A 1 m radius spherical electron drift chamber for the measurement of relativistic heavy nuclei

Abstract The performance of the spherical drift chamber of the BUGS IV (Bristol University Gas Scintillator) cosmic ray detector is presented. The 1 m radius spherical chamber employed ArN 2 gas scintillation, gas-proportional scintillation, and electron drift timing to provide charge, energy, and pathlength correction information. The details of the scintillation and drift processes are presented and the combination of these techniques in the BUGS IV central drift chamber are discussed. The performance of a recent exposure of the BUGS IV central spherical chamber to relativistic cosmic ray iron nuclei is presented. It is shown that the chamber provided pathlength corrections to all elements of this multi-detector experiment with relative uncertainties of less than 2% for 90% of all impact parameters. The maximum uncertainty for the largest impact parameter events remained less than 5%. Model drift waveforms are derived and shown to be in excellent agreement with the observed data.