6,826 research outputs found
Microstrip superconducting quantum interference device amplifiers with submicron Josephson junctions: enhanced gain at gigahertz frequencies
We present measurements of an amplifier based on a dc superconducting quantum
interference device (SQUID) with submicron Al-AlOx-Al Josephson junctions. The
small junction size reduces their self-capacitance and allows for the use of
relatively large resistive shunts while maintaining nonhysteretic operation.
This leads to an enhancement of the SQUID transfer function compared to SQUIDs
with micron-scale junctions. The device layout is modified from that of a
conventional SQUID to allow for coupling signals into the amplifier with a
substantial mutual inductance for a relatively short microstrip coil.
Measurements at 310 mK exhibit gain of 32 dB at 1.55 GHz.Comment: Version with high resolution figures at:
http://physics.syr.edu/~bplourde/bltp-publications.ht
A fast edge charge exchange recombination spectroscopy system at the ASDEX Upgrade tokamak
In this work, a new type of high through-put Czerny-Turner spectrometer has been developed which
allows us to acquire multiple channels simultaneously with a repetition time on the order of 10
μ
s
at different wavelengths. The spectrometer has been coupled to the edge charge exchange recom-
bination system at ASDEX Upgrade which has been recently refurbished with new lines of sight.
Construction features, calibration methods, and initial measurements obtained with the new setup will
be presented.European Commission (EUROfusion 633053
Interpretation of the I-Regime and transport associated with relevant heavy particle modes
The excitation of a novel kind of heavy particle [1, 2] mode at the edge of the plasma column is
considered as the signature of the I-con nement Regime [3{7]. The outward transport of impurities
produced by this mode is in fact consistent with the observed expulsion of them from the main
body of the plasma column (a high degree of plasma purity is a necessary feature for fusion burning
plasmas capable of approaching ignition). Moreover, the theoretically predicted mode phase velocity,
in the direction of the electron diamagnetic velocity, has been con rmed by relevant experimental
analyses [8] of the excited
uctuations (around 200 kHz). The plasma \spontaneous rotation" in the
direction of the ion diamagnetic velocity is also consistent, according to the Accretion Theory [9] of
this phenomenon, with the direction of the mode phase velocity. Another feature of the mode that
predicted by the theory is that the I-Regime exhibits a knee of the ion temperature at the edge of
the plasma column but not one of the particle density as the mode excitation factor is the relative
main ion temperature gradient exceeding the local relative density gradient. The net plasma current
density appearing in the saturation stage of the relevant instability, where the induced particle and
energy
uxes are drastically reduced, is associated with the signi cant amplitudes of the poloidal
magnetic eld
uctuations [6, 7] observed to accompany the density
uctuations. The theoretical
implications of the signi cant electron temperature
uctuations [10] observed are discussed.United States. Dept. of Energ
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