2D Position Sensitive Detector Research Articles

Design of Compact Polarized Neutron Imaging System for Accelerator Based Small Neutron Sources

Recently, compact neutron sources have been developed consisting of a small proton accelerator, a Be-target and a moderator, which can be installed in an experimental room. These sources have a possibility of various industrial applications because of their compactness. One of the applications is the polarized neutron imaging system. The system consists of neutron bender, polarizer, spin rotator, sample table, second spin rotator, spin analyzer and 2D-position sensitive detector. Since the neutron source is small and the imaging system should be installed near the moderator, the bender and polarizer have to be properly designed to have relatively wide acceptance angle for the incident beam. In the present study, the design and estimated results of such imaging system for will be presented.

Design Considerations and Testing of Virtual Frisch-Grid CdZnTe Detector Arrays Using the H3D ASIC

We discussed the design implementation and results from testing 2 × 2-, 3 × 3-, and 2 × 4-arrays of 6×6 ×15 mm3 CdZnTe virtual Frisch-grid detectors. In these measurements we employed a data acquisition system based on the H3D ASIC developed by BNL's Instrumentation Division in collaboration with the University of Michigan for 3D position-sensitive detectors. We used CZT crystals with a range of performance attributes to evaluate practical array configurations and detector-assembling procedures. The detector ratings were assigned based on the pulse-height spectra and correlated with data from X-ray diffraction topography measurements and X-ray response mapping obtained at BNL's National Synchrotron Light Source. The results helped us to better understand the performance limits of these detectors, and to identify future improvements in the array's design and requirements for the new readout ASIC.

GINA—A polarized neutron reflectometer at the Budapest Neutron Centre

The setup, capabilities, and operation parameters of the neutron reflectometer GINA, the recently installed "Grazing Incidence Neutron Apparatus" at the Budapest Neutron Centre, are introduced. GINA, a dance-floor-type, constant-energy, angle-dispersive reflectometer is equipped with a 2D position-sensitive detector to study specular and off-specular scattering. Wavelength options between 3.2 and 5.7 Å are available for unpolarized and polarized neutrons. Spin polarization and analysis are achieved by magnetized transmission supermirrors and radio-frequency adiabatic spin flippers. As a result of vertical focusing by a five-element pyrolytic graphite monochromator, the reflected intensity from a 20 × 20 mm(2) sample has been doubled. GINA is dedicated to studies of magnetic films and heterostructures, but unpolarized options for non-magnetic films, membranes, and other surfaces are also provided. Shortly after its startup, reflectivity values as low as 3 × 10(-5) have been measured by the instrument. The instrument capabilities are demonstrated by a non-polarized and a polarized reflectivity experiment on a Si wafer and on a magnetic film of [(62)Ni/(nat)Ni](5) isotope-periodic layer composition. The facility is now open for the international user community. Its further development is underway establishing new sample environment options and spin analysis of off-specularly scattered radiation as well as further decreasing the background.

Developments of a 2D position sensitive neutron detector

China Spallation Neutron Source (CSNS), one project of the 12th Five-Year-Plan scheme of China, is under construction in Guangdong province. Three neutron spectrometers will be installed during the first phase of the project, and two-dimensional position sensitive thermal neutron detectors are required. Before the construction of the neutron detectors, a prototype of a two-dimensional 200 mm×200 mm Multi-wire Proportional Chamber (MWPC) with Ar/CO2 (90/10) flowing gas has been constructed. In 2009, the prototype was tested with the 55Fe X-ray using part of the electronics, and performed well.Following the test in 2009, the neutron detector was constructed with the complete electronics and filled with the 6 atm. 3He+2.5 atm. C3H8 gas mixture in 2010. The neutron detector has been primarily tested with an Am-Be source. In this paper, new developments of the neutron detector including the design of the high pressure chamber, the optimization of the gas purifying system and the gas filling process will be reported. The results and discussion are also presented in this paper.

Instrumental profile of MYTHEN detector in Debye-Scherrer geometry

The main aberrations affecting data collected with 1D position sensitive detectors in Debye-Scherrer capillary geometry are examined, and analytical corrections proposed. The equations are implemented in two of the most advanced software based on the Rietveld and Whole Powder Pattern Modelling methods, respectively, for structure and microstructure analysis. Application to MYTHEN, a fast single photon counting detector developed at the Swiss Light Source, is discussed in detail.

Project of the new multifunctional reflectometer GRAINS with horizontal sample plane at the IBR-2M pulsed reactor in Dubna

The new multifunctional reflectometer GRAINS is under construction at the modernized high flux IBR-2 pulsed reactor (IBR-2M) of the FLNP JINR (Dubna, Russia). The principal feature of this reflectometer, the horizontal sample plane (or vertical scattering plane), enables the study of liquid-containing interfaces. The reflectometer will operate in the time-of-flight regime with constant sample illumination during measurements. The important advantage is the constant angular resolution with unvaried background. The additional modes of the GRAINS reflectometer comprise (1) off-specular scattering and GISANS, which are measured simultaneously in the TOF regime at a 2D position-sensitive detector; (2) angular encoding in the horizontal plane, which is provided by a Larmor precession region limited by current sheets in front of the sample; (3) 3D polarimetry in reflection, which is provided by a Larmor precession region around the sample position. The design of the reflectometer is optimised to take better advantage of an exceptionally broad wavelength band of the new cold moderator at the IBR-2M. The set-up will open up principally new possibilities for investigations in the field of interface nano-science at the IBR-2M reactor.

ASIC for High Rate 3D Position Sensitive Detectors

We report on the development of an application specific integrated circuit (ASIC) for 3D position sensitive detectors (3D PSD). The ASIC is designed to operate with pixelated wide bandgap sensors like Cadmium-Zinc-Telluride (CZT), Mercuric Iodide (Hgl2) and Thallium Bromide (TIBr). It measures the amplitudes and timings associated with an ionizing event on 128 anodes, the anode grid, and the cathode. Each channel provides low-noise charge amplification, high-order shaping with peaking time adjustable from 250 ns to 12 μs, gain adjustable to 20 mV/fC or 120 mV/fC (for a dynamic range of 3.2 MeV and 530 keV in CZT), amplitude discrimination with 5-bit trimming, and positive and negative peak and timing detections. The readout can be full or sparse, based on a flag and single- or multi-cycle token passing. All channels, triggered channels only, or triggered with neighbors can be read out thus increasing the rate capability of the system to more than 10 kcps. The ASIC dissipates 330 mW which corresponds to about 2.5 mW per channel.

New Two-Dimensional Solid State Pixel Detectors With Dedicated Front-End Integrated Circuits for X-Ray and Gamma-Ray Imaging

New two-dimensional (2D) position sensitive solid state pixel detectors with dedicated multi-channel mixed-signal front-end readout integrated circuits (ICs) have been developed for x-ray and gamma ray imaging. These pixel detectors were designed to be versatile and accommodate many types of position-sensitive solid-state sensors. These 2D pixel detectors are designed to address the needs of a wide range of photon counting applications with high energy resolution imaging, high spatial resolution and for fast photon counting with simultaneous multiple energy binning capability. The first family of these pixel detectors is intended for spectroscopy applications with sensors such as Si, Ge, GaAs, HgI <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , PbI <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , Se, CdTe and CdZnTe in a variety of configurations to detect and image x-rays and gamma-rays of energies up to 1.3 MeV. The second family is developed for fast photon counting with simultaneous energy binning. They can be used with similar solid state sensors. The third family is for high spatial resolution imaging with resolution down to 50 times 50 micron.

Readout ASIC for 3D Position-Sensitive Detectors

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> We describe an application specific integrated circuit (ASIC) for 3D position-sensitive detectors. It was optimized for pixelated Cadmium–Zinc–Telluride (CZT) sensors, and it measures, corresponding to an ionizing event, the energy and timing of signals from 121 anodes and one cathode. Each channel provides low-noise charge amplification, high-order shaping, along with peak- and timing-detection. The cathode's timing can be measured in three different ways: the first is based on multiple thresholds on the charge amplifier's voltage output; the second uses the threshold crossing of a fast-shaped signal; and the third measures the peak amplitude and timing from a bipolar shaper. With its power of 2 mW per channel the ASIC measures, on a CZT sensor connected and biased, charges up to 100 fC with an electronic resolution better than 200 <formula formulatype="inline"><tex>${\rm e}^{-}$</tex></formula> rms. Our preliminary spectral measurements applying a simple cathode/anode ratio correction demonstrated a single-pixel resolution of 4.8 keV (0.72 %) at 662 keV, with the electronics and leakage current contributing in total with 2.1 keV. </para>

Development, simulation and processing of new 3D Si detectors

New 3D Si detector structures have been proposed by BNL at the end of 2005. Different from the traditional planar Si detector technology, 3D detector technology places p + and n + electrodes vertically through the entire detector thickness, thus involves 3D processing. Our new 3D structures have some new features either in configuration and/or in processing: (1) all electrodes are processed on one side of the wafer to ensure a simple, true one-sided processing; and (2) stripixel electrode configuration can be arranged to get 2D position sensitive strip-like detectors with single-sided processing. The processing of the first prototype detectors batch of the new 3D detectors with single-column (n + column on p-type substrate) has begun. All n + columns have been etched and the remaining planar processing are been finishing up. Dual electrode columns (p + and n +) one-sided 3D Si detectors are planned for future prototype batches. Electric field simulations and estimation of CCE at SLHC fluences have been carried out for the new 3D Si detectors.

Ions transmitted through an anodic nanocapillary array

The transmission of incident $10--20\phantom{\rule{0.3em}{0ex}}\mathrm{keV}∕q$ ${\mathrm{Ar}}^{+}$, ${\mathrm{Ar}}^{3+}$, ${\mathrm{Ne}}^{3+}$, and ${\mathrm{Ne}}^{7+}$ ions in an ${\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ nanocapillary array was studied. The array consists of a dense distribution of pores typically $100\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ in diameter and $60\phantom{\rule{0.3em}{0ex}}\mathrm{\ensuremath{\mu}}\mathrm{m}$ in length. Emergent charge-state-selected angular distributions were studied at low energy using a two-dimensional (2D) position sensitive detector. The principal transmitted $q$ state is the incident $q$ state in all cases. The transmitted fraction of incident beam, $\ensuremath{\approx}2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}$, is many orders of magnitude smaller than the array's surface porosity $(\ensuremath{\approx}40%)$. No evidence of significant energy loss is observed for the transmitted ions. Yields in lower $q$ states and neutrals formed by electron capture are typically below 3% of the entrance $q$-state yield. Observed angular distributions consist of well resolved, 2D structures sitting on a continuum distribution. The angular distribution and sharp angular structures can be steered in the direction of the pores within about $\ifmmode\pm\else\textpm\fi{}0.5\ifmmode^\circ\else\textdegree\fi{}$ without a significant loss of transmitted intensity by rotating the sample with respect to the incident beam. All data suggest that the structure in the scattered ion angular distributions arises when ions bounce at ultralow grazing angles in very large impact parameter Coulomb collisions with electrically charged nanopore walls. Analysis of the observed structure has allowed the identification of single, double, and triple collisions inside the nanopores.

Neutron diffraction studies of magnetic-shape memory Ni–Mn–Ga single crystal

Neutron diffraction of single crystal of the typical example of magnetic-shape memory (MSM) alloy Ni 49.7Mn 29.3Ga 21 was carried out with a 2D position sensitive detector. The quality and inhomogeneity of the single crystal and martensite variant distribution was studied using ω-scan of selected nuclear Bragg reflections. The neutron diffraction reveals split of the (2 0 0) reflection of major martensite variant and large structural inhomogeneities in martensite phase. Using measurement in reciprocal space, we recorded a set of reflections that appear due to structural modulation (5 M) of the martensite, however, the set seems to be incomplete with missing or very weak reflections of second order compared with X-ray diffraction. The line of the magnetic reflection arising from the supposed antiferromagnetic ordering of the excess Mn atoms was very weak and it is difficult to discern from the background.

A 2D position sensitive germanium detector for spectroscopy and polarimetry of high-energetic x-rays

We report on a first prototype 2D μ-strip germanium detector, developed at IKP-Jülich, and its performance test at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France. Beside an accurate determination of the detector response function, the polarization sensitivity has been addressed in this study. For this purpose photon beams at energies of 60 keV and 210 keV have been used.

Characterization of one-dimensional position sensitive detectors with improved efficiency and position resolution for neutron spectrometers

Development and characterization of one-dimentional (1D) position sensitive detectors (PSDs) with improved efficiency and position resolution for neutron scattering applications are reported. The PSDs are characterized for energy resolution, count rate capability, sensitivity, efficiency, position resolution, and uniformity of response over the sensitive length. The studies are carried out to verify the dependence of position resolution on detector geometry, electronic noise, and stopping power of the fill gas. One of the PSDs is mounted on the small angle neutron scattering spectrometer and spectra from CTAB micelle sample are recorded using 5.4 A neutrons. A gain of factors 1.1 and 1.2 is obtained compared to earlier in house made 1D PSD and LND-made 1D PSD, respectively. The diffraction patterns from standard vanadium, nickel, and silicon samples are recorded on a powder diffractometer using newly designed PSDs. Gain in efficiency obtained at shorter wavelength of 0.783 A is by a factor of 1.6. All high pressure PSDs show improvement in the position resolution by 2-3 mm. It is observed that 1D PSD filled with isobutane as stopping gas improves the gamma tolerance and position resolution at lower partial pressures as compared to Kr. It is advantageous to use two or more 36C-type PSDs stacked together. It is economic and gives better efficiency due to scanning more beam height.

3 dimensional polymorphous silicon based metal-insulator-semiconductor position sensitive detectors

In this work we investigate the properties of a polymorphous silicon (pm-Si:H) metal-insulator-semiconductor (MIS) structure used in 3D position sensitive detectors (PSD). For the first time a 3D sensor made-up by pm-Si:H/SiO 2/Au layers is presented. MIS structures present several advantages over p-i-n structures, such as easier fabrication, fast response time and higher resolution. The 1D MIS PSD that constitute the array were extensively studied aiming its application in 3D pattern recognition. The results obtained show that MIS PSD can achieve non-linearities below 2% and sensitivities of 3.2 μA/cm over 6 mm length sensors. The miniaturization of the sensors length to arrays of 6 and 16 mm, respectively showed average non-linearities of about 1.9% for the 16 mm sensor which proved to be the best solution for this MIS structure.

Fission hindrance studies inPb200: Evaporation residue cross section and spin distribution measurements

Evaporation residue cross sections and spin distributions have been measured for $^{200}\mathrm{Pb}$ compound nucleus formed in $^{16}\mathrm{O}+^{184}\mathrm{W}$ reaction at the laboratory beam energies of 84, 92, 100, 108, 116, and 120 MeV. The evaporation residues have been selected using the recoil mass spectrometer, HIRA and detected using a 2D position sensitive silicon detector. The evaporation residue spin distributions have been measured by detecting gamma rays with 14 element BGO multiplicity filter. Measured evaporation residue cross sections and spin distributions are compared with the values predicted by a standard statistical model code. Comparison shows that, in the energy region studied, the nuclear viscosity parameter $\ensuremath{\gamma}=3$ is required to explain total evaporation residue cross sections and evaporation residue spin distributions.

A toroidal sector for the electron branch of a reaction microscope

We present calculations for the electron branch of a reaction microscope with a toroidal magnetic field for experiments in a storage ring. A suitable toroidal magnetic field guides the electrons away from the vicinity of the coasting beam onto a 2D position-sensitive detector. Other than in the linear geometry, 2D position and time-of-flight information for electrons on the detector are coupled in this geometry. For beam velocities below 12 au corresponding to projectile specific energies ⩽3.6 AMeV fast electrons emitted by the projectile and slow electrons can still conveniently be mapped simultaneously onto a single electron detector. For a position and time resolution of 0.2 mm and 1 ns, respectively, 1 eV can be resolved for electrons of 200 eV, which corresponds to a momentum resolution of about 0.3 au. A prototype for the toroidal sector will be tested using Unilac beams.

Wombat: The high-intensity powder diffractometer at the OPAL reactor

The Wombat powder diffractometer will be located on the TG1 thermal guide at the OPAL reactor. A variable vertically focusing monochromator will provide a flux of up to ≈10 8 ns −1 cm −2 at the sample position. A compact curved 2D position sensitive detector will allow simultaneous acquisition of 120 ° in 2 θ, with ≈10 6 s −1 count rate capability and time resolution down to the microsecond level. Wombat is designed for experiments requiring rapid real time acquisition (time-resolved environmental or kinetics experiments) or very good signal to noise (experiments with difficult sample environments or small sample volumes).

Benchmark testing of a multiblade neutron velocity selector

The fully operational prototype of a rotational velocity selector for neutron beam monochromation has been tested and the results compared to the theoretical characteristics (output wavelength, transmission and selectivity with respect to velocity and horizontal tilt angle of the multiblade rotor system). The minimum of the selected central wavelength is 2.5 Å in the current construction. Measurements are performed on a cold neutron beam at the Budapest Neutron Centre by energy-resolved pinhole beam imaging, using a 2D position-sensitive detector in time-of-flight regime. Thus, the effects of the incoming beam divergence are also evaluated.

Neutron beam phase space mapping

The phase space of neutron beams is mapped by means of energy-resolved neutron imaging using a 2D position-sensitive detector in time-of-flight regime. The beam is viewed through a pinhole with adjustable position with respect to the beam axis, mapping the beam cross-section. The neutron beam flux and divergence are measured with respect to position and wavelength. The results can be used in subsequent downstream instrument design and optimization, as input and/or test data for simulation codes as well as for characterization of upstream elements (neutron sources, monochromators, guides etc). Results of measurements performed at the exit of a tapered supermirror guide on a beam at the Budapest Neutron Centre are presented.