Department of Physics

Development of ultrasensitive radiation detectors

Superconducting Transition edge sensors as X-ray calorimeters

Detectors based on superconducting films with a transition temperature ~100 mK are currently the most sensitive X-ray detectors available. We are developing novel transition-edge sensor (TES) types for ultimate energy resolution, and are studying how the noise and responsivity of the devices can be improved both experimentally [Kinnunen2012, Palosaari2012] and theoretically [Maasilta2012].

Recently, we also started collaborating with the Technical Research Center of Finland, VTT Micronova, with whom a full wafer process for 256 pixel TES array was developed. The detector arrays are designed for materials science applications, for example for ultrasensitive elemental analysis. Studies will also help the future space agency satellite missions, for which ultrasensitive imaging X-ray spectrometers are being developed. The space mission detector work is performed in collaboration with the Space Research Organization Netherlands (SRON).

256 pixel X-ray TES array

Applications of TES spectrometers in chemistry, materials analysis and art history

In addition to pure detector research, we are heavily involved in developing whole X-ray spectrometer setups and pushing forward novel applications for these unique instruments. Recently, in collaboration with Lund University and NIST Boulder (funded by ERC), we demonstrated that using a TES spectrometer, chemical information can be obtained in X-ray absorption spectroscopy (EXAFS) in a lab-based setup, without the help of synchrotrons [Uhlig2013].This opens up the even more exciting possibility to get time-resolved chemical information, as the X-ray source used in the study was pulsed by a fs-laser.

Locally at the Physics Department in Jyväskylä, we have developed a unique spectroscopic tool for materials analysis, which is capable of resolving X-ray fluorescence lines excited with a proton beam (PIXE) orders of magnitude better than commercial instruments [Palosaari2014]. The new instrument is operated in collaboration with the Accelerator laboratory, and several companies have been involved in the TEKES funded project (Aivon Oy, Oxford Instruments Nanotechnology Tools Ltd, and Star Cryoelectronics LLC). The tool will also be used in the future to study art and cultural artefacts in an another TEKES project RECENART, in collaboration with the Art History and Chemistry Departments at Jyväskylä University.

ADR cryostat and the read-out of TES X-ray spectrometer