GEM based TPC for beam monitoring

In recent years Gas Electron Multipliers [1] have proven to be reliable amplification stages at high beam rates, and can be used also in Time Projection Chambers [2]. Our group developed a 1 dm3 active volume double-GEM TPC[3] for RIBLL (the radioactive ion beam line at the Institute of Modern Physics, in Lanzhou, China), with spatial resolution of 50 um and 280 um. Custom designed FPGA data acquisition system enables rate capability for about 100 kHz mm-2, providing excellent track-by-track position and angular information, better than 0.1 mm and 1 mrad respectively. The wide dynamic range of the system enables identification from 4He up to 86Kr using ionization measurement. Two of these TPCs are planned to operate in tandem mode [4, 5] to filter off-time particles and to achieve a superior angular resolution.

[1] F. Sauli, GEM: A new concept for electron amplification in gas detectors, Nucl. Instrum. Meth. A 386 (1997) 531
[2] D.R. Nygren, The Time Projection Chamber: A New 4 pi Detector for Charged Particles, PEP Summer Study (1974)
[3] G. Galgóczi et al., A GEM based TPC for beam monitoring, JINST 15 C08027 (2020)
[4] F. García et al., A GEM-TPC in twin configuration for the Super-FRS tracking of heavy ions at FAIR, Nucl. Instrum. Meth. A 884 (2018) 18
[5] P. Legou, E. Mazzucato and F. Nizery, Sextant a very fast beam spectrometer, IEEE Nucl. Sci. Symp. Conf. Rec. (2007) 649