Cross Delay Line Research Articles

High-Resolution Imager Based on Time-to-Space Conversion

We present an high-resolution 3D (X,Y,t) imager for time-resolved experiments based on time-to-space conversion. The system uses Cross Delay-Line detectors (CDL) for particle identification and a fully-configurable digital processor based on Field Programmable Gate Arrays (FPGAs) for the 3D image reconstruction. The instrument reaches a spatial resolution of 45 μm FWHM (i.e.,18 μm r.m.s.) and a temporal precision of 15 ps r.m.s.. The detection rate achieved is 10 Mcps, with a dead-time below 7 ns, leading to a global throughput up to 6 Gb/s. In addition to the state-of-the-art performance, the innovative aspect of the presented contribution resides in the complete reconfigurability of the instrument: it is, in fact, the first time that the Time-to-Digital Converter (TDC) used for the time-to-space conversion, has been fully implemented in programmable logic, without the use of dedicated Application Specific Integrated Circuit (ASIC) components. This advancement allows to adapt the instrument to the experimental setup without undergoing impractical hardware modifications.

Lightsheet fluorescence lifetime imaging microscopy with wide-field time-correlated single photon counting.

We report on wide‐field time‐correlated single photon counting (TCSPC)‐based fluorescence lifetime imaging microscopy (FLIM) with lightsheet illumination. A pulsed diode laser is used for excitation, and a crossed delay line anode image intensifier, effectively a single‐photon sensitive camera, is used to record the position and arrival time of the photons with picosecond time resolution, combining low illumination intensity of microwatts with wide‐field data collection. We pair this detector with the lightsheet illumination technique, and apply it to 3D FLIM imaging of dye gradients in human cancer cell spheroids, and C. elegans.

Microchannel Plate Imaging Detectors for High Dynamic Range Applications

Microchannel plate (MCP) imaging detectors are widely used in astronomical, biological imaging and remote sensing applications. Photon counting mode imagers with event timing can make use of the high spatial resolution (~10- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$50~\mu \text {m}$ </tex-math></inline-formula> ) and very high time resolution (subnanoseconds) of MCP detectors to enhance the performance of such detectors in dynamic environments (for example airborne surveillance of moving objects, LIDAR, and 3-D topographic imaging). The total information that can be collected is limited by the dynamic range of the detector (cross delay line sensors can support detected photon rates up to ~2 MHz over the entire effective area). The ideal sensor for many applications, such as bright images or fast transient behavior, would combine the desirable attributes of high spatial and time resolution for each detected photon with event rates of 100 MHz or more. A new class of MCPs constructed using atomic layer deposition (ALD) on borosilicate glass microcapillary arrays is providing enhancements towards this goal. The ALD MCP manufacturing process decouples the operational functionalization from the substrate fabrication, opening the door for new resistive layers and high secondary emissive materials. Many improvements over traditional MCPs have been demonstrated, including robust substrates able to withstand high processing temperatures, very low background rates, high stable gains, and low outgassing. Higher global photon counting rates can be supported by ALD MCP detector schemes while greatly improving the instrument lifetime. Additionally, the robustness of these MCPs provide them with surface properties capable of supporting the deposition of a wide range of efficient photocathode materials (III-V), which require high processing temperatures (>500 C), to achieve a high quantum efficiency at near UV to near IR wavelengths. Sealed tube sensors incorporating nano-engineered MCPs can support nonproliferation and remote sensing enabling technologies by advancing the state-of the-art single-photon electro-optical remote sensing detectors. The progress of this effort, including results from the deposition of opaque photocathodes directly onto the front surface of the MCPs and the performance and lifetime characteristics of open faced and seal tube detectors, is reported here.

A wide-field TCSPC FLIM system based on an MCP PMT with a delay-line anode.

We report on the implementation of a wide-field time-correlated single photon counting (TCSPC) method for fluorescence lifetime imaging (FLIM). It is based on a 40 mm diameter crossed delay line anode detector, where the readout is performed by three standard TCSPC boards. Excitation is performed by a picosecond diode laser with 50 MHz repetition rate. The photon arrival timing is obtained directly from the microchannel plates, with an instrumental response of ∼190 to 230 ps full width at half maximum depending on the position on the photocathode. The position of the photon event is obtained from the pulse propagation time along the two delay lines, one in x and one in y. One end of a delay line is fed into the "start" input of the corresponding TCSPC board, and the other end is delayed by 40 ns and fed into the "stop" input. The time between start and stop is directly converted into position, with a resolution of 200-250 μm. The data acquisition software builds up the distribution of the photons over their spatial coordinates, x and y, and their times after the excitation pulses, typically into 512 × 512 pixels and 1024 time channels per pixel. We apply the system to fluorescence lifetime imaging of cells labelled with Alexa 488 phalloidin in an epi-fluorescence microscope and discuss the application of our approach to other fluorescence microscopy methods.

Picosecond wide-field time-correlated single photon counting fluorescence microscopy with a delay line anode detector

We perform wide-field time-correlated single photon counting-based fluorescence lifetime imaging (FLIM) with a crossed delay line anode image intensifier, where the pulse propagation time yields the photon position. This microchannel plate-based detector was read out with conventional fast timing electronics and mounted on a fluorescence microscope with total internal reflection (TIR) illumination. The picosecond time resolution of this detection system combines low illumination intensity of microwatts with wide-field data collection. This is ideal for fluorescence lifetime imaging of cell membranes using TIR. We show that fluorescence lifetime images of living HeLa cells stained with membrane dye di-4-ANEPPDHQ exhibit a reduced lifetime near the coverslip in TIR compared to epifluorescence FLIM.

Characterization of a detector chain using a FPGA-based time-to-digital converter to reconstruct the three-dimensional coordinates of single particles at high flux.

We report on the development of a novel FPGA-based time-to-digital converter and its implementation in a detection chain that records the coordinates of single particles along three dimensions. The detector is composed of micro-channel plates mounted on top of a cross delay line and connected to fast electronics. We demonstrate continuous recording of the timing signals from the cross delay line at rates up to 4.1 × 10(6) s(-1) and three-dimensional reconstruction of the coordinates up to 3.2 × 10(6) particles per second. From the imaging of a calibrated structure we measure the in-plane resolution of the detector to be 140(20) μm at a flux of 3 × 10(5) particles per second. In addition, we analyze a method to estimate the resolution without placing any structure under vacuum, a significant practical improvement. While we use UV photons here, the results of this work apply to the detection of other kinds of particles.

Photoionization and Velocity Map Imaging spectroscopy of atoms, molecules and clusters with Synchrotron and Free Electron Laser radiation at Elettra

Advances in laser and Synchrotron Radiation instrumentation are continuously boosting fundamental research on the electronic structure of matter. At Elettra the collaboration between several groups active in the field of atomic, molecular and cluster physics and the Instrumentation and Detector Laboratory has resulted in an experimental set-up that successfully tackles the challenges posed by the investigation of the electronic structure of isolated species in the gas phase. The use of Synchrotron Radiation (SR) and Free Electron Laser (FEL) light, allows to cover a wide spectrum of targets from energetic to dynamics. We developed a Velocity Map Imaging (VMI) spectrometer that allows to perform as well SR as FEL experiments, just by changing part of the detection system.In SR experiments, at the Gasphase beamline of Elettra, a cross delay line detector is used, coupled to a 4-channel time-to-digital converter that reconstructs the position of the electrons. Simultaneously, a Time-of-Flight (TOF) mass spectrometer is used to acquire photoion spectra. Such a system allows PhotoElectron-PhotoIon-Coincidence (PEPICO) spectroscopy of atoms, molecules and clusters. In FEL experiments (notably differing from SR experiments in the much higher rate of events produced and detected, which forces one to forfeit coincidence detection), at the Low Density Matter (LDM) beamline of FERMI, a Micro Channel Plate (MCP) a phosphor screen and a CCD camera are used instead, capable of shot-by-shot collection of practically all events, albeit without time resolution.

Application of atomic layer deposited microchannel plates to imaging photodetectors with high time resolution

Novel microchannel plates have been constructed using borosilicate glass micro-capillary array substrates with 20µm and 10µm pores and coated with resistive, and secondary electron emissive, layers by atomic layer deposition. Microchannel plates in 33mm, 50mm and 20cm square formats have been made and tested. Although their amplification, imaging, and timing properties are comparable to standard glass microchannel plates, the background rates and lifetime characteristics are considerably improved. Sealed tube detectors based on the Planacon tube, and a 25mm cross delay line readout tube with a GaN(Mg) opaque photocathode deposited on borosilicate microchannel plates have been fabricated. Considerable progress has also been made with 20cm microchannel plates for a 20cm format sealed tube sensor with strip-line readout that is being developed for Cherenkov light detection.

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.

BVIT: A Visible Imaging, Photon Counting Instrument on the Southern African Large Telescope for High Time Resolution Astronomy

Abstract The Berkeley Visible Imaging Tube (BVIT) was installed on the Southern African Large Telescope (SALT) in January 2009 and subsequently refurbished in August 2010. BVIT is an imaging, photon counting camera with multi-color (B, V, R, and H-α) capability. At the heart of BVIT is a 25 mm diameter active area, microchannel plate, sealed tube device with a visible photocathode and a cross-delay line readout. For each detected event the readout electronics record an X, Y position, an event pulse size (P), and an arrival time (T) — recorded with 25 ns precision. Post-acquisition processing of the X, Y, P, and T photon lists can be used to build images and light curves (to whatever sampling rate is supported by the signal to noise of the source as detected). The instrument design is presented as well as some examples of data acquired with the instrument on SALT.

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.

Image charge multi-role and function detectors

The image charge technique used with microchannel plate imaging tubes provides several operational and practical benefits by serving to isolate the electronic image readout from the detector. The simple dielectric interface between detector and readout provides vacuum isolation and no vacuum electrical feed-throughs are required. Since the readout is mechanically separate from the detector, an image tube of generic design can be simply optimised for various applications by attaching it to different readout devices and electronics. We present imaging performance results using a single image tube with a variety of readout devices suited to differing applications: (a) A four electrode charge division tetra wedge anode, optimised for best spatial resolution in photon counting mode. (b) A cross delay line anode, enabling higher count rate, and the possibility of discriminating near co-incident events, and an event timing resolution of better than 1 ns. (c) A multi-anode readout connected, either to a multi-channel oscilloscope for analogue measurements of fast optical pulses, or alternately, to a multi-channel time correlated single photon counting (TCSPC) card.

A two-dimensional detector for pump-and-probe and time resolved experiments

We present a new bidimensional detector setup, based on cross delay line technology, specifically developed for time resolved experiments and particularly suited to work in conjunction with pump-and-probe systems. Thanks to the particular architecture of the acquisition electronics, the detector is able to correlate each event with the time it occurred in a way which preserves the picoseconds time resolution of pump-and-probe techniques and, more generally, can perform time resolved acquisition in the nanosecond or picoseconds scale. The acquisition setup count rate, up to more than 4 Mcounts/s in time resolved mode, exceeds the performances of the best two-dimensional detectors working in counting mode presently available on electron analysers. First experimental results, obtained both on bench tests and in UHV conditions, where the detector has been mounted on an electron analyser, confirm the validity of the approach and show the potentiality of time resolved acquisition applied to electron spectroscopy analysis.

High Resolution Photon Counting Detection System for Advanced Inelastic X-Ray Scattering Studies

High brilliance and high spectral resolution of synchrotron sources and associated optics enable a large number of soft-X-ray spectroscopic studies such as inelastic X-ray scattering, which is becoming a technique of choice for the investigation of the electronic properties of complex materials. The resolution of the detection system in such experiments has to match the accuracy of the probe beam in order to take the full advantage of the performance of modern synchrotron sources. In this paper we describe our advanced photon counting detection system capable of simultaneously registering both position and time of individual photons with 2-dimensional spatial accuracy of < 50 mum and timing accuracy of < 130 ps FWHM. The open face, 25 mm active area detector consists of a Z-stack of microchannel plates and a cross delay line readout and has a dark count rate of only a few counts per second. The associated electronics allows event counting rates up to ~400 KHz with 10% dead time for randomly events. We present the results of our first measurements of delayed fluorescence from different materials performed at the Advanced Light Source. Time and angular resolved fluorescence measurements allowed us to separate images for the prompt elastically scattered and the delayed photons. The detector can also distinguish registration of electrons, ions or photons by variation of the potential on its input mesh. These results demonstrate the capabilities of our detection system, which is currently being integrated into an advanced time resolved X-ray emission spectroscopy system.

A high spatial resolution event counting neutron detector using microchannel plates and cross delay line readout

We have developed and tested a 25 mm aperture event counting two-dimensional imaging detector with high time resolution using neutron-sensitive microchannel plates and a cross delay line readout anode. Spatial resolution of better than 17 μm RMS has been demonstrated along with thermal neutron detection efficiencies of about 20%. Each event can be time tagged to better than 25 ns and event rates in excess of 1 MHz may be achieved.

High spatial resolution neutron sensing microchannel plate detectors

Neutron sensing microchannel plates (MCPs) developed by Nova Scientific Inc. incorporate high-efficiency neutron conversion materials in the MCP glass to provide a high neutron stopping power. We have developed and tested neutron event counting 2D-imaging detectors using these MCPs with three different imaging systems, a cross delay line readout, a cross strip readout, and a MEDIPIX readout. Tests at MNRC and NIST with the cross delay line and cross strip readouts have established spatial resolution with neutrons as good as 17 μm RMS over 27 mm, with event rates of 1 MHz, event time tagging of 25 ns and intrinsic background rates of <0.05 events cm −2 s −1. MEDIPIX readouts for neutron imaging have poorer spatial resolution (55 μm) and event timing, but are capable of even higher rates (GHz).

MCP-based dual band far UV spectrograph with single channel readouts for space use

A compact far ultraviolet (FUV) spectrograph has been developed and applied to space observation on a micro-satellite. The dual channel imaging spectrograph utilized two micro-channel plate (MCP) detectors with a single crossed delay line (XDL) anode to record photon arrival events. The unconventional anode design allows for the use of a single set of position encoding electronics for both detector fields, thereby reducing the size, weight, and power of the associated electronics. The ground and on-orbit performance tests verified the successful application of the system for astrophysical observations. In this note, we report the design, the development, and the test results of the system, focusing on the XDL anode system.

Performance of a local electrode atom probe

AbstractThe performance of a local electrode atom probe with a crossed delay line detector has been characterized. The local electrode atom probe with its short flight path and high speed (up to 250 kHz) pulse generator has made dramatic, orders of magnitude improvements in the data acquisition rate and the size of the analyzed volume compared to previous types of three‐dimensional atom probes. Sustained detection rates of up to 17% ions per field evaporation pulse have been achieved with data collection rates of up to 2 million atoms per minute. Preferential evaporation is substantially reduced due to the smaller proportion of time spent at the standing voltage enabling lower pulse fractions to be routinely used. A procedure for aligning the specimen with the aperture in the local electrode is described. Published in 2007 by John Wiley &amp; Sons, Ltd.

Photon-counting H33D detector for biological fluorescence imaging

We have developed a photon-counting High-temporal and High-spatial resolution, High-throughput 3-Dimensional detector (H33D) for biological imaging of fluorescent samples. The design is based on a 25 mm diameter S20 photocathode followed by a 3-microchannel plate stack, and a cross-delay line anode. We describe the bench performance of the H33D detector, as well as preliminary imaging results obtained with fluorescent beads, quantum dots and live cells and discuss applications of future generation detectors for single-molecule imaging and high-throughput study of biomolecular interactions.

A space- and time-resolved single photon counting detector for fluorescence microscopy and spectroscopy.

We have recently developed a wide-field photon-counting detector having high-temporal and high-spatial resolutions and capable of high-throughput (the H33D detector). Its design is based on a 25 mm diameter multi-alkali photocathode producing one photo electron per detected photon, which are then multiplied up to 107 times by a 3-microchannel plate stack. The resulting electron cloud is proximity focused on a cross delay line anode, which allows determining the incident photon position with high accuracy. The imaging and fluorescence lifetime measurement performances of the H33D detector installed on a standard epifluorescence microscope will be presented. We compare them to those of standard single-molecule detectors such as single-photon avalanche photodiode (SPAD) or electron-multiplying camera using model samples (fluorescent beads, quantum dots and live cells). Finally, we discuss the design and applications of future generation of H33D detectors for single-molecule imaging and high-throughput study of biomolecular interactions.