Development of a Pulse Shape Discrimination CMOS ASIC

Southern Illinois University At Edwardsville, Edwardsville IL

Investigators

Abstract

There is one feature of the (nuclear) interaction that binds nuclei and supports large (neutron) stars which is poorly understood. This feature is how the binding changes with the density of the matter when the neutron-proton ratio is far different than one. For example, when there are far more neutrons than protons. Determination of the masses of (neutron) stars, as well as laboratory measurements of the dynamics of terrestrial collisions between nuclei can help determine this unknown dependence. We are involved in the latter type of research. Our experiments require large arrays of detectors. Some of these detector arrays only require the energy deposited in each detector element and when in time the energy deposit occurred. We have designed, constructed and put into operation a micro-chip (fabricated with CMOS technology) which greatly simplifies acquiring these data from large detector arrays. However, our experiments also require detectors which provide more than just energy and time information. Some of these detector systems require particle identification as well as total pulse-height (energy) and time information. The particle identification (for example, proton or alpha particle) information is encoded in the time dependence of the pulse shape from the detector elements. This proposal will create an integrated circuit, complementing our existing one, which will capable of doing the pulse-shape discrimination (PSD) required for particle type identification. A pulse-shape capable CMOS chip has never been made; however, the additional engineering effort (building on our previous chip) required to design such a chip is modest and within the scope of a two year grant. Within the two years of this grant we will: (1) design the integrated circuit, (2) build a prototype, (3) incorporate it into a working system and use it in our next experiment, (4) make a "production chip", and (5) distribute test stations to other interested groups. In doing the above, we will add a powerful new capability to the CMOS ASIC "tool box" for radiation detection instrumentation and thus make large detectors arrays with important information in the pulse shape more cost effective. We will also train several graduate and undergraduate students in mixed-signal, CMOS design.