The looming nature of ‘the closing’ has injected an increased sense of urgency into all those still working on detector installation. Since TileCal has been installed in the pit for several years now, you would think we would be exempt from such urgency. But no. In the past year or so, TileCal has undergone a campaign to repair some less-than-optimal components in our electronics. The front-end electronics for the TileCal are organized in long ‘drawers’ which can be pulled out from the ends of the calorimeter. We are replacing things like the power connectors which have been causing some problems over time. In the past year, we had the time and detector access to make these repairs so we decided not to wait for the problems to worsen.
There are 256 electronics drawers in TileCal so upgrading every single one is more than a day’s work. The drawer itself is almost nine feet long. It has to be removed from the calorimeter, lowered down to the floor of the detector cavern. On the floor, three electronics tables are set up where technicians can make the modifications. Once done, the drawer is tested, raised back to the calorimeter, re-inserted and re-tested.
One of the most difficult parts of this procedure is just getting the drawer from the calorimeter to the technician’s tables. There is no space to make the modifications right at the calorimeter so moving the drawer is the only solution. Furthermore, the scaffolding surrounding the calorimeter is accessible by ladders so we have to invent some creative ways to get the electronics drawers up and down the scaffolding.
One technique is to lower and raise the drawers through the access areas in the scaffolding. As seen here. The blue boxes at the top of the picture is the part of the calorimeter, where the electronic drawers are inserted. In the center of the picture, part of one of the drawers is being raised between two access ladders. This is delicate work. You don’t want to go banging your newly repaired electronic drawer against the sides of the scaffolding. And these are all custom-built electronics. It is not like you can go get a replacement at Radio Shack. On my former experiment, SNO, the electronics racks had signs reading, ‘Careful! These electronics cost more than your house!’.
It is times like these where I really admire a technician’s patience. The pressure of ‘the closing’ is increasing, everyone knows that soon the scaffolding will come down, the collective heart rate has gone up several beats. But the technicians are never fazed and continue to raise the drawers with the same patience and precision as ever. They know better than anyone: you raise the drawer too fast, you will break it. We are in good hands with those guys.
Tags: ATLAS, commissioning, installation
