Relative Standard Uncertainty Research Articles

Partial Acquisition of Spectral Projections Accelerates Four-dimensional Spectral-spatial EPR Imaging for Mouse Tumor Models: A Feasibility Study.

Our study aimed to accelerate the acquisition of four-dimensional (4D) spectral-spatial electron paramagnetic resonance (EPR) imaging for mouse tumor models. This advancement in EPR imaging should reduce the acquisition time of spectroscopic mapping while reducing quality degradation for mouse tumor models. EPR spectra under magnetic field gradients, called spectral projections, were partially measured. Additional spectral projections were later computationally synthesized from the measured spectral projections. Four-dimensional spectral-spatial images were reconstructed from the post-processed spectral projections using the algebraic reconstruction technique (ART) and assessed in terms of their image qualities. We applied this approach to a sample solution and a mouse Hs766T xenograft model of human-derived pancreatic ductal adenocarcinoma cells to demonstrate the feasibility of our concept. The nitroxyl radical imaging agent 2H,15N-DCP was exogenously infused into the mouse xenograft model. The computation code of 4D spectral-spatial imaging was tested with numerically generated spectral projections. In the linewidth mapping of the sample solution, we achieved a relative standard uncertainty (standard deviation/| mean |) of 0.76 μT/45.38 μT = 0.017 on the peak-to-peak first-derivative EPR linewidth. The qualities of the linewidth maps and the effect of computational synthesis of spectral projections were examined. Finally, we obtained the three-dimensional linewidth map of 2H,15N-DCP in a Hs766T tumor-bearing leg in vivo. We achieved a 46.7% reduction in the acquisition time of 4D spectral-spatial EPR imaging without significantly degrading the image quality. A combination of ART and partial acquisition in three-dimensional raster magnetic field gradient settings in orthogonal coordinates is a novel approach. Our approach to 4D spectral-spatial EPR imaging can be applied to any subject, especially for samples with less variation in one direction.

Study on the provision of traceable flow rate of water vapor for calibrating a time-of-flight mass spectrometer

Forming a traceable flow rate is the key to mass spectrometer calibration, and the flow rate can be calculated through the conductance. The theoretical and experimental analysis of measuring the conductance of water vapor using the VΔp measurement method is presented, the measurement error of that method increases with the decrease of flow rate, which is due to the strong adsorption characteristic of water vapor. Based on the VΔp measurement method, a new method called the pΔt measurement method is proposed to give the relationship between the orifice conductance and the inlet pressure for water vapor, and the conductance can be calculated by measuring the time of pressure change, which can correct the adsorption influence of water vapor on the measurement of conductance. The relative standard uncertainty of the pΔt measurement method is 8%. The conductance of an orifice, whose diameter is about 22.2 µm, was measured by that method, and the measurement results agree well with the theoretical values. According to those two methods, an apparatus was developed to calibrate a miniature time-of-flight mass spectrometer (TOF-MS) for water vapor, and it can supply the flow rate of water vapor in the range from 3.67 × 10−9 to 2.19 × 10−5 Pa m3 s−1. Finally, there is a linear relationship between the signal and the flow rate for water vapor in the range from 1.39 × 10−8 to 1.29 × 10−5 Pa m3 s−1.

Rapid determination of impurities in carbon dioxide for food by gas chromatography

This article describes the experimental principle and method of rapid determination of carbon monoxide, methane, propane, total hydrocarbon, methanol, ethylene oxide, acetaldehyde, vinyl chloride, benzene, and other common impurities in carbon dioxide by gas chromatograph. By using food additive carbon dioxide as a sample, the rapid analysis conditions, such as chromatographic column, valve switching time, and column box temperature control, were optimized. The retention time of impurity components in food additive carbon dioxide was determined using the external standard method. The relative standard uncertainty of CH4, C3H8, CO, CH3OH, CH2CH2O, CH3CHO, CH2CHCl, and C6H6 analysis is within 3% by using the established analytical method proposed in this article, which is equivalent to the national standard GB 1886.228-2016. The linear correlation coefficient r is greater than 0.9995, and the linear error is not greater than 2.0, indicating excellent linearity. In the meantime, in the case of 6 consecutive sample injections, the detection time is shortened by nearly three times. The experimental results show that the analytical method established in this article is suitable for the rapid determination of impurities in carbon dioxide for food, which can improve the accuracy of experimental results and work efficiency.

Remote measurement and calibration of alpha-emitting radionuclides through the utilization of characteristic ultraviolet fluorescence

During the decommissioning of nuclear facilities and spent fuel reprocessing, conventional alpha particle detectors are insufficient for accurately measuring the emissivity of alpha particles due to their high radiation intensity and complex nuclide types. The air fluorescence method is developed to detect the α particle emissivity through measuring the intensity of ultraviolet fluorescence generated by the interaction between α particles and nitrogen or other inert gas mediums. This method offers advantages such as long detection range and immunity to γ radiation interference. The measurement results are primarily influenced by factors including α particle energy, detection distance, and gas medium composition, with photon noise and detection distance determining the detection limit. The obtained results indicate that: In the condition of measured in darkness, measurement time for 1000s, and distance for 1 m, The minimum detection limit for α sources is 7.6 kBq with a relative standard uncertainty of 10%.

MSL goniospectrophotometer measurement model

Measurements of both hemispherical reflectance and the bidirectional reflectance distribution function (BRDF) are of interest to a wide range of industries including computer graphics, remote sensing, lighting design, and cosmetics. The scale of directional reflectance is often realised at national metrology institutes using goniospectrophotometers, and by integrating BRDF measurements made over the hemisphere, the scale of hemispherical reflectance can also be realised. This paper describes the measurement model for BRDF and hemispherical reflectance using the MSL goniospectrophotometer, which uses rotation stages to adjust the angle of the sample. The measurement model is applied to measurements of a white Spectralon sample and a white ceramic tile to demonstrate the performance of the instrument. The relative standard uncertainty in the BRDF of a white Spectralon sample at 550 nm is less than 0.1% for in-plane measurements, while the relative standard uncertainty in the hemispherical reflectance of a white Spectralon sample at 560 nm is 0.27%.

A Study on the Uncertainty of the Average Glandular Dose in Quality Control of Mammographic X-ray Units

【Purpose】 Accurate control of X-ray units and dosimeters and analysis of the uncertainties associated with the accurate measurement of radiation doses are essential for the effective establishment and application of diagnostic reference levels. In this study, the uncertainty of the average glandular dose (AGD) in the quality control of mammography equipment was evaluated in detail, and recommendations were provided to improve the accuracy and safety of radiological practice. 【Methods】 In the uncertainty analysis of the AGD, the relative standard uncertainties in the measurements of the half-value layer, the incident air kerma, and the conversion factor were considered and finally expressed as expanded uncertainties, the intervals of which were clearly defined. 【Results】 From the AGD measurements using two types of dosimeters, it was found that the primary sources of uncertainty are the uncertainty of the calibration factors of the dosimeters and the uncertainty of the conversion factors.【Conclusion】 To reduce uncertainty, the use of regularly calibrated dosimeters is effective and reliable. Two types of dosimeters are commonly used; the results of this study may serve as a reference value for the uncertainty of AGD in quality control in medical facilities.

Calculation of the Budget of Uncertainty on Measurements Size Nanoparticles Using Dynamic Light Scattering

Accurate nanoparticle characterization is essential since it can significantly affect its physicochemical and biological properties. Among physicochemical properties used to characterize nanomaterials, size and size distribution are essential and should be assessed before surveying poisonousness or biocompatibility. Several methods are suitable to evaluate these characteristics including the dynamic light scattering. The aims of the present paper were to propose a methodology to measure nanoparticle size and present the estimation of the particle size uncertainty using the dynamic light scattering technique. The reliability of measurements was ensured by a series of handling precautions and quality criteria for good measurements to be applied for methodology validation using reference material polyvinylpyrrolidone coated silver nanoparticles. The identification and quantification of input quantities to the measurement uncertainties were estimated. The uncertainty concerning the equipment was 1.2% while the repeatability obtained was 1.4%, within the range of values stipulated in the reference standard (less than 5%). The relative standard uncertainties of trueness and repeatability were below the thresholds defined by the International Organization for Standardization. The result of the expanded uncertainty was 3.9% with 95% coverage probability for the reference material.

A method for measuring the solid circulation rates of CFB boilers based on the particle flow-around principle

The solid circulation rate (Gs) is a key parameter for the design and operation of a circulating fluidized bed (CFB) industrial equipment, while the detection and measurement of the Gs value in an actual industrial CFB equipment remains difficult. To fill this gap, a method for the Gs measurement based on the flow-around principle was proposed in this study. The mathematical model for the signal transformation was established along the path “detected strain value – impact force – particle velocity – Gs value”, and the corresponding measurement device was also developed. The performance of the Gs measurement device was quantitatively validated in cold-state experiments and semi-quantitatively verified in an industrial trial in a CFB boiler. The results of a theoretical analysis indicate that the detected strain linearly increased with the impact force received by the intrusive spherical obstacle, and the slope coefficient was determined as per the experiment. The correlation of the impact force to the particle flow velocity was proposed and fitted using the experimental data. The computational particle fluid dynamics method was applied to simulate the particle flow field in the standpipe of the CFB boiler to determine the installation location of the Gs measurement device. The lab-scale cold-state experiments showed that the relative standard uncertainty of the Gs measurement using the device built in the present study was less than 2.0 %. This device was then applied in an industrial trial in a 116 MWth CFB boiler and the results proved the feasibility and applicability of the proposed Gs measurement method.

Charge collection efficiency of commercially available parallel-plate ionisation chambers in ultra-high dose-per-pulse electron beams

Objective. This investigation aims to experimentally determine the charge collection efficiency (CCE) of six commercially available parallel-plate ionisation chamber (PPIC) models in ultra-high dose-per-pulse (UHDPP) electron beams. Approach. The CCE of 22 PPICs has been measured in UHDPP electron beams at the National Metrology Institution of Germany (PTB). The CCE was determined for a dose per pulse (DPP) range between 0.1 and 6.4 Gy (pulse duration of 2.5 μs). The results obtained with the different PPICs were compared to evaluate the reproducibility, intra- and inter-model variation, and the performance of a CCE empirical model. Main results. The intra-model variation was, on average, 4.0%, which is more than three times the total combined relative standard uncertainty and was found to be greater at higher DPP (up to 20%). The inter-model variation for the PPIC with 2 mm electrode spacing, which was found to be, on average, 10%, was also significant compared to the relative uncertainty and the intra-model variation. The observed CCE variation could not be explained only by the expected deviation of the electrode spacing from the nominal value within the manufacturing tolerance. It should also be noted that a substantial polarity effect, between 0.914(5) and 1.201(3), was observed, and significant intra- and inter-model variation was observed on this effect. Significance. For research and pre-clinical study, the commercially available PPIC with a well-known CCE (directly measured for the specific chamber) and with a small electrode spacing could be used for relative and absolute dosimetry with a lower-limit uncertainty of 1.6% (k = 1) in the best case. However, to use a PPIC as a secondary standard in UHDPP electron beams for clinical purposes would require new model development to reduce the ion recombination, the polarity effect, and the total standard uncertainty on the dose measurement.

Enhancing Precision in L-band Electron Paramagnetic Resonance Tooth Dosimetry: Incorporating Digital Image Processing and Radiation Therapy Plans for Geometric Correction.

Following unforeseen exposure to radiation, quick dose determination is essential to prioritize potential patients that require immediate medical care. L-band electron paramagnetic resonance tooth dosimetry can be efficiently used for rapid triage as this poses no harm to the human incisor, although geometric variations among human teeth may hinder accurate dose estimation. Consequently, we propose a practical geometric correction method using a mobile phone camera. Donated human incisors were irradiated with calibrated 6-MV photon beam irradiation, and dose-response curves were developed by irradiation with a predetermined dose using custom-made poly(methyl methacrylate) slab phantoms. Three radiation treatment plans for incisors were selected and altered to suit the head phantom. The mean doses on tooth structures were calculated using a commercial treatment planning system, and the electron paramagnetic resonance signals of the incisors were measured. The enamel area was computed from camera-acquired tooth images. The relative standard uncertainty was rigorously estimated both with and without geometric correction. The effects on the electron paramagnetic resonance signal caused by axial and rotational movements of tooth samples were evaluated through finite element analysis. The mean absolute deviations of mean doses both with and without geometric correction showed marginal improvement. The average relative differences without and with geometric correction significantly decreased from 21.0% to 16.8% (p = 0.01). The geometric correction method shows potential in improving dose precision measurement with minimal delay. Furthermore, our findings demonstrated the viability of using treatment planning system doses in dose estimation for L-band electron paramagnetic resonance tooth dosimetry.

Adapting a practical EPR dosimetry protocol to measure output factors in small fields with alanine.

Modern radiotherapy techniques often deliver small radiation fields. In this work, a practical Electron Paramagnetic Resonance (EPR) dosimetry protocol is adapted and applied to measure output factors (OF) in small fields of a 6 MV radiotherapy system. Correction factors and uncertainties are presented and OFs are compared to the values obtained by following TRS-483 using an ionization chamber (IC). Irradiations were performed at 10cm depth inside a water phantom positioned at 90cm source to surface distance with a 6 MV flattening filter free photon beam of a Halcyon radiotherapy system. OFs for different nominal field sizes (1×1, 2×2, 3×3, 4×4, normalized to 10×10 cm2 ) were determined with a PinPoint 3D (PTW 31022) IC following TRS-483 as well as with alanine pellets with a diameter of 4mm and a height of 2.4mm. EPR readout was performed with a benchtop X-band spectrometer. Correction factors due to volume averaging and due to positional uncertainties were derived from 2D film measurements. OFs obtained from both dosimeter types agreed within 0.7% after applying corrections for the volume averaging effect. For the used alanine pellets, volume averaging correction factors of 1.030(2) for the 1×1 cm2 field and <1.002 for the larger field sizes were determined. The correction factor for positional uncertainties of 1mm was in the order of 1.018 for the 1×1 cm2 field. Combined relative standard uncertainties uc for the OFs resulting from alanine measurements were estimated to be below 1.5% for all field sizes. For IC measurements, uc was estimated to be below 1.0%. A practical EPR dosimetry protocol is adaptable for precisely measuring OFs in small fields down to 1×1cm2 . It is recommended to consider the effect of positional uncertainties for field sizes <2×2cm2 .

Spectral aerosol optical depth from SI-traceable spectral solar irradiance measurements

Abstract. Spectroradiometric measurements of direct solar irradiance traceable to the SI were performed by three spectroradiometer systems during a 3-week campaign in September 2022 at the Izaña Atmospheric Observatory (IZO) located on the island of Tenerife, Canary Islands, Spain. The spectroradiometers provided direct spectral irradiance measurements in the spectral ranges 300 to 550 nm (QASUME), 550 to 1700 nm (QASUME-IR), 300 to 2150 nm (BiTec Sensor, BTS), and 316 to 1030 nm (Precision Solar Spectroradiometer, PSR), with relative standard uncertainties of 0.7 %, 0.9 %, and 1 % for QASUME/QASUME-IR, the PSR, and the BTS respectively. The calibration of QASUME and QASUME-IR was validated prior to this campaign at Physikalisch-Technische Bundesanstalt (PTB) by measuring the spectral irradiance from two spectral irradiance sources, the high-temperature blackbody BB3200pg as a national primary standard and the tuneable laser facility TULIP. The top-of-atmosphere (ToA) solar irradiance spectra from the spectroradiometers were retrieved from direct solar irradiance measurements using zero-air-mass extrapolation during cloud-free conditions, which were then compared to the TSIS-1 Hybrid Solar Reference Spectrum (HSRS). These ToA solar spectra agreed to within 1 % for spectral ranges longer than 400 nm (for QASUME also at shorter wavelengths) in the spectral regions free of significant trace gas absorption and were well within the combined uncertainties over the full investigated spectral range. Using the results from the comparison with QASUME, the relative standard uncertainty of the TSIS-1 HSRS ToA solar spectrum in the spectral range 308 to 400 nm could be reduced from its nominal 1.3 % to 0.8 %, representing the relative standard uncertainty of the QASUME ToA solar spectrum in this spectral range. The spectral aerosol optical depth (AOD) retrieved from the solar irradiance measurements of these spectroradiometers using the TSIS-1 HSRS as the reference ToA solar spectrum agreed to within 0.01 in optical depth in nearly all common spectral channels of two narrowband filter radiometers belonging to the Global Atmosphere Watch Precision Filter Radiometer (GAW-PFR) network and Aerosol Robotic Network (AERONET). This study shows that it is now possible to retrieve spectral AOD over the extended spectral range from 300 to 1700 nm using solar irradiance measurements traceable to the SI using laboratory-calibrated spectroradiometers with similar quality to that from traditional Langley-based calibrated instruments. The main improvement to previous investigations is the recent availability of the high-spectral-resolution TSIS-1 HSRS with very low uncertainties, which provides the top-of-atmosphere reference for the spectral atmospheric transmission measurements obtained from ground-based solar irradiance measurements.

Low-noise switched integration amplifier forlow-photon flux radiometry.

A photodetector signal-to-noise ratio (SNR) over 1000 is one of the prerequisites to realizing the correlated photon radiometric benchmark with a relative standard uncertainty of 0.3% (k=1). To improve the SNR for low-photon flux detection, a switched integration amplifier (SIA) is designed to achieve a noise equivalent current of a fA level. A wide spectrum and low-photon flux measurement facility are built to evaluate the SNR at a photon rate of 108 s -1 within the spectral range of 350-1000nm. SNRs of the SIA-based Si photodetector are shown to be greater than 1000 at representative wavelengths.

Verifying measurements on Siemens Atellica® instruments using clinically acceptable analytical performance specifications

Measurements on clinical chemistry analysers must be verified to demonstrate applicability to their intended clinical use. We verified the performance of measurements on the Siemens Atellica® Solution chemistry analysers against the clinically acceptable analytical performance specifications, CAAPS, including the component of intra-individual biological variation, CVI . The relative standard uncertainty of measurement, i.e. analytical variation, CVA , was estimated for six example measurands, haemoglobin A1c in whole blood (B-HbA1c), albumin in urine (U-Alb), and the following measurands in plasma: sodium (P-Na), pancreatic amylase (P-AmylP), low-density lipoprotein cholesterol (P-LDL-C), and creatinine (P-Crea). Experimental CVA was calculated from single-instrument imprecision using control samples, variation between measurements on parallel instruments, and estimation of bias with pooled patient specimens. Each obtained CVA was compared with previously developed CAAPS. The calculated CVA was 1.4% for B-HbA1c (CAAPS 1.9% for single diagnostic testing, CAAPS 2.0% for monitoring after duplicate tests; IFCC units), 10.9% for U-Alb (CAAPS 44.9%), 1.2% for P-Na (CAAPS 0.6%, after triplicate testing 1.5%), 8.2% for P-AmylP (CAAPS 22.9%). The CVA was 4.9% for P-LDL-C (CAAPS for cardiovascular risk stratification 4.9% after four replicates), and 4.2% for P-Crea (CAAPS 8.0%). Three of the six measurands fulfilled the estimated clinical need. Results from P-Na measurements indicate a general need for improving the P-Na assays for emergency patients. It is necessary to consider CVI when creating diagnostic targets for laboratory tests, as emphasised by the CAAPS estimates of B-HbA1c and P-LDL-C.

Nonlinearity Measurement of Si Transferring Photodetector in the Low Radiation Flux Range

In order to establish a transferring chain from a photon flux of a single-photon source in quantum radiometry, the nonlinearity of the photodetector needs to be accurately measured. Using the flux superposition method, a nonlinearity measurement setup has been designed. The measurement setup consists of two tungsten halogen lamps, parent–child integrating spheres, an adjustable aperture, a diaphragm tube, and an optical filter. It has the advantage of low polarization error, low interference error, and low stray light effect. The Si photodiode to be measured is cooled to −40 °C to obtain a low noise level for low-flux radiation measurement. The nonlinearity of the Si photodetector is measured for photocurrent ranges from 10−12 A~10−6 A level, with a relative standard uncertainty from 0.0092~0.023%. The relative standard uncertainty of the nonlinearity correction factor ranged from 0.023~0.049%.

Speeds of Sound in Binary Mixtures of Water and Carbon Dioxide at Temperatures from 273 K to 313 K and at Pressures up to 50 MPa

Knowledge of thermodynamic properties of aqueous solutions of CO2 is crucial for various applications including climate science, carbon capture, utilisation and storage (CCUS), and seawater desalination. However, there is a lack of reliable experimental data, and the equation of state (EOS) predictions are not reliable, particularly for sound speeds in low CO2 concentrations typical of water resources. For this reason, we have measured speeds of sound in three different aqueous solutions containing CO2. We report speeds of sound in the single-phase liquid region for binary mixtures of water and CO2 for mole fractions of CO2 of 0.0118, 0.0066 and 0.0015 at temperatures from 273.15 K to 313.15 K and at pressures up to 50 MPa, measured using a dual-path pulse-echo apparatus. The relative standard uncertainties of the sound speeds are 0.05 %, 0.03 % and 0.01 % at 0.0118, 0.0066 and 0.0015 CO2 mole fractions, respectively. The change in sound speeds as functions of composition, pressure and temperature are analysed in this study. We find that dissolution of CO2 in water increases its sound speeds at all conditions, with the greatest increase occurring at the highest mole fractions of CO2. Our sound speed data agree well with the limited available experimental data in the literature but deviate from the EOS-CG of Gernert and Span by up to 7 % at the lowest temperatures, highest pressures, and highest CO2 mole fraction. The new low-uncertainty sound speed data presented in this work could provide a basis for development of an improved EOS and in establishing reliable predictions of the change in thermodynamic properties of seawater-like mixtures due to absorption of CO2 gas.

Assessing comparability and uncertainty of analytical methods for methylated mercury species in seawater

BackgroundThe relative distribution and importance of monomethylmercury (MMHg) and dimethylmercury (DMHg) in seawater is still under debate. A lack of comparability between measurements at sub-picomolar levels hampered the further understanding of the biogeochemical Hg cycle. To overcome this, we assessed the relative standard measurement uncertainties (Uex,r) for direct measurements of MMHg and DMHg by species-specific isotope dilution ICP-MS and cryo-focusing GC-ICP-MS at femtomolar concentrations. Furthermore, Uex,r was determined for the indirect determination of DMHg (DMHgcalc = MeHg - MMHg) and MeHg (MeHgcalc = MMHg + DMHg) to compare the two methodologies. ResultsExpanded Uex,r (confidence interval of 95%) for cryo-focusing GC-ICP-MS was 14.4 (<50 fM) and 14.2% (>50 fM) and for SS-ID GC-ICP-MS 5.6 (<50 fM) and 3.7% (>50 fM). For concentrations above 50 fM, Uex,r for DMHgcalc was always lower than for direct measurements (14.2%). For MeHgcalc, on the other hand, Uex,r was always higher for concentrations above 115 fM (range: 3.7–13.9%) than for direct measurements (3.7%). We evaluated the comparability of directly measured and calculated DMHg and MeHg concentrations based on Hg speciation measurements for two vertical profiles in the Mediterranean Sea. We show that directly measured and indirectly determined DMHg and MeHg concentrations yield comparable results. SignificanceOur results validate the application of the indirect method for the determination of DMHg if a direct measurement method with a low Uex,r such as isotope dilution is used for MMHg and MeHg measurements. The validation of the indirect measurement approach opens new possibilities to generate more precise and accurate DMHg data in the global ocean.

National round robin test (RRT) for delamination strength testing YBCO HTS wires at room temperature (RT) and 77K

Second generation high temperature superconducting coated conductors (2G HTS CCs) have become indispensable wires for high-field superconducting magnets. The transverse mechanical delamination strength (MDS) is a key parameter due to the multilayer structure of CCs. Determination of the MDS value is thus significant. In this study, we report the MDS results of national round robin test (RRT) conducted in china by the institutions of Lanzhou University, Institute of Plasma Physic, and Shanghai Superconductor Technology Co., Ltd at room temperature (RT) and 77 K, respectively, for the determination of 2G HTS CCs (copper-stabilized) transverse MDS by a standardized procedure. Data at RT and 77 K all showed good consistency, with the relative standard uncertainty of 2.22% and 2.35%, respectively, illustrating the reliability of the established procedure, which can be used as a reference for engineering CC manufacturing and design of application magnets.

A Compact High-Stability Nanosecond Pulse Test System Using Corona-Stabilized Switch and Coaxial Resistance Divider

Due to the lack of a standard nanosecond high-voltage pulse generator for sensor calibration, a high-stability nanosecond high-voltage pulse test system was developed in terms of circuit analysis, structural design, and performance test. By establishing the equivalent circuit model of the nanosecond pulse generator, the circuit component parameters of the five-stage Marx loop and the one-stage compression steepening unit were simulated. The influence of the action performance of the steepening gap on the characteristics of output nanosecond pulse was analyzed. The nanosecond pulse test system was established through the structural design of the nanosecond pulse-generating circuit, the development of a high-performance corona-stabilized switch, and the measurement of a fast-response resistance divider made of metal oxide thin-film resistors. The nanosecond pulse test system has the capability to output a double exponential nanosecond pulse voltages in the amplitude range of 10–60 kV with a rise time of 2.3 ± 0.5 ns and a half-peak time of 23 ± 5 ns. In addition, the output pulse voltage has a high consistency and stability in the full amplitude range. The maximum relative standard deviation of the peak value is 1.517%, and the relative standard uncertainty is less than 5‰.

The PTB water calorimeter for determining the absolute absorbed dose to water in ultra-high pulse dose rate electron beams

Objective. The purpose of this investigation is to establish the water calorimeter as the primary standard in PTB’s ultra-high pulse dose rate (UHPDR) 20 MeV reference electron beams. Approach. The calorimetric measurements were performed at the PTB research linac facility using the UHPDR reference electron beam setups that enable a dose per pulse between about 0.1 Gy and 6 Gy. The beam is monitored by an in-flange integrating current transformer. The correction factors required to determine the absorbed dose to water were evaluated using thermal and Monte Carlo simulations. Measurements were performed with different total doses delivered per pulse by modifying the instantaneous dose rate within a pulse and by changing the pulse length. The obtained temperature–time traces were compared to the simulated ones to validate the thermal simulations. In addition, absorbed-dose-to-water measurements obtained using the secondary standard alanine dosimeter system were compared to measurements performed with the primary standard. Main results. The simulated and measured temperature–time traces were shown to be consistent, within combined uncertainties, with one another. Measurements with alanine dosimeters proved to be consistent within k = 1 of the total combined uncertainty with the absorbed dose to water determined using the primary standard. Significance. The total relative standard uncertainty of absorbed dose to water determined using the PTB water calorimeter primary standard in UHPDR electron beams was estimated to be less than 0.5%, and the combined correction factors were found to deviate from 1 by less than 1% for both PTB UHPDR 20 MeV reference electron beams. The water calorimeter is therefore considered to be an established primary standard for the higher energy UHPDR reference electron beams.