Design

As mentioned in the previous sections, tilting the Enge spectrometer with respect to the Splitter magnet destroys its original symmetry of the optics. Therefore, it is essential to measure the particle's incident angle as well as its position at the exit of the spectrometer. In order to achieve a momentum resolution of 4$\times$10$^{-4}$ (FWHM), position and angular resolutions of 100$\mu$m and 2 mr (rms), respectively, are required for trajectories with incident angles that vary by more than 50 degrees across the focal plane. Furthermore, the detector should stand for a singles rate as high as 10 MHz.

A drift chamber with a honeycomb cell structure was employed to meet the above requirements. The drift chamber parameters are given in table 17 and its outlook can be seen in figures 55 and 56.

表 17: Honeycomb drift chamber parameters

layer configuration	xx' uu' xx' vv' xx' (u,v $\pm 30^\circ$ tilt)
effective volume	$12^H \times 100^W \times 30^T cm$
cell size	honeycomb (hexagon) with side 5 mm
anode wire	gold-plated tungsten $\phi$ 20$\mu$m
shield/field wire	gold-plated aluminum $\phi$ 80$\mu$m

The read-out electronics is designed to use the same amplifier-discriminator cards (N277L) as those for the HKS drift chambers.