Masters internship

Building a dynamic light scattering setup to study dense colloidal systems

Masters internship at the sector of Biological and Soft Systems (BSS) of the Cavendish Laboratory, University of Cambridge. Supervisors: dr. Erica Eiser & Taiki Yanagishima, MSc.

This report describes the construction of both the hardware and the software of a dynamic light scattering setup. The essential hardware consists of a 632 nm laser, a cuvette holder and a silicon multi-pixel photon counter that detects single photons with a sampling frequency of 320 MHz. The setup allows measurements at 90º only. The components are interconnected with optical fibers enabling homodyne measurements.

The obtained, binary signal is processed by a fast coarse-graining algorithm and autocorrelated using software that was developed in-house. A Monte-Carlo simulation of a colloid in an optical trap is employed to test the software program. On a dedicated computer the analysis can be performed at a sampling rate of up to ~3 MHz. The processed data is fitted, so that the initial parameters of the simulation could be retrieved with an error in the characteristic delay time as low as 0.37%. The statistical error estimate in the measured ensemble average is found to be 9.0% max.