Strong magnetic field generation by superconducting bulk magnets using various types of refrigerators and considering an efficient magnetization

Kazuya Yokoyama, Tetsuo Oka

Research output: Chapter in Book/Report/Conference proceedingChapter

Abstract

We are developing several types of superconducting bulk magnets with the goal of their industrial application, and we are studying to improve the magnetic field by pulsedfield magnetization (PFM). It is important to select a suitable refrigerator for cooling a bulk superconductor. This paper investigates magnetizing characteristics when using different refrigerators. The first is a Stirling refrigerator, in which the ultimate temperature was up to 50 K, and the cooling capacity was 10 W at 77 K. The other is a dual-stage GM-type refrigerator, in which the ultimate temperature was 13 K and the cooling capacity was 5 W at 20 K. When cooling and magnetizing tests were carried out using a GdBCO bulk 60 mm in diameter and 20 mm thick, a maximum trapped field of 3.0 T was achieved at 55 K, in the case of the Stirling refrigerator. Moreover, we also studied to improve the efficiency of magnetic flux trapping. Recent upsizing of the diameter and enhancement of the performance of bulk superconductors make PFM difficult, due to a strong magnetic shield. We propose a bulk material with small holes to supply magnetic flux into the bulk efficiently because superconductivity is intentionally lowered in the portion with holes. On the other hand, we are anxious about the flux flow in a high applied field. To investigate the effect of the proposed method, small holes were drilled in a bulk material, and a fundamental experiment was carried out. It was confirmed that the magnetic flux penetrated at a low applied field as compared with the holeless bulk material; moreover, the flux flow was suppressed in a high applied field at a low temperature. Furthermore, we aim to optimize the number, size, and position of small holes.

Original languageEnglish
Title of host publicationHigh-Temperature Superconductors
Subtitle of host publicationOccurrence, Synthesis and Applications
PublisherNova Science Publishers, Inc.
Pages369-385
Number of pages17
ISBN (Electronic)9781536133424
ISBN (Print)9781536133417
Publication statusPublished - 2018 Jan 1
Externally publishedYes

Fingerprint

Refrigerators
Magnets
Magnetization
Magnetic fields
Magnetic flux
Cooling
Superconducting materials
Fluxes
Flux pinning
Superconductivity
Temperature
Industrial applications
Experiments

Keywords

  • Flux penetration
  • Heat generation
  • Pulsed field magnetization
  • REBCO bulk
  • Refrigerator
  • Trapped field

ASJC Scopus subject areas

  • Engineering(all)
  • Materials Science(all)

Cite this

Yokoyama, K., & Oka, T. (2018). Strong magnetic field generation by superconducting bulk magnets using various types of refrigerators and considering an efficient magnetization. In High-Temperature Superconductors: Occurrence, Synthesis and Applications (pp. 369-385). Nova Science Publishers, Inc..

Strong magnetic field generation by superconducting bulk magnets using various types of refrigerators and considering an efficient magnetization. / Yokoyama, Kazuya; Oka, Tetsuo.

High-Temperature Superconductors: Occurrence, Synthesis and Applications. Nova Science Publishers, Inc., 2018. p. 369-385.

Research output: Chapter in Book/Report/Conference proceedingChapter

Yokoyama, K & Oka, T 2018, Strong magnetic field generation by superconducting bulk magnets using various types of refrigerators and considering an efficient magnetization. in High-Temperature Superconductors: Occurrence, Synthesis and Applications. Nova Science Publishers, Inc., pp. 369-385.
Yokoyama K, Oka T. Strong magnetic field generation by superconducting bulk magnets using various types of refrigerators and considering an efficient magnetization. In High-Temperature Superconductors: Occurrence, Synthesis and Applications. Nova Science Publishers, Inc. 2018. p. 369-385
Yokoyama, Kazuya ; Oka, Tetsuo. / Strong magnetic field generation by superconducting bulk magnets using various types of refrigerators and considering an efficient magnetization. High-Temperature Superconductors: Occurrence, Synthesis and Applications. Nova Science Publishers, Inc., 2018. pp. 369-385
@inbook{30a9e3ce442c426b9b6ca90a50d2c76c,
title = "Strong magnetic field generation by superconducting bulk magnets using various types of refrigerators and considering an efficient magnetization",
abstract = "We are developing several types of superconducting bulk magnets with the goal of their industrial application, and we are studying to improve the magnetic field by pulsedfield magnetization (PFM). It is important to select a suitable refrigerator for cooling a bulk superconductor. This paper investigates magnetizing characteristics when using different refrigerators. The first is a Stirling refrigerator, in which the ultimate temperature was up to 50 K, and the cooling capacity was 10 W at 77 K. The other is a dual-stage GM-type refrigerator, in which the ultimate temperature was 13 K and the cooling capacity was 5 W at 20 K. When cooling and magnetizing tests were carried out using a GdBCO bulk 60 mm in diameter and 20 mm thick, a maximum trapped field of 3.0 T was achieved at 55 K, in the case of the Stirling refrigerator. Moreover, we also studied to improve the efficiency of magnetic flux trapping. Recent upsizing of the diameter and enhancement of the performance of bulk superconductors make PFM difficult, due to a strong magnetic shield. We propose a bulk material with small holes to supply magnetic flux into the bulk efficiently because superconductivity is intentionally lowered in the portion with holes. On the other hand, we are anxious about the flux flow in a high applied field. To investigate the effect of the proposed method, small holes were drilled in a bulk material, and a fundamental experiment was carried out. It was confirmed that the magnetic flux penetrated at a low applied field as compared with the holeless bulk material; moreover, the flux flow was suppressed in a high applied field at a low temperature. Furthermore, we aim to optimize the number, size, and position of small holes.",
keywords = "Flux penetration, Heat generation, Pulsed field magnetization, REBCO bulk, Refrigerator, Trapped field",
author = "Kazuya Yokoyama and Tetsuo Oka",
year = "2018",
month = "1",
day = "1",
language = "English",
isbn = "9781536133417",
pages = "369--385",
booktitle = "High-Temperature Superconductors",
publisher = "Nova Science Publishers, Inc.",
address = "United States",

}

TY - CHAP

T1 - Strong magnetic field generation by superconducting bulk magnets using various types of refrigerators and considering an efficient magnetization

AU - Yokoyama, Kazuya

AU - Oka, Tetsuo

PY - 2018/1/1

Y1 - 2018/1/1

N2 - We are developing several types of superconducting bulk magnets with the goal of their industrial application, and we are studying to improve the magnetic field by pulsedfield magnetization (PFM). It is important to select a suitable refrigerator for cooling a bulk superconductor. This paper investigates magnetizing characteristics when using different refrigerators. The first is a Stirling refrigerator, in which the ultimate temperature was up to 50 K, and the cooling capacity was 10 W at 77 K. The other is a dual-stage GM-type refrigerator, in which the ultimate temperature was 13 K and the cooling capacity was 5 W at 20 K. When cooling and magnetizing tests were carried out using a GdBCO bulk 60 mm in diameter and 20 mm thick, a maximum trapped field of 3.0 T was achieved at 55 K, in the case of the Stirling refrigerator. Moreover, we also studied to improve the efficiency of magnetic flux trapping. Recent upsizing of the diameter and enhancement of the performance of bulk superconductors make PFM difficult, due to a strong magnetic shield. We propose a bulk material with small holes to supply magnetic flux into the bulk efficiently because superconductivity is intentionally lowered in the portion with holes. On the other hand, we are anxious about the flux flow in a high applied field. To investigate the effect of the proposed method, small holes were drilled in a bulk material, and a fundamental experiment was carried out. It was confirmed that the magnetic flux penetrated at a low applied field as compared with the holeless bulk material; moreover, the flux flow was suppressed in a high applied field at a low temperature. Furthermore, we aim to optimize the number, size, and position of small holes.

AB - We are developing several types of superconducting bulk magnets with the goal of their industrial application, and we are studying to improve the magnetic field by pulsedfield magnetization (PFM). It is important to select a suitable refrigerator for cooling a bulk superconductor. This paper investigates magnetizing characteristics when using different refrigerators. The first is a Stirling refrigerator, in which the ultimate temperature was up to 50 K, and the cooling capacity was 10 W at 77 K. The other is a dual-stage GM-type refrigerator, in which the ultimate temperature was 13 K and the cooling capacity was 5 W at 20 K. When cooling and magnetizing tests were carried out using a GdBCO bulk 60 mm in diameter and 20 mm thick, a maximum trapped field of 3.0 T was achieved at 55 K, in the case of the Stirling refrigerator. Moreover, we also studied to improve the efficiency of magnetic flux trapping. Recent upsizing of the diameter and enhancement of the performance of bulk superconductors make PFM difficult, due to a strong magnetic shield. We propose a bulk material with small holes to supply magnetic flux into the bulk efficiently because superconductivity is intentionally lowered in the portion with holes. On the other hand, we are anxious about the flux flow in a high applied field. To investigate the effect of the proposed method, small holes were drilled in a bulk material, and a fundamental experiment was carried out. It was confirmed that the magnetic flux penetrated at a low applied field as compared with the holeless bulk material; moreover, the flux flow was suppressed in a high applied field at a low temperature. Furthermore, we aim to optimize the number, size, and position of small holes.

KW - Flux penetration

KW - Heat generation

KW - Pulsed field magnetization

KW - REBCO bulk

KW - Refrigerator

KW - Trapped field

UR - http://www.scopus.com/inward/record.url?scp=85048426706&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85048426706&partnerID=8YFLogxK

M3 - Chapter

AN - SCOPUS:85048426706

SN - 9781536133417

SP - 369

EP - 385

BT - High-Temperature Superconductors

PB - Nova Science Publishers, Inc.

ER -