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Optical fibers hold promise for accurate dosimetry in small field proton therapy due to their superior spatial resolution and the lack of significant Cerenkov contamination in proton beams. One known drawback for most scintillation detectors is signal quenching in areas of high linear energy transfer, as is the case in the Bragg peak region of a proton beam. In this study, we investigated the potential of innovative optical fiber bulk materials using the sol-gel technique for dosimetry in proton therapy. This type of glass is made of amorphous silica (SiO[Formula: see text]) and is doped with Gd[Formula: see text] ions and possesses very interesting light emission properties with a luminescence band around 314 nm when exposed to protons. The fibers were manufactured at the University of Lille and tested at the TRIUMF Proton Therapy facility with 8.2-62.9 MeV protons and 2-6 nA of extracted beam current. Dose-rate dependence and quenching were measured and compared to other silica-based fibers also made by sol-gel techniques and doped with Ce[Formula: see text] and Cu[Formula: see text]. The three fibers present strong luminescence in the UV (Gd) or visible (Cu,Ce) under irradiation, with the emission intensities related directly to the proton flux. In addition, the 0.5 mm diameter Gd[Formula: see text]-doped fiber shows superior resolution of the Bragg peak, indicating significantly reduced quenching in comparison to the Ce[Formula: see text] and Cu[Formula: see text] fibers with a Birks' constant, k[Formula: see text], of (0.0162 [Formula: see text] 0.0003) cm/MeV in comparison to (0.0333 [Formula: see text] 0.0006) cm/MeV and (0.0352 [Formula: see text] 0.0003) cm/MeV, respectively. To our knowledge, this is the first report of such an interesting k[Formula: see text] for a silica-based optical fiber material, showing clearly that this fiber presents lower quenching than common plastic scintillators. This result demonstrates the high potential of this inorganic fiber material for proton therapy dosimetry.

We investigated the potential of a multimode (50- $\mu \text{m}$ core diameter) nitrogen doped silica-based optical fiber for X-rays, protons, and $\gamma $ -rays radiation detection and dosimetry. X-rays results confirm that this N-doped fiber presents a strong radioluminescence (RL) around 550 nm when exposed to radiation. The RL observed from a few centimeter long samples linearly depend on the dose rate at least in the 1-mGy/s–50-Gy/s range. Low dose rate $\gamma $ -ray t ests demonstrate the radiation detection at dose rate as low as $40~\mu $ Gy/s with a 2-m-long fiber sample. This fiber is also associated with an optically stimulated luminescence (OSL) when exposed to a 1064-nm laser light postirradiation. This OSL signature provides shortly after the irradiation a precise estimation of the accumulated dose at least in the 1-Gy–10-kGy range. Under proton exposure, we benchmarked the performances of the N-doped fiber with the ones of a conventional Markus chamber used by the TRIUMF proton-therapy team. This comparison highlights the potential of the small-size N-doped fiber to partially overcome the known limitations of commercial fiber-based dosimeters for medical applications. The obtained results are very promising for the future design of more complex spatially resolved beam monitoring systems. [ABSTRACT FROM AUTHOR]

We investigate the potential of innovative optical fiber bulk materials made by the sol-gel technique for real-time proton beam monitoring. Those types of glass are made of amorphous silica ( a -SiO2) doped with either Copper (Cu) or Cerium (Ce) ions. These optimized materials possess very interesting light emission properties when exposed to protons. For both types of glasses, online monitoring of the strong radiation-induced luminescence (RIL) allows to monitor the time evolution of the proton flux with ms resolution and the cumulated proton fluence can be precisely deduced by integrating the RIL signal. Furthermore, we showed that both samples present optically-stimulated luminescence (OSL) that could be exploited shortly after the end of the irradiation to reconstruct the cumulated fluence too. Preliminary tests presented in this paper have been performed at TRIUMF facility with high energy (30 - 63 MeV) protons at flux and fluences representative of proton therapy treatments. Obtained results demonstrate the potential of the developed optical materials for proton beam monitoring and permits to identify the needs for future experiments on microstructured fibers elaborated from these optical materials. [ABSTRACT FROM PUBLISHER]