Keramische Supraleiter-Quanteninterferometer im Magnetfeld: Rauschreduktion durch gezielte Flussfadenverankerung mittels Antidots
Keramische Supraleiter-Quanteninterferometer im Magnetfeld: Rauschreduktion durch gezielte Flussfadenverankerung mittels Antidots
Topic of this work is the analysis and improvement of the sensitivity of high-Tcsuperconducting rf-SQUIDs for operation in unshielded environment. The increase ofthe low-frequency noise due vortex motion in an applied magnetic field leads to adrastic reduction of sensibility of the sensors, which af...
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Personal Name(s): | Selders, Peter A. (Corresponding author) |
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Contributing Institute: |
Publikationen vor 2000; PRE-2000; Retrocat |
Imprint: |
Jülich
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
2000
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Physical Description: |
IV, 131 p. |
Document Type: |
Report Book |
Research Program: |
Addenda |
Series Title: |
Berichte des Forschungszentrums Jülich
3826 |
Link: |
OpenAccess OpenAccess |
Publikationsportal JuSER |
Topic of this work is the analysis and improvement of the sensitivity of high-Tcsuperconducting rf-SQUIDs for operation in unshielded environment. The increase ofthe low-frequency noise due vortex motion in an applied magnetic field leads to adrastic reduction of sensibility of the sensors, which affects possible application ofSQUIDs. Aim of this work was the reduction of the vortex motion by simplemeasures, i. e. specially positioned micrometer holes (antidots), in order to achieve afield independent noise performance of the SQUIDs. This work can be divided intothree major parts: 1. The penetration and motion of vortices in rf-Washer SQUIDs with applied magneticfield has been examined and compared with existing models of the surface barrierand the thermal activated vortex motion. 2. Concepts for the reduction of the low frequency noise due to vortex motion havebeen developed. These are based on the pinning of vortices by artificial defectsespecially micrometer holes, so called antidots. 3. The noise reduction due to vortex pinning by antidots in rf-Washer SQUIDs in anapplied magnetic field has been experimentally demonstrated in field-cooled andzero-field cooled measurements. In the frame of this work the connections between the penetration and motion ofvortices into and in the washer of the SQUID on one hand and the low frequencynoise on the other hand are proved and illuminated by different measurements. Thepenetration and motion of single vortices into and in the washer of the SQUIDs hasbeen detected. The reduction of the low frequency noise in applied magnetic fields tothe zero field level is realized by special arrangements of antidots. A shift of the onsetof the increase of the low frequency noise from 8$\mu$T for the SQUIDs without antidotsto 40$\mu$T in field-cooled measurements and to 25$\mu$T in zero-field cooledmeasurements with SQUIDs with antidots is achieved. The developed measurementtechniques are well suited for the further examination of the properties of vortices inrf-Washer SQUIDs and the vortex antidot interaction. |