Institute of Isotopes Hungarian Academy of Sciences Nuclear electronics for NCC measurements and training J. Bagi, J. Huszti, K. Szirmai Department of Radiation Safety

Institute of Isotopes Hungarian Academy of Sciences IAEA, 19 th February 2010NCC measurements & training 2 Contents IKI list mode equipment  Neutron coincidence counting  IKI instruments and software  Comparison with JSR-14 Virtual source  Concept  Applications  Educational use

Institute of Isotopes Hungarian Academy of Sciences IAEA, 19 th February 2010NCC measurements & training 3 Neutron coincidence counting Basic assumption: Spontaneous fission rate is proportional to plutonium mass  Spontaneous fission produces multiple neutrons per event  (α,n) processes are more frequent  Fission neutrons are not detected coincidently but they are time correlated Rossi-alpha distribution  Event probability after a trigger  Time correlated events are in the near field  Far field events are not correlated with trigger

Institute of Isotopes Hungarian Academy of Sciences IAEA, 19 th February 2010NCC measurements & training 4 Multiplicity counting Multiplicity distribution  Probability of event numbers in a time interval  Building event number distribution in a near and far gate  Difference of near and far gate describes coincident neutrons Point model  Uses first three multiplicity moments  Solution for effective plutonium mass, neutron multiplication factor and (α,n) contribution

Institute of Isotopes Hungarian Academy of Sciences IAEA, 19 th February 2010NCC measurements & training 5 IKI list mode equipment Virtual instrument  Hardware box connected to a PC  All controls and display are on the PC monitor Instrument family  Based on the same hardware platform: uniform look  Control and data transfer is made via USB line  Hardware identifies itself  Handles impulse rates up to 3∙10 6 cps List mode  Saving follow-up times  Evaluating with different parameters

Institute of Isotopes Hungarian Academy of Sciences IAEA, 19 th February 2010NCC measurements & training 6 IKI instruments Single channel list mode hardware  High voltage option Virtual source Multichannel list mode hardware  Simple model  Model with channel number handling

Institute of Isotopes Hungarian Academy of Sciences IAEA, 19 th February 2010NCC measurements & training 7 Multichannel device  Detectors contain several amplifiers  Amplifier outputs are merged for data acquisition  Deadtime loss due to merging is growing with count rate  Correction may be greater than measured value  Multichannel operation reduces deadtime correction considerably at high count rates

Institute of Isotopes Hungarian Academy of Sciences IAEA, 19 th February 2010NCC measurements & training 8 Channel information handling  Saves channel number with each follow-up value  Channel information handling extends PTR by several new features  Increased reliability by checking individual channels  Coincidence rates and Rossi-alpha distribution for individual channels  Data of defect channel can be subtracted after acquisition  By grouping of channels ring ratios can be calculated

Institute of Isotopes Hungarian Academy of Sciences IAEA, 19 th February 2010NCC measurements & training 9 Data acquisition software Handles single channel and multichannel units Displays channel and ring rates Repeated measurements Graph expandable and collapsible even while data acquisition Displaying previously recorded data files Channel operations on list mode files

Institute of Isotopes Hungarian Academy of Sciences IAEA, 19 th February 2010NCC measurements & training 10 Coincidence rate calculation Very fast processing Predelay, gate width and long delay can be set The same data set can be evaluated with different parameters Program performed well at ESARDA NDA Benchmark test

Institute of Isotopes Hungarian Academy of Sciences IAEA, 19 th February 2010NCC measurements & training 11 Rossi-α distribution Detection probability after a trigger event in function of time Random events have a uniform distribution whereas fission neutrons are time correlated Dieaway calculation by fitting

Institute of Isotopes Hungarian Academy of Sciences IAEA, 19 th February 2010NCC measurements & training 12 Comparison with JSR-14 PTR-02 JSR-14 Copy JCC- 31 JSR-14 JCC- 31 PTR-16  For multichannel measurements preamplifier outputs of detector were used  JCC-31 has only six preamplifiers  Single channel version in parallel with JSR-14  Copy output of PTR-02 used

Institute of Isotopes Hungarian Academy of Sciences IAEA, 19 th February 2010NCC measurements & training 13 Comparison results  Good agreement with JSR-14 results  Data without deadtime correction  At high count rate multichannel version compensates for impulse loss resulting from merging of preamplifier signals

Institute of Isotopes Hungarian Academy of Sciences IAEA, 19 th February 2010NCC measurements & training 14 Virtual source Computer with impulse train library Virtual source Data acquisition unit  Replaces real source and detector  Can feed any standard data acquisition unit e.g. JSR-14, AMSR, PTR  Replays list mode data and software-generated artificial pulse trains Virtual source is a tool for replaying impulse trains recorded with a list mode device. It opens new possibilities for NCC  Extendable impulse train library

Institute of Isotopes Hungarian Academy of Sciences IAEA, 19 th February 2010NCC measurements & training 15 Replacing real source and detector With a virtual source neither a source nor a detector nor paperwork is needed for neutron coincidence training.  The virtual source system can be transported like a laptop and no paperwork is needed  Great freedom in establishing training sites because some training can be performed without any real sources  High efficiency detectors are difficult to move because of their large mass  Transporting radioactive sources especially nuclear ones involves a lot of administration

Institute of Isotopes Hungarian Academy of Sciences IAEA, 19 th February 2010NCC measurements & training 16 Virtual source applications Service generator  Signal generator and virtual neutron detector in one small unit  No real sources are needed for instrument testing  The same random pulse train can be reproduced many times Training and Educational Tool for NCC  Demonstrating basic features of coincidence spectra by artificially generated impulse trains  Easy transport gives more freedom in selecting and preparing training sites  Virtual source library gives the possibility of investigating sources that trainees would not have access to or not present at the training site  No radiation hazard

Institute of Isotopes Hungarian Academy of Sciences IAEA, 19 th February 2010NCC measurements & training 17 Classroom use of virtual source  Four identical output channels  Teams connected in star topology are independent of each other  Additional teams can be lined up through the copy output of PTR-02

Institute of Isotopes Hungarian Academy of Sciences IAEA, 19 th February 2010NCC measurements & training 18 Exercises with virtual source Demonstrating the basics of neutron coincidence counting  Three-stage exercise plan with software-generated periodic, burst and random impulse trains  Several simple tasks at each stage Analyzing real spectra  Introduction to most frequent sources  Application of basic knowledge to real measurements Determining the type of unknown source  Application of D/S-method of IKI

Institute of Isotopes Hungarian Academy of Sciences IAEA, 19 th February 2010NCC measurements & training 19 Distribution basics Periodic Burst Random Follow-upMultiplicityRossi-alpha Every stage demonstrates some basic characteristics of the distributions  Periodic: multiplicity depends on gate width, building-up of Rossi- alpha  Burst: interpreting follow-up distribution, predelay  Random: variants of multiplicity spectrum

Institute of Isotopes Hungarian Academy of Sciences IAEA, 19 th February 2010NCC measurements & training 20 Analyzing real spectra  Getting familiar with basic source types  Basic impulse train library  Impulse trains measured in other laboratories can be added to library PuBeCf-252 Follow-up Multiplicity Rossi- α

Institute of Isotopes Hungarian Academy of Sciences IAEA, 19 th February 2010NCC measurements & training 21 Identifying unknown source Reference sources  Data acquisition  Calculation of coincidence rates  Setting up classification diagram Unknown sample  Data acquisition  Calculation of coincidence rates  Determining source kind from D/S value Application of D/S method developed in IKI

Institute of Isotopes Hungarian Academy of Sciences IAEA, 19 th February 2010NCC measurements & training 22 Exercises – completion Virtual source reduces training costs  Basic training can be held in a simple classroom  Training in the laboratory is shorter  Trainees are better prepared when measuring with real sources Real source handling is required  No sample handling exercise  Using of detector

Institute of Isotopes Hungarian Academy of Sciences IAEA, 19 th February 2010NCC measurements & training 23 Conclusion List mode measuring is emphasized in IAEA R&D objectives  Laboratory prototype available  Multichannel prototype extends measuring capability into million cps range  Virtual source is a spin-off product of list mode Application of virtual source in training  Cost reducing  No radiation hazard

Institute of Isotopes Hungarian Academy of Sciences IAEA, 19 th February 2010NCC measurements & training 24 Thank you for your attention!