Downstream stations

Downstream of the target and upstream of the first magnet, tracking is performed by a system of silicon microstrip detectors referred to as the Silicon Strip Detector (SSD). There are four stations of detectors, as shown in spec:target_region and labeled as ``SSD.''

Each station has 3 views. With respect to the horizontal axis of the experiment, the three views are oriented at $-135\degree$, $-45\degree$, and $-90\degree$ from most upstream to most downstream. The planes within a station are separated by 5 mm. The first three stations are separated by 6 cm; the last two stations are separated by 12 cm.

Each plane consists of two regions, an inner region with finer pitch strips and an outer region with more widely spaced strips. The most upstream station has $25~\mu\mathrm{m}$ inner strips and $50~\mu\mathrm{m}$ outer strips. The remaining three stations have $50~\mu\mathrm{m}$ inner strips and $100~\mu\mathrm{m}$ outer strips. Each of the 12 planes has 688 channels of ADC readout.

The properties of the SSD stations are summarized in spec:ssd_internals and are described in greater detail in Bellini:1986cg.

 

Table 3.1: The properties of the SSD planes. Station 1 is the most upstream station (closest to the target).

	Active Area
Station	Total	High Res.	Strip Pitch
1	$2.5 \times 3.5~\mathrm{cm}^2$	$1.0 \times 3.5~\mathrm{cm}^2$	25 , 50
2	$5.0 \times 5.0~\mathrm{cm}^2$	$2.0 \times 5.0~\mathrm{cm}^2$	50 , 100
3	$5.0 \times 5.0~\mathrm{cm}^2$	$2.0 \times 5.0~\mathrm{cm}^2$	50 , 100
4	$5.0 \times 5.0~\mathrm{cm}^2$	$2.0 \times 5.0~\mathrm{cm}^2$	50 , 100