Beam-intensity measurements

Most of the diagnostics concept for monitoring the Super-FRS beam intensity and transmission are FAIR accelerator based: particle detection combination (PDC), with three types of particle detectors (SEM, IC, plastic scintillator or diamond detector) at the entrance of the Pre-Separator (target) and the Main Separator to measure the beam current and counting. Special care is needed at the target region for the signal transportation and the front-end electronics location due to the high radiation level.

As an example, a two-gap IC with 50 mm diameter active area used to measure 12C ion-beam intensity is shown, see figure below. The detector was fit in a gas sensitive housing with stainless steel foils (0.1 mm) separating it from the vacuum. The IC analogue signal was fed into a current to frequency converter.

[1] S. Schlemme et al., GSI Scientific Report (2015) p. 369

At the highest particle rates it is foreseen to operate a SEM transmission monitor equipped with thin metallic foils (SEETRAM) in current mode. The IC/SEETRAM current is calibrated by using a fast-counting diamond detector.

[2] F. Schirru et al., Diam. Relat.  Mater. 49 (2014) 96

The signal properties (amplitude, slope and charge) of a pcCVD diamond detector exposed to 60 h of irradiation corresponding to an integrated flux of 6.2⋅ 1013  12C/cm2 were studied as a function of the accumulated flux [3].

[3] S. Schlemme et al., Diam. Relat. Mater. 99 (2019) 107536

The counting efficiency of a a large 20.0× 20.0× 0.3 mm3 pcCVD diamond detector was studied as a function of the beam rate and for different values of absorbed ions [4].

[4] F. Schirru et al, 2020 JINST 15 C04040

Partners: TU Darmstadt and GSI