CERN Accelerating science

Young scientist from PH/ESE group wins IEEE Nuclear and Plasma Sciences Society 2013 Radiation Instrumentation Early Career Award

Rafael Ballabriga Sune, a young scientist working within the ESE group, has been presented with the IEEE Nuclear and Plasma Sciences Society 2013 Radiation Instrumentation Early Career Award "for the implementation of a new approach to spectroscopic X-ray imaging, with registration of photon energies, using semiconductor devices with in-pixel processing for each individual incident photon". The ceremony took place on the 28th of October at the plenary session of the Nuclear Science Symposium in Seoul.

Left to right: Medipix2 and 3 collaborations spokesperson, Michael Campbell, Rafael Ballabriga and Xavier Llopart of the Medipix design team (Image credit Paula Collins/CERN)

Rafael Ballabriga graduated from Ramon Lull La Salle University in Barcelona (Spain) in 2002 (BSc 2000, MSc 2002). In 2004, he joined CERN, in the framework of the CERN Doctoral Student Program. At CERN, he worked with the microelectronics group, in the Medipix team on the design of hybrid pixel detector readout ASICs. His primary task was to study solutions to eliminate the distortion in the measured energy spectrum caused by charge sharing effects and fluorescence photons in segmented semiconductor detectors. In the designed architecture, the pixels on the ASIC communicate on an event by event basis, in order to identify the pixel with the largest energy deposition and assign to it the reconstructed charge over a larger-than-the-pixel sensor area. This is a method to retain spectroscopic information at high spatial resolution thas was implemented in the Medipix3RX chip. Multiple thresholds combined with the innovative architecture for charge reconstruction enable accurate energy weighting X-ray imaging and K-edge imaging.

Ballabriga says: "This award recognizes the work of a very motivated and dynamic team and the ideas that were identified during the work done in the framework of the Medipix2 collaboration, well before I arrived to CERN. I am very honoured to have been trusted to explore those ideas and implement them on an ASIC."

In addition to co-designing the Medipix3RX ASIC, together with Xavier Llopart, and implementing the novel charge summing architecture, Rafael Ballabriga and his colleagues from the Medipix3 Collaboration worked together towards the realization of the full detector system. As for the future, Ballabriga notes: "In the context of my work on the Medipix3 project, I have been exposed to many different tasks: microelectronics design, hybrid pixel detector electrical testing and characterization with radiation sources and also integration of the ASICs into different readout systems. I believe this will be valuable know-how for future projects within the ESE group."


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