Design and First Tests of a Radiation-Hard Pixel Sensor for the European X-Ray Free-Electron Laser

The high intensity and high repetition rate of the European X-ray Free-Electron Laser, presently under construction in Hamburg, requires silicon sensors which can stand X-ray doses of up to 1 GGy for 3 years of operation at high bias voltage. Within the AGIPD Collaboration the X-ray-radiation damage in MOS Capacitors and Gate-Controlled Diodes fabricated by four vendors on high-ohmic n-type silicon with two crystal orientations and dif- ferent technological parameters, has been studied for doses between 1 kGy and 1 GGy. The extracted values of oxide-charge and surface-current densi- ties have been used in TCAD simulations, and the layout and technological parameters of the AGIPD pixel sensor optimized. It is found that the op- timized layout for high X-ray doses is significantly different from the one for non-irradiated sensors. First sensors and test structures have been de-livered in early 2013. Measurement results for X-ray doses of 0 to 10 MGy and their comparison to simulations are presented. They demonstrate that the optimization has been successful and that the sensors fulfill the required specifications

Ethnicity, communication and growth.

In this paper we consider the link often alleged between ethnic diversity and the growth rate of GDP per capita. We first assume that it is ethnic polarization rather than ethnic fragmentation that is harmful for growth so that the relationship may be nonlinear. Second, we hypothesize that the impact of ethnic diversity on growth may depend on communication costs. This leads us to estimate a traditional growth rate equation on cross sectional data in a switching regression framework. In "low communication costs countries", the relationship between growth and ethnic diversity is U-shaped. On the other hand, in "high communication costs countries", growth is a decreasing function of ethnic diversity and the severity of the latter's deleterious impact is an increasing function of communication costs, proxied here by the illiteracy rate. The regime that a country belongs to is a function of two proxies for communication costs: the illiteracy rate and population density. The impact of ethnic diversity on growth seems not to operate through macroeconomic policy choices. Rather it is a direct transmission mechanism, in which ethnic diversity affects private and public resource allocation, that appears to dominate.