keV Energy Range Research Articles

Nonthermal X-Rays from Pulsation-driven Shocks in Cepheids

Rapid X-ray phase-dependent flux enhancement in the archetype classical Cepheid star δ Cep was observed by XMM-Newton and Chandra. We jointly analyze thermal and nonthermal components of the time-resolved X-ray spectra prior to, during, and after the enhancement. A comparison of the timescales of shock particle acceleration and energy losses is consistent with the scenario of a pulsation-driven shock wave traveling into the stellar corona and accelerating electrons to ∼GeV energies, and with Inverse Compton (IC) emission from the UV stellar background leading to the observed X-ray enhancement. The index of the nonthermal IC photon spectrum, assumed to be a simple power law in the [1–8] keV energy range, radially integrated within the shell [3–10] stellar radii, is consistent with an enhanced X-ray spectrum powered by shock-accelerated electrons. An unlikely ∼100-fold amplification via turbulent dynamo of the magnetic field at the shock propagating through density inhomogeneities in the stellar corona is required for the synchrotron emission to dominate over the IC; the lack of time correlation between radio synchrotron and stellar pulsation contributes to make synchrotron as an unlikely emission mechanism for the flux enhancement. Although current observations cannot rule out a high-flux two-temperature thermal spectrum with a negligible nonthermal component, this event might confirm for the first time the association of Cepheids pulsation with shock-accelerated GeV electrons.

Polarization Properties of the Weakly Magnetized Neutron Star X-Ray Binary GS 1826–238 in the High Soft State

The launch of the Imaging X-ray Polarimetry Explorer (IXPE) on 2021 December 9 has opened a new window in X-ray astronomy. We report here the results of the first IXPE observation of a weakly magnetized neutron star, GS 1826−238, performed on 2022 March 29–31 when the source was in a high soft state. An upper limit (99.73% confidence level) of 1.3% for the linear polarization degree is obtained over the IXPE 2–8 keV energy range. Coordinated INTEGRAL and NICER observations were carried out simultaneously with IXPE. The spectral parameters obtained from the fits to the broadband spectrum were used as inputs for Monte Carlo simulations considering different possible geometries of the X-ray emitting region. Comparing the IXPE upper limit with these simulations, we can put constraints on the geometry and inclination angle of GS 1826–238.

A multifrequency characterization of the extragalactic hard X-ray sky

Context. Nowadays, we know that the origin of the cosmic X-ray background (CXB) is mainly due to the integrated emission of active galactic nuclei. Therefore, in order to obtain a precise estimate of the contribution of different source classes to the CXB, it is crucial to achieve full characterization of the hard-X ray sky. Aims. We present a multifrequency analysis of all sources listed in the third release of the Palermo Swift-BAT hard X-ray catalog (3PBC) with the goal of (i) identifying and classifying the largest number of sources adopting multifrequency criteria, with particular emphasis on extragalactic populations and (ii) extracting sources belonging to the class of Seyfert galaxies to present here the release of the second version of the Turin-SyCAT. Methods. We outline a classification scheme based on radio, infrared (IR), and optical criteria that allows us to distinguish between unidentified and unclassified hard X-ray sources, as well as to classify those sources belonging to the Galactic and the extragalactic populations. Results. Our revised version of the 3PBC lists 1176 classified, 820 extragalactic, and 356 Galactic sources, as well as 199 unclassified and 218 unidentified sources. According to our analysis, the hard X-ray sky is mainly populated by Seyfert galaxies and blazars. For the blazar population, we report trends between the hard X-ray and the gamma-ray emissions based on the fact that a large fraction of them also have a counterpart detected by the Fermi satellite. These trends are all in agreement with the expectations of inverse Compton models which are widely adopted to explain the blazar broadband emission. For the Seyfert galaxies, we present the second version of the Turin-SyCAT, including a total of 633 Seyfert galaxies, with 282 new sources corresponding to an increase of ~80% with respect to the previous release. Comparing the hard X-ray and the infrared emissions of Seyfert galaxies, we confirm that there is no clear difference between the flux distribution of the infrared-to-hard X-ray flux ratio of Seyfert galaxies Type 1 and Type 2. However, there is a significant trend between the mid-IR flux and hard X-ray flux, confirming previous statistical results in the literature. Conclusions. We provide two catalog tables. The first is the revised version of the 3PBC catalog based on our multifrequency analyses. The second catalog table is a release of the second version of the Turin-SyCAT catalog. Finally, we highlight that extensive soft X-ray data are already available in the form of the Swift archive which can be used to search for potential counterparts of unidentified hard X-ray sources. All these datasets will be reduced and analyzed in a forthcoming analysis to determine the precise position of low-energy counterparts in the 0.5–10 keV energy range for 3PBC sources that can be targets of future optical spectroscopic campaigns; this is necessary to obtain their precise classification.

The scientific performance of the microchannel X-ray telescope on board the SVOM mission

The Microchannel X-ray Telescope (MXT) will be the first focusing X-ray telescope based on a narrow field “Lobster-Eye” optical design to be flown on a satellite, namely the Sino-French mission SVOM. SVOM will be dedicated to the study of Gamma-Ray Bursts and more generally time-domain astrophysics. The MXT telescope is a compact (focal length $\sim $ 1.15 m) and light (< 42 kg) instrument, sensitive in the 0.2–10 keV energy range. It is composed of an optical system, based on micro-pore optics (MPOs) of 40 μ m pore size, coupled to a low-noise pnCDD X-ray detector. In this paper we describe the expected scientific performance of the MXT telescope, based on the End-to-End calibration campaign performed in fall 2021, before the integration of the SVOM payload on the satellite.

Single- and double-ionization processes of antiproton-helium and antiproton–molecular hydrogen collisions in the keV energy range

We report on an ab initio model to describe single- and double-ionization processes in antiproton collisions with atoms and molecules. Our model is based on a fully correlated close-coupling approach and a Dyson orbital analysis. Furthermore, we employ the concept of a correlation integral in order to quantify and gain insights into the effects of electronic correlation on the ionization processes. Our model is applied to the prototype antiproton-helium and antiproton--molecular hydrogen collision systems in the keV energy range.

Design and performance of the camera of the Micro-channel X-ray Telescope on-board the SVOM mission

The Microchannel X-ray Telescope (MXT) is part of the scientific payload of the SVOM Sino-French space mission to observe the early afterglow of gamma-ray bursts in the 0.2–10 keV energy range and localize them within 2 arcmin. For a total mass of 42 kg and a total power of 60 W, this instrument is composed of an optical system, a structural carbon fiber tube, a radiator, a camera and a data processing unit. The camera consists of a focal plane assembly with a detector ceramic board and thermoelectric coolers, a front-end electronics, a calibration wheel and a support structure. Spectral characterization tests of the focal plane assembly based on a 256 × 256 pixel pnCCD spectroscopic imager were performed in the laboratory, at the Metrology beamline of the SOLEIL synchrotron and at the PANTER X-ray facility. Energy resolution of 79 eV FWHM at 1.5 keV was demonstrated in the nominal flight configuration (−65 °C, real time event selection by the camera). The paper presents the design, the realization and the performance of the flight camera of MXT. It focuses on the technical challenges, the original implemented solutions and the custom-made setups for the validation tests.

Differential cross–section measurements and R-Matrix calculations for proton elastic scattering on natMg in the energy range Ep,lab = 2.70–4.25 MeV, suitable for EBS

In the current work the first coherent set of differential cross section values for the natMg(p,p0)natMg elastic scattering covering the Ep,lab = 2700–4250 keV energy range is presented for 6 backscattering detection angles (120°, 130°, 140°, 150°, 160° and 170°). R-Matrix calculations were implemented using the AZURE 2.0 code [1] in an attempt to reproduce the obtained experimental data, whilst taking into account the 24Mg(p,p1)24Mg reaction channel. Both results are suitable for EBS and other IBA applications and, furthermore, they form a basis for a future expansion of the current SigmaCalc [2] evaluation, once more experimental data become available. The measurements were performed in the 5.5 MV TN11 HV Tandem Accelerator and the high precision goniometer of N.C.S.R. ‘Demokritos’, Athens, Greece. The experimental and data analysis procedures are presented in detail, along with the process behind the implementation of the R-Matrix calculations.

Structural and photon/neutron attenuation features of PbNi/CNT nanocomposites: An experimental approach

In this work, PbNi/CNT nanocomposites were prepared by sodium borohydride method at varying metallic molar ratios for determination of their structural and nuclear radiation shielding properties. As-prepared PbNi/CNTs were characterized by using transmission electron microscopy (TEM), scanning electron microscopy energy-dispersive X-ray spectroscopy (SEM-EDX), elemental mapping, and X-ray diffraction (XRD). Average particle sizes of Pb40Ni60/CNT, Pb60Ni40/CNT, Pb80Ni20/CNT, and Pb20Ni80/CNT materials were obtained as 5.6, 3.8, 4.2, and 4.2 nm, respectively. Radiation attenuation properties of the produced nanocomposites were investigated experimentally by irradiating the samples with gamma photons in the 34–383 keV energy range. The accuracy of the experimental results was checked with outcomes calculated with EpiXS software. Mass attenuation coefficient (MAC) was found in the range of 22.924–0.108 cm2/g, 5.473–0.129 cm2/g, 3.767–0.109 cm2/g, and 4.626–0.128 cm2/g for Pb20Ni80/CNT, Pb80Ni20/CNT, Pb40Ni60/CNT, and Pb60Ni40/CNT samples, respectively. Also, other photon shielding parameters (HVL, Zeff, EABF, and EBF) were calculated to make a comprehensive evaluation. The results show that 30% by weight Pb80Ni20 doped CNT has the lowest HVL and buildup factors values and the largest MAC, Zeff values. Finally, macroscopic cross-section values (ΣR) were obtained to estimate the ability of the nanocomposite samples to reduce the energy of fast neutrons. It was revealed that the ΣR values of the samples were in the range of 0.158–0.169 cm−1 and they had higher ΣR values than conventional neutron moderators.

Characterization of the focal plane of the microchannel X-ray telescope at the metrology beamline of SOLEIL synchrotron for the space astronomy mission SVOM

The Microchannel X-Ray Telescope is one of the four instruments of the SVOM Sino-French space mission to observe the afterglow of gamma-ray bursts in the 0.2–10 keV energy range and localize them within 2 arcmin. Inside the 9 kg camera, the detection chain consists of a detector assembly equipped with a fully depleted 256 × 256 pixels pnCCD and two CAMEX front-end ASICs, and a “US-free” front-end electronics unit to control the focal plane and extract photon events. The flight spare model was installed and characterized in November 2021 at SOLEIL synchrotron on the soft X-ray branch of Metrology beamline operating from 40 eV to 1800 eV. The goals of this campaign were to measure the quantum efficiency and characterize the spectral response, i.e., the energy calibration law, the charge transfer efficiency and the energy resolution at different positions on the detector. This implied the development of a full-custom cryostat to interface with the beam line and a special tuning of the beam line to get the appropriate photon flux for single photon counting in the pixels of 75 μm size without pile-up. This paper presents the configuration, the test plan, the test results, and the modeling of the detector response. This beam line was successfully used for spectral characterizations of the MXT detector from 300 to 1800 eV with excellent spectral purity and with a photon flux 7 orders of magnitude lower than the beamline nominal output.

Optical design of micro-focus X-ray photon correlation spectroscopy beamline at Shenzhen Light Source

An optical design study of a beamline proposed for the 3 GeV synchrotron radiation facility, the Shenzhen Light Source, is described. The beamline was designed to cover an energy range from 2.0 to 20 keV with two experimental station, one for X-ray absorption spectroscopy (XAS) experiments and the other for X-ray photon correlation spectroscopy (XPCS) experiments. A 4 m planar undulator with a relatively short magnetic period (20 mm) was used as the radiation source. Horizontally and vertically focusing mirrors separately focus the source along the horizontal and vertical directions, respectively, thus enhancing the flexibility of the beamline. The focus point was employed as the secondary source, and a pair of KB mirrors were used to achieve a near-circular focus spot of about 4.5μm×4.5μm. A Si(111) DCM was selected to produce the monochromatic light that covers the 2.0–20 keV energy range. When the photon energy is lower than 10 keV, the energy resolution can be better than 1.47 × 10−4 and the total flux is larger than 1 × 1014 photons/s. The longitudinal coherence length is in a few μm range. With aperture size adjustment, the transverse coherence length at the sample position is approximately 3μm and the coherent flux is up to 1012 phs/s for the photon energy around 2.5 keV. This excellent coherence performance can be applied for the purpose of X-ray photon correlation spectroscopy related experiments.

X-ray detectors for the BabyIAXO solar axion search

BabyIAXO is a helioscope under construction to search for an emission of the axion particle from the Sun. At the same time it serves as an intermediate stage towards the International Axion Observatory (IAXO). An integral component of this experiment is a low background X-ray detector with a high efficiency in the 1–10 keV energy range. Micromegas detectors are considered as baseline technology for BabyIAXO thanks to the relatively high efficiency and very low background level. Other detector technologies developed to reach better energy resolution while maintaining high efficiency and low background level are also under study. In this paper, we review the BabyIAXO design and present the analysis of data taken with the prototype of an IAXO Micromegas detector. A background level of 8.8×10−7counts keV−1cm−2s−1 was reached.

Dead layer estimation of an HPGe detector using MCNP6 and Geant4

In this study, Monte Carlo simulations were used to calculate the full-energy peak efficiency of a p-type coaxial high-purity germanium (HPGe) detector. The HPGe detector was modeled using MCNP6 and Geant4, and the thickness of the dead layer of germanium crystals was estimated for an accurate simulation. The dead layer was divided into front and side components, where a point source and a Marinelli beaker source were used to estimate each dead layer thickness. The model was validated by comparing the simulated as well as experimental results for the standard sources of cylindrical and Marinelli beakers. The Geant4 results and experimental results matched up to 4% in the 59.54–1836.05 keV energy range, while MCNP6 matched up to 6% when adjusted for coincidence summing effects. HPGe detector modeled in Monte Carlo simulations can be utilized for experimental validation and experimental setup prior to using actual HPGe detectors.

COMPARISON BTWEEN THE RELATIONS OF HpGe DETECTOR EFFICIENCY CURVE AND BACKGROUND “SPECTRUM SHAPE”

The full energy peak efficiency (ɛ) relation of HpGe detector is determined and compared with the "spectrum shape" relation of natural background (BG) for the (121.8-1408) keV energy range. A one liter Marinelli beaker soil standard containing the Eu-152 material is used in calibration and measurement. A MATLAB fitting program were used obtain the efficiency relation from the experimental values, and to obtain the BG "spectrum shape" relation from the count rates at the corresponding energy values used. The ɛ / BG factor values were 1.154 at the 121.8keV and increase with energy till reaching a maximum value of 4.358 at about 778keV energy and then decrease. These values may be used to extract efficiency from the BG values at the specified measurement conditions. The obtained results may participate in extending our understanding of the standardization concept in radiation measurements.

An integrated system for user-friendly X-ray intensity attenuation in a wide energy range

For undulator hard X-ray beamlines of a wide energy range, the beam intensity control is often needed to regulate the photon flux impinging on delicate detectors. Despite the capability of state-of-the-art X-ray pixel detectors being greatly advanced recently, the frontier undulator beamlines in synchrotron facilities often carry outstanding photon fluxes that are sometimes too high for certain measurements. Here, we report a developed protocol that allows intensity attenuation of an X-ray beam in the 4-23 keV energy range with flexible attenuation factors; a prototype is installed and tested on the 13A biological small-angle X-ray scattering beamline of the 3 GeV Taiwan Photon Source (TPS) of the National Synchrotron Radiation Research Center, Hsinchu, Taiwan. The intensity attenuation system is modified from a commercially available pneumatically actuated, vacuum-type precision X-ray attenuator of ADC ABS-300; the system provides beam attenuation factors covering 8 orders of intensity attenuation for an X-ray beam in 4-23 keV. This was achieved with selected combinations of 10 sets of metal foils comprising different thicknesses of Al, Ti, Cu, and Ta foils. A user-friendly protocol is established to automatically compare a subscribed attenuation factor with all the possible attenuation factors from the 1024 combinations of the 10 sets of foils in the X-ray energy used, and determine a set of the metal foils having a best-matched attenuation factor. Calculation of beam intensity attenuations with the selected foils is coded with Python and integrated into the Experimental Physics and Industrial Control System (EPICS). The input of an attenuation factor is done through a graphical display of the attenuator system based on the Control System Studio (CSS). The developed X-ray beam attenuation system provides a convenient and intuitive beam intensity control and has the potential to be adopted in future beamlines.

Characteristics of Natural Background Radiation in the Lubin Mine, Poland

There has been growing interest in using underground locations for applications in various fields, including research. In Poland, for several years, attempts have been made to build an underground laboratory. For this purpose, selecting an appropriate location requires a detailed analysis of the level of natural radioactivity. The present study presents detailed characteristics of the natural background radiation in close vicinity to shaft L-VI of the Lubin mine, at the depth of 910 m (2275 m w.e.). The in situ measurement of the photon flux in the 7–3150 keV energy range was equal to 8.08 ± 0.90 cm−2s−1, and the gamma-ray dose rate of 0.070 ± 0.010 µSv/h with the highest contribution from 40K and 214B isotopes. The thermal neutron flux measured using helium counters was equal to 4.2 ± 0.9 × 10−6 cm−2s−1. The radon concentration in the air measured with the RAD7 monitor showed low values ranging from 0 to 15.3 Bq/m3. Laboratory measurements of rocks using alpha and gamma spectrometry techniques showed a significant variation in the concentration of 226Ra and 234,238U isotopes, and the highest concentration values were recorded for shales. The 40K, 234,238U and 226Ra isotopes make the greatest contribution to the natural radioactivity of analyzed rocks.

Electron conditioning of technical surfaces at cryogenic and room temperature in the 0–1 keV energy range

In the superconducting magnets of the Large Hadron Collider (LHC) at CERN, most of the beam-induced heat load is intercepted by a beam-screen (BS) cryogenically cooled to 5–20 K. When circulating the bunched proton beam, an electron cloud (EC) can form and bombard the BS copper surface with high doses of predominantly low-energy electrons, which desorb gas and consequently increase the pressure. The beam-induced pressure rise decreases during operation as the electron irradiation diminishes the secondary electron yield (SEY) and the electron-stimulated desorption (ESD) yield, a phenomenon referred to as ‘beam conditioning’. Low ESD and SEY values achieved rapidly are requisite to mitigate EC and maintain UHV in storage rings. We report data on ESD and SEY electron conditioning completed at cryogenic temperature with 0–1 keV electrons up to an electron dose of 5.10−3 C mm−2. Our results show that SEY conditioning depends on the primary electron energy and also that ESD yield significantly decreases with temperature. At 15 K, the amorphous-carbon coating and laser-treated copper present SEY below 1.1 and have initial ESD yields 3–6 times lower than OFE copper. Our results conform to the SEY and ESD's general understanding and extend it towards cryogenic temperatures.

Constraining the Nature of the 18 min Periodic Radio Transient GLEAM-X J162759.5-523504.3 via Multiwavelength Observations and Magneto-thermal Simulations

We observed the periodic radio transient GLEAM-X J162759.5-523504.3 (GLEAM-X J1627) using the Chandra X-ray Observatory for about 30 ks on 2022 January 22–23, simultaneously with radio observations from the Murchison Widefield Array, MeerKAT, and the Australia Telescope Compact Array. Its radio emission and 18 min periodicity led the source to be tentatively interpreted as an extreme magnetar or a peculiar highly magnetic white dwarf. The source was not detected in the 0.3–8 keV energy range with a 3σ upper limit on the count rate of 3 × 10−4 counts s−1. No radio emission was detected during our X-ray observations either. Furthermore, we studied the field around GLEAM-X J1627 using archival European Southern Observatory and DECam Plane Survey data, as well as recent Southern African Large Telescope observations. Many sources are present close to the position of GLEAM-X J1627, but only two within the 2″ radio position uncertainty. Depending on the assumed spectral distribution, the upper limits converted to an X-ray luminosity of L X < 6.5 × 1029 erg s−1 for a blackbody with temperature kT = 0.3 keV, or L X < 9 × 1029 erg s−1 for a power law with photon index Γ = 2 (assuming a 1.3 kpc distance). Furthermore, we performed magneto-thermal simulations for neutron stars considering crust- and core-dominated field configurations. Based on our multiband limits, we conclude that (i) in the magnetar scenario, the X-ray upper limits suggest that GLEAM-X J1627 should be older than ∼1 Myr, unless it has a core-dominated magnetic field or has experienced fast cooling; (ii) in the white dwarf scenario, we can rule out most binary systems, a hot sub-dwarf, and a hot magnetic isolated white dwarf (T ≳ 10.000 K), while a cold isolated white dwarf is still compatible with our limits.

Seven Years of Coordinated Chandra–NuSTAR Observations of SN 2014C Unfold the Extreme Mass-loss History of Its Stellar Progenitor

We present the results from our 7 yr long broadband X-ray observing campaign of SN 2014C with Chandra and NuSTAR. These coordinated observations represent the first look at the evolution of a young extragalactic SN in the 0.3–80 keV energy range in the years after core collapse. We find that the spectroscopic metamorphosis of SN 2014C from an ordinary type Ib SN into an interacting SN with copious hydrogen emission is accompanied by luminous X-rays reaching L x ≈ 5.6 × 1040 erg s−1 (0.3–100 keV) at ∼1000 days post-explosion and declining as L x ∝ t −1 afterwards. The broadband X-ray spectrum is of thermal origin and shows clear evidence for cooling after peak, with . Soft X-rays of sub-keV energy suffer from large photoelectric absorption originating from the local SN environment with . We interpret these findings as the result of the interaction of the SN shock with a dense (n ≈ 105 − 106 cm−3), H-rich disk-like circumstellar medium (CSM) with inner radius ∼2 × 1016 cm and extending to ∼1017 cm. Based on the declining NHint(t) and X-ray luminosity evolution, we infer a CSM mass of ∼(1.2 f–2.0 , where f is the volume filling factor. We place SN 2014C in the context of 121 core-collapse SNe with evidence for strong shock interaction with a thick circumstellar medium. Finally, we highlight the challenges that the current mass-loss theories (including wave-driven mass loss, binary interaction, and line-driven winds) face when interpreting the wide dynamic ranges of CSM parameters inferred from observations.

Active Region Extent Assessment with X-rays (AREA-X)

The development of semiconductor sensors for new particle tracking detectors places increasing limits on sensor characteristics such as uniformity, size and shape of inefficient areas and size of active compared to inactive sensor areas. Accurately assessing these relatively subtle effects requires either measurements in particle beams or the modification of samples to be used in dedicated laser test setups.Active Region Extent Assessment with X-rays (AREA-X) has been developed as an alternative method for the fast, efficient and precise study of the active area of a semiconductor sensor. It uses a monochromatic, micro-focused X-ray beam with a 10–20 keV energy range as provided by several synchrotron beam lines and uses the photo current induced in the sensor to measure the depth of the responsive sensor volume. It can be used to study local inhomogeneities or inefficiencies, the overall extent of the active sensor volume and its shape and its localised application, which makes the need to gather statistics over a large area unnecessary, allowing for fast readout, which enables studies of the sensor behaviour at a range of external parameters, e.g. temperature or applied bias voltage.This paper presents the measurement concept and technical setup of the measurement, results from initial measurements as well as capabilities and limitations of the method.

Assessment of the detection efficiency calibration of high-resolution gamma-ray spectrometers by EGSnrc and MCNP6.2 Monte Carlo codes

Determination of the activity content of radionuclides with high accuracy and precision with gamma-ray spectrometry is strongly based on the detection efficiency calibration of the detector. The detector efficiency calibration is determined with standard reference sources and/or Monte Carlo codes. The current study provides methodology that can be used to generate efficiency curve with simulations instead of experiments. As a result, the need for additional experiments can be reduced. The implementation of a specific script written on EGSnrc Monte Carlo code was investigated to calculate the detection efficiency with high-level accuracy for high-purity germanium (HPGe) spectrometry. For this purpose, two HPGe detectors (ORTEC and PGT) used routinely in the activity measurement of gamma emitting radionuclides were modelled with EGSnrc code to obtain detection efficiencies for 40–2000 keV energy range. The detector models were benchmarked against MCNP6.2 Monte Carlo code with a hypothetical source geometry. The code-to-code comparison between EGSnrc and MCNP6.2 codes indicted that the codes can be used to generate a reliable detection efficiency curve. The benchmark results showed that median arithmetic deviations of the efficiencies of ORTEC and PGT detectors are found as 0.88% and 1.69%, respectively. The experimental studies were performed with 22Na, 57Co, 60Co, 137Cs, and 241Am standard disc sources for the ORTEC detector and with in-house prepared 152Eu sandwich-type source for the PGT detector. The sources were counted in the energy range of 59.5–1408 keV. The efficiency values from simulations were used in the calculation of the activities of the aforementioned gamma sources with a mathematical formula and resulting measured activity values were compared with reference activity values given in the certificates. In addition, the applicability of spreadsheet approach that is usually used to determine the combined standard uncertainty for alpha-particle spectrometry was investigated for gamma-ray spectrometry. The performance of the recommended procedure was scored in terms of relative bias, z-score, u-test, trueness, and precision. The activity results obtained with simulated efficiencies showed good agreement with certified values.