Radiation Physics and Engineering
A peer-reviewed journal published by K. N. Toosi University of Technology

Absolute standardization of carbon-14 by the CIEMAT/NIST method with empirical determination of the Birks parameter

Document Type : Research Article

Authors

Mohammad Ali Mohammadi 1
Omidreza Kakuee 2
M. Zahedi Far 1
Ali Biganeh 2
Masoomeh Sharbatdaran 2

1 Department of Nuclear Physics, Faculty of Physics, University of Kashan, Kashan, Iran

2 Physics and Accelerators Research School, Nuclear Science and Technology Research Institute, P.O. Box: 14395-836, Tehran, Iran

https://doi.org/10.22034/rpe.2026.573537.1338
Abstract
This study presents the implementation and validation of the CIEMAT/NIST efficiency tracing method for the absolute standardization of Carbon-14 using an ultra-low-level Quantulus 1220 liquid scintillation counter, toluene-based cocktails, and the EFFY-9 code. Due to the absence of a dedicated profile for classical toluene cocktails in the software library, Ultima Gold was used as a substitute. To achieve this, a universal curve was constructed using a series of tritiated standards as a tracer, correlating the instrumental quench index with the model’s free parameter. Subsequently, the activity of two certified Carbon-14 standards was computed across a range of Birks parameter (kB) values from 0.004 to 0.014 cm.MeV-1. The results exhibited excellent agreement with certified values, with relative deviations consistently remaining below 2.1%. Detailed analysis indicated that the minimum bias corresponds to kB=0.004 cm.MeV-1. This finding confirms that, in this specific configuration, kB serves as an effective parameter, compensating for the residual mismatch between the actual properties of toluene and the surrogate computational profile. This research emphasizes the necessity of experimentally determining the Birks parameter for each specific laboratory setup to ensure maximum accuracy.

Highlights

  • CIEMAT/NIST method validated for absolute Carbon-14 standardization in LSC.
  • Universal calibration curve established using tritium for Carbon-14 efficiency.
  • Optimized Birks parameter (kB) achieved a deviation below 2.1% from certified values.
  • Method eliminates need for nuclide-specific calibration standards in LSC.
  • First national-level application of CIEMAT/NIST for Carbon-14 in toluene cocktails.

Keywords

Liquid Scintillation Counting
CIEMAT/NIST Method
Birks Parameter
Efficiency Tracing

Copyright
RPE is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License (CC BY-NC 4.0).

Conflict of Interest
The authors declare no potential conflict of interest regarding the publication of this work‎.

Funding
‎The authors declare that no funds‎, ‎grants‎, ‎or other financial support were received during the preparation of this manuscript‎.

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Radiation Physics and Engineering
Volume 7, Issue 3
Summer 2026
Pages 45-52

  • Receive Date 02 February 2026
  • Revise Date 12 May 2026
  • Accept Date 23 June 2026

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