Luminescent materials and optoelectronics, particularly those that rely on down-conversion optical phenomena (i.e., involving a conversion from higher-energy photons into lower-energy photons), have garnered increasing interest for various photonics applications. Over the years, a plethora of down-converting luminescent materials has been actively explored, in particular for enhancing the collection and conversion efficiency of luminescent solar concentrators since the 80s. However, with the exploration of new down-converting luminescent materials, as well as the recent development of numerous emerging applications utilizing luminescent components for enhanced system performance, the technology is envisaged to expand beyond its use in luminescent solar concentrators. This perspective article aims at shedding light on the significance of incorporating luminescent materials and components for various emerging technologies related to optical-based communication, imaging, tracking, sensing, and data storage and encryption. The related opportunities and challenges are also outlined, which can potentially inspire practical pathways towards commercialization of luminescent-based optoelectronics and shape the way forward for the broader community.

https://aip.scitation.org/doi/pdf/10.1063/5.0127552

Down-converting luminescent optoelectronics and their applications

BACKGROUND
Recent proposals of high dose rate plans in protontherapy as well as very short proton bunches may pose problems to current beam monitor systems. There is an increasing demand for real-time proton beam monitoring with high temporal resolution, extended dynamic range and radiation hardness. Plastic scintillators coupled to optical fibre sensors have great potential in this context to become a practical solution towards clinical implementation.


PURPOSE
In this work, we evaluate the capabilities of a very compact fast plastic scintillator with an optical fiber readout by a SiPM and electronics sensor which has been used to provide information on the time structure at the nanosecond level of a clinical proton beam.


MATERIALS AND METHODS
A 3×3×3 mm3 plastic scintillator (EJ-232Q Eljen Technology) coupled to a 3×3 mm2 SiPM (MicroFJ-SMA-30035, Onsemi) has been characterized with a 70 MeV clinical proton beam accelerated in a Proteus One synchrocyclotron. The signal was read out by a high sampling rate oscilloscope (5 GS/s). By exposing the sensor directly to the proton beam, the time beam profile of individual spots was recorded.


RESULTS
Measurements of detector signal have been obtained with a time sampling period of 0.8 ns. Proton bunch period (16 ns), spot (10 μs) and interspot (1 ms) time structures could be observed in the time profile of the detector signal amplitude. From this, the RF frequency of the accelerator has been extracted, which is found to be 64 MHz.


CONCLUSIONS
The proposed system was able to measure the fine time structure of a clinical proton accelerator online and with ns time resolution. This article is protected by copyright. All rights reserved.

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/mp.16333

Technical note: Measurement of the bunch structure of a clinical proton beam using a SiPM coupled to a plastic scintillator with an optical fiber.

In recent years, proton therapy has gained importance as a cancer treatment modality due to its conformality with the tumor and the sparing of healthy tissue. However, in the interaction of the protons with the beam line elements and patient tissues, potentially harmful secondary neutrons are always generated. To ensure that this neutron dose is as low as possible, treatment plans could be created to also account for and minimize the neutron dose. To monitor such a treatment plan, a compact, easy to use, and inexpensive dosimeter must be developed that not only measures the physical dose, but which can also distinguish between proton and neutron contributions. To that end, plastic optical fibers with scintillation materials (Gd2O2S:Tb, Gd2O2S:Eu, and YVO4:Eu) were irradiated with protons and neutrons. It was confirmed that sensors with different scintillation materials have different sensitivities to protons and neutrons. A combination of these three scintillators can be used to build a detector array to create a biological dosimeter.

/pdf/optical-fibers-as-dosimeter-detectors-for-mixed-proton-35b9mt3h.pdf

Optical Fibers as Dosimeter Detectors for Mixed Proton/Neutron Fields—A Biological Dosimeter

In proton therapy, the dose from secondary neutrons to the patient can contribute to side effects and the creation of secondary cancer. A simple and fast detection system to distinguish between dose from protons and neutrons both in pretreatment verification as well as potentially in vivo monitoring is needed to minimize dose from secondary neutrons. Two 3 mm long, 1 mm diameter organic scintillators were tested for candidacy to be used in a proton–neutron discrimination detector. The SCSF-3HF (1500) scintillating fibre (Kuraray) and EJ-260 plastic scintillator (Eljen Technology) were irradiated at the TRIUMF Neutron Facility and the Proton Therapy Research Centre. In the proton beam, we compared the raw Bragg peak and spread-out Bragg peak response to the industry standard Markus chamber detector. Both scintillator sensors exhibited quenching at high LET in the Bragg peak, presenting a peak-to-entrance ratio of 2.59 for the EJ-260 and 2.63 for the SCSF-3HF fibre, compared to 3.70 for the Markus chamber. The SCSF-3HF sensor demonstrated 1.3 times the sensitivity to protons and 3 times the sensitivity to neutrons as compared to the EJ-260 sensor. Combined with our equations relating neutron and proton contributions to dose during proton irradiations, and the application of Birks’ quenching correction, these fibres provide valid candidates for inexpensive and replicable proton-neutron discrimination detectors.

/pdf/organic-scintillator-fibre-sensors-for-proton-therapy-s2cd6286.pdf

Organic Scintillator-Fibre Sensors for Proton Therapy Dosimetry: SCSF-3HF and EJ-260

Effective online monitoring of the spatial distribution of high‐energy radiation is of significant importance in various fields such as medical imaging, high‐energy physics, and homeland security. However, achieving radiation detectors with both high sensitivity and minimal disturbance is an enormous challenge. The present study introduces a solution to this bottleneck issue through the development of a full‐inorganic scintillating fiber, successfully demonstrating its application in constructing a radiation monitoring device. The scintillating fiber, activated with Ce3+ and fabricated using the melt‐in‐tube approach, is lightweight with a density of 2.5 g cm−3 and exhibits efficient scintillating emission with a light yield of 4000 photons MeV−1. These characteristics enable the achievement of radiation detection with high sensitivity while keeping disturbance to the incident radiation beam at a minimum. Furthermore, 2D and 3D radiation beam monitors are constructed based on these scintillating fibers, facilitating spatial radiation monitoring. The findings demonstrate that full‐inorganic scintillating fibers and devices offer a synergistic combination of high sensitivity and negligible disturbances. This progress not only introduces a novel full‐inorganic fiber for radiation detection but also suggests promising applications in various nuclear fields where 3D radiation beam tracking is essential.

Online Radiation Beam Tracking by Using Full‐Inorganic Scintillating Fibers

The time structure of proton beam pulses has been measured using a three-dimensional beam profile monitor (BPM) with scintillating fibers at the Korea Multi-purpose Accelerator Complex (KOMAC). The BPM measured the spatial and temporal distributions of 100-μs-long macropulses at the 20-MeV and 100-MeV proton beamlines. The scintillating fiber BPM covers an effective area of 120(x)×120(y) mm2, with 12 fibers separated by 10 mm in each direction. Signals from 1-mm-diameter fibers were read out with a 1.3×1.3mm2 multi-pixel photon counter (MPPC) and fed into a 500-MHz flash ADC. We successfully measured the beam profile and its time structure at the same time. Using multi-layered collimators, the beam intensity could be sufficiently reduced so that the BPM could measure individual beam particles. 

Three-dimensional measurement of a proton beam profile at KOMAC with a scintillating fiber detector

A multiplicity trigger detector (MTD) was developed for the SπRIT experiment that aims to probe the high-density symmetry energy via heavy-ion collisions (HICs). The MTD is designed to measure the charged-particle multiplicity in HICs to provide a trigger signal that can be used to select high-multiplicity events induced by central collisions. The MTD consists of two side-walls segmented into 30 plastic scintillation paddles, each equipped with a multi-pixel photon counter. A custom board with EASIROC front-end ASIC is used as readout electronics. A multiplicity logic signal is generated by an on-board FPGA that processes the discriminated signals from EASIROCs. The overall latency of the whole detector system for outputting the trigger is less than 100 ns, including 52 ns of electronics latency for processing the signals. During the measurement of 112Sn+124Sn reactions at an incident energy of 270 MeV/nucleon, the minimum multiplicity threshold of the MTD was set to 4, where the overall trigger efficiency was obtained to be about 39 % for inclusive nuclear reactions. A simulation study with a numerical calculation of HICs found that the central collisions of impact parameters of less than 4 fm can be triggered with a high efficiency of more than 95 % by the experimental trigger condition. 

Multiplicity trigger detector for the S<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="d1e1021" altimg="si25.svg"><mml:mi>π</mml:mi></mml:math>RIT experiment

A new radioactive ion-beam accelerator facility, RAON, is under construction in Korea. Among the seven experimental systems being built, the Large Acceptance Multi-Purpose Spectrometer (LAMPS) in the high-energy experimental hall is the versatile detector system for nuclear physics. Its primary goal is to study the nuclear equation of state (EoS) and the symmetry energy of the compressed nuclear matter, which should be essential to understand the effective nuclear interactions and structure of the astrophysical objects like neutron stars. The basic LAMPS system consists of the beam diagnostic elements such as the starting counters and beam drift chambers, the time-projection chamber, the barrel and forward time-of-flight systems, the forward neutron detector array, and the superconducting solenoid magnet. In this paper the overview of the present status of each detector component for LAMPS will be given with some prospects. 

Status of LAMPS at RAON

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Three-dimensional measurement of a proton beam profile at KOMAC with a scintillating fiber detector

Multiplicity trigger detector for the S<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="d1e1021" altimg="si25.svg"><mml:mi>π</mml:mi></mml:math>RIT experiment

Status of LAMPS at RAON