Make custom post type archive for administrator only

can you add this code in your archive-ticket.php before get_header().

please check below snap for the same.

enter image description here

$user         = wp_get_current_user();
$roles        = (array) $user->roles;
$current_role = $roles[0];
$allowed_role = array('administrator');
if (!is_user_logged_in() || !in_array($current_role, $allowed_role)) {
    wp_redirect(site_url());
}

Thanks.