diamond pixel detector

Diamond Pixel Detector:

A bias voltage of +200 V was applied, which resulted in a current of app. 4 nA. We operated the chip at 2.5 MHz. The voltage settings for the DAC are the same as for the silicon detector.

1. Backplane Pulse, 1 Pixel Read out

A backplane pulse of 1.8 V triggers the readout of a single column (figure 1). This pulse height corresponds to 14600 electrons, which is well above the readout threshold of 4140 electrons (V_C = -2.89 V).

Decreasing the backplane voltage from 1.8 V (14600 electrons, first figure) to 1.2 V (9740 electrons, second figure) and to 890 mV (7220 electrons, third figure) decreases the signal size of the pixel indicated by the arrow. Because the size of the two other pixel does not vary and is independent of the charge injected into the backplane we conclude they are not working.

2. Backplane Pulse - 2 Columns Read out

With a backplane pulse voltage of 2.55V (20700 electrons) another column is read out. The right one is the column from the previous figure (section 1.). On the left one you can see three additional pixels marked by arrows. In the following sequence you find one of them disappearing if the voltage decreases from 2.55 V to 2.3 V (18660 electrons) and to 2.0 V (16200 electrons).

3. Another Pixel

An additional pixel (indicated by the arrow) can be seen growing when the voltage is increased to 3.7 V (30000 electrons).

4. Many Columns

V_backplane = 4.6 V (37300 electrons)

Now many columns are read out, but no additional pixel can be definitly identified. The columns described in the previous section are marked as "1" and "2". We attribute the response of the other columns to crosstalk.

Since the signal size of only 3 pixels varies with differnt backplane pulse heights we conclude that only these are working properly. But only the most sensitive one responds to a backplane pulse, which size is in the range of signal generated by a mip in CVD diamond.

Aug 2 1999, Thomas Bergauer, Rudolf Wedenig