Easier than i expected
set xml_content "?xml version=\"1.0\" encoding=\"UTF-8\"?[$doc asXML -indent 2 -escapeNonASCII]'"
set xml_filename "/var/lib/aolserver/trunk2/packages/photo-album/www/resources/xml/photos-temp.xml"
set fp [open $xml_filename w]
puts $fp $temp_iuri
close $fp
cheers!