Papers by Keyword: Photon Counter

Abstract: Photon correlation technique is an effective method for measuring the particle size of sub-micron particles and nanoparticles. This tenchnology has a good prospect and commerical value. Photon counter is used in photon correlation spectroscopy experiment to gain the intensity of photon. In order to obtain the accurate values of the photon correlation, efficient and accurate photon counter must be designed. This paper presents two kinds of photon counters implemented by FPGA. The programming language used is Verilog HDL. The software design and system simulation are completed in the integration circumstance of ISE. Experiments show that our work is effective. They all have a simple circuit design, and easy to be upgraded. The accurate photon counters can meet the different requirements of photon correlation.

Abstract: In view of the extremely weak scattered light in PCS nano-particle size analyzer, a photon counter consisting of a PMT, amplifier, discriminator and pulse counter is designed. A double-counter structure is adopted in pulse counter in order to realize “glue” counter. The standard polystyrene particles are measured by using this counter, and the correlation of the collected photons was implemented. The experimental results show that the counter can reach the precision of PCS nano-particle size analyzer.

Abstract: The measurement and analysis system of nanoparticles size distribution was developed by using virtual instrument technology, while the photon counting technology was applied in the system to replace the expensive correlator. High speed photon pulse counter was designed. The real-time data of nanoparticles dynamic light scattering were analyzed in the mixed program of MATLAB and LabVIEW, where the time autocorrelation functions of nanoparticles light scattering signals of monodisperse and polydisperse are reversed by NNLS arithmetic. Experiments results show that the peak position, peak width and symmetry of inverse distribution are very close to the real simulate particles.

Abstract: A variety of silicon carbide (SiC) detectors have been developed to study their sensitivity, including Schottky photodiodes, p-i-n photodiodes, avalanche photodiodes (APDs), and single photon-counting APDs. Due to the very wide bandgap and thus extremely low leakage current, SiC photo-detectors show excellent sensitivity. The specific detectivity, D*, of SiC photodiodes are many orders of magnitude higher than the D* of other solid state detectors, and for the first time, comparable to that of photomultiplier tubes (PMTs). SiC APDs have also been fabricated to pursue the ultimate sensitivity. By operating the SiC APDs at a linear mode gain over 106, single photoncounting avalanche photodiodes (SPADs) in UV have been demonstrated.