Development of a multi-channel power supply for silicon photo-multipliers used with inorganic scintillators

The motivation of the current R&D project is based upon the requirements of the JEDI international collaboration aiming to measure Electric Dipole Moments (EDMs) of charged particles in storage rings. One of the most important elements of such an experiment will be a specially designed polarimeter with the detection system based on a modular inorganic scintillator (LYSO crystal) calorimeter. The calorimeter modules are read out by Silicon Photo Multipliers (SiPMs). This paper describes the development of a multi-channel power supply for the polarimeter modules, providing very stable and clean bias voltages for SiPMs. In order to ensure the best possible performance of SiPMs in conjunction with the crystal-based calorimeter modules and to guarantee the required level of calorimeter stability, several quality requirements have to be met by the power supply. Additionally, it is required to provide features including remote control via the network, ramping of the output voltage, measuring and sending the information about its output voltages and currents, etc. The obtained results demonstrate that the goals for the JEDI polarimeter are met. The developed hardware will be useful in other fields of fundamental and applied research, medical diagnostic techniques and industry, where SiPMs are used

Exploring the structure-properties relationships of novel polyamide thin film composite membranes

Polysulfone (PSf) is a traditional material widely used for manufacturing microfiltration and ultrafiltration membranes by non-solvent induced phase separation (NIPS) process. However, the hydrophobic nature of PSf makes the membranes prone to protein fouling. In order to create non fouling surfaces and further decrease the pore size, the membrane pores can be modified by different strategies as atom transfer radical polymerization [1]. However, these strategies are not adopted by industry due to either cost or technical challenges. This contribution presents the preparation of asymmetric membranes by in situ interfacial polymerization (IP) of thin films (TF) on the PSf support surface in order to form a new polyamide (PA) layer [2]. The new PA is hydrophilic and negatively charged, and has prospects in application such as removal of bacteria and heavy metal ions from waste water. The pore size of the barrier layer can be controlled by adjusting the cross-linking degree and chemical composition of the PA network. This work is an attempt to prepare a new PA TF composite membrane and investigate the effect of different amines’ structures on the final membrane properties. Characterization of the PA surface morphology and chemical structure includes scanning electron microscopy, atomic force microscopy, attenuated total reflectance Fourier transform infrared spectroscopy, and streaming potential measurements. Rhodamine B cannot stain the TF composite membrane surface unlike the virgin PSf surface. Furthermore, the water flux decreases from 220 L/h/m²/bar for the PSf membrane to 1.5 L/h/m²/bar for the TF composite membrane. It is therefore concluded that a dense PA TF forms on the porous PSf support after the IP. In order to confirm the antifouling properties, bovine serum albumin/phosphate-bufered saline solution was tested as a model solution to measure flux recovery. References[1] Han-Bang Dong, You-Yi Xu, Zhuan Yi, Jun-Li Shi, Modification of polysulfone membranes via surface-initiated atom transfer radical polymerization, Applied Surface Science, 255, (2009), 8860-8866.[2] Yu Jun Song, Patricia Sun, Lawrence L. Henry, Benhui Sun, Mechanism of structure and performance controlled thin film composite membrane formation via interfacial polymerization process, Journal of Membrane Science, 251, (2005) 67-79