He held a leading position at CERN's Antiproton Accumulator, a machine that was part of the infrastructure connected to the UA1 and UA2 experiments, where the W and Z bosons were discovered in 1983.

[3] [4] During his nearly 40 years as a staff member at CERN he held technical and management positions such as in beam diagnostics, instrumentation, accelerator studies, controls, testing of superconducting magnet and safety.

This machine created antiprotons for the Super Proton Synchrotron, and was part of the infrastructure that led to the discovery of the W and Z bosons for which Carlo Rubbia and Simon van der Meer received the 1984 Nobel Prize in Physics.

During his tenure at CERN, he was associated with Fermilab for the commissioning of an antiproton source 1985 and 1986 and at the Los Alamos National Laboratory where he collaborated on Proton Storage Ring in 1989.

[10] Over 7 years Chohan led this international team which fully tested, qualified and trained up about 1300 superconducting magnets for use in the LHC.