494 research outputs found
Investigation of external refrigeration systems for long term cryogenic storage Final report
Data on external refrigeration systems for space storage of cryogens for long period
SIRTF Telescope Instrument Changeout and Cryogen Replenishment (STICCR) Study
The Space Infrared Telescope Facility (SIRTF) is a long-life cryogenically cooled space-based telescope for infrared astronomy from 2 to 700 micrometers. SIRTF is currently under study by NASA-ARC (Reference AP) and planned for launch in approximately the mid 1990s. SIRTF will operate as a multiuser facility, initially carrying three instruments at the focal plane. It will be cooled to below 2 K by superfluid liquid helium to achieve radiometric sensitivity limited only by the statistical fluctuations in the natural infrared background radiation over most of its spectral range. The lifetime of the mission will be limited by the lifetime of the liquid helium supply, and baseline is currently to be 2 years. The telescope changes required to allow in-space replenishment of the 4,000-L superfluid helium tank was investigated. A preliminary design for the space services equipment was also developed. The impacts of basing the equipment and servicing on the space station were investigated. Space replenishment and changeout of instruments required changes to the telescope design. Preliminary concepts are presented
Mechanically reinforced MgB2 wires and tapes with high transport currents
Monofilamentary MgB2-wires with a 2- or 3-component sheath containing
mechanical reinforcing stainless steel (SS) were prepared and characterized. In
direct contact to the superconductor Nb, Ta or Fe was used. For a selection of
samples with a Fe and Fe/SS sheath, we investigated the transport critical
current behaviour in magnetic fields changing systematically the geometrical
shape from a round wire to a flat tape. A strong increase of the current
densities in flat tapes was observed and possible reasons for this are
discussed. Reinforcing the sheath in the outer layer with different amounts of
stainless steel leads to a systematic field dependent decrease of the transport
critical current density with increasing steel amount. This is an indication
for a pre-stress induced degradation of the critical currents in MgB2 wires and
first Ic-stress-strain experiments seem to confirm this observation and
interpretation.Comment: 12 pages, 5 figures. Submitted to Physica C (Proceedings of EUCAS
2001
Handbook of external refrigeration systems for long term cryogenic storage
Handbook of external refrigeration systems for long term cryogenic storag
High current DyBCO-ROEBEL Assembled Coated Conductor (RACC)
Low AC loss high transport current HTS cables (>1 kA) are required for
application in transformers, generators and are considered for future
generations of fusion reactors coils. 2G coated conductors are suitable
candidates for high field application at quite high operation temperatures of
50-77 K, which is crucial precondition for economical cooling costs. As a
feasibility study we present the first ROEBEL bar cable of approx. 35 cm length
made from industrial DyBCO coated conductor (THEVA GmbH, Germany). Meander
shaped ROEBEL strands of 4 mm width with a twist pitch of 180 mm were cut from
10 mm wide CC tapes using a specially designed tool. The strands carried in
average 157 Amps/cm-width DC and were assembled to a subcable with 5 strands
and a final cable with 16 strands. The 5 strand cable was tested and carried a
transport current of > 300 Amps DC at 77 K, equivalent to the sum of the
individual strand transport critical currents. The 16 strand cable carried 500
A limited through heating effects and non sufficient stabilisation and current
sharing. A pulse current load indicated a current carrying potential of > 1 kA
for the 16 strand cable.Comment: EUCAS2005, 11th.-15th.Sept.2005, Vienna Austria, to be published in
SUST, special issu
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