The aim of the first test was to show that a charge injected signal into the SDD can be read out through the SDD hybrid frontend electronics. A fully tested and functional SDD (STAR 2.7 from SINTEF) was mounted into an E896 test board. A fully tested hybrid prototype was glued and aligned on the board and then bonded to the detector. Details and photographs of this setup can be found under SVT System Test Layout on the SVT System Test homepage.
We used the second injection line located at a distance of 1 cm from the anodes. The line consists of so-called 'dot' injectors, which are distributed evenly across the detector with a 2.25 mm dot spacing. The dots allow to not only measure the drift time and the amplitude, but also the width of the drift cloud. We injected a 5 V pulse which corresponds to about 10 MIP. 10 MIP translates to an amplitude of about 800 mV in the main cluster pixel.
The following measurement was obtained by using a LABVIEW setup. For the upcoming tests we will replace the LABVIEW system with the UT based readout electronics/DAQ system.
The three dimensional 'lego'-plot depicts the amplitude on the y-axis (scale = 0-0.8 V), the anode number on the z-axis (anode = 0-80), and the timebucket number on the x-axis (timebucket = 0-127). For reasons of simplicity only the last 80 anodes (1/3 of the detector) are shown: Charge injection into E896-1
The amplitude and drift time are remarkably stable. The width of the cloud is also narrower than expected based on previous bench tests. The cloud shows a sigma of about 70 ns.
The noise level in the pedestal channels averages 4.5 mV which corresponds to about 450 rms electrons, well within the SVT requirements.
The next tests will include measurements with smaller injection pulses to determine the response to minimum ionizing particles.