Products
Just some photos...
The essential features of the 2.3 liters prototype inner volume are clearly illustrated by the following pictures referring to the new version of the prototype realized in 2007. The right photo shows the field shaping system for the drift and multiplication volume:
- A copper circular cathode and a stainless steel structure of racetrack 20 cm large annular rings provide a uniform electric field in the sensitive liquid argon region;
- The racetracks are separated by a PEEK structure providing a conical shape to the sensitive volume;
- A system of level sensors is used to monitor the liquid-gas interface and to check it is placed few millimeters above the first grid, used to close the drift region (7.5 cm long). A second grid is positioned few cm above to guarantee the extraction of ionization electrons into the gas phase: the remaining grids ensure the proportional light production (see proposal).
To obtain the best
light collection, and a corresponding higher sensitivity, a high performance reflector layer (see photo on the left) sorrounds
the drift region and the internal surface of the whole inner detector: this guarantees that a higher percentage of
scintillation light reaches the four 3" cryogenic photomultipliers (PMTs) placed in the upper volume. The PMTs matrix (see bottom picture),
positioned few cm above the last grid, is used to simultaneously detect primary and secondary light signals induced by an interaction
in the liquid drift region.
The whole system is fully contained in a stainless steel, vacuum-tight cylindrical container, 30 cm large and 50 cm high (See picture on the left),
that is completely immerged in a liquid argon bath used to provide the coexistancy of liquid and gaseous phase in the inner detector. A 2 cm thick copper gamma shielding surrounds the central core.
