Fig. 1. Measured relationship between drift time (vertical axis) and distance to wire obtained from extrapolation of beam track reconstructed in a Si-microstrip telescope (horizontal axis), for a non-irradiated straw (top) and a at a counting rate of 18 MHz (bottom).

Fig. 2. Distribution of the resulting residual with respect to the beam track, for a non-irradiated straw (top) and at a counting rate of 18 MHz (bottom).

Fig. 3. Straw output signal typical of a point-like ionisation measured at the wire anode for the 70%Xe+20%CF₄+10%CO₂ gas mixture chosen for the ATLAS TRT tracker.

Fig. 4. Parameters of the processed straw signal at the input to the discriminator.

Fig. 5. Drift-time measurement accuracy as a function of the electronic threshold for different signal peaking times. The test-beam measurements are compared to simulations of the straw response.

Fig. 6. Drift-time measurement efficiency, as defined in the text, as a function of the electronic threshold for different signal peaking times.

Fig. 7. Drift-time measurement accuracy as a function of peaking time for different electronic thresholds. The test-beam measurements are compared to simulations of the straw response.

Fig. 8. Drift-time measurement efficiency, as defined in the text, as a function of peaking time for different electronic thresholds. The test-beam measurements are compared to simulations of the straw response.

Fig. 9. Drift-time measurement accuracy as a function of the straw counting rate for different overshoot areas of the analogue output signal as obtained from simulations front-end electronics with a 12.5 ns peaking time.

Fig. 10. Drift-time accuracy measured as a function of the time-bin size of the TDC.

Fig. 11. Drift-time measurement accuracy (left-hand scale) and efficiency (right-hand scale) as a function of the straw counting rate for the DC-coupled analogue circuit with baseline restoration.

Fig. 12. Block diagram of the ASDBLR chip.

Fig. 13. Measured ASDBLR input impedance versus frequency.

Fig. 14. SPICE simulation of the ASDBLR output of the preamplifier (solid) and shaping circuits (dashed). The horizontal scale is given in ns.

Fig. 15. SPICE simulation of the ASDBLR output after baseline restoration for input charges of 2 fC (with large undershoot) and 25 fC (rescaled). The horizontal scale is given in ns.

Fig. 16. Illustrative schematic of the baseline restorer (BLR).

Fig. 17. Output of shaper (top) and discriminator (bottom) of ASDBLR chip connected to a TRT straw. The plot on the left (right) corresponds to a signal below (above) the threshold for the TR discriminator. Each division corresponds to 20 ns for the horizontal scale and 25 mV (discriminator outputs) for the vertical scale. Vertical scale for shaper outputs is arbitrary.

Fig. 18. Low threshold current versus signal amplitude for 16 different channels of two ASDBLR chips.

Fig. 19. Same as Fig. 18 for the high-level threshold.

Fig. 20. Noise counting rate as a function of the low-level threshold for one channel of an ASDBLR chip connected to a straw through a 5 cm long cable with LEMO connectors.

Fig. 21. Drift-time measurement accuracy (bottom) and efficiency (top) as defined in Section 2, as a function of the straw counting rate measured for the DC-coupled electronics at a low-level threshold of 200 eV and for the ASDBLR chip at low-level thresholds of 170 and 266 eV.