Lund Ion Beam Analysis Facility Research Articles

Modification of spray-deposited CdO thin films by 1.5 MeV proton irradiation

Thin films of cadmium oxide (CdO) with different thicknesses in the range of 78–250 nm were prepared and deposited on glass substrates by using a spray pyrolysis technique. A microbeam facility (Lund Ion Beam Analysis facility) was used to irradiate the prepared CdO thin films with a 1.5 MeV proton beam for fluence in the range of 2 × 1012–2 × 1014 ions/cm2. The surface morphology of the CdO films was measured by atomic force microscopy, and it was observed that the grain size and surface roughness were increased as a function of ion fluence. A UV spectrophotometer was used to study the optical properties of the samples, and the results revealed that the absorbance and optical band gaps increased with an increase in the proton fluence and CdO film’s thickness. This work explores the possibility of CdO material modification using low-energy proton irradiation.

One detector, all the light elements – Low-background NRA, RBS and ERDA for the quantification of elements from hydrogen to fluorine

Presented is a review of the accomplishments, of the light-element program, conducted at the Lund Ion-Beam Analysis Facility. A detailed account is given of the current experimental setup at the total Ion-Beam Analysis Chamber, which is equipped with two Double-Sided Silicon Strip Detectors for charge particle detection, a silicon drift detector for PIXE analysis, an electrostatic deflection system for charge measurement and implements a Nuclear Micro-Probe. A summary of the work conducted to date on the quantification of low Z elements is presented on a case by case basis. Details of the current work efforts and an overview of the advances which are intended in the near future are given.

Automating the setup and control of the pre-sample charge measurement system at the Lund Ion-beam Analysis Facility

In many IBA applications the aim is to obtain quantitative figures characterising the sample, usually requiring a reliable measurement of the beam current for normalisation. To avoid the drawbacks associated with on-sample and post-sample charge measurement systems a pre-sample measurement system can be used.In this work an upgrade to the pre-sample charge measurement system at the Lund Ion-beam Analysis Facility is presented, in which a custom built control module based around a Teensy 3.2 micro-controller has been added to the existing system. The new control module allows for remote handling and monitoring of the deflection system, operated via USB connection to a PC running a graphical user interface. Details of the control modules functionality, design and programming are given, as well as the functionality of the user interface. An example of how the new control module can be used for automated calibration of the deflection system is also presented.

Lithium analysis using a double-sided silicon strip detector at LIBAF

Quantification and mapping possibilities of lithium in geological material, by Nuclear Reaction Analysis (NRA), was evaluated at the Lund Ion Beam Analysis Facility (LIBAF). LiF and two Standard Reference Materials, (SRM 610 and SRM 612) were used in the investigation. The main part of the data was obtained at the beam energy 635keV studying the high Q-value reaction 7Li(p, α)4He, but reaction yield and detection limits were also briefly investigated as a function of the energy. A double-sided silicon strip detector (DSSSD) was used to detect the α-particles emitted in the reaction in the backward direction. The combination of the high Q-value, a reasonably good cross-section and the possibility to use a high beam current have been demonstrated to allow for measurement of concentrations down below 50ppm. Proton energies below 800keV were demonstrated to be appropriate energies for extracting lithium in combination with boron analysis.

A nuclear geochemical analysis system for boron quantification using a focused ion beam

Ion beam analysis has for decades been used as a tool for geochemical analysis of trace elements using both X-rays (particle induced X-ray emission) and nuclear reaction analysis. With the geoanalytical setup at the Lund Ion Beam Analysis Facility, the boron content in geological samples with a spatial resolution of 1 µm is determined through nuclear reaction analysis. In the newly upgraded setup, a single detector has been replaced by a double sided silicon strip detector with 2048 segments. After optimization, boron content in geological samples as low as 1 µg g−1 can be measured.

A tailored 200 parameter VME based data acquisition system for IBA at the Lund Ion Beam Analysis Facility – Hardware and software

With the recent advances towards modern Ion Beam Analysis (IBA), going from one- or few-parameter detector systems to multi-parameter systems, it has been necessary to expand and replace the more than twenty years old CAMAC based system. A new VME multi-parameter (presently up to 200 channels) data acquisition and control system has been developed and implemented at the Lund Ion Beam Analysis Facility (LIBAF).The system is based on the VX-511 Single Board Computer (SBC), acting as master with arbiter functionality and consists of standard VME modules like Analog to Digital Converters (ADC’s), Charge to Digital Converters (QDC’s), Time to Digital Converters (TDC’s), scaler’s, IO-cards, high voltage and waveform units. The modules have been specially selected to support all of the present detector systems in the laboratory, with the option of future expansion. Typically, the detector systems consist of silicon strip detectors, silicon drift detectors and scintillator detectors, for detection of charged particles, X-rays and γ-rays.The data flow of the raw data buffers out from the VME bus to the final storage place on a 16 terabyte network attached storage disc (NAS-disc) is described. The acquisition process, remotely controlled over one of the SBCs ethernet channels, is also discussed. The user interface is written in the Kmax software package, and is used to control the acquisition process as well as for advanced online and offline data analysis through a user-friendly graphical user interface (GUI). In this work the system implementation, layout and performance are presented. The user interface and possibilities for advanced offline analysis are also discussed and illustrated.

Radiation tolerance of ultra-thin PIN silicon detectors evaluated with a MeV proton microbeam

A focused MeV proton beam at the Lund Ion Beam Analysis Facility has been used to induce radiation damage in transmission semiconductor detectors. The damage alters the response of detectors and degrades their charge transport properties. In this work, the radiation tolerance of ultra-thin silicon PIN detectors was studied as a function of proton fluences and detector thickness using a scanning proton microprobe. The investigated detectors had thicknesses ranging between 6.5 and 22μm, and different selected regions of each detector were irradiated with fluence up to 2×1015protons/cm2. The results show that the charge collection efficiency (CCE) decreases as a function of the proton fluence. Compared with non-irradiated regions, the CCE was above 94% at the lowest fluence of 2×1012protons/cm2 for all the detectors studied. Degradation of the devices caused spectral peak shifting toward lower energies. The highest possible fluence of 2.55MeV protons that could be used, causing only minor radiation damage, was 2×1013cm−2 for the thinnest detectors (6.5 and 10μm) and 2×1012cm−2 for the thickest detectors (15 and 22μm).

Preliminary results of oxygen isotope ratio measurement with a particle-gamma coincidence method

The possibility to study variations in the oxygen isotopic ratio with photon tagged nuclear reaction analysis (pNRA) is evaluated in the current work. The experiment described in the article was performed at Lund Ion Beam Analysis Facility (LIBAF) with a 2MeV deuteron beam.Isotopic fractionation of light elements such as carbon, oxygen and nitrogen is the basis of many analytical tools in hydrology, geology, paleobiology and paleogeology. IBA methods provide one possible tool for measurement of isotopic content. During this experimental run we focused on measurement of the oxygen isotopic ratio. The measurement of stable isotopes of oxygen has a number of applications; the particular one driving the current investigation belongs to the field of astrogeology and specifically evaluation of fossil extraterrestrial material.There are three stable isotopes of oxygen: 16O, 17O and 18O. We procured samples highly enriched with all three isotopes. Isotopes 16O and 18O were easily detected in the enriched samples, but no significant signal from 17O was detected in the same samples. The measured yield was too low to detect 18O in a sample with natural abundances of oxygen isotopes, at least in the current experimental setup, but the spectral line from the reaction with 16O was clearly visible.

Deuterium/hydrogen microscopy in astrogeological material using an elastic recoil approach

A new experimental setup for quantitative hydrogen isotopic-ratio microscopy in thin samples (up to 12μm) is under development at the Lund Ion Beam Analysis Facility. This technique is derived from the proton–proton scattering technique and has been proven to have the same beneficial features, namely a detection limit below 1wt-ppm and a depth resolution better than 1μm. The method gives absolute quantitative information about H or D content in atoms per cm2 and does not depend on the structure, chemical environment or other so called “matrix effects”. This work presents an evaluation of the developed technique through measurements on unique material from samples from the Tagish Lake meteorite, which has been suggested to be one of the most primitive solar system materials yet studied. We discuss the capabilities of the technique through the results from measurements on a geological standard.

Efficient ultra-thin transmission silicon detectors for a single-ion irradiation system at the Lund Ion Beam Analysis Facility

This paper describes the fabrication of efficient ultra-thin silicon transmission detectors for use as pre-cell detectors in single-ion experiments on living cells at the Lund Ion Beam Analysis Facility. More than 40 detectors of different thicknesses down to 5 μm have been fabricated and packaged. The main design considerations were very low leakage current (below 9 nA) and low full depletion voltage at biases less than 0.5 V at room temperature. In addition, we have shown that cooling the device can reduce the leakage current to 3 nA. The experimental testing of the pre-cell detection system is based on counting the passage of ions through the transmission (ΔE) detector before hitting the stopping (E) detector placed behind it, to ensure the accurate delivery of specific doses of radiation to the sample. Optimal detection of the fabricated detectors for the passage of an external beam of 2.2 MeV protons was obtained by cooling the device to below 2°C. Cooling the ΔE detectors provides up to 20% better energy resolution and up to 98% detection efficiency for 2.2 MeV protons. The development of this kind of efficient pre-cell detector enables a range of new experiments to be conducted on thick biological samples.

A decade’s worth of otolith PIXE analyses

Over the past 10 years, several thousand otoliths have been analyzed with PIXE (using 2.55 MeV protons) at LIBAF (Lund Ionbeam Analysis Facility, formerly LNMP Lund Nuclear Micro Probe). Over 40 elements have been identified in otoliths, many at levels suitable for PIXE analysis. Readily detectable elements in otoliths starting with Ca are: Ca (the matrix), Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Br, Sr, Y, Zr, Mo, Cd, Sn (difficult), I, Ba (sometimes difficult), Pb (difficult). The detector system, used over this time period, is more sensitive than many other X-ray detector systems, since it consists of eight HPGE detector elements (100 mm2 each), in an annular formation around the beam entrance. Using a thick absorber allows us to use quite high beam current, typically 12 nA, but sometimes up to 20 nA. This permits us to have low detection limits within short analysis times. Additionally, light stable isotope research is widespread in the sciences including ecology. Stable isotopes of N provide information about trophic level (“who eats who”), providing the opportunity to map out the switching of diets from one food type to another. Oxygen isotopes are useful as “environmental thermometers”. Currently, most of such analyses require destruction of the otolith, and nitrogen isotope analysis may require dissolving entire otoliths, thus losing all temporal information. We present new techniques using new types of detectors, double side silicon strip detector (DSSSD). The detectors, electronics and the laboratory setup are described in detail; for our analysis, a MeV proton and a deuterium microbeam at LIBAF is used. The analysis is performed immediately after the PIXE analysis, without moving the sample.

Characterizations of new ΔE detectors for single-ion hit facility

This paper describes the performance evaluation of new ΔE detectors to be used as pre-cell hit detectors in living cell irradiation experiments at the Lund Ion Beam Analysis facility (LIBAF). Using these detectors with a thickness down to 4.15μm fabricated at Lund University, an experiment was setup in which ΔE-detectors were used together with a stop E-detector in a telescope system under coincidence measurements. The characteristics of ΔE detectors were based on the optimal detection of the passage of 2.55MeV protons. The results of these tests demonstrate that the detector telescope clearly separates the protons, this due to high signal-to-noise ratio and good energy resolution of the ΔE-detectors. The best performing detector was shown to have a detection efficiency of 95% at thickness of 9.7μm. This type of high-performing detector is suitable for the planned role of the ΔE-detector in the future cell irradiation experiments.

Hydrogen analysis and profiling with a position sensitive detector

The double sided silicon strip detector (DSSSD) is a segmented silicon detector commonly used in the fields of high energy physics and nuclear physics. This type of detector is used for analysis of reactions produced by charged particles. This makes it well suited for a number of analytical methods commonly used in ion beam analysis (IBA), such as Rutherford Backscattering (RBS) and elastic recoil detection (ERDA). One such detector was installed and tested at Lund Ion Beam Analysis Facility (LIBAF) recently. This is a modification to the existing setup used to measure hydrogen concentrations and depth profiles. When completed it will be used primarily for geological applications.Exact knowledge of the hydrogen content is important in a number of fields, but high enough accuracy can be difficult to achieve with most methods. In IBA normally some variant of ERDA, such as the proton–proton (p–p) coincidence method is used. We describe how the p–p coincidence technique was optimized to get the most out of our experimental setup. Previously this type of spectroscopy has been performed with two detector channels. In the present setup we expand that number from 2 to 96 channels, 64 on the front and 32 on the back of the detector. The intersecting strips give 2048 distinct detector elements or 1024 possible coincidences as dictated by the reaction kinematics. This increase in complexity requires a more detailed data analysis but it rewards us with higher sensitivity and a better background suppression.