We evaluate the temperature effect on the X-ray radiation-induced luminescence (RIL) of differently doped silica fibers obtained via the sol-gel route. Previous investigations showed that these optical materials exhibit interesting dosimetry properties, such as very good detection capabilities and linear response over a large range of dose rate. However, several radiation environments, such as space and particle accelerators, also require a careful assessment of the temperature effect on these properties exploited for dosimetry. With this aim, we characterize their RIL efficiency and spectral dependence at several irradiation temperatures. We demonstrate that all the investigated materials present a nonnegligible temperature dependence of the RIL in the range from -120 degrees C to 80 degrees C. The temperature effect on the RIL signal is still compensable via calibration and temperature monitoring.

The distributed optical fiber radiation sensor (DOFRS) developed by CERN is a key technology for the spatially continuous and real-time monitoring of radiation dose in harsh environments. Silica-based optical fibers (OFs) doped or co-doped with phosphorous are used as sensing elements of the DOFRS systems. The performance of these systems is strongly dependent on the radiation sensitivity of the OFs used, as well as the possibility to qualify and calibrate them for dosimetry applications. In this article, we report on the radiation response of a set of 12 Ge/P-doped single-mode (SM) OFs at 1550 and 1625 nm under Co-60 gamma -rays, including a post-irradiation study to evaluate the recovery of the fibers under test. After conducting several experiments to evaluate the performance of the OFs, we determined which ones are the most suitable to be used in the radiation sensing fiber optics cables installed in CERN's accelerator complex.

In this work we present the radiation environment of the Large Hadron Collider (LHC), focusing on the year 2022, the first after the Long Shutdown 2 (2019-2021).We highlight the most prominent radiation level changes with respect to the 2018 operation, commenting on the related Radiation Hardness Assurance implications.In addition to presented data from wellestablished radiation monitors, such as Beam Loss Monitors and RadMons, we demonstrated the excellent capabilities of the recently deployed Distributed Optical Fibre Radiation Sensing covering selected regions of the LHC.Profiting from the SRAMs deployed along the accelerator and its shielded alcoves, we demonstrated their capabilities for distributed SEUs monitoring.

LUMINA, a fiber-based dosimeter, exploiting the radiation induced attenuation (RIA) phenomenon, has been operational inside the International Space Station (ISS) since August 2021. We discuss in this article its capability to detect the possible signatures of recent solar particle events (SPEs) through the related increase of the dose rate (DR) radiation level within the ISS. Our analysis over 699 days of operation shows that the two LUMINA channels, operating either in the visible or infrared (IR) domains, are able to detect the slight DR increase related to the solar flares (SFs), in particular, in the poles regions. The South Atlantic Anomaly (SAA) remains well detected by both LUMINA channels, but no significant increase of the DRs is noticable during the solar events in this region. These results were obtained at DRs close to the lower detection limit of our instrumentation, demonstrating the potential of fiber dosimeters, especially if less shielded, to detect the SFs and monitor the radiation environment.

The super proton synchrotron (SPS) is the second largest accelerator at CERN where protons are accelerated between 16 and 450 GeV/c. Beam losses, leading to the mixed-field radiation of up to MGy magnitude, pose a threat to the reliability of the electronic equipment and polymer materials located in the tunnel and its vicinity. In particular, in the arc sectors, where both main magnets and radiation sensors are periodically arranged, the total ionizing dose (TID) is of concern for the front-end electronics of a logarithmic position system (ALPS). The SPS is equipped with multiple radiation detection systems, such as beam loss monitors (BLMs), RadMons, and as of 2021, the distributed optical fiber radiation sensor (DOFRS) that combined all together provides a very comprehensive picture of both the TID spatial distribution and its time evolution. Within this study, the overview of measured 2021 and 2022 TID levels is presented, together with the demonstration of capabilities offered by the different radiation monitors. The DOFRS, supported by the passive radiophotoluminescence (RPL) dosimeter measurements, is used to assess the TID values directly at the electronic racks, which turned out to be reaching several tens of Gy/year, potentially affecting the ALPS lifetime.

The first nested anti-resonant hollow-core fiber radiation study is reported. A record near-zero radiation induced attenuation is observed under γ-rays and X-rays. These results open new possibilities for fiber-based applications in radiation environments.

The combined effect of radiation and cryogenic temperatures on the response of two different multimode fibers (MMF), one conventional and one radiation resistant, has been investigated. This article presents the outcome of the measurements of the radiation induced attenuation (RIA) in those fibers at 830 nm and 1310 nm under gamma irradiation and at temperatures of 300 K, 218 K, 143 K and 10. The results reveal a strong increase of the RIA when decreasing the temperature down to cryogenic levels, with substantial different growth dynamics between the two fibers. However, both cases show a non-linear dependence of the RIA on the temperature. It is also observed that after a long recovery time, including the heating of the fiber from cryogenic temperature to room temperature, a large amount of the defects created are annealed, bringing the radiation resistant fiber close to its initial performance.

We present the experimental characterization of both radiation induced attenuation (RIA) and radioluminescence (RL) of differently doped optical fiber (OF) radiation sensors. We present data for different sample lengths and total ionizing dose (TID) up to 600 kGy (SiO2) under X-rays. Combined RIA and RL responses are used to attempt explaining the variation of the RL signal with TID on those fibers.

The optical-fiber-based dosimeter of the LUMINA project was deployed in August 2021 in the International Space Station in the framework of the Alpha mission. The sensing elements of the dosimeter are P-doped optical fibers, which were proven to be excellent candidates for dosimetry applications. The twofold objective of this paper is to provide a theoretical model for the radiation response of the dosimeter and to report on the experimental work carried out at CERN for the qualification and calibration of the engineering model of the LUMINA dosimeter. Combining the theoretical response and experimental data, the calibration curve of the flight model is obtained. Finally, this study broadens the investigation of the room temperature radiation response of P-doped optical fibers in a range of dose rates 104 times lower than previously reported, from 21µGy(SiO2)/h to145mGy(SiO2)/h.

This Letter reports the first, to the best of our knowledge, spectral radiation induced attenuation (RIA) measurements of nested anti-resonant nodeless hollow-core fibers (NANFs). A 5-tube NANF, alongside a solid-core single-mode radiation resistant fiber (SM-RRF), was irradiated under γ-ray up to 101 kGy (SiO2) and under x-ray up to 241 kGy (SiO2). No RIA was observed in the NANF in the second half of the O-band, the S-band, the C-band, and the L-band. The NANF showed a reduction of absorption bands associated with water and HCl under irradiation. Three new attenuation peaks were radiolytically induced and are attributed to the creation of HNO3. These peaks are centered respectively at 1441 nm, 1532 nm, and 1628 nm, with a full width at half maximum (FWHM) of, respectively, 10 nm, 12 nm, and 12 nm. These results demonstrate that the wide bandwidth range of NANFs is essentially unaffected by radiation, but the internal gas contents of the NANF must be managed to avoid producing undesirable spectral features through radiolytic reactions. Wide spectral regions almost unaffected by the ionizing radiation could open new possibilities for the use of NANF in harsh radiation environments.

A benchmark between various radiation monitors employed at CERN for radiation to electronics applications and their simulated values with the FLUKA Monte Carlo is performed at the CHARM mixed-field irradiation facility. Comparisons are made for different operational conditions, using data recorded in the 2015–2018 period.

In this work we present a combined experimental and ab initio simulation investigation concerning the Germanium Lone Pair Center (GLPC), its interaction with molecular oxygen (O2), and evolution under irradiation. First, O2 loading has been applied here to Ge-doped optical fibers to reduce the concentration of GLPC point defects. Next, by means of cathodoluminescence in situ experiments, we found evidence that the 10 keV electron irradiation of the treated optical fibers induces the generation of GLPC centers, while in nonloaded optical fibers, the irradiation causes the bleaching of the pre-existing GLPC. Ab initio calculations were performed to investigate the reaction of the GLPC with molecular oxygen. Such investigations suggested the stability of the dioxagermirane (DIOG) bulk defect, and its back conversion into GLPC with a local release of O2 under irradiation. Furthermore, it is also inferred that a remarkable portion of the O2 passivated GLPC may form Ge tetrahedra connected to peroxy bridges. Such structures may have a larger resistance to the irradiation and not be back converted into GLPC.

This paper focuses on the theoretical model, qualification and calibration of an optical fibre dosimeter developed to measure extremely low radiation doses and deployed in the International Space Station in August 2021.

With the foreseen upgrades in HL-LHC, the Versatile Link Plus project was launched to develop the optical fibre links between the experiments and the counting room, in order to reach higher data rates. New fibre cabling plants have been designed in this framework for tight integration in experiment front ends and operation at higher radiation doses. Those cabling plants make use of novel multi-fibre assemblies that are tailored to the specific experiment requirements and conditions. This paper describes the design decisions that have led to the final production-ready prototypes and the related implementation of a large-scale procurement framework.

We evaluate the temperature effect on the X-ray radiation-induced luminescence (RIL) of Cu- or Ce-single-doped and CuCe-codoped silica glass. Previous investigations showed that these optical materials exhibit interesting dosimetry properties, such as very good detection capabilities and linear response over a large range of dose rate. However, several radiation environments, such as space and particle accelerators, also require a careful assessment of the temperature effect. With this aim, we characterize their RIL efficiency and spectral dependence at several irradiation temperatures. We demonstrate that all the investigated materials present a nonnegligible temperature dependence of the RIL in the range -120 °C to 80 °C, whilst preserving linear dose rate dependence at each irradiation temperature. However, the temperature effect on the RIL signal is still compensable via calibration and temperature monitoring.

The X‐ray radiation‐induced attenuation (RIA) growth kinetics are studied online in different single‐mode aluminosilicate optical fibers in the near‐IR (NIR) domain to evaluate their potential in terms of dosimetry. The optical fibers differ by Al contents, core sizes, drawing parameters, and also by a preform deposition process. The data show no dependence of the RIA on all these parameters, a positive result for the design of point or distributed radiation detectors exploiting RIA to monitor the dose. The RIA growth rate is unchanged for dose rates changing from 0.073 to 6.25 Gy(SiO2) s−1, and the RIA linearly increases with the dose up to 2 kGy(SiO2). Small but noticeable RIA changes are observed when the irradiation temperature increases up to 50 °C during successive irradiation runs. Such results, and the post‐irradiation RIA recovery, have to be considered for the application, as they can affect the dose measurement accuracy. Finally, the spectral analysis shows no dependence of the spectral shape on the fiber and irradiation parameters. As a consequence, the data reported at 1310 and 1550 nm give information not only for the RIA kinetics at telecommunications and sensor wavelengths but also for the whole NIR range often used fiber‐based technologies.

Point or distributed optical fiber (OF)-based dosimeters can exploit the observed linear dependence of the radiation-induced attenuation (RIA) at 1550 nm in phosphosilicate OFs to monitor the total ionizing dose (TID). The temperature dependence of the radiation sensitivity coefficients at 1550 nm (expressed in dB km -1 Gy -1 ) of three phosphorus-doped single-mode OFs has been investigated between -80 °C and 300 °C for TID ranging from 1 Gy to 1 kGy(SiO 2 ). Our measurements reveal the same temperature dependence of the calibration factor for the three fibers at the higher temperatures (>120 °C) where the P1 defects, at the origin of the IR-RIA, are metastable. However, the uncertainties on the TID measurements through the fiber-based dosimeter remain within the 15% for temperatures ranging from -80 °C to 120 °C for the three tested fibers. The independence of the RIA and then of the dose measurements from the dose rate is also maintained in this temperature range.

We describe the implementation of a versatile system and the corresponding method to perform fast postmortem optical attenuation measurements on irradiated optical-fibers (OFs) for dosimetry purposes. The measurement is based on the radiation-induced attenuation (RIA) phenomenon. We use a dual-wavelength optical time-domain reflectometer (OTDR) coupled with a suitable radiation-sensitive OF. We demonstrate that radiation dose levels higher than 100 Gy(SiO2) can be measured efficiently with 1-m-long samples. The accuracy of the measurement increases with the increasing radiation dose if the length of the sample is kept fixed. We also highlight the possible limitations of our approach and, more generally, limitations related to performing accurate RIA measurement (online or postmortem) on short single-mode (SM) OF samples. The technological solution we propose can be tailored to address different radiation environments.

We investigate the X-ray (40 keV) and gamma-ray (1.2 MeV) radiation responses of three different radiation sensitive Optical Fibers (OFs) up to 100 Gy(SiO2). In particular, we study the Radiation Induced Attenuation (RIA) in the Near Infrared domain (NIR) for single mode OFs doped with Phosphorus (P), Aluminum (Al) and Phosphorus/Cerium (PCe) in their cores at three temperatures up to 50 degrees C. RIA levels and kinetics strongly depend on the operating wavelength and fiber composition. For both P and PCe-doped fibers, the P1 defects are the main contributors to the RIA, with Ce-codoping inducing a decrease of radiation sensitivity. For the Al-doped fiber, no specific absorption bands can be discriminated in the NIR. Both X- and gamma-rays lead to the same RIA levels and kinetics. The RIA spectral dependences on dose and temperature highlight the potential of the three investigated fibers for radiation detection and dosimetry. To better discuss the properties of point defects responsible for the NIR RIA, we analyze how the fundamental mode propagation influences the RIA spectra of each fiber type. By reasonably assuming that the core RIA exceeds largely the cladding RIA and by calculating the mode Confinement Factor (CF), the RIA spectra of the core material are reconstructed and the spectral characteristics of defects are discussed for each type of fibers.

We demonstrate the feasibility of resetting and reusing dosimeters exploiting the measurement of the infrared radiation-induced attenuation (IR-RIA) in phosphosilicate optical fibers (OFs) to provide point or distributed dose measurements in radiation environments. To bleach the room temperature stable IR-RIA, we used the photobleaching (PB) phenomenon. The PB efficiency was evaluated for different wavelengths in the [400-1100] nm range. The best identified PB resetting condition consists in using a continuous-wave Argon-ion laser at 514 nm. This treatment successfully bleached ∼97% of the IR-RIA at 1550 nm of a 30 m-long P-doped single mode optical fiber X-ray irradiated at a dose of 100 Gy. Successive re-irradiations of the same OF sample, regenerated after each run, confirm that the dosimeter keeps the same calibration curve during the whole process.