[SOLVED] Unibeast stuck on "copying files"

Hello
I have an iMac running Yosemite
I downloaded El capitan installer
I put my system in english and allows apps from anywhere.
I format my Kingston 16gb then run unibeast.
It stucks on "copying files" and after 10-15min the USB pops up called "OS X Base system" and nothing more...

Tried differents USB ports and 8gb key but I have the same problem..

I don't know what to do