The Lightweight Straw The Lightweight Straw Tube Tracker for PANDA Tube Tracker for PANDA

Detector at GSIDetector at GSIAndrey SokolovAndrey Sokolov*,1*,1, James Ritman, James Ritman11, Peter Wintz, Peter Wintz11, ,

Paola GianottiPaola Gianotti22, Dario Orecchini, Dario Orecchini22 11Institut für Kernphysik, Forschungszentrum JülichInstitut für Kernphysik, Forschungszentrum Jülich22Laboratori Nazionali di Frascati, ItalyLaboratori Nazionali di Frascati, Italy

PANDA detector

Target spectrometer:• MVD + STT/TPC + MDC• Time Of Flight• DIRC + RICH • Electro-Magnetic Calorimeter• Muon detection• Superconducting solenoid

Forward spectrometer:• Dipole magnet• MDC or STT• RICH• EMC• Hadron calorimeter• Muon detection

STT or TPC

Bernd Ketzer HK57.1Bernd Ketzer HK57.1

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;

Central Tracker Options

Time-Projection ChamberTime-Projection Chamber (Christian H(Christian Höppner, öppner, HK 38.2)HK 38.2)

Straw Tube TrackerStraw Tube Tracker

Straw Tube

r

Typical spatial resolutionTypical spatial resolution 50-300 50-300 μμmm

~2 kV

Ar+CO2

Straw Tube

Pressure Stabilized Straw Tube

Elongation 1.5mm

+50μm

Pabs=2 atm

Overpressure gives the stability and rigidity to the straw Overpressure gives the stability and rigidity to the straw tube, but it also change straw tube dimensions.tube, but it also change straw tube dimensions.

That should be taken into account in the tracker design.That should be taken into account in the tracker design.

COSY –TOFCOSY –TOF Straw Tube Tracker Straw Tube TrackerOne double layerOne double layer

Pressure Stabilized Straw Tube Tracker

Spatial Resolution

Spatial resolution of the COSY-TOF straw tube trackerSpatial resolution of the COSY-TOF straw tube tracker

Ar+20%CO2

Proposed PANDA pressure stabilized straw tube trackerProposed PANDA pressure stabilized straw tube tracker

Pressure Stabilized Straw Tube Tracker

1.5m

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.

Aging Phenomena in Straw Tube

Anode wire surface after irradiation Anode wire surface after irradiation [ATLAS TRT, NIM A512(166)][ATLAS TRT, NIM A512(166)]

Longitudinal Hits Projection

1000 events of pp collisions (DPM generator)1000 events of pp collisions (DPM generator)

protonsprotons

Hit/Charge Density Along Straw Length

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.

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.

STT parameters

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 tubesOne planar double-layer with the skewed straw tubes

HESR: High Energy Storage Ring

Beam Momentum1.5 - 15 GeV/c

High Intensity Mode:Luminosity 2x1032 cm-2s-1 (2x107Hz)p/p (st. cooling) ~10-4

High Resolution Mode:Luminosity 2x1031 cm-2s-1 p/p (e- cooling) ~10-5

Straw TubeStraw Tube Tracker