Search for quarks using a flash tube chamber

A large flash tube chamber has been used at Durham to search-for e/3 charged particles (quarks) in extensive air showers where the local electron density is greater than 40m(^-2). The response of the detector to relativistic muons was measured and the equivalent characteristics for relativistic e/3 quarks calculated. The response for the more energetic muons in air showers was also measured. In a running time of 2,570 hours no definite quark tracks have been detected and the limit on the charge e/3 quark flux was set as: I<8.0 10(^-11) cm(^-2) sec(^-1) st(^-1). No non relativistic heavy mass particles, irrespective of their charge, were detected in the chamber from measurements on two body elastic collisions of EAS particles with essentially free protons.