Forward Drift Chamber Shift

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The Forward Drift Chambers

The Forward Drift Chamber (FDC) system consists of four identical packages, each having six chambers (cells). These are planar drift chambers with both wire and cathode strips being readout, in total 12,672 channels.

The cells within a package have independent gas volumes, but are separated with a flexible mylar membrane and therefore the pressure difference between the cells should never exceed 30~Pa. Positive (up to 2200V) and negative (up to 500V) HV is applied on the sense and field wires respectively with dark currents not exceeding 3 microA per HV channel.

The detector (including cables) emits a total power of about 1500~Watt, of which about 900~Watt inside the magnet, due to the LV applied on the detector pre-amplifieres. A cooling system using Fluorinert is used to keep the temperature on the pre-amplifiers below the permissible limit. The LV system should never be turned on if the cooling system doesn't work .


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