Prog Med Phys.  2022 Mar;33(1):1-10. 10.14316/pmp.2022.33.1.1.

Effective Volume of the Korea Research Institute of Standards and Science Free Air Chamber L1 for Low-Energy X-Ray Measurement

• Yi CY
• Kim YH
• Jeong DY

• KMID: 2528099
• DOI: http://doi.org/10.14316/pmp.2022.33.1.1

Abstract

Purpose
To evaluate the effective volume of the Korea Research Institute of Standards and Science free air chamber (KRISS FAC) L1 used for the primary standard device of the low-energy X-ray air kerma.
Methods
The mechanical dimensions were measured using a 3-dimensional coordinate mea suring machine (3-d CMM, Model UMM 500, Carl Zeiss). The diameter of the diaphragm was mea sured by a ring gauge calibrator (Model KRISS-DM1, KRISS). The elongation of the collector length due to electric field distortion was determined from the capacitance measurement of the KRISS FAC considering the result of the finite element method (FEM) analysis using the code QuickField v6.4.
Results
The measured length of the collector was 15.8003±0.0014 mm with a 68% confidence level (k=1). The aperture diameter of the diaphragm was 10.0021±0.0002 mm (k=1). The mechanical measurement volume of the KRISS FAC L1 was 1.2415±0.0006 cm ³ (k=1). The elongated length of the collector due to the electric field distortion was 0.170±0.021 mm. Considering the elongated length, the effective measurement volume of the KRISS FAC L1 was 1.2548±0.0019 cm³ (k=1).
Conclusions
The effective volume of the KRISS FAC L1 was determined from the mechanically measured value by adding the elongated volume due to the electric field distortion in the FAC. The effective volume will replace the existing mechanically determined volume in establishing and maintaining the primary standard of the low-energy X-ray.

Keyword

Primary standard; Air kerma; Low-energy X-ray; Free air chamber; Effective volume