Bromide Scintillators Research Articles

Hybrid Eu(II)-bromide scintillators with efficient 5d-4f bandgap transition for X-ray imaging

Luminescent metal halides are attracting growing attention as scintillators for X-ray imaging in safety inspection, medical diagnosis, etc. Here we present brand-new hybrid Eu(II)-bromide scintillators, 1D type [Et4N]EuBr3·MeOH and 0D type [Me4N]6Eu5Br16·MeOH, with spin-allowed 5d-4f bandgap transition emission toward simplified carrier transport during scintillation process. The 1D/0D structures with edge/face -sharing [EuBr6]4− octahedra further contribute to lowing bandgaps and enhancing quantum confinement effect, enabling efficient scintillation performance (light yield ~73100 ± 800 Ph MeV−1, detect limit ~18.6 nGy s−1, X-ray afterglow ~ 1% @ 9.6 μs). We demonstrate the X-ray imaging with 27.3 lp mm−1 resolution by embedding Eu(II)-based scintillators into AAO film. Our results create the new family of low-dimensional rare-earth-based halides for scintillation and related optoelectronic applications.

Discerning β-emitting radioactivity from caesium-137 γ radiation via bremsstrahlung for in-situ groundwater monitoring

A qualitative approach to discern the relative contributions of 137Cs and 90Sr in-solution with a monitoring probe is described, based on a comparison of X- and γ-ray photon spectra. The bremsstrahlung yield from 90Sr has been measured as a function of distance (x) from a cerium bromide scintillation detector relative to the 137Cs γ-ray full-energy peak response. The utility of two, count-independent shape factor parameters has been compared: the ratio of the sum of the counts in the 60–800 keV region to the full-energy peak response associated with the 137Cs 662 keV γ-ray line, termed for the benefit of this paper as SF1, and the ratio of counts in the 60–350 keV region to those in the 350–450 keV region, defined in this work as SF2. These parameters probe the presence of isotopes associated with clear full-energy spectral lines and bremsstrahlung, respectively. They have been calibrated as a function of x with sealed sources in the laboratory and both are observed to be asymptotic as x→0. This approach has been tested with a variety of open, laboratory-based liquid samples comprising 90Sr and 137Cs, and in a water-based, contaminated medium in the field associated with a sump at a low-level waste disposal facility on the former fast reactor site at Dounreay, UK. The highest response in both SF1 and SF2 measured in this work is observed in these on-site measurements, consistent with x→0, implying both 90Sr and 137Cs presenting together in solution. This is consistent with prior, laboratory-based analysis of the sump media, and suggests that the β−-emitter contribution (anticipated to comprise 90Sr and 90Y) is very near the probe, consistent with the solution being in contact with it. This is of relevance where the β−/γ composition of contaminated groundwater, in-situ, is not well understood or where migratory changes in activity are suspected.

Self-calibration method for LaBr3 coupled with SiPM detector based on internal radiation of 138La

Gamma detectors consisting of lanthanum bromide (LaBr3) scintillator and silicon photomultiplier (SiPM) have extensive applications in various scientific fields. Accurate gamma energy measurement depends on accurate calibration of these detectors. While some studies have attempted detector self-calibration based on the natural background of LaBr3, these methods are limited to specific LaBr3 crystals and lack generality. To address this limitation, this paper proposes a self-calibration method that solely utilizes the natural radioactivity of 138La. By solving for the maximum similarity between the test background from measurement and the standard spectrum obtained from the Geant4 simulation, the detector is effectively calibrated. Furthermore, the application of a series of energy spectrum processing algorithms simplifies the solution complexity of the maximum similarity problem. Experimental results from four different crystals at varying temperatures demonstrate calibration errors of less than 0.8% at 662 keV, highlighting the method's broad applicability and accuracy. Besides, the influence of the background measurement time and the natural environmental background on the self-calibration method are discussed in detail, further illustrating the value of the application.

Gamma-ray sources imaging and test-beam results with MACACO III Compton camera

Hadron therapy is a radiotherapy modality which offers a precise energy deposition to the tumors and a dose reduction to healthy tissue as compared to conventional methods. However, methods for real-time monitoring are required to ensure that the radiation dose is deposited on the target. The IRIS group of IFIC-Valencia developed a Compton camera prototype for this purpose, intending to image the Prompt Gammas emitted by the tissue during irradiation. The system detectors are composed of Lanthanum (III) bromide scintillator crystals coupled to silicon photomultipliers. After an initial characterization in the laboratory, in order to assess the system capabilities for future experiments in proton therapy centers, different tests were carried out in two facilities: PARTREC (Groningen, The Netherlands) and the CNA cyclotron (Sevilla, Spain). Characterization studies performed at PARTREC indicated that the detectors linearity was improved with respect to the previous version and an energy resolution of 5.2 % FWHM at 511 keV was achieved. Moreover, the imaging capabilities of the system were evaluated with a line source of 68Ge and a point-like source of 241Am-9Be. Images at 4.439 MeV were obtained from irradiation of a graphite target with an 18 MeV proton beam at CNA, to perform a study of the system potential to detect shifts at different intensities. In this sense, the system was able to distinguish 1 mm variations in the target position at different beam current intensities for measurement times of 1800 and 600 s.

Evaluation of full-energy-peak efficiencies for a LaBr3:Ce scintillator through a Virtual Point Detector approach

The aim of this work is to investigate, in a wide range of gamma-ray energies, the validity of the “Virtual Point Detector” (VPD) approach to evaluate Full-Energy-Peak Efficiency (FEPE) values for a Cerium-doped Lanthanum Bromide scintillator (LaBr3:Ce). With VPD approximation, the detector is assumed equivalent to a virtual point inside the crystal where all the interactions can be considered to occur. The distance of VPD from detector cap is evaluated through experimental point source measurements. The knowledge of the trend of VPD depth as a function of gamma radiation energy allows the evaluation of FEPE values starting from an experimental reference value.The validation of the procedure has been performed by applying the VPD approach to measurement geometries already characterized such as a disk source, an Havar foil irradiated inside a target of a medical cyclotron, and a parallelepided sample geometry, an atmospheric particulate paper filter reduced to 6 cm × 6 cm × 0.7 cm dimensions. FEPE values determined by VPD approach lead to radionuclide activities very close to the ones already obtained with measurements carried out with other detectors.

Non-proportionality of Light Yield of CeBr3 Scintillator

Cerium bromide (CeBr3) scintillation crystal were studied and analyzed from the photon and electron response measurements. For photon response measurements, the radioactive source has been used for the energy range of 0.356 MeV ≤ E ≤ 1.332 MeV. The 137Cs source irradiated with gamma ray energy at 0.662 MeV was used for the electron response measurement using Compton coincidence technique. The variable angles (θ) would generate the gamma energies corresponding to a scattering angle of 30° to 120°. The results of number of photoelectron (Nphe) show responds to linear trends for photon and electron response. The light yield shows increase with increasing the photon and electron energy. The results showed the non-proportionality of photon response and electron response demonstrated good proportional properties of all energy ranges and as the result, the crystal is a promising candidate for gamma or X-rays detection.

A2Bn-1PbnI3n+1 (A = BA, PEA; B = MA; n = 1, 2): Engineering Quantum-Well Crystals for High Mass Density and Fast Scintillators.

Quantum-well (QW) hybrid organic-inorganic perovskite (HOIP) crystals, e.g., A2PbX4 (A = BA, PEA; X = Br, I), demonstrated significant potentials as scintillating materials for wide energy radiation detection compared to their individual three-dimensional (3D) counterparts, e.g., BPbX3 (B = MA). Inserting 3D into QW structures resulted in new structures, namely A2BPb2X7 perovskite crystals, and they may have promising optical and scintillation properties toward higher mass density and fast timing scintillators. In this article, we investigate the crystal structure as well as optical and scintillation properties of iodide-based QW HOIP crystals, A2PbI4 and A2MAPb2I7. A2PbI4 crystals exhibit green and red emission with the fastest PL decay time <1 ns, while A2MAPb2I7 crystals exhibit a high mass density of >3.0 g/cm3 and tunable smaller bandgaps <2.1 eV resulting from quantum and dielectric confinement. We observe that A2PbI4 and PEA2MAPb2I7 show emission under X- and γ-ray excitations. We further observe that some QW HOIP iodide scintillators exhibit shorter radiation absorption lengths (∼3 cm at 511 keV) and faster scintillation decay time components (∼0.5 ns) compared to those of QW HOIP bromide scintillators. Finally, we investigate the light yields of iodide-based QW HOIP crystals at 10 K (∼10 photons/keV), while at room temperature they still show pulse height spectra with light yields between 1 and 2 photons/keV, which is still >5 times lower than those for bromides. The lower light yields can be the drawbacks of iodide-based QW HOIP scintillators, but the promising high mass density and decay time results of our study can provide the right pathway for further improvements toward fast-timing applications.

System characterization and performance studies with MACACO III Compton camera

The IRIS group of IFIC-Valencia has developed a Compton camera prototype. The system detectors are made of Lanthanum (III) bromide scintillator crystals coupled to silicon photomultipliers. Two models of silicon photomultipliers arrays with different micro pixel pitch (25 and 50 μm) have been chosen as possible candidates to improve the response of the new system. Characterization studies with a 22Na point-like source have indicated that the 25 μm photodetector provided better performance in terms of energy resolution (5.2% FWHM at 511 keV) and angular resolution (6.9∘ FWHM at 1275 keV), and more stability with temperature variations. In addition, MACACO III imaging capabilities have been assessed using a structure composed of thirty-seven 22Na point-like sources. Furthermore, in order to evaluate possible ways of improving the system performance, several studies have been carried out by means of simulations both in realistic and performance improved conditions. In this work, the system performance is evaluated for its future application in different areas.

Detailed analysis of a previously uninvestigated feature in lanthanum bromide scintillation crystals intrinsic background

Lanthanum halide scintillation crystals represent the state of the art of the scintillators technology for gamma ray spectroscopy. They feature a short decaying time ( < 30 ns), high light yield, good detection efficiency and an optimal energy resolution ( < 2.9% at 662 keV). Lanthanum halides also present an intense intrinsic background caused by the radioactive decay of 138 La and 227 Ac contaminations, which cover all the lower energies up to 3 MeV. Despite being a limitation in low counting rate experiments, this intrinsic background can be exploited to perform energy calibration of the pulse height spectra, refraining from the employment of dedicated external sources. The intense electron capture peak of 138 La at 1471 keV, which is the most relevant feature for this purpose, has been deeply characterised in literature in many aspects. In this work, a detailed analysis of the lanthanum bromide intrinsic background was performed on several scintillation crystals, unveiling a feature with an average energy of 1515 keV not yet described in the current literature.

The Mu2e experiment — Searching for charged lepton flavor violation

The Mu2e experiment will search for a Standard Model violating rate of neutrinoless conversion of a muon into an electron in the presence of an aluminum nucleus. Observation of this charged lepton flavor violating process would be an unambiguous sign of new physics. Mu2e will improve upon previous searches for this process by four orders of magnitude. This requires the world’s highest-intensity muon beam, a detector system capable of efficiently reconstructing the 105 MeV/c conversion electron signal, and minimizing sensitivity to background events. A pulsed 8 GeV proton beam strikes a target, producing pions that decay into muons. Beam outside the pulse must be suppressed to <10−10 to reduce beam-related backgrounds. The muon beam is guided from the production target along the transport system and onto the aluminum stopping target. Conversion electrons leave the stopping target and propagate inside a solenoidal magnetic field to the tracker and electromagnetic calorimeter. The tracker is a system of straw tube panels filled with Ar/CO2 at 1 atm that tracks particles inside of a solenoidal B-field and measures their momenta with ∼100 keV/c resolution to resolve signal events from decay-in-orbit backgrounds. The CsI calorimeter provides E/p and is used to seed the track reconstruction algorithm with σE/E∼10% and σt<500ps. Additionally, a novel cosmic ray veto with greater than 99.99% efficiency brings the expected number of background events to fewer than one over three years of running. To normalize the experiment, the stopping target monitor measures the rate of capture photons from muons incident on the stopping target by using a system of high-purity germanium and lanthanum bromide scintillators.

Electron non-linear light yield of LaBr[formula omitted] detector aboard GECAM

Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) is mainly designed to detect Gamma-Ray Bursts associated with gravitational wave events. The lanthanum bromide (LaBr3) scintillator with two types of doping (5% Ce3+ only, 5% Ce3+ co-doped with 1.5% Sr2+) are used in the Gamma-Ray Detectors (GRDs) of GECAM. Here, by analyzing the on-ground calibration data, we find different characteristics of these two doping types of LaBr3 scintillator, including the Energy-Channel (E-C) relation, photon non-proportional response, energy resolution, as well as the electron non-proportional response which is derived from photon response and Monte Carlo simulation with Bayesian inference method. The results also show that the photon scintillation light yield and energy resolution can be improved by co-doping Sr2+ in LaBr3:Ce3+ scintillator, owing to a direct inhibitory effect on the electron non-proportional response. By taking the electron non-proportional response into account, we find that the simulated spectrum is in good agreement with the measured one, including Compton structure, escape peak of Lanthanum and Bromine as well as full energy peak, indicating that the electron non-proportional response is an essential factor in the energy response of scintillator detector thus should be considered in the data analysis.

A compact instrument for gamma-ray burst detection on a CubeSat platform II

The Gamma-ray Module, GMOD, is a miniaturised novel gamma-ray detector which will be the primary scientific payload on the Educational Irish Research Satellite (EIRSAT-1) 2U CubeSat mission. GMOD comprises a compact (25 mm times 25 mm times 40 mm) cerium bromide scintillator coupled to a tiled array of 4 times 4 silicon photomultipliers, with front-end readout provided by the IDE3380 SIPHRA. This paper presents the detailed GMOD design and the accommodation of the instrument within the restrictive CubeSat form factor. The electronic and mechanical interfaces are compatible with many off-the-shelf CubeSat systems and structures. The energy response of the GMOD engineering qualification model has been determined using radioactive sources, and an energy resolution of 5.4% at 662 keV has been measured. EIRSAT-1 will perform on-board processing of GMOD data. Trigger results, including light-curves and spectra, will be incorporated into the spacecraft beacon and transmitted continuously. Inexpensive hardware can be used to decode the beacon signal, making the data accessible to a wide community. GMOD will have scientific capability for the detection of gamma-ray bursts, in addition to the educational and technology demonstration goals of the EIRSAT-1 mission. The detailed design and measurements to date demonstrate the capability of GMOD in low Earth orbit, the scalability of the design for larger CubeSats and as an element of future large gamma-ray missions.

Analog front-end for FPGA-based readout electronics for scintillation detectors

A new pulse-processing electronics architecture for photomultipliers coupled to fast scintillators used in nuclear physics experiments is described. The system comprises a field programmable gate array (FPGA) based time-to-digital converter (TDC), as well as custom analog electronics for amplification and efficient analog signal processing. These electronics include separate fast and slow discrete amplifiers to extract the timing and energy information of the incident radiation on cerium doped lanthanum bromide scintillators. With the slow amplifier, a novel circuit that is able to convert energy information directly into pulse width with a linear dependence is introduced. Advanced and highly demanded features such as low-processing time, high data rate handling capabilities and long collection windows have been tested with radioactive ion-beams. These characteristics of pulse-processing modules will further push the boundaries of experimental freedom.

Investigation into activation of accelerators at various synchrotron radiation facilities in Japan

ABSTRACT To establish systematic guidelines for accelerator decommissioning, a large-scale activation survey was conducted at representative synchrotron radiation facilities in Japan. The neutron flux during accelerator operation was measured with various dosimeters. A Monte Carlo simulation was conducted for some facilities to verify the special neutron distribution and their spectra. Beam loss points, reflected as high-dose-rate areas, were identified by a whole-beamline survey with a survey meter, and the generated radionuclides and their activity were determined with a lanthanum bromide (LaBr3) scintillation spectrometer. In all facilities, the activation level was quite low. Whole-beamline tunnels made of concrete were not activated, and no radionuclides were detected except for natural nuclides. In addition, almost all beamline components were either not or minimally activated. Although the acceleration energy is very high for radiation synchrotron facilities, the generation of radioactive waste would be very low.

A compact instrument for gamma-ray burst detection on a CubeSat platform I

The Educational Irish Research Satellite 1 (EIRSAT-1) is a 2U CubeSat being developed under ESA’s Fly Your Satellite! programme. The project has many aspects, which are primarily educational, but also include space qualification of new detector technologies for gamma-ray astronomy and the detection of gamma-ray bursts (GRBs). The Gamma-ray Module (GMOD), the main mission payload, is a small gamma-ray spectrometer comprising a 25 mm × 25 mm × 40 mm cerium bromide scintillator coupled to an array of 16 silicon photomultipliers. The readout is provided by IDE3380 (SIPHRA), a low-power and radiation tolerant readout ASIC. GMOD will detect gamma-rays and measure their energies in a range from tens of keV to a few MeV. Monte Carlo simulations were performed using the Medium Energy Gamma-ray Astronomy Library to evaluate GMOD’s capability for the detection of GRBs in low Earth orbit. The simulations used a detailed mass model of the full spacecraft derived from a very high-fidelity 3D CAD model. The sky-average effective area of GMOD on board EIRSAT-1 was found to be 10 cm2 at 120 keV. The instrument is expected to detect between 11 and 14 GRBs, at a significance greater than 10σ (and up to 32 at 5σ), during a nominal one-year mission. The shape of the scintillator in GMOD results in omni-directional sensitivity which allows for a nearly all-sky field of view.

Miniaturized USB-powered multi-channel module for gamma spectroscopy and imaging

LAILA is a miniaturized eight-channel electronic readout system for compact γ-ray detectors, combining high-resolution spectroscopy capability with position sensitivity. Compactness is achieved by the combination of a novel CMOS front-end ASIC (Application-Specific Integrated Circuit) for analog processing of a large signal current from Silicon PhotoMultiplier (SiPM) solid-state photodetectors, with a microcontroller-based data acquisition system. The adoption of automatic gain regulation in the gated-integrator stage of the ASIC offers an 84 dB dynamic range, combining single-photon sensitivity with an extended input photon energy range (20 keV-4MeV, using 30 μm-cell SiPMs). Using this module with properly merged 144 SiPM pixels coupled to a 3 in.-thick lanthanum bromide scintillation crystal, a 3% energy resolution at 662 keV and 1cm spatial resolution in the estimation of the interaction coordinates are experimentally demonstrated in this work.

The measurement method of gamma ray air absorbed dose rate based on LaBr 3 (Ce) detector

Objective Based on the lanthanum bromide scintillator detector, the calculation method of G( E) function was developed to measure the air absorbed dose rate. Methods Firstly, the gamma energy spectrumof the lanthanum bromide detector were simulated and the response functions with different energies were determined with Monte Carlo simulation method. Then, the G( E) function was calculated by the least square method. Finally, the air absorbed dose rate measured by the lanthanum bromide detector using G( E) function conversion method was compared with the theoretical calculation value based on the point source experiments. Results The experimental verification results showed that the relative deviation between thecalculated value with G( E) function and the theoretical calculation value wasmostly controlled within ± 6%, which verified the accuracy of G( E) function. Conclusion The results showed that the method of G( E) function could be applied to calculate the gamma radiation dose rate based on the in-situ the gamma spectrum with LaBr 3 detector. 摘要： 目的 针对溴化镧闪烁体探测器, 开展了 G( E) 函数的计算方法研宄, 最终实现了空气吸收剂量率的测量。 方法 首先, 基于蒙特卡罗模拟计算方法, 模拟计算出溴化镧探测器的 γ 能谱, 给出不同能量的响应函数;然后, 利用 最小二乘法计算得到了 G( E) 函数;最后, 利用标准点源实验, 将溴化镧探测器利用 G( E) 函数转换测量得到的空气吸 收剂量率与理论计算值进行了比较。 结果 实验验证结果表明, 基于 G( E) 函数得到的空气吸收剂量率与理论计算值 的相对偏差控制在 ± 6% 以内, 验证了 G( E) 函数的准确性。 结论 基于 γ 谱-剂量转换方法, 就地 γ 谱仪可应用于辐射 剂量的测量。

First in-core gamma spectroscopy experiments in a zero power reactor

Gamma rays in nuclear reactors, arising either from nuclear reactions or decay processes, significantly contribute to the heating and dose of the reactor components. Zero power research reactors offer the possibility to measure gamma rays in a purely neutronic environment, allowing for validation experiments of dose estimates, computed spectra, and prompt to delayed gamma ratios. The resulting data can contribute to models, code validation and photo atomic/nuclear data evaluation. To date, most experiments have relied on flux measurements using TLDs, ionization chambers, or spectrometers set in low flux areas. The CROCUS reactor allows for flexible detector placement in and around the core, and has recently been outfitted with gamma detection capabilities to fulfill the need for in-core gamma spectroscopy, as opposed to flux. In this paper we report on the experiments and accompanying simulations of gamma spectrum measurements inside a zero power reactor core, CROCUS. It is a two-zone, uranium-fueled light water moderated facility operated by the Laboratory for Reactor Physics and Systems Behaviour (LRS) at the Swiss Federal Institute of Technology Lausanne (EPFL). Herein we also introduce, in detail, the new LEAF system: A Large Energy-resolving detection Array for Fission gammas. It consists of an array of four detectors – two large ø 127 254 mm Bismuth Germanate (BGO) and two smaller ø 12 50 mm Cerium Bromide (CeBr3) scintillators. We describe the calibration and characterization of LEAF followed by first in-core measurements of gamma ray spectra in a zero power reactor at different sub-critical and critical states, and different locations. The spectra are then compared to code results, namely MCNP6.2 pulse height tallies. We were able to distinguish prompt processes and delayed peaks from decay databases. We present thus experimental data from hitherto inaccessible core regions. We provide the data as validation means for codes that attempt to model these processes for energies up to 10 MeV. We finally draw conclusions and discuss the future uses of LEAF. The results indicate the possibility of isotope tracking and burn-up validation.

A proof-of-concept study of an in-situ partial-ring time-of-flight PET scanner for proton beam verification.

Development of a PET system capable of in-situ imaging requires a design that can accommodate the proton treatment beam nozzle. Among the several PET instrumentation approaches developed thus far, the dual-panel PET scanner is often used as it is simpler to develop and integrate within the proton therapy gantry. Partial-angle coverage of these systems can however lead to limited-angle artefacts in the reconstructed PET image. We have previously demonstrated via simulations that time-of-flight (TOF) reconstruction reduces the artifacts accompanying limited-angle data, and permits proton range measurement with 1-2 mm accuracy and precision. In this work we show measured results from a small proof-of-concept dual-panel PET system that uses TOF information to reconstruct PET data acquired after proton irradiation. The PET scanner comprises of two detector modules, each comprised of an array of 4×4×30 mm3 lanthanum bromide scintillator. Measurements are performed with an oxygen-rich gel-water, an adipose tissue equivalent material, and in vitro tissue phantoms. For each phantom measurement, 2 Gy dose was deposited using 54 - 100 MeV proton beams. For each phantom, a Monte Carlo simulation generating the expected distribution of PET isotope from the corresponding proton irradiation was also performed. Proton range was calculated by drawing multiple depth-profiles over a central region encompassing the proton dose deposition. For each profile, proton range was calculated using two techniques (a) 50% pick-off from the distal edge of the profile, and (b) comparing the measured and Monte Carlo profile to minimize the absolute sum of differences over the entire profile. A 10 min PET acquisition acquired with minimal delay post proton-irradiation is compared with a 10 min PET scan acquired after a 20 min delay. Measurements show that PET acquisition with minimal delay is necessary to collect 15O signal, and maximize 11C signal collection with a short PET acquisition. In comparison with the 50% pick-off technique, the shift technique is more robust and offers better precision in measuring the proton range for the different phantoms. Range measurements from PET images acquired with minimal delay, and the shift technique demonstrate the ability to achieve <1.5 mm accuracy and precision in estimating proton range.

Feasibility of Observing Gamma-Ray Polarization from Cygnus X-1 Using a CubeSat

Abstract Instruments flown on CubeSats are small. Meaningful applications of CubeSats in astronomical observations rely on the choice of a particular subject that is feasible for CubeSats. Here we report the result of a feasibility study for observing gamma-ray polarization from Cygnus X-1 using a small Compton polarimeter on board a 3U CubeSat. Silicon detectors and cerium bromide scintillators were employed in the instrument models that we discuss in this study. Through Monte Carlo simulations with a Geant4-based MEGAlib package, we found that, with a 10 Ms on-axis, zenith-direction observation in a low-inclination, low-altitude, Earth-orbit radiation background environment, the minimum detectable polarization degree can be down to about 10% in 160–250 keV, 20% in 250–400 keV, and 65% in 400–2000 keV. A 3U CubeSat dedicated to observing Cygnus X-1 can therefore yield useful information on the polarization state of gamma-ray emissions from the brightest persistent X-ray black hole binary in the sky.