SiPM Array Research Articles

Light yield of cold undoped CsI crystal down to 13 keV and the application of such crystals in neutrino detection

The light yield of an undoped CsI crystal at about 77 Kelvin was measured to be 33.5 , pm , 0.7 photo-electrons (PE) per keV electron-equivalent (keVee) in the energy range of [13, 60] keVee using X and gamma -rays from an ^{241}Am radioactive source. Based on this experimental result, the performance of 10 kg cryogenic inorganic scintillating crystals coupled to SiPM arrays to probe non-standard neutrino interactions through the detection of coherent elastic neutrino-nucleus scatterings at the spallation neutron source, Oak Ridge National Laboratory, was examined in detail.

A preliminary study on 3D position reconstruction of monolithic crystal readout

Compared to pixelated crystal detectors, monolithic crystal detectors present more advantages. Without reflective layer between crystal pixel, monolithic crystal detectors provide higher detection efficiency while being cheaper. Another important feature is that monolithic crystal detectors can provide depth of interaction (DOI) information, which can improve image quality in nuclear imaging systems. In this article, we aim to study a new positioning scheme of this kind of detector in order to push its applications in nuclear imaging systems. Fan-beam collimation and convolutional neural network are combined to reconstruct interaction points in crystal. Firstly, we built a monolithic detector model based on Geant4 and validated this positioning scheme with simulation data. Then, we constructed a monolithic GAGG(Ce) detector and evaluated its performance with experimental data. With proposed positioning scheme, in experiment, we obtained ~ 1.7 mm FWHM resolution on average in x-/y-direction, while ~ 2.5 mm FWHM resolution on average in DOI direction for a 33 × 33 × 10 mm3 monolithic GAGG(Ce) crystal coupled with 8 × 8 SiPM array. Through simulations and experiments, we validated our positioning scheme, i.e., fan-beam collimation and convolutional neural network. Convolutional neural network can reconstruct 3D positions of gamma-rays interaction points in a high resolution, and fan-beam collimation can provide high calibration efficiency; with combination of them, we established a high position resolution and high calibration efficiency positioning scheme for monolithic crystal detector.

SiPM development for space-borne and ground detectors: From Lazio-Sirad and Mini-EUSO to Lanfos

We describe some applications of SiPMs developed for space-borne detectors to be employed in astroparticle physics research. SiPMs were first installed in space in 2005 on board of the International Space Station (ISS) in the Lazio-Sirad experiment. In Lazio-Sirad the SiPMs have been used as sensors of a small calorimeter to measure radiation environment in space and assess the effectiveness of shielding for astronauts. More recently, a 64 pixel array of SiPMs was used in Mini-EUSO, an UV telescope to study UV terrestrial emissions. Mini-EUSO was launched in Summer 2019 on board the ISS and is observing the Earth from a nadir facing window in the Russian section of the station. The detector technology and readout electronics developed in these contexts can also be employed in ground-based applications, both in research and in technological transfer implementations. As an example, we also discuss the application of SiPM detectors developed for EUSO detectors in the development of Lanfos, a detector to assess the amount of Cesium in food produced in the regions affected by the 2011 Fukushima power plant accident.

Cryogenic SiPM arrays for the DUNE photon detection system

In this paper we report on the characterization of SiPM tiles developed for the R&D on the DUNE Photon Detection System. The tiles were produced by Fondazione Bruno Kessler (FBK) employing Near Ultra-Violet High Density Standard Field (NUV-HD-SF) SiPMs. Special emphasis is given on cryo-reliability of the sensors, i.e. the stability of electric and mechanical properties after thermal cycles at room and 77 K temperature. The characterization includes the determination of the I–V curve, a high sensitivity measurement of Dark Count Rate at different overvoltages, and correlated noise. The single p.e. sensitivity is measured as a function of the number of sensors connected to a single electronic channel, after amplification at 77 K using a dedicated cold amplifier.

Construction status of the Mu2e crystal calorimeter

The Mu2e experiment at Fermilab will search for the charged-lepton flavor violating neutrino-less conversion of a negative muon into an electron in the field of an aluminum nucleus. The Mu2e detector is composed of a tracker, an electromagnetic calorimeter and an external veto for cosmic rays. The calorimeter plays an important role in providing excellent particle identification capabilities and a fast online trigger filter, while aiding the track reconstruction capabilities. Calorimeter requirements are to provide a large acceptance for 0∼10 MeV electrons and reach: i) a time resolution better than 0.5 ns; ii) an energy resolution better than 10%; and iii) a position resolution of 1 cm. The calorimeter consists of two disks, each one made of 674 pure CsI crystals. Each crystal is readout by two large area 2×3 arrays of UV-extended SiPMs of 6×6 mm2 dimensions. A large scale prototype (Module-0) has been tested at an electron beam. We report here the tests done to finalize the calorimeter design, the results obtained with Module-0 and the status of production. At this time, the performance characteristics of 85% of the crystals and all of the SiPMs have been measured. The calorimeter engineering drawings have been completed and the large mechanical components are under fabrication. Analog and digital electronics have been prototyped and tested with irradiation dose. Their serial production is being organized. The calorimeter assembly phase is planned for mid-2020.

A depth-encoding PET detector for high resolution PET using 1 mm SiPMs

A dual-ended readout PET detector based on two Hamamatsu 16 × 16 arrays of 1 × 1 mm2 SiPMs coupled to both ends of a 25 × 25 array of 0.69 × 0.69 × 20 mm3 polished LYSOs was evaluated in terms of flood histogram, energy resolution, timing resolution, and DOI resolution. The SiPM arrays have a pitch size of 1.2 mm. Each SiPM pixel has an active area of 1 × 1 mm2, and was fabricated using 15 μm microcells. The LYSO array has a pitch size of 0.75 mm, and the crystals are separated using Toray reflector with a thickness of 50 μm. The flood histogram and energy resolution were measured at different overvoltages (ranging from 1.5 to 7.0 V, in 0.5 V steps) and at four different temperatures (−7, 0, 10 and 20 °C). The timing resolution and DOI resolution were obtained at the optimal overvoltage for the flood histogram and at each different temperature. Overall, the results show better performance was obtained at lower temperatures, and that the optimal overvoltage decreased at higher temperatures. The optimal overvoltage was 5.0 V (corresponding to a bias voltage of 68.5 V) in order to achieve the highest quality flood histogram at 0 °C. Under these conditions, the flood histogram quality, energy resolution, timing resolution, and DOI resolution were 3.26 ± 0.65, 18.4 ± 4.5%, 1.70 ± 0.12 ns and 2.22 ± 0.19 mm, respectively. The flood histograms and energy resolution were also obtained at different activities. The results show that better flood histogram and energy resolution were obtained at lower activity, however all the crystals can be resolved at an event rate of over 210 k cps, indicating the DOI detector module can be used both for high resolution human brain PET and small animal PET applications.

Gaussian position-weighted center of gravity algorithm for multiplexed readout

Readout signal multiplexing is a commonly used method to reduce the electronics cost in positron emission tomography (PET) systems, and the calculation of the scintillation coordinates typically is done by using a center of gravity (CoG) technique due to its simplicity and ease of implementation. This comes with a drawback, since CoG has a non-linear response at the periphery of the detector due to the lack of weights beyond the detector. Detectors with multiplexed readout that are based on finely segmented scintillators and coarsely segmented photosensors are known to suffer from the so-called edge effect where a pile-up of the reconstructed coordinates from the edge crystals is observed. This may lead to incorrect assignment of the events to crystal pixels and result in the formation of erroneous lines of response causing a degradation of spatial resolution and reduction of image contrast. To overcome the abovementioned limitations in gamma-ray detectors with multiplexed photosensor readout, we propose to use a modified Gaussian position-weighted center of gravity (PW-CoG) technique for the calculation of gamma-ray interaction position. Here, the proposed method is applied to PET detectors with 24 24 LYSO crystals read out by 8 8 SiPM array with 64:16 row/column multiplexing. Furthermore, we compared the modified Gaussian PW-CoG and truncated center of gravity coordinate reconstruction methods. It was observed that both algorithms resolve peaks corresponding to events registered in the crystal pixels on the periphery of the crystal array. However peak-to-valley ratios and crystal resolvability metrics for the PW-CoG algorithm are generally greater.

The liquid argon detector and measurement of SiPM array at liquid argon temperature

Particle detectors based on liquid argon (LAr) have recently become recognized as an extremely attractive technology for the direct detection of dark matter as well as the measurement of coherent elastic neutrino–nucleus scattering (CEνNS). The Chinese argon group at Institute of High Energy Physics has been studying the LAr detector technology and a LAr detector has been operating steadily. A program of using a dual phase LAr detector to measure the CEνNS at Taishang Nuclear Power Plant has been proposed and the R&D work is ongoing. Considering the requirements of ultra-low radio-purity and high photon collection efficiency, SiPMs will be a good choice and will be used in the detector. In this proceeding, an introduction of the LAr detector and the measurement results of SiPM array at LAr temperature will be presented.

Characterization of a High-Aspect Ratio Detector With Lateral Sides Readout for Compton PET

Although positron emission tomography is probably the most specific molecular imaging modality, it still lacks a high detection sensitivity. One way of improving this is by implementing larger axial scanners and, therefore, increasing the solid angle coverage. Alternatively, it is possible to increase the sensitivity gain by improving the timing capabilities of the detectors. However, from the most fundamental nature of particle interactions with matter, the 511-keV gamma rays suffer, in most of the cases, from scatter collisions either in the patient or within the detector block, before a photoelectric event eventually occurs. Recovering all scattered (Compton) events would improve scanner sensitivity. In this work, we show the performance of a detector block geometry suitable for the development of PET scanners based on several detector layers. A geometry using multiple layers favor the process of scattered events, at the time that allows one for their proper identification. The detector block consists of a LYSO crystal with $51.5\times 51.5$ mm2 surface and 3 mm thickness, resulting in a very high aspect ratio above 17. Four custom-made SiPM arrays of $1\times 16$ elements with $3\times 3$ mm2 area each are coupled to the lateral sides of the crystal. Four different methods to estimate the gamma-ray interaction position using the information collected by the four SiPM arrays have been implemented and compared in order to assess the most suitable one for this detector configuration and aspect ratio. A novel calibration method based on Voronoi diagrams has been successfully implemented, allowing us to recover data for the entire detector block. We have reached an intrinsic spatial resolution for the whole block of less than 1.6 mm FWHM, combined with an energy resolution of 12.1%. We have also compared the performance results with detector blocks using the same crystal but employing the standard backreading approach. Similar results were obtained but making use of four times less SiPM active area in the case of the lateral reading compared to the backreading method, and with the possibility to minimize the undesirable scatter in the photosensor layers.

Beam test characterisation of a Plastic Scintillator Prototype for the space-based cosmic ray experiment HERD

The High Energy cosmic-Radiation Detector (HERD) facility is planned to go onboard China's Space Station, planned to be operational starting in around 2025 for about 10 years. The main scientific objectives of HERD are the search for signals of dark matter annihilation products, precise cosmic electron/positron spectrum and measurements of anisotropy up to 10 TeV, precise cosmic ray spectrum and composition measurements up to the knee energy (1 PeV), and high energy γ-ray monitoring and survey. HERD consists of a 3D cubic crystals calorimeter (CALO) surrounded by microstrip silicon trackers (STKs) and scintillating fiber trackers (FIT) and by a Plastic Scintillator Detector (PSD) for γ-ray veto and ion charge measurement. A PSD prototype consisting of a scintillator tile readout by two arrays of SiPMs on opposite sides has been tested with proton and C ion beam at the CNAO (Centro Nazionale Adroterapia Oncologica) in Pavia, (Italy). Preliminary results on charge resolution are presented.

Characterization of four readout circuits for an MR compatible, preclinical PET detector

We are building a high sensitivity preclinical PET/MRI insert using a highly multiplexed light sharing PET module. Each module incorporates four 19 × 19 arrays of 1 × 1 × 20 mm3 LYSO crystals with dual-ended DOI encoding readout, requiring 32 readout channels for positioning and eight channels for timing. These constraints necessitate compact, robust electronics for digitization. We have characterized four linearized time-over-threshold circuits based on these detector requirements. The four circuits allow for high channel density and can digitize signals from highly multiplexed light sharing detectors. Each circuit digitizes one channel of a multiplexed SiPM array, yielding a binary output that interfaces directly with an FPGA. Using the optimal circuit, we have characterized the performance of a pair of PET modules. The four circuits were characterized based on linearity of the 22Na photopeak positions and energy resolution at 511 keV, as well as separation of elements in a 10 × 10 array of 1.2 mm LYSO crystals coupled with a specular reflector. Practical measures of performance were comparable to those obtained with a DRS evaluation board, which served as a reference acquisition system. The ratio of the 22Na photopeak positions was 2.0 for each circuit and the reference system, implying 20% saturation due to the SiPM. PET energy resolution of the optimal circuit was 11.8% FWHM for a single crystal versus 12.6% for the reference system, and crystals were equally well separated in all cases. PCBs implementing the optimal readout circuit were fabricated and used to construct two complete detector modules. Crystals in each of the four blocks in the module were well resolved, with a mean energy resolution of 24.4 ± 4.7%. Two modules operating in coincidence showed a single detector timing resolution of 3.0 ns, which is appropriate for preclinical applications.

Prospect of undoped inorganic crystals at 77\xa0Kelvin for low-mass dark matter search at Spallation Neutron Source

Investigated in this work were sensitivities of a prototype detector for the detection of low-mass dark matter particles produced at the Spallation Neutron Source at the Oak Ridge National Laboratory in 2 years of data taking. The presumed prototype consisted of 10 kg undoped CsI or NaI scintillation crystals directly coupled with SiPM arrays operated at 77 K. Compared to the COHERENT CsI(Na) detector, a much higher light yield was assumed for the prototype. An experiment with a cylindrical 1 kg undoped CsI crystal coupled directly to two photomultiplier tubes at about 77 K was conducted as the first step to verify the idea. A light yield of 26.0 pm 0.4 photoelectrons per keV electron-equivalent was achieved. This eliminated the concern of self light absorption in large crystals raised in some of the early studies.

Study and characterization of WLS for ARAPUCA to DUNE experiment

The photon detection system of the far detector of the Deep Underground Neutrino Experiment (DUNE) will collect liquid argon scintillation photons with an array of modules whose working principle is based on the ARAPUCA technology. These devices acting as light traps are able to convert VUV scintillation photons into visible ones and capture them inside a reflective cavity observed by an array of SiPMs as active photo-sensitive elements. The use of wavelength shifting techniques in light collecting systems for particle detection in liquid argon is of fundamental importance, since the scintillation photon wavelength is around 127 nm of the photon produced which is extremely challenging to be directly detected. The main objective of the present work was to explore and characterize different substrates, wavelength shifting compounds and deposition methods to optimize and improve the light collection of the ARAPUCA device.

Ce:LaBr3 crystals with SiPM array readout and temperature control for the FAMU experiment at RAL

Compact X-rays detectors made of 1/2′′ Ce:LaBr3 crystals of cubic shape with SiPM array readout have been developed for the FAMU experiment at RIKEN-RAL, to instrument regions of difficult access. Due to the high photon yield of Ce:LaBr3 it was possible to use a simple readout scheme based on CAEN V1730 digitizers, without a dedicated amplification stage. The drift with temperature of SiPM gain was corrected by using CAEN A7885D regulated power supply chips with temperature feedback. Energy resolutions (FWHM) around 3.5% at the 137Cs peak and around 9% at the 57Co peak were obtained.

Characterization of monolithic GAGG:Ce coupled to both PMT and SiPM array for gamma imaging in Nuclear Medicine

GaGG:Ce scintillation crystal is very useful for nuclear imaging purposes, thanks to its several advantages (high density, short decay time, high light yield and good energy resolution, no self-activity, no hygroscopic). However, only the recent improvements in the growth processes make it available with large size, in order to use it in monolithic configuration. The main drawbacks of pixelated crystals, as non-uniform response, high production costs and optical light loss, could be therefore overcome. In this work the characterization of this promising crystal coupled both to a single channel PMT (spectrometric purpose) and to a new technology SiPM (50% PDE and 74% geometrical fill factor) has been performed. The detection efficiency results good both for SPECT (87% at 122 keV) and for PET (18% at 356 keV) applications. However, the unexpected result arises from the energy resolution: at 356 keV 8.9% and 8.0% for single channel PMT and SiPM configuration, respectively. In other terms, the used SiPM allows to achieve higher energy resolution than single channel PMT. Moreover, a high imaging performance has been observed, with a millimeter intrinsic spatial resolution.

A position sensitive scintillation detector using a side-by-side GAGG-F/GAGG-T phoswich block

Position sensitive detectors are the key component of gamma-ray imaging systems such as coded-aperture cameras and emission computed tomography systems. Improving the intrinsic spatial resolution of detectors is critical to system performances. Recent advance of the GAGG scintillator production allows variable decay time with different Al/Ga ratios. In this paper, we developed a novel position sensitive scintillation detector using a side-by-side fast\ obreakdash-GAGG/typical-GAGG (GAGG-F/GAGG-T) phoswich array, which consisting of 12×12 phoswich unit pairs assembled by the GAGG-F scintillator (decay time constant ∼ 50 ns) and the GAGG-T scintillator (decay time constant ∼ 90 ns) in a pixel size of 1.35×2.7×4 mm3 and coupled to a 8×8 SiPM (MicroFJ\ obreakdash-30035\ obreakdash-TSV) array. An experiment was conducted using the irradiation of a 57Co source (122 keV) . Experimental results demonstrate that events from the GAGG\ obreakdash-F and GAGG-T scintillators can be discriminated with only 7% mis-assignment probability. The 12×12 of GAGG\ obreakdash-F and GAGG-T scintillator arrays are both distinguishable in separated flood maps. The average energy resolutions of GAGG\ obreakdash-F and GAGG-T scintillators at 122 keV are 27.58% and 23.51% respectively. The side-by-side GAGG-F/GAGG-T detector has the advantage of improved intrinsic spatial resolution, no intrinsic background radiation and uniform detection efficiency.

Design and Performance Evaluation of a BGO + SiPM Detector for High-Energy Prompt Gamma Imaging in Proton Therapy Monitoring

Proton therapy is attracting increasing attention nowadays owing to its accurate dose delivery to the target tumor. However, this advanced treatment modality is subject to proton beam range uncertainty, which could lead to overdose in healthy tissues. In the past decades, prompt gamma imaging (PGI) has gained increasing interest and been proved promising for realtime proton beam monitoring. The detection of 2-8 MeV high energy prompt gamma, however, poses a serious challenge for PGI system design, especially, for the detector design. In this article, we propose a prompt gamma detector design for a PGI system under development in our lab. The detector was composed of a 12 x 12 BGO block coupled to an 8 x 8 SiPM array with a crystal pixel size of 3.5 mm x 3.5 mm x 30 mm. A numerical simulation model was developed to evaluate the SiPM saturation effect caused by the finite number of microcells in each SiPM pixel while a huge number of optical photons might impinge the SiPM pixel under high energy gamma ray irradiation. Experiments under high energy gamma isotopes ( <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">22</sup> Na - 511 keV, 1.275 MeV, <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">88</sup> Y - 898 keV, 1.836 MeV, and <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">232</sup> Th - 2.6 MeV) irradiation were conducted to evaluate positioning performance, energy response linearity, and energy resolution (ER) of the detector. Root mean squared (RMS) metric was defined to assess the detector's positioning performance quantitatively. The numerical simulation results demonstrated that the SiPM saturation effect of the proposed detector design is negligible up to 10-MeV gamma photon detection. In the experimental studies, the obtained energy response linearity was 0.9997±0.0005, indicating almost no SiPM saturation effect for up to 2.6-MeV gamma photon detection with the proposed detector design. ER of 31.96% (511 keV), 26.67% (898 keV), 20.19% (1.275 MeV), 17.38% (1.836 MeV), and 15.88% (2.6 MeV) were achieved. With increased gamma photon energy, the crystal elements in the flood maps became clearer with reduced RMS value of the flood maps, indicating improved positioning performance. Based on the simulation and experimental results, we conclude that the proposed detector design is feasible for the PGI system with good energy and positioning performance as well as excellent anti-saturation capability for high energy gamma ray detection.

Novel preclinical PET geometrical concept using a monolithic scintillator crystal offering concurrent enhancement in spatial resolution and detection sensitivity: a simulation study

We propose a small-animal PET scanner design combining two sets of monolithic crystals with two different thicknesses. The detectors with thinner crystals serve for high resolution imaging while the thicker crystals retain the detection efficiency. Two small-animal PET models based on 10 and 12 detector blocks made of monolithic LYSO crystals were implemented in the GEANT4 Monte Carlo toolkit. In each of these models, half of the detector blocks consisted of a crystal thickness of 10 mm whereas the second half had a crystal thickness of 2 mm. The scintillator crystals were coupled to SiPM arrays. For the first model, the detector blocks were arranged in a full-ring polygonal geometry in such a way that detector blocks with the same thickness were sitting opposite to each other. For the second model, detector blocks with different crystal thicknesses were facing each other. The performance of the proposed PET models was assessed using standard parameters, including spatial resolution, sensitivity and noise equivalent count rate. Comparison was made with conventional PET models with crystal thicknesses of 2 mm, 6 mm and 10 mm. PET models with a crystal thickness of 2 mm led to the highest spatial resolution (up to 0.6 mm FWHM) at the cost of poor absolute sensitivity (2.5%). On the other hand, PET models with a crystal thickness of 10 mm led to good detection efficiency (4.4%), yet with substantial degradation of spatial resolution (1.2 mm FWHM). The proposed PET models with thick and thin crystals exhibited an optimal trade-off between spatial resolution and sensitivity outperforming the PET model with fixed 6 mm crystal by achieving a spatial resolution of 0.7 mm and absolute sensitivity of 3.7%. The novel proposed PET design concept achieved an optimal trade-off between the sensitivity and spatial resolution by combining two sets of monolithic crystals.

Exploring TOF capabilities of PET detector blocks based on large monolithic crystals and analog SiPMs

Monolithic scintillators are more frequently used in PET instrumentation due to their advantages in terms of accurate position estimation of the impinging gamma rays both planar and depth of interaction, their increased efficiency, and expected timing capabilities. Such timing performance has been studied when those blocks are coupled to digital photosensors showing an excellent timing resolution.In this work we study the timing behaviour of detectors composed by monolithic crystals and analog SiPMs read out by an ASIC. The scintillation light spreads across the crystal towards the photosensors, resulting in a high number of SiPMs and ASIC channels fired. This has been studied in relation with the Coincidence Timing Resolution (CTR). We have used LYSO monolithic blocks with dimensions of 50 × 50 × 15 mm3 coupled to SiPM arrays (8 × 8 elements with 6 × 6 mm2 area) which compose detectors suitable for clinical applications.While a CTR as good as 186 ps FWHM was achieved for a pair of 3 × 3 × 5 mm3 LYSO crystals, when using the monolithic block and the SiPM arrays, a raw CTR over 1 ns was observed. An optimal timestamp assignment was studied as well as compensation methods for the time-skew and time-walk errors. This work describes all steps followed to improve the CTR. Eventually, an average detector time resolution of 497 ps FWHM was measured for the whole thick monolithic block. This improves to 380 ps FWHM for a central volume of interest near the photosensors. The timing dependency with the photon depth of interaction and planar position are also included.

The GECAM and its payload

<p indent="0mm">The Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) monitors gamma-ray bursts (GRBs) coincident with gravitational wave events over the whole sky. It also monitors other burst events, such as the high-energy radiation of fast radio bursts, various GRBs, and magnetar bursts. GECAM can measure the energy spectra, light curves, and location of all kinds of bursts. GECAM consists of two small satellites which operate in the same low earth orbit but in opposite geocentric directions. To obtain an all-sky field of view, the two satellites operate in opposite orbital phases. The GECAM payload includes two kinds of detectors: charged particle detector (CPD) and gamma-ray detector (GRD). Each GRD module consists of a LaBr₃:Ce scintillator and a SiPM array, and its gamma-ray detection range is <sc>5 keV–5 MeV.</sc> GECAM retrieves the locations of events such as GRBs through analyzing the data of the multiple GRDs on both satellites. Meanwhile, the CPD consists of a plastic scintillator and a SiPM array that detects charged particles of energies from <sc>300 keV</sc> to <sc>5 MeV.</sc> The GECAM distinguishes the charged particle burst events in space by jointly analyzing the GRD and CPD data. The payload electronic box (EBOX) provides in-flight trigger and burst localization. The trigger and burst location data are transmitted by a BeiDou Short Message system, which allows GECAM to guide other telescopes to do follow-up observations.