posted by: dberry
I just finished a bunch of shifts on the ECAL test beam. This summer, the ECAL group ran a test beam at the H4 Prevessin site. The test beam consists of a stream of high energy electrons. Our beam of electrons was generated by the SPS (Super Proton Synchrotron). The proton beam is smashed into a high Z element (like tungsten) to produce pions. The neutral pions are separated off and they decay to photons. The photons are then smashed into a lighter target (such as copper) and it produces high energy electrons.
The high energy electrons are then sent to a 5×5 crystal tower. We then move the crystal tower such that the beam lands on a specific crystal. The first thing we did in the experiment was characterized a normal 5×5 crystal tower. Then we changed out two of the crystals. One crystal was replaced with a radiation damaged crystal, and the other one was made out of a material which is more resistant to radiation damage. We then remeasured the crystal towers response. The data hasn’t been analyzed yet, so I can’t post any results. But below is a picture of the radiation damaged crystal.