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Physics Physics Instrumentation and Detectors

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Wednesday 9 September

Instrumentation and Detectors

Optimization and Underground Implementation of the KAPAE Phase II Detector for an Invisible New Particle Search in Positronium Decay

Dongwoo Jeong, Jaeyoung Cho, Doohyeok Lee et al. (+4 more)

The KAPAE Phase II detector was developed to search for invisible decays of positronium as a probe of physics beyond the Standard Model. The detector geometry was optimized with Geant4 simulations, and the scintillation and readout performance were evaluated experimentally. The temperature dependence of the BGO scintillator and several readout configurations were studied to find the operating condition giving the best energy resolution. The background level was then measured both at the surface and underground. At the surface, the positron-gamma coincidence background was of order 1 Hz, with occasional bursts up to about 65 Hz. Underground, it decreased to below about 3 \times 10^{-4} Hz, more than three orders of magnitude lower.
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All authors Dongwoo Jeong, Jaeyoung Cho, Doohyeok Lee, Jaehyeok Kim, HyeoungWoo Park, Yun-Tao Wu, H. J. Kim

Instrumentation and Detectors

Post-fabrication trimming of a 1024-pixel, single-photon counting, Microwave Kinetic Inductance Detector array with a pixel pitch of 150 micron

Wilbert Ras-Vinke, Hessel Schulte, David J. Thoen et al. (+5 more)

Microwave Kinetic Inductance Detectors are superconducting resonators capable of single-photon counting with energy resolving capability at visible and near-infrared wavelengths. Their zero read noise, extremely low dark counts, and compatibility with frequency-division multiplexing make them well suited for large imaging arrays. The detector yield of these arrays is often limited by the fabrication-induced frequency scatter leading to resonator collisions. We find that the tight packing of the pixels can add significant frequency scatter as well. We developed a post-fabrication correction method that is suitable for tightly packed arrays with a pixel pitch of $150\ \mathrm{\mu m}$. We demonstrate this method on a 1024-pixel array multiplexed on a single octave of readout bandwidth and show a reduction in frequency scatter from $1.1\times 10^{-2}$ to $3.5\times 10^{-4}$ and an increase in yield from $76\%$ to $94\%$.
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All authors Wilbert Ras-Vinke, Hessel Schulte, David J. Thoen, Kevin Kouwenhoven, Steven A.H. de Rooij, Tonny A.H.M. Coppens, Jochem J.A. Baselmans, Pieter J. de Visser

Instrumentation and Detectors

Development of Ultrafast and Radiation-Hard GAGG for the Next-Generation of High-Energy Physics Calorimeters

Louis Roux, Loris Martinazzoli, Julie Delenne et al. (+9 more)

The evolution of High Energy Physics (HEP) toward future collider experiments with High Luminosity (HL), such as the HL-LHC, requires the development of scintillating materials that combine high density, excellent radiation hardness and an ultrafast response. While Cerium-doped Gadolinium Aluminum Gallium Garnet (GAGG:Ce) offers a very high light yield and resilience to irradiation, its typical decay time of approximately 50-60 ns may lead to pile-up effects in high-rate environments. In this paper, we report on the development and multi-stage characterization of various accelerated GAGG compositions optimized for timing performance and grown by Crytur. By taking advantage of divalent co-doping to engineer the scintillation kinetics, we achieved an effective decay time (tau_d,eff) down to 5.5 ns while maintaining a competitive light yield of several thousand photons per MeV. Laboratory characterization demonstrates that the time resolution under gamma-ray excitation is comparable to commercial GAGG, while the time resolution measured with 120 GeV pions reaches performance levels comparable to state-of-the-art LYSO:Ce,Ca. After a 1 MGy proton irradiation campaign the material retains most of its optical transmission. The results confirm that this ultrafast GAGG composition is a viable candidate for the next generation of HEP calorimetry and timing detectors.
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All authors Louis Roux, Loris Martinazzoli, Julie Delenne, Philipp Roloff, Ondřej Zapadlík, Jan Polak, Jan Havlíček, Silvia Sýkorová, Martin Nikl, Pavel Boháček, Christophe Dujardin, Etiennette Auffray

Instrumentation and Detectors

A unified quantum electrical platform for synchronous metrological realization of volt, ohm and ampere

Lei Wang, Lushuai Qian, Yunfeng Lu et al. (+12 more)

A co-located integration quantum electrical standard is essential to reduce reliance on distributed traceability in high-accuracy metrology, especially for portable and on-site use. Metrologically, realizing any two of voltage, resistance, and current is sufficient, as the third follows from Ohm's law. The combination of Josephson voltage and quantum Hall resistance offers better uncertainty, but conflicts with the tesla-level field for quantum Hall and near-zero field for Josephson operation. Here we report a compact unified platform enabling co-realization of quantum voltage and resistance in a single cryostat near 4 K, with quantum current derived via Ohm's law. A hierarchical magnetic shielding with staged attenuation and spatial confinement allows 6 T and below 50 nT to coexist within 270 mm axial separation with negligible cross-coupling. In integrated operation, the Josephson and quantum Hall subsystems agree with expected quantized values within relative standard uncertainties of 2.6E-9 and 1.4E-8, respectively. Linking them via an improved cryogenic current comparator realizes a 50 {\mu}A quantum current with relative uncertainty of 6.6E-8. These results demonstrate that three basic electrical units can be synchronously realized with superior metrological consistency on a single integrated platform, offering a viable transition from distributed calibration chains toward compact-integrated quantum-based realization.
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All authors Lei Wang, Lushuai Qian, Yunfeng Lu, Yang Shi, Xuanlu Yang, Xiaoding Huang, Zihan Lei, Yuan Zhang, Yaqiong Fu, Junsheng Cheng, Jianhua Liu, Xinning Hu, Yinming Dai, Jianting Zhao, Qiuliang Wang

Instrumentation and Detectors

A Six-Quadrupole Diamagnetic Suspension Architecture for Ultra-Sensitive Space Accelerometry

Marco Pisani, Edoardo Dalla Ricca, Carlo Paolo Sasso et al. (+1 more)

This paper proposes a novel inertial sensor based on a solid diamagnetic cubic test mass passively suspended by a symmetric configuration of six magnetic quadrupoles. Designed specifically for microgravity environments, this system eliminates the mechanical noise and hysteresis inherent in elastic suspensions, as well as the complexity associated with electrostatic suspension systems. We provide an analysis of the magnetic intrinsic noise floor imposed by eddy current damping, alongside ground-based preliminary experimental results demonstrating potential sensitivities in the order of the $10^{-10} \text{ m/s}^2/\sqrt{\text{Hz}}$ regime.
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All authors Marco Pisani, Edoardo Dalla Ricca, Carlo Paolo Sasso, Massimo Zucco

Instrumentation and Detectors

Operation of a negative ion gas time projection chamber without electronegative fill gases

Lachlan J. McKie, Lindsey J. Bignell, Nicholas Adams et al. (+3 more)

The high fidelity reconstruction of particle tracks in micropatterned gaseous time projection chambers renders this technology ideal for future rare-event searches, including direction-sensitive dark matter experiments. Large drift distances are typically required for such experiments, so that the overall spatial resolution is limited by diffusion. Negative ion drift exhibits lower diffusion than electron drift and is thus an attractive option for realising a large-scale detector. The use of electronegative gases to create negative ions introduces technical challenges, most notably a reduction in gain when compared to conventional gas mixtures. In this study, we demonstrate a new method for negative ion generation via dissociative electron attachment using the conventional molecular fill gas CF$_4$. Our optical measurements of negative ion drift indicate electron attachment lengths of $<$1 mm and comparable gain to electron avalanches. The individual negative ion avalanches were also time-resolved, allowing the number of ions reaching the readout to be counted. We measure an improved energy resolution by single ion counting, relative to an integrated electron avalanche signal measured under identical gain conditions.
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All authors Lachlan J. McKie, Lindsey J. Bignell, Nicholas Adams, Victoria U. Bashu, Ferdos Dastgiri, Gregory J. Lane

Instrumentation and Detectors · Cross-listed from hep-ex

Extended High-Mass Axion Search with an Auxetically Tuned Higher-Order-Mode Cavity

Jinsu Kim, Sungjae Bae, Junu Jeong et al. (+9 more)

Conventional high-mass axion haloscopes based on the TM$_{010}$ mode lose detection volume as the resonant frequency increases. We report an extended axion search using a dielectric-restored TM$_{020}$ cavity haloscope with symmetry-preserving auxetic tuning based on a single-degree-of-freedom mechanical architecture. Using a near-quantum-limited microwave receiver, we searched a frequency range of 4.98-5.07 GHz and exclude axion-photon couplings with sensitivity approaching the KSVZ benchmark. Together with two earlier searches, the present scans extend a multi-scan program based on this architecture, yielding nearly 300 MHz of contiguous high-mass axion coverage over 4.98-5.27 GHz, the first broad search reported with a single higher-order-mode haloscope. This work establishes higher-order-mode cavities as a practical, scalable route beyond the TM$_{010}$ volume penalty.
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All authors Jinsu Kim, Sungjae Bae, Junu Jeong, Younggeun Kim, Jihn E. Kim, Arjan F. van Loo, Yasunobu Nakamura, Seonjeong Oh, Taehyeon Seong, Yannis K. Semertzidis, Sergey Uchaikin, SungWoo Youn

Instrumentation and Detectors

Spectral Discrimination of Deposited Gamma-Ray Energies in a Simulated CeBr$_3$ Scintillator

Andrey Elagin

We show that wavelength measurements of individual detected optical photons may provide additional information about gamma-ray energy deposited in a CeBr$_3$ crystal when the detected-photon-count distributions overlap for nearby gamma-ray energies. Monoenergetic 662 and 629 keV gammas are used in a Geant4 simulation of a $25\times25\times20~\mathrm{mm^3}$ CeBr$_3$ crystal. Assuming a light yield of $6.0\times10^4$ photons/MeV, a wavelength-independent photon-detection efficiency of 30%, and a wavelength resolution of $\sigma_{\lambda}=40$ nm, we find that the fraction of photons reconstructed above 385 nm gives an event-level separation of $\sim$ 2 standard deviations between the 662 and 629 keV event populations selected within the same $\sim$ 1%-wide detected-photon-count interval. No timing or reconstructed interaction-position information is used. The result demonstrates, within the present simulation model, that event-dependent optical spectra can retain energy information beyond an undifferentiated photon count.
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Tuesday 8 September

Instrumentation and Detectors

Development and demonstration of the Korea ALICE Telescope using electron beams at KEK PF-AR

Jiyoung Kim, Meike Danisch, Sungwoon Choi et al. (+26 more)

The development of ultra-low-mass, high-precision vertex detectors is a key requirement for future collider experiments and motivates extensive research and development of novel silicon tracking technologies. In this work, we present the development and beam-test demonstration of the Korea ALICE Telescope (KATS), a silicon-tracking telescope designed to support R&D on next-generation cylindrical vertex detectors, such as the proposed ALICE ITS3 upgrade. The telescope consists of six ALPIDE Monolithic Active Pixel Sensors (MAPS) used as reference tracking planes, a bent ALPIDE sensor serving as the device under test, and a scintillating-fiber-based trigger system, all housed in a light-tight modular enclosure. This setup enables precise track reconstruction and detailed performance studies of both planar and curved silicon sensors. Beam tests were carried out using high-energy electron beams at the KEK Photon Factory Advanced Ring (PF-AR). The telescope system operated stably under realistic beam conditions, and its tracking performance was successfully validated. The bent ALPIDE sensor was operated at a bending radius of approximately 18 mm, consistent with ITS3's design goals, without any observable degradation in detection performance. The measured results confirm that the KATS provides a versatile and reliable platform for studies of curved MAPS technologies, alignment precision, and tracking performance. These results provide important experimental validation of key technologies for future low-mass cylindrical silicon vertex detectors and establish KATS as a valuable facility for ongoing and future detector R&D.
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All authors Jiyoung Kim, Meike Danisch, Sungwoon Choi, Tatsuya Chujo, Taku Gunji, Yoonha Hong, Hangil Jang, Towa Katsuno, Ryotaro Kohara, MinJung Kweon, Sanghoon Lim, Inaba Motoi, Hikari Murakami, Hanseo Park, Jonghan Park, Shingo Sakai, Daito Shibata, Reita Wada, Kyungrim Woo, Yorito Yamaguchi, Seunghwan Yang, In-Kwon Yoo, Miljenko Suljic, Serhiy Senyukov, Giacomo Contin, Domenico Colella, Bong-Hwi Lim, Mihail-Bogdan Blidaru, Berkin Ulukutlu

Instrumentation and Detectors

Intrinsic time resolution of a hexagonal BC404 scintillator: A Monte Carlo study of interaction geometry and optical reflectivity

C. H. Zepeda-Fernández, L.F. Rebolledo-Herrera and E. Moreno Barbosa

Time resolution is an important parameter in particle detectors, as it determines their ability to distinguish between two temporally separated events. It can be decomposed into electronic and intrinsic contributions, the latter being influenced by scintillation, optical transport, detector geometry, particle type and energy, and the sensitive area of the photosensor. In this work, a Monte Carlo simulation based on Geant4 is used to investigate the intrinsic time resolution of a hexagonal BC404 plastic scintillator. The analysis includes the evaluation of the optical-photon distribution over the hexagonal surfaces and the characterization of the intrinsic time resolution for different interaction configurations. The intrinsic time resolution is investigated using muons as cosmic-ray proxies with energies ranging from 4~GeV to 1~TeV. In addition, the effect of surface reflectivity on optical-photon transport and timing performance is studied for reflectivities ranging from 0% to 100%. The results show that the intrinsic time resolution exhibits little dependence on the incident muon energy, while a clear dependence on the interaction position is observed. Furthermore, although the number of detected photons varies with the interaction position and surface reflectivity, the intrinsic time resolution is not solely determined by photon statistics, indicating that optical transport and geometrical effects play an important role in the timing performance. Across the investigated configurations, intrinsic time resolutions ranging from approximately 15 to 100~ps are obtained. These findings highlight the importance of the interaction position, optical transport, photon statistics, and surface reflectivity in determining the timing performance of hexagonal plastic scintillators and provide guidance for the optimization of their optical properties and geometry for timing-sensitive applications.
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Instrumentation and Detectors

Non-destructive 3D doping imaging of silicon sensors

Xiangyu Xie, Anna Bergamaschi, Maria Carulla et al. (+9 more)

Silicon sensors are the foundational detection medium for X-rays and charged particles. While their bulk dopant distribution determines device performance, it is conventionally assumed homogeneous because traditional profiling is destructive, spatially restricted, and insensitive at the relevant concentrations. Here we introduce a non-destructive 3D doping imaging technique that turns the readout electronics of a charge-integrating hybrid pixel detector into a massively parallelized capacitance-voltage profiler. With a few tens of micrometres of 3D resolution over wafer-scale areas at concentrations on the order of $10^{11}$ cm$^{-3}$, we image the bulk doping concentration of operational sensors. Macroscopically, we resolve depth-evolving concentric doping rings; microscopically, we uncover scattered doping anomalies that distort local electric fields. The rings modulate the depletion voltage, while the anomalies disrupt local charge collection, a previously overlooked cause of pixel yield and performance degradation. By bridging manufacturing signatures with microscopic defects, this approach provides a non-destructive framework for sensor characterization and yield optimization.
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All authors Xiangyu Xie, Anna Bergamaschi, Maria Carulla, Roberto Dinapoli, Erik Fröjdh, Viktoria Hinger, Davide Mezza, Aldo Mozzanica, Jonathan Mulvey, Bernd Schmitt, Saverio Silletta, Jiaguo Zhang

Instrumentation and Detectors · Cross-listed from astro-ph.IM

Full Characterisation of the Polarisation Primary Beam of the GRAO 32-m Telescope

Theophilus Ansah-Narh, Nia Imara, Benedicta Woode et al. (+4 more)

Direction-dependent instrumental polarisation is a major systematic limitation in high-fidelity single-dish radio polarimetry, yet a unified characterisation of beam leakage and the conditioning of polarisation recovery is lacking for the Ghana Radio Astronomy Observatory (GRAO) 32-m telescope. We aim to establish a quantitative, direction-dependent polarimetric beam model at 5.0 and 6.7 GHz. High-resolution GRASP electromagnetic simulations of the nominal telescope configuration are used to derive the full complex Jones response and corresponding Mueller matrices, from which beam shape, beam squint, instrumental Stokes leakage, and intrinsic cross-polarisation ratio (IXR) are evaluated across the primary beam. The Stokes $I$ beams have half-power beam widths of $396.4$ and $295.3$ arcsec at 5.0 and 6.7 GHz, respectively, with main-beam efficiencies of $56.4$ and $55.6$ per cent. At 5.0 GHz, the circular-polarisation beam squint is $9.96$ arcsec ($2.5$ per cent of the HPBW), whereas no statistically significant squint is detected at 6.7 GHz. Leakage from Stokes $I$ into linear polarisation remains below $0.1$ per cent within the half-power beam but increases substantially towards the sidelobes. IXR reaches approximately $80$ dB on axis and decreases with angular offset. These results establish the intrinsic electromagnetic polarimetric response of the GRAO 32-m telescope and provide a quantitative baseline for direction-dependent calibration and subsequent observational validation.
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All authors Theophilus Ansah-Narh, Nia Imara, Benedicta Woode, Joseph Bremang Tandoh, Emmanuel Proven Adzri, Diana Klutse, Evaristus Uzochukwu Iyida

Instrumentation and Detectors

Event-by-Event Space-Charge Gain Suppression in LGADs and Its Impact on Time Resolution

Djunes Janssens, Michael Moll and Heinrich Schindler

Low Gain Avalanche Detectors (LGADs) achieve time resolutions below 50 ps through internal charge multiplication, yet the gain is not a fixed device property as the space-charge of the multiplied electron-hole density screens the gain layer field, which suppresses further impact ionization. While TCAD simulations reproduce the average gain suppression, their deterministic treatment of a continuous charge density cannot capture the event-by-event fluctuations that determine the timing performance. We present a Monte Carlo study of space-charge-induced gain suppression in LGADs using the Garfield++ framework, in which the dynamic field of the drifting carriers, computed from a coarse-grained system of charged rings, is superimposed on TCAD-computed static field maps of Centro Nacional de Microelectrónica (CNM) and Hamamatsu Photonics (HPK) produced sensors while preserving single carrier avalanche statistics. The simulated gain reproduces published two-photon absorption-transient current technique measurements across two orders of magnitude in injected charge, including the dependence on the injection depth. For minimum ionizing particles, the event-by-event coupling between deposited charge and gain compresses the Landau tail of the multiplied charge, narrowing the signal arrival time distribution and improving the intrinsic time resolution of the HPK-S1 sensor investigated in this work from 53.9 $\pm$ 1.0 ps to 44.5 $\pm$ 0.9 ps. Treating the primary ionization as a stochastic sequence of charge clusters, it is further shown analytically that any gain suppression that decreases with the cluster size narrows the centroid time distribution.
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Instrumentation and Detectors · Cross-listed from hep-ex

Readout electronics for SUBMET

Claudio Campagnari, Sungwoong Cho, Suyong Choi et al. (+20 more)

A dedicated data acquisition (DAQ) system has been developed for the SUB-Millicharge ExperimenT (SUBMET) at the Japan Proton Accelerator Research Complex (J-PARC), a search for particles carrying a fractional electric charge $Q = \epsilon e$ with $\epsilon$ below $\mathcal{O}(10^{-3})$, hereafter referred to as millicharged particles (mCPs). Because such particles are expected to produce at most a few scintillation photons, the system is optimized for single-photoelectron detection from the photomultiplier tubes (PMTs), combining high-speed waveform digitization with precise timing. To capture eight consecutive proton bunches of the 30 GeV J-PARC beam within a single trigger, the eight channels of the Domino Ring Sampler 4 (DRS4) chip are cascaded in groups of four to form two readout inputs, each sampling 4096 points continuously at 820.5 MHz over an effective time window of 5 us. After calibration, timing differences between channels are within 1 ns on the same DRS4 chip, 2 ns on the same board, and 8 ns across different boards, well within the 30 ns coincidence window of the experiment. The front-end electronics achieve an RMS noise below 0.4 mV. The baseline is deliberately offset upward such that the negative-going pulses span a larger fraction of the digitizer range, improving voltage resolution and dynamic range. A trigger control board aggregates data from multiple readout boards and sustains the data-transfer rate required for beam operation. The measured performance confirms that the DAQ system meets the timing, noise, and throughput requirements of the experiment.
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All authors Claudio Campagnari, Sungwoong Cho, Suyong Choi, Seokju Chung, Matthew Citron, Albert De Roeck, Martin Gastal, Seungkyu Ha, Andy Haas, Christopher Scott Hill, Insung Hwang, Hoyong Jeong, Jaebak Kim, Jeonghwa Kim, Hyunki Moon, Ryan Schmitz, David Stuart, Eunil Won, Jae Hyeok Yoo, Jinseok Yoo, Ayman Youssef, Ahmad Zaraket, Haitham Zaraket

Monday 7 September

Instrumentation and Detectors · Cross-listed from hep-ex

Solid-state nuclear magnetic resonance search for axion-like dark matter with broadband SQUID magnetometry

Andrew J. Winter, János Ádám, Deniz Aybas et al. (+5 more)

We report the results of an experimental search for ultralight axion-like dark matter in the mass ranges 19.5–20.5 and 21.5–22 neV. The Cosmic Axion Spin Precession Experiment-electric probes the axion-nuclear electric dipole moment coupling. We perform solid-state nuclear magnetic resonance on $^{207}$Pb spin ensembles which reside in a polarized ferroelectric crystal. The background axion-like dark matter field induces an oscillating torque on the $^{207}$Pb spins via the electric dipole moment coupling $g_{d}$. The experiment is calibrated with pulsed magnetic resonance measurements covering two frequency bands (4.6–5.0 and 5.2–5.3 MHz) that correspond to the axion Compton frequencies associated with the identified axion mass ranges. By sweeping the leading magnetic field applied to the sample, we are able to detect the $^{207}$Pb nuclear magnetic resonance in these frequency ranges using a superconducting quantum interference device, inductively coupled to the sample with a broadband circuit. We establish the upper bounds $|g_{d}| < 4\times 10^{-4}$ GeV$^{-2}$ with 95% confidence in these frequency bands. Our results demonstrate the detection and small-tip angle calibration of low-field $^{207}$Pb nuclear magnetic resonance, allowing for sensitivity to axion-like dark matter in the nanoelectron-volt axion mass range.
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All authors Andrew J. Winter, János Ádám, Deniz Aybas, Dmitry Budker, Derek F. Jackson Kimball, Surjeet Rajendran, Arne Wickenbrock, Alexander O. Sushkov

Instrumentation and Detectors

Real-time blind indexing by cross-frame consensus

Stefano Marchesini and Yuan Ni

Classical crystallography determines orientation and unit-cell geometry from a rotation series collected from a single specimen, whereas serial crystallography acquires one still exposure from each of many randomly oriented microcrystals and must reconstruct a complete dataset by pooling partial measurements across the ensemble. In serial experiments, each frame typically contains only a subset of reflections, and frames with few reliable peaks (the small-N regime) are especially difficult to index blindly, because multiple incorrect lattices or orientations can explain sparse observations. The approach implemented in GLINT addresses this small-N regime by treating the dataset, rather than the individual frame, as the unit of inference. Candidate solutions are generated for many frames, weak but recurrent lattice hypotheses are pooled across the ensemble to identify a shared unit cell, and each frame is then registered against that consensus cell through a known-cell orientation search with lower dimensionality than blind indexing. In benchmark tests, GLINT matched the strongest blind indexer in the comparison on indexing yield at roughly 40x lower per-frame blind-indexing latency against XGANDALF's fastest configuration, and batched known-cell registration ran entirely on one GPU, allowing cell discovery on the fly during serial data collection. On experimental serial data, frames indexed blind by GLINT merged to crystallographic quality (CC* = 0.90), while the method rejected non-crystal images rather than forcing unsupported indexing assignments. These results demonstrate that indexing performance can be evaluated not only by indexing yield and throughput, but also by the quality of the resulting merged crystallographic data.
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Instrumentation and Detectors · Cross-listed from hep-ex

Reducing simulation-related emissions in rare-event searches through optimised event biasing

P. Knights, L. J. Milligan and K. Nikolopoulos

Rare-event search experiments continue to extend their sensitivities to unprecedented levels. This requires increasingly small backgrounds, and shielding schemes that can suppress external backgrounds by several orders of magnitude. Moreover, detailed simulations are required to attain a good understanding of these experimental backgrounds. Studies have suggested, however, that simulations and computing-related tasks contribute approximately 10% to the average particle physicist's carbon footprint. With backgrounds frequently below 0.01 counts per kg of target per keV of energy, simulations require more computing resources; growing a rare-event researcher's computing-related carbon footprint. Event biasing is often applied in shielding simulations as a remedy, yet there is a lack of systematic guidance on how to maximally benefit from them. An optimisation study for the importance-splitting biasing technique is discussed, focused on balancing statistical precision with simulation CPU-time, and how this can benefit the average researcher's carbon footprint.
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Instrumentation and Detectors

Review of Hybrid and Opaque Scintillator Technologies Advancing Neutrino and Dark Matter Detectors

Stefan Schoppmann

Organic liquid scintillators are used since several decades, especially in neutrino physics. They excel at the detection of low-energy particles where energy and timing information is required. Organic liquid scintillators have advantages such as high light yield, radio purity, cost effectiveness, and more. However, they also exhibit disadvantages, most prominently a lack of vertex resolution and particle identification. Various novel ideas have emerged over the course of the last decade to improve the performance of organic liquid scintillators. Among them are most prominently hybrid and opaque scintillators. In this proceedings, these novel scintillators are reviewed and their current applications in the research fields of neutrino and dark matter physics are illustrated.
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Instrumentation and Detectors

Ton-scale Xenon Gas TPC for $0\nu\beta\beta$ Search at Atmospheric Pressure

Y. Mei, K. Mistry and D.R. Nygren

We explore aspects of an unorthodox ton-scale xenon gas time projection chamber detector operated at normal temperature and pressure (NTP), designed for $0\nu\beta\beta$ discovery at $\sim10^{27}$ year sensitivity. At fixed active mass, a greater transparency to $\gamma$-ray backgrounds and better track clarity exists at NTP relative to higher density. Operation at NTP also alleviates difficulties with pressure containment and significantly reduces HV requirements. With metre-scale electron tracks at a few MeV, event topology can be used to efficiently reject the copious $\gamma$-ray backgrounds by factors ranging from 550–1200, largely compensating for the greater surface area of the detector. Event topology is captured from anode plane signals combined with sensing the secondary ion component arriving at the cathode plane. A molecular gas additive limits diffusion of the secondary electron tracks to below a cm and provides stable proportional avalanche gain. An energy resolution $\delta$E/E $\leq$ 1% FWHM seems possible. A 100 kg scale demonstrator for this detector technology could lead directly to a ton-scale search.
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Sunday 6 September

Instrumentation and Detectors · Cross-listed from physics.acc-ph

Preliminary design of continuous wave Low-Level RF systems for S3FEL

Z. Y. Zhang, J. F. Zhu, H. L. Ding et al. (+4 more)

In the Shenzhen Superconducting Soft X-ray Free Electron Laser (S3FEL), Continuous Wave (CW) Low-Level Radio Frequency (LLRF) systems perform critical functions including adjusting the power coupling of accelerator cavities, regulating the amplitude and phase of the RF field, and maintaining the resonance frequency and phase of the cavities. These functions are essential to ensure the electron beam operates at the accelerating phase. Within S3FEL, each superconducting cavity is driven by a solid-state amplifier (SSA), with each SSA paired with a dedicated LLRF system. Based on the distinct acceleration cavities employed, the CW LLRF systems for S3FEL are categorized into four types: 1. Primary accelerator LLRF systems (superconducting, 1.3 GHz; quantity: 168), 2. Harmonic cavity LLRF systems (superconducting, 3.9 GHz; quantity: 16), 3. VHF electron gun LLRF systems (room temperature, 216 MHz; quantity: 4), 4. Buncher LLRF systems (room temperature, 1.3 GHz; quantity: 2). These four LLRF system categories exhibit differing requirements for RF field and acceleration cavity control. This report presents the preliminary design schemes for these four types of CW LLRF systems.
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All authors Z. Y. Zhang, J. F. Zhu, H. L. Ding, J. W. Han, W. Li, J. Y. Yang, W. Q. Zhang

Saturday 5 September

Instrumentation and Detectors

EBS and in-beam $\gamma$-ray investigation of FCVA-prepared Cr$_2$O$_3$ targets for low-energy $^{16}$O+$^{16}$O fusion experiments

C. Wen, X. Chen, L. Wang et al. (+22 more)

The Cr$_2$O$_3$ solid target for low-energy $^{16}$O+$^{16}$O fusion experiments was fabricated using filtered cathodic vacuum arc (FCVA) deposition. Its composition, oxygen areal density and impurity content were characterized by elastic backscattering spectrometry (EBS), and the impurity-induced background contributions were investigated by in-beam $\gamma$-ray spectroscopy. EBS results indicate that the Cr$_2$O$_3$ film exhibits good stoichiometry and uniformity, with $^{16}$O areal densities ranging from $(3.24-3.25)\times10^{17}$ atoms/cm$^2$. The EBS analysis reveals a carbon atomic fraction of approximately 1.25-1.29% in the Cr$_2$O$_3$ layer, while a large amount of carbon impurities are also identified on the surface of Cr substrate. In-beam $\gamma$-ray spectra reveal prominent transitions associated with $^{27}$Al and $^{24}$Mg at 844, 1015, and 1369 keV, mainly originating from $^{12}$C+$^{16}$O fusion reactions induced by carbon impurities under $^{16}$O irradiation. Meanwhile, characteristic $\gamma$-rays emissions from evaporation channels of the $^{16}$O+$^{16}$O reaction, including $^{31}$S, $^{31}$P, and $^{28}$Si, were also observed and can be used to extract the $^{16}$O+$^{16}$O fusion cross sections. This work provides an experimental basis for the development of high-purity oxide targets and the optimization of target configurations for future low-background $^{16}$O+$^{16}$O fusion cross section measurements.
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All authors C. Wen, X. Chen, L. Wang, Z. An, F. Bai, Y. Chen, X. Fang, Y.X. Fan, B.S. Gao, Z.Y. Guo, J.F. Han, H.T. Hu, W.P. Lin, B. Liao, S. Lin, G. Liu, X.Q. Liu, P.P. Ren, J. Su, J.H. Tan, X.D. Tang, P. Wang, S. Wang, D.H. Xie, N.T. Zhang

Instrumentation and Detectors

Simulation Study of the Design and Spatial Resolution of a Novel AC-coupled Cross Strip LGAD

Jingkang Xu, Mengzhao Li, Zhiliang Hu et al. (+5 more)

AC-coupled Low Gain Avalanche Diode (AC-LGAD), evolved from the standard LGAD technology, are silicon detectors characterized by exceptional temporal and spatial resolutions. This work proposes a novel sensor named AC-coupled Cross Strip LGAD (CS-LGAD) structure with dual-layered overlapping strip electrodes. It can achieve two-dimensional particle position measurement with low readout density while also inheriting the high temporal resolution of the LGAD. The sensor structure, doping and current-voltage (I-V) characteristics of the sensor were investigated through TCAD simulations. Additionally, Monte Carlo simulations were employed to simulate the signal response of CS-LGAD to minimum ionizing particles (MIPs). The response of MIPs hitting different positions was simulated, and the reconstruction of particle coordinates (x and y) was achieved based on the sharing of charges on the dual-layer electrodes. The spatial resolution might reach 3.6% and 5.5% of the pitch size in the x and y directions, respectively, according to the simulation. The proposed CS-LGAD is a promising 4D detector with low mass and low readout density.
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All authors Jingkang Xu, Mengzhao Li, Zhiliang Hu, Tianya Wu, Mei Zhao, Zhijun Liang, Lihua Mo, Tianjiao Liang

Instrumentation and Detectors

Long-term performance of non-ALD MCP-PMTs in the high-radiation environment of ALICE

Yury Melikyan for the ALICE Collaboration

The Fast Interaction Trigger detector of the ALICE apparatus at the LHC includes a Cherenkov subsystem utilizing 52 Planacon XP85002/FIT-Q microchannel plate-based photomultiplier tubes. It is a precise trigger, multiplicity and luminosity detector located in the forward region, where the flux of collision products is the largest. The photon load reaches up to 2*10^8 photoelectrons / cm^2 / s for the innermost photosensors, corresponding to 0.4 {\mu}A / cm^2 average anode current density. The lifetime-extended version of the Planacon MCP-PMT with atomic layer deposition cannot handle such a large anode current. We therefore use the non-ALD version of the Planacons that, on the other hand, suffer from a limited lifetime in terms of the integrated anode charge. Here we present the long-term performance trends of the non-ALD Planacons up to the integrated anode charge of 2 C / cm^2. We demonstrate that the low-gain operation strategy allows to maintain excellent time resolution in multiphoton mode unchanged up to that large integrated charge. While the majority of the equally illuminated MCP-PMTs feature almost identical ageing speed, two outliers suffering from a faster ageing coincide with the outliers in the noise characteristics measured prior to the irradiation. Moreover, we report that the effective ageing speed is partially suppressed by the self-recovery of the response of aged MCP-PMTs newly observed by our group during months-long no-beam periods.
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Instrumentation and Detectors

An optical cryostat for automated testing of silicon photomultipliers with vacuum-ultraviolet light

Lucas Darroch, Riya Rai, Soud Al Kharusi et al. (+8 more)

We present the design and performance of an optical cryostat for testing silicon photomultipliers (SiPMs) with vacuum-ultraviolet (VUV) light. The cryostat operates within a temperature range of 120 to 340 K, achieving a temperature stability of 1.2 mK, measured in a rolling 10-minute window once settled within a liquid nitrogen fill-cycle, and 13.8 mK over a complete fill-cycle including the refill transient. The cryostat includes a VUV-transparent CaF$_2$ viewport with a 142 mm diameter clear aperture, which limits the optically accessible sample area to 158 cm$^2$. The viewport is integrated into a sealed dark box and optical table to facilitate light delivery. VUV illumination is achieved using a custom xenon scintillation lamp or a xenon flash lamp, with a motorized two-axis linear rail system ensuring precise light positioning over the sample. This paper details the cryostat and optical system design, as well as commissioning current-voltage (IV) measurements using Hamamatsu VUV-sensitive SiPMs from 165 to 295 K and a measurement of the photodetection efficiency at 165 K.
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All authors Lucas Darroch, Riya Rai, Soud Al Kharusi, David Gallacher, Megan Marquis, Sebastian Eppelt, Iskender Isikbay, Xiao Shang, Tsvetelin Totev, Naman Walia, Thomas Brunner

Friday 4 September

Instrumentation and Detectors

Kinematic Fitting of electromagnetic calorimeter data - an improved method

Nicolas Kolanus, Jonas Kohlen and Ulrike Thoma

Kinematic fitting is widely used in particle physics experiments as a powerful tool to improve experimental resolutions, to suppress background and to provide selection criteria for the identification of specific reactions. Kinematic fitting methods, however, typically assume that the fitted quantities follow Gaussian distributions; an assumption which does not always hold. This is particularly true for energy measurements from electromagnetic calorimeters. This issue can largely be overcome by performing a transformation of the non-Gaussian variables into variables which follow a Gaussian distribution. The new adapted kinematic fitting procedure allows to better account for the non-Gaussian nature of the measured calorimeter energies, at the same time improving the accuracy and robustness of the kinematic fit. This leads to improved pull and confidence-level distributions of the kinematic fit as well as improved invariant mass distributions and signal-to-background ratios in the final event sample.
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Instrumentation and Detectors

The DarkLight Experiment at TRIUMF

R. Alarcon, D. Almonte, M.I. Alstaty et al. (+60 more)

This paper reports on the commissioning of the DarkLight experiment at the ARIEL superconducting electron linear accelerator located at TRIUMF in Vancouver, Canada. DarkLight was designed to utilize the ARIEL electron beam to search for a new boson, $A^\prime$, which preferentially couples to leptons, with a mass in the range 13-17 MeV/$c^2$. Such a boson could be produced via the $e^-~X\rightarrow e^-~X~A^\prime$ process, and the resulting $A^\prime\rightarrow e^+~e^-$ decay used to reconstruct the invariant mass of the $A^\prime$. The $e^+e^-$ pair is detected using a pair of magnetic spectrometers. Each spectrometer is instrumented with two triple GEM detectors and a scintillating strip hodoscope to trigger the event readout. Electron beam energies between 10 and 30 MeV were used to commission the experiment with a 1$~\mu$m thick carbon target. With both spectrometer polarities set to select electrons, elastic and Møller scattering were used to examine detector performance and compare with predicted distributions from Monte Carlo simulations. Planned upgrades to the e-linac will allow searches to be made with beam energies up to 50 MeV using a 1$~\mu$m thick tantalum target.
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All authors R. Alarcon, D. Almonte, M.I. Alstaty, J. Azzi, R. Baartman, J.C. Bernauer, X. Braun, D. Ciarniello, C. Clabeaux, E.W. Cline, E. Corey, R. Corliss, W. Deconinck, A. Deshpande, J. Dilling, J. Dodge, D.H. Dongwi, C. Ekeman, E.A. Fielding, S. Frantzen, I. Friščić, G. Gelinas, S. Gelinas, K. Gill, A. Sabzevari Gonzalez, S. Gupte, D.K. Hasell, M. Hasinoff, B. Humphries, E. Ihloff, N. Jackson, D. Jayakodige, R. Kanungo J.E. Kelsey, O. Kester, M. Kohl, H.W. Koay, R. Laxdal, L. Levack, X. Li, W. Lin, C. Ma, A. Mahon, H. Merkel, J.W. Martin, L. Miller, R. Milner, K. Olchanski, K. Pachal, T. Planche, D. Preddy, S.D. Rädel, G. Randall, J. Redinger, D.A. Reiter, R. Richards, B. Scully, S. Shapiro, M. Suresh, C. Vidal, S. Wang, H. Witte, H. Yang, S. Yen

Instrumentation and Detectors

Nanoscale NMR of DNA-Functionalized Diamond Using Individual NV Centers

Erika Janitz, Konstantin Herb, Laura A. Völker et al. (+2 more)

Nuclear magnetic resonance (NMR) spectroscopy is a powerful probe of molecular structure and dynamics but typically requires large spin ensembles. Here, we demonstrate nanoscale NMR detection of fluorinated DNA using individual near-surface nitrogen-vacancy (NV) centers in diamond nanopillar waveguides under ambient conditions. We covalently tether $^{19}$F-labeled oligonucleotides to mixed nitrogen- and oxygen-terminated surfaces, localizing target spins within the nanoscale sensing volume. Probabilistic spin simulations suggest that the measured signals are consistent with those expected from a few molecules and depend strongly on NV-molecule separation, configuration, and local surface heterogeneity. These results establish a framework for NMR of surface-tethered biomolecules and identify key challenges for single-molecule structural elucidation.
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All authors Erika Janitz, Konstantin Herb, Laura A. Völker, Christian L. Degen, John M. Abendroth

Instrumentation and Detectors · Cross-listed from quant-ph

Microkelvin resolution thermometry at the nanometre scale

Jack W. Hart, Soham Pal, Julien R. E. Roth et al. (+8 more)

Accurate temperature readings of transient events at the nanometer scale are challenging due to the low sensitivity of available sensors. Nanodiamonds containing nitrogen-vacancy (NV) centers have been used for nanoscale thermometry in complex environments, including inside living cells. However, their performance has been limited by short coherence times and low photon counts. In this work, we use isotopically-purified dual-NV nanodiamonds and a bespoke quantum sensing chip to showcase an order of magnitude improvement in temperature measurement sensitivity compared with previous reports. We demonstrate robust temperature measurements with an error of 682 $\mu$K, experimental sensitivities below 50 mK/$\surd \text{Hz}$ and a shot-noise limited sensitivity of 9.6 mK/$\surd \text{Hz}$. To confirm the utility of these high-performance nanothermometers, we quantify the temperature change induced by the thermometry measurement itself, specifically the optical excitation laser used to probe the NV spin state. In addition, we observe directly at the nanometre scale the transient heating caused by the exothermic mixing of dimethyl sulfoxide in water. Sub-millikelvin resolution and millikelvin sensitivity thermometry unlock the possibility of monitoring minute thermal fluctuations in living systems and assessing catalyst performance at the nanometre scale.
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All authors Jack W. Hart, Soham Pal, Julien R. E. Roth, Katie Ninham, Abbie H. Aleksandrova, Xander Peetroons, Soumen Mandal, Oliver A. Williams, Gavin W. Morley, Mete Atature, Helena S. Knowles

Instrumentation and Detectors · Cross-listed from physics.atom-ph

Dead-zone-free free-induction-decay alkali-metal atomic magnetometer

X.-K. Wang, J. He, H.-H. Deng et al. (+2 more)

The detection dead zone is an important systematic limitation in scalar atomic magnetometers, constraining their practical utility. In this work, we demonstrate a sensitive dead zone free scalar magnetometer by integrating previously established techniques into a FID magnetometer based on Bell Bloom optical pumping. The dead zone is eliminated by inserting a reflecting mirror within a multipass cavity assisted atomic cell, which folds the optical beam into orthogonal paths. Our analysis reveals that interregion cross talk is essential for interpreting the resulted experimental signals. The sensor exhibits oscillation signal amplitude variations within a factor of three across all orientations in three dimensional space, and a field sensitivity better than 80 fT/Hz^(1/2) over the full space. We further characterize the heading error in the geomagnetic field range, where experimental results agree with theoretical predictions within 0.7 nT. Additionally, the sensor can operate in a closed loop mode by feeding back the real time frequency extracted from the FID signal to modulate the pump beam, we characterize the magnetic field slew rate of the sensor. This work paves the way towards a sensitive vector FID magnetometer.
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All authors X.-K. Wang, J. He, H.-H. Deng, W. Gao, D. Sheng

Instrumentation and Detectors · Cross-listed from physics.plasm-ph

Activated carbon-assisted anionic dye decomposition using a dual-liquid post-double dielectric barrier discharge plasma reactor

Krishna V S, Surya and Mangilal Choudhary

Non-thermal Plasma (NTP) technology, including the Dielectric Barrier Discharge (DBD) reactor, has emerged as an effective advanced oxidation process (AOP) for treating persistent organic pollutants in industrial wastewater. Based on this objective, a dual-liquid dielectric-barrier-discharge plasma reactor was built and used to degrade a ternary anionic dye mixture comprising Reactive Red 120, Congo Red, and Methyl Orange in its post-discharge configuration. The adjustable length of the outer liquid electrode (grounded) provides flexibility in controlling the discharge length and cooling, thereby achieving higher degradation efficiency and greater reactor stability. The conducting-liquid high-voltage electrode (a dielectric tube filled with a conductive solution) helps mitigate metal corrosion and oxidation caused by reactive species in the discharge zone. A detailed study of the degradation of ternary anionic dye mixtures (simulated dye wastewater samples) in the presence of activated carbon (AC) was performed to explore the potential applications of post-discharge treatment. The activated carbon (granules) enhances the degradation rate of ternary anionic dye mixtures in basic solutions rather than in acidic or neutral solutions. A comparative study of the degradation reaction kinetics of the ternary anionic dye mixtures in acidic and basic solutions was conducted after analyzing UV-Vis absorption spectra. The role of other parameters, such as solution pH, the mass and size of AC particles, dye concentrations, and AC reuse, was investigated in relation to degradation efficiency. The degradation mechanism was elucidated by the formation of strong oxidizer (hydroxyl radicals) on the surface of activated carbon during post-discharge treatment. However, in acidic or neutral anionic dye solutions, the degradation mechanism was dominated by ozone.
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