Delay Line Readout Research Articles

Digitized signal acquisition of gas-filled, multiwire, neutron detector with delay-line readout

Multiwire counters are likely to remain a reliable and cost-efficient option for a large class of instruments. Delay-line position encoding is widely used in multiwire position sensitive particle detectors. Improvement of several detector parameters is a continuous demand such as count rate or position resolution. Digitization of the analog detector signals retains all information about the detected events at the highest count rate. Neutronic measurement results on our standard detector with 200mm × 200mm active area are presented with different acquisition algorithms. The analog signals were digitized by a high speed, multichannel Acqiris digitizer with 1 ns sampling resolution.

Small area detectors at the European XFEL

The detectors to be used at the European XFEL have to deal with the unique time structure of the machine, delivering up to 2700 pulses, with a repetition rate of 4.5 MHz, ten times per second, the very high photon flux and the need to combine single-photon sensitivity and a large dynamic range. This represents a challenge not only for the large-area 2D imaging detectors but also for the smaller-area detectors and makes the use of standard commercial devices impossible. Dedicated solutions are therefore envisaged for small imaging- or strip-detectors. In this contribution the focus is put on two particular small-area detector solutions which are planned to be used at the European XFEL, a strip detector for hard X-rays (with energy 3 < E < 25 keV) and an imaging detector for soft X-rays (0.25 < E < 3 keV). Hard X-rays photon-beam diagnostics as well as hard X-ray absorption and emission spectroscopy at the European XFEL make use of strip detectors as detectors for beam spectrometers or as energy-dispersive detectors in combination with an energy-dispersive element. The European XFEL is establishing cooperation with the Paul Scherrer Institute in Villigen to develop a new version of the Gotthard detector best suited to the European XFEL needs. The use case and the required detector specifications are illustrated. Starting from the present detector version, the modifications planned to adapt it to the European XFEL running conditions are described. These include the capability of running at an increased rate and to provide a veto signal to the large 2D imaging detectors, in order to be able to remove non-interesting images already at early stages of the DAQ system. In another particular application, resonant inelastic X-ray scattering, a Micro-Channel Plate detector matched to a delay-line readout is foreseen to be used. In this case the European XFEL is aiming for a highly customized solution provided by the German company Surface Concept. The use case is described, the science-driven detector specifications are illustrated and the expected detector performance is shown.

Large area event counting detectors with high spatial and temporal resolution

Novel large area microchannel plates (MCPs) constructed using micro-capillary arrays functionalized by atomic layer deposition (ALD) have been successfully demonstrated in large format detectors (10 cm and 20 cm) with cross delay line and cross strip readouts. Borosilicate micro-capillary substrates allow robust MCPs to be made in sizes to 20 cm, the intrinsic background rates are low ( < 0.06 events cm−2 sec−1), the channel open area can be made as high as 85%, and the gain after preconditioning (vacuum bake and burn-in) shows virtually no change over > 7 C cm−2 extracted charge. We have constructed a number of detectors with these novel MCPs, including a 10 × 10 cm cross strip readout device and 20 × 20 cm delay line readout sensors. The cross strip detector has very high spatial resolution (the 20 μm MCP pores can be resolved, thus obtaining ∼ 5k × 5k resolution elements), good time resolution ( < 1 ns), and high event rate ( > 5 million counts/s at 20% dead time), while operating at relatively low gain ( ∼ 106). The 20 × 20 cm delay line detectors have achieved spatial resolutions of ∼ 50 μm and event rates of several MHz, with good gain and background uniformity and < 200 ps event time tagging. Progress has also been made in construction of a 20 × 20 cm sealed tube optical imager, and we have achieved > 20% quantum efficiency and good uniformity for large area (20 cm) bialkali photocathodes.

Development of Parallel Plate Avalanche Counter (PPAC) for BigRIPS fragment separator

We have developed a position-sensitive Parallel Plate Avalanche Counter (PPAC), which has been used as a focal plane detector in the BigRIPS fragment separator and the subsequent RI-beam delivery lines at the RIKEN Nishina Center RI Beam Factory. The PPAC detector plays an important role not only in the tuning of the separator and delivery lines but also in the particle identification of rare isotope (RI) beams. The PPAC detector has a sensitive area of 240mm×150mm, and the position information is obtained by a delay-line readout method. Being called double PPAC, it is composed of two full PPACs, each measuring the particle locus in two dimensions. High detection efficiency has been made possible by the twofold measurement using the double PPAC detector. The sensitivity uniformity is also found to be excellent. The root-mean-square position resolution is measured to be 0.25mm using an α source, while the position linearity is as good as ±0.1mm for the detector size of 240mm. Characteristics, operating principles, specifications, performance and issues of the PPAC detector are presented, including its signal transmission system using optical fiber cables.

Development of a new time and position resolving detector for the pulsed low energy positron system PLEPS

The pulsed low energy positron system PLEPS at the Munich research reactor FRM-II is a user facility for depth resolved positron lifetime measurements. Besides positron lifetime measurements 2D-AMOC (Two Dimensional Age Momentum Correlation) experiments are also possible. 2D-AMOC provides in coincidence the lifetime of the positron and the longitudinal momentum distribution of the annihilated electron. It would be of great scientific concern to measure simultaneously the entire 3D-momentum distribution of the electron annihilating with the positron and the corresponding lifetime of the positron (4D-AMOC). To perform 4D-AMOC measurements a time and position resolving detector is required in coincidence with a pixelated Germanium detector. Therefore a time and spatially resolving detector is currently developed at our institute with envisaged time resolution of 100 ps (FWHM) and a spatial resolution of about 2.6 mm (FWHM) over an area of 12 cm2. First test measurements have been carried out with a 25 mm diameter MCP (Micro Channel Plate) image intensifier and with special delay-line anode readout for the spatial information. Up to now 178 ps (FWHM) time resolution and on average 3.4 mm (FWHM) position resolution have been achieved with BaF2 as scintillator material and a 60Co source.

Development and applications of a new neutron single-crystal diffractometer based on a two-dimensional large-area curved position-sensitive detector

A new single-crystal neutron diffractometer based on a large-area curved two-dimensional position-sensitive detector (C-2DPSD) has been developed. The diffractometer commissioning is almost complete, together with development of the measurement methodology and the raw data processing software package, the Reciprocal Analyzer, and the instrument is now ready to be launched for users. Position decoding of the C-2DPSD is via a delay-line readout method with an effective angular range of 110 × 54° in the horizontal and vertical directions, respectively, with a nominal radius of curvature of 530 mm. The diffractometer is equipped with a Ge(311) mosaic monochromator and two supermirror vacuum guide paths, one before and one after the monochromator position. The commissioning incorporates corrections and calibration of the instrument using an NaCl crystal, various applications such as crystallographic and magnetic structure measurements, a crystallinity check on large crystals, and a study on the composition or dopant content of a mixed crystal of (Tm x Yb1-x )Mn2O5. The installation of the diffractometer and the measurement method, the calibration procedure and results, the raw data treatment and visualization, and several applications using the large C-2DPSD-based diffractometer are reported.

Delay line readout of a large dimension multi-wire proportional chamber

A two dimensional multi-wire proportional chamber with delay line readout was developed, which has a large sensitive area of 30 cm × 30 cm. Two cathode planes using printed circuit boards are orthogonally placed to give two coordinates of the impact point of the particle. Signals collected from the cathode strips are amplified and discriminated from two ends of the delay line at each cathode board. By recording the time difference between the two discrimination pulses and the common gate pulse from anode wires, a coordinate position was reconstructed, and a position resolution of better than 1 mm could be obtained in the whole sensitive area along the anode wires.

Time and position sensitive single photon detector for scintillator read-out

We have developed a photon counting detector system for combined neutron and γ radiography which can determine position, time and intensity of a secondary photon flash created by a high-energy particle or photon within a scintillator screen. The system is based on a micro-channel plate photomultiplier concept utilizing image charge coupling to a position- and time-sensitive read-out anode placed outside the vacuum tube in air, aided by a standard photomultiplier and very fast pulse-height analyzing electronics. Due to the low dead time of all system components it can cope with the high throughput demands of a proposed combined fast neutron and dual discrete energy γ radiography method (FNDDER). We show tests with different types of delay-line read-out anodes and present a novel pulse-height-to-time converter circuit with its potential to discriminate γ energies for the projected FNDDER devices for an automated cargo container inspection system (ACCIS).

Time Projection Chambers with C-pads for heavy ion tracking

Time Projection Chambers with C-pads and integrated delay line readout were developed as position sensitive detectors for the Fragment separator at GSI Darmstadt. The main advantages of TPCs are a small amount of matter in the sensitive volume, high spatial resolution, and high tracking efficiency. Working parameters in experimental conditions are presented. Internal spatial resolutions of σ x = 88 μ m and σ y = 38 μ m were achieved. The tracking efficiency dependence on ion beam intensity was studied with 238U beam at 1 GeV/ u energy. Efficiency of more than 99% was achieved up to 40 kHz and over 90% for 250 kHz 238U beam intensity. Different kinds of ions from proton to uranium were measured in many experiments and confirmed the result obtained.

An X-ray imaging device based on a GEM detector with delay-line readout

An X-ray imaging device based on a triple-GEM (Gas Electron Multiplier) detector, a fast delay-line circuit with 700 MHz cut-off frequency and two dimensional readout strips with 150 μm width on the top and 250 μm width on the bottom, is designed and tested. The localization information is derived from the propagation time of the induced signals on the readout strips. This device has a good spatial resolution of 150 μm and works stably at an intensity of 105 Hz/mm2 with 8 keV X-rays.

High Spatial and Temporal Resolution Neutron Imaging With Microchannel Plate Detectors

Special microchannel plates (MCPs) developed by Nova Scientific Inc. incorporate high efficiency neutron conversion materials into the MCP to provide a high neutron stopping power. <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> B and <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">nat</sup> Gd have high interaction cross sections for thermal neutrons and their incorporation into MCP glass is a convenient way to make efficient MCPs for neutron detection with high spatial resolution. We have evaluated neutron event counting 2D imaging detectors using these MCPs with a cross delay line readout, cross strip readout, and a Medipix2 readout. Tests at several reactors with the cross delay line and cross strip readouts have established spatial resolution with neutrons as good as ~30 microns FWHM over a 27 mm diameter detector, with event rates approaching 1 MHz, low fixed pattern noise, event time tagging of 25 ns and intrinsic background rates of < 0.05 events cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> sec <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> . Evaluation of neutron sensing MCP detector with Medipix2 readout (14 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) has allowed operation at high counting rates (500 MHz) with the spatial resolution limited by the 55 micron pixel size of the Medipix2 readout. We have also used the Medipix2 for centroiding of neutron events to sub pixel resolution to obtain better spatial resolution (< 15 mum) for neutrons at reduced event rates (100 kHz). Initial measurements of thermal neutron detection efficiencies give values of 20% to 25% for thermal neutrons and 45% for cold neutrons without optimization of the detection geometry. Preliminary tests with shielding and a LaBr scintillator to gate neutron detections in coincidence with gamma rays produced by neutron interactions has enabled gamma ray rejection factors of 3 times 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> to be achieved. Further improvements in the neutron detection efficiency and gamma ray discrimination efficiency can be gained by optimization of the geometrical and electronic configurations.

Study of a multi-wire proportional chamber with a cathode strip and delay-line readout

The design principle for a multi-wire proportional chamber with a cathode strip and delay-line readout is described. A prototype chamber of a size of 10 cm ×10 cm was made together with the readout electronics circuit. A very clean signal with very low background noise was obtained by applying a transformer between the delay-line and the pre-amplifier in order to match the resistance. Along the anode wire direction a position resolution of less than 0.5 mm was achieved with a 55Fe-5.9 keV X ray source. The simple structure, large effective area and high position resolution allow the application of a gas chamber of this kind to many purposes.

Multi-Segment Position-Sensitive Detector for an X-ray Imaging Crystal Spectrometer

Multi-Segment Position-Sensitive Detector for an X-ray Imaging Crystal Spectrometer Jong Kyu Cheon Neutron Science Division, Korea Atomic Energy Research Institute, Daejeon 305-353 and Department of Physics, Kyungpook National University, Daegu 702-701 Myung Kook Moon and Chang Hee Lee Neutron Science Division, Korea Atomic Energy Research Institute, Daejeon 305-353 Shraddha S. Desai Solid State Physics Division, Bhabha Atomic Research Center, 400 085 Mumbai, India Uk Won Nam Space Science Division, Korea Astronomy and Space Science Institute, Daejeon 305-348 Sang Gon Lee and Jun Gyo Bak KSTAR Experiment and Operation Division, National Fusion Research Institute, Daejeon 305-333 Hee Dong Kang Department of Physics, Kyungpook National University, Daegu 702-701 (Received 3 November 2008) A two-dimensional segmented position sensitive detector (PSD) as a part of an X-ray imaging crystal spectrometer (XICS) for use in tokamak plasma experiments was developed. It is based on a multi-wire proportional counter (MWPC) using a delay-line readout method. The MWPC, necessary for recording plasma image data, provides the combined advantages of low neutron radiation sensitivity and large sensitive detection area. The fabricated PSD for the XICS is a four-segment MWPC that can be used in intense X-ray photon environments. PACS numbers: 29.40.Cs, 52.70.-m

Study of delay-line readout for GEM detector

The delay-line readout method is suitable for the position sensitive detectors in the early stage of high energy physics experiment at low-rate environment. In this paper, we present a fast delay-line circuit (cut off frequency: 0.7 GHz) equipped with a triple-GEM (Gas Electron Multiplier) detector for X-ray imaging. Using 8 keV X-rays and readout strips with 0.15 mm width and 0.4 mm pitch, the experiment result shows that the position resolution of the detecting system is less than 100 μ m at a counting rate of 10 5 Hz . A full simulation model has been developed for the design of delay-line electric circuit.

Novel instruments for ultra-soft X-ray emission spectroscopy

Two alternative instrument designs to the traditional Rowland grating spectrometer for high resolution ultra-soft X-ray spectroscopy are presented. The first instrument is a plane grating spectrometer using off-axis parabolic mirrors for collection and refocusing, and with a spatially resolving multichannel detector with delay line read-out. The instrument offers substantially higher performance in terms of resolution and sensitivity than traditional instruments. The second instrument is a Fourier transform spectrometer based on a grazing incidence Mach–Zehnder interferometer using wavefront dividing beamsplitters. The path length difference can be scanned over 0.1 mm, which corresponds to a resolution of 12 meV.

Neutron detectors for scattering experiments at HANARO

Position sensitive detectors (PSD) measure the distribution of scattered neutrons and are essential tools for neutron scattering experiments. Various types of neutron detectors used at neutron diffractometers are conventional tube detectors, 1-D and 2-D PSDs. Korea Atomic Energy Research Institute (KAERI) has been developing various kinds of PSDs to improve the instrument performance and to develop new scattering instruments. Our development work is initiated with 1-D PSD for residual stress analysis spectrometer and finally the technology is extended to development of 2-D PSD with planar and curved geometry. All PSDs are based on multiwire grid assembly with delay line readout method for position encoding, as the response is faster than charge division method and enables higher count rate capability. Design details and operational characteristics of some of the PSDs developed, for application at neutron scattering instruments are presented.

Spectral resolution measurement of an x-ray imaging crystal spectrometer for KSTAR

A spectral resolution measurement of the x-ray imaging crystal spectrometer for the Korea Superconducting Tokamak Advanced Research machine utilizing a segmented position-sensitive detector and time-to-digital converter based delay-line readout electronics was performed by using an x-ray tube in a laboratory. The measured spectral resolution is about 12,600, which means the actual energy resolution is 0.32 eV for the x-ray tube's bremsstrahlung peak energy of 4 keV. The results from the spectral resolution measurement are described.

Two-dimensional thermal neutron detector

A two-dimensional thermal neutron detector for neutron diffraction experiments has been developed and designed at the St. Petersburg Nuclear Physics Institute, Russian Academy of Sciences. The detector is based on a multiwire proportional chamber with cathode-strip delay line readout. The detector aperture is 170 × 300 mm2 and the anode wire spacing is 4 mm. The chamber is filled with a 1.5 atm 3He + 2 atm CF4 gas mixture. To conserve high purity of the gas mixture, all electrodes are made of quartz glass. The spatial resolution of the detector is 2.5 mm and the detection efficiency is 60% for 9 A neutrons.

The Calibration and Data Products of GALEX

We describe the calibration status and data products pertaining to the GR2 and GR3 data releases of the Galaxy Evolution Explorer (GALEX). These releases have identical pipeline calibrations that are significantly improved over the GR1 data release. GALEX continues to survey the sky in the Far Ultraviolet (FUV, ~154 nm) and Near Ultraviolet (NUV, ~232 nm) bands, providing simultaneous imaging with a pair of photon counting, microchannel plate, delay line readout detectors. These 1.25 degree field-of-view detectors are well-suited to ultraviolet observations because of their excellent red rejection and negligible background. A dithered mode of observing and photon list output pose complex requirements on the data processing pipeline, entangling detector calibrations and aspect reconstruction algorithms. Recent improvements have achieved photometric repeatability of 0.05 and 0.03 mAB in the FUV and NUV, respectively. We have detected a long term drift of order 1% FUV and 6% NUV over the mission. Astrometric precision is of order 0.5" RMS in both bands. In this paper we provide the GALEX user with a broad overview of the calibration issues likely to be confronted in the current release. Improvements are likely as the GALEX mission continues into an extended phase with a healthy instrument, no consumables, and increased opportunities for guest investigations.

Two-dimensional detector of thermal neutrons

A two-dimensional detector of thermal neutrons has been designed and constructed for neutron diffraction experiments at the St. Petersburg Nuclear Physics Institute. It is based on a multiwire proportional chamber (MWPC) with cathode strip delay line readout and has a sensitive area of 170×300 mm 2 and anode wire spacing is 4 mm. It operates with a gas mixture of 1.5 bar 3He+2 bar CF 4. To improve the gas purity by a few orders of magnitude, a new technology for fabrication of the detector's electrodes has been developed. An intrinsic resolution of 0.6 mm (FWHM) and a differential nonlinearity of ±5% are achieved. It was shown that the detector, whose efficiency is about 60% for 9 Å neutrons, has a resolution of 2.5 mm along the fine axis and about 4 mm for the perpendicular discrete axis. The dependence of the measured pulse height spectra from the applied high voltage and the electric field in the drift regions has been investigated. It turns out that for thermal neutrons the measured spectra are very similar to those obtained with proportional neutron counters filled with 10 bar 3He.