The Lightweight Straw Tube Tracker for PANDA Detector at GSI

1. The Lightweight Straw Tube Tracker for PANDA Detector at GSI Andrey Sokolov*,1, James Ritman1, Peter Wintz1, Paola Gianotti2, Dario Orecchini2 1Institut für Kernphysik, Forschungszentrum Jülich 2Laboratori Nazionali di Frascati, Italy

2. PANDA detector Bernd Ketzer HK57.1 STT or TPC

3. Requirements to the Central Tracker • Almost full angular coverage; • High momentum resolution, δp/p~1%; • High spatial resolution, σrφ~150μm, σz~1-3mm; • Minimal detector material budget, X0~1%; • High rate capability, 107ev/s; • Resistance against aging effects, 1-2 C/cm/year;

4. Central Tracker Options Time-Projection Chamber(Christian Höppner, HK 38.2) Straw Tube Tracker

5. Straw Tube ~2 kV r Ar+CO2 Typical spatial resolution50-300 μm

6. Straw Tube

7. Elongation 1.5mm +50μm Pressure Stabilized Straw Tube Pabs=2 atm Overpressure gives the stability and rigidity to the straw tube, but it also change straw tube dimensions. That should be taken into account in the tracker design.

8. Pressure Stabilized Straw Tube Tracker COSY –TOF Straw Tube Tracker One double layer

9. Spatial Resolution Ar+20%CO2 Spatial resolution of the COSY-TOF straw tube tracker

10. Pressure Stabilized Straw Tube Tracker 1.5m Proposed PANDA pressure stabilized straw tube tracker

11. Aging Phenomena in Straw Tube • Gas gain in the straw tube can deteriorate and dark current (noise) can increase with a time due to aging effects, namely: • deposit of the conductive polymers on the wire surface; • formation of an insulation coating on the cathode (Malter effect); • anode wire swelling by the free radicals; • oxidation of the conductive layer on the cathode surface. • These aging phenomena are typically observed for the accumulated charge values > 1-3 C/cm, depending on the gas mixture.

12. Aging Phenomena in Straw Tube Anode wire surface after irradiation [ATLAS TRT, NIM A512(166)]

13. Longitudinal Hits Projection protons 1000 events of pp collisions (DPM generator)

14. Hit/Charge Density Along Straw Length

15. Conclusions and Outlook • New design for the PANDA Straw Tube Tracker has been proposed; • The total weight of the tracker will be only about 50 kg; • The spatial resolution is about 150μm using Ar+10%CO2 gas mixture; • The background simulation shows the very high radiation load; • The beam test is under preparation; • The test and simulation results of the PANDA straw tube tracker demonstrate the feasibility of the chosen detector concepts.

16. STT parameters • Total number of tubes - ~5000; • Radial dimensions – 16-42cm; • Length – 1.5m; • Tube diameters –10mm; • Tube wall material – Mylar, 30μm; • Anode wire – W/Re,20μm; • Spatial resolution – σrφ≈150μm, σz≈3-10mm; • Gas filling – Ar+10%CO2; • Gas absolute pressure – 2 bar; • Thickness - ~1% X0.

17. Longitudinal Coordinate Measurement • Skewed layers • 1-4 mm precision; • Charge sharing: • 10-20 mm precision; • Time of charge propagation: • 10-20 mm precision. One planar double-layer with the skewed straw tubes

18. HESR: High Energy Storage Ring Beam Momentum 1.5 - 15 GeV/c High Intensity Mode: Luminosity 2x1032 cm-2s-1 (2x107Hz) dp/p (st. cooling) ~10-4 High Resolution Mode: Luminosity 2x1031 cm-2s-1 dp/p (e- cooling) ~10-5

19. Straw Tube Straw Tube Tracker