Solid-state Detector Array Research Articles

Muon track reconstruction in a segmented bolometric array using multi-objective optimization

Recent advances in segmented solid-state detector arrays for rare-event searches have allowed the technology to approach the ton-scale in detector mass and the scale of meters in size. Often focused around searches for neutrinoless double-beta decay or direct dark matter detection, such experiments also have the capability to search for exotic particles that leave track-like signatures across their volume. However, the segmented nature of such detector arrays often sets the spatial resolution and makes the problem of reconstructing track-like paths non-trivial. In this paper, we present an algorithm that improves reconstruction of track-like events in segmented detectors using multi-objective optimization — a computational technique that optimizes more than one cost function at a time without specifying a quantitative weighting between them. Such a technique allows the reconstruction of tracks through a detector and the determination of path-lengths through individual elements. When combined with the reconstructed energy depositions in each element this allows for a calculation of the stopping power of track-like particles and opens the door to searches for particles with abnormal stopping power like monopoles or lightly-ionizing particles (LIPs). Results are presented which evaluate the precision of the reconstruction tools as they currently stand against Monte Carlo generated data. The algorithm is presented in the context of the CUORE experiment, but has applications to other segmented calorimeter detectors.

Two-dimensional solid-state array detectors: A technique for in vivo dose verification in a variable effective area.

PurposeWe introduce a technique that employs a 2D detector in transmission mode (TM) to verify dose maps at a depth of dmax in Solid Water. TM measurements, when taken at a different surface‐to‐detector distance (SDD), allow for the area at dmax (in which the dose map is calculated) to be adjusted.MethodsWe considered the detector prototype “MP512” (an array of 512 diode‐sensitive volumes, 2 mm spatial resolution). Measurements in transmission mode were taken at SDDs in the range from 0.3 to 24 cm. Dose mode (DM) measurements were made at dmax in Solid Water. We considered radiation fields in the range from 2 × 2 cm2 to 10 × 10 cm2, produced by 6 MV flattened photon beams; we derived a relationship between DM and TM measurements as a function of SDD and field size. The relationship was used to calculate, from TM measurements at 4 and 24 cm SDD, dose maps at dmax in fields of 1 × 1 cm2 and 4 × 4 cm2, and in IMRT fields. Calculations were cross‐checked (gamma analysis) with the treatment planning system and with measurements (MP512, films, ionization chamber).ResultsIn the square fields, calculations agreed with measurements to within ±2.36%. In the IMRT fields, using acceptance criteria of 3%/3 mm, 2%/2 mm, 1%/1 mm, calculations had respective gamma passing rates greater than 96.89%, 90.50%, 62.20% (for a 4 cm SSD); and greater than 97.22%, 93.80%, 59.00% (for a 24 cm SSD). Lower rates (1%/1 mm criterion) can be explained by submillimeter misalignments, dose averaging in calculations, noise artifacts in film dosimetry.ConclusionsIt is possible to perform TM measurements at the SSD which produces the best fit between the area at dmax in which the dose map is calculated and the size of the monitored target.

PO-0901 2D solid-state array detectors: a technique for in-vivo dose verification at varying effective area

PO-0901 2D solid-state array detectors: a technique for in-vivo dose verification at varying effective area

Stress Distribution During Cold Compression of Rocks and Mineral Aggregates Using Synchrotron-based X-Ray Diffraction.

We report detailed procedures for performing compression experiments on rocks and mineral aggregates within a multi-anvil deformation apparatus (D-DIA) coupled with synchrotron X-radiation. A cube-shaped sample assembly is prepared and compressed, at room temperature, by a set of four X-ray transparent sintered diamond anvils and two tungsten carbide anvils, in the lateral and the vertical planes, respectively. All six anvils are housed within a 250-ton hydraulic press and driven inward simultaneously by two wedged guide blocks. A horizontal energy dispersive X-ray beam is projected through and diffracted by the sample assembly. The beam is commonly in the mode of either white or monochromatic X-ray. In the case of white X-ray, the diffracted X-rays are detected by a solid-state detector array that collects the resulting energy dispersive diffraction pattern. In the case of monochromatic X-ray, the diffracted pattern is recorded using a two-dimensional (2-D) detector, such as an imaging plate or a charge-coupled device (CCD) detector. The 2-D diffraction patterns are analyzed to derive lattice spacings. The elastic strains of the sample are derived from the atomic lattice spacing within grains. The stress is then calculated using the predetermined elastic modulus and the elastic strain. Furthermore, the stress distribution in two-dimensions allow for understanding how stress is distributed in different orientations. In addition, a scintillator in the X-ray path yields a visible light image of the sample environment, which allows for the precise measurement of sample length changes during the experiment, yielding a direct measurement of volume strain on the sample. This type of experiment can quantify the stress distribution within geomaterials, which can ultimately shed light on the mechanism responsible for compaction. Such knowledge has the potential to significantly improve our understanding of key processes in rock mechanics, geotechnical engineering, mineral physics, and material science applications where compactive processes are important.

A multichannel magneto-chiral dichroism spectrometer.

In this work, we describe a multichannel magneto-chiral dichroism spectrometer for the visible and near infrared wavelength ranges. The optical signal acquisition is based on commercially available Czerny-Turner spectrograph systems equipped with solid state detector arrays. The signal analysis method is based on post-processing phase sensitive detection, where the optical properties of the sample are modulated by an alternating external magnetic field. As an illustration of the performance of this spectrometer, magneto-chiral dichroism was measured in crystals of α - NiSO4 · 6H2O and good agreement with literature results was obtained.

Light emitting diodes: Light engines to simplify and economize advanced microscopy

THE old adage, ‘‘A picture is worth a thousand words,’’ is especially true in biological research, with microscopic images serving to mark the development of key concepts in biology since Hooke first described ‘‘cells’’ in thin slices of cork (1). More than 400 years later, microscopic imaging still serves as a primary data source for biological research, with increasingly advanced techniques that provide information on molecular scale interactions and dynamics. Such advanced molecular imaging techniques take advantage of ever more sophisticated light sources, optics, detectors, and image processing methods, many of which can be quite complex and expensive. At the same time, new technologies and production methods, many driven by the consumer market, have resulted in key components of imaging systems becoming smaller, simpler, and cheaper. The convergence of these effects is having profound effects on our options for light sources for microscopic imaging. The properties of the illumination source are critical to many advanced optical microscopy methods. Lasers play a key role in many of these owing to the monochromatic and coherent nature of their light, plus their ability to be pulsed and otherwise controlled. However, illumination with high-pressure mercury gas discharge or xenon lamps is still the standard for most imaging applications. These light sources provide bright, broad-spectrum excitation (300–900 nm) that can be easily selected by excitation filters for fluorescent imaging applications. However, there are quite a few disadvantages that limit the wide-spread of mercury or xenon lamps-based microscopy system in biological applications. First, sometimes these traditional light sources are too bright and harmful for the living organisms being studied. Excessive brightness can cause rapid photo-bleaching of the dyes used to stain the cells/ tissues. UV light especially, if not blocked, can have significant deleterious effects on live cells. Second, there are substantial costs involved in using mercury or xenon lamps because of their relatively short lifespan. The life of a mercury lamp is usually several hundred hours, and the intensity of these lamps decays progressively during this time. In addition, gas discharge lamps require some time to warm up before lamp intensity reaches steady state. Therefore, once mercury lamps are turned on, they have to be left on for hours to enable fluorescent measurements as needed without delay, thereby further shortening the lamp lifetime. Third, there are also some hazards issues of using mercury or xenon lamps. These lamps generate a significant amount of heat and therefore introduce complications when used in a confined space. When mercury lamps die, they can explode and damage the lenses or mirrors within the lamp housing. These factors combine to make gas discharge lamps inconvenient for lab-based applications and impractical for field applications, including use in portable, miniature, or low cost imaging devices. By contrast, light-emitting diodes (LEDs) show great pro

Development and production of the ionization chamber for the T2K muon monitor

We report on the development of an ionization chamber for the muon monitor in the T2K (Tokai-to-Kamioka) long baseline neutrino oscillation experiment.In the T2K experiment, we generate a muon neutrino beam using the 50-GeV proton synchrotron in J-PARC and detect it in the Super-Kamiokande detector, which is 295km away from J-PARC. We aim the neutrino beam off-axis by 2.5° from Super-Kamiokande in order to maximize the sensitivity to the neutrino oscillation measurement. Since the beam direction is required to be aimed within 1mrad, we need to monitor it with a precision better than 1mrad.The muon monitor is the only instrument that can monitor the neutrino beam direction in real time by measuring a profile of muons which are generated along with neutrinos. It is required to measure the intense muon beam precisely and stably in a high radiation area. Therefore, we use two independent systems for the muon monitor: an array of ionization chambers and another array of solid-state detectors. We developed the ionization chamber and performed beam tests with an electron beam at the Laboratory of Particle Beam Science in Kyoto University. We also had a long-term test in the NuMI beamline at Fermilab. Then we finalized the design of the ionization chamber and built it. We expect the ionization chambers as the muon monitor to monitor the beam direction with a precision of 0.2mrad.

Facing the challenge of biosample imaging by FTIR with a synchrotron radiation source

Fourier-transform infrared (FTIR) synchrotron radiation (SR) microspectroscopy is a powerful molecular probe of biological samples at cellular resolution (<10 microm). As the brilliance of SR is 100-1000 times higher than that of a conventional Globar source, FTIR microscopes are now available in almost all advanced SR facilities around the world. However, in spite of this superior performance, the expected advances in IR SR microscopy have not yet been realised, particularly with regard to bio-analytical studies of single cells and soft tissues. In recent decades solid-state array detectors have revolutionized the fields of molecular spectroscopy and chemical imaging, and now new IR focal plane array detectors implemented at ultra-bright SR facilities will extend the performance and overcome the existing limitations, possibly allowing IR SR instrumentation to achieve the highest sensitivity and resolution of molecular imaging. The impact of IR imaging on large tissue area and the complexity of the analysis are discussed. In view of the high brilliance of SR sources, a comparison of published microscope images is given. Finally, it is briefly outlined how an optimized combination of IR instrumentation and SR optical systems could reach the expected advantages of a SR-based FTIR imaging system.

Role of Bound Zn(II) in the CadC Cd(II)/Pb(II)/Zn(II)-responsive Repressor

The Staphylococcus aureus plasmid pI258 cadCA operon encodes a P-type ATPase, CadA, that confers resistance to Cd(II)/Pb(II)/Zn(II). Expression is regulated by CadC, a homodimeric repressor that dissociates from the cad operator/promoter upon binding of Cd(II), Pb(II), or Zn(II). CadC is a member of the ArsR/SmtB family of metalloregulatory proteins. The crystal structure of CadC shows two types of metal binding sites, termed Site 1 and Site 2, and the homodimer has two of each. Site 1 is the physiological inducer binding site. The two Site 2 metal binding sites are formed at the dimerization interface. Site 2 is not regulatory in CadC but is regulatory in the homologue SmtB. Here the role of each site was investigated by mutagenesis. Both sites bind either Cd(II) or Zn(II). However, Site 1 has higher affinity for Cd(II) over Zn(II), and Site 2 prefers Zn(II) over Cd(II). Site 2 is not required for either derepression or dimerization. The crystal structure of the wild type with bound Zn(II) and of a mutant lacking Site 2 was compared with the SmtB structure with and without bound Zn(II). We propose that an arginine residue allows for Zn(II) regulation in SmtB and, conversely, a glycine results in a lack of regulation by Zn(II) in CadC. We propose that a glycine residue was ancestral whether the repressor binds Zn(II) at a Site 2 like CadC or has no Site 2 like the paralogous ArsR and implies that acquisition of regulatory ability in SmtB was a more recent evolutionary event.

A Five-coordinate Metal Center in Co(II)-substituted VanX

In an effort to structurally probe the metal binding site in VanX, electronic absorption, EPR, and extended x-ray absorption fine structure (EXAFS) spectroscopic studies were conducted on Co(II)-substituted VanX. Electronic spectroscopy revealed the presence of Co(II) ligand field transitions that had molar absorptivities of approximately 100 m(-1) cm(-1), which suggests that Co(II) is five-coordinate in Co(II)-substituted VanX. Low temperature EPR spectra of Co(II)-substituted VanX were simulated using spin Hamiltonian parameters of M(S) = |+/-1/2), E/D = 0.14, g(real(x,y)) = 2.37, and g(real(z)) = 2.03. These parameters lead to the prediction that Co(II) in the enzyme is five-coordinate and that there may be at least one solvent-derived ligand. Single scattering fits of EXAFS data indicate that the metal ions in both native Zn(II)-containing and Co(II)-substituted VanX have the same coordination number and that the metal ions are coordinated by 5 nitrogen/oxygen ligands at approximately 2.0 angstroms. These data demonstrate that Co(II) (and Zn(II) from EXAFS studies) is five-coordinate in VanX in contrast to previous crystallographic studies (Bussiere, D. E., Pratt, S. D., Katz, L., Severin, J. M., Holzman, T., and Park, C. H. (1998) Mol. Cell 2, 75-84). These spectroscopic studies also demonstrate that the metal ion in Co(II)-substituted VanX when complexed with a phosphinate analog of substrate D-Ala-D-Ala is also five-coordinate.

IBIS: The Imager on-board INTEGRAL

The IBIS telescope is the high angular resolution gamma-ray imager on-board the INTEGRAL Observatory, successfully launched from Baikonur (Kazakhstan) the 17th of October 2002. This medium size ESA project, planned for a 2 year mission with possible extension to 5, is devoted to the observation of the gamma-ray sky in the energy range from 3 keV to 10 MeV (Winkler [CITE]). The IBIS imaging system is based on two independent solid state detector arrays optimised for low ( keV) and high ( MeV) energies surrounded by an active VETO System. This high efficiency shield is essential to minimise the background induced by high energy particles in the highly excentric out of van Allen belt orbit. A Tungsten Coded Aperture Mask, 16 mm thick and ~1 squared meter in dimension is the imaging device. The IBIS telescope will serve the scientific community at large providing a unique combination of unprecedented high energy wide field imaging capability coupled with broad band spectroscopy and high resolution timing over the energy range from X to gamma rays. To date the IBIS telescope is working nominally in orbit since more than 9 month.

Geometric calibration models of infrared cameras and scanners for photogrammetric and remote sensing applications

The paper is concerned with the geometric calibration of infrared imaging systems with a view to use them in both photogrammetry and remote sensing applications. From the geometric point of view, three quite different types of infrared imagers can be distinguished: 1. the pyroelectric vidicon camera; 2. the CCD camera with 2-D areal array of solid-state detectors; and 3. the thermal video frame scanner (TVFS). These operate in different parts of the infrared spectrum. The special optical and detector technologies used in these different devices are first reviewed. On this basis, a special target plate is constructed with its own internal radiation source that allows all of these devices to be calibrated geometrically. The actual experimental and calibration procedures are described, as is the method used for the automated measurement of all the targets using image matching techniques. The subsequent data processing and analysis are then outlined. The results obtained from the successful calibration of a representative sample of CCD cameras and thermal video frame scanners are presented and discussed in detail. They provide much new and accurate information on the geometric characteristics of these imagers that can be used in military, medical, industrial, and environmental applications.

Dual energy imaging in mammography: Cross-talk study in a Si array detector

One of the main limitation to the extensive use of breast-cancer screening as a prevention method is the relatively high X-ray dose released to the patient. A new approach is under study in which two quasi-monochromatic beams – with mean energies of 18.0 and 36.0 keV – are produced simultaneously, starting from an X-ray tube, by means of a monochromator based on a pyrolytic graphite crystal. The two beams are superimposed in space. The removal of the energy components with low content of diagnostic information from the spectrum, leads to a reduction of the dose released to patients maintaining (or improving) the image quality. The two quasi-monochromatic beams impinge on the patient and then are detected with a solid-state array detector; the image results as the difference between the transmitted intensities of the two detected beams. In this work, the performances of two different electronic readouts and three pixel widths of a silicon position sensitive array detector are simulated and described in order to minimize cross-talk effects between adjacent pixels. The use of a detector with spectrometric capabilities is necessary to separate, by means of thresholds, the high energy photons from the low energy ones.

X-ray computed tomography

X-ray computed tomography (CT) is a medical imaging technique that produces images of transaxial planes through the human body. When compared with a conventional radiograph, which is an image of many planes superimposed on each other, a CT image exhibits significantly improved contrast although this is at the expense of reduced spatial resolution.A CT image is reconstructed mathematically from a large number of one-dimensional projections of the chosen plane. These projections are acquired electronically using a linear array of solid-state detectors and an x-ray source that rotates around the patient.X-ray computed tomography is used routinely in radiological examinations. It has also been found to be useful in special applications such as radiotherapy treatment planning and three-dimensional imaging for surgical planning.

Infrared Detectors and Emitters: Materials and Devices

Notwithstanding the title of Infrared Detectors and Emitters: Materials and Devices, the major theme of this book is infrared detection, and in particular the varied materials and device technologies which compete to provide solid state detector arrays for high performance infrared imaging. One of the advantages of a book of this kind is the opportunity to compare, in a single volume, the relative merits and maturity of such a broad spectrum of infrared materials. The book deals comprehensively with the mainstream technologies of mercury cadmium telluride, indium antimonide, metal silicides, quantum wells and uncooled pyroelectrics and microbolometers. In addition, we have individual chapters on some aspiring alternatives such as lead chalcogenides, thallium-based compounds, the zinc and manganese alloys of HgTe, and low-dimensional structures using InAsSb and HgTe-CdTe. At times the enthusiasm and rivalry among the authors shows through in the claims made for their respective technologies. For example, in chapter 7 we learn that `the largest single array in use today' is a 1024�1024 element InSb array. Later, in chapter 12, we learn `the largest reported to date' is a 2048�2048 MCT array! Enthusiasm also accounts for the inclusion of topics on magnetic field sensors and transistors, which are outside the scope of the book's title. The black-and-white photographic reproductions in this book, though adequate, are small and somewhat grainy and do not do full justice to the original subjects. The book provides a useful, compact reference work for the infrared specialist and a good tutorial for the non-specialist, particularly through the two introductory chapters on the operating principles and assessment of devices, and theoretical sections dispersed amongst the other chapters. Chapters 1 and 2 are recommended reading before full immersion in the later chapters, which are all by well-known experts in their chosen fields. The chapters on uncooled microbolometer arrays by R A Wood and on photovoltaic detectors in MCT by M B Reine are especially lucid and comprehensive. Peter Knowles

Extended wavelength InGaAs infrared (1.0–2.4 μm) detector arrays on SCIAMACHY for space-based spectrometry of the Earth atmosphere

Space qualified InGaAs solid-state array detectors, covering the near-infrared 1–2.4 μm wavelength range, have been developed for application in space-based spectroscopy of the Earth atmosphere. The SCIAMACHY atmospheric chemistry instrument on the ESA ENVISAT satellite (2002–2005) will be equipped with a series of these novel detectors. Detectors are arranged in linear arrays of 1024 pixels of 25×500 μm 2 dimension and meet requirements on modestly low operating temperature (150 K) and low levels of dark current and noise. In this paper the underlying physics of dark current and noise of the detector system is studied on the basis of a theoretical model in combination with measurements. At 2.4 μm wavelength the dark-current performance achieved is 20–100 fA at an operating temperature of 150 K and a bias voltage of −2 mV. This corresponds to a figure of merit for detector resistance R 0 times detector pixel area A of R 0 A=2.5–12.5 MΩ cm 2. This result has required the development of a customised multiplexer for parallel detector read-out at near-zero bias voltage. Further reduction of the operating temperature will not result in lowering the dark current and noise of the InGaAs detectors which are shown to be limited by tunnelling current. A route to future improvement is discussed.

The relative abundance of actinides in the cosmic radiation

Abstract The DIAS-ESTEC Ultra Heavy Cosmic Ray Experiment (UHCRE) on the Long Duration Exposure Facility (LDEF) collected approximately 3000 cosmic-ray nuclei with Z>65 in the energy region E>1.5 GeV/nucleon during a six year exposure in Earth orbit. The entire accessible collecting area of the solid-state nuclear-track detector (SSNTD) array has been scanned for actinides, yielding a sample of thirty from an exposure of ≈150 m 2 sr yr. The observed charge spectrum is presented. The current best value for the cosmic-ray actinide relative abundance, (Z>88)/(74≤Z≤87), is given. This value is considered in the context of the predictions of source/propagation models.

Magnetic compton scattering using the elliptical multipole wiggler at sector 11-ID-B

Magnetic Compton scattering has been used to measure the momentum distribution of magnetic electrons in several materials. The polarization and frequency tunability of the elliptical multipole wiggler (EMW) makes it an ideal source for magnetic Compton scattering experiments. We performed the measurements using 50, 100 and 150 keV photons simultaneously. The EMW was operated at K y =14 (E c =32 keV) and K x between 0.6 and 1.03. The degree of circular polarization was about 80% or higher. The sample was mounted between the poles of an electromagnet in a field of 0.8 T. The majority of Compton scattering measurements were performed by switching the magnet polarity. Tests using an iron foil target gave a similar magnetic Compton profile by either switching the magnetic field or the photon helicity. A 9-element Ge solid state detector array was used for detection.

Towards microstrip detectors for synchrotron powder diffraction facilities

A major improvement of todays experimental techniques in powder diffraction can be achieved by using a massively parallel detection of diffraction patterns with arrays of solid-state detectors. In order to determine the feasibility of this technique, a test experiment was performed at the Swiss–Norwegian Beamline (SNBL) of the European Synchrotron Radiation Facility (ESRF). Diffraction patterns of previously characterized samples were first recorded with conventional equipment: in high-intensity mode with a single slit in front of the detector (Debye–Scherrer geometry) and at highest angular resolution with an analyzer crystal before the detector. Results were then compared to measurements performed with a double-sided silicon microstrip detector. Particular attention was placed on angular resolution and integrated intensities since these parameters are of most importance for structure determination from powder diffraction patterns. The results presented in this paper provide a basis for the design of a dedicated detector array for the synchrotron powder diffraction facility at the Swiss Light Source presently under construction at the Paul Scherrer Institute.

The future of atomic absorption spectrometry: a continuum source with a charge coupled array detector?

Continuum source atomic absorption spectrometry (CS-AAS) has made impressive progress in the last 5 years thanks to the availability of high resolution echelle spectrometers and solid state array detectors. With these new spectrometers and detectors, the capabilities of CS-AAS exceed those of conventional, line source-AAS (LS-AAS). For CS-AAS, absorbances are more accurate (corrected for stray radiation and non-specific broadband background absorption and integrated with respect to height in the furnace), detection limits average a factor of 2 lower, calibration ranges are a factor of 1000 greater, multi-wavelength data are available for correction of spectral interferences, sensitivity is a powerful quality assurance measure since it is independent of all instrument parameters except atomization temperature and, of course, multi-element detection is possible. The future appears bright for CS-AAS. Whereas, previously, CS-AAS was striving for parity with LS-AAS, it is now reasonable to state that it is CS-AAS which is setting the standard.