The CDF Run II Silicon Design

To meet these goals, a central vertexing portion of the detector called the SVX II was designed, consisting of double-sided silicon sensors with a combination of both 90-degree and small-angle stereo layers[6,11]. The SVX II is nearly twice as long as the original SVX and SVX $^{\prime}$ , which were constrained to fit within a previous gas-based track detector used to locate the position of interactions along the beam line. Further studies showed that this functionality could be provided by the SVX II itself, so the gas-based vertex detector was removed from the design and replaced by an additional set of silicon detectors called the Intermediate Silicon Layers (ISL)[6,12].

**Figure 3:** A side view of half of the CDF Run II silicon system on a scale in which the coordinate is highly compressed.
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Due to readout speed and capacitance limitations that were most severe for the stereo layers, the readout electronics for the SVX II were designed to be mounted as close as possible to the sensors. The large instrumented length of silicon along the beam pipe requires these electronics to be located within the active sensitive volume, with resulting negative consequences on impact parameter resolution. To mitigate these effects, a layer of silicon called Layer 00 was added to the design at very small radius[10]. For capacitance and space reasons, to minimize material, and to allow large bias voltages to be used to ensure depletion even after extensive radiation damage, this layer is single-sided. The combined Layer 00+SVX II

ISL final design shown in Figure 2 functions as an integrated silicon tracker that recovers excellent $r\phi$ impact parameter resolution without unduly affecting the

resolution of the experiment.

**Figure 4:** An end view of the CDF II silicon system including the SVX II cooling bulkheads and ISL support structure.
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A schematic view of the principal active components of the CDF Run II silicon system is given in Figures 3 and 4. The side view shown in Figure 3 is a cross-section of one half of the silicon tracker, using a compressed

scale. Figure 4 shows an end view of the CDF II silicon system including the SVX II bulkheads and ISL support frame. The total amount of material in the silicon system averaged over azimuthal angle and

varies roughly as 10% of a radiation length divided by the sine of the polar angle in the region of pseudorapidity $\eta$ between 0 and 1. The average material traversed by particles increases to roughly twice this value for $1\le\eta\le 2$ due to the increased likelihood to encounter cables, cooling bulkheads, and portions of the support frame.

**Figure 5:** End view of the innermost three layers of the CDF Run II silicon system, showing Layer 00 along with the first two layers of the SVX II region. The Layer 00 electronics (not shown) are mounted beyond the active volume for vertexing. The SVX II electronics are shown just outside and just inside of each of the layers drawn.
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