2,545 research outputs found
Amplifier for measuring low-level signals in the presence of high common mode voltage
A high common mode rejection differential amplifier wherein two serially arranged Darlington amplifier stages are employed and any common mode voltage is divided between them by a resistance network. The input to the first Darlington amplifier stage is coupled to a signal input resistor via an amplifier which isolates the input and presents a high impedance across this resistor. The output of the second Darlington stage is transposed in scale via an amplifier stage which has its input a biasing circuit which effects a finite biasing of the two Darlington amplifier stages
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
Development of neutron activation analysis procedures for the determination of oxygen in potassium final report, period ending 15 dec. 1964
Neutron activation analysis for determination of oxygen in potassiu
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
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
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
Temperature Dependence of Critical Current Fluctuations in Nb/AlO/Nb Josephson Junctions
We have measured the low frequency critical current noise in
Nb/AlO/Nb Josephson junctions. Unshunted junctions biased above
the gap voltage and resistively shunted junctions biased near the critical
current, , have been measured. For both, the spectral density of , , is proportional to , scales inversely as the
area, , and is independent of over a factor of nearly
20 in . For all devices measured at 4.2 K, (1 Hz)/Hz when scaled to A=1 m. We find that, from 4.2
K to 0.46 K, decreases linearly with temperature
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