Written: IJDM 18/01/02

Cell dimensions
The target cell is 26mm wide x 35mm high x 15mm thick.
The internal corners have a 2mm radius, so the total
volume is ~ 13.598 cm^3.

Thickness
The windows bow out slightly due to the pressure of the water enclosed.
This still has to be measured accurately.

Orientation
The cell is designed to be mounted at 90 to the photon beam.

Windows
The front and rear windows are 0.06mm mylar foil.

Nuclei/cm^2
When filled with H2O the target has 5.02 x 10^22 water molecules per square cm.
The mylar foils consist mainly of O, C and H in proportions roughly (0.20, 0.70, 0.10)
by weight. The number of additional O atoms is about 1.8 x10^20/cm^2.
The H atoms should not contribute to cross section. The number of C atoms is about
6.3 x 10^20 atoms/cm^2. (about 1.2% of the Oxygen content).
The proposal is based on a C target with 5x10^22 atoms/cm^2.

Energy Loss
Proton energy losses in the windows are negligible.

Mounting Plate
The target is mounted on aluminium plate 82mm wide x 55mm high x 3mm thick.
This plate can then be mounted in turn on the target ladder.
The centre of the target is 7.5mm in front of the Al support plate and this
should be taken into consideration in mounting the target.

Beam Size
With a 5mm diameter collimator the expected beam spot size at the target is
15mm diameter. This is well within the target cell aperture.

Side Walls
The side walls are 7mm thick perspex. The walls have to be this thick to provide
a surface to glue the windows.

Energy Loss Baffles
To equalise energy losses of protons emitted at different depths in the target
perspex energy loss baffles are attached to the front of the target. These
are designed to equalise the path lengths of protons emitted at 60 degrees
ireesepective of the depth they are produced in the target. The baffles take
into account both the path lengths through the side walls and through the water.
Particles emitted at smaller angles will have larger energy losses, but will
miss the PiP and TOF detectors. Particles emitted at larger angles will have
a partial compensation for path length traversed.