MDT second coordinate readout: status and perspectives Yuri Davydov JINR, Dubna XXXI PANDA Collaboration meeting GSI, December 2009

Two types of MDTs “Closed geometry” Al profile: 0.6 mm thick Cover: 0.15mm thick S.S. Wire: 50 μm W(Au) Envelop: Noryl “Open geometry” Al profile: 0.6 mm thick Wire: 50 μm W(Au) Envelop: Noryl Strips: 1 cm wide, 10cm long The same tube was used for the test measurements for closed geometry and open geometry (S.S. cover was removed). Tube length is about 60 cm. Gas mixture: 70%Ar+30%CO2

Anode and strip induced signals Signal induced on the single strip is about 10% of that on the wire Two preamps AMPL-8.3 were used to detect a strip signal Trace 1: Anode signal, K≈60 mV/μA Trace 2: Strip signal, inverted, K≈480 mV/μA

Counting rate and efficiency Cosmics, threshold 2 μA Difference between closed and open geometry is ~80 V

Counting rates of an open geometry MDT with a 60Co source Thresholds: 1.0 μA, 1.5 μA, 2.0 μA Counting rate with 60Co at threshold 2.0 μA is close to that for cosmics at the same threshold: similar initial ionizations in the chamber gas. Could be used for tests during MDT construction, assembly and, possibly, operation

Amplitude and time spectra Open geometry U=2300 V The time spectra are similar for closed geometry at 2200 V and open geometry at 2300 V

Spectra from 55Fe x-rays Closed geometry Open geometry 2200 V 2300 V Full photo absorption peaks correspond to energy 5.9 keV and allow to estimate a gas gain in the MDTs

Gas gain One needs to apply about 100 V more to the open geometry MDT in order to get the same gas gain

The block diagram of the test setup for spatial accuracy study Sc 1, Sc 2: 100•20•100 мм3 4 strips 1 cm wide 10 cm long on each MDT AMPL-8.3 preamplifier LeCroy 2249A ADC gate 1000 ns

Typical individual strip spectra from MDT Scintillator counters selected particles mostly crossing two central strips

Anode and induced signals on four MDTs Wires Strips (sum of 4 strips) MDT 1 MDT 2 MDT 1 MDT 2 MDT 3 MDT 4 MDT 3 MDT 4

Wire-strip signals correlation Sum of 4 strips Strip signal, μA QS /QA = 21.6±1.1 % Anode signal, μA

Track reconstruction with strip signals Signal is defined on each strip For each MDT a charge distribution is fitted by Gaussian in order to calculate center of gravity Track is reconstructed by linear fit using 4 points Residuals are calculated

MDT spatial accuracy of the strip readout 1 cm wide, 10 cm long strips 4 MDT layers near vertical tracks Achieved a spatial accuracy: σ~0.4 мм Much better than PANDA requirements – there is a real room for optimization of a number of channels!

The test results are published as JINR preprints and submitted to a referred journal: V.M. Abazov, G.D. Alexeev, Yu.I. Davydov, V.L. Malyshev, A.A. Piskun, V.V. Tokmenin 1. A performance comparison of mini-drift tubes with a different design JINR preprint P13-2009-164 (in Russian) Submitted to: “Pribory i Technika Experimenta” (in Russian) / “Instruments and Scientific Techniques” (English version) 2. The spatial accuracy of mini-drift tubes by detecting the induced signals JINR preprint P13-2009-173 (in Russian) Submitted to: “Pribory i Technika Experimenta” (in Russian) / “Instruments and Scientific Techniques” (English version)

Conclusion Plans for the future MDT with an open cathode geometry reliably allows to detect signals induced on the outer strips. Double Ampl-8.3 preams seems to operate stable at least with short strips. The spatial resolution σ≈ 0.4 mm achieved with 1 cm wide and 10 cm long strips Plans for the future Test of a strip readout with long (up to 4 m) strips Test of a strip readout with strips of a different width Optimization of the strip widths for all MDTs over the whole PANDA spectrometer (i.e. minimization of a number of channels)