How to stop a session in asp.net

hello ,
in my website has two login sperate one for user and one for admin

suppose i login as user and add tab and open in site and login as admin

its work but when i do logout in user then is logout from admin as well

i want to if i login in both area user, admin in same browser  then i logout user then admin still login

but in my case all session stop

is any way to stop any perticular session stop and rest session work