## 4 Conclusions  
The ultra-short duration of laser-driven beams, in addition to the harsh experimental environment resulting from the required intense laser-matter interactions, limits the application of conventional dosimetry techniques in the measurement of these modalities [10]. As a result, novel strategies must be explored to overcome the unique challenges presented by such a harsh environment and, above all, by the UHDRs. The first absorbed dose measurements of a laser-induced proton beam with a calorimeter have been presented based on the use of a small-body portable graphite calorimeter developed and maintained at the NPL, representing an approach to laser-driven dosimetry that had never been explored. The NPL SPGC was operated within a laser-driven proton beam using the VULCAN-PW laser system of the CLF at the RAL. The absorbed dose was calculated for each of the irradiations performed through conversion of the radiation-induced temperature rises from each of the core thermistors. An additional measurement of the absorbed dose was carried out for each irradiation through the use of radiochromic film dosimetry, with film placed on the front surface of the SPGC. The decrease in the absorbed dose measured with the RCF compared with the dose measured with the SPGC indicated the amount of degradation of the beam after passing through the graphite jacket. The experimental setup was replicated for two of the shots in terms of the target used (i.e., shot 1 and shot 3), yielding the same degree of beam degradation. Radiochromic films have been used the most widely for the dosimetry of laser-driven beams. The outlined measurements conducted with both the SPGC and RCF indicate the ability of the calorimeter system to measure the absorbed dose from the radiation-induced temperature rise generated from the laser-target interactions, with the RCF acting as an additional measurement technique of the dose delivered. Furthermore, each of the shots, independent of the setup or target used, show good consistency in terms of the temperature rise measured by each of the thermistors. For dosimeters that are reliant on the use of electronics to some degree, the presence of a large EMP generated during the laser-target interaction may pose potential damaging effects to the equipment and/or signal. The excellent signal-to-noise ratio observed in the temperature curves indicated a lack of such distortion, with no evident effects of the EMP present in the calorimeter system. Nevertheless, the induced temperature rises for each shot producing dose values on the Gy level, alongside the excellent signal-noise ratio and broad consistency with RCF measurements, demonstrate the ability of this device to operate within the environment of a high-power laser system. The limited number of irradiations performed, whilst being sufficient to demonstrate the proof-of-principle, should be expanded upon to improve the statistical variability, verify the accuracy and better assess the achievable level of uncertainty for calorimetry techniques in measuring the absorbed dose generated by laser-driven proton beams. For this article, the authors stated have contributed to the writing of this, in addition to the contained work in the following degree: methodology, S.M., F.R., A.S. and N.L. ; software, N.L. ; experiment preparation and data acquisition: S.M., N.L., G.M. and F.R. ; formal analysis, S.M. and N.L. ; writing--original draft preparation, S.M. ; writing--review and editing, S.M., A.S., F.R., N.L., M.B., G.M. and A.M.; supervision, F.R., A.S. and M.B. All authors have read and agreed to the published version of the manuscript. **Funding:** This project, 18 HLT04 UHDpulse, received funding from the EMPIR programme co-financed by the Participating States and from the European Union's Horizon 2020 research and innovation programme. We also acknowledge funding from EPSRC (grant EP/K022415/1). **Institutional Review Board Statement:** Not applicable. **Informed Consent Statement:** Not applicable. **Data Availability Statement:** Not applicable.