Measured Photon Energy Research Articles

Activity estimates of localised gamma emitting radionuclides using a GR-135 survey meter

During the operation of high energy accelerators activated materials are commonly created. The activity and isotopes present in these materials must be characterised for their clearance and release from the facility, or to ascertain their duration of stay in a radiological storage area. An activity estimate method using a gamma detecting GR-135 survey meter, which has the ability to collect an energy spectrum, is presented. Using several reference radioactive sources the detection efficiency and dead time of the survey meter were characterised. This information combined with the physical properties of the survey meter, the counting time and the properties of the measured photon energy emissions can be used to calculate an accurate activity estimate for localised activation on accelerator components, or loose contamination on isolated waste materials.

A prototype Radiation Energy Measuring Integrated Circuit with an asynchronous current-pulse reset block providing analog-to-digital conversion in 28 nm CMOS

In this paper we introduce a prototype Radiation Energy Measuring Integrated Circuit (REMIC) fabricated in a 28 nm CMOS process. The chip operates in a single-photon counting (SPC) mode and contains 100 pixels with a size of 50 μm × 50 μm. It is designed for precise energy measurements using asynchronous analogue-to-digital conversion. The proposed architecture allows both fast signal processing and precise energy measurement of incoming photons to be performed independently in each pixel, occupying a small pixel area. The integrated circuit (IC) has dimensions of 1.1 mm × 1.1 mm and is currently undergoing preliminary measurements. The paper focuses on the methodology used to mitigate process variations in each of the recording channels.

Electron and photon energy calibration with the ATLAS detector using LHC Run 2 data

This paper presents the electron and photon energy calibration obtained with the ATLAS detector using 140 fb-1 of LHC proton-proton collision data recorded at √(s) = 13 TeV between 2015 and 2018. Methods for the measurement of electron and photon energies are outlined, along with the current knowledge of the passive material in front of the ATLAS electromagnetic calorimeter. The energy calibration steps are discussed in detail, with emphasis on the improvements introduced in this paper. The absolute energy scale is set using a large sample of Z-boson decays into electron-positron pairs, and its residual dependence on the electron energy is used for the first time to further constrain systematic uncertainties. The achieved calibration uncertainties are typically 0.05% for electrons from resonant Z-boson decays, 0.4% at E T ∼ 10 GeV, and 0.3% at E T ∼ 1 TeV; for photons at E T ∼ 60 GeV, they are 0.2% on average. This is more than twice as precise as the previous calibration. The new energy calibration is validated using J/ψ → ee and radiative Z-boson decays.

Pure CsI electromagnetic calorimeter design for the Super Tau-Charm Facility

The Super Tau-Charm Facility (STCF) is a high-luminosity electron-positron collider proposed in China. It will operate in the energy region of 2–7 GeV with a peak luminosity of at least 0.5×1035 cm−2 s−1, providing an excellent platform for studying the tau-charm physics. The STCF detector includes an electromagnetic calorimeter (EMC), which plays a crucial role in the accurate measurement of photon energy. To address the challenge of achieving superior photon energy resolution in the high-rate environment caused by the high luminosity, a fast-response EMC based on pure CsI crystals is proposed for the STCF experiment. In this paper, we present the conceptual design of a pure CsI EMC for STCF. The light yield of a pure CsI unit designed for the STCF EMC was measured using cosmic rays. Without considering the mechanical structures of the EMC and the sub-detectors in front of the EMC, the performance of the pure CsI based EMC was studied through Geant4 simulations incorporating the measured light yield, and the EMC design was optimized based on the results. The simulation was carried out under the condition of 100 p.e./MeV light yield and the high background environment anticipated in the STCF experiment. By employing a waveform fitting method, an energy resolution of better than 2.5% for 1 GeV photons was achieved, which satisfies the major performance requirement for the STCF EMC. However, validation studies should be conducted, including the contribution of different types of experimental backgrounds and the accuracy of the background counting rate.

Comprehensive evaluations of a prototype full field-of-view photon counting CT system through phantom studies.

Objective. Photon counting CT (PCCT) has been a research focus in the last two decades. Recent studies and advancements have demonstrated that systems using semiconductor-based photon counting detectors (PCDs) have the potential to provide better contrast, noise and spatial resolution performance compared to conventional scintillator-based systems. With multi-energy threshold detection, PCD can simultaneously provide the photon energy measurement and enable material decomposition for spectral imaging. In this work, we report a performance evaluation of our first CdZnTe-based prototype full-size PCCT system through various phantom imaging studies.Approach.This prototype system supports a 500 mm scan field-of-view and 10 mmz-coverage at isocenter. Phantom scans were acquired using 120 kVp from 50 to 400 mAs to assess the imaging performance on: CT number accuracy, uniformity, noise, spatial resolution, material differentiation and quantification.Main results.Both qualitative and quantitative evaluations show that PCCT, under the tested conditions, has superior imaging performance with lower noise and improved spatial resolution compared to conventional energy integrating detector (EID)-CT. Using projection domain material decomposition approach with multiple energy bin measurements, PCCT virtual monoenergetic images have lower noise, and good accuracy in quantifying iodine and calcium concentrations. These results lead to increased contrast-to-noise ratio (CNR) for both high and low contrast study objects compared to EID-CT at matched dose and spatial resolution. PCCT can also generate super-high resolution images using much smaller detector pixel size than EID-CT and greatly improve image spatial resolution.Significance.Improved spatial resolution and quantification accuracy with reduced image noise of the PCCT images can potentially lead to better diagnosis at reduced radiation dose compared to conventional EID-CT. Increased CNR achieved by PCCT suggests potential reduction in iodine contrast media load, resulting in better patient safety and reduced cost.

GPU-accelerated CZT detector simulation with charge build-up effects

The simulation of semiconductor detectors is a key tool for developping and studying their behavior. In general, simulations of CZT detectors assume the crystal to be perfect, meaning that its properties are uniform. However, structural defects appearing in the crystal during growth modify these properties. Moreover, dynamic phenomena like polarization can appear. In particular, the electric field inside the detector can be disturbed by bulk charges, which creates uncertainties on measurement of incident photon energy and on interaction position estimated by sub-pixel positioning. One of the main issues of a simulation considering these non-uniformities is its complexity, especially if multiple or evolving electric field distributions have to be considered. Hence, we have developed a model accepting electric field modifications and allowing to observe quickly the detector's response modifications with the electric field. We leveraged GPU to address such computational burden. Indeed, we can afford to consider more complex simulations as the computation time is reduced. In this study, we introduced different types of spatial defects which may be found in real CZT crystals (point-like, planar, etc.) to observe quickly and easily their impact on the detector's measurement, on both spatial and spectral response.

Improving the energy resolution of photon counting microwave kinetic inductance detectors using principal component analysis

We develop a photon energy measurement scheme for single photon counting Microwave Kinetic Inductance Detectors (MKIDs) that uses principal component analysis (PCA) to measure the energy of an incident photon from the signal ("photon pulse") generated by the detector. PCA can be used to characterize a photon pulse using an arbitrarily large number of features and therefore PCA-based energy measurement does not rely on the assumption of an energy-independent pulse shape that is made in standard filtering techniques. A PCA-based method for energy measurement is especially useful in applications where the detector is operating near its saturation energy and pulse shape varies strongly with photon energy. It has been shown previously that PCA using two principal components can be used as an energy-measurement scheme. We extend upon these ideas and develop a method for measuring the energies of photons by characterizing their pulse shapes using any number of principal components and any number of calibration energies. Applying this technique with 50 principal components, we show improvements to a previously-reported energy resolution for Thermal Kinetic Inductance Detectors (TKIDs) from 75 eV to 43 eV at 5.9 keV. We also apply this technique with 50 principal components to data from an optical to near-IR MKID and achieve energy resolutions that are consistent with the best results from existing analysis techniques.

Spectral characterization of flash and high flux x-ray radiographic sources with a magnetic Compton spectrometer.

In this work, we present a new analysis method applied to revitalize permanent magnet Compton spectrometers used to measure photon energy spectra in the MeV range. The inversion of the measured electron distribution to determine the original photon distribution is achieved via a method of consistent coupled radiation transport and magnetic field mapping of the input photon spectra to the measured electron distribution. The method of linear least squares was used to perform the unfolding of the electron distribution to the initial photon spectra, without any assumptions made regarding the electron distribution. We present an application of this method to data from a nominal 19.4MeV flash radiographic source (the first axis of the Dual Axis Radiographic Hydro-Test Facility) capable of generating 500 R @ 1m in ∼60ns and a medical therapy source (a Scanditronix M22, Microtron) capable of variable energies with nominal endpoints of 6, 10, 15, and 20MeV and an output of ∼1000-2000 R/min @ 1m. The results provide agreement between the modeled and unfolded experimentally measured photon spectra as quantified by statistical tests, from 1.5 to 20MeV. Experimental results are presented as well as a discussion of the novel MCNP6-based simulations and methods for reconstruction of the spectra.

High-accuracy measurement of mass attenuation coefficients and the imaginary component of the atomic form factor of zinc from 8.51 keV to 11.59 keV, and X-ray absorption fine structure with investigation of zinc theory and nanostructure.

High-accuracy X-ray mass attenuation coefficients were measured from the first X-ray Extended Range Technique (XERT)-like experiment at the Australian Synchrotron. Experimentally measured mass attenuation coefficients deviate by ∼50% from the theoretical values near the zinc absorption edge, suggesting that improvements in theoretical tabulations of mass attenuation coefficients are required to bring them into better agreement with experiment. Using these values the imaginary component of the atomic form factor of zinc was determined for all the measured photon energies. The zinc K-edge jump ratio and jump factor are determined and results raise significant questions regarding the definitions of quantities used and best practice for background subtraction prior to X-ray absorption fine-structure (XAFS) analysis. The XAFS analysis shows excellent agreement between the measured and tabulated values and yields bond lengths and nanostructure of zinc with uncertainties of from 0.1% to0.3% or 0.003 Å to 0.008 Å. Significant variation from the reported crystal structure was observed, suggesting local dynamic motion of the standard crystal lattice. XAFS is sensitive to dynamic correlated motion and in principle is capable of observing local dynamic motion beyond the reach of conventional crystallography. These results for the zinc absorption coefficient, XAFS and structure are the most accurate structural refinements of zinc at room temperature.

Low-energy X-ray attenuation characteristics of Rhizophora spp. composites

Photon absorption parameters such as mass attenuation coefficients ( $${\mu }_{\mathrm{m}}$$ ), molar extinction coefficients ( $$\varepsilon$$ ), total molecular ( $${\sigma }_{\mathrm{t},\mathrm{m}}$$ ), atomic ( $${\sigma }_{\mathrm{t},\mathrm{a}}$$ ) and electronic ( $${\sigma }_{\mathrm{t},\mathrm{el}}$$ ) cross sections, half-value layers $$({X}_{1/2})$$ , tenth-value layers ( $${X}_{1/10}$$ ), mean free paths $$(\lambda )$$ , effective atomic numbers ( $${Z}_{\mathrm{eff}}$$ ), and effective electron densities ( $${N}_{\mathrm{el}}$$ ) were estimated for defatted soy flour (DSF), soy protein concentrate (SPC), and soy protein isolate (SPI)-based Rhizophora spp. particleboard composites substituted with 10 wt% sodium hydroxide (NaOH) and 0, 5, 10, and 15 wt% itaconic acid polyamidoamine-epichlorohydrin (IA-PAE) adhesives. Elemental composition was assessed using ultrahigh-resolution field emission scanning electron microscopy-energy dispersive X-ray spectrometry (UHR-FESEM-EDX). The interaction parameters were evaluated for $${\mathrm{K}}_{\mathrm{\alpha }1}$$ photons at 16.59, 17.46, 21.21, and 25.26 keV, employing a low-energy germanium (LEGe) detector system and an 241Am $$\gamma$$ -ray source. X-ray diffraction characterization revealed an amorphous phase in the developed particleboard composites. Samples DSF15′, SPC15′, and SPI15′ exhibited the highest values of $${\mu }_{\mathrm{m}}$$ , $$\varepsilon$$ , $${\sigma }_{\mathrm{t},\mathrm{m}}$$ , $${Z}_{\mathrm{eff}}$$ , and $${N}_{\mathrm{el}}$$ among all of the studied particleboard samples, within the range of measured photon energies. In addition, all of the modified samples exhibited lower $${X}_{1/2}$$ , $${X}_{1/10}$$ , $$\lambda$$ , $${\sigma }_{\mathrm{t},\mathrm{a}}$$ , and $${\sigma }_{\mathrm{t},\mathrm{el}}$$ than the unmodified samples, with DSF-, SPC-, and SPI/NaOH/Rhizophora spp./IA-PAE (15 wt%), indicating insignificant changes. The current results of the particleboard samples’ analysis can be useful for medical radiation applications and shielding research.

Absolute X-ray energy measurement using a high-accuracy angle encoder.

This paper presents an absolute X-ray photon energy measurement method that uses a Bond diffractometer. The proposed system enables the prompt and rapid in situ measurement of photon energies over a wide energy range. The diffractometer uses a reference silicon single-crystal plate and a highly accurate angle encoder called SelfA. The performance of the system is evaluated by repeatedly measuring the energy of the first excited state of the potassium-40 nuclide. The excitation energy is determined as 29829.39 (6) eV, and this is one order of magnitude more accurate than the previous measurement. The estimated uncertainty of the photon energy measurement was 0.7 p.p.m. as a standard deviation and the maximum observed deviation was 2 p.p.m.

MICRODOSIMETRIC UNDERSTANDING OF DOSE RESPONSE AND RELATIVE EFFICIENCY OF THERMOLUMINESCENCE DETECTORS.

LiF:Mg,Ti detectors show relative efficiency η for heavy charged particles significantly lower than one. It was for a long time not recognised that η varies also for electron energies and, as a consequence for photons. For LiF:Mg,Cu,P detectors measured photon energy response was named ‘anomalous’ because it differed significantly from the ratio of photon absorption coefficients. The decrease of η was explained as a microdosimetric effect due to local saturation of trapping centres around the electron track. For TLD-100 it was noticed by Horowitz that the measured photon energy response disagrees with the ratio of absorption coefficient by about 10%. It was demonstrated that a fraction of the TL signal in LiF:Mg,Ti is generated in the supralinear dose–response range, due to the high local doses generated by photon-induced tracks. Prediction of TL efficiency is particularly important in space dosimetry and in dosimetry of therapeutic beams like protons or carbon ions.

Ground calibration and in-orbit performance of the time-resolved soft x-ray spectrometer on board XPNAV-1

The time-resolved soft x-ray spectrometer (TSXS) aboard on the X-ray Pulsar Navigation Test Satellite is an x-ray timing spectrometer covering the energy range of 0.5 to 10 keV. It is China’s first focusing x-ray telescope launched into space orbit. The optical system of TSXS is an x-ray grazing incidence focusing system with a field of view 15 arc min, which is nested with 4 parabolic mirrors with a focal length of 1150 mm. The focal plane detector of TSXS uses a silicon drift detector. From April to June 2016, ground calibration was carried out on TSXS, including the optical axis determination, calibration of energy linearity and energy resolution, calibration of time resolution and photon arrival time accuracy, and calibration of mirrors’ reflectivity. After the launch on November 10, 2016, the in-orbit calibration and performance verification of the telescope was carried out, including the optical axis determination, the performance of energy response, the performance of time accuracy, the calibration of effective area, and the evaluation of telescope sensitivity. After calibration and verification on the ground and in orbit, the photon energy measurement error of the telescope is better than 0.5% at energies above 1.5 keV, the energy resolution is better than 156 eV at 6.4 keV, the time resolution is <1 μs, the photon arrival time measurement accuracy is <302 ns, and the telescope in-orbit background is <4.16 ± 1.42 × 10 − 3 photons / s (0.5 to 3 keV, 40°N to 40°S, not including South Atlantic Anomaly). The telescope has an in-orbit observation sensitivity of 2.09 × 10 − 3 photons / cm2 / s / keV (0.5 to 3 keV, T = 1000 s, and nσ = 5).

Constraints on cosmological parameters from gamma-ray burst peak photon energy and bolometric fluence measurements and other data

ABSTRACT We use measurements of the peak photon energy and bolometric fluence of 119 gamma-ray bursts (GRBs) extending over the redshift range of 0.3399 ≤ z ≤ 8.2 to simultaneously determine cosmological and Amati relation parameters in six different cosmological models. The resulting Amati relation parameters are almost identical in all six cosmological models, thus validating the use of the Amati relation in standardizing these GRBs. The GRB data cosmological parameter constraints are consistent with, but significantly less restrictive than, those obtained from a joint analysis of baryon acoustic oscillation and Hubble parameter measurements.

Calibration and performance of the CMS Electromagnetic Calorimeter in LHC Run-II

Many physics analyses using the Compact Muon Solenoid (CMS) detector at the LHC require accurate, high resolution electron and photon energy measurements. Excellent energy resolution is crucial for studies of Higgs boson decays with electromagnetic particles in the final state, as well as searches for very high mass resonances decaying to energetic photons or electrons. The CMS electromagnetic calorimeter (ECAL) is a fundamental instrument for these analyses and its energy resolution is crucial for the Higgs boson mass measurement. Recently the energy response of the calorimeter has been precisely calibrated exploiting the full Run-II data, aiming at a legacy reprocessing of the data. A dedicated calibration of each detector channel has been performed with physics events such as electrons from W and Z boson decays, and photons from π0/η decays. This paper presents the calibration strategies that have been implemented and the excellent performance achieved by the CMS ECAL with the ultimate calibration of Run-II data, in terms of energy scale stability and energy resolution.

Signatures of the d^{*}(2380) Hexaquark in d(γ,pn[over →]).

We report a measurement of the spin polarization of the recoiling neutron in deuterium photodisintegration, utilizing a new large acceptance polarimeter within the Crystal Ball at MAMI. The measured photon energy range of 300-700MeV provides the first measurement of recoil neutron polarization at photon energies where the quark substructure of the deuteron plays a role, thereby providing important new constraints on photodisintegration mechanisms. A very high neutron polarization in a narrow structure centered around E_{γ}∼570 MeV is observed, which is inconsistent with current theoretical predictions employing nucleon resonance degrees of freedom. A Legendre polynomial decomposition suggests this behavior could be related to the excitation of the d^{*}(2380) hexaquark.

Quantifying the Effect of Cosmic Ray Showers on the X-IFU Energy Resolution

The X-ray Integral Field Unit (X-IFU) will operate an array of more than 3000 Transition Edge Sensor pixels at 90 mK with an unprecedented energy resolution of 2.5 eV at 7 keV. In space, primary cosmic rays and secondary particles produced in the instrument structure will continuously deposit energy on the detector wafer and induce fluctuations on the pixels’ thermal bath. We have investigated through simulations of the X-IFU readout chain how these fluctuations eventually influence the energy measurement of X-ray photons. Realistic timelines of thermal bath fluctuations at different positions in the array are generated as a function of a thermal model and the expected distribution of the deposited energy of the charged particles. These are then used to model the TES response to these thermal perturbations and their influence on the onboard energy reconstruction process. Overall, we show that with adequate heatsinking, the main energy resolution degradation effect remains minimal and within the associated resolution allocation of 0.2 eV. We further study how a dedicated triggering algorithm could be put in place to flag the rarer large thermal events.

Calibration and Performance of the CMS Electromagnetic Calorimeter in LHC Run2

Many physics analyses using the Compact Muon Solenoid (CMS) detector at the LHC require accurate, high resolution electron and photon energy measurements. Excellent energy resolution is crucial for studies of Higgs boson decays with electromagnetic particles in the final state, as well as searches for very high mass resonances decaying to energetic photons or electrons. The CMS electromagnetic calorimeter (ECAL) is a fundamental instrument for these analyses and its energy resolution is crucial for the Higgs boson mass measurement. Recently the energy response of the calorimeter has been precisely calibrated exploiting the full Run2 data, aiming at a legacy reprocessing of the data. A dedicated calibration of each detector channel has been performed with physics events exploiting electrons from W and Z boson decays, photons from π0 and η decays, and from the azimuthally symmetric energy distribution of minimum bias events. This talk presents the calibration strategies that have been implemented and the excellent performance achieved by the CMS ECAL with the ultimate calibration of Run2 data, in terms of energy scale stability and energy resolution.

Performance of the CMS electromagnetic calorimeter during the LHC Run II

Many physics analyses using the Compact Muon Solenoid (CMS) detector at the LHC require accurate, high resolution electron and photon energy measurements. In particular, excellent energy resolution is crucial for studies of Higgs boson decays with electromagnetic particles in the final state, as well as searches for very high mass resonances decaying to energetic photons or electrons. Following the excellent performance achieved in Run I at center-of-mass energies of 7 and 8 TeV, the CMS electromagnetic calorimeter (ECAL) is operating at the LHC with proton-proton collisions at 13 TeV center-of-mass energy. The instantaneous luminosity delivered by the LHC during Run II has achieved unprecedented values, using 25 ns bunch spacing. High pileup levels necessitate a retuning of the ECAL readout and trigger thresholds and reconstruction algorithms, to achieve the best possible performance in these more challenging conditions. The energy response of the detector must be precisely calibrated and monitored to reach and maintain the excellent performance obtained in Run I in terms of energy scale and resolution. A dedicated calibration of each detector channel is performed with physics events exploiting electrons from W and Z boson decays, photons from π0/η decays, and from the azimuthally symmetric energy distribution of minimum bias events. This talk presents the new reconstruction algorithm and calibration strategies that were implemented to maintain the excellent performance of the CMS ECAL throughout Run II. Performance results from the Run II data taking period will be reported.

Simulation of the CMS electromagnetic calorimeter response at the energy and intensity frontier

The electromagnetic calorimeter (ECAL) of the CMS experiment at the LHC is a homogeneous calorimeter made of 75848 lead tungstate (PbWO4) scintillating crystals, designed for high precision electron and photon energy measurements in hadron collisions at the TeV scale. The detailed simulation of the calorimeter response is crucial for physics analyses involving electrons, photons, jets or missing energy. The detector simulation has been tuned during the first LHC run, including a detailed description of the upstream material. The increase of centre-of-mass energy, bunch crossing rate and instantaneous luminosity in the second run has resulted in updated and improved data readout, settings and reconstruction techniques. Furthermore, aging effects due to radiation, in particular increases in noise in the photodetectors and crystal transparency losses, have caused a change of the calorimeter response. All of these effects have been taken into account in order to improve the simulation of the calorimeter response and to ensure that it describes the data well over time, notwithstanding the evolving conditions. In 2024 the ECAL will undergo an upgrade to cope with the high luminosity phase of the LHC (HL-LHC). The temperature of the calorimeter will be lowered to mitigate the aging effects, the front-end electronics will be replaced with a faster version and the data will be read out in streaming mode towards the off-detector electronics. The fast PbWO4 response time will be exploited to measure the timing of high-energy showers with high precision. A detailed simulation description of the crystal response is fundamental for the design of the detector electronics and to predict the performance for the energy and timing measurements. The techniques employed in tuning the simulation of the detector response for the present running conditions and for the upgrade will be presented.