Session K09: Particle Physics Instrumentation IV

Characterization of novel scintillators for neutrino physics

In recent years, novel liquid scintillators have been developed allowing the separation of Cherenkov and scintillation light. They hold the potential for a major breakthrough in neutrino detection technology, allowing development of large, low-threshold, directional detectors suited for the study of neutrino properties and astrophysical observations.

We perform two characterization experiments for these novel liquid scintillation media exploiting the CN proton beam at LNL, Italy. We investigate the energy-dependent quenching effect and the fluorescence time spectra utilizing gammas and neutrons produced in collisions of the proton beam with a lithium target at a few MeV beam energy. In addition, we also perform high precision measurements of these properties for classical organic scintillators. Our results will allow a refined understanding and modelling of scintillator properties and constitute valuable input for the design of future large scale detectors.   

The development of slow Water-based Liquid Scintillators for next-generation neutrino experiments

The development and production of Water-based Liquid Scintillators (WbLS) offers the potential to revolutionize next-generation neutrino experiments. This novel detection media, containing both water and organic constituents, produces a combination of scintillation and Cherenkov light, with the utilisation of both components expanding the physics potential of large-scale experiments. It will further enhance mass hierarchy and CP violation determination capabilities, whilst assisting searches for the diffuse supernova neutrino background, nucleon decay and neutrinoless double beta decay. A challenge of using this neoteric media is the separation of the two light components. To facilitate this, an exciting evolution would be to produce Water-based Slow Scintillators (WbSS) that fluoresce on longer timescales. The difficulties of this are wide and varied: Which amalgamation is optimal? What are the ideal characteristics for neutrino experiments? How can we fully parameterise and understand the new media? In this talk, the synthesis, modelling, measurement and current status of these innovative cocktails will be presented.   

High precision scintillator time profile measurements using an LAPPD

Liquid scintillators have seen consistent use in nuclear and particle physics over several decades, with new mixtures still being developed today. In the context of large-scale neutrino detectors, accurate knowledge of the emission time profile of the scintillator cocktail is necessary for robust vertex reconstruction, and the potential for direction reconstruction via timing-based selection of Cherenkov photons is directly correlated with the scintillator rise-time. We present a single-photon method for measuring the time profiles of organic liquid scintillators which is robust to the light yield of the sample, where an LAPPD provides enhanced sensitivity to the rise-time, and report implications for timing-based particle-identification in water-based liquid scintillator based on measurements made using the CHESS apparatus at LBNL.   

Towards directional detection of reactor antineutrinos with segmented 6Li-doped PSD plastic scintillator — SANDD status update

The development of ⁶Li-doped PSD plastic scintillators at LLNL opened new opportunities for reactor-antineutrino detectors. Unlike liquid scintillators, plastics are easily machinable into segments and do not require special handling or regulatory approvals from reactor operators. Lithium-6 is advantageous over other neutron capture agents as it has a relatively high cross section and a well-localized capture ⁶Li(n, α). The reactor-antineutrino directional detection relies on reconstructing the interaction vertices for prompt positron and delayed neutron-capture events. To operate at the surface level with minimal or no overburden, the detector should have an excellent cosmogenic-fast-neutron background-rejection mechanism. Pulse-Shape Discrimination is a powerful technique to reject backgrounds.

This talk is a status update on the Segmented AntiNeutrino Directional Detector (SANDD) project, as we near a completion of the full detector — a set of plastic segments with a hybrid SiPM/PMT readout.   

Advances in Large Area Picosecond Photo-Detectors – LAPPD™

The Large Area Picosecond Photo-Detector (LAPPD), commercialized by Incom Inc., is the world's largest planar-geometry microchannel plate (MCP) based photodetector.

It incorporates a chevron pair of 10 μm or 20μm MCPs, produced by applying resistive and emissive Atomic Layer Deposition (ALD) layers to glass capillary array (GCA) substrates, encased in a hermetic glass or ceramic package. The borosilicate glass or UV grade fused silica entry window is coated with a high sensitivity bi-alkali photocathode. The internal stack has been redesigned to increase the detection area from 350 cm² to 370 cm².

The GEN I LAPPD utilizes direct strip anode readout while the GEN II LAPPD features a customizable capacitively-coupled pixelated readout with resistive anode, significantly reducing cross-talk. LAPPDs have demonstrated electron gains of 10⁷, low dark noise rates (< kHz/cm²), single photoelectron (PE) timing resolution of 52 ps RMS (electronics-limited) and mm-scale spatial resolution, high (>25%) QE uniform bi-alkali photocathodes, and good magnetic field tolerance.

LAPPDs are good candidates for neutrino, HEP, and neutrinoless double-beta decay experiments, and medical and nuclear non-proliferation applications. We report on recent developments and performance of the LAPPDs.   

Optimization of Light Yield and Timing of Extruded Plastic Scintillator

High energy physics experiments often use extruded plastic scintillator with wavelength-shifting (WLS) fiber coupled to silicon photomultiplier (SIPM) readout. Using cosmic ray, we studied factors, such as the fiber's diameter, the extrusion dimension, and the type of fiber, that can affect the light yield and timing resolution of plastic extruded scintillator read out with WLSs and SiPMs. We also studied the decay time of the different types of fiber using a 405nm laser diode to excite the fiber directly as well as a 260nm LED to excite the extruded scintillator, where the scintillation is then carried by the fiber to the SiPM. Our results suggest that increasing the thickness of the extrusion and increasing the fiber diameter increases the light yield. Furthermore, BCF-92 fiber produces a lower light yield than Y-11 but has a significantly faster decay time and better timing resolution.   

Development and Demonstration of Metalenses for Improved Light Collection in Noble Element Experiments

As many noble element experiments are moving to larger and larger scales to fulfill their physics goals, providing solutions to enhance the physics potential of these large-scale experiments while maintaining a reasonable cost is of the utmost importance to our field. Metalenses, dielectric nanostructures that focus light like a lens while being small, durable, radiopure, and low cost, could transform light collection. Our research group has previously demonstrated that metalenses can be an attractive solution to increase light collection. We are now developing metalenses optimized for noble element experiments and targeting several potential applications. In this talk, the most recent results of these optimized metalenses will be presented.   

Dependence of TPB-coated and uncoated polytetrafluoroethylene reflectance on thickness at visible and ultraviolet wavelengths in air

Polytetrafluoroethylene (PTFE) is an excellent diffuse reflector widely used in light collection systems for particle physics experiments. The NEXT experiment uses PTFE inside the detector to provide highly reflective surfaces to increase the light collection. This light collection is further improved using wavelength shifters, specifically TPB. We describe investigations into the reflectance of PTFE based on thickness, in both TPB-coated and uncoated PTFE. These investigations occurred for light of wavelengths 128 nm, 260nm and 450nm using two complementary methods. The 450 and 260 nm light are generated using LEDs, while 128 nm light is generated by argon scintillation in the presence of an alpha source. Finally, we investigate the variations in reflectivity between different PTFE suppliers.   

The Dichroicon: A Spectral Photon Sorter

Many large scale particle detectors use photons as their primary event detection method, usually detecting numbers of photons and their arrival times. Photons also carry information about an event through their wavelength, polarization, and direction, but often little to none of this information is utilized. This talk aims to characterize the "dichroicon," a Winston-style light cone comprised of dichroic filters which allows detectors to use the wavelength information encoded in photons. The dichroicon has a broad range of applications including the discrimination between Cherenkov and scintillation light in scintillator detectors, the correction for photon dispersion in large scale detectors, and new handles on particle ID. This talk will present experimental results taken with CHESS, a benchtop scale particle detector located at Berkeley Lab. These results quantify the dichroicon's ability to separate scintillation light from Cherenkov light and explore how this affects event reconstruction. Additionally, simulation results illustrating the impact of dichroicons in next generation neutrino detectors will be discussed.