SAUNA QB - Array: The realization of a new concept in radioxenon detection.

We introduce a new concept in radioxenon detection - the radioxenon Array, defined as a system where air sampling and activity measurement is performed at multiple locations, using measurement units that are less sensitive, but on the other hand less costly, and easier to install and operate, compared to current state-of-the-art radioxenon systems. The inter-unit distance in the Array is typically hundreds of kilometres. Using synthetic nuclear explosions together with a parametrized measurement system model, we argue that, when such measurement units are combined into an Array, the aggregated verification performance (detection, location, and characterization) can be high. The concept has been realized by developing a measurement unit named SAUNA QB, and the world's first radioxenon Array is now operating in Sweden. The operational principles and performance of the SAUNA QB and the Array is described, and examples of first measured data are presented, indicating a measurement performance according to expectations.

Neutron spectrometer for ITER using silicon detectors.

High resolution neutron spectrometers provide information about plasma parameters at existing fusion experiments. Such a system may also be employed at ITER. Proton recoil telescopes have classically been used to detect neutrons with good energy resolution but poor efficiency. Using annular silicon detectors, it is possible to greatly increase the solid angle coverage and hence improve efficiency. Based on a simulation (MCNPX) study, the scaling of energy resolution, efficiency, and time to determine an ion temperature to 10% accuracy on foil thickness and detector location is shown. The latter quantity is used to determine the optimum foil thickness and detector geometry for specific plasma temperatures. For a 20 keV deuterium-tritium (DT) plasma, 5.3% resolution with efficiency of 2.9x10(-4) n cm(2) is attainable using the available detectors. This gives a temperature measurement with 10% accuracy in 1.1 ms for a neutron flux of 2x10(9) n cm(-2). Multiple detectors can be used to further increase the efficiency if needed. A system of this kind could be tested in a future DT campaign at, for example, JET.