Design and set-up of the neutron guides at FRM-II

The new neutron source FRM-II is designed with one especially large beam hole (diameter at the outer pool wall ∝1.2 m), which looks onto a cold source of D2. Six neutron guides start inside this beam tube and enter (through an 18 m long guide tunnel) a guide hall ∝ 50 m long and ∝25 m wide, inside which more than a dozen instruments can be installed. Most of all other horizontal beam tubes can be equipped with one or two guide tubes, either thermal guides (beam tubes SR-5 and SR-8) or cold guides (beam tube SR-4). Moreover a very cold beam can be extracted through a vertical guide directly from inside the cold source. (orig.)