The Casimir effect is a well-known macroscopic consequence of quantum vacuum fluctuations, but whereas the static effect (Casimir force) has long been observed experimentally, the dynamic Casimir effect is up to now undetected. From an experimental viewpoint a possible detection would imply the vibration of a mirror at gigahertz frequencies. Mechanical motions at such frequencies turn out to be technically unfeasible. Here we present a different experimental scheme where mechanical motions are avoided, and the results of laboratory tests showing that the scheme is practically feasible. We think that at present this approach gives the only possibility of detecting this phenomenon. PACS numbers: 12.20.Fv, 42.50.Dv, For any quantum field, the vacuum is defined as its ground state. Differently than in the classic case, this ground state, due to the uncertainty principle, is not empty, but filled with field fluctuations around a zero mean value. Moreover this vacuum state depends on the field boundary conditions : if they change, there will be a correspondingly different vacuum (whose fluctuations will have a different wavelength spectrum). Thus a quantum vacuum state may be equivalent to real particles of a new vacuum after a change in boundary conditions.If we consider the electromagnetic field, the peculiar nature of the quantum vacuum has experimentally observable consequences in the realm of microscopic physics, such as natural widths of spectral lines, Lamb shift, anomalous magnetic moment of the electron and many more. It is perhaps even more striking that there exist also observable effects at a macroscopic level. The Casimir force (static Casimir effect [1,2]) is one of these macroscopic effects which has been observed experimentally. A dynamic Casimir effect is also predicted to occur when one boundary is accelerated in a nonuniform way, as for instance when a metal surface undergoes harmonic oscillations. In this case a number of virtual photons from the vacuum are converted into real photons ("Casimir radiation"), while the moving metal surface loses energy [3,4,5].It is worth notice that, whereas the static Casimir effect has been observed by several experiments [6], the Casimir radiation is to date unobserved, in spite of the abundant theoretical work done in this field [7,8,9,10,11] (see [8] for a historical review and a bibliography of the relevant studies). We argue that this lack of experimental activity stems from the rooted idea of using mechanical oscillations. We shall show that this is unfeasible with present-day techniques.Here we shall present a new experimental approach where an effective motion is generated by the excitation of a plasma in a semiconductor. In terms of power this effective motion is much more convenient than a mechanical motion, since in a metal mirror only the conduction electrons reflect the electromagnetic waves, whereas a great amount of power would be wasted in the acceleration of the much heavier nuclei. Some authors [12,13,14] have made use of our idea in order to cons...
According to QED a metallic mirror set in motion in quantum vacuum gives rise to “dissipated” energy in the form of real photons. This phenomenon, called dynamical Casimir effect, has never been observed due to unsolved technical difficulties: in order to obtain an experimentally measurable number of photons from vacuum fluctuations a reflecting surface has in fact to vibrate at very high frequencies 109 Hz. As these frequencies are too high to be achieved with a purely mechanical oscillation, our idea is to switch an effective microwave mirror on and off at very short intervals of time changing the reflectivity of a semiconductor layer by shining a pulsed laser beam on its surface. The first step to study the feasibility of this technique is to show that a semiconductor slab when illuminated by a laser behaves indeed as a metal. This article presents the measurements that confirm this demand, obtained by uniformly illuminating large (several square centimeters) surfaces of silicon and GaAs
A system with several lines for the preparation of graphite targets for radiocarbon analysis has been built at the new accelerator mass spectrometry (AMS) facility in Caserta, Italy. Special attention has been paid in the design to the reduction of background contamination during sample preparation. Here, we describe the main characteristics of these preparation lines. Results of tests performed to measure 14C background levels and isotope fractionation in several blank samples with the Caserta AMS system are presented and discussed.
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