highest efficiency recorded to date for any thin-film window. This finding has an immediate application in single-ion irradiation systems where a thin vacuum window is required to allow extraction of an ion beam from the vacuum into air and at the same time offer 100% efficiency for the detection of the passage of the ion through the window.

Diamond based detectors have potential applications in high energy physics experiments. These detectors can be fabricated from synthetic Chemical Vapour Deposited (CVD) polycrystalline diamond films. Previously it has been shown by the Turin group and their coworkers in Zagreb that it is possible to investigate the electrical characteristics of high quality polycrystalline CVD diamond films by Ion Beam Induced Current (IBIC). The present work describes IBIC images obtained using 2 MeV He+ irradiation of 250 μm thick polycrystalline diamond films through a thin gold surface contact layer biased positively relative to the grounded rear surface of the film. In contrast to previous experiments the present spectra of collected charge display a clearly defined peak from the induced charge. Images obtained by separating these spectra into different regions of interest allow the identification of regions in the sample of different charge collection efficiency. In particular the presence of some grains in which no charge collection appears possible and the reduction in charge collection efficiency at the grain boundaries is evident.

A new method for three dimensional tomographic analysis of micro-samples is presented. The technique is capable of accurately calculating the mass density and composition distribution of a sample, using the data measured from a STIM and PIXE tomography experiment. The technique solves for the effects of the energy dependence of the proton stopping-power and X-ray production cross-section. It also incorporates X-ray attenuation for a cone geometry between the sample and X-ray detector. A priori information about low Z elements is easily incorporated into the technique. The reconstruction of the mass density and composition of a phantom is shown.

The aim of this project is to develop a new system for single ion irradiation of cells for genetic and cell biology studies. This charged particle focused microbeam system will provide a fully computer controlled irradiation facility with submicron (subcellular) resolution and will open many new avenues into studies of radiobiological mechanisms. In the first stage of this project a system for single ion detection has been developed. A thin diamond window has been tested as vacuum/atmosphere window and as a possible source of secondary electrons and/or photons for single ion detection. A detection efficiency of 97% has been achieved.

Ions traversing a semiconductor material give rise to an e-h pair plasma whose interaction within the material and subsequent collection depends highly on the electronic properties of the material. The Ion Beam Induced Charge (IBIC) technique although allowing the imaging of both depletion and defect regions within a device gives little or no information regarding the timing of the charge collection process. Transient analysis on the other hand, particularly when combined with the IBIC, provides a more comprehensive study of the sample.

High dose N ion implantations into glassy carbon (GC) and diamond were performed at energies of 160 and 300 keV respectively. Target temperatures of the GC and diamond substrates were −100° C and room temperature respectively. Maximum N concentrations of 30 and 17 at.% were achieved for the GC and diamond respectively. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) revealed unusual surface modifications for both substrates.

Deep, high-aspect ratio trenches have been fabricated in the resist Polymethyl methacrylate by exposure to a focussed beam of MeV protons followed by development. The depth of the trenches depends on the energy of the protons and simulations suggest that this can be up to 300 μm. The University of Melbourne Microprobe is capable of producing a focussed spot size of the order of a few microns. This opens up the possibility of fabricating extremely high-aspect ratio microstructures for use as optical components.

This article will demonstrate the production and application of ‘‘mixed’’ beams for a magnetically focused nuclear microprobe. A ‘‘mixed’’ beam is defined as any two beams of ions of different species, or energy, or both that can be quickly and easily made to have the same magnetic rigidity (Rm) so that they transport, focus, and scan the same in a magnetic nuclear microprobe. Two techniques for the production of such beams will be presented. These methods include the extraction of different ions from the same source and scanning the terminal potential to produce the same Rm, and the use of a postacceleration stripper to change the charge state of one ion species to give it the same Rm as another ion species. The application of mixed beams to ion beam induced charge, scanning transmission ion microscopy, and ion microlithography will also be presented.

We are developing a laboratory and beam line control system. The MpControl system utilises all the flexibility and power of a computer network. Target stages, power supplies, Faraday cups, beam monitors, event counters, etc. can all be controlled by any of a number of computers in the laboratory. Software on each of these computers allows control, monitoring and display of the state of the beam line, accelerator and target manipulation stage. The entire system may be simultaneously controlled from any computer terminal on the network. The system has the potential to allow a user to manipulate the target stage from the beam control room, or to adjust accelerator parameters from the target chamber at the end of the beam line. The system has been designed to be easily transportable across computer platforms, currently with support for UNIX, X-Windows and MS-DOS. We believe this is a critical factor in a world of rapidly advancing computer and instrumentation hardware systems. The system has been designed to integrate with the MpSys data acquisition system.

There are many ways of imaging a specimen with a high velocity beam of focused ions, associated with the many ways in which the beam interacts with the specimen. There are other ways of imaging the specimen, utilizing other radiation. This multitude of images contains much information about the specimen and images may be combined. It is difficult to draw a line between imaging and quantitative analysis because, in general, the images are quantitative; but they may be influenced by properties of the specimen in many ways and thus carry additional information. This paper places the emphasis on the formation of the image and its information, resolution requirements, the meaning of beam resolution and the need for more information in the image. The emphasis throughout is on principles.