The 53-inch Chamber

This chamber is a general purpose vacuum vessel in the S2 vault, used for mounting large detector arrays surrounding a central target. It is expected to be used in conjunction with the neutron wall detectors.

Expanded Description

The 53-inch Chamber is a vertical cylinder with a thin aluminum wall at beam height. It is mounted immediately after the last superconducting quadrupole on the G-beamline in the S2 vault. Inside is a large aluminum stationary plate for mounting detector arrays such as LASSA or the MINIBALL. An air-locked target ladder rises from below with the capability to use chemically reactive targets, such as alkali metals. Eight ports are available for signal and high voltage feedthroughs, with a ninth used for vacuum instrumentation.

Downstream of the chamber is a large diameter beam tube leading to a faraday cup. The large diameter prevents interactions between the tube and any beam halo. Portable shielding is used around the faraday cup.

Technical Information

Status: Under construction.

Location: S2 Vault

Contact Person: Dave Sanderson

Technical Detail

The vacuum vessel is a vertical cylinder with an inner diameter of 135.9 cm. The detector mounting platform is approx. 53 cm below the beam axis. The upper half of the chamber is fabricated from aluminum and is lifted off for access. The beamline connections are on this section, so the bellows will need to be disassembled before opening the chamber. The lower section is fabricated from stainless steel and includes the ISO-200 ports for the feedthroughs and the vacuum system.

The vacuum system consists of a 2000 l/s turbo pump with its associated forepump and a separate roughing pump. The turbo has a gate valve so it can be left running during venting of the chamber. Due to a lack of control rack space, all the vacuum gauges have readouts on the transducers with an interface to the laboratory’s control system.

One of the feedthrough ports is used for vacuum instrumentation and valves. The other eight are available for electrical and cooling feedthroughs. S800 style ISO-200 feedthrough plates and 92” Scattering Chamber style feedthrough plates with adapters can be installed.

The target mechanism incorporates an airlock for using chemically reactive targets, such as metallic calcium. The positioning of the targets is manual with a range of three 1.90 cm. high frames. The target frames are chosen by the experimenter. A second port for a target mechanism is located in the top lid, with an ISO-80 flange, upstream and centered on the beam axis.

The exit beamline quickly opens up to 30.5 cm ID to prevent any beam halo from interacting with the beamtube wall. Immediately before the faraday cup at the end is a diagnostic station with viewer and a turbo pumping system.

A large vertical slab of steel is immediately behind the faraday cup for shielding during tuning with primary beams. On the sides, water jugs are stacked to block neutrons from the faraday cup reaching the neutron walls.

The S2 vault has the normal complement of utilities, including clean power. A large jib crane has the reach to remove the top of the chamber during venting.

The following figure shows a CAD model of the chamber with its exit beamline.