General Description

-- PeterWintz - 04 Nov 2013

STT x-y view 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 track association to events in the PANDA specific environment of about 150 tracks from 40 individual events within 2 µs.

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 230 kg and 3.2 tons (sum for 4636 tubes). The straws are arranged in two semi-barrels around the beam pipe with a few cm gap to leave space for the vertical target pipe.

STT 3-D view

STT Dimensions
Inner radius 15 cm
Outer radius 42 cm
Total length 171 cm
Material budget (radial) 1.23 % (X/X0)

Number of straws 4636
Straw length 1400 mm
Straw diameter (inner) 10 mm
Straw pitch 10.14 mm
Straw film tube Mylar (aluminised)
Straw wall thickness 27 µm
Sense wire W/Re
Wire diameter 20 µm
Number of axial layers 15-19
Number of stereo layers 8
Stereo angle +2.9, -2.9 deg
Gas mixture Ar/CO2(10%)
Gas pressure 2 bar (absolute)
Maximum drift time (2T-field) ~ 200 ns
Spatial resolution (sigma) 150 µm (xy), 2-3 mm (z)
Energy resolution (dE/dx) < 10 %
Maximum rate (innermost layer) < 1 MHz/straw, < 7-14 kHz/cm
Mean charge load 0.2 C / cm
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Topic attachments
I Attachment ActionSorted ascending Size Date Who Comment
STT_3Dview.jpgjpg STT_3Dview.jpg manage 30.2 K 04 Nov 2013 - 14:16 PeterWintz STT 3-D view
STT_xyview.jpgjpg STT_xyview.jpg manage 52.9 K 04 Nov 2013 - 14:14 PeterWintz STT x-y view
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