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General Description

-- PeterWintz - 04 Nov 2013

The central Straw Tube Tracker (STT) in the PANDA target spectrometer features a high-resolution spatial and momentum reconstruction of charged particle trajectories in a broad momentum range from about 100 MeV/c to 8 GeV/c. In addition, a particle identification of protons, kaons, and pions in the momentum region below 1 GeV/c has to be done exclusively by the STT, with a measurement of the particles' specific energy-loss. The STT design is optimised for a minimal material budget by the technique of self-supporting straw layer modules. The detector is essential for the online track reconstruction and event identi fication in the continuous, trigger-less data-acquisition at PANDA.

The detector consists of 4636 straw tubes, each with a length of 1400 mm and 10 mm inner diameter. The wall thickness of the aluminised mylar film tube is 27 µm. The tubes are pressurized to 1 bar overpressure (2 bar absolute pressure) and glued together to close-packed, self-supporting multi-layers which sustain the wire tension and tube stretching equivalent to 230kg and 3.2 tons (sum for 4636 tubes).

Specification Number
Straw number 4636
Straw length 1400 mm
Straw diameter 10 mm
Straw gap 20 µm
Straw film tube Mylar (aluminised)
Straw wall thickness 27 µm
Sense wire W/Rh
Wire diameter 20 µm
Wire tension 50 g
Straw weight 2.5 g
Number of axial straw layers 12- 19
Number of stereo straw layers 8
Stereo angle 2.9 deg
Gas mixture Ar/CO2(10%)
Gas pressure 2 bar (absolute)
Spatial resolution (r/phi) 150 µm
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STT inner radius 16 cm
STT outer radius 42 cm
STT total length 171 cm
STT material budget (radial) 1.23 % (X/X0)
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Topic revision: r2 - 04 Nov 2013, PeterWintz
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