[Show abstract][Hide abstract] ABSTRACT: A cold neutron imaging and diffraction instrument, IMAT, is currently being constructed at the ISIS second target station. IMAT will capitalize on time-of-flight transmission and diffraction techniques available at a pulsed neutron source. Analytical techniques will include neutron radiography, neutron tomography, energy-selective neutron imaging, and spatially resolved diffraction scans for residual strain and texture determination. Commissioning of the instrument will start in 2015, with time-resolving imaging detectors and two diffraction detector prototype modules. IMAT will be operated as a user facility for material science applications and will be open for developments of time-of-flight imaging methods.
[Show abstract][Hide abstract] ABSTRACT: The performance of the new position sensitive neutron detector arrays of the Small Angle Neutron Scattering (SANS) instrument SANS2d is described. The SANS2d instrument is one of the seven instruments currently available for users on the second target station (TS2) of the ISIS spallation neutron source. Since the instrument became operational in 2009 it has used two one metre square multi-wire proportional detectors (MWPC). However, these detectors suffer from a low count rate capability, are easily damaged by excess beam and are then expensive to repair. The new detector arrays each consist of 120 individual position sensitive detector tubes, filled with 15 bar of 3He. Each of the tubes is one metre long and has a diameter of 8mm giving a detector array with an overall area of one square metre. Two such arrays have been built and installed in the SANS2d vacuum tank where they are currently taking user data. For SANS measurements operation of the detector within a vacuum is essential in order to reduce air scattering. A novel, fully engineered approach has been utilised to ensure that the high voltage connections and preamps are located inside the SANS2d vacuum tank at atmospheric pressure, within air tubes and air boxes respectively. The signal processing electronics and data acquisition system are located remotely in a counting house outside of the blockhouse. This allows easy access for maintenance purposes, without the need to remove the detectors from the vacuum tank. The design will be described in detail. A position resolution of 8mm FWHM or less has been measured along the length of the tubes. The initial measurements taken from a standard sample indicate that whilst the detector arrays themselves only represent a moderate improvement in overall detection efficiency (~ 20%), compared to the previous detector, the count rate capability is increased by a factor of 100. A significant advantage of the new array is the ability to change a single tube in situ within approximately one day with a relatively small staff effort. The results obtained from the first user trials are reported.
No preview · Article · Dec 2014 · Journal of Instrumentation
[Show abstract][Hide abstract] ABSTRACT: We demonstrate for the first time the viability of a three-dimensional (3D) elemental imaging technique based on Neutron Resonance Transmission Imaging (NRTI). NRTI is a neutron technique based on the presence of a resonance structure in the neutron-induced reaction cross sections. These resonances allow the identification of elements and isotopes within an object in a non-destructive manner. A dedicated set-up on the INES (Italian Neutron Experimental Station) beamline of the ISIS spallation neutron source was used for the experiments. An early mediaeval disc fibula from the Hungarian National Museum in Budapest was used for our demonstration. The methodology, analysis procedures are described and results obtained from the reconstruction of the 3D NRTI elemental image of the ancient object are compared with results obtained from other neutron based 3D imaging techniques.
No preview · Article · Dec 2014 · Journal of Analytical Atomic Spectrometry
[Show abstract][Hide abstract] ABSTRACT: The performance of the position sensitive neutron detector array of the WISH diffractometer is discussed. WISH (Wide angle In a Single Histogram) is one of the seven instruments currently available for users on the second target station (TS2) of the ISIS spallation neutron source, and is used mainly for magnetic studies of materials. WISH is instrumented with an array of 10 detector panels, covering an angular range of 320o, orientated in two semi-cylindrical annuli around a central sample position at a radius of 2.2m. In total the 10 detector panels are composed of 1520 3He based position sensitive detector tubes. Each tube has an active length of one metre, a diameter of 8mm and is filled with 3He at 15 bar. The specification for the WISH detectors included a neutron detection efficiency of 50% at a neutron wavelength of 1Å with good gamma rejection. A position resolution better than 8 mm FWHM along the length of the tubes was also required which has been met experimentally. Results obtained from the detector arrays showing pulse height and positional information both prior to and post installation are shown. The first 5 of the 10 detector panels have been operational since 2009, and comparable diffraction data from powder and single crystal samples taken from the remaining 5 panels (installation completed in 2013) shows that we have a detector array with a highly stable performance which is easily assembled and maintained. Finally some real user data is shown, highlighting the excellent quality of data attainable with this instrument.
No preview · Article · Dec 2014 · Journal of Instrumentation
[Show abstract][Hide abstract] ABSTRACT: The gamma-ray background spectra of VESUVIO and INES beamlines, at the ISIS spallation neutron source, were measured with an HPGe spectrometer. These measurements are intended to provide information on typical gamma-ray background spectra in spallation neutron source environments, with special regard to beamlines employing gamma-ray sensitive detectors. Sources and creation processes of more than 60 gamma-ray lines in the energy range 80 keV–12 MeV were identified by using specifically developed data analysis software.
No preview · Article · Aug 2014 · Journal of Analytical Atomic Spectrometry
[Show abstract][Hide abstract] ABSTRACT: A low-afterglow, 10B-doped neutron-sensitive ZnS/10B2O3 scintillator was developed. The developed ZnS phosphor has a primary decay time constant of about 60 ns with a low afterglow. The developed scintillator exhibited a mean afterglow height of 4% relative to the peak at 1 μs after the peak, which is half that of a commercial ZnS/6LiF scintillator manufactured by Applied Scintillation Technologies. The count-rate capability of a wavelength-shifting-fibre-based detector was increased to 30,000 cps by implementing the developed scintillator from 5,000 cps with the commercial scintillator.
No preview · Article · Jul 2014 · Journal of Physics Conference Series
[Show abstract][Hide abstract] ABSTRACT: The research of reliable substitutes of 3He detectors is an important task for the affordability of new neutron scattering instrumentation for future spallation sources like the European Spallation Source. GEM (Gas Electron Multiplier)-based detectors represent a valid alternative since they can combine high-rate capability, coverage of up to area and good intrinsic spatial resolution (for this detector class it can be better than 0.5 mm). The first neutron diffraction measurements performed using a borated GEM detector are reported. The detector has an active area of and is equipped with a borated cathode. The GEM detector was read out using the standard ISIS Data Acquisition System. The comparison with measurements performed with standard 3He detectors shows that the broadening of the peaks measured on the diffractogram obtained with the GEM is 20–30% wider than the one obtained by 3He tubes but the active area of the GEM is twice that of 3He tubes. The GEM resolution is improved if half of its active area is considered. The signal-to-background ratio of the GEM is about 1.5 to 2 times lower than that of 3He. This measurement proves that GEM detectors can be used for neutron diffraction measurements and paves the way for their use at future neutron spallation sources.
[Show abstract][Hide abstract] ABSTRACT: Measurements of the fast neutron energy spectrum at the ISIS spallation
source are reported. The measurements were performed with a Proton
Recoil Telescope consisting of a thin plastic foil placed in the neutron
beam and two scintillator detectors. Results in the neutron energy range
30 MeV < En < 80 MeV are in good agreement with Monte
Carlo simulations of the neutron spectrum.
No preview · Article · Nov 2013 · Journal of Instrumentation
[Show abstract][Hide abstract] ABSTRACT: A metallic 19th century flute was studied by means of integrated and simultaneous neutron-based techniques: neutron diffraction, neutron radiative capture analysis and neutron radiography. This experiment follows benchmark measurements devoted to assessing the effectiveness of a multitask beamline concept for neutron-based investigation on materials. The aim of this study is to show the potential application of the approach using multiple and integrated neutron-based techniques for musical instruments. Such samples, in the broad scenario of cultural heritage, represent an exciting research field. They may represent an interesting link between different disciplines such as nuclear physics, metallurgy and acoustics.
No preview · Article · Sep 2013 · Measurement Science and Technology
[Show abstract][Hide abstract] ABSTRACT: Single crystal diamond (SDD) detectors coupled to fast digital data acquisition were tested as monitors of fast neutrons at the ISIS pulsed spallation neutron source. The ISIS pulsed neutron beams are generated by proton induced spallation on a tungsten tantalum target at 50 Hz repetition rate. The SDD signal was digitized at 1 GHz to reconstruct the deposited energy and time of flight (tToF) of each detection event. The SDD system was used reliably and almost continuously over a period of several days. The results of the biparametric measurements are in qualitative agreement with predictions based on the proton beam pulse structure and the energy deposited in the SDD by the main neutron interaction processes.
No preview · Article · Aug 2013 · Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment
[Show abstract][Hide abstract] ABSTRACT: The performance characteristics of the Off Specular MicrOstrip Neutron Detector (OSMOND) are described. Based on microstrip gas chamber (MSGC) detectors, OSMOND is a high counting rate detector, with sub-millimeter position resolution, capable of replacing the existing rate limited scintillator detectors currently in use on the suite of reflectometer instruments of the ISIS spallation neutron source. The detector system is described together with results of neutron beam tests carried out on the CRISP and POLREF reflectometers.
No preview · Article · Jun 2013 · IEEE Transactions on Nuclear Science
[Show abstract][Hide abstract] ABSTRACT: The software package ANTS (Anger-camera type Neutron detector: Toolkit for Simulations), developed for simulation of Anger-type gaseous detectors for thermal neutron imaging was extended to include a module for experimental data processing. Data recorded with a sensor array containing up to 100 photomultiplier tubes (PMT) or silicon photomultipliers (SiPM) in a custom configuration can be loaded and the positions and energies of the events can be reconstructed using the Center-of-Gravity, Maximum Likelihood or Least Squares algorithm. A particular strength of the new module is the ability to reconstruct the light response functions and relative gains of the photomultipliers from flood field illumination data using adaptive algorithms. The performance of the module is demonstrated with simulated data generated in ANTS and experimental data recorded with a 19 PMT neutron detector. The package executables are publicly available at http://coimbra.lip.pt/~andrei/ [http://coimbra.lip.pt/~andrei]
No preview · Article · May 2013 · Journal of Instrumentation
[Show abstract][Hide abstract] ABSTRACT: The development and testing of the SuPerior Rate for INTER (SPRINTER) detector is described. Based on a microstrip gas chamber (MSGC), the aim of the project was to produce a matched pair of high-counting-rate detectors capable of replacing the existing 3He tubes currently used on the INTER reflectometer of the ISIS spallation neutron source. The detector system is described, and the results from the first neutron beam tests carried out on an ISIS neutron reflectometer are also shown.
No preview · Article · Apr 2013 · IEEE Transactions on Nuclear Science
[Show abstract][Hide abstract] ABSTRACT: The development and testing of the Off Specular MicrOstrip Neutron Detector (OSMOND) is described. Based on a microstrip gas chamber the aim of the project was to produce a high counting rate detector capable of replacing the existing rate limited scintillator detectors currently in use on the CRISP reflectometer for off specular reflectometry experiments. The detector system is described together with results of neutron beam tests carried out at the ISIS spallation neutron source. (c) 2012 Elsevier B.V. All rights reserved.
No preview · Article · Jan 2013 · Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment
[Show abstract][Hide abstract] ABSTRACT: The existence of resonance peaks in neutron absorption spectra in the epithermal range of energies enables unique non-destructive testing techniques. The deep penetration of epithermal neutrons provides an opportunity to perform a compositional analysis of a sample which is opaque to X-rays and thermal neutrons. The neutron resonances in the transmission spectra constitute a characteristic pattern for many isotopes, which can be used to identify the isotope and to map the distribution of the isotope in a sample. The neutron transmission spectra can be measured with the time of flight (TOF) technique using a pulsed neutron source. Combining this method with a high resolution neutron counting detector enables substantial improvements of spatial resolution of neutron resonance transmission imaging. Such a detector has been developed to register neutrons with 55 μm spatial and 10-1000 ns temporal resolution Our proof-of-principle experiments at the ISIS pulsed neutron spallation source demonstrate that compositional analysis of multi-element samples can now be performed with ~150 μm spatial resolution. Images of a test mask consisting of <; 200 μm thick foils of Au, Ag, In and Gd were collected in the 1-100 eV energy range. The experimental results demonstrate the potential for compositional analysis via resonance absorption transmission with high spatial resolution. In-bulk temperature measurement through Doppler broadening analysis will also benefit from this technique.
No preview · Article · Dec 2012 · IEEE Transactions on Nuclear Science
[Show abstract][Hide abstract] ABSTRACT: The development and testing of the SuPerior Rate for INTER (SPRINTER) detector is described. Based on a Microstrip Gas Chamber (MSGC) the aim of the project was to produce a matched pair of high counting rate detectors capable of replacing the existing 3He tubes currently used on the INTER reflectometer of the ISIS spallation neutron source. The detector system is described and the results from the first neutron beam tests carried out on an ISIS neutron reflectometer are also shown.
[Show abstract][Hide abstract] ABSTRACT: The high-energy neutron field of the VESUVIO instrument at the ISIS facility has been characterized using the technique of thin-film breakdown counters (TFBC). The technique utilizes neutron-induced fission reactions of natU and 209Bi with detection of fission fragments by TFBCs. Experimentally determined count rates of the fragments are ≈50% higher than those calculated using spectral neutron flux simulated with the MCNPX code. This work is a part of the project to develop ChipIr, a new dedicated facility for the accelerated testing of electronic components and systems for neutron-induced single event effects in the new Target Station 2 at ISIS. The TFBC technique has shown to be applicable for on-line monitoring of the neutron flux in the neutron energy range 1–800 MeV at the position of the device under test (DUT).
No preview · Article · Sep 2012 · Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment
[Show abstract][Hide abstract] ABSTRACT: A fast neutron beam monitor based on a triple Gas Electron Multiplier (GEM) detector was developed and tested for the ISIS spallation neutron source in U.K. The test on beam was performed at the VESUVIO beam line operating at ISIS. The 2D fast neutron beam footprint was recorded in real time with a spatial resolution of a few millimeters thanks to the patterned detector readout.
Full-text · Article · Jul 2012 · Journal of Instrumentation
[Show abstract][Hide abstract] ABSTRACT: A fast neutron
detection system suitable for high rate measurements is presented. The detector is based on a commercial high purity single crystal
diamond (SDD) coupled to a fast digital data acquisition system. The detector was tested at the ISIS pulsed spallation neutron source. The SDD event signal was digitized at 1 GHz to reconstruct the deposited energy (pulse amplitude) and neutron arrival time; the event time of flight (ToF) was obtained relative to the recorded proton beam signal t
0. Fast acquisition is needed since the peak count rate is very high (∼800 kHz) due to the pulsed structure of the neutron beam. Measurements at ISIS indicate that three characteristics regions exist in the biparametric spectrum: i) background gamma events of low pulse amplitudes; ii) low pulse amplitude neutron events in the energy range E
dep = 1.5-7 MeV ascribed to neutron
elastic scattering on 12C; iii) large pulse amplitude neutron events with En
< 7 MeV ascribed to 12C(n,α)9Be and 12C(n,n')3α.
[Show abstract][Hide abstract] ABSTRACT: The prototype of a wavelength-sensitive neutron filter has been realized and tested successfully for the first time. The filter exploits the neutron wavelength dependence of the transparency of He-3 gas. The analysis of test results gives high wavelength resolution Delta lambda/lambda similar or equal to 0.5% over the broad wavelength range 0.2-5.2 angstrom. We propose an idea to expand the filter range in the short wavelength direction by use of a cryogenic environment, and also consider the use of media using other than He-3 gas. The proposed filter might be used in advanced reflectometers and SANS2D neutron scattering instruments.
No preview · Article · Jun 2012 · Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment