Improvement of the performance of germanium detectors using pulse shape analysis for industrial and environmental applications

Lead Research Organisation: University of Liverpool
Department Name: Physics

Abstract

A commonly used method of identifying and quantifying radioactive isotopes in safety, security and environmental applications is to measure the gamma-ray spectrum using a high resolution germanium detector. This allows an individual gamma-ray energy to be determined exactly and then the isotope uniquely identified and quantified. A limitation of germanium detectors is their poor peak to background response. As the most probable interaction of the gamma rays of interest with the detector material is Compton scattering there is a significant Compton continuum in the spectra at energies below the incident gamma-ray energy. This can result in the Compton background from high activity isotopes masking the photopeaks from lower activity isotopes. Reduction of Compton background is one aim of this work. The demand from many users is to have very efficient detector systems to improve their sensitivity and reduce their counting times. Once the efficiency is greater than a few percent coincidence summing becomes a problem. This occurs when two or more gamma rays from the same decay event are detected simultaneously. This can lead to substantive corrections being necessary. These corrections are often very difficult to apply when the isotope decays with many gamma rays.The identification of coincidence summing events is a second aim of this work. Germanium detectors used for industry applications have to be simple, usually single crystal devices, to allow their use in a wide range of establishments. Those available on the market today, in general, have poor timing characteristics and this timing information is not easily available to the user. The third aim of this work is to develop an algorithm to define accurately the time of the interaction in the detector and to measure how the charge is collected immediately after this. This will be done by looking at signals derived from both electron and hole collection. This should lead to an improved spectral response as events will be better characterised. The final aim of this work is to investigate the feasibility of using a single germanium crystal with a relatively simple electrode structure to produce spectroscopic gamma-ray images. This work will used electric field simulations to investigate the possibilities.

Canberra is a world-leading supplier of instrumentation for the nuclear industry. The annual market size for standard High Purity Germanium detectors worldwide is around £13M, with Canberra's share at approximately 50% (the market leader in this field). The project aims to optimise Canberra's unique detector portfolio for the digital era, in order to realise real world improvement in the UK's installed detector base. Canberra expects the results of this project to grow sales of these detectors by 15%, and Canberra's market share by 7%. The new detectors and instruments that arise from the project will directly influence Canberra's UK operation where they are a major supplier of instruments and R&D to key UK laboratories in the nuclear power and decommissioning sectors, the environmental and public health sectors and those working on security and the UK counter test ban treaty work.

Publications

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Colosimo S (2015) Characterisation of two AGATA asymmetric high purity germanium capsules in Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

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Harkness-Brennan L (2014) An experimental characterisation of a Broad Energy Germanium detector in Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

 
Description Significant progress has been made in achieving improvements in the spectrum quality and time resolution of the Broad Energy germanium detector systems. The Peak to Total of the BEGe detector has been significantly improved by the application of Digital signal processing techniques.
Exploitation Route The current achievements are being implemented in commercial products at this time
Sectors Energy

 
Description The output of the research is being integrated into commercial products. The advancement will lead to a significant advancement in the performance of germanium detector systems.
First Year Of Impact 2016
Sector Energy
Impact Types Societal,Economic

 
Description IPS 1 
Organisation Mirion Technologies Inc
Country United States 
Sector Private 
PI Contribution Expertise in Gamma-ray imaging systems
Collaborator Contribution Mirion Technologies have supported the development of Gamma-ray Imaging systems for the Nuclear sector. They have sponsored PhD and MSc students and support research grant applications.
Impact New algorithms for extracting signals from germanium detectors. New optimised designs of deployable detector systems.
Start Year 2014
 
Title Signal filtering algorithm 
Description Software to filter the gamma-ray energy deposition based on the waveform to improve measurable peak to total and maintain efficiency. 
Type Of Technology Software 
Year Produced 2017 
Impact The algorithm will be included in the next release of digitiser hardware for germanium detector readout. This will offer significant performance advantages to already installed detector systems (as well as new products). The key impact will be on the Nuclear Energy and Decommissioning sector. 
 
Description Advances in semiconductor sensors, Gamma-ray imaging system, U of York Departmental Seminar 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Undergraduate students
Results and Impact Departmental seminar series, University of York
Year(s) Of Engagement Activity 2014
 
Description From AGATA to Gamma-ray imaging: Status and perspectives, Uof Notre Dame 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact University of Notre Dame conference
Year(s) Of Engagement Activity 2014
 
Description Invited talk: Gamma-ray imaging spectroscopy, CARM conference, NPL, London 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Invited talk at CARM conference (radiation metrology)
Year(s) Of Engagement Activity 2015
 
Description NNL Technical Seminar Series 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact National Nuclear Laboratory Technical Seminar series. Presenting projects that define the technology roadmap going forward. Raised profile of STFC technology opportunities within the nuclear sector.
Year(s) Of Engagement Activity 2017
 
Description Physics INNOVATE 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact Physics INNOVATE was run as part of the international festival of business. Held in Liverpool at the Convention Centre (2016) and the Town Hall (2015). The event showcased the key UoL and STFC technologies to a broad range of industry. A number of new projects have commenced following these events.
Year(s) Of Engagement Activity 2015,2016