Lucia Giuliano

Objective. This study evaluates the performance of a simple secondary‐standard graphite calorimeter (SSCal) for absorbed‐dose measurements in ultra‐high dose‐rate (UHDR) electron beams, motivated by the need for reliable, traceable dosimetry for FLASH radiotherapy. Approach . The SSCal was calibrated against the primary absorbed‐dose standard at the National Physical Laboratory (NPL) and characterised in conventional 6-10 MeV electron beams. Monte Carlo (MC) simulations were used to derive detector‐specific perturbation and field‐size correction factors, including conversion from absorbed dose to graphite to absorbed dose to water. The SSCal was then tested in a 9 MeV UHDR beam (0.06–5.78 Gy pulse ⁻¹ ) at the Centro Pisano Flash Radiotherapy facility. Absorbed dose was determined using two independent approaches: (1) application of the calibration coefficient derived experimentally at NPL, and (2) first‐principles calorimetry. Alanine dosimetry provided an independent traceability route for cross‐validation. Main results . Calibration coefficients obtained at NPL showed minimal dependence on field size or beam quality. MC simulations indicated that perturbations were dominated by internal air gaps, with increasing magnitude at small field sizes. Corresponding beam quality correction factors enabled accurate application of the NPL calibration to the UHDR beam. Across all dose-per-pulse (DPP) values, the two dose determination methods agreed within 1%. The SSCal exhibited excellent linearity with pulse number and stable response for three pulses or more. A systematic Δ T /MU trend was observed only for single- or double-pulse exposures, for which transient perturbations in the beam current transformer signal provide a plausible explanation. In addition, or alternatively, the observed reduction in detector response may be influenced by non-linear heat-transfer effects within the calorimeter, potentially associated with cumulative heating and delayed thermistor equilibration. Agreement between SSCal and alanine was within ±1% for all but the highest DPP (5.71 Gy pulse ⁻¹ ), where a 2.6% deviation was observed under low-pulse conditions, which is consistent with the Δ T /MU trend. Significance . The results demonstrate that the SSCal provides stable, linear, and largely dose‐rate‐independent absorbed‐dose measurements in UHDR electron beams when appropriate MC‐derived corrections are applied, while indicating that a potential deviation from ideal response cannot be excluded at the highest investigated DPP values (>5 Gy pulse ⁻¹ ). These findings support suitability of SSCal as a reference-quality dosimeter for FLASH research and development.

We illustrate a theoretical study of a technique using high-energy muon beams (TeV class) propagating through thick (kilometer-long) crystalline rock layers subject to tectonic-induced stress, potentially capable of actively monitoring the temporal evolution of the pressure rise in seismic fault zones associated with earthquake triggering when the induced tectonic pressure reaches and overcomes the rock elastoplastic deformation limit. This technique could contribute to improving earthquake forecasting statistics in seismically active regions, offering support for seismic hazard assessment and prevention strategies. Active monitoring of the induced tectonic stress and its time evolution is achieved by remote sensing of the electric field generated in quartz crystals embedded in crystalline rocks by piezoelectric effects. In this context, tectonic pressure refers to the time-dependent stress field acting on the rock body due to tectonic forces, which adds to the time-independent lithostatic pressure resulting from the weight of overlying materials. High-energy muon beams transmitted through a rock layer subject to tectonic pressure will be affected in their transverse phase-space distributions by the piezoelectric fields, therefore transferring to a detector the information on the applied tectonic stress. Finally, we illustrate the design of a proof-of-principle experiment to be conducted in a standard accelerator laboratory, using moderate-energy muons (GeV class) propagating through granite slabs subject to a press-induced stress reaching the rupture limit. A zero-generation proof-of-principle test can also be performed using 20–150 MeV electron beams transmitted through single quartz crystals subject to variable pressure.

We illustrate a theoretical study of a newly conceived technique using high-energy muon beams (TeV-class) propagating through thick (km-long) crystalline rock layers subject to tectonic-induced stress, potentially capable of actively monitoring the temporal evolution of the pressure rise in seismic fault zones associated with earthquake triggering when the induced tectonic pressure reaches and overcomes the rock elasto-plastic deformation limit. This technique could contribute to improving earthquake forecasting statistics in seismically active regions, offering support for seismic hazard assessment and prevention strategies. Active monitoring of the induced tectonic stress and its time evolution is achieved by remote sensing of the electric field generated in quartz crystals embedded in crystalline rocks by piezoelectric effects. In this context, tectonic pressure refers to the time-dependent stress field acting on the rock body due to tectonic forces, which adds to the time-independent lithostatic pressure resulting from the weight of overlying materials. High-energy muon beams transmitted through a rock layer subject to tectonic pressure will be affected in their transverse phase space distributions by the piezoelectric fields, therefore transferring to a detector the information on the applied tectonic stress. Finally, we illustrate the design of a proof-of-principle experiment to be conducted in a standard accelerator laboratory, using moderate-energy muons (GeV-class) propagating through granite slabs subject to a press-induced stress reaching the rupture limit. A zero-generation proof-of-principle test can also be performed using 20-150\,MeV electron beams transmitted through single quartz crystals subject to variable pressure.

In this work, a detailed parametric study assessing the impact of low-conductivity coatings on the radio-frequency accelerating cavity quality factor and resonance frequency shift is presented. In particular, this study is aimed at proving the feasibility of molybdenum oxides deposited on copper to reduce the dark current in high-gradient applications due to its intrinsically high work function. In order to compute the effective surface impedance of the resulting layered structure, a transmission line-based approach is adopted. The present analysis demonstrates the potential effectiveness of molybdenum thin-films, which only slightly affects the accelerating cavity quality factor, with very low sensitivity to thickness and resistivity inhomogeneities.

To rapidly assess healthy tissue toxicities induced by new anti-cancer therapies (i.e., radiation alone or in combination with drugs), there is a critical need for relevant and easy-to-use models. Consistent with the ethical desire to reduce the use of animals in medical research, we propose to monitor lung toxicity using an ex vivo model. Briefly, freshly prepared organotypic lung slices from mice were irradiated, with or without being previously exposed to chemotherapy, and treatment toxicity was evaluated by analysis of cell division and viability of the slices. When exposed to different doses of radiation, this ex vivo model showed a dose-dependent decrease in cell division and viability. Interestingly, monitoring cell division was sensitive enough to detect a sparing effect induced by FLASH radiotherapy as well as the effect of combined treatment. Altogether, the organotypic lung slices can be used as a screening platform to rapidly determine in a quantitative manner the level of lung toxicity induced by different treatments alone or in combination with chemotherapy while drastically reducing the number of animals. Translated to human lung samples, this ex vivo assay could serve as an innovative method to investigate patients’ sensitivity to radiation and drugs.