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An electrostatic quadrupole doublet lens system has been designed and constructed to provide strong, mass-independent focusing of 1–3 MeV ions to a 1 µm2 spot size. The electrostatic doublet consists of four sets of gold electrodes deposited on quartz rods that are positioned in a precision machined rigid frame. The 38 mm electrodes are fixed in a quadrupole doublet arrangement having a bore diameter of 6.35 mm. The coating process allows uniform, 360° coverage with minimal edge defects. Determined via optical interferometry, typical surface roughness is 6 nm peak to valley. Radial and coaxial alignment of the electrodes within the frame is accomplished by using a combination of rigid and adjustable mechanical supports. Axial alignment along the ion beam is accomplished via external manipulators. COMSOL Multiphysics® v5.2 and Propagate Rays and Aberrations by Matrices (PRAM) were used to simulate ion trajectories through the system.

There exists a critical need to understand the flow and accumulation of metallic ions, both naturally occurring and those introduced to biological systems. In this paper the results of fabricating thin film elemental biological standards containing nearly any combination of trace elements in a protein matrix are presented. Because it is capable of high elemental sensitivity, particle induced X-ray emission spectrometry (PIXE) is an excellent candidate for in situ analysis of biological tissues. Additionally, the utilization of microbeam PIXE allows the determination of elemental concentrations in and around biological cells. However, obtaining elemental reference standards with the same matrix constituents as brain tissue is difficult. An excellent choice for simulating brain-like tissue is Norland® photoengraving glue which is derived from fish skin. Fish glue is water soluble, liquid at room temperature, and resistant to dilute acid. It can also be formed into a thin membrane which dries into a durable, self-supporting film. Elements of interest are introduced to the fish glue in precise volumetric additions of well quantified atomic absorption standard solutions. In this study GeoPIXE analysis package is used to quantify elements intrinsic to the fish glue as well as trace amounts of manganese added to the sample. Elastic (non-Rutherford) backscattered spectroscopy (EBS) and the 1.734 MeV proton-on-carbon 12 C(p,p) 12 C resonance is used for a normalization scheme of the PIXE spectra to account for any discrepancies in X-ray production arising from thickness variation of the prepared standards. It is demonstrated that greater additions of the atomic absorption standard cause a viscosity reduction of the liquid fish glue resulting in thinner films but the film thickness can be monitored by using simultaneous PIXE and EBS proton data acquisition.

As high energy ions travel through a crystalline semiconductor materials they produce damage along the path which results in resistance to some of the wet chemical etching. A series of preliminary experiments have been performed at the Louisiana Accelerator Center (LAC) to examine the feasibility of irradiating high energy (keV–MeV) ions such as protons, xenon and gold through microscale masked structures on crystalline (n-type) Si substrates followed by wet chemical etch with KOH for attaining deep micromachining in Si. The results of these experiments are reported.

The new generation nuclear microprobe system at the Louisiana Accelerator Center in the University of Louisiana at Lafayette consists of a 6.25 m beam line that employs the magnetic quadrupole Sextuplet lens system. This Sextuplet is a zoom system having the same demagnifications, the same focal lengths and the same positions of the focal points in (xoz) and (yoz) planes as in the case for the Russian quadruplet, It also can have the same spherical aberrations in both planes. The parameters which allow obtaining the lowest coefficients of spherical aberration are found for different geometrical configurations of electric and magnetic quadrupole lenses. Specifically, the configuration of a combined Sextuplet consisting of two magnetic and four electrostatic lenses or consisting of two electrostatic and four magnetic lenses is studied and compared with magnetic and electrostatic Sextuplets. The values of the chromatic and spherical aberrations for these combined systems are compared and the minimum spot radius and the half-widths of the corresponding slits for some optimal magnetic and electrostatic Sextuplets are given. sponding for some optimal magnetic and electrostatic Sextuplets are given.

Deep buried layered microstructures have many potential applications as sensors, micro-electro-mechanical systems (MEMS), and optical devices, but it has always been challenging to obtain a minimum number of process steps to produce these structures. A single step ion irradiation process has been used to fabricate buried tunnels with 3 MeV P-beam writing by utilizing enhanced end-of-range damage in thick polymethylmethacrylate (PMMA). Creation of the buried tunnels in PMMA with a single energy irradiation step was found to be strongly dependent on the ion fluence and chemical developing process. The fabrication of a modular large scale complex pattern involving tunneled microstructures is presented as an example of this novel technique.

The high energy focused ion beam (HEFIB) system at the Louisiana Accelerator Center (LAC) of the University of Louisiana at Lafayette, Lafayette, USA, is constructed on one of the beamlines of a National Electrostatics Corporation 1.7 MV 5SDH-2 tandem accelerator. The HEFIB system has several components, including a versatile magnetic quadrupole sextuplet lens focusing system defined as the Russian magnetic sextuplet (RMS) system having the same demagnifications, the same focal lengths and the same positions of the focal points in xz and yz planes as the Russian quadruplet and a one-piece concrete supporting base and integrated endstation with air isolation. A review of recent microlithography and HEFIB system developments at LAC are presented, as well as new results using heavy ion (HI) beam lithography on crystalline silicon.

Energetic (MeV) Au implantation in Si(1 0 0) (n-type) through masked micropatterns has been used to create layers resistant to KOH wet etching. Microscale patterns were produced in PMMA and SU(8) resist coatings on the silicon substrates using P-beam writing and developed. The silicon substrates were subsequently exposed using 1.5 MeV Au3+ ions with fluences as high as 1 × 1016 ions/cm2 and additional patterns were exposed using copper scanning electron microscope calibration grids as masks on the silicon substrates. When wet etched with KOH microstructures were created in the silicon due to the resistance to KOH etching cause by the Au implantation. The process of combining the fabrication of masked patterns with P-beam writing with broad beam Au implantation through the masks can be a promising, cost-effective process for nanostructure engineering with Si.

The term “P-beam writing” is used to describe the technique of using focused high energy proton microbeams for micro or nanofabrication applications. The P-beam technique can be used to rapidly fabricate three-dimensional, high aspect ratio microstructures in a variety of materials without the use of masks and it is proving to be a versatile lithographic method. Recent developments in the application P-beam writing of microstructures at the Louisiana Accelerator Center are presented.

The main difference between quadrupole and axisymmetric charge particle beam focusing systems is that quadrupole systems do not produce a regular image of an object like axisymmetric systems. Because of the special symmetry in geometry and electric or magnetic fields along the axis, only the Russian quadruplet (RQ) can produce an image, however, for each geometry and given maximum field gradient of the RQ, the number of experimentally attainable focal distances in one system is limited to one or two. A new quadrupole focusing system with the same symmetry as the RQ is now under development at the Louisiana Accelerator Center that produces an image and has the possibility to vary the focal distance over a wide range by changing the excitation of the middle lenses. As a result, the magnification may be changed from 10−3 to 10+3 so that this versatile design can be adapted for several applications of high-energy focusing ion beam (HEFIB) systems, including nuclear nanoprobe, scanning microscope or transmission microscope. The configuration of this lens system consists of six quadrupole lenses and although these lenses can be combined either as magnetic (RMS) or electrostatic (RES) sextuplets, the Louisiana Accelerator Center is presently constructing an RMS system due to operational requirements. The zoom capability of the RMS is numerically investigated and the smallest beam spot size and appropriate optimal parameters of the RMS are presented for different emittances and compared with the corresponding parameters of the RQ.

Development of stable high brightness ion sources with accelerators will enhance the capabilities for micro-analysis as well as the micro-fabrication. Recently we have upgraded a Duoplasmatron ion source associated with a 1.7 MV tandem (NEC, Pelletron) accelerator to produce high brightness proton beam for nuclear microprobe application at the Louisiana Accelerator Center. This has substantially increased the ion source life time as well as the accelerator beam brightness. The beam brightness was found to be highly heterogeneous, with paraxial rays about an order of magnitude brighter than surrounding rays.

Once focused, the ion beam in a microprobe can be scanned over the sample by using a set of two orthogonal magnetic coils or electrostatic deflection plates positioned before, inside or after the focusing system. In the paper the influence of the scanner position on the beam spot shape is considered for different focusing systems such as triplet, quadruplet and sextuplet and for two different emittances of the beam. The numerous graphs show the dependence of the shape of the spot and the density distribution of the beam on the scanning radius.

A new quadrupole focusing system-magnetic sextuplet (RMS), with the same symmetry as the Russian quadruplet (RQ), has been proposed and is presently under development. The RMS has the same demagnifications and the same focal lengths as the RQ system and it can have the same spherical aberration in both planes. Its main feature, however, is the capability to change the demagnification over a wide range from 1 to greater than 1000 by changing the excitation of the middle lenses. In the RMS it is possible to obtain a point crossover between the middle lenses with a corresponding minimum sensitivity to the relative rotation of both triplets around the longitudinal axis. By changing the excitation of the middle lenses, the optimal demagnification for every emittance can be found and for every beam emittance it is possible to achieve a minimum spot size by varying the sizes of collimator diaphragms and the distance between them. All capabilities of the RMS are numerically investigated and the smallest beam spot size and appropriate optimal parameters of the system have been found for different emittances.

Until recently, it was difficult to measure properties of individual fluor grains. The development of an accelerator-based nuclear microprobe, as is currently available at the Louisiana Accelerator Center, has made this type of research possible. Using ion beams as small as 1 /spl times/ 1 /spl mu/m (horizontal /spl times/ vertical extent), it is now possible to measure properties of individual fluor grains. Starting in 2000, a research program was initiated to determine the microscopic fluorescence properties for selected rare earth compounds, like Y/sub 2/O/sub 2/S:Eu. Particle-induced X-ray emission (PIXE) was used to characterize individual fluor grains. Individual Y/sub 2/O/sub 2/S:Eu grains are clearly visible in the analysis and are less than 10 /spl mu/m in extent.

Most previous research measures fluorescence properties over the macroscopic regime. Properties of individual microscopic grains could be significantly different than those measured over the macroscopic scale. Until recently, it was difficult to measure properties of individual fluor grains. Existing characterization techniques like scanning electron microscopy are not practical, since the resulting fluorescence masks the electron surface profile. Starting in September 2000, a research program was initiated at the Acadiana Research Laboratory to determine microscopic fluorescence properties for selected inorganic rare earth compounds. The initial phase of this program utilized microscopic proton induced X-ray emission (μPIXE) to characterize the elemental composition of individual fluor grains. Results show that both individual grains and small clusters of grains could be seen using μPIXE. Maps of this type can be used to estimate grain dimensions for the selected rare earth fluor. This technique is a new and innovative method to characterize a fluor material.

Oxygen is known to be an important factor in reducing the corrosion rate of titanium, yet small amounts of oxygen on the titanium surface are practically undetectable by standard Rutherford Backscattering Spectrometry (RBS) analysis. The 3.05 MeV nuclear scattering resonance for 4 He + on oxygen was used in this study to show that surface oxygen is recoil-implanted by collisions with 1 MeV gold ions and produces a noticeable effect on corrosion test results.

An artificially coalified Taxodium peat was used to examine the behavior of inorganic constituents in terrestrial organic matter during the early coalification process. The artificial coal is produced by subjecting the peat to incremental increases in temperature up to 60 °C and pressures to 14.48 MPa over a four-week period in a partially open reactor. A standard polished thin section 30 μm thick is then cut from the resulting disk and examined using light microscopy to select and mark areas to be cut from the polished thin section. The distribution of inorganic constituents in these areas of the solid produced during the coalification process is then studied using nuclear microscopy. Results suggest that concentrations of inorganic constituents, including silicon, are lower in the newly produced solids than in the initial material. Distributions of other inorganic elements, including aluminum, sulfur, chlorine, potassium, calcium, barium and iron are also investigated.

The interest in assessing environmental pollution using tree ring analysis has increased in recent years. However, attempts to link metal deposition in tree rings to environmental pollution should be evaluated cautiously. In order to investigate the variation of the trace element distribution at two heights and two positions, four cores were extracted from a 60 year-old water oak (Quercus nigra). Experimental results show variations in the distribution of metals in different cores. These differences were not due to sample preparation, but possibly to differential deposition in the tree. The results indicate that caution must be exercised when attempting to link trace element studies of tree rings to pollution chronology of the surrounding environment.

A non-scintillating plastic sample in the form of a 6-μm-thin film was exposed to a 1-MeV proton beam at dosages ranging from 10 7 to 10 9 rad/cm 2 . The film was found to be luminescent when exposed to ultraviolet light. The intensity of the luminescence is a direct function of the damage to the film and there is no evidence of luminescence on unexposed regions. The luminescence increased to a maximum within 72 h after exposure and remained constant thereafter.

Au ions (900 keV) have been used to directly sputter etch microstructures in silicon, aluminum, copper and silver. The results presented clearly demonstrate that high energy heavy ions can be used to fabricate microstructures in selected metals and silicon in a single step process.