Public SCT Plots for Collision Data

This plot shows the intrinsic module efficiency for tracks measured in the SCT Barrel. In these plots we show the number of hits per possible hit where dead modules and chips are taken into account. The efficiency is shown for two different types of tracks; SCT stand alone and combined tracks. We demand a minimum of 20 TRT hits and 6 SCT hits in the silicon detectors (not including the hit under test for efficiency). This plot was approved on Wednesday 16th December 2009 at an open ATLAS meeting and uploaded on Friday 18th December 2009. The alignment used in this plot was derived from collision data.

This plot shows the intrinsic module efficiency for tracks measured in the SCT EndCap-A. In these plots we show the number of hits per possible hit where dead modules and chips are taken into account. The efficiency is shown for two different types of tracks; SCT stand alone and combined tracks. We demand a minimum of 20 TRT hits and 6 SCT hits in the silicon detectors (not including the hit under test for efficiency). This plot was approved on Wednesday 16th December 2009 at an open ATLAS meeting and uploaded on Friday 18th December 2009. The plot includes a preliminary alignment derived from beam data.

SCT reads out three 25ns time bins around Level-1 Accept signal. During commissioning, we run in a mode where a hit is recorded in a strip if the charge deposited is greater than the 1fC threshold in any of these time bins.We want the whole detector to be “timed in” with the trigger, so that the modules receive the Level-1 accept signal in the same bunch crossing as the particles from a collision pass through the modules. This involves applying delays to the trigger signal to compensate for the length of the optical fibres that transmit the trigger signal, and for the time-of-flight of particles from the interaction point to the module. We can fill a 3 bin histogram corresponding to whether a strip was over threshold in each of the three bunch crossings that are read out – the first bin corresponds to the bunch crossing before the Level-1 accept, the second bin is the same BC as the LVL1Accept and the third is the BC after. If we are correctly timed in, hits corresponding to tracks from a collision event should follow a “01X” pattern – i.e. nothing in the first bin, over threshold in the second bin, and no requirement on the third bin. For each event, fill one of these 3-bin timebin plots for each layer, using hits-on-track for that layer. Take the mean of this histogram, and fill this as the y-axis variable in a profile plot. Reset the histograms and repeat for all events. Therefore, the y error bars on each point represent the variances in the means of those timebin plots from event-to-event. One unit on the y-axis corresponds to 25ns, and to be correctly timed in, we hope that the mean should be between 1 and 2.

This plot shows a breakdown of the different types of error for the data taken in 2010 as seen on the previous plot. It shows that the total fraction of data with errors in the run period was less than 0.25%. The fraction of data with each kind of error can be found in corresponding bins.The report summarizing this can be found here.

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In this plot, the HV current measured in the HV power supply of the ATLAS SCT barrel modules are shown by points at four SCT barrel layers (B3 to B6) . The data were taken when the LHC beams were off. Assuming that all HV currents are due to generation current in the silicon bulk, they are converted to those at the temperature of 0oC using the temperature scaling formula with effective energy Egen =1.21 eV [1]. The predicted leakage currents by the Hamburg /Dortmund model are shown by four lines with colored bands indicating 1 sigma uncertainties, which is obtained by quadratically summing up all uncertainties of the model parameters as well as the temperature measurements. The prediction takes into account of self-annealing effects using the measured sensor temperatures shown at the top of plots. The prediction is based on the total 7 and 8-TeV collision luminosities delivered at Point-1, shown by the black solid line. Results of the FLUKA simulation [2] of minimum bias events at 7 TeV pp collisions (with 5% up at 8 TeV) are used to convert the collision luminosity to 1 MeV neutron-equivalent fluence at each layer. The error of the FLUKA simulation is not included in the estimate of 1 sigma uncertainty. Very good agreements between data and predictions are observed over 4 decades in leakage current as well as over 3 year, indicating (1) observed HV currents are mostly due to bulk generation current, (2) the leakage current models with self-annealing terms are well applicable and (3) the flux simulation is reasonable. In conclusion, the leakage current is one of good measures for the radiation levels at the SCT region. [1] A.Chilingarov, RD50 Technical Note 2013_JINST_8_P10003,
[2] https://twiki.cern.ch/twiki/bin/viewauth/Atlas/BenchmarkingAtTheLHC.

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This plot shows the leakage current distribution of the SCT modules of four barrel layers (B3 to B6) on Dec 5, 2012 when the LHC beam off. Out of 2112 barrel modules, 2060 modules (97.5%) satisfy the cuts of HV=150+5-2V with reasonable hybrid temperatures. The currents measured by the HV PS are converted to those at the temperature of 0oC using the temperature scaling formula. The leakage currents are plotted in 12 groups, each of which contains all the modules placed at the same z (beam direction) position. Values of modules in each group are plotted in series starting from 0 to 360 degree in phi direction. The distribution of currents is very flat along z (eta) except for B3 in which the central part (|z| < 30 cm) shows about 7% excess. This flat distribution is a good reflection of the flat eta distribution of secondary particles around the center of the minimum bias events.

Distribution of the temperatures of all the end-cap modules as of Dec. 5, 2012. Each module has one thermistor to measure the temperature of the hybrid circuit. Side A and C are shown with different colors.

Mean hybrid temperatures as a function of time (averaged every 5 days). In the endcap case, they are separately shown for sides A and C.