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Relative contributions of surface and bulk hysteresis to properties of hollow cylinders of type II superconductors
Volume 3’7A, number 2
RELATIVE
PROPERTIES
PHYSICS
CONTRIBUTIONS
OF HOLLOW
LETTERS
8 November 1971
OF SURFACE AND CYLINDERS OF TYPE
BULK HYSTERESIS TO II SUPERCONDUCTORS*
D. G. SCHWEITZER Brookhaven
National Laboratory,
Upton, New York,
USA
Received 24 September 1971
Comparisons of the shielding and field retaining properties of type II hollow cylinders in fields applied externally and in the void can be used to distinghuish surface hysteresis from bulk hysteresis.
a combination of bulk and surface properties. Fig. la shows the variation of internal fields with applied fields for Pb-5 a/o Bi samples of
Recent measurements [l] of the properties of type I hollow cylinders in fields generated in the voids provide new information on the field penetration and flux trapping properties of superconducting hollow cylinders. Some preliminary re-
sults from type II hollow cylinders are reported here comparing this technique with conventional measurements using externally applied fields. The shielding and field trapping properties of hollow cylinders of type II superconductors depend upon whether the hysteresis arises mainly from surface properties or from combinations of surface and bulk hysteresis [2]. When the hysteresis is due mainly to surface properties, the shielding and field trapping properties are insensitive to wall thickness. In this case the field trapping properties are similar when the applied field is generated either inside the void or external to the hollow cylinder. For such materials the bulk behaves like an Abrikosov superconductor and appreciable field gradients do not appear to exist in the bulk. The field trapping appears to be due to surface currents, and scales precisely with applied fields generated either externally or internally. When the hysteresis is due to a combination of surface and bulk properties the low field shielding in externally applied fields is dependent on wall thickness whereas the high field shielding is not. In this case the variation of retained field with externally applied fields is different from the variation of retained field with fields generated in the void. The differences in behavior for the two types of measurements provide a convenient method of distinguishing hysteresis arising from surface properties and hysteresis arising from * This work was performed under the auspices of the U. S. Atomic Energy Commission.
800 600 DENOTES REGION WHER 400 200
-2
8
FACE COMPONENT 0
200
400
6CO
803
1000
IXK)
1400
1600
l8M)2000
Hex, (04
I
I
0
200
400
600
800
I
I
1000
I200 H
a+
I
1400
I
I
I600
(Oe’
Fig. 1. Variation of field in the void (H.) with increasing external field (Hext): a. for Pb-5 afo Bi hollow cylinders
of different wall thickness, b. for V hollow linders of different wall thickness.
cy-
147
Volume
37A. number 2
PHYSICS
LETTERS
1
600-
8 November
(b)
800
o.O.
to’
0.
700
V14.Z°Kj 0.157
600
cm WALL
0.”
500
500 -
1971
0
xi = i i
400-
400 0.417
300-
cm WALL
I.f. INTERNAL 0 1.1. EXTERNAL
FIELD FIELD
l
200 -
0
300
0 0
200 0
100 !l
I,
I
I
I
0
IO
20
30
40
50
60
70
60
90
100
0
170
340
510
660
650
1020
II90
1360
1530
1700
Fig.
2.
I,
I
roe,
,
FIELD FIELD
.
(
I~AlfINTERNAL)
0
IO
20
30
40
H(OellEXTERNAL1
0
217
434
651
665
,
50 1065
,
,
,
,
60
70
60
90
1302
1520
1736
1953
,
,
L
100
I(AJ[INT
y&t
2170
HlOel(E>
RNALJ
Comparison of trapped fields (t.f.) after applying and removing external and internal fields.
different wall thicknesses. Fig. lb shows analogous data for vanadium hollow cylinders. The results demonstrate the differences in behavior discussed above. Fig. 2a and 2b compare the variation of field retained in the void with applied fields generated externally and internally. In the case of the vanadium hollow cylinders the data scale suggesting that the field trapping is due to surface currents in suppert of previous work [2]. *****
148
. 1.1. INTERNAL o 1.f. EXTERNAL
.
In the case of Pb-5 a/o Bi, the two methods yield different results implying that the trapped field distributions in the bulk are different when the fields are applied externally or internally.
References [l] D. G. Schweitzer (1970) 4326. [2] D. G. Schweitzer (1967) 348.
and M. Garber,
Phys. Rev. 1
and M. Garber,
Phys. Rev. 160
RELATIVE
PROPERTIES
PHYSICS
CONTRIBUTIONS
OF HOLLOW
LETTERS
8 November 1971
OF SURFACE AND CYLINDERS OF TYPE
BULK HYSTERESIS TO II SUPERCONDUCTORS*
D. G. SCHWEITZER Brookhaven
National Laboratory,
Upton, New York,
USA
Received 24 September 1971
Comparisons of the shielding and field retaining properties of type II hollow cylinders in fields applied externally and in the void can be used to distinghuish surface hysteresis from bulk hysteresis.
a combination of bulk and surface properties. Fig. la shows the variation of internal fields with applied fields for Pb-5 a/o Bi samples of
Recent measurements [l] of the properties of type I hollow cylinders in fields generated in the voids provide new information on the field penetration and flux trapping properties of superconducting hollow cylinders. Some preliminary re-
sults from type II hollow cylinders are reported here comparing this technique with conventional measurements using externally applied fields. The shielding and field trapping properties of hollow cylinders of type II superconductors depend upon whether the hysteresis arises mainly from surface properties or from combinations of surface and bulk hysteresis [2]. When the hysteresis is due mainly to surface properties, the shielding and field trapping properties are insensitive to wall thickness. In this case the field trapping properties are similar when the applied field is generated either inside the void or external to the hollow cylinder. For such materials the bulk behaves like an Abrikosov superconductor and appreciable field gradients do not appear to exist in the bulk. The field trapping appears to be due to surface currents, and scales precisely with applied fields generated either externally or internally. When the hysteresis is due to a combination of surface and bulk properties the low field shielding in externally applied fields is dependent on wall thickness whereas the high field shielding is not. In this case the variation of retained field with externally applied fields is different from the variation of retained field with fields generated in the void. The differences in behavior for the two types of measurements provide a convenient method of distinguishing hysteresis arising from surface properties and hysteresis arising from * This work was performed under the auspices of the U. S. Atomic Energy Commission.
800 600 DENOTES REGION WHER 400 200
-2
8
FACE COMPONENT 0
200
400
6CO
803
1000
IXK)
1400
1600
l8M)2000
Hex, (04
I
I
0
200
400
600
800
I
I
1000
I200 H
a+
I
1400
I
I
I600
(Oe’
Fig. 1. Variation of field in the void (H.) with increasing external field (Hext): a. for Pb-5 afo Bi hollow cylinders
of different wall thickness, b. for V hollow linders of different wall thickness.
cy-
147
Volume
37A. number 2
PHYSICS
LETTERS
1
600-
8 November
(b)
800
o.O.
to’
0.
700
V14.Z°Kj 0.157
600
cm WALL
0.”
500
500 -
1971
0
xi = i i
400-
400 0.417
300-
cm WALL
I.f. INTERNAL 0 1.1. EXTERNAL
FIELD FIELD
l
200 -
0
300
0 0
200 0
100 !l
I,
I
I
I
0
IO
20
30
40
50
60
70
60
90
100
0
170
340
510
660
650
1020
II90
1360
1530
1700
Fig.
2.
I,
I
roe,
,
FIELD FIELD
.
(
I~AlfINTERNAL)
0
IO
20
30
40
H(OellEXTERNAL1
0
217
434
651
665
,
50 1065
,
,
,
,
60
70
60
90
1302
1520
1736
1953
,
,
L
100
I(AJ[INT
y&t
2170
HlOel(E>
RNALJ
Comparison of trapped fields (t.f.) after applying and removing external and internal fields.
different wall thicknesses. Fig. lb shows analogous data for vanadium hollow cylinders. The results demonstrate the differences in behavior discussed above. Fig. 2a and 2b compare the variation of field retained in the void with applied fields generated externally and internally. In the case of the vanadium hollow cylinders the data scale suggesting that the field trapping is due to surface currents in suppert of previous work [2]. *****
148
. 1.1. INTERNAL o 1.f. EXTERNAL
.
In the case of Pb-5 a/o Bi, the two methods yield different results implying that the trapped field distributions in the bulk are different when the fields are applied externally or internally.
References [l] D. G. Schweitzer (1970) 4326. [2] D. G. Schweitzer (1967) 348.
and M. Garber,
Phys. Rev. 1
and M. Garber,
Phys. Rev. 160