Overview of the 4.6m Test Chamber

Japanese version is here

Test Chamber Geometry

A picture of the test chamber is available below.
A picture of the 4.6m chamber
The chamber has been built to study the feasibility of a precision central drift chmber with a large wire length. The chamber has mini-jet cells each containing 5 sense wires made of gold-plated tungsten. The wirers are 30 microns in diameter and 4.6m in length. The field wires are, on the other hand, made of aluminium and have a diameter of 125 microns.

Wire Position Measurement System

The most difficult part of the construction of a long chamber is the control of wire positions which are subject to gravitational and electrostatic sags. We have developed a wire position measuring system which consits of two telescopic microscopes, one for horizontal and one for vertical positions, equipped with CCD cameras.
Wire position measurement system
The viewable area has a dimension of about 1mm times 1mm with a focal depth of about 1mm. The horizontal and vertical positions of the telescopes are measured by precision linear scales with a spatial resolution of a few microns and the position readings are electrically logged together with the wire image. To see a sample image of a wire illuminated by a laser beam, click here.

Cosmic Ray Tests

Cosmic ray tests have been carried out with a candidate gas mixtrue (CO2:Iso-Butane=90:10) provided through a gas mixing system using mass flow meters. The system is also equipped with a O2 monitoring system.
Two scintillation counters sandwich the 4.6m chamber and their coincidence signals a cosmic ray passage, thereby triggering the data taking system (see this for our setup). The positions of the two scintillation counters are moved to study incident angle dependence (see this for instance).
Sense wire signals are sent to 8-bit FADC's driven at 500 MHz through charge sensitive pre-amplifiers. Typical chamber signals look like this.

Preliminary Results

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kurihara@jlcux1.kek.jp Mar 14, 1994