Istituto Nazionale di Fisica Nucleare
Sezione di Trieste

Laboratory Measurements

To check the quality of a Silicon Drift Detector a series of laboratory measurements have to be done.

First an (I-V) measurement is done on the detector itself, in order to find possible local defects generating high current. It is very useful because permit us to preselect in a fast and simple way the "good" detectors from the leakage current point of view. This measurement is performed in a probe station using two needles.

Then the SDD is mounted on a detector card, and connected to it via ultrasonic wire bonding. This card is plugged into a motherboard (see the figure below), that provides all signals and bias voltages, as well as all connections and test points for the measurements.

With this set up we can perform both the static and the dynamic measurements. The static measurements consist in the test of both the leakage current at the anodes and the potential distribution on the divider. The former is done completing, on both sides, the detector card with a small PCB that connects together the anodes in groups of eight (see PCB1 on the figure above). The latter is performed checking the voltage drop every ten drift cathodes. As an example, the figure below shows the results of a ALICE-D1B prototype.

The dynamic measurement serves to check the performance of the MOS injectors. This can be done replacing PCB1 with a multi-layer PCB that can house the front-end electronics (PCB2). It is worthwhile noting that the wire bonding on the detector are not removed during this operation, as only the connection between PCBs are involved.
In this conditions, when we send a negative pulse to the MOS gate we can see the same pulse collected at one anode after the time of flight of the injected charge. The figure below shows, as an example, a scope picture of a signal coming from the injectors. The upper trace displays the trigger signal from the pulse generator. The lower trace shows the pulse collected at the anode after a tome of flight of the injected charge of 5.42us (the applied field was 500V/cm).

Data

Data base of the tested detectors (only for collaborators)
MOS measurements (only for collaborators)

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