Timepix3 makes its way into synchrotron research
Nicola Tartoni (Diamond Light Source), 27/05/2016
Figure 1: Shows the histogram of the time of arrivals of photons. The acquisition was synchronised with the machine clock and it shows that Timepix3 measures correctly the beam structure and that the isolated flash is completely separated from the train of flashes. (Image: Hazem Yousef and Giulio Crevatin, Diamond Light Source)
The detector group at Diamond Light Source, the UK’s synchrotron science facility, is developing a new photon counting detector for time resolved experiments based on Timepix3. The Timepix3 builds upon previous designs with a very high spatial resolution and it is the latest read-out application-specific integrated circuit (ASIC) for pixelated detectors released by the Medipix3 collaboration led by CERN.
The Timepix3 ASIC is designed to resolve individual interaction of photons and particles with the sensor material by placing a time stamp to the time of arrival of the event. The nominal accuracy of the time stamp of Timepix3 is 1.5625 ns. Unlike the more conventional technology of photon counting detectors, such as Medipix3, Timepix3 works in the so-called “data driven mode”: every time an event is detected the information related to the time of arrival and location of the event is sent on the data lines. This enables a much more efficient data transfer when data is sparse.
The detector group at Diamond has been a member of the Medipix3 collaboration since 2007. Scientists there realised that the Timepix3 could be a very good candidate for building position-sensitive detectors for time-resolved experiments from time scales between less than milliseconds down to tens of nanosecond and possibly below.
Beamline scientists at Diamond voiced a strong need for more efficient detectors for time-resolved experiments in a large number of techniques that include small-molecule crystallography, powder diffraction, small angle scattering, absorption and emission X-ray spectroscopy. The detector group therefore proposed the development of a large-area position-sensitive detector for time-resolved experiments based on Timepix3. The detector that is going to be developed will tile 160 Timepix3 read-out ASICs that will be flip-chip bump-bonded to 10 monolithic silicon sensors. This will give a total of 10 million pixels and a sensitive area of 320 cm2.
In order to determine the characteristics of Timepix3, and the best way to operate it, the detector group at Diamond is carrying out a number of beam tests with a single chip system. Some of the results already published show the outstanding timing capability of Timepix3. The X-ray beam emitted by Diamond consists of trains of flashes 50 picoseconds long and spaced 2 nanometres apart. During the hybrid mode of operation the train of flashes lasts 1.372 microseconds (686 flashes) followed by a 0.5-microsecond gap. In the middle of the gap an isolated flash is placed. This results in an excellent diagnostic tool of the timing capabilities of detectors when the acquisition is synchronised with the machine clock that is locked to the frequency of flashes. Figure 1 shows the beam structure measured by Timepix3. The isolated flash is completely separated by the train of flashes. The best results achieved so far are 19 nanoseconds FWHM of the isolated peak. Pump and probe experiments can be greatly enhanced by the capability to completely separate the isolated flash.
The time-resolved detector development project was approved last March by the Diamond management team. The delivery of a first single module prototype is planned in 2017.
For further information on Diamond’s detector activities, please visit http://www.diamond.ac.uk/Science/Research/Detector.html