Tracker (MWPC)
For the C2, C3, and C4 chambers, we will reuse the existing MWPC chambers
which were used in the previous E246 experiment. They are placed at the
entrance (C2) and exit (C3, C4) of each magnet gap. Since the C2, C3, and
C4 chambers have to be operated under the strong field of the spectrometer,
a planar MWPC with cathode readout was chosen. The anodes are 20-μm
gold-plated tungsten wires strung with 2 mm pitch along the momentum-sensitive
directions. The two cathode planes are located above and below the anode
plane. The distance between the cathode and anode planes is 6mm. The cathode
planes are made of a 25- μm Kapton foil with copper coating stripes of 18
μm in thickness. The width of the strip is 9 mm in width and the spacing
between strips is 1 mm. A mixed gas of Ar (50%) and ethane (50%) is used
as the operating gas. High voltage of +4.0kV is supplied to the anode,
and the cathode signal is used for the hit position determination. Typical
position resolutions are ~200 μm.
Overview
