Application of ionization detectors in low energy IBA

Contact:
M. Döbeli

M. Döbeli

The main goal of this project is to investigate the possibility to apply newly developed gas ionization detectors with ultra thin entrance windows and low-noise electronics in Ion Beam Analysis.

ERDA (Elastic Recoil Detection Analysis)

As part of the PhD thesis of Christian Kottler, a new spectrometer for low energy heavy ion ERDA has been developed. Presently, improvements to this spectrometer are implemented and the potential of ERDA to discriminate between isotopes and to measure isotope ratios is examined.

HIBS (Heavy Ion Backscattering Spectrometry)

HIBS offers much better mass resolution for heavy elements and often superior depth resolution than standard RBS. Common silicon detectors are not practical for this purpose due to radiation damage by heavy projectiles. In the course of the PhD thesis of Marc Mallepell, a cylinder-symmetric gas ionization detector has been designed and constructed. It is of annular shape and can be placed in line with the incident beam. The detector is equipped with a circular array of silicon nitride entrance windows which warrants a small kinematic broadening of the energy resolution at a reasonable solid angle. The length of the chamber and the maximum possible gas pressure allow the detection of particles in a wide energy range. The electrode design and the amplifier chain are optimized for low electronic noise. With 50 nm silicon nitride windows the gas detector outperforms standard implanted silicon detectors for all ions heavier than Li. Even for 2 MeV He projectiles a similar resolution as with a Si detector is obtained (see figure).

The documentation  of this detector can be accessed here.

Presently miniaturized gas ionization detectors with a size of a few cm are developed and their performance in HIBS and standard RBS measurements is beeing investigated.