arXiv subjects

Martin Rongen

Publications and source records attributed to Martin Rongen.

15 recordsLinked to original sources

arXiv2025

A co-deployed dust-logging instrument for the IceCube Upgrade and IceCube-Gen2

A precise understanding of the optical properties of the instrumented Antarctic ice sheet is crucial to the performance of optical Cherenkov telescopes such as the IceCube Neutrino Observatory and its planned successor, IceCube-Gen2. One complication arising from the large envisioned footprint of IceCube-Gen2 is the larger impact of the so-called ice tilt. It describes the undulation of ice layers of constant optical properties within the detector. In this contribution, we will describe the project to build a co-deployed laser dust logger. This is a device to measure the stratigraphy of impurities in the ice to derive the ice tilt. It consists of a light source that will be co-deployed with the photosensor modules, meaning it is part of the deployment string and operated during the deployment of the detector. The newly developed device will be tested during the deployment of the IceCube Upgrade in the 2025/26 austral summer to pave the way for IceCube-Gen2.

astro-ph.IM↗

arXiv2025

Very Late Afterpulses and Search for the Neutron Echo in IceCube

While high-energy astrophysical neutrinos are well-established, their flavor composition remains relatively unconstrained. In IceCube, long muon tracks from $ν_μ$ charged-current interactions are easily identified but the detector geometry does not allow sufficient resolution to distinguish cascade-type events. The Neutron Echo - a delayed light signal in the detector from neutron capture and de-excitation - can probe the shower's hadronic content and thus the underlying interaction. A significant background arises from late PMT afterpulses, which are temporally coincident with the physics signal. The traditional IceCube data acquisition system has a limited readout window with significant deadtime between triggers, which is insufficient to capture the late pulses. A recently developed deadtime-free readout mode, with an extended window, enables their detection. An observed excess in the delayed time spectrum over the background would be compatible with the Neutron Echo hypothesis. In this contribution, we summarize the physics scope of delayed signals, discuss the timing spectrum of signal and PMT background, highlight the capabilities of the new system for recording late pulses, and emphasize the potential of IceCube for particle identification through delayed signals.

astro-ph.HE↗

arXiv2025

Mapping the ice stratigraphy in IceCube using camera deployment footage

The IceCube Neutrino Observatory is a cubic-kilometer Cherenkov array deployed in the deep, glacial ice at the geographic South Pole. An important feature of the instrumented ice are undulations of layers of constant optical properties over the footprint of the detector. During detector construction, these layers were mapped using stratigraphy measurements obtained from a stand-alone laser dust logger. While this system is very precise, its cost does not scale to the instrumented volume envisioned for the proposed IceCube-Gen2 Observatory. Here, we explore the possibility of obtaining equivalent stratigraphy data from camera footage recorded during the deployment of IceCube more than a decade ago. If successful, this could be an alternative technique to be considered for IceCube-Gen2.

astro-ph.HE↗

arXiv2025

State of the Ice Model in the IceCube Observatory

IceCube is a neutrino observatory located at the South Pole that uses Antarctic ice as a medium for detection of Cherenkov photons. As such, analysis of the data relies on our understanding of the properties of ice within and around the instrumented volume. Over the years we have made significant progress in understanding the glacial ice and now have a comprehensive model that covers many of the relevant aspects of the photon propagation in it. In this report we give a historical overview of the ice description within the IceCube detector, list some of the remaining issues, and assess how much more improvement is still needed. As the IceCube Upgrade is expected to be installed in less than a year, with several new types of calibration devices aiming to further our understanding of ice, this is the perfect time to review the current state of the ice model.

astro-ph.HE↗

arXiv2025

Resolution Limiting Factors in Low-Energy Cascade Zenith Angle Reconstruction with the IceCube Upgrade

The IceCube Neutrino Observatory includes low energy extensions such as the existing DeepCore subarray and the upcoming IceCube Upgrade, which will consist of seven new strings of photosensors with denser instrumentation than the existing array. The setup will allow for the study of neutrino oscillations with greater sensitivity compared to the existing instrumentation, improve neutrino mass ordering studies, and test for the unitarity of the PMNS mixing matrix with high precision. A critical component in these low-energy physics analyses is the accurate reconstruction of event information, particularly the zenith angle of incoming neutrinos. In this study, we discuss the processes that limit the zenith resolution, which include the transverse spread of the hadronic shower, in-ice photon scattering, module resolutions, and module noise. By considering approximations to these processes, we aim to approach the intrinsic zenith resolution limits for purely hadronic events.

physics.ins-det↗

arXiv2023

Refining the IceCube detector geometry using muon and LED calibration data

The IceCube Neutrino Observatory deployed 5160 digital optical modules (DOMs) on 86 cables, called strings, in a cubic kilometer of deep glacial ice below the geographic South Pole. These record the Cherenkov light of passing charged particles. Knowledge of the DOM positions is vital for event reconstruction. While vertical positions have been calibrated, previous in-situ geometry calibration methods have been unable to measure horizontal deviations from the surface positions, largely due to degeneracies with ice model uncertainties. Thus the lateral position of the surface position of each hole is to date in almost all cases used as the lateral position of all DOMs on a given string. With the recent advances in ice modeling, two new in-situ measurements have now been undertaken. Using a large sample of muon tracks, the individual positions of all DOMs on a small number of strings around the center of the detector have been fitted. Verifying the results against LED calibration data shows that the string-average corrections improve detector modeling. Directly fitting string-average geometry corrections for the full array using LED data agrees with the average corrections as derived from muons where available. Analyses are now ongoing to obtain per-DOM positions using both methods and in addition, methods are being developed to correct the recorded arrival times for the expected scattering delay, allowing for multilateration of the positions using nanosecond-precision propagation delays.

astro-ph.HE↗

arXiv2023

A model independent parametrization of the optical properties of the refrozen IceCube drill holes

The IceCube Neutrino Observatory deployed 5160 digital optical modules (DOMs) in a cubic kilometer of deep, glacial ice below the geographic South Pole, recording the Cherenkov light of passing charged particles. While the optical properties of the undisturbed ice are nowadays well understood, the properties of the refrozen drill holes still pose a challenge. From camera observations, we expect a central, strongly scattering column shadowing a part of the DOMs' sensitive area. In MC simulation, this effect is commonly modeled as a modification to the DOMs' angular acceptance curve, reducing the forward sensitivity of the DOMs. The associated uncertainty is a dominant detector systematic for neutrino oscillation studies as well as high-energy cascade reconstructions. Over the years, several measurements and fits of the drill holes' optical properties and of the angular acceptance curve have been proposed, some of which are in tension. Here, we present a principle component analysis, which allows us to interpolate between all suggested scenarios, and thus provide a complete systematic variation within a unified framework at analysis level.

astro-ph.HE↗

arXiv2023

An improved mapping of ice layer undulations for the IceCube Neutrino Observatory

A precise understanding of the optical properties of the instrumented Antarctic ice sheet is crucial to the performance of the IceCube Neutrino Observatory, a cubic-kilometer Cherenkov array of 5,160 digital optical modules (DOMs) deployed in the deep ice below the geographic South Pole. We present an update to the description of the ice tilt, which describes the undulation of layers of constant optical properties as a function of depth and transverse position in the detector. To date, tilt modeling has been based solely on stratigraphy measurements performed by a laser dust logger during the deployment of the array. We now show that it can independently be deduced using calibration data from LEDs located in the DOMs. The new fully volumetric tilt model not only confirms the magnitude of the tilt along the direction orthogonal to the ice flow obtained from prior dust logging, but also includes a newly discovered tilt component along the flow.

astro-ph.HE↗

arXiv2022

The Wavelength-shifting Optical Module

The Wavelength-shifting Optical Module (WOM) is a novel photosensor concept for the instrumentation of large detector volumes with single-photon sensitivity. The key objective is to improve the signal-to-noise ratio which is achieved by decoupling the photosensitive area of a sensor from the cathode area of its photomultiplier tube (PMT). The WOM consists of a transparent tube with two PMTs attached to its ends. The tube is coated with wavelength-shifting paint absorbing ultra-violet photons with nearly $100\,\%$ efficiency. Depending on the environment, e.g. air (ice), up to $73\,\%$ $(41\,\%)$ of the subsequently emitted optical photons can be captured by total internal reflection and propagate towards the PMTs where they are recorded. The optical properties of the paint, the geometry of the tube and the coupling of the tube to the PMTs have been optimized for maximal sensitivity based on theoretical derivations and experimental evaluations. Prototypes were built to demonstrate the technique and to develop a reproducible construction process. Important measurable characteristics of the WOM are the wavelength dependent effective area, the transit time spread of detected photons and the signal-to-noise ratio. The WOM outperforms bare PMTs especially with respect to the low signal-to-noise ratio with an increase of a factor up to 8.9 in air (5.2 in ice). Since the gain in sensitivity is mostly in the UV-regime, the WOM is an ideal sensor for Cherenkov and scintillation detectors.

astro-ph.IM↗

arXiv2021

Advances in IceCube ice modelling and what to expect from the Upgrade

The IceCube Neutrino Observatory instruments about 1 km$^3$ of deep, glacial ice at the geographic South Pole using 5160 photomultipliers to detect Cherenkov light from relativistic, charged particles. Most IceCube science goals rely on precise understanding and modelling of the optical properties of the instrumented ice. A peculiar light propagation effect observed by IceCube is an anisotropic attenuation, which is aligned with the local flow of the ice. Recent efforts have shown this effect is most likely due to curved photon trajectories resulting from the asymmetric light diffusion in the birefringent polycrystalline microstructure of the ice. This new model can be optimized by adjusting the average orientation, size and shape of the ice crystals. We present the parametrization of the birefringence effect in our photon propagation simulation, the fitting procedures and results. The anticipated potential of calibration instrumentation in the upcoming IceCube Upgrade to improve on known shortcomings of the current ice modelling is also discussed.

astro-ph.IM↗

arXiv2021

The Wavelength-shifting Optical Module (WOM) for the IceCube Upgrade

The Wavelength-shifting Optical Module (WOM) is a novel optical sensor that uses wavelength shifting and light guiding to substantially enhance the photosensitive area of UV optical modules. It has been designed for the IceCube Upgrade, a seven-string extension of the IceCube detector planned for the 2022/2023 South Pole deployment season. The WOM consists of a hollow quartz cylinder coated in wavelength shifting paint which serves as detection area and has two photomultipliers (PMTs) attached to the end faces. The light-collecting tube increases the effective photocathode area of the PMTs without producing additional dark current, making it suitable for low-signal, low-noise applications. We report on the design and performance of the WOM with a focus on the 12 modules in production for deployment in the IceCube Upgrade. While the WOM will be deployed in IceCube, its design is applicable to any large-volume particle detector based on the detection of Cherenkov light.

astro-ph.HE↗

arXiv2021

A Novel Microstructure-Based Model to Explain the IceCube Ice Anisotropy

The IceCube Neutrino Observatory instruments about 1 km$^3$ of deep, glacial ice at the geographic South Pole using 5160 photomultipliers to detect Cherenkov light of charged relativistic particles. Most of IceCube's science goals rely heavily on an ever more precise understanding of the optical properties of the instrumented ice. A curious light propagation effect observed by the experiment is an anisotropic attenuation, which is aligned with the local flow of the ice. Having recently identified curved photon trajectories resulting from asymmetric light diffusion in the birefringent polycrystalline microstructure of the ice as the most likely underlying cause of this effect, work is now ongoing to optimize the model parameters (effectively deducing the average crystal size and shape in the detector). We present the parametrization of the birefringence effect in our photon propagation simulation, the fitting procedures and results as well as the impact of the new ice model on data-MC agreement.

astro-ph.HE↗

arXiv2019

Calibration of the IceCube Neutrino Observatory

The IceCube Neutrino Observatory instruments roughly one cubic kilometer of deep, glacial ice below the geographic South Pole with 5160 optical sensors to register the Cherenkov light of passing relativistic, charged particles. Since its construction was completed in 2010, a wide range of analyses has been performed. Those include, among others, the discovery of a high energetic astrophysical neutrino flux, competitive measurements of neutrino oscillation parameters and world-leading limits on dark matter detection. With ever-increasing statistics the influence of insufficiently known aspects of the detector performance start to limit the potential gain of future analyses. This thesis presents calibration studies on both the hardware characteristics as well as the optical properties of the instrumented ice. Improving the knowledge of the detector systematics and the methods to study them does not only aid IceCube but also inform the design of potential future IceCube extensions.

astro-ph.IM↗

arXiv2019

Light diffusion in birefringent polycrystals and the IceCube ice anisotropy

The IceCube Neutrino Observatory instruments about 1 km^3 of deep, glacial ice at the geographic South Pole with 5160 photomultipliers to detect Cherenkov light from charged relativistic particles. The experiment pursues a wide range of scientific questions ranging from particle physics such as neutrino oscillations to high-energy neutrino astronomy. Most of these efforts rely heavily on an ever more precise understanding of the optical properties of the instrumented ice. An unexpected light propagation effect, observed by the experiment, is an anisotropic attenuation, which is aligned with the local flow of the ice. The exact cause is still under investigation. In this contribution, the micro-structure of ice as a birefringent polycrystal is explored as the cause for this anisotropy.

astro-ph.HE↗

arXiv2018

Design and evaluation of a versatile picosecond light pulser

Many experimental setups, such as for the calibration of photosensors, require light sources with sub-nanosecond timing precision. We present the design and evaluation of a brightness controlled, picosecond light pulser based on an avalanche transistor pulse driving circuit. It can be used with a large variety of LEDs and VCSELs, enabling usage over a wide wavelength range, with light curves as short as ~100 ps standard deviation.

physics.ins-det↗