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3. The Hcal monitoring display

Before we could develop such monitoring display,it was necessary to implement in the program a complete model of the geometry of the detector and of the readout system. This model is also the basis for the event display, so it was decided to have in the same program, both the event and the monitoring display. A 3D display of Hcal and Mdet was implemented (see figure 1) . This representation is rather messy and almost unusable even if you deselect most of the detector(see figure 2). The modeling of the readout system introduces other difficulties. We used an exploded representation of the detector, to make it easier to grasp. Each one of the three detector parts:i.e. the barrel,endcap a and endcap b, is a sandwich filled with 22 layers of streamer tubes. Each layer is read by strips and pads . The strips are individually read, but the pad signals are summed for the 22 of them that form a "tower". The exploded representation of the event, will show for each of the three parts of the detectors, the 22 layers separately with the fired strips and pads(figure 3). Fired strips should always cross fired pads, so this display will allow a visual check of the apparatus at the layer level in the single event. Both the 3D representation and the exploded view are not suitable for the monitoring display, where we want to show the status of all sensors and the geometrical correlations between them. The 3D display is a clutter with only a few channels, imagine with all of them! The exploded view is too detailed and will require more than one screen. Therefore we developed a planar map of the calorimeter borrowing the idea from the representation of geographical entities, like towns, usually found in atlases[3] . The data is overlayed on the map of the country,with the information coded in some way at the town position. This allows the display of huge amounts of information making manifest in the same time the spatial correlations present in the data. The development of this map for Hcal was relatively straightforward. When a high energy particle crosses one of the 36 modules which compose the calorimeter, it leaves a track of fired towers and a track of fired strips. In fig. 4a the towers are drawn on the front and back surface of the module, while the fired strips are drawn on the walls. In fig. 4b a two dimensional representation of the module shows the wall and the back surface of the module. This is a map of the module,in the sense that we can draw each one of the channels in a different position and the spatial correlations are kept. In fact you can now code the Adc value for analog channels in color or in some other way.(fig 4b) This idea may be extended to the three parts of the calorimeter and to Mdet. The final result is what you see in fig.5 where you have the complete map of Hcal and Mdet. You can use this map to represent single events (see fig.5). At this level it is possible to check visually the geometrical correlation between the Mdet and Hcal signal. In the use as monitoring display the values shown are computed by integrating the signals coming from thousands of events(fig. 6). This is the main display used by the operator to check for detector problems. He will look for empty zones ,signals drawn outside the detector outline, unusual pattern in the tower signal distribution. Always firing channels will appear as flashing. In figure 7 ,what is coded in colour in each tower position, is the mean of the pedestal for the tower. In fact any kind of information concerning towers and strips may be shown using this map. The implementation was done on a Vaxstation 3100 using X-windows and the Motif toolkit. The program was written in C + Fortran and the Uil language was used to develop the user interface. The operator can click on any detector part and get more information about it. In the case of a bad channel, this information should be sufficient to repair it.

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