Fabrication and cryogenic stabilisation of (Bi,Pb)SrCaCuO-2223 superconducting tapes
Fabrication and cryogenic stabilisation of (Bi,Pb)SrCaCuO-2223 superconducting tapes
This thesis is in two parts which firstly investigates the influence of the sintering time prior to the last deformation and the sintering atmosphere on the critical current density (Jc) of (Bi, Pb)-2223 superconducting tapes. The second part investigates the fabrication procedure and the cryogenic stabilisation of a pancake coil made from commercial multifilamentry tape.
The effect of the sintering time prior to the first intermediate rolling, tSI, showed no strong optimising properties on the Jc. However, the total sintering time required to optimise the Jc increased with decreasing tSI. This behaviour could be explained by the inhomogeneity of the phases in the core at low values of tSI which required long sintering times to produce mature current paths.
The influence of the sintering time between the first and second intermediate deformation, tS2, on the Jc was studied. The results showed an optimum tS2 for various total sintering times. The highest Jc=2.1 x104 Acm-2 (77K, self field) was produced for tapes with a total sintering time of 140h and ts2-27h. In addition, the sintering time required to reach the peak Jc increased with ts2. This behaviour is believed to be associated with the availability of the liquid phase required to heal the microcracks after the last deformation process.
The effect of sintering in various oxygen partial pressures (pO2) on the transport Jc has been investigated. The melting temperature of BSCCO decreases proportionately with pO2, therefore, it was necessary to adjust the sintering temperature to maintain the same subcooling for each pO2. The results showed that the total sintering time required to reach an optimum Jc was longer for tapes sintered in air compared to low pO2, which may be due to a longer incubation period for tapes sintered in air. The field dependence was also stronger for tapes processed in low pO2 compared to air, which suggests that stronger grain boundaries were produced by slower conversion rates.
Normal-zone propagation and stability measurements were performed on a single pancake coil made from BSCCO-2223 multifilamentry tape. The coil composite was held above a subcooled nitrogen bath at 65K and thermal links between the coil and the bath provided cooling by conduction. The normal zone stability was investigated using heated regions of various lengths and power inputs. The results show that the total energy required to quench the coil (EQ) reduced as the length of the heated region decreased. For example, EQ=2.8J and 4.7J for heater lengths of 2.5cm and 14.6cm respectively. The measured velocity of the normal zone in the transverse direction was 1.75mms-1, and the longitudinal velocity was estimated to be 16.7mms-1. These results suggest that High-Tc devices require careful design to ensure safe operation and protection.
University of Southampton
1998
Penny, Marcus David
(1998)
Fabrication and cryogenic stabilisation of (Bi,Pb)SrCaCuO-2223 superconducting tapes.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
This thesis is in two parts which firstly investigates the influence of the sintering time prior to the last deformation and the sintering atmosphere on the critical current density (Jc) of (Bi, Pb)-2223 superconducting tapes. The second part investigates the fabrication procedure and the cryogenic stabilisation of a pancake coil made from commercial multifilamentry tape.
The effect of the sintering time prior to the first intermediate rolling, tSI, showed no strong optimising properties on the Jc. However, the total sintering time required to optimise the Jc increased with decreasing tSI. This behaviour could be explained by the inhomogeneity of the phases in the core at low values of tSI which required long sintering times to produce mature current paths.
The influence of the sintering time between the first and second intermediate deformation, tS2, on the Jc was studied. The results showed an optimum tS2 for various total sintering times. The highest Jc=2.1 x104 Acm-2 (77K, self field) was produced for tapes with a total sintering time of 140h and ts2-27h. In addition, the sintering time required to reach the peak Jc increased with ts2. This behaviour is believed to be associated with the availability of the liquid phase required to heal the microcracks after the last deformation process.
The effect of sintering in various oxygen partial pressures (pO2) on the transport Jc has been investigated. The melting temperature of BSCCO decreases proportionately with pO2, therefore, it was necessary to adjust the sintering temperature to maintain the same subcooling for each pO2. The results showed that the total sintering time required to reach an optimum Jc was longer for tapes sintered in air compared to low pO2, which may be due to a longer incubation period for tapes sintered in air. The field dependence was also stronger for tapes processed in low pO2 compared to air, which suggests that stronger grain boundaries were produced by slower conversion rates.
Normal-zone propagation and stability measurements were performed on a single pancake coil made from BSCCO-2223 multifilamentry tape. The coil composite was held above a subcooled nitrogen bath at 65K and thermal links between the coil and the bath provided cooling by conduction. The normal zone stability was investigated using heated regions of various lengths and power inputs. The results show that the total energy required to quench the coil (EQ) reduced as the length of the heated region decreased. For example, EQ=2.8J and 4.7J for heater lengths of 2.5cm and 14.6cm respectively. The measured velocity of the normal zone in the transverse direction was 1.75mms-1, and the longitudinal velocity was estimated to be 16.7mms-1. These results suggest that High-Tc devices require careful design to ensure safe operation and protection.
This record has no associated files available for download.
More information
Published date: 1998
Identifiers
Local EPrints ID: 463253
URI: http://eprints.soton.ac.uk/id/eprint/463253
PURE UUID: 3a461ecb-bee4-413c-9e49-ee6b92d2d8ba
Catalogue record
Date deposited: 04 Jul 2022 20:48
Last modified: 04 Jul 2022 20:48
Export record
Contributors
Author:
Marcus David Penny
Download statistics
Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.
View more statistics