RECENT PIXEL WORK AT CPPM I. The DMILL Lepton array The DMILL Lepton pixel array contains 12 columns of 63 pixels with full read-out system. Since this matrix has been designed in a rad-hard technology, irradiation tests have been per- formed . Main results are depicted in Fig. 1. and Fig. 2. Fig. 1. shows the behaviour of the preamplifier after different doses and Fig. 2. depicts the behaviour of the analog part and the read-out part before and after irradiation up to 30 Mrad (Si)/ 6 1014 p(300Mev)/cm2, which is more than expected after 10 years of LHC operation. While the efficiency remains unchanged, the In-Time response (i. e. the minimum charge with correct bunch crossing tagging) is slightly increased. It demonstrates that correct pixel electronics behaviour after high level of irradiation is reachable. before irradiation 500 krad (Si)/ 1013 p(300Mev)/cm2 5 Mrad (Si)/ 1014 p(300Mev)/cm2 15 Mrad (Si)/ 3 1014 p(300Mev)/cm2 Fig. 1. Current impulse responses. Fig. 2. Response of the DMILL pixel array before and after 6 1014 proton(300Mev)/cm2 II. The Beer & Pastis pixel array The Beer & Pastis pixel array has been developed in collaboration with the University of Bonn. The technology used is the AMS BiCMOS 0.8u (see Fig. 4.). It includes 12 columns of 63 pixels and the pixel size of this chip has been kept constant (regardind the size of the Lep- ton pixel cell) in order to be compatible with existing p+/n detectors. The main new features are: - a complete new analog part which tolerates high detector leakage current. Special attention has been paid to reduce threshold mismatch (sigma of 90 electrons as shown in Fig. 3.) and to reduce the difference between the threshold and the In-Time response (i. e. time-walk) - a dynamic threshold tune in each pixel which allow performances depicted in Fig. 3. (sigma of 8 electrons). - an improvement of the read-out part which provides the analog information of the charge deposited in the pixel. This has been realized with the Time Over Threshold technics. Fig. 3. Measured threshold spread of the Beer & Pastis chip Fig. 4. Microphotograph of the Beer & Pastis chip III. Analog cell issued from the MBTS1 chip Fig. 5. Measured time walk of the AMS pixel cell MBTS1 stands for Marseille Bonn Test Structures 1. This chip has been developed at the beginning of 1997 in order to test main structures before realizing the pixel demonstrator (FE- A). It includes an enhanced analog part and some critical digital parts. In order to simulate the detector, an extra parasitic capacitance of 200 fF has been added at the input of each pixel cell. Fig. 5. depicts the delayed reponse of the complete cell (amplifier + discriminator) referenced to 35000 electrons input charge. The minimun charge to remain within a window of 25 ns is 2100 electrons. The threshold has been calculated to be 1650 elec- trons. These results give a time walk of 450 electrons. Fig. 6. Measured threshold of the AMS pixel cell versus leakage current Fig. 6. shows the full leakage current tolerance of the pixel cell. It has been measured by add- ing a current mirror directy at each pixel cell input.