Two optical configurations are commonly used in single-molecule fluorescence microscopy: point-like excitation and detection to study freely diffusing molecules, and wide field illumination and detection to study surface immobilized or slowly diffusing molecules. Both approaches have common features, but also differ in significant aspects. In particular, they use different detectors, which share some requirements but also have major technical differences. Currently, two types of detectors best fulfil the needs of each approach: single-photon-counting avalanche diodes (SPADs) for point-like detection, and electron-multiplying charge-coupled devices (EMCCDs) for wide field detection. However, there is room for improvements in both cases. The first configuration suffers from low throughput owing to the analysis of data from a single location. The second, on the other hand, is limited to relatively low frame rates and loses the benefit of single-photon-counting approaches. During the past few years, new developments in point-like and wide field detectors have started addressing some of these issues. Here, we describe our recent progresses towards increasing the throughput of single-molecule fluorescence spectroscopy in solution using parallel arrays of SPADs. We also discuss our development of large area photon-counting cameras achieving subnanosecond resolution for fluorescence lifetime imaging applications at the single-molecule level.

, 368 2013 Phil. Trans. R. Soc. B Guerrieri, F. Panzeri, I. Rech, A. Gulinatti, F. Zappa, M. Ghioni and S. Cova Siegmund, Anton S. Tremsin, John V. Vallerga, A. Cheng, M. Levi, D. Aharoni, K. Arisaka, F. Villa, F. X. Michalet, R. A. Colyer, G. Scalia, A. Ingargiola, R. Lin, J. E. Millaud, S. Weiss, Oswald H. W. single-molecule fluorescence microscopy Development of new photon-counting detectors for

Single-molecule observation, characterization and manipulation techniques have recently come to the forefront of several research domains spanning chemistry, biology and physics. Due to the exquisite sensitivity, specificity, and unmasking of ensemble averaging, single-molecule fluorescence imaging and spectroscopy have become, in a short period of time, important tools in cell biology, biochemistry and biophysics. These methods led to new ways of thinking about biological processes such as viral infection, receptor diffusion and oligomerization, cellular signaling, protein-protein or protein-nucleic acid interactions, and molecular machines. Such achievements require a combination of several factors to be met, among which detector sensitivity and bandwidth are crucial. We examine here the needed performance of photodetectors used in these types of experiments, the current state of the art for different categories of detectors, and actual and future developments of single-photon counting detectors for single-molecule imaging and spectroscopy.

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.

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.

The LHC beam luminosity monitor is based on the following principle. The neutrals that originate in LHC at every PP interaction develop showers of minimum ionizing particles in the absorbers placed in front of the separation dipoles. The shower energy, measured by suitable detectors in the absorbers is proportional to the number of neutral particles and, therefore, to the luminosity. The principle lends itself to a luminosity measurement on a bunch-by-bunch basis. However, to make such a measurement feasible, the system must comply with extremely stringent requirements. Its speed of operation must match the 40MHz bunch repetition rate of LHC. Besides, the detector must stand extremely high radiation doses. This paper discusses the solutions adopted to comply with these requirements.

In this paper we give a brief report on the development of simple direct- and indirect-detection imagers for proton radiography experiments. We outline a conceptual design for a novel, multi-frame 5 mega frames per second (Mfs) hybrid imager. The high-density interconnect is identified as a critical enabling technology. We present a description of a 3D electronics packaging cube, which was completed in a recent feasibility study.

A novel segmented multigap pressurized gas ionization chamber is being developed for optimization of the luminosity of the Large Hadron Collider (LHC). The ionization chambers are to be installed in the front quadrupole and 0/spl deg/ neutral particle absorbers in the high luminosity interaction regions (IRs) and sample the energy deposited near the maxima of the hadronic/electromagnetic showers in these absorbers. The ionization chambers are instrumented with low noise, fast pulse-shaping electronics to be capable of resolving individual bunch crossings at 40 MHz. In this paper, we report the initial results of our second test of this instrumentation in a super proton synchrotron (SPS) external proton beam. Single 300 GeV protons are used to simulate the hadronic/electromagnetic showers produced by the forward collision products from the interaction regions of the LHC. The capability of instrumentation to measure the luminosity of individual bunches in a 40 MHz bunch train is demonstrated.

We constructed two small-area pixelated detectors, which can record signals produced by 800-MeV proton beam micropulses with a repetition rate of 358 ns. The first detector was built around a two-dimensional (2-D) photodiode array. The array was illuminated by light emitted by a monolithic 1.7-mm-thick lutetium oxy-orthosilicate (LSO) scintillator and imaged by a simple optical system. The other detector was a hydrogen ion chamber operated at I to 2.5 atm. The anode was divided into an array of 8 x 8 1 mm(2) pixels. The fast positive-ion drift velocity in hydrogen helps to minimize the space charge build up. However, for beam pulses spaced in time closer than 1mus, there appears to be a substantial accumulation of space charge. The electronic readout chain, for each of the 64 channels, consisted of an externally clocked fast-gated integrator and an amplifier coupled to an on-board analog-to-digital converter (ADC) and a first-in-first-out storage (FIFO). The detectors were tested with beam pulses up to 4 x 10(6) protons per mm(2) delivered in 30 to 120 ns wide microbursts.

The front IR quadrupole absorbers (TAS) and the IR neutral particle absorbers (TAN) in the high-luminosity insertions of the Large Hadron Collider (LHC) each absorb approximately 1.8 TeV of forward collision products on average per pp interaction (similar to235 W at design luminosity Of 10(34) cm(-2) s(-1)). This secondary particle flux can be exploited to provide a useful storage ring operations tool for optimization of luminosity. A novel segmented, multigap, pressurized gas ionization chamber is being developed for sampling the energy deposited near the maxima of the hadronic/electromagnetic showers in these absorbers. The system design choices have been strongly influenced by optimization of signal-to-noise ratio and by the very high radiation environment. The ionization chambers are instrumented with low-noise, fast, pulse-shaping electronics to be capable of resolving individual bunch crossings at 40 MHz. Data on each bunch are to be separately accumulated over multiple bunch crossings until the desired statistical accuracy is obtained. At design luminosity, approximately 2 x 10(3) bunch crossings will suffice for a 1% luminosity measurement. In this paper, we report the first experimental results of the ionization chamber and analog electronics. Single 450-GeV protons from the SPS at CERN are used to simulate the hadronic/electromagnetic showers produced by the forward collision products from the interaction regions of the LHC.

This paper discusses the criteria that have been adopted to optimize the signal processing in a shower detector to be employed as LHC beam luminosity monitor. The original aspect of this instrument is its ability to operate on a bunch-by-bunch basis. This means that it must perform accurate charge measurements at a repetition rate of 40 MHz. The detector must withstand an integrated dose of 100 Grad, that is, two to three orders of magnitude beyond those expected in the experiments. To meet the above requirements, an ionization chamber consisting of several gaps of thickness 0.5 mm, filled with a gas that is expected to be radiation resistant, has been designed. Crucial in the development of the system is the signal processing, as the electronics noise may set the dominant limitation to the accuracy of the measurement. This is related to two aspects. One is the short time available for the charge measurement. The second one is the presence of a few meter cable between the detector and the preamplifier, as this must be located out of the region of highest radiation field. Therefore the optimization of the signal-to-noise ratio requires that the best configuration of the chamber gaps be determined under the constraint of the presence of a cable of non negligible length between detector and preamplifier. The remote placement of the amplifying electronics will require that the front-end electronics be radiation hard although to a lesser extent than the detector.

This paper addresses the design of a system intended to readout multiparametric information from a matrix of pixels. The system presented acquires the charge associated with the signal and provides a timing information from each pixel. Although it lends itself to a broad range of time-correlated imaging situations involving any kind of pixel matrices, the design constraints assumed are particularly tailored to the application with pixels that sense the output charge distribution from a microchannel plate (MCP). The combination of a microchannel plate and a pixel matrix is an extremely versatile detector and the readout system must be able to fully exploit the intrinsically high position resolution and time accuracy featured by the MCP. The behavior of the readout system described in this paper is based upon advanced concepts to meet the above application requirements and is believed to provide a significant functional improvement over conventional pixel systems

LBNL· 455 49 ERNEST ORLANDO LAWRENCE BERKELEY NATIONAL LABORATORY Status Report on the Development of Instrumentation for Bunch by Bunch Measurement and Optimisation of Luminosity in the tHC w.e. Turner, P.S. Datte, P.F. Manfredi, ].E. Millaud, N.V. Mokhov, M. Placidi, V. Re, and H. Schmickler Accelerator and Fusion Research Division May 2000 Prepared for Proceedings of the US-LHC Collaboration Meeting on Accelerator Physics Experiments for Future Hadron Colliders Brookhaven National Laboratory 22-23 February, 2000

The front IR quadrupole absorbers (TAS) and the IR neutral particle absorbers (TAN) in the high luminosity insertions of the Large Hadron Collider (LHC) each absorb approximately 1.8 TeV of forward collision products on average per pp interaction (/spl sim/235 W at design luminosity 10/sup 34/ cm/sup -2/ s/sup -1/). This secondary particle flux can be exploited to provide a useful storage ring operations tool for optimization of luminosity. A novel segmented, multi-gap, pressurized gas ionization chambers is being developed for sampling the energy deposited near the maxima of the hadronic/electromagnetic showers in these absorbers. The ionization chamber must be capable of resolving individual bunch crossings at 40 MHz. The ionization chamber is segmented into quadrants; each quadrant consists of sixty (40/spl times/40) mm/sup 2/ Cu plates 1.0 mm thick, with 0.5 mm gaps. The 0.5 mm gap width has been chosen so that the time for the ionization electrons to drift across the gap, is short enough to produce at the output of the shaping amplifier, a signal that returns to the base line is less than the 25 ns bunch spacing of the LHC. From noise considerations in the presence of a cable the stack of plates are connected electrically 10 in parallel, 6 in series to achieve an equivalent detector capacitance C/sub d//spl sim/50 pF. This type connection forms an electrode inductive L/sub e/ and electrode capacitive C/sub e/ network that must be optimized to transfer charge from the chamber to the sensing amplifier. This paper describes the design of the collection electrodes optimized for 40 MHz operation.

This report discusses the problems of release of items from facilities and installations where radiation-based activities have been carried out. Several situations are reviewed and their release problems are discussed in detail. Particular attention is devoted to the assessment of the activity of the items to be released. A correct assessment of the activity will help the decision about the final use of the items removed from the radiation-related facility, either re-use, entering the public market, recycling, disposal and storage under different procedures. Even the final destination of the building which hosted the facility needs to be decided on the basis of an accurate assessment of the residual activity. The assessment of the activity, besides being fundamental in guaranteeing a safe approach to the procedures related to the release may result in a substantial profit. This is the case of items whose level of activity is so low that they can be put on the public market, reused or recycled for final product subject to very stringent radiation safety requirements. It will be shown that detector techniques play a fundamental role in the release process. In particular, the low-level counting techniques are fundamental in establishing whether or not the unrestrained release is feasible or not.