RBS HEDGEHOG – New 680 msr RBS Setup for fastest channeling experiments and ultra-high sensitivity measurements

RBS as one of the most widely used IBA methods requires a rather high beam fluence due to the small backscattering cross-section. Although the lack of measurement statistics can be compensated by a longer measurement time, this can only be applied to macroscopic beam spots and is not possible for sensitive samples or in a micro beam setup.

Larger detectors are an easy means to increase the covered solid angle, however this is limited in terms of kinematic broadening and decreasing energy resolution due to increasing detector capacitance [1]. Multi-detector setups overcome this limitation and are attracting increasing interest in various laboratories. Geometric constraints, mechanical robustness, the cost of multiple MCA systems, as well as the difficulty of simultaneously analyzing data from the individual detectors make this a difficult but worthwhile endeavor.

In this contribution, we report on our recently commissioned setup - namely, the "RBS hedgehog" located at the 3 MV tandem accelerator of the HZDR’ Ion Beam Center. The setup is equipped with 78 independent RBS detectors arranged in 5 concentric rings with backscattering angles from 165° to 105° covering a total solid angle of 680 msr - equivalent to 34% of the total backscatter angle. The 78 independent MCA systems can handle up to 8 Mega counts per second.

The presentation will start with an introduction to RBS technique, it’s advantages and disadvantages. It will be followed by a theoretical design study of the influence of different detector configurations on the kinematic broadening for different energies and ion species. We then introduction the used in-house designed and fabricated PIPS detectors and MCA systems and present initial experimental results for various projectiles and energies. Finally, we will illustrate its power at a future application of ion beam induced phase transformation in Ga2O3 [2].

[1] Klingner, N., et al. (2013), Optimizing the Rutherford Backscattering Spectrometry setup in a nuclear microprobe, NIMB, 306, 44-48. DOI: 10.1016/j.nimb.2012.12.062
[2] Azarov A., et al. (2023), Universal radiation tolerant semiconductor. Nat Commun. 2023 DOI: 10.1038/s41467-023-40588-0