Fermilab Summer Students - 2008

Research: Current silicon detector testing techniques require that the detectors have an installed readout system. A new technique was set up to test the properties of silicon detectors that do not require a readout system. This would allow specific areas of the detectors to be tested which would not be possible with current techniques. For testing of the silicon detector, a laser scanning station with a 1060 nm diode laser was assembled at the Silicon Detector Facility at Fermilab. This method uses the fact that the response of a silicon detector to a collimated laser beam pulse has the same effect as a minimum ionizing particle. The beam has a very small spot size, so it is possible to accurately position the beam to measure individual charge deposits on the aluminum strips that are connected to p-type silicon strips. The strips are probed by a low capacitance microprobe as opposed to the normal method of using a readout system. Tests were carried out on a 300-µm-thick silicon strip detector where we were able to calculate the capacitance of strips, the charge deposited per laser pulse on and around an aluminum strip, the doping concentration throughout the bulk of the detector and how electric field in the detector affects charge collection on the strips. The properties measured using this technique matched those which had already been collected by a beam test. This demonstrated that the new technique gave consistent results. This technique has a compact setup, allows great control of the amount and location of the deposited charge and can be used on detectors that have not been set up with a readout system.