1. LS User’s Forum 2001 Developments in LSC Andy Pearce CIRM Date: 5th September 2001

3.  Intro - LSC at NPL  LSC2001  ICRM2001  Summary

4. Liquid Scintillation at NPL  4  LS coincidence counting – Absolute standardisation using LSC – High(ish) activities –  -  or  -  emitting nuclides – Extension to other nuclides – tracer technique  CIEMAT/NIST efficiency tracing – Secondary standardisation using LSC – Wide range of activities – Primarily for pure  emitting nuclides – Extension to most other nuclides – courtesy of Günter

5. Liquid Scintillation at NPL (cont’d)  Triple-Double Coincidence Rate (TDCR) Method – Absolute Standardisation using LSC – Custom built counters – three photomultipliers – Pure  and pure EC nuclides – Not coincidence counting!  Other Techniques – “Standard” techniques as familiar to many – Straightforward secondary counting – Dilution factors – Health physics

6. LSC2001 – Advances in Liquid Scintillation Spectrometry

7. LSC2001- Advances in Liquid Scintillation Spectrometry “...aims at providing a forum for radioanalysts to discuss their most recent findings and future work”  Karlsruhe, Germany 7-11 May 2001  Participants from environmental & life sciences  NIST, PTB, LNHB and NPL

8. LSC2001- Topics Discussed  Natural Radioactivity  Applications in Bioscience & Medicine  Tritium and Radiocarbon  Low Level Counting  Nuclear Sciences & Environmental Survey

9. LSC2001- Topics Discussed (cont’d)  Instrumentation & Data Handling  Sample Preparation  Chromatographic Methods  Cocktails  Other Techniques

10. LSC2001- Scientific Interest  Large amount of interest in Radon and Radium analysis  Some “nuts and bolts” work – particularly by CEA  Alpha-beta pulse shape discrimination  Spectral deconvolution  Scintillant cocktails – nothing new!

11. LSC2001 – Radium and Radon A large amount of Chemistry!!!

12. LSC2001- Nuts and Bolts  Three papers from CEA on underlying principles in LSC  “Understanding the peak asymmetry in  -LS with  /  discrimination”  “Energy Transfer and Fluorescence Mechanism in  -LS – Applications to Scintillation Cocktail Composition”  Wall Effect in LSC

13. LSC2001- Alpha-Beta PSD  A rather popular technique  Some concern (informally raised) that this is often used incorrectly  Commercial systems require careful calibration to give reliable results

14. LSC2001- Spectral Deconvolution  Another increasingly popular method  Again, some users appear over-optimistic of what can be achieved with this technique  Uncertainty handling and confidence levels seem generally optimistic (personal opinion!)

15. LSC2001- Scintillant Cocktails  Some sales pitches – but nothing much new?  Interesting “one stage” scintillant with a large Stokes’ Shift (details unavailable)  “Seasonal Variation” of commercial cocktails  Packard LSA Cocktail Guide

16. Slippery Packard!  1 Shot of rum  1 Orange  Take a bite out of the orange  Down the rum  Eat the rest of the orange

17. ICRM2001- International Conference on Radionuclide Metrology and it’s Applications “... to provide an opportunity for the exchange of information on techniques and applications of radionuclide metrology, and to encourage international co-operation in this field”  Braunschweig, Germany 14-18 May 2001  Representation from NMI’s such as NIST, PTB and NPL  Includes report from ICRM-LSC Working Group

18. ICRM2001- Topics Discussed  Stability problems with alkaline matrices  Ionisation quench  Wall effect in LSC  Developments in CIEMAT/NIST from PTB  Web Page

19. ICRM2001 – Alkaline Matrices  A particular problem for NMI’s – Some nuclides not soluble in acids – Example 188 W/ 188 Re  Also a problem for user community? – Matrices often more complex – Longer measurement times

20. ICRM2001- Ionisation Quench  Ionisation quench parameter is used in both CIEMAT/NIST and TDCR techniques  Not significant at high energies – but may be dominant at low energies  Some doubts over best formula and constants to use  Limits precision of CIEMAT/NIST and TDCR

21. ICRM2001- Wall Effect  LNHB (part of CEA) have investigated wall effect  Used PENELOPE Monte Carlo code  Coupled modelling with experimental observations  Demonstrated that the wall effect is negligible for high- energy beta emitters

22. ICRM2001- Developments in CIEMAT/NIST  PTB have developed new CIEMAT/NIST code  Extension to standardisation of wider range of nuclides (almost any in fact)  Investigated the best achievable uncertainties  Demonstrated that uncertainties for pure EC nuclides are limited by ionisation quench

23. ICRM2001- Web Page www-dta.cea.fr/DAMRI/FR/Pages/radioactivité/scintillation/icrm1.htm  ICRM Working Group web page, containing information on standardisation techniques:  You don’t need to be able to speak French, however...  Your browser does!

24. Summary – Points  Pulse Shape Discrimination – How well does it really work? – Is it applied properly?  Spectral Deconvolution – Does anybody rely on it? – How much confidence in results?

25. Summary – Points (cont’d)  Scintillant Cocktails – Variability from one batch to the next – A problem for us – what about the user?  Alkaline Matrices – How to obtain stable solutions – What to use to produce quench curves