2009 July:

The SciFi2 detector was designed and is assembled in the frame of a PhD thesis [1]. It is shown in fig. 2 (left side). An active area of 66cm x 51cm is obtained using 640 scintillating fibers with a diameter of 3mm. The planar detector covers an angular range of ± 10° in the x-direction and ± 8° in the y-direction. A central hole (4cm x 4cm) allows the beam to pass through. Groups of 16 fibers are glued together to form a so-called module. The profile of one module is shown in fig. 2 (right). The design guarantees a minimum path length (about 2mm) for particles traversing the circular fibers. The modules are arranged in two layers twisted by 90degrees. The signals from each module are read out by 16-channel photomultiplier (Hamamatsu H6568).

By now, the modules for one layer are constructed and all components of the frame are ready. All photomultiplier and discriminators are delivered and tested. The detector will be completed in the early summer of this year.

The analogue signals from the photo tubes of both detectors are fed to 16-channel leading edge discriminators. The threshold for each channel can be programmed individually via a serial bus. The discriminator outputs then feed multihit TDC modules via a standard LVDS signal format. This signal processing and readout is already successfully used in a very similar way in the Crystal Barrel setup.

The timing resolution of the detectors is about 2ns (FWHM). It basically results from the varying distance of particle hits to the corresponding photocathode.


[1] S. Böse, doctoral thesis, Bonn (in preparation)