The art of pulse shaping in solid-state detectors

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Date:	January 26, 2012 – 10:00 am
Speaker:	Matjaz Vencelj
Abstract:	Spectroscopic pulse shaping is a way of maximizing the signal-to-noise ratio in nuclear particle detectors. This is particularly crucial in high purity germanium detectors, made to measure gamma-rays with the highest possible energy resolution. Given their cost and the hassle of cryogenic operation, all for superior resolution, signal analysis must be taken seriously. In terms of resolution alone and when detection events are rare, classical approaches to shaping are sufficient. High count rates however, invented specifically to collect good statistics during progressively shorter PhD projects, bring in systematic distortions of the measured gamma-ray energy, called pile-up artifacts, unless one throws away a great deal of experimental information. Starting with the mantra of distilling all of the available information from the signal, we propose an adaptive time-domain filter, motivate it and define it mathematically, attempt to explain it in terms of neat pictures, and report on rather promising first experimental testing, reaching well over 1Mcps throughput rates in a large HPGe detector. Lastly, real-time considerations of implementing the filter in programmable hardware are discussed. About the speaker Dr. Matjaz Vencelj was born in 1975 in Slovenia, the tiny speck of subalpine land which the locals are mysteriously proud of. He obtained a college degree in piano in 1993, kyu 4 in karate in 1995, and a PhD in experimental nuclear physics from the University of Ljubljana in 2006. During 2006 and 2007, he held a research position between the Hi-Light Optoelectronics company and the Kernfysisch Versneller Instituut in Groningen. Since then, he works at the Jozef Stefan Institute in Ljubljana. Since his Dutch period, his passion and specialty are the design of ambitious nuclear detectors and complicated algebraic read-out schemes for detector signals, particularly at very high count rates. This brings in a natural overlap with the instrumentation for monitoring of medical radiotherapies. He currently lives with his wife and two small children in a fireplace-heated home at the outskirts of Ljubljana, property including three apple-trees and a ’74 Piaggio moped.

Date:

January 26, 2012 – 10:00 am

Speaker:

Matjaz Vencelj

Abstract:

Spectroscopic pulse shaping is a way of maximizing the signal-to-noise ratio in nuclear particle detectors. This is particularly crucial in high purity germanium detectors, made to measure gamma-rays with the highest possible energy resolution. Given their cost and the hassle of cryogenic operation, all for superior resolution, signal analysis must be taken seriously.

In terms of resolution alone and when detection events are rare, classical approaches to shaping are sufficient. High count rates however, invented specifically to collect good statistics during progressively shorter PhD projects, bring in systematic distortions of the measured gamma-ray energy, called pile-up artifacts, unless one throws away a great deal of experimental information.

Starting with the mantra of distilling all of the available information from the signal, we propose an adaptive time-domain filter, motivate it and define it mathematically, attempt to explain it in terms of neat pictures, and report on rather promising first experimental testing, reaching well over 1Mcps throughput rates in a large HPGe detector.

Lastly, real-time considerations of implementing the filter in programmable hardware are discussed.

About the speaker

Dr. Matjaz Vencelj was born in 1975 in Slovenia, the tiny speck of subalpine land which the locals are mysteriously proud of. He obtained a college degree in piano in 1993, kyu 4 in karate in 1995, and a PhD in experimental nuclear physics from the University of Ljubljana in 2006.

During 2006 and 2007, he held a research position between the Hi-Light Optoelectronics company and the Kernfysisch Versneller Instituut in Groningen. Since then, he works at the Jozef Stefan Institute in Ljubljana.

Since his Dutch period, his passion and specialty are the design of ambitious nuclear detectors and complicated algebraic read-out schemes for detector signals, particularly at very high count rates. This brings in a natural overlap with the instrumentation for monitoring of medical radiotherapies.

He currently lives with his wife and two small children in a fireplace-heated home at the outskirts of Ljubljana, property including three apple-trees and a ’74 Piaggio moped.

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