[en] In time-of-flight mass spectrometry the mass resolution can be improved by the use of energy focusing electric fields. Calculations on the design of a third order energy focusing instrument have been performed. (orig.)

[en] First results obtained with the MPI supported laboratory setup of a long distance time-of-flight mass-spectrometer confirm the applicability of the method to use laser-ionisation for remote analysis of small celestial bodies. After ratification of the treaty on Soviet-German cooperation in science, a grant by the BMFT enables us to participate in the LIMA-D flight instrument. We have now improved the operating system for the instrument and the data collection algorithm. In the laboratory we set up a unit to check the response of a multiplier system to complex input currents as they occur e.g. in the case of a mass spectrum. As laser-ionisation is a highly non-linear process, where ion yields depend on a lot of parameters, an extensive laboratory study, in which we cooperate with colleagues from IKI in Moscow, FMI in Helsinki, and the University of Kaiserslautern, shall give actual ion yields and ion energies for the range of laser and focus conditions used in the PHOBOS flyby configuration. These data shall be available when the flyby takes place in December 1989. (orig.)

No abstract available

[en] A new series array of 1440 Josephson tunnel junctions has been developed and tested as a reference voltage standard. It yields microwave induced quantized voltage steps up to 1.3 V. The steps are usually stable for more than 5 h with a microwave driving frequency of either 70 or 90 GHz. A high-resolution comparison of a constant voltage step at the 1-V level with the electromotive force of a saturated Weston cell is described. The comparison shows that the step voltage is constant to within +- 1 nV over the full step width

[en] Superconducting microwave monolithic integrated circuits (S-MMIC), based on Josephson tunnel junctions, are a well-established tool to reproduce the volt at the highest level of accuracy. An external oscillator of a fixed frequency f supplies microwave energy through a waveguide to the S-MMIC. The wave changes its mode at a waveguide-antipodal finline-stripline taper before entering a series array stripline of up to 30 000 Josephson tunnel junctions and is dissipated as heat in a lossy stripline. Both striplines have a characteristic impedance Z of 2 to 5 Ω. An equivalent circuit is shown in figure 1. The oscillator is matched to the waveguide with a source resistance R_G Z(waveguide) ∼ 550 Ω. The most critical part is the taper, which should work as a lossless impedance matching network at the frequency of the oscillator. Microwave energy is fed into the tunnel junctions by the surface current I_HF of the travelling wave in the series array stripline producing an rf voltage amplitude U_JHF across the capacitance C of each junction. The Josephson tunnel junctions work as self-oscillating parametric mixers producing steps of constant voltage V in the current-voltage characteristic whenever (nf - 2eV/h) = 0, with n denoting an integer and e and h denoting the elementary charge and Planck's constant, respectively. The equivalent circuit of a Josephson tunnel element used in a voltage standard for 1 V working at a frequency of f = 70 GHz is given by a lumped parallel resonant circuit with a nonlinear inductance on the order of L = φ₀/2πI₀ ∼ 1 pH, flux quantum φ₀ = h/2e and a linear capacitance of C ∼ 40 pF. These tunnel junctions have a maximum zero voltage current of approximately I₀ ∼ 350 μA. (orig.)

[en] A new series array of 1440 Josephson tunnel junctions has been developed and tested as a reference voltage standard. It yields microwave induced quantized voltage steps up to 1.3 V. The steps are usually stable for more than 5 h with a microwave driving frequency of either 70 or 90 GHz. A high-resolution comparison of a constant voltage step at the 1-V level with the electromotive force of a saturated Weston cell is described. The comparison shows that the step voltage is constant to within +- 1 nV over the full step width

[en] 1000 Ω and 1290.64 Ω coaxial resistors with calculable frequency dependence have been realized at PTB to be used in quantum Hall effect-based impedance measurements. In contradistinction to common designs of coaxial resistors, the design described in this paper makes it possible to remove the resistive element from the shield and to handle it without cutting the outer cylindrical shield of the resistor. Emphasis has been given to manufacturing technology and suppressing unwanted sources of frequency dependence. The adjustment accuracy is better than 10 µΩ Ω⁻¹