## 5 Discussion and Conclusions
### Detectors and Readout Electronics  
To record the hit position of protons and \(\alpha\)-particles, our instrument requires a position-sensitive sensor plane. This can be achieved by the use of either a micro-channel plate (MCP) or a channel electron multiplier (CEM). Moreover, we explicitly require a high time resolution while maintaining high count numbers. This can raise a concern regarding MCPs as their saturation count rate is around 1 MHz, depending on the detecting surface area. On the other hand, CEMs present higher count rates independent of the hit area but may induce a lower velocity resolution due to their size. [PERSON] et al. [11] use 32 CEMs to achieve a 1.5\({}^{\circ}\) resolution in their high-cadence THOR instrument design. For MPA, the sensor has a rectangular shape (strip) and pixels are organized along the \(z\) axis. Figure 15 shows an anode array in the case of an MCP detector.  
While we do not show the MCP itself in this figure, we represent the MCP-produced electron clouds as gray circles. An acquisition chain is responsible for recording every hit and its position along the \(z\) axis. A pixel (yellow rectangle in Figure 15) can correspond to a unique anode wire or resistive strip, or a combination of neighboring wires/strips, depending on the trade-off between velocity resolution required for a particular measurement and counting statistics (the summation of counts from multiple wires/strips defines the number of counts in a pixel if multiple wires/strips are combined). We recommend that readout electronics composed of amplifiers and discriminators are multiplexed to reduce the number of components required.  
Conceptualization, B.C. and G.N.; methodology, B.C., G.N. and D.V.; software, B.C.; validation, G.N. and D.V.; formal analysis, B.C.; investigation, B.C.; writing--original draft preparation, B.C.; writing--review and editing, B.C., G.N. and D.V.; visualization, B.C.; supervision, G.N. and D.V.; project administration, G.N. and D.V.; and funding acquisition, D.V. All authors have read and agreed to the published version of the manuscript.  
This research was partly funded by STFC Consolidated Grant ST/S000240/1 and STFC Ernest Rutherford Fellowship ST/P003826/1.  
Figure 15: Position-sensitive anodes and a representative pixel. The anodes are represented by the blue lines. They consist of conductive wires that detect the current generated by the electron beams (gray circles) and determine the vertical \(z\) position of the beam based on the knowledge of which wire has been hit. A pixel is defined as either a single anode or a collection of multiple anode wires and is represented here as a yellow rectangle. The two permanent magnets, which delimit the magnetic chamber, are represented by the dark rectangles at both sides of the pixels.  
**Acknowledgments:** The authors thank [PERSON] for helpful discussions. The code written for the simulations in this publication is publicly available at [[https://github.com/c1-94/MPA](https://github.com/c1-94/MPA)]([https://github.com/c1-94/MPA](https://github.com/c1-94/MPA)).  
**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.