SSAS: Move tempdb database
Connect to your Analysis Services server in SQL Management Studio.  Right-click the server, then click Properties in the menu.  In the Properties dialog, check the "Show Advanced (All) Properties" check box at the bottom of the list.  Then, in the grid above that check box, set the location you want for SSAS TempDB in the "TempDir" setting.

You will have to restart SQL Server Analysis Services for the change to take effect.