Efficiency and Position Resolution

Before installation the Pad Chambers were tested with cosmic rays. In studies of efficiency and position resolution, a triggering system with large plastic scintillators read out by photomultipliers were used. A more detailed description of the setup and measurements can be found in paper I.

The efficiency measurements were carried out by varying both the anode wire voltage and the pad threshold setting. The results are shown in fig. 2.4.

Figure 2.4: Efficiency curves for PC1/2/3 with

$\bullet$ varying high voltage and constant threshold (top)
$\bullet$ varying threshold and constant high voltage (bottom)

The results are shown also for the case when only two fired pads in a cell are required to get a valid hit (2 pads min.).

=14cm images/efficiency1.eps

=14cm images/efficiency2.eps

The operating voltages are set to 1700 V for PC1, 1840 V for PC2, and 1880 V for PC3. The operating thresholds are set to 5.4 fC, 7.2 fC, and 7.2 fC respectively. Efficiency values for these settings are shown in table 2.1.

Table 2.1: Efficiency at operational settings.

	PC1	PC2	PC3
Efficiency	99.6 %	99.8 %	99.8 %

In the position resolution measurements, performed for PC1 and PC2, an additional chamber (PC1) was used as a reference. The results are presented in table 2.2.

Table 2.2: Position resolution along and across wires.

Position resolution ($\sigma$)	PC1	PC2
Along wires	1.7 mm	3.1 mm
Across wires	3.4 mm	5.0 mm