Ckfinder Thumbnails not created

I have a problem please someone help me , I'm using ckfinder demo version and thumbnails are not created in it file permissions are all set to 777 , this is my code
$config['Thumbnails'] = Array(
'url' => $baseUrl.'_thumbs',
'directory' => $baseDir.'_thumbs',
'enabled' => true,
'directAccess' => true,
'maxWidth' => 100,
'maxHeight' => 100,
'bmpSupported' => false,
'quality' => 80);

Can't find the problem