584 research outputs found
Icing tunnel tests of a glycol-exuding porous leading edge ice protection system on a general aviation airfoil
A glycol-exuding porous leading edge ice protection system was tested. Results show that the system is very effective in preventing ice accretion (anti-ice mode) or removing ice from an airfoil. Minimum glycol flow rates required for anti-icing are a function of velocity, liquid water content in the air, ambient temperature, and droplet size. Large ice caps were removed in only a few minutes using anti-ice flow rates. It was found that the shed time is a function of the type of ice, size of the ice cap, angle of attack, and glycol flow rate. Wake survey measurements show that there is no significant drag penalty for the installation or operation of the system tested
Evaluation of a pneumatic boot deicing system on a general aviation wing model
The aerodynamic characteristics of a typical modern general aviation airfoil were investigated with and without a pneumatic boot ice protection system. The ice protection effectiveness of the boot was studied. This includes the change in drag on the airfoil with the boot inflated and deflated, the change in drag due to primary and residual ice formation, drag change due to cumulative residual ice formation, and parameters affecting boot effectiveness. Boot performance was not affected by tunnel total temperature or velocity. Marginal effect in performance was associated with angle of attack. Significant effects on performance were caused by variations in droplet size, LWC, ice cap thickness inflation pressure, and surface treatment
The Ramsey method in high-precision mass spectrometry with Penning traps: Experimental results
The highest precision in direct mass measurements is obtained with Penning
trap mass spectrometry. Most experiments use the interconversion of the
magnetron and cyclotron motional modes of the stored ion due to excitation by
external radiofrequency-quadrupole fields. In this work a new excitation
scheme, Ramsey's method of time-separated oscillatory fields, has been
successfully tested. It has been shown to reduce significantly the uncertainty
in the determination of the cyclotron frequency and thus of the ion mass of
interest. The theoretical description of the ion motion excited with Ramsey's
method in a Penning trap and subsequently the calculation of the resonance line
shapes for different excitation times, pulse structures, and detunings of the
quadrupole field has been carried out in a quantum mechanical framework and is
discussed in detail in the preceding article in this journal by M. Kretzschmar.
Here, the new excitation technique has been applied with the ISOLTRAP mass
spectrometer at ISOLDE/CERN for mass measurements on stable as well as
short-lived nuclides. The experimental resonances are in agreement with the
theoretical predictions and a precision gain close to a factor of four was
achieved compared to the use of the conventional excitation technique.Comment: 12 pages, 14 figures, 2 table
Ordered structures in rotating ultracold Bose gases
The characterization of small samples of cold bosonic atoms in rotating
microtraps has recently attracted increasing interest due to the possibility to
deal with a few number of particles per site in optical lattices. We analyze
the evolution of ground state structures as the rotational frequency
increases. Various kinds of ordered structures are observed. For atoms,
the standard scenario, valid for large sytems, is absent, and only gradually
recovered as increases. The vortex contribution to the total angular
momentum as a function of ceases to be an increasing function of
, as observed in experiments of Chevy {\it et al.} (Phys. Rev. Lett.
85, 2223 (2000)). Instead, for small , it exhibits a sequence of peaks
showing wide minima at the values of , where no vortices appear.Comment: 35 pages, 17 figure
A multi-reflection time-of-flight mass spectrometer for the offline ion source of the PUMA experiment
The antiProton Unstable Matter Annihilation experiment (PUMA) at CERN aims at
investigating the nucleon composition in the matter density tail of radioactive
as well as stable isotopes by use of low-energy antiproton-nucleon annihilation
processes. For this purpose, antiprotons provided by the Extra Low ENergy
Antiproton (ELENA) facility will be trapped together with the ions of interest.
While exotic ions will be obtained by the Isotope mass Separator On-Line DEvice
(ISOLDE), stable ions will be delivered from an offline ion source setup
designed for this purpose. This allows the proposed technique to be applied to
a variety of stable nuclei and for reference measurements. For beam
purification, the ion source setup includes a multi-reflection time-of-flight
mass spectrometer (MR-ToF MS). Supported by SIMION simulations, an earlier
MR-ToF MS design has been modified to meet the requirements of PUMA. During
commissioning of the new MR-ToF device with Ar ions, mass resolving powers
in excess of 50,000 have been obtained after 150 revolutions, limited by the
chopping of the continuous beam from an electron impact ionisation source
Shape oscillation of a rotating Bose-Einstein condensate
We present a theoretical and experimental analysis of the transverse monopole
mode of a fast rotating Bose-Einstein condensate. The condensate's rotation
frequency is similar to the trapping frequency and the effective confinement is
only ensured by a weak quartic potential. We show that the non-harmonic
character of the potential has a clear influence on the mode frequency, thus
making the monopole mode a precise tool for the investigation of the fast
rotation regime
Separated Oscillatory Fields for High-Precision Penning Trap Mass Spectrometry
Ramsey's method of separated oscillatory fields is applied to the excitation
of the cyclotron motion of short-lived ions in a Penning trap to improve the
precision of their measured mass. The theoretical description of the extracted
ion-cyclotron-resonance line shape is derived out and its correctness
demonstrated experimentally by measuring the mass of the short-lived Ca
nuclide with an uncertainty of using the ISOLTRAP Penning
trap mass spectrometer at CERN. The mass value of the superallowed beta-emitter
Ca is an important contribution for testing the conserved-vector-current
hypothesis of the electroweak interaction. It is shown that the Ramsey method
applied to mass measurements yields a statistical uncertainty similar to that
obtained by the conventional technique ten times faster.Comment: 5 pages, 4 figures, 0 table
Production and trapping of carbon clusters for absolute mass measurements at ISOLTRAP
Singly-charged carbon clusters C/sub n//sup +/ (n >or= 1) have been produced by laser-induced desorption and fragmentation of C/sub 60/ fullerenes and have been injected into and stored in the Penning trap system of the ISOLTRAP mass spectrometer at ISOLDE/CERN. The present study is the first step to extend the until now direct mass measurements at ISOLTRAP to absolute mass measurements by using clusters of /sup 12/C. (10 refs)
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