Photon Energy Resolution Research Articles

RF shielding materials for highly-integrated PET/MRI systems

Integration of magnetic resonance imaging (MRI) and positron emission tomography (PET) into a simultaneous device calls for adaptations of the radio frequency (RF) shielding concept. Conventional PET module housings fully encase the entire PET detector to reduce mutual interference. Excluding passive components, i.e. scintillators, from the housings, offers integration advantages, e.g. by reducing the overall housing volume or utilizing bigger scintillators. However, locating the scintillator outside of the RF shielding requires an optically transparent RF shielding interface between the scintillators and the photodetector to close the aperture. Therefore, a careful evaluation and selection of RF materials is essential to ensure an excellent PET/MRI system performance. To this end, we examined 10 materials (coated glasses, coated foils, meshes). The shielding effectiveness (SE) was evaluated at 100 and 300 MHz. PET performance was tested for single event registration and coincident events by integrating the material into the PET detector stack between the digital silicon photomultiplier photodetector array and one-to-one coupled scintillator. We determined photon attenuation (PA), energy resolution (dE/E), and coincidence resolving time (CRT) and compared to reference measurements for each material group. MRI compatibility was assessed by analyzing the material influence on the main magnetic field (B0) homogeneity. The coated glasses and foils exhibited SEs of up to 25 dB at 300 MHz. Both had a PA < 23% with dE/E and CRT comparable to the reference measurements, and no measurable impact on the B0 field was registered. The meshes exhibited higher SEs up to 56 dB, but also a PA > 58% with a higher impact on dE/E and CRT. Only one mesh affected B0 homogeneity. Overall, we recommend the coated foil HS 9400 for integration concepts as it exhibited a good performance with SE = 25 dB, PA = 22%, resulting in a PET performance of dE/E = 12% and CRT = 274 ps.

Noise processing of superconducting kinetic inductance single photon detector

Noise is one of the main factors affecting the performance index of weak signal detection devices, and the optimal filtering algorithm is an effective method to adaptively extract various useful weak signals from the white noise background. In order to improve the performance of single photon detector (especially the photon number resolution ability), one mainly focuses on the optimization of detector hardware such as the optimization of photosensitive materials and the technology of device fabrication. However, in this paper the performance of microwave kinetic Inductance detector (MKID) in the way of data processing is improved. Considering the fact that the template of light pulse signal in the optimal filtering algorithm is obtained by taking the average, we replace the noise model in the original optimal filtering algorithm with the white noise model and the whitening noise model. Then we process the photon response data that are detected by the MKID in an extremely low temperature environment. The results show that the energy resolution (one of the main performance indexes of single photon detector) of MKID is improved by about 15%, and we achieve an infrared single photon energy resolution of 0.26 eV. In this paper, the application and development trends of superconducting single photon detector are briefed. Then, how the MKID responds to weak coherent optical signal in low temperature environment, and the process of signal conversion, acquisition and output are explained in detail. According to the optimal filtering algorithm, we use different noise models to analyze the results of the signals detected by MKID. After that, we count the optimal amplitude multiple, perform the Gaussian fitting analysis on the statistical graph, and compare the energy resolution with the photon number resolution of the optimal filtering algorithm under different noise models. As a result, we find that under the white noise model, the optimal filtering algorithm is used to obtain the best result for MKID processing, and high energy resolution can be achieved.

Optimizing the performance of the CMS Electromagnetic Calorimeter to measure Higgs properties during Phase I and Phase II of the LHC

The CMS Electromagnetic Calorimeter (ECAL), is a high granularity lead tungstate (PbWO4) crystal calorimeter operating at the CERN LHC. The ECAL performance has been crucial in the discovery and subsequent characterization of the Higgs boson. The original ECAL design considerations, and the improvements to the energy reconstruction and energy calibration algorithms to cope with the LHC Run II are described. For the High-Luminosity LHC (HL-LHC) upgrades to ECAL are necessary. The crystals in the barrel region will be retained, defining the HL-LHC CMS barrel electromagnetic calorimeter ECAL. The readout electronics will be upgraded and operating at lower temperatures, to maintain the required performance of ECAL from 2027 onwards. The new readout electronics, the timing resolution and the electron and photon reconstruction efficiencies and energy resolution expected for HL-LHC are presented. The performance relevant to a number of key Higgs decay channels is reported.

Simple, high-resolution method for measurement of the natural relative energy bandwidth of Si(111) double crystal monochromators

Measurement of photon energy resolution, an important operational parameter of X-ray double-crystal monochromators (DCMs), is complicated by the coupled relationship between energy bandwidth and diffraction angle. This paper reports two methods of analyzing the natural relative energy bandwidth of DCMs at fixed photon energy. The first is based on measurement of the post-DCM beam using a monolithic double channel-cut monochromator (MDCM), while the second uses measurements of the K absorption edge of copper (Cu) in the post-DCM beam as a small vertical angular slice of the source is scanned. Both analysis methods eliminate the effects of synchrotron radiation (SR) vertical angular divergence. The natural relative energy bandwidth values for the Si(111) DCM measured by the MDCM and Cu K-edge absorption methods are 1.59×10−4 at 12.763 keV and 1.61×10−4 at 8.979 keV, respectively. This result demonstrates that the two methods offer nearly the same level of precision for determining the natural relative energy bandwidth of Si(111) DCMs. However, the Cu K-edge absorption method has the advantages of requiring simpler experimental equipment and significantly shorter data acquisition time.

Simulation of the CsI crystal calorimeter of the detector of charm-tau factory in Novosibirsk

The paper presents a current status of the simulation of the pure CsI crystal calorimeter of the detector of charm-tau factory project in Novosibirsk. The calorimeter employs the scheme with the crystals focusing at the beams interaction point to obtain the optimal energy and coordinate resolutions. We present a detailed description of the calorimeter design, optimized using the specially developed parametrized crystal geometry generator. The report also presents the results for the coordinate and energy correction functions calculation. After application of these corrections the estimation of the photon energy and coordinate resolutions for the ideal conditions of negligibly small stochastic, electronic and pileup noises was performed. The π0 reconstruction efficiency and mass resolution depending on it's momentum were also determined.

Physics object performance of the FCC-hh calorimeter system

The feasibility of a future proton-proton collider (FCC-hh) has been outined in Conceptual Design Reports published early 2019. FCC-hh would deliver collisions at a center of mass energy up to 100 TeV and unprecedented instantaneous luminosity (L=3 × 1034), resulting in extremely challenging radiation conditions up to a maximum of 5× 1018 neq/cm2 and a dose up to 5 GGy in the forward calorimeters (up to |η|=6) and up to 1000 simultaneous proton-proton interactions per bunch-crossing. By delivering an integrated luminosity of few tens of ab−1, the FCC-hh would provide an unrivalled discovery potential for new physics. Requiring high sensitivity for resonant searches at masses up to tens of TeV imposes strong constraints on the design of the calorimeters. Resonant searches in final states containing jets, taus and electrons require both excellent energy resolution at multi-TeV energies as well as outstanding ability to resolve highly collimated decay products resulting from extreme boosts. In addition, the FCC-hh provides the unique opportunity to precisely measure the Higgs self-coupling in the di-photon and b-jets channel. Excellent photon and jet energy resolution at low energies as well as excellent angular resolution for pion background rejection are required in this challenging environment. In this talk we will briefly review the electromagnetic and hadronic calorimeter current design and requirements (granularity, energy resolution, acceptance, …) and discuss the expected performance of the physics objects based on calorimeter reconstruction. We will then examine the impact of the object performance on the final sensitivity of the relevant benchmark physics analyses.

Development of an Optical Transition-Edge Sensor Array

Transition-edge sensors (TESs) exhibiting high energy resolution for single optical photons have been applied to photon-counting microscopy for biological imaging. This paper discusses the development of TES arrays with large effective areas to expand the field of view of photon-counting microscopy and has fabricated an optical TES array comprising a Ti/Au bilayer on a Si substrate. Thermal interference due to Joule power did not affect the time constant and energy resolution of a detector in the TES array, even though the Joule power in the detector was changed by 23%. The photon signal crosstalk between adjacent detectors was − 40 dB which was negligible. Heat conduction through the Si substrate was dominant in the photon signal crosstalk between adjacent detectors.

TES Microcalorimeters for PTOLEMY

The PTOLEMY project is devoted to directly detect the cosmic neutrino background. A key point for the project success is the development of a device which is capable of detecting electrons with an energy resolution lower than 0.05 eV. Microcalorimeters based on transition-edge sensors are among the best candidates since they already reach 0.11 eV of energy resolution for telecomm photons. To further improve the energy resolution, while maintaining a suitable saturation energy, it is necessary to reduce the transition temperature. This could be achieved by proximity effect of a normal-superconducting bilayer. To this aim, TiAu very thin films are under development to demonstrate the feasibility of reaching 0.05 eV energy resolution for light pulses of few eV. Thanks to the high electron stopping power of metals, the penetration depth of low energy incident electrons is limited to few nanometers and, with respect to visible light, we expect a high detection efficiency, while keeping similar dark counts and energy resolution.

Resummed photon spectrum from dark matter annihilation for intermediate and narrow energy resolution

The annihilation cross section of weakly interacting TeV scale dark matter particles χ0 into photons is affected by large quantum corrections due to electroweak Sudakov logarithms and the Sommerfeld effect. We extend our previous work on the resummation of the semi-inclusive photon energy spectrum in χ0χ0 → γ + X in the vicinity of the maximal photon energy Eγ = mχ with NLL’ accuracy from the case of narrow photon energy resolution {E}_{mathrm{res}}^{gamma } of order {m}_W^2/{m}_{chi } to intermediate resolution of order {E}_{mathrm{res}}^{gamma}sim {m}_W . We also provide details on the previous narrow resolution calculation. The two calculations, performed in different effective field theory set-ups for the wino dark matter model, are then shown to match well, providing an accurate representation up to energy resolutions of about 300 GeV.

Absolute single photoionization cross-sections of Br3+: experiment and theory

Absolute single photoionization cross section measurements for Br3+ ions are reported in the photon energy range 44.79–59.54 eV at a photon energy resolution of 21 ± 3 meV. Measurements were performed at the Advanced Light Source at Lawrence Berkeley National Laboratory using the merged-beams technique. Numerous resonance features in the experimental spectrum are assigned and their energies and quantum defect values are tabulated. The cross-section measurements are also compared with Breit–Pauli R-matrix calculations with suitable agreement over the photon energy range investigated. Analysis of the measured spectrum including Rydberg resonance series identifications produced a new emperical determination of the ionizational potential of Br3+ of 46.977 ± 0.050 eV, which is 805 meV lower than the most recently published value of 47.782 eV. This disparity between our determination and the earlier published value is similar to an 843 meV shift in the accepted ionization potential published for iso-electronic Se2+ as part of this same research program.

Upgrade of SLRI BL8 beamline for XAFS spectroscopy in a photon energy range of 1–13 keV

Beamline 8 is a bending magnet beamline at Synchrotron Light Research Institute (SLRI) in Thailand and has been opened for synchrotron users to perform X-ray absorption fine structure (XAFS) spectroscopy since 2006. The beamline was originally equipped with a double crystal monochromator (DCM) using a vertical entrance slit in order to limit divergence of a white beam, thus optimizing photon energy resolution at a cost of photon flux. In 2016 the beamline was upgraded with a vertical collimating mirror to decrease beam divergence. The maximum photon flux is consequently increased to 3 × 1011 photons s−1 (100 mA)−1 at the phosphorus K-edge (2145.5 eV). This enhances beamline utilization for phosphorus speciation and analysis of local atomic structures in diluted samples (>50 mg/kg of phosphorus). Furthermore, the highest photon energy of the beamline has been extended from 10 keV to 13 keV, enabling several heavy elements such as lead to be studied while the lowest photon energy currently covers the sodium K-edge. To demonstrate improved XAFS performance, XAFS experiments were carried out on selected samples (NaCl, Na3PO4·12H2O, PbO, PbO4, PbCO3, PbS, soil, and historical paint); quality of the experimental spectra was evaluated in terms of signal-to-noise ratio and appearance of XAFS characteristic features.

Cms Ecal Daq Monitoring System

The Large Hadron Collider (LHC) at CERN in Geneva, Switzerland, has just completed the Run 2 era, colliding protons at a center-of-mass energy of 13 TeV at high instantaneous luminosity. The Compact Muon Solenoid (CMS) is a general-purpose particle detector experiment at the LHC. The CMS electromagnetic calorimeter (ECAL) has been designed to achieve excellent energy and position resolution for electrons and photons. A multi-machine distributed software configures the on-detector and off-detector electronic boards composing the ECAL data acquisition (DAQ) system and follows the life cycle of the acquisition process. Since the beginning of Run 2 in 2015, many improvements to the ECAL DAQ have been implemented to reduce and mitigate occasional errors in the front-end electronics and not only. Efforts at the software level have been made to introduce automatic recovery in case of errors. Automatic actions has made even more important the online monitoring of the DAQ boards status. For this purpose a new web application, EcalView, has been developed. It runs on a light Node.js JavaScript server framework. It is composed of several routines that cyclically collect the status of the electronics. It display the information when web requests are launched by client side graphical interfaces. For each board, detailed information can be loaded and presented in specific pages if requested by the expert. Server side routines store information regarding electronics errors in a SQLite database in order to perform offline analysis about the long term status of the boards.

Physics requirements for the FCC-hh calorimeter system

The future proton-proton collider (FCC-hh) will deliver collisions at a center of mass energies up to √s = 100 TeV at an unprecedented instantaneous luminosity of L = 3 1035cm−2s−1, resulting in extremely challenging radiation conditions up to a maximum of 5 1018cm2MeV neutron equivalent fluence and dose up to 5 GGy in the forward calorimeters (up to |η| = 6) and up to 1000 simultaneous proton-proton interactions per bunch-crossing. By delivering an integrated luminosity of few tens of ab−1, the FCC-hh will provide an unrivalled discovery potential for new physics. Requiring high sensitivity for resonant searches at masses up to tens of TeV imposes strong constraints on the design of the calorimeters. Resonant searches in final states containing jets, taus and electrons require both excellent energy resolution at multi-TeV energies as well as outstanding ability to resolve highly collimated decay products resulting from extreme boosts. In addition, the FCC-hh provides the unique opportunity to precisely measure the Higgs self-coupling in the di-photon and b-jets channel. Excellent photon and jet energy resolution at low energies as well as excellent angular resolution for pion background rejection are required in this challenging environment.

Energetic γ-rays from TeV scale dark matter annihilation resummed

The annihilation cross section of TeV scale dark matter particles χ0 with electroweak charges into photons is affected by large quantum corrections due to Sudakov logarithms and the Sommerfeld effect. We calculate the semi-inclusive photon energy spectrum in χ0χ0→γ+X in the vicinity of the maximal photon energy Eγ=mχ with NLL' accuracy in an all-order summation of the electroweak perturbative expansion adopting the pure wino model. This results in the most precise theoretical prediction of the annihilation rate for γ-ray telescopes with photon energy resolution of parametric order mW2/mχ for photons with TeV energies.

A computational tool for simulation and design of tangential multi-energy soft x-ray pin-hole cameras for tokamak plasmas.

A new tool has been developed to calculate the spectral, spatial, and temporal responses of multi-energy soft x-ray (ME-SXR) pinhole cameras for arbitrary plasma densities (n e,D), temperature (T e), and impurity densities (n Z). ME-SXR imaging provides a unique opportunity for obtaining important plasma properties (e.g., T e, n Z, and Z eff) by measuring both continuum and line emission in multiple energy ranges. This technique employs a pixelated x-ray detector in which the lower energy threshold for photon detection can be adjusted independently. Simulations assuming a tangential geometry and DIII-D-like plasmas (e.g., n e,0 ≈ 8 × 1019 m-3 and T e,0 ≈ 2.8 keV) for various impurity (e.g., C, O, Ar, Ni, and Mo) density profiles have been performed. The computed brightnesses range from few 102 counts pixel-1 ms-1 depending on the cut-off energy thresholds, while the maximum allowable count rate is 104 counts pixel-1 ms-1. The typical spatial resolution in the mid-plane is ≈0.5 cm with a photon-energy resolution of 500 eV at a 500 Hz frame rate.

THz absorption spectrum employed for characterize the mixed Gallium selenide-Tin disulfide saturable absorber and its application for passively Q-switched solid state laser

Due to the ultra-short recovery time and the wider absorption range, graphene-like 2D material have been widely employed as saturable absorbers (SAs) in passively Q-switched and mode-locked lasers. Due to the low photon energy, noninvasive and high resolution, THz wave was widely used to characterize samples. In this paper, the nonlinear saturable absorption property and THz absorption spectrum of Gallium selenide/Tin disulfide (GaSe/SnS2) is reported. Passively Q-switched Nd:GdTaO4 laser with GaSe/SnS2 SA is demonstrated. The maximum output power of 551 mW under the pump power of 5 W. The minimum pulse width is 365 ns at the pulse repetition rate of 89 kHz. Our results indicate that GaSe/SnS2 nanosheets could be used in Q-switched lasers. The GaSe/SnS2 SA with good nonlinear absorption properties and easy fabricating process will promote the ultrafast photonics applications in solid state lasers.

Validation of a NaI(Tl) and LaBr3(Ce) detector's models via measurements and Monte Carlo simulations

This work relates to the study and characterization of the response function of two scintillation detectors with similar size: 2″×2″ NaI(Tl) and 2″×2″ LaBr3(Ce). The photon detection efficiency and energy resolution curve were measured for the NaI(Tl) detector in the gamma energy range from 60 keV to 1408 keV. A precise mathematical model of the two scintillators was developed using the Monte Carlo simulation code MCNP. Comparison of the efficiency data with MCNP simulations showed good agreement enabling the validation of the computational models for both NaI(Tl) and LaBr3(Ce) detectors.

The Experiment Research of Continuous-Wave Terahertz Imaging System

Terahertz wave has attracted wide attention for its great transparency, low photon energy and high imaging resolution. Experiments were performed to explore the basic application of continuous terahertz wave. Some articles for daily use were chosen and sealed as samples and detected by the continuous-wave terahertz imaging system. Then a foam specimen was made with inclusions placed in it and detected by the system. The experimental results demonstrate that the system can detect and image the shapes and locations of the samples and inclusions correctly, though the air hole defect in the foam specimen is difficult to identify. The different colors indicating the strength of the reflected signal help to distinguish the different materials. The work paves the way for our future research and application of continuous terahertz wave.

Dispersion of the resonant second order nonlinearity in 2D semiconductors probed by femtosecond continuum pulses

We demonstrate an effective microspectroscopy technique by tracing the dispersion of second order nonlinear susceptibility (χ(2)) in a monolayer tungsten diselenide (WSe2). The χ(2) dispersion obtained with better than 3 meV photon energy resolution showed peak value being within 6.3-8.4×10-19 m2/V range. We estimate the fundamental bandgap to be at 2.2 eV. Sub-structure in the χ(2) dispersion reveals a contribution to the nonlinearity due to exciton transitions with exciton binding energy estimated to be at 0.7 eV.

Optimization of a large-area detector-block based on SiPM and pixelated LYSO crystal arrays

We present the performance evaluation of a large-area detector module based on the ArrayC-60035-64P, an 8×8 array of tileable, 7.2mm pitch, silicon photomultipliers (SiPM) by SensL, covering a total area of 57.4mm×57.4mm. We characterized the ArrayC-60035-64P, operating at room temperature, using LYSO pixelated crystal arrays of different pitch sizes (1.075, 1.430, 1.683, 2.080 and 2.280mm) to determine the resolvable crystal size. After an optimization process, a 7mm thick coupling light guide was used for all crystal pitches. To identify the interaction position a 16-channel (8 columns, 8 rows) symmetric charge division (SCD) readout board together with a center-of-gravity algorithm was used. Based on this, we assembled the detector modules using a 40×40 LYSO, 1.43mm pitch array, covering the total detector area. Calibration was performed using a 137Cs source resulting in excellent crystal maps with minor geometric distortion, a mean 4.1 peak-to-valley ratio and 9.6% mean energy resolution for 662keV photons in the central region. The resolvability index was calculated in the x and y directions with values under 0.42 in all cases. We show that these large area SiPM arrays, combined with a 16-channel SCD readout board, can offer high spatial resolution, without processing a big number of signals, attaining excellent energy resolution and detector uniformity.