Theoretical study of small signal gain of slow flow CW CO2 lasers with diffusion cooling Azizmorad Koushki, Kaveh Silakhori and Saeid Jelvani Eur. Phys. J. D, 67 9 (2013) 201 Published online: 26 September 2013 DOI: 10.1140/epjd/e2013-40169-3