The HKS chambers are used to measure the trajectory position and orientation at the HKS focal plane in order to measure the particle momentum. Two sets of chambers will be used with a separation of one meter. Each set contains 6 coordinate planes (U, U', X, X', V, V'), therefore there will be 12 coordinate measurement planes (figure 39). The U and U' wires have an angle of 60 degrees with respect to wires in X and X' planes, while the V and V' have an angle of -60 degrees. This is to enhance the position resolution in the X direction. The X', U', V' planes are offset by half a cell size with respect to the X, U, V planes ,respectively, in order to increase the capability to resolve the left-right ambiguity.
Each chamber has an active area of 
cm
.
Spacing between a sense wire to
a field wire is 0.5 cm. Coordinate planes are separated by thin Cu-Mylar foil to
form cathode planes. The gap between two foils is 0.635 cm. Additional 0.635 cm
gap is inserted in between X and X' planes because of the amplifier-discriminator
card mounting plane. On the particle entrance and exit faces, one
extra empty gap plane is added for pressure equalization. All planes are made of
print-circuit-board (figure 40).
The Nanometric N277-L amplifier-discriminator cards are mounted on the center support board and distributed on the two long sides of the chamber. Each chamber needs 40 cards of them, i.e. 40 of the 16 channel twisted pair cables.
The basic design is the same as the SOS chambers except for the size and the additional gap in the middle between X and X' planes. The standard SOS chamber tracking code can be directly adopted by changing the wire map, size, and middle gap.