A miniature four-channel ionization chamber that was developed at NSLS
Detectors sit at the very end of the intricate systems that constitute light sources like NSLS and NSLS-II. Because detectors are where the science gets done, detector research and development can enable new science.
For the user community, NSLS-II will offer a significantly higher degree of coherence in its beams than most other synchrotrons, so imaging techniques that take advantage of that superiority are at the forefront of detector R&D.
The CHX beamline, one of six project beamlines being built for NSLS-II, uses photon correlation spectroscopy. The goal is to detect the arrival time of photons with the highest possible resolution over the largest possible area. Current detectors allow a time resolution in the millisecond range and require the full detector area to be read out with millisecond frame rate. The detector being developed will provide a time resolution of 10 microseconds in the first generation and around 10 nanoseconds in the next. DOE is funding this effort, which is a collaboration involving Brookhaven, Fermilab, and AGH University of Science and Technology in Poland.
Another project beamline at NSLS-II, XPD, will enable diffraction using x-rays in the 50-100 keV range. At these energies, silicon becomes very transparent, so any silicon-based detector will be extremely inefficient. Work has begun on a technology based on germanium, which is much more highly absorbing in this energy range. Although this is extremely challenging, success will enable a range of new detectors and a new generation of experiments making use of high-energy x-rays.
Detector R&D can also help NSLS users to do better experiments. One user from the National Institute of Standards and Technology presented a challenge: Measure samples simultaneously using a technique known as EXAFS. The solution: A miniature four-channel ionization chamber was developed, providing an excellent way to do comparative experiments. A bonus: These devices have also proved useful at the Advanced Photon Source at Argonne National Laboratory.