The Conductance of a Perfect Thin Film with Diffuse Surface Scattering

The conductance of thin films with diffusive surface scattering was solved semi-classically by Fuchs and Sondheimer. However, when the intrinsic electron mean free path is very large or infinite their conductance diverges. In this letter a simple diffraction picture is presented. It yields a conductance which corresponds to a limiting mean free path. PACS: 73.50.-h, 73.50.Bk, 73.23.-b, 73.25.+i, B14

New design of electrostatic mirror actuators for application in high-precision interferometry

We describe a new geometry for electrostatic actuators to be used in sensitive laser interferometers, suited for prototype and table top experiments related to gravitational wave detection with mirrors of 100 g or less. The arrangement consists of two plates at the sides of the mirror (test mass), and therefore does not reduce its clear aperture as a conventional electrostatic drive (ESD) would do. Using the sample case of the AEI-10 m prototype interferometer, we investigate the actuation range and the influence of the relative misalignment of the ESD plates with respect to the test mass. We find that in the case of the AEI-10 m prototype interferometer, this new kind of ESD could provide a range of 0.28 μm when operated at a voltage of 1 kV. In addition, the geometry presented is shown to provide a reduction factor of about 100 in the magnitude of the actuator motion coupling to the test mass displacement. We show that therefore in the specific case of the AEI-10 m interferometer, it is possible to mount the ESD actuators directly on the optical table without spoiling the seismic isolation performance of the triple stage suspension of the main test masses

Coherent population transfer beyond the adiabatic limit: generalized matched pulses and higher-order trapping states

We show that the physical mechanism of population transfer in a 3-level system with a closed loop of coherent couplings (loop-STIRAP) is not equivalent to an adiabatic rotation of the dark-state of the Hamiltonian but coresponds to a rotation of a higher-order trapping state in a generalized adiabatic basis. The concept of generalized adiabatic basis sets is used as a constructive tool to design pulse sequences for stimulated Raman adiabatic passage (STIRAP) which give maximum population transfer also under conditions when the usual condition of adiabaticty is only poorly fulfilled. Under certain conditions for the pulses (generalized matched pulses) there exists a higher-order trapping state, which is an exact constant of motion and analytic solutions for the atomic dynamics can be derived.Comment: 15 pages, 9 figure

Photoionization Suppression by Continuum Coherence: Experiment and Theory

We present experimental and theoretical results of a detailed study of laser-induced continuum structures (LICS) in the photoionization continuum of helium out of the metastable state 2s $^1S_0$. The continuum dressing with a 1064 nm laser, couples the same region of the continuum to the {4s $^1S_0$} state. The experimental data, presented for a range of intensities, show pronounced ionization suppression (by as much as 70% with respect to the far-from-resonance value) as well as enhancement, in a Beutler-Fano resonance profile. This ionization suppression is a clear indication of population trapping mediated by coupling to a contiuum. We present experimental results demonstrating the effect of pulse delay upon the LICS, and for the behavior of LICS for both weak and strong probe pulses. Simulations based upon numerical solution of the Schr\"{o}dinger equation model the experimental results. The atomic parameters (Rabi frequencies and Stark shifts) are calculated using a simple model-potential method for the computation of the needed wavefunctions. The simulations of the LICS profiles are in excellent agreement with experiment. We also present an analytic formulation of pulsed LICS. We show that in the case of a probe pulse shorter than the dressing one the LICS profile is the convolution of the power spectra of the probe pulse with the usual Fano profile of stationary LICS. We discuss some consequences of deviation from steady-state theory.Comment: 29 pages, 17 figures, accepted to PR

Complementarity relation for irreversible process derived from stochastic energetics

When the process of a system in contact with a heat bath is described by classical Langevin equation, the method of stochastic energetics [K. Sekimoto, J. Phys. Soc. Jpn. vol. 66 (1997) p.1234] enables to derive the form of Helmholtz free energy and the dissipation function of the system. We prove that the irreversible heat Q_irr and the time lapse $Delta t} of an isothermal process obey the complementarity relation, Q_irr {Delta t} >= k_B T S_min, where S_min depends on the initial and the final values of the control parameters, but it does not depend on the pathway between these values.Comment: 3 pages. LaTeX with 6 style macro

Measuring a coherent superposition

We propose a simple method for measuring the populations and the relative phase in a coherent superposition of two atomic states. The method is based on coupling the two states to a third common (excited) state by means of two laser pulses, and measuring the total fluorescence from the third state for several choices of the excitation pulses.Comment: 7 pages, 1 figure, twocolumn REVTe

Radiation Protection Considerations for the Cryogenic In Vacuum Undulator of the EMIL Project at BESSY

The Helmholtz Zentrum Berlin and the Max Planck Society implement a new dedicated X ray beamline at the synchrotron light source BESSY II for the analysis of materials for the regenerative energy generation. The project is called EMIL, the Energy Materials In Situ Laboratory Berlin, [1] and the beamlines had to deliver x rays with a needed energy range from 80 eV up to 12000 eV. Therefore two undulators will be placed in a single straight section, for soft x rays an elliptical APPLE II device and for hard x rays a cryogenic in vacuum undulator. To determine adequate measures of the shielding of synchrotron radiation in the experimental hall we use the particle transport code FLUKA [2] [3]. We calculated the synchrotron radiation spectra for the cryogenic undulator with the code SPECTRA10 [4]. After modeling the modified section of the storage ring and the new beamlines we determined the thickness of the shielding walls of the hutches with the results of spectra sampling with FLUKA up to 30000 eV. The APPLE II undulator don t has to be considered for the hutch design because of its low energy synchrotron radiation 80 eV up to 2000 eV which is absorbed in the vacuum system. Additionally we considered the effects of the bremsstrahlung with FLUKA simulations

Fluka Calculations of Gamma Spectra at BESSY

Since 22nd October 2012 the synchrotron light source BESSY is operated in top up mode. Losses of electrons during injection cause an electromagnetic cascade, that consists of high energetic photons of the bremsstrahlung, and secondary electrons and positrons from the pair creations. The bremsstrahlung spectrum has a maximum at 1.022 MeV owing to pair creations. The spectrum has a high energetic tail, that reaches up to the electron energy of 1.7 GeV at BESSY. The low energy part of the electromagnetic cascade is produced by compton scattering or the photo effect. Due to the opened beamshutters during top up injections, the low energetic part of the bremsstrahlung spectrum can reach the experimental hall. We used the particle interaction and transport code FLUKA for the calculations of both the fluence and the dose distribution. We calculated the gamma spectra of the radiation through the shielding walls and through the front ends. We discussed the question whether additional safety measures are necessary for top up operation due to the low energy part of the spectrum. From our calculations we determined the correction factors for our ionisation chambers of the ambient dose measurement syste