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New Multi-MHz KWS-2 Detector Improves Count Rate by a Factor of 25

6 November 2015

Providing world-class neutron scattering instruments at the best neutron sources for the scientific community is the mission of the Jülich Centre for Neutron Science (JCNS). This includes the ongoing search for component upgrades to drive up the performance of the instruments to their technical or even physical limits. A dramatic improvement in performance has now been achieved with the installation of a new detector at the small-angle neutron diffractometer KWS-2 operated by JCNS at the Heinz Maier-Leibnitz Zentrum (MLZ) in Garching.

The new detection system is characterized by a dead-time constant of 25ns and a count rate as high as 5MHz at 10% dead-time. Compared to the old detector, this means an improvement of factor 25:

SANS-2 New Detektor Image 1Fig. 1 – The dead time of the new KWS-2 detector extracted from the fit of the measured count rate (symbols) with the paralysable dead time model (line); an improvement of factor 25 was achieved compared to the old detector.
Copyright: Forschungszentrum Jülich

The much higher count rate shortens measurement times and thus increases the number of experiments which can be carried out in the same time period by the optimal use of the high flux of up to 2x108 neutrons cm-2 s-1 at the sample position. In addition, the detector’s excellent performance opens up new scientific opportunities to investigate the structures of small soft-matter and biological systems. These systems can typically deliver only a very weak scattering signal at high wave-vector transfers Q above the buffer or solvent level, a problem now resolved due to the leap in performance brought about by the new detector.Supplied by GE Reuter Stokes Inc., and installed in close collaboration with a team of JCNS and the Jülich institute Electronic Systems (ZEA-2) on-site, the system consists of an array of 3He tubes that cover an active detection area equivalent to 0.9 m2 (Fig. 2) along with innovative rapid read-out electronics:

SANS-2 New Detektor Image 2Fig. 2 – The new KWS-2 detector during the installation phase.
Copyright: Forschungszentrum Jülich

To improve the read-out characteristics and reduce noise, the detection electronics are mounted in a closed container at the rear of the detector.

For more information please contact the instrument scientists:

Dr. Aurel Radulescu: a.radulescu@fz-juelich.de
Dr. Noemi Kinga Szekely: n.szekely@fz-juelich.de
Dr. Marie-Sousai Appavou: m.s.appavou@fz-juelich.de