New Technologies for Microanalysis and Element Imaging in THJ Scanning Electron Microscope

Abstract

Application of silicon drift detector in PIXE tomography system of Fudan University

ZnO is an essential material used in various devices, but its performance can be significantly enhanced by introducing or removing defects, such as oxygen and zinc vacancies. In this article, we explore the relationship between different types of defects in pure and Al/Ga-doped ZnO and their corresponding optical and electronic properties, which are vital for X-ray detection. The nanoparticles were initially synthesized using the sol-gel auto-combustion method, with calcination temperatures of 400 °C, 500 °C, and 600 °C. The samples were then analyzed using multiple techniques, including XRD, FESEM, FTIR, photoluminescence (PL), electron paramagnetic resonance (EPR), and positron annihilation lifetime spectroscopy (PALS). Subsequently, DFT+U calculations were conducted to examine the electrical, optical, and theoretical EPR properties, as well as to identify defects that occur at different calcination temperatures. Analyzing the connection between defects and PL spectra in X-ray scintillation detectors, along with exploring the relationship between electron and hole concentrations in X-ray semiconductor detectors, provides valuable insights into the fundamental properties of ZnO. These insights pave the way for utilizing ZnO in developing next-generation scintillation and semiconductor X-ray detection technologies.

Si(Li) and Ge Energy Dispersive Spectroscopy (EDS) detectors are commonly used for x-ray microanalysis because they are easy to use, inexpensive to operate, and offer both rapid qualitative evaluation of chemical composition and accurate quantitative analysis. Unfortunately, they are limited by energy resolutions on the order of 100 eV, which is insufficient to resolve many important overlapping x-ray peaks in materials of industrial interest, such as the Si Kα and W Mα peak overlap in WSi2. Although WDS spectrometers with excellent energy resolution (typically 2 eV to 10 eV) can resolve most peak overlaps, qualitative WDS analysis is limited by the need to serially scan over the entire energy range using multiple diffraction crystals. There is a need for a new generation of x-ray spectrometers for microanalysis that combines the excellent energy resolution of WDS spectrometers with the ease of use and the parallel energy detection capability of EDS spectrometers.We are developing a high-energy-resolution x-ray microcalorimeter spectrometer for use in x-ray microanalysis. Our microcalorimeter spectrometer consists of a superconducting transition-edge microcalorimeter cooled to an operating temperature of 100 mK by a compact adiabatic demagnetization refrigerator mounted on a SEM column, read-out SQUID (Superconducting Quantum Interference Device) electronics followed by pulse-shaping amplifiers and pile-up rejection circuitry, and a multichannel analyzer with real-time computer interface.

Optimal design of waveform digitisers for both energy resolution and pulse shape discrimination

Performance evaluation of newly developed SrI2(Eu) scintillator

The next-generation of neutrinoless double beta decay (0νββ) searches are targeting half-life sensitivities towards 1027–1028 years. Gaseous xenon time projection chamber (GXeTPC) detectors may be able to meet this challenge due to their excellent energy resolution and background rejection power through event visualization. This paper explores how the design choices of a next-generation GXeTPC time projection chamber can impact the overall performance of the experiment. We study the performance of systems using xenon enriched in the isotope 136Xe or natural xenon, focusing on scenarios that incorporate one tonne of 136Xe isotope. The detector size, copper shielding mass, energy resolution, density (using pressure at 293 K for convenience), and corresponding levels of diffusion are surveyed to evaluate the overall performance dependencies on these parameters. A detector optimized for using enriched xenon is preferred over natural, due primarily to a factor of 10 lower background rate driven by the large intrinsic backgrounds introduced by the copper shielding used in the detector. The performance of three types of gas TPC technologies was also explored based on different gas additives used to reduce diffusion to different levels. For all TPC technologies, we find background rates of a fraction of a count per tonne year in the region of interest are achievable. These performance levels are contingent on suitable energy resolution and event position placement in the drift direction being achieved for the specific detector technology. Performance for enriched xenon TPCs varies mildly with pressure in the range 5 to 25 bars, reaching background levels below 0.2 events/tonne-year. Performance at one bar is worse by approximately a factor of four. When considerations for the construction of the detector in addition to the selection performance are included, there may be no clearly optimum pressure.

Fabrication and characterization of cubic SrI2(Eu) scintillators for use in array detectors

Scintillators are important materials for radiation detection applications such as homeland security, geological exploration, and medical imaging. Scintillators for nuclear nonproliferation applications in particular must have excellent energy resolution in order to distinguish the gamma-ray signatures of potentially dangerous radioactive sources, such as highly enriched uranium or plutonium, from non-threat radioactive sources such as radioactive tracers used in medical imaging. There is an established need for scintillators with energy resolution in the 1-2% range at 662 keV. However, there are challenges surrounding the development of this new generation of high light yield/high resolution scintillators; for example, the high cost of production due to low crystal yield and slow growth process, and crystal inhomogeneity. We will discuss efforts focused on developing recently discovered high performance scintillators K(Sr,Ba)2I5:Eu, Cs4(Ca,Sr)I6:Eu and Cs2Hf(Cl,Br)6 that have potential for meeting nuclear security needs. Growth parameters for these materials have been optimized, allowing the growth of excellent quality single crystals measuring up to one-inch in diameter via the vertical Bridgman technique at translation rates between 1 and 5 mm/h. These scintillators materials have excellent properties with light yields between 30,000 and 120,000 ph/MeV, and energy resolutions between 2.3 and 4.6% at 662 keV.

A silicon multi-cathode detector (SMCD) has been developed for microanalysis and x-ray mapping applications. The SMCD has a large active area (∼0.5 cm2), excellent energy resolution, and high count rate capability. The detector utilizes novel structures that have produced very low dark current, high electric field, uniform charge collection, low noise and high sensitivity to low energy x-rays. The detector's spectral response was evaluated using a 55Fe radioisotope source, as well as by fluorescing materials with an x-ray generator. Figure 1 shows a 55Fe spectrum with an energy resolution of 125 eV FWHM at 5.9 keV collected at 12 μs peaking time. This energy resolution has been repeatably measured on many different detectors. To evaluate the high count rate x-ray performance, which is very important for fast x-ray mapping, a Cu sample was fluoresced using a Rh-anode x-ray tube.

The basic purpose of the x-ray trace element analytical techniques is to detect with high sensitivity elemental constituents of the target (including elements in trace amounts) and determine quantitatively the elemental composition of the investigated sample. These techniques are based on the detection of x-rays following the atomic inner shell ionization. An inner shell (core) electron can be removed from the atom in different ways, for the analytical purposes x-ray absorption and proton scattering are most commonly used. In the case of X-Ray Fluorescence (XRF) method the x-ray tube is usually applied to irradiate the sample while in the case of Proton Induced X-ray Emission (PIXE) the proton beam accelerated by the electrostatic accelerator to typical energy of MeV is used to ionize the target atoms. The atom with a hole in the inner shell (core hole) is extremely unstable with characteristic lifetime in the order of 10-15 s. Consequently, the inner shell ionization is followed via subsequent x-ray or Auger electron emission. Both, PIXE and XRF method exploit the radiative decay channel. The energy of the emitted x rays is given by the energy difference of the electron states involved in the transition which is characteristic of the target element atomic number. In order to identify the elemental composition of the target, energy analysis of the emitted radiation is required with energy resolution high enough to resolve characteristic spectral contributions from different elements in the sample. Such resolution is achieved by the energy dispersive solid state detectors in which electric signals are proportional to the incident x-ray energy and they are commonly used in x-ray trace element analytical techniques. Besides good enough energy resolution they also provide an excellent efficiency, which is crucial to collect weak signals from trace elements in the sample. It was in fact the development of the semiconductor detectors in the seventies that has triggered the development of x-ray analytical techniques. Today both PIXE and XRF techniques being a multi-element, sensitive, fast, non destructive and relatively inexpensive, have established as a routine analytical tool in a variety of fields such as material analysis, environmental and biomedical research, archeological and art studies,... However, in some special cases the energy resolution of solid state energy dispersive detectors, nowadays reaching the order of 130 – 150 eV for the x-ray energies of few keV, is not enough and significantly higher energy resolution is required to enhance the analytical capabilities of the x-ray techniques. In order to increase further the energy resolution of x-

A compact high resolution pair spectrometer for photons at intermediate energies

The physics reach and feasibility of the Future Circular Collider are currently being investigated in the form of a Conceptual Design Report. The ultimate goal is to collide protons with a centre-of-mass energies of 100 TeV, thus extending the reach of the current HEP facilities. This high-energy regime opens new opportunities for the discovery of physics beyond the standard model, but also new constraints on the detector design. As at 100 TeV a large fraction of the W, Z, H bosons and top quarks are produced with a significant boost, it implies an efficient reconstruction of high energetic objects. The reconstruction of those boosted objects sets the calorimeter performance requirements in terms of energy resolution, containment of highly energetic hadron showers, and high transverse granularity. The detectors designed for the FCC experiments need to tackle harsh conditions of the unprecedented collision energy and instantaneous luminosity. They also must be able to deal with a very high number of collisions per bunch crossings (pile-up). Excellent energy and angular resolution, also for low energetic particles, is therefore needed in order to meet the demands based on the physics benchmarks like Higgs self-couplings. We present the current baseline technologies for the calorimeter system of the FCC-hh reference detector and present first results of the performance studies with the combined calorimeters, meeting the energy resolution goal.

Large area avalanche photodiodes in scintillation and X-rays detection

Superconducting tunnel junctions in use for X-ray detection ale expected to produce an excellent energy resolution. An inclusive model is employed to give an overview of the detector characteristics. This method is devised to implicitly take properties of superconductor materials into account. With introducing an empirical relationship between junction parameters, the detector characteristics such as signal magnitude and energy resolution are reproduced to an acceptable degree. This method gives a helpful suggestion for understanding the detector performance such as a Fano-like factor, and may also serve as a guide line for designing tunnel junctions.