All-solid-state radiometers for environmental studies to 700 GHz

We report results with an all-solid-state radiometer for measurements of the ClO molecule at 649 GHz. The project is part of a program to provide low-noise, low-weight, low-power radiometers for space operation, and special effort has been expended on the development of high-efficiency solid-state frequency multipliers and Schottky-barrier mixers with low local oscillator power requirements. The best measured system noise temperature was 1750 K with the mixer and preamplifier cooled to 77 K. The mixer diode was easily pumped into saturation, indicating that the design has excellent prospects of operating at higher frequencies - our present design goal being 1 THz. We comment on the principal design features of such systems and will report on stratospheric measurements performed with this system

Inside out, outside in?: Eine »Außenbereichsinsel« im Innenbereich

Übungsklausur Der von K ordnungsgemäß bevollmächtigte F beantragt in dessen Namen deshalb am 1. 3. 2012 formgerecht bei der Stadt L die Erteilung einer »Bebauungsgenehmigung « für das Grundstück des K, bezogen auf die Errichtung des geplanten »Factory-Outlet-Centers«, dessen Erschließung durch den Bau zweier Zufahrten in westlicher und östlicher Richtung gesichert werden soll und auch im Übrigen gesichert ist. Die Stadt L versagt jedoch mit Bescheid vom 10. 4. 2012 den Erlass der begehrten Genehmigung. Dabei verweist sie darauf, dass das Vorhaben den Vorgaben des Flächennutzungsplanes widerspreche sowie das Erfordernis einer förmlichen Bauleitplanung als öffentlicher Belang i. S. v. § 35 III 1 BauGB beeinträchtigt und daher das Vorhaben bauplanungsrechtlich nicht genehmigungsfähig sei. Marktanalysen hätten ergeben, dass – was zutrifft – der Textilmarkt in der Kreisfreien Stadt L und den umliegenden Gemeinden übersättigt sei, weshalb weitere Verkaufsflächen für Textilien ohne Schaden für die mittelständische Textilwirtschaft nicht zugelassen werden könnten. Deswegen verweigere man auch das gemeindliche Einvernehmen

A proposed experiment on the proton driven plasma wakefield acceleration

Simulations have shown that a high energy, short and intense proton beam can drive a large amplitude plasma wave and accelerate an electron beam to the energy frontier in a single plasma channel. To verify this novel idea, a proof-of-principle demonstration experiment is now being planned. The idea is to use the available high energy proton beams either from the Proton Synchrotron (PS) or the Super Proton Synchrotron (SPS) at CERN, to shoot the beam into a plasma cell and to excite the plasma wakefield. A strong density modulation due to the excited plasma wakefield is produced for a long drive beam and this modulated beam in turn produces a high electric field. The proposed experimental setup is introduced in this paper. The interactions between the plasma and the proton beam are simulated and the results are presented. The compression of an SPS bunch is also discussed.Comment: This paper is submitted to the proceedings of the first International Particle Accelerator Conference (IPAC10)in Kyoto, Japa

A Concept for the LHC Luminosity Upgrade Based on Strong Beta* Reduction combined with a Minimized Geometric Luminosity Loss Factor

A significant reduction of b* requires a new beam crossing scheme to overcome the consequence of the luminosity loss factor. We define in this paper the parameters of a possible solution taking advantage of an early separation scheme optionally supplemented by a weak crab crossing. Large aperture (150 mm) Nb$_{3}$Sn triplet quadrupoles are chosen for their compactness, temperature margin and ability to relax the collimator gap and impedance. This concept offers high performance for a moderate increase of complexity. An open issue is the possibility of integrating dipoles inside the detectors

An alternative nonlinear collimation system for the LHC

The optics design of an alternative nonlinear collimation system for the LHC is presented. We discuss an optics scheme based on a single spoiler located in between a pair of skew sextupoles for betatron collimation. The nonlinear system allows opening up the collimator gaps, thereby, reduces the collimator impedance, which presently limits the LHC intensity. After placing secondary collimators at locations behind the spoiler, we analyze the beam losses and calculate the cleaning efficiency from tracking studies. The results are compared with those of the conventional linear collimation system

Constructive approach to limiting periodic orbits with exponential and power law dynamics

In dynamical systems limit cycles arise as a result of a Hopf bifurcation, after a control parameter has crossed its critical value. In this study we present a constructive method to produce dissipative dynamics which lead to stable periodic orbits as time grows, with predesigned transient dynamics. Depending on the construction method a) the limiting orbit can be a regular circle, an ellipse or a more complex closed orbit and b) the approach to the limiting orbit can follow an exponential law or a power law. This technique allows to design nonlinear models of dynamical systems with desired (exponential or power law) relaxation properties.Comment: 17 pages, 6 figure

Tune shift induced by nonlinear resistive wall wake field of flat collimator

We present formulae for the coherent and incoherent tune shifts due to the nonlinear resistive wall wake field for a single beam traveling between two parallel plates. In particular, we demonstrate that the nonlinear terms of the resistive-wall wake field become important if the gap between the plates is comparable to the transverse rms beam size. We also compare the theoretically predicted tune shift as a function of gap size with measurements for an LHC prototype graphite collimator in the CERN SPS and with simulations

Transverse Impedance of LHC Collimators

The transverse impedance in the LHC is expected to be dominated by the numerous collimators, most of which are made of Fibre-Reinforced-Carbon to withstand the impacts of high intensity proton beams in case of failures, and which will be moved very close to the beam, with full gaps of few millimetres, in order to protect surrounding super-conducting equipments. We present an estimate of the transverse resistive-wall impedance of the LHC collimators, the total impedance in the LHC at injection and top energy, the induced coupled-bunch growth rates and tune shifts, and finally the result of the comparison of the theoretical predictions with measurements performed in 2004 and 2006 on a prototype collimator installed in the SPS