arXiv subjects

Hans Th. J. Steiger

Publications and source records attributed to Hans Th. J. Steiger.

10 recordsLinked to original sources

arXiv2026

Development and validation of a forward 0.7--4 MeV quasi-monoenergetic neutron capability at the CN Van de Graaff of LNL

The CN Van de Graaff accelerator of INFN--LNL provides forward-angle quasi-monoenergetic neutrons in the 0.7--4 MeV range via the 7Li(p,n)7Be reaction on thin metallic lithium targets. This work describes the development and experimental validation of this forward neutron capability, combining comparisons of commonly used transport tools with time-of-flight (ToF) measurements. Neutron yields calculated with EPEN, FLUKA, MCNPX, and PINO are compared over the CN energy range in order to assess model-dependent variations relevant for fluence estimates. For zero incident-energy spread, a mutually consistent set of transport calculations agrees within 5% and is used as a practical reference for normalisation. The effect of incident-energy convolution on the predicted yields is examined. Time-of-flight measurements performed using a sub-nanosecond secondary pulsing system verify the timing structure and forward-angle kinematics of the quasi-monoenergetic neutron component at the detector position, with neutron arrival times consistent with the expected forward kinematics within the experimental resolution. Using measured proton currents and transport calculations based on this reference set, forward neutron fluences at the device position are estimated with an overall uncertainty of approximately 9%, including contributions from current integration, target thickness, and geometry. A short device irradiation, carried out in parallel with the ToF campaign, demonstrates measurable response under CN beam conditions and confirms the practical usability of the beam for low-MeV neutron studies. Together, these results establish the current operational performance of the CN 0° forward quasi-monoenergetic neutron capability in the 0.7--4 MeV range and identify the steps required toward routine calibrated operation.

physics.ins-det↗

arXiv2026

Doping of a Borexino-like Liquid Scintillator with Tellurium-Diols

One promising approach for future neutrinoless double beta decay ($0νββ$) searches is the incorporation of candidate isotopes into liquid scintillator detectors. In this work, a sample of the high-performance 1,2,4-trimethylbenzene-based liquid scintillator used in the Borexino experiment was loaded with different concentrations of Te-diol compounds. To realize the loading, a modified water-free synthesis procedure in a non-acidic organic environment at room temperature was employed. The loaded scintillator mixtures were characterized with respect to their emission spectra, optical absorbance, light yield, and scintillation time profiles under $α$ excitation. Within the experimental uncertainties, only comparatively small changes in the spectral emission shape and optical transmission were observed for Te-loadings up to 2\%. At the same time, a systematic reduction of the scintillation light yield with increasing Te concentration was measured. At 1\% Te-loading, an estimated light yield of approximately 8400\,photons/MeV$_{\mathrm{ee}}$ was obtained. Furthermore, the scintillation time profile measurements indicate systematically shorter effective decay time constants for increasing Te-loading, consistent with enhanced non-radiative de-excitation processes introduced by the Te-diol complexes. Overall, the results demonstrate that the investigated loading technique can be successfully applied to a pseudocumene-based liquid scintillator while preserving the principal scintillation characteristics of the system.

physics.ins-det↗

arXiv2026

Picosecond laser test unit for photosensor characterization at ambient and low temperatures

Accurate single photoelectron (SPE) characterization of photosensors is essential for controlling systematic uncertainties in low-light neutrino and dark matter detectors. We present a compact laboratory setup for the characterization of photosensors under controlled, low-light conditions. Specifically, we demonstrate its use with photomultiplier tubes (PMTs) operated at the SPE-level, using picosecond laser pulses and waveform digitization to determine key PMT properties. Measurements as a function of supply voltage and temperature ($-50^\circ$C to $+20^\circ$C) are performed on ET Enterprises 9821(Q)B tubes and a Hamamatsu R9980 assembly, which show exponential gain-voltage behavior and device-to-device variation. Cooling increases the gain by $\sim 0.1\,\%/^\circ$C, while the transit time spread (TTS) and peak-to-valley ratio (P/V) exhibit no clear temperature dependence. TTS decreases with voltage. Late pulses remain at the percent level and prepulses at the sub-percent level. Cable length affects both apparent gain and TTS. A model-independent, data-driven self-convolution method is introduced to quantify double photoelectron contributions from pulse charge spectra. The procedures provide a reproducible, practice-oriented reference for SPE-level PMT characterization and can be extended to other photosensor types.

physics.ins-det↗

arXiv2024

PALM -- Precision Attenuation Length Measurement in Liquid Scintillators

Future neutrino experiments at low energies such as JUNO or THEIA will use large volume homogeneous liquid scintillator detectors. The optical attenuation length of the liquid is of uttermost importance for the successful realization of these experiments. At TU Munich a new optical spectrometer (Precision Attenuation Length Measurement (PALM)) has been set up in order to measure the light attenuation of liquids which can be used for these types of experiments up to around 100 m in the wavelength region between 400 nm and 1000 nm. The setup features an optical imaging system with a long focal length, which allows for in-situ monitoring of the beam stability during the measurement. The setup capability as well as the reproducibility of its results has been demonstrated at two different wavelengths of 430 nm and 500 nm.

physics.ins-det↗

arXiv2024

Development, Characterization and Production of a novel Water-based Liquid Scintillator based on the Surfactant TRITON X-100

Water-based Liquid Scintillator (WbLS) is a novel detector medium for particle physics experiments. Applications range from the use as hybrid Cherenkov/scintillation target in low-energy and accelerator neutrino experiments to large-volume neutron vetoes for dark matter detectors. Here, we present a novel WbLS featuring new components (the surfactant Triton-X and vitamin C for long-term stability), a new production recipe, and a thorough characterization of its properties. Moreover, based on neutron scattering data we are able to demonstrate that the pulse shape discrimination capabilities of this particular LS are comparable to fully-organic LAB based scintillators.

hep-ex↗

arXiv2024

Development of a Bi-solvent Liquid Scintillator with Slow Light Emission

One of the most promising approaches for the next generation of neutrino experiments is the realization of large hybrid Cherenkov/scintillation detectors made possible by recent innovations in photodetection technology and liquid scintillator chemistry. The development of a potentially suitable future detector liquid with particularly slow light emission is discussed in the present publication. This cocktail is compared with respect to its fundamental characteristics (scintillation efficiency, transparency, and time profile of light emission) with liquid scintillators currently used in large-scale neutrino detectors. In addition, the optimization of the admixture of wavelength shifters for a scintillator with particularly high light emission is presented. Furthermore, the pulse-shape discrimination capabilities of the novel medium was studied using a pulsed particle accelerator driven neutron source. Beyond that, purification methods based on column chromatography and fractional vacuum distillation for the co-solvent DIN (Diisopropylnaphthalene) are discussed.

physics.ins-det↗

arXiv2023

Fast neutron production at the LNL Tandem from the $^7$Li($^{14}$N,xn)X reaction

Fast neutron beams are of relevance for many scientific and industrial applications. This paper explores fast neutron production using a TANDEM accelerator at the Legnaro National Laboratories, via an energetic ion beam (90 MeV $^{14}N$) onto a lithium target. The high energy models for nuclear collision of FLUKA foresee large neutron yields for reactions of this kind. The experiment aimed at validating the expected neutron yields from FLUKA simulations, using two separate and independent set-ups: one based on the multi-foil activation technique, and the other on the time of flight technique, by using liquid scintillator detectors. The results of the experiment show clear agreement of the measured spectra with the FLUKA simulations, both in the shape and the magnitude of the neutron flux at the measured positions. The neutron spectrum is centered around the 8 MeV range with mild tails, and a maximum neutron energy spanning up to 50 MeV. These advantageous results provide a starting point in the development of fast neutron beams based on high energy ion beams from medium-sized accelerator facilities.

nucl-ex↗

arXiv2022

TAO -- The Taishan Antineutrino Observatory

The Taishan Antineutrino Observatory (TAO or JUNO-TAO) is a satellite detector for the Jiangmen Underground Neutrino Observatory (JUNO). JUNO aims at simultaneously probing the two main frequencies of three-flavor neutrino oscillations, as well as their interference related to the mass ordering, at a distance of some 53 km from two powerful nuclear reactor complexes in China. Located near the Taishan-1 reactor, TAO independently measures the antineutrino energy spectrum of the reactor with unprecedented energy resolution. The TAO experiment will realize a neutrino detection rate of about 2000 per day. In order to achieve its goals, TAO is relying on cutting-edge technology, both in photosensor and liquid scintillator (LS) development which is expected to have an impact on future neutrino and Dark Matter detectors. In this paper, the design of the TAO detector with a special focus on calorimetry is discussed. In addition, an overview of the progress currently being made in the R&D for photosensor and LS technology in the frame of the TAO project will be presented.

physics.ins-det↗

arXiv2022

Design, Status and Physics Potential of JUNO

The Jiangmen Underground Neutrino Observatory (JUNO) is a 20 kton multi-purpose liquid scintillator detector currently being built in a dedicated underground laboratory in Jiangmen (PR China). Data-taking is expected to start in 2023. JUNO's main physics goal is the determination of the neutrino mass ordering using electron anti-neutrinos from two nuclear power plants at a baseline of about 53 km. JUNO aims for an unprecedented energy resolution of 3 $\%$ at 1 MeV for the central detector, which will allow determining the mass ordering with 3 $σ$ significance within six years of operation. Furthermore, measurements in neutrino physics and astrophysics, such as estimating the solar oscillation parameters and the atmospheric mass splitting with an accuracy of 0.5 $\%$ or better, will be performed. In these proceedings, JUNO's design, the status of its construction, and its physics potential, will be presented alongside a short excursion into its rich R$\&$D program.

physics.ins-det↗

arXiv2018

Measurements of the Lifetime of Orthopositronium in the LAB-Based Liquid Scintillator of JUNO

Electron antineutrinos are detected in organic liquid scintillator based neutrino experiments by means of the inverse beta decay, producing both a positron and a neutron. The positron may form a bound state together with an electron, called positronium (Ps). The longer-lived spin state of Ps, orthopositronium (o-Ps) has a lifetime of about $3\,\mathrm{ns}$ in organic liquid scintillators (LS). Its formation changes the time distribution of photon emission, which affects positron reconstruction algorithms and allows the application of pulse shape discrimination (PSD) to distinguish electron from positron events. In this work, we measured the lifetime $τ_2$ of o-Ps in the linear alkylbenzene (LAB) based LS of the JUNO (Jiangmen Underground Neutrino Observatory) experiment including wavelength shifters, obtaining $τ_2 = 2.97\,\mathrm{ns} \pm 0.04\,\mathrm{ns}$. Due to systematics, which are not yet completely understood, we are not able to give a final result for the o-Ps formation probability $I_2$. We use a novel type of setup, which allows a better background suppression as compared to commonly used PALS (positron annihilation lifetime spectroscopy) measurements.

physics.ins-det↗