Effect of Measurement on the Periodicity of the Coulomb Staircase of a Superconducting Box

We report on the effect of the back-action of a Single Cooper Pair Transistor electrometer (E) on the measurement of charge on the island of a superconducting box (B). The charge is e-periodic in the gate bias of B when E is operated near voltages 2Delta/e or 4Delta/e. We show that this is due to quasiparticle poisoning of B at a rate proportional to the number of quasiparticle tunneling events in E per second. We are able to eliminate this back action and recover 2e charge periodicity using a new measurement method based on switching current modulation of E.Comment: 4 pages, 4 figures, revised versio

Observation of Strong Coulomb Blockade in Resistively Isolated Tunnel Junctions

We report measurements of the Coulomb-blockade current in resistively isolated (R_{Isol} >> h/e^{2}) tunnel junctions for the temperature range 60mK $We report measurements of the Coulomb-blockade current in resistively isolated ($R_{Isol}\gg h/e^{2})$ tunnel junctions for the temperature range 60mK < T < 230mK where the charging energy E_{c} is much greater than the thermal energy. A zero-bias resistance R_{0} of up to 10^{4}R_{T} (the tunnel resistance of the bare junction) is obtained. For eV << E_{c}, the I-V curves for a given R_{Isol} scale as a function of V/T, with I \propto V^{\alpha (R_{Isol})} over a range of V. The data agree well with numerical calculations of the tunneling rate that include environmental effects.Comment: 13 pages, 3 eps figure

A study to develop neutron activation for measuring bone calcium content

Neutron activation analysis for measuring calcium in monkey bone

Radiation Due to Josephson Oscillations in Layered Superconductors

We derive the power of direct radiation into free space induced by Josephson oscillations in intrinsic Josephson junctions of highly anisotropic layered superconductors. We consider the super-radiation regime for a crystal cut in the form of a thin slice parallel to the c-axis. We find that the radiation correction to the current-voltage characteristic in this regime depends only on crystal shape. We show that at large enough number of junctions oscillations are synchronized providing high radiation power and efficiency in the THz frequency range. We discuss crystal parameters and bias current optimal for radiation power and crystal cooling.Comment: 4 pages, 1 figure, to be published in Phys. Rev. Let

Single-Electron Traps: A Quantitative Comparison of Theory and Experiment

We have carried out a coordinated experimental and theoretical study of single-electron traps based on submicron aluminum islands and aluminum oxide tunnel junctions. The results of geometrical modeling using a modified version of MIT's FastCap were used as input data for the general-purpose single-electron circuit simulator MOSES. The analysis indicates reasonable quantitative agreement between theory and experiment for those trap characteristics which are not affected by random offset charges. The observed differences between theory and experiment (ranging from a few to fifty percent) can be readily explained by the uncertainty in the exact geometry of the experimental nanostructures.Comment: 17 pages, 21 figures, RevTex, eps

Crossover from Kramers to phase-diffusion switching in hysteretic DC-SQUIDs

We have measured and propose a model for switching rates in hysteretic DC-SQUID in the regime where phase diffusion processes start to occur. We show that the switching rates in this regime are smaller than the rates given by Kramers' formula due to retrapping of Josephson phase. The retrapping process, which is affected by the frequency dependent impedance of the environment of the DC-SQUID, leads to a peaked second moment of the switching distribution as a function of temperature. The temperature where the peaks occur are proportional to the critical current of the DC- SQUID.Comment: 4 pages, 4 figure