Abstract
In this work, we report on the first demonstration of Lab on Fiber (LOF) dosimeter for ionizing radiation monitoring at ultra-high doses. The new dosimeter consists in a metallo-dielectric resonator at sub-wavelength scale supporting localized surface plasmon resonances realized on the optical fiber (OF) tip. The resonating structure involves two gold gratings separated by a templated dielectric layer of poly(methyl methacrylate) (PMMA). Two LOF prototypes have been manufactured and exposed at the IRRAD Proton Facility at CERN in Geneva to 23 GeV protons for a total fluence of 0.67 × 1016 protons/cm2, corresponding to an absorbed dose of 1.8 MGy. Experimental data demonstrated the “radiation resistance” feature of the LOF devices and a clear dependence of the reflected spectrum versus the total dose, expressed by a cumulative blue-shift of ~1.4 nm of the resonance combined with a slight increase of 0.16 dBm in the reflected spectrum. The numerical analysis carried out to correlate the experimental results with the dimensional and physical properties of the resonator, expected to be tightly connected to the absorbed dose, suggests that the main phenomenon induced by exposure to proton beam and able to explain the measured spectral behavior is the reduction of the PMMA thickness, which is also consistent with past literature in the field. Preliminary results demonstrated the potentiality of the proposed platform as dosimeter at MGy dose levels for high energy physics experiments.
Highlights
The High Energy Physics (HEP) community is currently discussing the possible upgrades of today’s Large Hadron Collider (LHC), in order to schedule a roadmap for the construction of the generation HEP experiment
In order to meet the abovementioned needs and to overcome the limitations suffered by the majority of OF-based approaches, especially in terms of operational range and saturation levels, as well as influence of temperature and issues related to intensity-based measurements, in this work, we propose a new extrinsic OF dosimeter for ultra-high dose radiation, based on the so-called LOF technology[10,11,12]
The HEP community is currently preparing for the incoming upgrade of the present Large Hadron Collider, into the higher performance High Luminosity LHC, and it envisages the possible future upgrades such as the HE-LHC and the new machines like the CLIC and the Future Circular Collider (FCC)
Summary
Number of particles crossing the material and is expressed in particles/cm2 [Ф]. For semiconductor material, the normalized 1 MeV neutron equivalent fluence [n1MeV/cm2] is instead commonly used. In order to meet the abovementioned needs and to overcome the limitations suffered by the majority of OF-based approaches, especially in terms of operational range and saturation levels, as well as influence of temperature and issues related to intensity-based measurements, in this work, we propose a new extrinsic OF dosimeter for ultra-high dose radiation, based on the so-called LOF technology[10,11,12]. The spectral response arising from these resonant phenomena is sensitive to variations of both optical properties and size of the platform components These include real and imaginary parts of the RI of adopted materials, as well as lattice period, holes radius, metal and dielectric thickness.
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