Hungarian Academy of Sciences Institute of Isotopes Nuclear

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

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

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

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

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

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

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

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

• 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 Hungarian Academy of Sciences Institute of Isotopes Data acquisition software NCC measurements & training 9 IAEA, 19 th February 2010

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Hungarian Academy of Sciences Institute of Isotopes Thank you for your attention! www. iki. kfki. hu/radsec/research huszti@iki. kfki. hu NCC measurements & training 24 IAEA, 19 th February 2010