## 3 ELIMAIA Dosimetry Description
### The In-Air Final Section for Dosimetry and Sample Irradiation  
In the ELIMAIA beamline, the transported particles, once selected in energy, will reach the in-air final section through a kapton window placed in a dedicated flange, separating this section from the in-vacuum one (Figure 6). Figure 6: (**a**) 3D model of the in-air final section of the ELIMAIA beam line. Transported particles come from the left: (1) flange, separating the two sections of the beamline and housing the secondary emission monitor (SEM) and TOF detectors. (2) Ion collector (IC) for the in-transmission dose monitoring. (3) Final irradiation point, including the Faraday cup (FC) and sample irradiation system (SIS), respectively, used for absolute dosimetry and sample irradiation. All the elements are installed in translating stages to change their relative position; (**b**) picture of the in-air final section for dosimetry and sample irradiation installed along the ELIMAIA beamline. The same flange will also house the secondary emission monitor (SEM); which is one of the detectors composing the ELIMAIA dosimetric system; and a diamond detector for time of flight measurements; both controlled by dedicated actuators. The SEM is basically a beam current monitor that; once cross calibrated with a reference detector; can be also used as a on-line in-trasmission dose monitor. Moreover; thanks to the scattering of the incident protons; it contributes to the beam homogeneity at the final irradiation point. Further details on that will be given in the next section. The total length of the in-air section is about 3 m and the relative positions of all the single-shot operating devices, as well as of the detectors for dosimetry can be easily changed, according to the user requirements. A collimation system, aiming to cut the beam later tails, will be also included in order to provide the final shape of the beam at the irradiation point, with diameters ranging between few hundreds of \(\upmu\)m up to 1 cm. Because of the flexibility of the system, both for position and beam diameter, it has not been included in the picture. The first detector, which is traversed by the transported beam in air, is an in-transmission multi-gap ionization chamber (MGIC), aiming to on-line monitor the dose shot-by-shot (Figure 6). The MGIC is composed by two independent gaps, operated at different voltages, and it is a monitor that, once calibrated with an absolute detector for dosimetry, measures the dose delivered at the irradiation point. Specifically, the detector for measuring the absolute dose at the ELIMAIA beam line is a Faraday cup, which is able to measure the collected charge once coupled to an electrometer [32]. The information on the transported charge by the primary particles, coupled by a measurement of the beam area and the energy spectrum, provides the dose at the irradiation point. A sample irradiation system (SIS) can be easily placed at the same position where the beam has been previously calibrated, in order to deliver specific amounts of dose per sample, remotely controlling the sample positions (Figure 6). Further details for all the mentioned elements will be given in the next section. The output from the detectors is processed by a dedicated software, which collects the acquired signals and provides a feedback for the laser system, once the required dose at the irradiation point is achieved. Figure 6b shows a picture of the in-air final section for dosimetry and sample irradiation installed along the ELIMAIA beamline. All the elements are placed in translating stages assembled in linear rails, in order to easily change their relative positions (Figure 7). In particular, both the MGIC and the stage where the SIS and the FC are mounted can be translated along the beam direction, in order to change their relative longitudinal position and to be placed closer to the kapton window, if low energy irradiations are performed.