Multichannel Time-Stamping-Based Correlator and Hardware Simulator for Photon Correlation Spectroscopy

In fluorescence correlation spectroscopy and dynamic light scattering, digital correlators acquire the autocorrelation function of detected photons to measure diffusional dynamics of biomolecules and small particles. Multi-channel data from different wavelengths or scattering angles provide increased information for resolving multiple species. Similarly, in single-molecule spectroscopy and in experiments on photon entanglement, there is a need to acquire time stamps of photons from multiple detectors. To enable such advances, a cost-effective Multichannel Time-Correlator (MTC) and a Multichannel Hardware Simulator (MHS) were developed, each based on a reconfigurable digital input/output card, recently available from National Instruments. The field-programmable-gate-array (FPGA) cores of the cards are programmed to implement counters and first-infirst- out (FIFO) buffers for data transfer by direct-memory-access (DMA). The MTC scans 16 digital inputs each 12.5 nanoseconds to detect voltage pulses coming from a multichannel single-photon detector. Whenever one or more pulses are detected, the timing, which is recorded as a 32-bit timestamp, and a 16-bit flag that specifies the channel(s) are sent to the host computer (PC) for further analysis and storage to a binary file. The DMA data transfer to or from the host PC allows a sustained photon rate of \u3e10 million per second among the 16 channels. An algorithm simultaneously calculates all 16x16 autocorrelation and cross-correlation functions for logarithmically spaced delays directly from the timestamps and channel flags. The MHS reads simulated timestamp and channel data from a binary file and sends the information by DMA to the FPGA card, which uses the received data to generate voltage pulses at 16 digital outputs to thereby simulate the signal from a 16-channel single-photon detector. When the MHS is connected to the MTC, each within a separate PC, the recovered timestamp data is correct to within the expected digital error of +/- 1 timing count

Research Proposal for an Experiment to Search for the Decay {\mu} -> eee

We propose an experiment (Mu3e) to search for the lepton flavour violating decay mu+ -> e+e-e+. We aim for an ultimate sensitivity of one in 10^16 mu-decays, four orders of magnitude better than previous searches. This sensitivity is made possible by exploiting modern silicon pixel detectors providing high spatial resolution and hodoscopes using scintillating fibres and tiles providing precise timing information at high particle rates.Comment: Research proposal submitted to the Paul Scherrer Institute Research Committee for Particle Physics at the Ring Cyclotron, 104 page

Run 2 Upgrades to the CMS Level-1 Calorimeter Trigger

The CMS Level-1 calorimeter trigger is being upgraded in two stages to maintain performance as the LHC increases pile-up and instantaneous luminosity in its second run. In the first stage, improved algorithms including event-by-event pile-up corrections are used. New algorithms for heavy ion running have also been developed. In the second stage, higher granularity inputs and a time-multiplexed approach allow for improved position and energy resolution. Data processing in both stages of the upgrade is performed with new, Xilinx Virtex-7 based AMC cards.Comment: 10 pages, 7 figure

Stellar intensity interferometry: Experimental steps toward long-baseline observations

Experiments are in progress to prepare for intensity interferometry with arrays of air Cherenkov telescopes. At the Bonneville Seabase site, near Salt Lake City, a testbed observatory has been set up with two 3-m air Cherenkov telescopes on a 23-m baseline. Cameras are being constructed, with control electronics for either off- or online analysis of the data. At the Lund Observatory (Sweden), in Technion (Israel) and at the University of Utah (USA), laboratory intensity interferometers simulating stellar observations have been set up and experiments are in progress, using various analog and digital correlators, reaching 1.4 ns time resolution, to analyze signals from pairs of laboratory telescopes.Comment: 12 pages, 3 figur

The design of fluorescence correlation spectroscopy for single molecule techniques

The ribosome is responsible for protein synthesis--a critical process in creating essential proteins for cell survival. Though bulk techniques yield valuable results about the structure of the ribosome, bulk techniques are not ideal in examining ribosomal dynamics and understanding kinetics involved in protein synthesis. On the contrary, the single molecule spectroscopy techniques are ideal in investigating the mechanisms of ribosome dynamics in real-time under equilibrium conditions. The latest advances in single molecule biophysics have opened numerous opportunities in the biological world to study the dynamics of molecules in real-time. Single molecule techniques such as Fluorescence Correlation Spectroscopy (FCS) have opened opportunities to study the ribosome as well as other ribosomal proteins. FCS is used to investigate diffusion coefficients, concentration, and kinetics of biological samples. In this thesis, we address the process of assembling an FCS system, as well as the design of a high-speed correlator. The high-speed correlator allows the software to handle the high data counts that can occur in single molecule experiments. A field-programmable gate arrays (FPGA) dual correlator and a multi-tau correlator are designed to handle the noise and high count rates that can dominate the signal. Also addressed in this thesis are ideal experimental conditions for successfully obtaining and troubleshooting results received from FCS curves.Includes bibliographical reference

A 32-channel photon counting module with embedded auto/cross-correlators for real-time parallel fluorescence correlation spectroscopy

Fluorescence correlation spectroscopy (FCS) is a well-established technique to study binding interactions or the diffusion of fluorescently labeled biomolecules in vitro and in vivo. Fast FCS experiments require parallel data acquisition and analysis which can be achieved by exploiting a multi-channel Single Photon Avalanche Diode (SPAD) array and a corresponding multi-input correlator. This paper reports a 32-channel FPGA based correlator able to perform 32 auto/cross-correlations simultaneously over a lag-time ranging from 10 ns up to 150 ms. The correlator is included in a 32 × 1 SPAD array module, providing a compact and flexible instrument for high throughput FCS experiments. However, some inherent features of SPAD arrays, namely afterpulsing and optical crosstalk effects, may introduce distortions in the measurement of auto- and cross-correlation functions. We investigated these limitations to assess their impact on the module and evaluate possible workarounds