Objective: Ionization chambers, mostly used for beam calibration and for reference dosimetry, can show high recombination effects in pulsed high dose rate proton beams. The aims of this paper are: first, to characterize the linearity response of newly designed Asymmetrical Beam Monitor Chambers (ABMC) in a 100 to 226 MeV pulsed high dose rate per pulse scanned proton beam; and secondly, to calibrate the ABMC with a PPC05 (IBA Dosimetry) plane parallel ionization chamber and compare to calibration with a home-made Faraday Cup (FC). 
Approach: ABMC response linearity was evaluated with FC and a PTW 60019 microDiamond detector. Regarding ionometry-based ABMC calibration, recombination factors were evaluated theoretically, then numerically, and finally experimentally measured in water for a plane parallel ionization chamber PPC05 (IBA Dosimetry) through ks saturation curves. Finally, ABMC calibration was also achieved with FC and compared to the ionometry method for 7 energies. 
Main results: Linearity measurements showed that recombination losses in the new ABMC design were well taken into account for the whole range of the machine dose rates. The Two-Voltages-Method was not suitable for recombination correction, but Jaffé’s plots analysis was needed, emphasizing the current IAEA TRS-398 reference protocol limitations. Concerning ABMC calibration, Faraday cup based absorbed dose estimation and PPC05-based absorbed dose estimation differ by less than 6.3 % for the investigated energies. 
Significance: So far, no update on reference dosimetry protocols is available to estimate the absorbed dose in ionization chambers for clinical high dose rate per pulse pulsed scanned proton beams. This work proposes a validation of the new ABMC design, a method to take into account the recombination effect for ionometry-based ABMC calibration and a comparison with Faraday cup dose estimation in this type of proton beams.