A 3‐nsec pulse of 600‐keV electrons has been used to ionize a CO2&sngbnd;N2&sngbnd;He medium from which laser pulses lasting up to 120 &mgr;sec have been obtained. The electron beam is nearly collinear with the laser axis and normal to the sustainer field. Pulse energies of 11.5 J have been obtained from the 75‐cm‐long device.