Turbofan forced mixer lobe flow modeling. Part 3: Application to augment engines

Military engines frequently need large quantities of thrust for short periods of time. The addition of an augmentor can provide such thrust increases but with a penalty of increased duct length and engine weight. The addition of a forced mixer to the augmentor improves performance and reduces the penalty, as well as providing a method for siting the required flame holders. In this report two augmentor concepts are investigated: a swirl-mixer augmentor and a mixer-flameholder augmentor. Several designs for each concept are included and an experimental assessment of one of the swirl-mixer augmentors is presented

Effective-range approach and scaling laws for electromagnetic strength in neutron-halo nuclei

We study low-lying multipole strength in neutron-halo nuclei. The strength depends only on a few low-energy constants: the neutron separation energy, the asymptotic normalization coefficient of the bound state wave function, and the scattering length that contains the information on the interaction in the continuum. The shape of the transition probability shows a characteristic dependence on few scaling parameters and the angular momenta. The total E1 strength is related to the root-mean-square radius of the neutron wave function in the ground state and shows corresponding scaling properties. We apply our approach to the E1 strength distribution of 11Be.Comment: 4 pages, 1 figure (modified), additional table, extended discussion of example, accepted for publication in Phys. Rev. Let

Effective generation of cat and kitten states

We present an effective method of coherent state superposition (cat state) generation using single trapped ion in a Paul trap. The method is experimentally feasible for coherent states with amplitude $\alpha \le 2$ using available technology. It works both in and beyond the Lamb-Dicke regime.Comment: 11 pages, 8 figure

Experimental quantum information processing with 43Ca+ ions

For quantum information processing (QIP) with trapped ions, the isotope 43Ca+ offers the combined advantages of a quantum memory with long coherence time, a high fidelity read out and the possibility of performing two qubit gates on a quadrupole transition with a narrow-band laser. Compared to other ions used for quantum computing, 43Ca+ has a relatively complicated level structure. In this paper we discuss how to meet the basic requirements for QIP and demonstrate ground state cooling, robust state initialization and efficient read out for the hyperfine qubit with a single 43Ca+ ion. A microwave field and a Raman light field are used to drive qubit transitions, and the coherence times for both fields are compared. Phase errors due to interferometric instabilities in the Raman field generation do not limit the experiments on a time scale of 100 ms. We find a quantum information storage time of many seconds for the hyperfine qubit.Comment: 9 pages, 10 figure

Quasirelativistic quasilocal finite wave-function collapse model

A Markovian wave function collapse model is presented where the collapse-inducing operator, constructed from quantum fields, is a manifestly covariant generalization of the mass density operator utilized in the nonrelativistic Continuous Spontaneous Localization (CSL) wave function collapse model. However, the model is not Lorentz invariant because two such operators do not commute at spacelike separation, i.e., the time-ordering operation in one Lorentz frame, the "preferred" frame, is not the time-ordering operation in another frame. However, the characteristic spacelike distance over which the commutator decays is the particle's Compton wavelength so, since the commutator rapidly gets quite small, the model is "almost" relativistic. This "QRCSL" model is completely finite: unlike previous, relativistic, models, it has no (infinite) energy production from the vacuum state. QRCSL calculations are given of the collapse rate for a single free particle in a superposition of spatially separated packets, and of the energy production rate for any number of free particles: these reduce to the CSL rates if the particle's Compton wavelength is small compared to the model's distance parameter. One motivation for QRCSL is the realization that previous relativistic models entail excitation of nuclear states which exceeds that of experiment, whereas QRCSL does not: an example is given involving quadrupole excitation of the $^{74}$Ge nucleus.Comment: 10 pages, to be published in Phys. Rev.

Measurement of the hyperfine structure of the S1/2-D5/2 transition in 43Ca+

The hyperfine structure of the S1/2-D5/2 quadrupole transition at 729 nm in 43Ca+ has been investigated by laser spectroscopy using a single trapped 43Ca+ ion. We determine the hyperfine structure constants of the metastable level as A=-3.8931(2) MHz and B=-4.241(4) MHz. The isotope shift of the transition with respect to 40Ca+ was measured to be 4134.713(5) MHz. We demonstrate the existence of transitions that become independent of the first-order Zeeman shift at non-zero low magnetic fields. These transitions might be better suited for building a frequency standard than the well-known 'clock transitions' between m=0 levels at zero magnetic field.Comment: corrected for sign errors in the hyperfine constants. No corrections to were made to the data analysi

Conductance peaks in open quantum dots

We present a simple measure of the conductance fluctuations in open ballistic chaotic quantum dots, extending the number of maxima method originally proposed for the statistical analysis of compound nuclear reactions. The average number of extreme points (maxima and minima) in the dimensionless conductance, $T$, as a function of an arbitrary external parameter $Z$, is directly related to the autocorrelation function of $T(Z)$. The parameter $Z$ can be associated to an applied gate voltage causing shape deformation in quantum dot, an external magnetic field, the Fermi energy, etc.. The average density of maxima is found to be $= \alpha_{Z}/Z_c$, where $\alpha_{Z}$ is a universal constant and $Z_c$ is the conductance autocorrelation length, which is system specific. The analysis of $$ does not require large statistic samples, providing a quite amenable way to access information about parametric correlations, such as $Z_c$.Comment: 5 pages, 5 figures, accepted to be published - Physical Review Letter

Laser cooling with electromagnetically induced transparency: Application to trapped samples of ions or neutral atoms

A novel method of ground state laser cooling of trapped atoms utilizes the absorption profile of a three (or multi-) level system which is tailored by a quantum interference. With cooling rates comparable to conventional sideband cooling, lower final temperatures may be achieved. The method was experimentally implemented to cool a single Ca$^+$ ion to its vibrational ground state. Since a broad band of vibrational frequencies can be cooled simultaneously, the technique will be particularly useful for the cooling of larger ion strings, thereby being of great practical importance for initializing a quantum register based on trapped ions. We also discuss its application to different level schemes and for ground state cooling of neutral atoms trapped by a far detuned standing wave laser field.Comment: 9 pages, 13 figures, submitted to Appl Phys B 200

Paper Session I-B - Characterizing Space-Grown Degenerate Narrow Gap Semiconductors by Scanning Tunneling Optical Spectroscopy

We consider the II-VI narrow gap semiconducting alloys Hg(1-x)Cd(x)Te, Hg(1-x)Zn(x)Te, Hg(1-x)Zn(x)Se, for which empirical equations exist that give each alloy’s forbidden energy band gap Eg(x) as a function of its stoichiometry as characterized by the value x . These materials are important to NASA for two reasons. They are useful for making infrared detectors, and they are best grown in microgravity to optimize their uniformity. The equations can be inverted to yield the stoichiometry parameter x provided that the value of Eg can be determined experimentally, for example, by optical absorption measurements. We have investigated an alternative method, which should yield appreciably better spatial resolution, in which scanning tunneling optical spectroscopy (STOS) is used to measure the enhancement of the current that is due to photoexcitation of carriers at the tunneling junction in an STM. We present a simplified working model for low temperature calculations of STOS. Our major conclusions are: (a) for the degenerate case, knowledge of ND - NA (donor density minus the acceptor density) can be used to deduce the true band gap from the apparent band gap, (b) the low temperature tunneling current may have a sharper onset, depending on the diffusion length, at the band gap than does the optical absorption, and (c) our simplified formulation allows for quick, straightforward evaluation of many different cases and is in essential agreement with more detailed analysis