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Monica Dunford | USLHC | USA

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How Time Passes

Like many others in this field, I am often asked the question by friends, ‘What is it that you do exactly?’ This is my cue to launch into my standard spiel about discovering the origins of mass, etc. But usually I don’t get that far before being interrupted with, ‘No, no, no. You go to work… Time passes… You come home… Something happens in the middle there.’

At the moment, discovering the origins of mass and new physics is more like the light at the end of the tunnel than a daily reality. These discoveries are the things we all strive to make; the reason we endeavor to build a massive 6-story detector. But a detector that big means there are billions of little pieces that must be put together and tested to verify that they are functioning properly. The majority of my days are spent making sure that my little corner of ATLAS is doing just that: functioning properly. So that when the beam turns on, we’ll be ready to start answering the big questions.

Just like my fellow blogger, Pam, my corner of ATLAS involves a lot of cable. Actually all of ATLAS involves cables. Real estate on the detector itself is hard to come by because any type of read-out electronics, power supplies, or structural support, is dead material. As the goal is to measure very energetic particles flying out from the beam’s interaction in the detector’s center, if these particles pass through dead material, they cannot be measured accurately. Therefore anything that doesn’t absolutely HAVE to be on the detector isn’t. Hence the cable.

A short way off from the detector is a series of rooms, collectively called the ‘counting room’ which is the destination of the miles of cables flowing off the detector to the remainder of ATLAS’ power supplies and electronics. And I do mean miles. As seen in this picture, beneath the floors of the counting room is cable tray after tray. I have only had to crawl under the floor laying cable once and I emerged from the experience sore from the acrobatics required to move around the trays and looking like a human impersonation of a dust ball.
The counting room floor

LVL1 CablesThe cables that I am most intimately familiar with are those coming from the Tile Calorimeter to the Level-one trigger. (I will leave the description of TileCal and level-one trigger for another day.) The cables shown here carry the analog trigger signals from the calorimeter to the counting room. Don’t be deceived by the apparent innocence of these cables. It is a serious triceps workout to wrestle those cables into the connectors.

Before we can be ready for the beam, there are a series of tests that need to be done. First, we have to confirm that every cable and pin within that cable is going to the correct place in the counting room electronics. Second, we have to confirm that the electronics producing the trigger signals on the detector are functioning properly. Third, we have to calibrate both the electronics on the detector and in the counting room. The calibration is essential for us to be able to convert the signal we actually measure in the electronics (which is in milli-volts) to the quantity we actually care about (which is the particle’s energy as it passed through the detector).

While eventually one day we will be answering fundamental questions about the origin of mass, today I can only tell you which TileCal sectors are fully cabled and ready to go. On a day-to-day basis, getting those sectors tested and functioning is how time passes. And it passes quickly.

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