Here is the information I’ve found on several sites.
1. You *must* put the cross-tab itself in Group Header #1 (pre-req).
2. The GH1 field would be the field you want to break on, in your case, “department” (via right-click. “Change Group”, selecting department rom the first dropdown on the “Common” tab).
3. Right-click on the Goup Header in the Design tab, select “Section Expert”.
4. Select the “New Page After” checkbox.