| 1. |
- Auzelyte, Vaida, et al.
(författare)
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The beam blanking system for microlithography at Lund Nuclear microprobe
- 2004
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section B: Beam Interactions with Materials and Atoms. - : Elsevier BV. - 0168-583X. ; 219-20, s. 485-489
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Tidskriftsartikel (refereegranskat)abstract
- A new beam blanking system was installed at the Lund Nuclear Microprobe and employed in proton beam lithography (PBL) for polymer microstructures fabrication. The blanker consists of two parallel plates connected to a high voltage generator. Measurement of the beam blanking time on a sample was performed by means of the standard PIXE system. The beam is blanked and returns to a sample within 200 ns. The blanking system is designed for the new sub-micrometer beamline under installation in the accelerator laboratory. A number of pilot MeV ion beam lithography experiments were performed to illustrate the possibility to use the blanking system in combination with the existing data acquisition and scanning system. A 2.5 MeV proton beam was used to irradiate 50 mum SU-8 negative resist. The blanker was shown to be a necessary part of the lithography system. It enables blanking between each pixel and hence fabrication of various patterns down to a single pixel. The blanker has significantly simplified beam control and enhanced process time and spatial resolution. Three-dimensional microstructures with 20:1 aspect ratio were fabricated.
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| 2. |
- Kristiansson, Per, et al.
(författare)
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Development of a system for determination of the C-13/C-12 isotopic ratio with high spatial resolution
- 2004
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section B: Beam Interactions with Materials and Atoms. - : Elsevier BV. - 0168-583X. ; 219-20, s. 561-566
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Tidskriftsartikel (refereegranskat)abstract
- Stable carbon isotopes play an important role in the interpretation of biological activity, particularly when the fossil record is studied. In combination with morphological and chemical data, isotopic information can be useful in paleontology and astrobiology. In this paper the development of a microanalytical ion beam system for the measurement of the carbon isotope ratio with high spatial resolution and good statistics is presented. The technique used is elastic scattering of alpha particles with an energy of 2.75 MeV. At this energy the C-13 cross-section is enhanced relative to the Rutherford cross-section and while the C-12 cross-section is reduced. The optimisation of the system is described, including sample preparation and the design of the particle detection system for high efficiency combined with good energy resolution. Finally, some results from the initial test run of the system are shown and discussed. (C) 2004 Elsevier B.V. All rights reserved.
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| 3. |
- Pallon, Jan, et al.
(författare)
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An off-axis STIM procedure for precise mass determination and imaging
- 2004
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section B: Beam Interactions with Materials and Atoms. - : Elsevier BV. - 0168-583X. ; 219-20, s. 988-993
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Tidskriftsartikel (refereegranskat)abstract
- For the precise determination of the local mass density in thin samples analysed at the Lund Nuclear Microprobe, a modified version of off-axis STIM is described. An on-axis/off-axis geometry is used where a thin C-foil, placed behind the sample scatters protons into the particle detector. The advantage of this geometry compared to the off-axis case where particles are directly scattered from the sample into the particle detector is that the energy-loss spectrum acquired is less degraded. A spectral resolution comparable to on-axis STIM is achieved at a beam current high enough to allow for a simultaneous PIXE analysis (50-100 pA). (C) 2004 Elsevier B.V. All rights reserved.
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| 4. |
- Shariff, Asad, et al.
(författare)
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Characterization of a new large area HPGe X-ray detector for low beam current application
- 2004
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section B: Beam Interactions with Materials and Atoms. - : Elsevier BV. - 0168-583X. ; 219-20, s. 494-498
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Tidskriftsartikel (refereegranskat)abstract
- In the new sub-micron beamline at the Lund Nuclear Microprobe facility a special large area HPGe X-ray detector has been installed. It consists of eight 100-mm(2)-size detector elements arranged in an annular formation around the beam entrance hole. Different parameters like FWHM, FWTM, peak-to-background ratio and peak-to-valley ratio for each individual detector element as well as their sum spectra have been investigated. The data handling, i.e. how eight parallel signals are individually stored and summed together, has been discussed. The possibility to use the detector for simultaneous measurement of high and low energy photons, i.e. PINE combined with PIGE has been demonstrated. (C) 2004 Elsevier B.V. All rights reserved.
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| 5. |
- Shariff, Asad
(författare)
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Development of New Experimental Facilities at the Lund Nuclear Microprobe Laboratory
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Ion beam analysis techniques are now well established as research tools for a broad range of multidisciplinary scientific fields. The ability to focus an ion beam down to micrometer size has expanded and strengthened the capability of IBA techniques to a higher level. A new field “Nuclear microprobe (NMP) analysis” has been developed over the past decades, in which most IBA techniques are used and, in addition, a new group of imaging techniques has been developed. A high-resolution scanning nuclear microprobe can provide maps of distributions of elements with high sensitivity and can analyse very small structures. The power of NMP lies mainly in its lateral resolution (beam spot size) and the amount of current it can deliver on the target. So the quest for the smallest possible beam spot size with sufficient beam current is an active field of research. Even if the NMP has much more to offer, conventional IBA techniques are still suitable in some scientific fields of research, due to their simplicity and the shorter run times required. In this work two new beamlines have been designed and constructed at the Lund NMP laboratory. The first part of the thesis is based on the design and construction of a broad beam facility called “macro beamline” including the quantitative calibration of the PIXE set-up in this beamline. For a better performance and quantification with PIXE the peak tailing of the X-ray detector has been characterized. This beamline has subsequently been successfully used to analyse a large number of PIXE samples with a beam of millimetre size. The second part of the thesis describes the design and construction of a new sub-micron beamline, where a focused beam with sub-micron resolution is expected. In designing this beamline all the necessary parameters were carefully considered and a detailed theoretical investigation was done using computer code PRAM. A two-stage doublet configuration has been chosen as the focusing system based on these calculations. Our two-stage system is unique in that the first stage act as an independent microprobe. Experimentally, two of the key functions for a successful set-up, the four high quality magnetic quadrupole lenses and a special 8-element annular X-ray detector have been investigated and characterized. This large area X-ray detector will facilitate work with a much lower beam current. A large and flexible chamber, with sample stage movable with high precision and a optical viewing system of high magnification, has also been constructed. Special care has been taken to insulate the beamline and the chamber from vibration.
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| 6. |
- Shariff, Asad, et al.
(författare)
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Evaluation of low-energy tailing parameters of a HPGe X-ray detector to be used in GUPIX software library for PIXE analysis
- 2004
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section B: Beam Interactions with Materials and Atoms. - : Elsevier BV. - 0168-583X. ; 219-20, s. 110-114
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Tidskriftsartikel (refereegranskat)abstract
- Accurate description of the response function of X-ray detectors is important for quantitative PIXE analysis. For analytical description of low-energy tailing in PIXE spectra, the GUPIX approach was used, i.e. a combination of Hypermate type functions. The low-energy tailing parameters of a low-energy high purity germanium X-ray detector in the region 1.3-9.2 keV was determined by systematic fitting of X-ray spectra from thin MicroMatter standards. Except for the main Gaussian peak and germanium escape peaks, one shelf, one truncated shelf, one exponential function and KMM radiative Auger feature was applied to fit the spectral data collected with this low-energy Ge X-ray detector. The overall trend of different tail parameters shows similar characteristic as those for Si(Li) X-ray detectors used in this energy range, i.e. very strong tailing at low X-ray energies and a rapid fall off with increasing X-ray energy. The fitted parameters, as a function of X-ray energy, were then incorporated into the GUPIX library for PIXE analysis. (C) 2004 Elsevier B.V. All rights reserved.
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| 7. |
- Wegdén, Marie, et al.
(författare)
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Hydrogen analysis by p-p scattering in geological material
- 2004
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section B: Beam Interactions with Materials and Atoms. - : Elsevier BV. - 0168-583X. ; 219-20, s. 550-554
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Tidskriftsartikel (refereegranskat)abstract
- It has been concluded by geologists that a significant amount of hydrogen is stored as point defects in nominally anhydrous minerals. Determination of the amount of hydrogen bound in these minerals is a step towards determining the total water content of the earth mantle as well as comprehending its internal water cycle. The possibility to measure hydrogen in thin geological samples by elastic p-p scattering has been investigated at the Lund Nuclear Microprobe. In this work the development of the experimental procedure and standardisation of data analysis is described. Special emphasis has been put into doing the data analysis as simple as possible and at the same time applicable to all sorts of thin samples, even those of unknown nature. A special annular surface barrier detector composed of two insulated detector halves, which are read out simultaneously, is used to detect the recoiled proton and the scattered proton in coincidence. Conditions on the difference in time and energy of the detected particles, enables us to distinguish true hydrogen events from false or random ones. Homogeneous Mylar foils with known hydrogen content are used as reference material and enables determination of the total amount of hydrogen in the bulk of the geological samples as well as depth profiling, in order to separate contaminations in the surface front the bulk concentrations. The method has been tested with a 2.8 MeV proton beam on thin samples of both Muscovite, which is known to have a natural hydrogen concentration of about 0.5 wt%, and Pyroxene, which is a nominally anhydrous mineral.
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| 8. |
- Wegdén, Marie, et al.
(författare)
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Nuclear microprobe analysis of the selective boron uptake obtained with BPA in brain tumour tissue
- 2004
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section B: Beam Interactions with Materials and Atoms. - : Elsevier BV. - 0168-583X. ; 219-20, s. 67-71
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Tidskriftsartikel (refereegranskat)abstract
- The tumour selective ability of the boron compound boronophenylalanine (BPA), today used in Boron Neutron Capture Therapy in Sweden, has been investigated with the Lund Nuclear Microprobe. The tumour to tissue ratio of the boron concentration, as well as the location of boron within the cells, is critical for the efficiency of the therapy. It is desirable that the boron is accumulated as close as possible to the cell nucleus, since the alpha particles produced in the B-10(n,alpha)Li-7 reaction only have a range of about 10 microns, i.e. a cell diameter. The nuclear reaction B-11(p,alpha)2alpha, which has an especially high cross-section (300 mb) for 660 keV protons, has been used to analyse brain tissue from BPA-injected rats. Previous studies on other boron compounds have shown significant background problems when the alpha particles are detected in the backward direction. By a specially designed set-up, alpha particles in the forward and backward direction are detected simultaneously, and only the coincidences between the two directions are considered to be true boron events. In this way we could achieve excellent background suppression. The analysis shows that BPA indeed is tumour selective. Quantifications show a boron abundance of 150 +/- 20 ng/cm(2) in normal tissue and 567 70 ng/cm(2) in tumour tissue. If the rat is fed with L-dopa before the injection of BPA the uptake increases 3-4 times. The boron is homogeneously distributed in the cellular structure and no specific intracellular accumulation has been shown. (C) 2004 Elsevier B.V. All rights reserved.
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