(r9) GeneralDescription < STT

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---++ General Description

-- Main.PeterWintz - 04 Nov 2013

<img align="right" alt="STT x-y view" height="251" src="%ATTACHURLPATH%/STT_xyview.jpg" width="240" />
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.

<img align="right" alt="STT 3-D view" height="217" src="%ATTACHURLPATH%/STT_3Dview.jpg" width="245" />

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

| *Specifications* ||
| 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/Rh |
| 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) | &lt; 10 % |
| Maximum rate (innermost layer) | &lt; 1 MHz/straw, &lt; 7-14 kHz/cm |
| Mean charge load | 0.2 C / cm |
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Topic attachments
I	Attachment	Action	Size	Date	Who	Comment
jpg	STT_3Dview.jpg	manage	30.2 K	04 Nov 2013 - 14:16	PeterWintz	STT 3-D view
jpg	STT_xyview.jpg	manage	52.9 K	04 Nov 2013 - 14:14	PeterWintz	STT x-y view

Topic revision: r9 - 27 Mar 2014, PeterWintz

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