Count Rate Research Articles

Study of readout system for 3He linear position sensitive detectors

This study introduces a readout system for 3He linear position-sensitive detectors (LPSDs), tailored for the Small Angle Neutron Scattering (SANS) spectrometer of the Compact Pulsed Hadron Source (CPHS) at Tsinghua University. Central to this system is the employment of a trapezoidal filter as the primary signal shaper, selected for its enhanced noise filtering capabilities and efficacy in mitigating ballistic deficit. Additionally, the integration of a digital CR filter aims to counteract baseline drift within trigger signals. This innovative architecture underwent validation via computer programs using experimental data, demonstrating superior performance in spatial resolution compared to conventional Gaussian filter-based approaches. Meanwhile, the improvement in spatial resolution comes with a narrower pulse width, promising a higher throughput at high count rates. When applied to a 16-tube detector module, the system achieved an average position resolution of 3.63 mm (FWHM) at the central region and 4.03 mm at the end regions. Furthermore, with a pusle width of 0.6 μs, the 96-tube detector array is promised to sustain a count rate over 1 Mcps.

Addressing Statistical Power and Increasing Diversity in Hospice Research: Electronic Medical Record Participant Identification Compared to Nurse Referral Approaches to Recruitment

ContextRecruitment of targeted samples into hospice clinical trials is often challenging. While electronic medical records (EMR) are commonly used in hospital-based research, it is uncommon in hospice research. The community setting and the variability in hospices and their medical record creates unique challenges. ObjectivesThis paper compares recruitment in two hospice randomized controlled trials, each of which had a group recruited by using the EMR identification and a group recruited by nurse referral. We sought to answer three questions: 1) What is the impact of using the EMR to identify hospice participants for clinical research? 2) How do the referral count and consent rate (referrals that ultimately result in verbal informed consent to participate in research) differ between hospice agencies using an EMR participant identification approach compared to those using a nurse referral approach? and 3) What are the challenges associated with using the EMR to identify potential research participants? MethodRecruitment data from two hospice clinical trials was combined into a new database. Data from hospice nurse referral agencies was compared with data from those agencies who participated in EMR-identified referrals. ResultsThe EMR identification process was feasible and efficient, resulting in more referrals and more consented participants than the nurse referral method. Of particular interest is that 8% more black caregivers were recruited using the EMR identification process than the nurse referral. ConclusionsThe EMR-identified recruitment process is the recommended method in hospice research.

Radiation Damage on Silicon Photomultipliers from Ionizing and Non-Ionizing Radiation of Low-Earth Orbit Operations.

Silicon Photomultipliers (SiPMs) are single photon detectors that gained increasing interest in many applications as an alternative to photomultiplier tubes. In the field of space experiments, where volume, weight and power consumption are a major constraint, their advantages like compactness, ruggedness, and their potential to achieve high quantum efficiency from UV to NIR makes them ideal candidates for spaceborne, low photon flux detectors. During space missions however, SiPMs are usually exposed to high levels of radiation, both ionizing and non-ionizing, which can deteriorate the performance of these detectors over time. The goal of this work is to compare process and layout variation of SiPMs in terms of their radiation damage effects to identify the features that helps reduce the deterioration of the performance and develop the next generation of more radiation-tolerant detectors. To do this, we used protons and X-rays to irradiate several Near Ultraviolet High-Density (NUV-HD) SiPMs with small areas (single microcell, 0.2 × 0.2 mm2 and 1 × 1 mm2) produced at Fondazione Bruno Kessler (FBK), Italy. We performed online current-voltage measurements right after each irradiation step, and a complete functional characterization before and after irradiation. We observed that the main contribution to performance degradation in space applications comes from proton damage in the form of an increase in primary dark count rate (DCR) proportional to the proton fluence and a reduction in activation energy. In this context, small active area devices show a lower DCR before and after irradiation, and we propose light or charge-focusing mechanisms as future developments for high-sensitivity radiation-tolerant detectors.

HHEPATO-Cy5, a Bimodal Tracer for Image-Guided Hepatobiliary Surgery.

Liver cancer is a leading cause of cancer deaths worldwide. Surgical resection of superficial hepatic lesions is increasingly guided by the disrupted bile excretion of the fluorescent dye indocyanine green (ICG). To extend this approach to deeper lesions, a dedicated bimodal tracer that facilitates both fluorescence guidance and radioguidance was developed. Methods: A tracer comprising a methylated cyanine-5 (Cy5) fluorescent dye and a mercaptoacetyltriserine chelate (hHEPATO-Cy5) was synthesized and characterized. Cellular uptake and excretion were evaluated in hepatocyte cultures (2-dimensional culture and invitro lesion model), using a fluorescent bile salt, MitoTracker dye, and methylated Cy5 as a control. After radiolabeling, the pharmacokinetics of 99mTc-hHEPATO-Cy5 were assessed in mice over 24 h (percentage injected dose and percentage injected dose per gram of tissue, SPECT/CT imaging and fluorescence imaging). The ability to provide real-time fluorescence guidance during robot-assisted hepatobiliary surgery was evaluated in a porcine model using ICG as a reference. Results: The unique molecular signature of hHEPATO-Cy5 promotes hepatobiliary excretion. In vitro studies on hepatocytes showed that where methylated Cy5 remained internalized, hHEPATO-Cy5 showed fast clearance (10 min) similar to that of fluorescent bile salt. In vivo use of 99mTc-hHEPATO-Cy5 in mice revealed liver accumulation and rapid biliary clearance. The effectiveness of bile clearance was best exemplified by the 2-orders-of-magnitude reduction in count rate for the gallbladder (P = 0.008) over time. During hepatobiliary surgery in a porcine model, hHEPATO-Cy5 enabled fluorescence-based lesion identification comparable to that of ICG. Conclusion: The bimodal 99mTc-hHEPATO-Cy5 provides an effective means to identify liver lesions. Uniquely, it helps overcome the shortcomings of fluorescence-only approaches by allowing for an extension to in-depth radioguidance.

Batch VUV4 characterization for the SBC-LAr10 scintillating bubble chamber

The Scintillating Bubble Chamber (SBC) collaboration purchased 32 Hamamatsu VUV4 silicon photomultipliers (SiPMs) for use in SBC-LAr10, a bubble chamber containing 10 kg of liquid argon. A dark-count characterization technique, which avoids the use of a single-photon source, was used at two temperatures to measure the VUV4 SiPMs breakdown voltage (VBD), the SiPM gain (g SiPM), the rate of change of g SiPM with respect to voltage (m), the dark count rate (DCR), and the probability of a correlated avalanche (PCA) as well as the temperature coefficients of these parameters. A Peltier-based chilled vacuum chamber was developed at Queen's University to cool down the Quads to 233.15 ± 0.2 K and 255.15 ± 0.2 K with average stability of ±20 mK. An analysis framework was developed to estimate VBD to tens of mV precision and DCR close to Poissonian error. The temperature dependence of VBD was found to be 56 ± 2 mV K-1, and m on average across all Quads was found to be (459 ± 3(stat.)±23(sys.))× 103 e- PE-1 V-1. The average DCR temperature coefficient was estimated to be 0.099 ± 0.008 K-1 corresponding to a reduction factor of 7 for every 20 K drop in temperature. The average temperature dependence of PCA was estimated to be 4000 ± 1000 ppm K-1. PCA estimated from the average across all SiPMs is a better estimator than the PCA calculated from individual SiPMs, for all of the other parameters, the opposite is true. All the estimated parameters were measured to the precision required for SBC-LAr10, and the Quads will be used in conditions to optimize the signal-to-noise ratio.

A Dark Count Rate Self-Adjusting Charge Pump With Negative Feedback Control for SPAD Array Biasing

A Dark Count Rate Self-Adjusting Charge Pump With Negative Feedback Control for SPAD Array Biasing

Neutron activation of stable isotopes in soil and groundwater from a radionuclide production facility, South Africa.

The neutron activation of stable isotopes in environmental matrices, such as soil and groundwater, is a critical aspect of assessing the impact of radionuclide production facilities on the surrounding ecosystem. The envisioned Low-Energy Radioactive Ion Beams (LERIB) facility at the iThemba LABS, South Africa is anticipated to generate significant sources of ionising radiation. The study investigated the possible repercussions of neutron irradiation stemming from the facility, focusing on the activation of stable isotopic compositions in the environment. The investigation employed a combination of experimental and analytical techniques to characterize the neutron activation products in soil and groundwater samples collected from the vicinity. Samples were collected from designated areas for background radiological measurements and were irradiated with neutrons for a period of 1 h. The induced radioactivity measured by the High Purity Germanium detector included 24Na, 22Na, 54Mn, 52Mn, and 46Sc. The application of Darcy's law for groundwater velocity suggests that radionuclides in groundwater will migrate at an average flow velocity of 0.8 m/day. The isotopes with longer half-lives have count rates at background concentrations; therefore, environmental impacts on the site and surrounding communities might be minimal.

Prognostic value of hematological indicators in preeclampsia

The objective: to evaluate the changes in hematological indicators as early predictors of the development of preeclampsia.Materials and methods. A retrospective cohort study was conducted with the participation of 49 pregnant women in the period from March 2020 to January 2022. All women were observed in the women’s consultation of the private medical center “Leleka”.Pregnant women were divided into two groups: the main group – women who were diagnosed with preeclampsia at >20 weeks of pregnancy, n=20), and the control group (n=29) – women without preeclampsia during pregnancy.Each woman underwent a general blood test, the systemic inflammatory response index (SIRI), allergy index (AI), immunoreactivity index (II), adaptation index (А) in I (up to 12 weeks), II (13–27 weeks) and III (from 28 weeks) trimesters of pregnancy, respectively, were calculated.Results. Pregnant women, in whom subsequently preeclampsia developed, had statistically significant differences in white blood cell count and erythrocyte sedimentation rate (ESR) compared to controls.The AI index decreased statistically significantly in the control group in the II trimester compared to the I trimester (р=0.05), while the changes in the main group were statistically insignificant. The median AI indicator in the main group decreases by 22.7% in the II trimester, and increases by 8.9% in the III trimester; in the control group the median AI decreases by 12.3% and 7.5%, respectively.The median adaptation index in the main group statistically significantly decreases by 25.7% in the II trimester and increases by 19.2% in the III trimester. In the control group, this index does not increase in the III trimester.Conclusions. The dynamics of the main hematological indicators and calculated indices can be useful for predicting of preeclampsia development. Carrying out a general blood test as a widely available method is possible in order to stratify the individual risk of preeclampsia development in combination with other generally accepted factors of this complication.High values of leukocytes and ESR in the early terms of pregnancy in women who subsequently developed preeclampsia confirm the role of inflammation as an etiopathogenetic factor. A change in the integral hematological indices of allergy and adaptation can be an early predictor of preeclampsia.The results of this study predict the presence of preeclampsia clusters, the determination of the mechanisms of which will allow to expand the possibilities of preventive measures, which needs to be confirmed in large-scale randomized studies in the future.

Application of a superconductor detector (SNSPD) for infrared atmospheric lidar measurements

Infrared lidar systems are powerful tools in many environmental applications where high accuracy level, real time observations and eye safe operations are essential. The main challenge for infrared lidar systems rests on the lack of high-performance detectors operating at such wavelengths. A promising solution is represented by Superconducting Nanostrip Single Photon Detectors (SNSPDs), thanks to their optimal efficiency and noise at infrared wavelengths with a system detection efficiency close to one, a dark count rate of less than 1 count/s as well as few nanoseconds dead time and picosecond time resolution. Here, we report on the use of SNSPDs for atmospheric lidar observations at 1064 nm and compare the results with those obtained simultaneously at 532 nm using a photomultiplier (PMT) as detector. Our experimental findings show the potentiality of SNSPDs for future lidar applications in the infrared domain.

Bayesian peak identification method for low count rate gamma spectrum under short-time measurement based on physical priors

A Bayesian peak identification method based on physical model had been proposed in this study to perform qualitative analysis for the low count rate gamma spectrum under short-time measurement. Based on the prior knowledge about gamma detection, the distribution of energy deposited in the detector near the region of interest of a target peak through photoelectric effect, Compton scattering and multiple scattering had been analyzed and approximated using three elementary components, then, the distribution of each component after convolution had been studied, and at last, a probabilistic mixture model had been proposed to directly describe the distribution of measured energy within region of interest. When the data measurement has been completed, a Gibbs sampler was used to estimate the posterior distribution of model parameters to discriminate the existence of target peaks. The numerical and physical experiments were performed to verify the effectiveness of the parameter estimation algorithm and the performance of the proposed identification method. The numerical experiments showed the identification precision is proportional to counts and peak-to-total ratio, when the peak-to-total ratio is greater than 0.5, the proposed method could identify the peak with a probability greater than 50% given 50 observations. The physical experiment used a NaI(Tl) detector to measure 137Cs, 60Co and 152Eu sources in a laboratory environment at different equivalent distances, the peak identification precision had been tested for the proposed method, and the experiments proved that the probabilistic model is a good approximation to the physical process, and the proposed identification method outperformed the conventional method under short-time measurement conditions.

Prior image-based generative adversarial learning for multi-material decomposition in photon counting computed tomography

BackgroundPhoton counting detector computed tomography (PCD-CT) is a novel promising technique providing higher spatial resolution, lower radiation dose and greater energy spectrum differentiation, which create more possibilities to improve image quality. Multi-material decomposition is an attractive application for PCD-CT to identify complicated materials and provide accurate quantitative analysis. However, limited by the finite photon counting rate in each energy window of photon counting detector, the noise problem hinders the decomposition of high-quality basis material images. MethodsTo address this issue, an end-to-end multi-material decomposition network based on prior images is proposed in this paper. First, the reconstructed images corresponding to the full spectrum with less noise are introduced as prior information to improve the overall signal-to-noise ratio of the data. Then, a generative adversarial network is designed to mine the relationship between reconstructed images and basis material images based on the information interaction of material decomposition. Furthermore, a weighted edge loss is introduced to adapt to the structural differences of different basis material images. ResultsTo verify the performance of the proposed method, simulation and real studies are carried out. In simulation study of structured fibro-glandular tissue model, the results show that the proposed method decreased the root mean square error by 67 % and 26 % on adipose, 66 % and 28 % on fibroglandular, 52 % and 8 % on calcification, compared to butterfly network and dual interactive Wasserstein generative adversarial network. ConclusionExperimentally, the proposed method shows certain advantages over other methods on noise suppression effect, detail retention ability and decomposition accuracy.

Development of a fast neutron monitoring detector for the NDPS neutron TOF facility by using Parallel Plate Avalanche Counters

A Parallel Plate Avalanche Counter (PPAC) neutron monitoring detector was developed and manufactured to monitor fast neutrons with energies greater than ∼1 MeV for use in the Nuclear Data Production System (NDPS), a neutron Time-of-Flight (TOF) facility of RAON. The detectors designed for monitoring fast neutrons comprise two sets of PPACs and a fast neutron converter. The performance of the detector was tested by using a241Am alpha source and neutron beams from a proton cyclotron. For the fast neutron converter, a thin thorium coating with a diameter of 60 mm was prepared by using the electrodeposition method. The areal density of thorium deposited on a thin aluminium layer with a thickness of 2 μm was determined by alpha spectrometry and measured to be 306 ± 7.65 μg/cm2. For the neutron beam test, neutrons were generated through the 9Be (p,n)9B reaction in a proton cyclotron facility. These generated neutrons were detected by using our PPAC neutron detector, and the experimentally measured count rate (1.74 ± 0.18 counts/s) agreed with the count rate (1.68 counts/s) calculated by PHITS v3.16 and GEANT4 v10.7 simulations. The timing resolution of the detector was estimated to be σ = 550 ps.

Performance evaluation of the 3D-ring cadmium–zinc–telluride (CZT) StarGuide system according to the NEMA NU 1-2018 standard

BackgroundThe application of semi-conductor detectors such as cadmium–zinc–telluride (CZT) in nuclear medicine improves extrinsic energy resolution and count sensitivity due to the direct conversion of gamma photons into electric signals. A 3D-ring pixelated CZT system named StarGuide was recently developed and implemented by GE HealthCare for SPECT acquisition. The system consists of 12 detector columns with seven modules of 16 × 16 CZT pixelated crystals, each with an integrated parallel-hole tungsten collimator. The axial coverage is 27.5 cm. The detector thickness is 7.25 mm, which allows acquisitions in the energy range [40–279] keV. Since there is currently no performance characterization specific to 3D-ring CZT SPECT systems, the National Electrical Manufacturers Association (NEMA) NU 1-2018 clinical standard can be tailored to these cameras. The aim of this study was to evaluate the performance of the SPECT/CT StarGuide system according to the NEMA NU 1-2018 clinical standard specifically adapted to characterize the new 3D-ring CZT.ResultsDue to the integrated collimator, the system geometry and the pixelated nature of the detector, some NEMA tests have been adapted to the features of the system. The extrinsic measured energy resolution was about 5–6% for the tested isotopes (99mTc, 123I and 57Co); the maximum count rate was 760 kcps and the observed count rate at 20% loss was 917 kcps. The system spatial resolution in air extrapolated at 10 cm with 99mTc was 7.2 mm, while the SPECT spatial resolutions with scatter were 4.2, 3.7 and 3.6 mm in a central, radial and tangential direction respectively. Single head sensitivity value for 99mTc was 97 cps/MBq; with 12 detector columns, the system volumetric sensitivity reached 520 kcps MBq−1 cc−1.ConclusionsThe performance tests of the StarGuide can be performed according to the NEMA NU 1-2018 standard with some adaptations. The system has shown promising results, particularly in terms of energy resolution, spatial resolution and volumetric sensitivity, potentially leading to higher quality clinical images.

Quantitative Analysis with EDS and WDS at High Count Rates

Quantitative Analysis with EDS and WDS at High Count Rates

Metrological characterization of a commercial single-photon source with high photon flux emission

We present a comprehensive metrological characterization of a commercial single-photon source with high photon flux emission for use in radiometry. The source is based on an InGaAs quantum dot in a micropillar. A comparative analysis of two excitation schemes—phonon-assisted excitation and two-photon excitation—explores differences in excitation power dependence, temporal stability and single-photon purity. The commercial source exhibits excellent properties for the field of quantum radiometry, achieving simultaneously a photon flux of (17.19 ± 0.09) million photons/s for a pulse repetition rate of 79.4 MHz, and a single-photon purity of 98%. Its optical power of (3.68 ± 0.02) pW is directly determined with a traceably calibrated low-noise photodiode. The ability to directly compare the photocurrent in a low-noise photodiode with the count rate at a single-photon avalanche detector allows for a seamless transition between the classical and quantum realizations of optical power. Therefore, we were able to build another bridge between classical and quantum radiometry by using a deterministic single-photon source.

High-performance oxygen terminated synthetic single crystal diamond detector for high gamma dose rate measurement

A high-performance oxygen terminated synthetic single crystal diamond (SCD) detector (4.5 × 4.5 × 0.5 mm3) is presented. The SCD detector exhibits an extremely low leakage current value of 0.29 pA/mm2 with an electric field of 0.3 V/μm. The charge collection spectrum measured with a238Pu source (5.48 MeV α-particles) irradiation shows that the electron and hole charge collection efficiency (CCE) reach as high as 99.1% and 98.9%, with an energy resolution as low as 2.87% and 2.53%, respectively, compared to Si detector. The SCD detector shows excellent radiation hardness and stability under 60Co γ-ray irradiation with a dose rate of 12.737 kGy/h at 150 V bias and is able to withstand a cumulative dose of up to at least 9.3 kGy. The detector output in current mode is linearly related to the dynamic dose rate (0.409 Gy/h-12.737 kGy/h). Similarly, the counting rate of the detector in counting mode exhibits a strong linear variation within the range of 2.6 mGy/h-1269.36 Gy/h. Our results fully indicate that our fabricated SCD detector can be potentially applied to harsh γ irradiation scenarios, which is of guiding significance on real-time dose monitoring.

Efficient, nonparametric removal of noise and recovery of probability distributions from time series using nonlinear-correlation functions: Photon and photon-counting noise.

A preceding paper [M. Dhar, J. A. Dickinson, and M. A. Berg, J. Chem. Phys. 159, 054110 (2023)] shows how to remove additive noise from an experimental time series, allowing both the equilibrium distribution of the system and its Green's function to be recovered. The approach is based on nonlinear-correlation functions and is fully nonparametric: no initial model of the system or of the noise is needed. However, single-molecule spectroscopy often produces time series with either photon or photon-counting noise. Unlike additive noise, photon noise is signal-size correlated and quantized. Photon counting adds the potential for bias. This paper extends noise-corrected-correlation methods to these cases and tests them on synthetic datasets. Neither signal-size correlation nor quantization is a significant complication. Analysis of the sampling error yields guidelines for the data quality needed to recover the properties of a system with a given complexity. We show that bias in photon-counting data can be corrected, even at the high count rates needed to optimize the time resolution. Using all these results, we discuss the factors that limit the time resolution of single-molecule spectroscopy and the conditions that would be needed to push measurements into the submicrosecond region.

Biodistribution and Absorption of Radiopharmaceutical 99mTc MDP in Various Bones of Lung Cancer Patients Using SPECT/CT Modalities

Lung-to-bone cancer metastasis frequently involves bone lesions, particularly in the vertebrae. A bone scan using the radiopharmaceutical 99mTc MDP is a common diagnostic tool for detecting advanced metastases. This research aimed to determine the conversion factor of count rate to unit activity, assess the range of source activity in bones with and without lesions, and analyze the relationship between lung cancer metastasis and radiopharmaceutical activity in various bones. The study involved 28 patients. Procedures included phantom manufacturing, determining the depth of Antero Posterior (AP) and Postero Anterior (PA) position bones, converting count rates to activity units, and assessing 99mTc MDP biodistribution in bones. Results indicated that the conversion factor of count rate to activity units in AP and PA positions for lumbar vertebrae, costa vera, ilium, and sacrum were (〖13.2×10〗^(-4); 4.9〖×10〗^(-4)) mCi/cps; (4.0〖×10〗^(-4); 4.4〖×10〗^(-4)) mCi/cps; (4.0〖×10〗^(-4); 4.9〖×10〗^(-4)) mCi/cps; and (〖12.2×10〗^(-4); 〖4.5×10〗^(-4)) mCi/cps. In addition, there is a range of source activity values and percentage of activity in the bones (lumbar vertebrae; costa vera; ilium; and sacrum), namely (0.019-0.053) mCi and (0.107-0.498)%; (0.020-0.045) mCi and (0.139-0.338)%; (0.024-0.066) mCi and (0.128-0.551)%; and (0.012-0.028) mCi and (0.078-0.264)%. Furthermore, there is a range of source activity values in the lesion-indicated bone (lumbar vertebrae; costa vera; ilium; and sacrum), namely (0.038-0.053) mCi; (0.024-0.045) mCi; (0.033-0.066) mCi; and (0.017-0.028) mCi. The relationship between lung cancer metastasis to various bones studied and the range of radiopharmaceutical activity values obtained is moderately positive.

Revisiting the dead time effects of Insight-HXMT/ME on timing analysis

ABSTRACT Dead time is a common instrumental effect of X-ray detectors, which would alter the behaviour of timing properties of astronomical signals, such as distorting the shape of power density spectra (PDS), affecting the root-mean-square of potential quasi-periodic oscillation signals, etc. We revisit the effects of the dead time of Medium Energy X-ray telescope (ME) onboard Insight-HXMT based on the simulation of electronic read-out mechanism that causes the dead time and the real data. We investigate dead time effects on the pulse profile as well as the quasi–periodic oscillation (QPO) signals. The dead time coefficient suggests a linear correlation with the observed count rate in each phase bin of the pulse profile according to the simulation of periodic signal as well as the real data observed on Swift J0243.6+6124. The Fourier-amplitude-difference (FAD) method could well recover the intrinsic shape of the observed PDS in the case that the PDS is from two identical detectors. We apply this technique on ME, by splitting the nine FPGA modules into two groups. The results indicate that the FAD technique suits the case when two groups of detectors are not largely different; and the recovered PDS of Sco X-1 observed by ME slightly enhances the significance of the previously known QPO signal, meanwhile the root-mean-square of QPO is significantly improved. We provide the FAD correction tool implemented in HXMTDAS for users in the future to better analyse QPO signals.

Fluorescence Enhancement of Single V2 Centers in a 4H-SiC Cavity Antenna.

Solid state quantum emitters are a prime candidate in distributed quantum technologies since they inherently provide a spin-photon interface. An ongoing challenge in the field, however, is the low photon extraction due to the high refractive index of typical host materials. This challenge can be overcome using photonic structures. Here, we report the integration of V2 centers in a cavity-based optical antenna. The structure consists of a silver-coated, 135 nm-thin 4H-SiC membrane functioning as a planar cavity with a broadband resonance yielding a theoretical photon collection enhancement factor of ∼34. The planar geometry allows us to identify over 20 single V2 centers at room temperature with a mean (maximum) count rate enhancement factor of 9 (15). Moreover, we observe 10 V2 centers with a mean absorption line width below 80 MHz at cryogenic temperatures. These results demonstrate a photon collection enhancement that is robust to the lateral emitter position.