Drift Time Measurement in the ATLAS Liquid Argon Electromagnetic Calorimeter using Cosmic Muons

Editors : C. Collard, C. Gabaldon & D. Fournier

Published in EPJC

Status : accepted by EPJC

arXiv:1002.4189

Figures

• Figure 1: Accordion structure of the barrel. The top figure is a view of a small sector of the barrel calorimeter in a plane transverse to the LHC beams. Honeycomb spacers, in the liquid argon gap, position the electrodes between the lead absorber plates.
  

Fig1 - Accordion Structure

• Figure 2: Typical single ionization pulse in a cell of layer 2 of the barrel (left) and endcap (right) of the calorimeter. The large red dots show the data samples, the small blue dots the prediction and the grey triangles the relative difference (data (S) - prediction (g))/S_max, on the scale shown on the right side of the plot (normalized to the data).
  

Fig2 Left - Ionization pulse in EMB

Fig2 Right - Ionization pulse in EMEC

• Figure 3: Nominal HV (black dots) and nominal gap width w_gap (blue triangles) versus eta in the 2nd layer of the EM calorimeter.
  

Fig3 - HV and gap width vs Eta

• Figure 4: Schematic view of a LAr gap. The nominal position of the readout electrode (dashed line) is exactly equidistant from the lead absorbers. Any shift with respect to the nominal position (solid line) causes an increase of the gap width on one side of the electrode, and a decrease on the other side.
  

Fig4 - LAr gap

• Figure 5: Current as a function of time for a perfect centering of the electrode (delta_gap=0 \mu m), a shift of delta_gap=100 \mu m and delta_gap=200 \mu m.
  

Fig5 - Current vs time

• Figure 6: Monte Carlo simulation for (left) T_drift and (right) T_bend versus eta for the three endcap layers: layer 1 (red triangles), layer 2 (black dots) and layer 3 (blue squares).
  

Fig6 Left - T_drift vs eta

Fig6 Right - T_bend vs eta

• Figure 7: (left) Q^2_0 versus S_max^gain and (right) Q^2 versus S_max in layer 2 of the barrel. The black points correspond to the mean value.
  

Fig7 Left - Q^2 vs S_max

Fig7 Right - Q^2_0 vs S+max^gain

• Figure 8: Absolute value of the shift parameter as a function of the drift time in the barrel (left) and in the endcap (right), for layer 2.
  

Fig8 Left - Shift vs T_drift in EMB

Fig8 Right - Shift vs T_drift in EMEC

• Figure 9: Distribution of the absolute value of the shift parameter in layer 2 of the barrel (left) and endcap (right).
  

Fig9 Left - Shift in EMB

Fig9 Right - Shift in EMEC

• Figure 10: Drift time as a function of eta in layer 2 of the barrel: using the RTM method (open dots), the FPM method (red triangles) and the prediction described in the text (purple line).
  

Fig10 - Drift time vs eta in barrel layer 2

• Figure 11: Drift time as a function of phi in layer 2 of the barrel: using the RTM method (open dots), the FPM method (red triangles) and the prediction described in the text (purple line)
  

Fig11 - Drift time vs phi in barrel layer 2

• Figure 12: 2D map of T_drift in (eta,phi) for layer 3. The empty bins correspond to sectors with non nominal HV.
  

Fig12 - 2D map for Drift time in eta,phi in barrel layer 3

• Figure 13: Drift time as a function of eta in layer 1 of the barrel: using the RTM method (open dots) and the FPM method (red triangles).
  

Fig13 - Drift time vs eta in barrel layer 1

• Figure 14: Drift time as a function of eta in the presampler barrel using the FPM method (red triangles). The full purple line represents the prediction normalized to the region 0.8<|eta|<1.2, using Equation 15 and the gap values given in Table 5. The empty bins correspond to sectors with non nominal HV.
  

Fig14 - Drift time vs eta in barrel layer 0

• Figure 15: Drift time uniformity between groups of 4x4 cells (Delta eta x Delta phi = 0.1x0.1) for barrel layer 2.
  

Fig15 - Drift time uniformity in barrel layer 2

• Figure 16: (eta,phi) map in which |delta_gap| is plotted per bin of 0.1x0.1
  

Fig16 - 2D map for Shift in eta,phi in barrel layer 2

• Figure 17: Drift time versus pseudorapidity for layer 1 (left), layer 2 (middle), and layer 3 (right) cells of the endcap. Black points are the data and red triangles Monte Carlo predictions for photons. The vertical dashed lines show the boundaries between different high voltage regions.
  

Fig17 Left - Drift time vs eta in layer 1 of endcap

Fig17 Middle - Drift time vs eta in layer 2 of endcap

Fig17 Right - Drift time vs eta in layer 3 of endcap

• Figure 18: Drift time versus pseudorapidity for the three layers of the endcap: layer 1 (red triangles), layer 2 (black dots), layer 3 (blue squares). The vertical dashed lines show the boundaries between different high voltage regions.
  

Fig18 - Drift time vs eta in layer 1,2,3 of endcap

• Figure 19: Drift time normalized to the average value versus phi for layer 2 of the eta>0 (left) and eta<0 (right) endcap wheels. The black dots are the average per phi bin and the vertical dashed lines show the boundaries between different modules.
  

Fig19 Left - Drift time vs Phi in layer 2 of endcapA

Fig19 Right - Drift time vs Phi in layer 2 of endcapC

• Figure 20: Drift time uniformity between groups of 4x4 cells (Delta eta x Delta phi = 0.1x0.1) for endcap layer 2. The normalization is obtained as a fit to the data using a first order polynomial in each HV region to cancel out the influence of the gap variation with eta.
  

Fig20 - Drift time uniformity in endcap layer 2

• Figure 21: Electrode shift as function of phi for layer 2 of the endcap. The black dots are the average per phi bin and the vertical dashed lines show the boundaries between different modules.
  

Fig21 - Shift vs phi in endcap layer 2

• Figure 22: (left) Drift time and (right) Drift velocity (at E = 1 kV/mm) versus eta in layer 2. The black dots are the average per eta bin.
  

Fig22 Left - Drift time vs eta in layer 2

Fig22 Right - Drift velocity vs eta in layer 2

• Figure 23: Drift velocity distribution for the barrel (left) and endcap (right).
  

Fig23 Left - Drift velocity for barrel

Fig23 Right - Drift velocity for endcap

• Figure 24: Relative difference between the design gap values and the values extracted from T_drift measurements.
  

Fig24 - Difference of gap values vs eta

• Figure 25: Drift velocity versus eta in the layer 2 at the operating point extracted from T_drift measurements.
  

Fig24 - Extracted Drift velocity versus eta in the layer 2 at the operating point

-- CarolineCollard - 15-Jul-2010

Last reviewed by: Never reviewed