CFHT, Instruments, Spectroscopy, CAFE.

CAFE Description

Greg Barrick and Jacques Baudrand

Pictures by Jacques Baudrand

10 January 2001

The CAFE is an instrument to replace the old coude mirror train with a fiber optic. The project consists of 3 pieces:

1) An optical bench mounted to a port on the Cassegrain Bonnette which contains a holder for the fiber, feed optics for the fiber, flat field and spectral (ThAr) calibration lamps, feed optics for the calibration lamps, and a mechanism to select between telescope feed and calibration feed. The light from the telescope will be fed into this optical bench using the Cassegrain Bonnette central mirror. The electronics for the optical bench will be controlled from a crate mounted on the Cassegrain environment.

2) Two fiber optic cables (one for spare) with microlenses on either end to shape the beam. The fibers will be ~28 m long.

3) Optics for injecting the beam into the Gecko Spectrograph. This will be a Bowen-Wallraven slicer to which the fiber cable will be attached. The beam will be injected into the spectrograph at f/20 as is currently the case with the coude train.

The was built for CFHT by Jacques Baudrand, Rene Vitry, and Michel Lesserter at the Observatoire de Paris-Meudon.

CAFE was first delivered to CFHT at the end of September 1999 and a preliminary acceptance test was held at CFHT with Jacques Baudrand and Rene Vitry of OPM during the last two weeks of October. (Click here for a photograph of some of the CFHT staff involved in the acceptance test courtesy of Jacques.) The tests went well with much progress being made on the controller software in the two weeks Jacques and Rene were here. Optically and mechanically, CAFE was shown to be very stable and reliable.

CAFE returned to CFHT in mid-2000 and was used for the first time for science in July 2000. CAFE is now a commissioned instrument at CFHT and is the primary feed for Gecko.

Below are some photographs of some parts of CAFE provided by Jacques.

Figure 1: F/20 output beam from the fiber link. Optical specification required for the CFHT high-resolution Gecko spectrograph.

Figure 2: Fiber link output extremity near the mechanical mount and precision connector.

Figure 3: CAFE output sub-assembly. To be mounted at the High-resolution Gecko spectrograph entrance (the image slicer is hidden inside the mounting behind the fiber connector).

Figure 4: All silica image slicer. All parts are assembled using molecular adhesion (big prism size: 10 mm)

Figure 5: CAFE Head central optical sub-assembly (top view). The precison connectors are ready to receive the fiber link mechanics.

Figure 6: CAFE Head central optical sub-assembly (bottom view).

Figure 7: Input fiber link mechanical extremity. A rod type microlens is bonded on top of the fiber core.

Figure 8: Output fiber link mechanical extremity. A rod type microlens is bonded on top of the fiber core.

Figure 9: CAFE Head fully assembled and ready to be mounted on the telescope.

Figure 10: CAFE Head with protective cover removed. In the first plane we can see the calibration facility with the halogen lamp and the ThAr source.

Pictures of the Electronics - 24 August 1999

Figure 1: The control rack for the CAFE contorl electronics.

Figure 2: The cards that make up the CAFE controller electronics.

Figure 3: The manual controller box for the CAFE control electronics.
Send comments to: Greg Barrick
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