The ATLAS 36" Scattering Chamber is designed to provide a flexible platform on which to mount a wide variety of experimental setups. A schematic top view of the 36" Scattering Chamber is shown in Figure III.17. The vacuum vessel is relatively small (36" diameter) where the upper half is rotatable by approximately plus/minus 45 degrees and the lower half is fixed. The upper chamber has five large (12" x 12") ports (in-plane and spaced by 45 deg.) on which large area detectors or vacuum extension boxes can be mounted, and a sliding vacuum seal for the entrance beam pipe to allow for the rotation of the upper chamber under vacuum. The upper chamber is attached to a large rotatable platform which provides the torque for rotation and serves as the platform for supporting the detector systems attached to the ports. The lower fixed chamber houses three independently movable gear rings on which detectors can be mounted, the target assembly, and the various feedthroughs for cables and controls. The vessel is constructed from stainless steel. Teflon seals are used in the rotating seal between upper and lower chambers, and the sliding seal at the entrance.
A modular system of tables is available for mounting detectors on the three internal rings. A cross sectional view of the main chamber with the movable and stationary rings is shown in this figure along with the dimensions relative to beam height. A variety of table tops are available with slots at five degree increments covering 30 degrees to 70 degrees. A long arm is available for mounting movable detectors in the extension boxes. In addition there is a stationary ring mounted at the outer edge of the chamber. The pedestal that sits on the table top and is used to bring the standard Si detector mounts to beam height is shown in this figure. The figure shows the detail of the keystone that is at the top of all 36" Scattering Chamber detector rails.
There are two vacuum extension boxes available that can be mounted to the chamber. Both provide an additional 29.25 inches radial distance from the target position. The boxes have a side access panel for mounting equipment in the box. The rear flange of the boxes can also accomodate the standard 12" x 12" port covers. The boxes can be mounted on adjacent faces of the main chamber. A schematic of the angular acceptance of the extension boxes is shown here.
The chamber is equipped with feed-thrus for gas detector systems and coolant circulators.
A variety of large port covers are available depending on the needs of the particular experiment that is setup. The port covers are made out of either stainless steel or aluminum. Specialized covers are available to allow insertion of detectors in the chamber wall and for neutron measurements. The various motions of the chamber are controlled manually. The basic specifications for the chamber are listed in the Table III.2 below.
MATERIAL
SIZE
PORTING
DETECTOR MOUNTING: INSIDE
OUTSIDE
TARGET ASSEMBLY
VACUUM SYSTEM
VACUUM PERFORMANCE
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