1 / 10

LS User’s Forum 2001

LS User’s Forum 2001. CIEMAT/NIST – what is it?. Andy Pearce CIRM. Date: 5 th September 2001. What is CN Basic Idea Free Parameter Model Fermi Theory Summary. What is CIEMAT/NIST. Standardisation technique developed by CIEMAT and NIST (hence the name) based on LSC

cloris
Download Presentation

LS User’s Forum 2001

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. LS User’s Forum 2001 CIEMAT/NIST – what is it? Andy PearceCIRM Date: 5th September 2001

  2. What is CN • Basic Idea • Free Parameter Model • Fermi Theory • Summary

  3. What is CIEMAT/NIST • Standardisation technique developed by CIEMAT and NIST (hence the name) based on LSC • Allows standardisation without specialised equipment • Initially for pure beta emitting nuclides • Later extended to EC and EC-gamma nuclides

  4. The Basics • A Poisson model is used to calculate the detection efficiency for a nuclide as a function of a “free parameter” – related to amount of chemical quench in the sample • Relationship between free parameter and external standard quench factor determined using tritium • Combination of the two used to generate a quench curve for the nuclide of interest

  5. Free Parameter Model • For a mono energetic beta particle the efficiency is given by • E is the particle energy • Q(E) is the ionisation quench function • M is the “free parameter”

  6. Fermi Theory • The energy distribution of beta particles is given by: • W is the beta energy (here in natural units) • W0 is the end point energy • F0L0 is the relativistic Fermi coulomb correction • S is the shape factor correction • C is a collection of other correction terms

  7. Bringing it Together • Efficiencies at a range of free parameters are calculated for tritium and matched to an experimental tritium quench curve, to give a free parameter vs. quench curve • Free parameter vs. efficiency is calculated for the nuclide of interest • From the two curves, efficiency can be calculated for the sample nuclide

  8. Bringing it Together

  9. Summary • The CIEMAT/NIST method is a useful means of standardising pure beta emitters • Mathematically very complex, but software codes can be used to “black box” without knowledge of the underlying algorithms • Allows accurate measurement of “new” nuclides with commercial LS counters

More Related