Überblick über die neueren Arbeiten auf dem Gebiet des Wasserstoff-und Tritiumverhaltens in Hochtemperaturreaktoren

This report comprises the contributions of members of the "Institut für Reaktor-Entwicklung" (IRE) to the "Und Seminar on Hydrogen and Tritium Behaviour in High Temperature Reactors", which was held March 8, 1978, at KFA Jülich. At the beginning the problem is introduced and the investigations at IRE related to this area are presented in their context. Then follow the individual papers on the subjects mentioned. At first the experiences with the operation of the experimental facility AUWARM and the newest results in the current testing program are discussed. Therafter the model investigations with hydrogen and deuterium on the problem of hydrogen- and tritium permeation are reported and a computer program for balancing tritium in pebble-bed-HTRs is described. Last notleast the studies on the behaviour of tritium in matrix graphite and the experiments on primary coolant purification by titanium gettering are shortly communicated. The results given in this report are preliminary informations on the actual status of the current investigations

Coherent manipulation of atomic qubits in optical micropotentials

We experimentally demonstrate the coherent manipulation of atomic states in far-detuned dipole traps and registers of dipole traps based on two-dimensional arrays of microlenses. By applying Rabi, Ramsey, and spin-echo techniques, we systematically investigate the dephasing mechanisms and determine the coherence time. Simultaneous Ramsey measurements in up to 16 dipole traps are performed and proves the scalability of our approach. This represents an important step in the application of scalable registers of atomic qubits for quantum information processing. In addition, this system can serve as the basis for novel atomic clocks making use of the parallel operation of a large number of individual clocks each remaining separately addressable.Comment: to be published in Appl. Phys.

Multiple micro-optical atom traps with a spherically aberrated laser beam

We report on the loading of atoms contained in a magneto-optic trap into multiple optical traps formed within the focused beam of a CO_{2} laser. We show that under certain circumstances it is possible to create a linear array of dipole traps with well separated maxima. This is achieved by focusing the laser beam through lenses uncorrected for spherical aberration. We demonstrate that the separation between the micro-traps can be varied, a property which may be useful in experiments which require the creation of entanglement between atoms in different micro-traps. We suggest other experiments where an array of these traps could be useful.Comment: 10 pages, 3 figure

Wave Packet Echoes in the Motion of Trapped Atoms

We experimentally demonstrate and systematically study the stimulated revival (echo) of motional wave packet oscillations. For this purpose, we prepare wave packets in an optical lattice by non-adiabatically shifting the potential and stimulate their reoccurence by a second shift after a variable time delay. This technique, analogous to spin echoes, enables one even in the presence of strong dephasing to determine the coherence time of the wave packets. We find that for strongly bound atoms it is comparable to the cooling time and much longer than the inverse of the photon scattering rate

Quantum computing in optical microtraps based on the motional states of neutral atoms

We investigate quantum computation with neutral atoms in optical microtraps where the qubit is implemented in the motional states of the atoms, i.e., in the two lowest vibrational states of each trap. The quantum gate operation is performed by adiabatically approaching two traps and allowing tunneling and cold collisions to take place. We demonstrate the capability of this scheme to realize a square-root of swap gate, and address the problem of double occupation and excitation to other unwanted states. We expand the two-particle wavefunction in an orthonormal basis and analyze quantum correlations throughout the whole gate process. Fidelity of the gate operation is evaluated as a function of the degree of adiabaticity in moving the traps. Simulations are based on rubidium atoms in state-of-the-art optical microtraps with quantum gate realizations in the few tens of milliseconds duration range.Comment: 11 pages, 7 figures, for animations of the gate operation, see http://www.itp.uni-hannover.de/~eckert/na/index.htm

Implications of SU(2) symmetry on the dynamics of population difference in the two-component atomic vapor

We present an exact many body solution for the dynamics of the population difference $N_2-N_1$ induced by an rf-field in the two-component atomic cloud characterized by equal scattering lengths. This situation is very close to the actual JILA experiments with the two-component $^{87}$Rb vapor. We show that no intrinsic decoherence exists for $N_2-N_1$, provided the exact SU(2) symmetry holds. This contrasts with finite dissipation of the normal modes even in the presence of the SU(2) symmetry. The intrinsic decoherence for \$N_2-N_1$ may occur as long as deviations from the exact SU(2) symmetry are taken into account. Such decoherence, however, should be characterized by very long times governed by the smallness of the deviations from the symmetry. We suggest testing the evolution of $N_2-N_1$ by conducting echo-type experiments.Comment: 5 RevTex pages, no figures, typos correcte

Top Partner Discovery in the T→tZT\to tZ channel at the LHC

In this paper we study the discovery potential of the LHC run II for heavy vector-like top quarks in the decay channel to a top and a $Z$ boson. Despite the usually smaller branching ratio compared to charged-current decays, this channel is rather clean and allows for a complete mass reconstruction of the heavy top. The latter is achieved in the leptonic decay channel of the $Z$ boson and in the fully hadronic top channel using boosted jet and jet substructure techniques. To be as model-independent as possible, a simplified model approach with only two free parameters has been applied. The results are presented in terms of parameter space regions for $3\sigma$ evidence or $5\sigma$ discovery for such new states in that channel.Comment: 24 pages, 8 figures, version 2 updated to JHEP 01 (2015) 08

The Swiss Kidney Stone Cohort (SKSC), a longitudinal, multi-centric, observational cohort to study course and causes of kidney stone disease in Switzerland.

Kidney stone disease has a high prevalence worldwide of approximately 10 % of the population and is characterized by a high recurrence rate Kidney stone disease results from a combination of genetic, environmental, and life-style risk factors, and the dissection of these factors is complex. The Swiss Kidney Stone Cohort (SKSC) is an investigator-initiated prospective, multi-centric longitudinal, observational study in patients with kidney stones followed with regular visits over a period of 3 years after inclusion. Ongoing follow-ups by biannual telephone interviews will provide long-term outcome data up to 10 years. SKSC comprises 782 adult patients (age > 18 yrs) with either recurrent stones or a single stone event with at least one risk factor for recurrence. In addition, a control cohort of 207 individuals without kidney stone history and absence of kidney stones on a low-dose CT-scan at enrolment has also been recruited. SKSC includes extensive collections of clinical data, biochemical data in blood and 24 hr urine samples, and genetic data. Biosamples are stored at a dedicated biobank. Information on diet and dietary habits were collected through food frequency questionnaires and standardized recall interviews by trained dieticians with the Globodiet software. SKSC provides an unique opportunity and resource to further study cause and course of kidney disease in a large population with data and samples collected of a homogenous collective of patients throughout the whole Swiss population