Commercial counterboard for 10 ns software correlator for photon and fluorescence correlation spectroscopy

A 10 ns time resolution, multi-tausoftwarecorrelator, capable ofcomputing simultaneous autocorrelation (A-A, B-B) and cross (A-B)correlation functions at count rates up to ∼10 MHz, with no data loss, has been developed in LabVIEW and C++ by using the National Instrument timer/counterboard (NI PCIe-6612) and a fast PersonalComputer (PC) (Intel Core i7-4790 Processor 3.60 GHz ). Thecorrelator works by using two algorithms: for large lag times (τ≳ 1μs), a classical time-mode scheme, based on themeasure of the number of pulses per time interval, is used; differently, forτ≲ 1μs a photon-mode (PM) scheme is adopted and thecorrelation function is retrieved from the sequence of the photon arrival times. Single auto- and cross-correlationfunctions can be processed online in full real time up to count rates of ∼1.8 MHz and ∼1.2 MHz, respectively. Two autocorrelation (A-A, B-B) and a crosscorrelation (A-B)functions can be simultaneously processed in full real time only up to count rates of ∼750 kHz. At higher count rates, the online processing takes place in a delayed modality, but with no data loss. When tested with simulatedcorrelation data and latex spheressolutions, the overall performances of thecorrelator appear to be comparable with those of commercialhardwarecorrelators, but with several nontrivial advantages related to its flexibility, low cost, and easy adaptability to future developments of PC and data acquisition technology.

Source: Review of Scientific Instruments - November 16, 2016 Category: Physics Authors: Matteo Molteni and Fabio Ferri Source Type: research