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Fibre slit mounting

In order to use ISIS with fibres, it is necessary to mount the fibre bundle slit end in a special structure. This structure is required to take into account the mechanical performance of the spectrograph and to allow the slit alignment with its optical axis.

As can be see in Figure 9, the fibres slit is placed such that the optical axis of the fibres is orthogonal to the optical axis of the spectrograph. A prism is used to make both optical axes coincide. This prism is mounted on a holder. The incoming light from the fibres crosses the holder through two 2mm wide slots. Several clips fix the prism to the holder. The slit is mounted onto a plate ; three kinematic seats allow the fibre slit to be aligned with the prism.

The prism - slit system is mounted onto a rotating plate which permits alignment between the slit image and the detector's spatial direction. Another plate, placed onto kinematic seats, holds the prism - slit mounting and allows it to be aligned with the optical axis of the spectrograph.

Finally, all these mechanisms are supported by the standard mounting to the ISIS slits but with two peculiarities: On the one hand, a stop piece is employed to centre the slit image in the detector. On the other, two pieces to clamp the protective cover of the slit are supported by the plate.

The bundle exits the mechanical structure of the spectrograph through a window opened in the ISIS box (Figure 9). Two portable plates were manufactured to adjust the bundle to the window. THe plates are joint to the bundle through a cable-gland of type GEWISS/GW52006.