by Panos Charitos. Published: 05 December 2012

Costanza obtained her PhD in electronic engineering from the University of Florence. As a PhD student she spent some time working with ALICE as part of the CERN – Doctorate program. During that time she had the chance to understand in depth the operation of the current pixel detector of the Inner Tracking System. Part of her work was to optimize and calibrate the trigger signal generated by the pixel detector and further develop the automatic procedures for calibration. When Costanza arrived at CERN the pixel detector team had already constructed a hardware board for triggering but it was not yet optimized and calibrated for real data-taking.

Costanza remembers that it was an exciting period since the first beams were running at the LHC and furthermore we were all excited to see how ITS worked during Pb-Pb collisions.

Costanza Cavicchioli, a CERN Fellow working in programming and designing the digital components of the upgraded ITS

Costanza spends most of her time working in the design of the electronics that will be used in the upgraded project of the ITS. Most of the time she is busy with the digital design of monolithic pixel detectors. She had previously learnt hardware description languages for programming and she used these languages to design the digital components of the detector. Fairly recently Costanza started working on the analogue world, developing not in code anymore but designing manually the schematic and the layout of the components.

Thanushan got his master degree in applied physics from the University of Turin where he continued to pursue his PhD at the department of experimental physics. During this period he was a member of the ASIC design team of the Turin branch of INFN (Italy’s National Institute of Nuclear Physics) where he had the opportunity to gain experience on Analog and Mixed Signal ASIC (Application Specific Integrated Circuit) design. He was actively involved in the design and test activities of the hybrid pixel front-end electronics for the Micro Vertex Detector (MVD) of the PANDA experiment at FAIR.

Thanushan Kugathasan: Following his long experience on Hybrid Pixel Detectors he moved to CERN as a fellow to work for the ITS Upgrade. For Thanushan, stepping into monolithic pixel detectors was a great challenge.

After becoming familiar with the language of particle physics and following his background on microelectronics he moved to CERN to work in the project of the ITS upgrade. From his previous experience, Thanushan was familiar with the design of hybrid pixel chips and hence stepping into monolithic pixel detectors was a great challenge.

Cesar, was associated to Universidad de Valencia working for the ATLAS TileCal. He was designing FPGA firmware and verification for the ATLAS TileCal upgrade phase I & II. He migrated to ITS upgrade through a Spanish Training Program working affiliated to the Polytechnic University of Valencia; he decided to join ALICE and the ITS upgrade on micro electronics team. He works closely with Thanushan and Costanza in the design of the new monolithic pixel detectors and he feels excited to be member of a team that develops this completely new technology. He points out that “this type of research is more specialized and one needs to be very dedicated and efficient to achieve”. Following his past experience, Cesar is now working on his PhD research in electronic engineering.

Cesar Marin working on the ITS upgrade on micro electronics team. Cesar works closely with Thanushan and Costanza in developing completely new technology as part of the ITS upgrade project

The ITS is used for tracking particles with a precision of few microns. When a particle hits a silicon detector it leaves a trail we see the charge that it produces in the silicon itself; these charges are then collected and elaborated to send a digital electronic signal outside the detector. The challenge of designing a monolithic pixel detector is that you have everything, namely the sensor and the electronics built in a single physical piece. This is quite different compared to the hybrid pixel detectors which are made of two different parts: one for collecting the charge and another which has all the electronics to amplify, digitize and store the signal.

Costanza, Thanushan and Cesar are working on CMOS Sensor Design for a new monolithic pixel detector, the first step in the chain of the data acquisition system. They have to think of new ways in which the physical information coming from the experiment can be transformed into electronic data that will then be processed outside the detectors. They work closely with the CERN microelectronics group. During the first year of hard work their group was able to design the first two prototypes using the Tower Jazz 0.18 um CMOS Imaging Sensor Technology. The first prototype is used for the technology validation, exploring whether this technology can be used in the ITS – also accounting for the radiation environment of the detector. The Total Ionizing Dose (TID) tolerance of the CMOS devices has been successfully tested and the test system for the study of the Single Event Upset (SEU) rate in memories is under preparation.

Finally, they also designed the first monolithic pixel prototype which has recently arrived and the first measurements are ongoing. Charge collection efficiency, cluster size and noise of different pixel layouts will be studied.

Following the endorsement of the ITS upgrade by the LHCC they are highly motivated to prove that the monolithic pixel technology is mature and can comply with the requirements of the upgraded ITS. By the end of next year they hope that they will come up with a fully designed chip. This of course if a very tight schedule but as they are all experienced and know how to work as a team they can succeed!