NDS - Laboratory for Dosimetry Standards

Jožef Stefan Institute,
Jamova 39,
SI-1000 Ljubljana,

T: +38614773651, +38614773416


Leader: Matjaž MiheličCoworkers: Boštjan Črnič


The main activity of the NDS laboratory is the maintenance of the secondary standard in the field of dosimetric quantities (kerma in air) and in the field of quantities in radiation protection (equivalent dose, surface emission).

The traceability of the standard for kerma and equivalent dose is ensured through secondary ionization chambers (Fig. 1) and for surface emission through large area sources (Fig. 2).


Fig. 1 Secondary ionization chambers (top to bottom):

  • LS-01: for traceability of Cs-137, Co-60, Am-241 HASS sources and  X-ray narrow series spectra (N)
  • TW 34060: for traceability of RQR and RQA diagnostic spectra
  • RC 06 M: for traceability of    RQR-M and RQA-M diagnostic spectra



Fig. 2 Large area sources with an active surface of 10 x 10 cm² for calibration of surface contamination monitors


Ionization chambers and large area sources are periodically sent for calibration to primary laboratories.

In the NDS laboratory, calibration and irradiation of dose meters, dose rate meters (γ and X-ray) and calibration of contamination monitors (surface emissions of α and β particles) ensure the dissemination of metrological traceability at national and international levels.

We calibrate and irradiate all types of radiation protection meters:

  • Ionization chambers
  • Portable environmental dose/dose rate meters (e.g. Fig. 3)
  • Electronic personal dose/dose rate meters (e.g. Fig. 3)
  • Passive personal equivalent dose meters (TLD, OSL dosimeters)
  • Surface contamination monitors


Fig. 3 Environmental equivalent dose rate meter (left) and personal electronic dosimeter (right).


For calibrations of γ radiation and X-rays meters the following sources are used:

  • Am-241, Cs-137, Co-60 in X-ray narrow series (N-30 to N-150)

according to the standards: ISO 4037-1:2019, -2:2019, -3:2019, -4:2019, X and gamma reference radiations for calibrating dosemeters and doserate meters and for determining their response as a function of photon energy

Diagnostic series:

  • RQR,
  • RQA (RQR/RQA-3 , RQR/RQA-5, RQR/RQA-7, RQR/RQA-9),

and diagnostic series:

  • RQR-M,

according to the standard: CEI/IEC 61267:2005, Medical diagnostic equipment – Radiation conditions for use in determination of characteristics.


For calibration of surface contamination monitors the following large area sources are used:

  • α radiation: Am-241, U-238
  • β radiation: Cl-36, Sr-90, Cs-137, Tc-99

according to the NPL GPG No. 14 infinite planar source method.


Our calibration and measurement capabilities (CMCs) are published in the Key Comparison DataBase (KCDB) at BIPM. All information is publicly available on the BIPM website.

Calibration / Irradiation capabilities

  • Gamma ray high activity sealed sources (HASS): Co-60, Cs-137, Am-241
  • X-ray 1: 10-160 keV (ISO 4037 narrow spectra N, IEC 61267 diagnostic spectra: RQR, RQA)
  • X-ray 2: 2- 60 keV (IEC 61267 mammographic spectra: RQR-M, RQA-M)
  • α radiation: Am-241, U-238
  • β radiation: Cl-36, Sr-90, Cs-137, Tc-99

Dose rate range: 0 - 0.1 Gy/min

Dose range: 0 - 1 Gy

Gamma / X-ray energy range: 10 - 1250 keV

Possible duration of exposure: 100 h

Dose rate modulation options: 10⁶

Source to irradiated object distance: up to 7 m

Main use of the facility: calibration, irradiation, testing

Dosimetric quantities used:

  • Air kerma [Gy]
  • Ambient dose equivalent H* (10), personal dose equivalent Hp(10) and Hp(0,07) [Sv]
  • Surface emission rate: α, β [s⁻¹]



  • Maintaining the traceability of a reference standard - Ionizing radiation
  • Calibrations



  • Calibrations

The Laboratory for Dosimetry Standards (NDS) was established in 1992 at Section F-2 at the Jožef Stefan Institute in order to offer Slovenia quality metrological support for ionizing radiation measurements, primarily to radiation protection of people and environment.

NDS is the only laboratory in Slovenia to offer measurement traceability in the field of ionizing radiation quantities. Since 2003 it has been accredited by Slovenian Accreditation according to the ISO / IEC 17025 standard. In 2009, NDS was named the National Standard Holder (NNE) in the field of ionizing radiation by the Metrology Institute of the Republic of Slovenia (MIRS). The Laboratory, as NNE, is included in the Slovenian National Metrology System, managed by MIRS.

We are actively engaged in the work of Technical Committee for Ionizing Radiation (TC-IR) at the international organisation EURAMET.

In 2015, the NDS was commissioned modern metrology equipment - a calibration system for mammography X-ray spectra as part of the project "Metrology System Infrastructure - Ionizing Radiation". The metrology equipment was purchased with the help of the European Regional Development Fund by the Metrology Institute of the Republic of Slovenia.