Superconductivity - Part 7: Electronic characteristic measurements - Surface resistance of superconductors at microwave frequencies

This part of IEC 61788 describes measurement of the surface resistance of superconductors at microwave frequencies by the standard two-resonator method. The object of measurement is the temperature dependence of Rs at the resonant frequency. The applicable measurement range of surface resistances for this method is as follows: - Frequency: 8 GHz < f < 30 GHz - Measurement resolution: 0,01 milliohm at 10 GHz.

Supraleitfähigkeit - Teil 7: Charakteristische elektronische Messungen - Oberflächenwiderstand von Supraleitern bei Frequenzen im Mikrowellenbereich

Supraconductivité - Partie 7: Mesures des caractéristiques électroniques - Résistance de surface des supraconducteurs aux hyperfréquences

Superprevodnost - 7. del: Meritve elektronskih lastnosti - Površinska upornost superprevodnikov pri mikrovalovnih frekvencah (IEC 61788-7:2006)

General Information

Status
Published
Publication Date
11-Dec-2006
Technical Committee
Drafting Committee
Parallel Committee
Current Stage
6060 - Document made available
Due Date
12-Dec-2006
Completion Date
12-Dec-2006

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SLOVENSKI SIST EN 61788-7:2007
STANDARD
marec 2007
Superprevodnost – 7. del: Meritve elektronskih lastnosti – Površinska
upornost superprevodnikov pri mikrovalovnih frekvencah (IEC 61788-7:2006)
Superconductivity - Part 7: Electronic characteristic measurements - Surface
resistance of superconductors at microwave frequencies (IEC 61788-7:2006)
ICS 17.220.20; 29.050 Referenčna številka
SIST EN 61788-7:2007(en)

© Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno

---------------------- Page: 1 ----------------------
EUROPEAN STANDARD
EN 61788-7
NORME EUROPÉENNE
December 2006
EUROPÄISCHE NORM
ICS 17.220; 29.050 Supersedes EN 61788-7:2002
English version
Superconductivity
Part 7: Electronic characteristic measurements -
Surface resistance of superconductors at microwave frequencies
(IEC 61788-7:2006)
Supraconductivité Supraleitfähigkeit
Partie 7: Mesures des caractéristiques Teil 7: Charakteristische elektronische
électroniques - Messungen -
Résistance de surface des Oberflächenwiderstand von Supraleitern
supraconducteurs aux hyperfréquences bei Frequenzen im Mikrowellenbereich
(CEI 61788-7:2006) (IEC 61788-7:2006)

This European Standard was approved by CENELEC on 2006-11-01. CENELEC members are bound to comply

with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard

the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on

application to the Central Secretariat or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other

language made by translation under the responsibility of a CENELEC member into its own language and notified

to the Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Cyprus, the Czech

Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,

Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,

Sweden, Switzerland and the United Kingdom.
CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
Central Secretariat: rue de Stassart 35, B - 1050 Brussels

© 2006 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

Ref. No. EN 61788-7:2006 E
---------------------- Page: 2 ----------------------
EN 61788-7:2006 - 2 -
Foreword

The text of document 90/193/FDIS, future edition 2 of IEC 61788-7, prepared by IEC TC 90,

Superconductivity, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as

EN 61788-7 on 2006-11-01.
This European Standard supersedes EN 61788-7:2002.
Examples of technical changes made are:

– closed type resonators are recommended from the viewpoint of the stable measurements;

– uniaxial-anisotropic characteristics of sapphire rods are taken into consideration for designing the size

of the sapphire rods;

– recommended measurement frequency of 18 GHz and 22 GHz are added to 12 GHz described in

EN 61788-7:2002.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
(dop) 2007-08-01
national standard or by endorsement
– latest date by which the national standards conflicting
(dow) 2009-11-01
with the EN have to be withdrawn
Annex ZA has been added by CENELEC.
__________
Endorsement notice

The text of the International Standard IEC 61788-7:2006 was approved by CENELEC as a European

Standard without any modification.
__________
---------------------- Page: 3 ----------------------
- 3 - EN 61788-7:2006
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

The following referenced documents are indispensable for the application of this document. For dated

references, only the edition cited applies. For undated references, the latest edition of the referenced

document (including any amendments) applies.

NOTE When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD

applies.
Publication Year Title EN/HD Year
IEC 60050-815 - International Electrotechnical Vocabulary - -
(IEV)
Part 815: Superconductivity
Undated reference.
---------------------- Page: 4 ----------------------
INTERNATIONAL IEC
STANDARD 61788-7
Second edition
2006-10
Superconductivity –
Part 7:
Electronic characteristic measurements –
Surface resistance of superconductors at
microwave frequencies
© IEC 2006 ⎯ Copyright - all rights reserved

No part of this publication may be reproduced or utilized in any form or by any means, electronic or

mechanical, including photocopying and microfilm, without permission in writing from the publisher.

International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland

Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch Web: www.iec.ch

PRICE CODE
Commission Electrotechnique Internationale V
International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
For price, see current catalogue
---------------------- Page: 5 ----------------------
– 2 – 61788-7 © IEC:2006(E)
CONTENTS

FOREWORD...........................................................................................................................4

INTRODUCTION.....................................................................................................................6

1 Scope...............................................................................................................................7

2 Normative references .......................................................................................................7

3 Terms and definitions .......................................................................................................7

4 Requirements ...................................................................................................................7

5 Apparatus.........................................................................................................................8

5.1 Measurement system ..............................................................................................8

5.2 Measurement apparatus for R ................................................................................9

5.3 Dielectric rods .......................................................................................................11

6 Measurement procedure.................................................................................................12

6.1 Specimen preparation ...........................................................................................12

6.2 Set-up ...................................................................................................................12

6.3 Measurement of reference level ............................................................................12

6.4 Measurement of the frequency response of resonators..........................................13

6.5 Determination of surface resistance of the superconductor and ε’ and tan δ

of the standard sapphire rods ................................................................................15

7 Precision and accuracy of the test method......................................................................16

7.1 Surface resistance ................................................................................................16

7.2 Temperature..........................................................................................................17

7.3 Specimen and holder support structure .................................................................17

7.4 Specimen protection..............................................................................................18

8 Test report......................................................................................................................18

8.1 Identification of test specimen ...............................................................................18

8.2 Report of R values ...............................................................................................18

8.3 Report of test conditions........................................................................................18

Annex A (informative) Additional information relating to Clauses 1 to 8................................19

Bibliography..........................................................................................................................32

Figure 1 – Schematic diagram of measurement system for temperature dependence of

R using a cryocooler .............................................................................................................8

Figure 2 – Typical measurement apparatus for R ................................................................10

Figure 3 – Insertion attenuation IA, resonant frequency f and half power bandwidth Δf,

measured at T Kelvin ............................................................................................................13

Figure 4 – Reflection scattering parameters (S and S ) ....................................................15

11 22

Figure 5 – Term definitions in Table 4...................................................................................17

Figure A.1 – Schematic configuration of several measurement methods for the surface

resistance .............................................................................................................................20

Figure A.2 – Configuration of a cylindrical dielectric rod resonator short-circuited at

both ends by two parallel superconductor films deposited on dielectric substrates ................22

Figure A.3 – Computed results of the u-v and W-v relations for TE mode.........................23

01p

Figure A.4 – Configuration of standard dielectric rods for measurement of R and tan δ .......24

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61788-7 © IEC:2006(E) – 3 –

Figure A.5 – Three types of dielectric resonators ..................................................................24

Figure A.6 – Mode chart to design TE resonator short-circuited at both ends by
011

parallel superconductor films [11] .........................................................................................27

Figure A.7 – Mode chart to design TE resonator short-circuited at both ends by
013

parallel superconductor films [11] .........................................................................................28

Figure A.8 – Mode chart for TE closed-type resonator......................................................29

011

Figure A.9 – Mode chart for TE closed-type resonator......................................................30

013

Table 1 – Typical dimensions of pairs of standard sapphire rods for 12 GHz, 18 GHz

and 22 GHz ..........................................................................................................................11

Table 2 – Dimensions of superconductor film for 12 GHz, 18 GHz, and 22 GHz ....................12

Table 3 – Specifications on vector network analyzer .............................................................16

Table 4 – Specifications on sapphire rods.............................................................................16

---------------------- Page: 7 ----------------------
– 4 – 61788-7 © IEC:2006(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SUPERCONDUCTIVITY –
Part 7: Electronic characteristic measurements –
Surface resistance of superconductors
at microwave frequencies
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

all national electrotechnical committees (IEC National Committees). The object of IEC is to promote

international co-operation on all questions concerning standardization in the electrical and electronic fields. To

this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,

Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC

Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested

in the subject dealt with may participate in this preparatory work. International, governmental and non-

governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely

with the International Organization for Standardization (ISO) in accordance with conditions determined by

agreement between the two organizations.

2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international

consensus of opinion on the relevant subjects since each technical committee has representation from all

interested IEC National Committees.

3) IEC Publications have the form of recommendations for international use and are accepted by IEC National

Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC

Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any

misinterpretation by any end user.

4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications

transparently to the maximum extent possible in their national and regional publications. Any divergence

between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in

the latter.

5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any

equipment declared to be in conformity with an IEC Publication.

6) All users should ensure that they have the latest edition of this publication.

7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and

members of its technical committees and IEC National Committees for any personal injury, property damage or

other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and

expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC

Publications.

8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is

indispensable for the correct application of this publication.

9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of

patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

International Standard IEC 61788-7 has been prepared by IEC technical committee 90:

Superconductivity.

This second edition cancels and replaces the first edition, published in 2002, of which it

constitutes a technical revision. Examples of technical changes made are: 1) closed type

resonators are recommended from the viewpoint of the stable measurements, 2) uniaxial-

anisotropic characteristics of sapphire rods are taken into consideration for designing the size

of the sapphire rods, and 3) recommended measurement frequency of 18 GHz and 22 GHz

are added to 12 GHz described in the first edition.
The text of this standard is based on the following documents:
FDIS Report on voting
90/193/FDIS 90/198/RVD
---------------------- Page: 8 ----------------------
61788-7 © IEC:2006(E) – 5 –

Full information on the voting for the approval of this standard can be found in the report on

voting indicated in the above table.

This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

IEC 61788 consists of the following parts, under the general title Superconductivity:

Part 1: Critical current measurement – DC critical current of Cu/Nb-Ti composite super-

conductors

Part 2: Critical current measurement – DC critical current of Nb Sn composite super-

conductors

Part 3: Critical current measurement – DC critical current of Ag- and/or Ag alloy-sheathed

Bi-2212 and Bi-2223 oxide superconductors

Part 4: Residual resistance ratio measurement – Residual resistance ratio of Nb-Ti

composite superconductors

Part 5: Matrix to superconductor volume ratio measurement – Copper to superconductor

volume ratio of Cu/Nb-Ti composite superconductors

Part 6: Mechanical properties measurement – Room temperature tensile test of Cu/Nb-Ti

composite superconductors

Part 7: Electronic characteristic measurements – Surface resistance of superconductors at

microwave frequencies
Part 8: AC loss measurements – Total AC loss measurement of Cu/Nb-Ti composite
superconducting wires exposed to a transverse alternating magnetic field by a
pickup coil method

Part 9: Measurements for bulk high temperature superconductors – Trapped flux density of

large grain oxide superconductors

Part 10: Critical temperature measurement – Critical temperature of Nb-Ti, Nb Sn, and

Bi-system oxide composite superconductors by a resistance method

Part 11: Residual resistance ratio measurement – Residual resistance ratio of Nb Sn

composite superconductors

Part 12: Matrix to superconductor volume ratio measurement – Copper to non-copper

volume ratio of Nb Sn composite superconducting wires

Part 13: AC loss measurements – Magnetometer methods for hysteresis loss in Cu/Nb-Ti

multifilamentary composites

The committee has decided that the contents of this publication will remain unchanged until

the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in

the data related to the specific publication. At this date, the publication will be

• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.
---------------------- Page: 9 ----------------------
– 6 – 61788-7 © IEC:2006(E)
INTRODUCTION

Since the discovery of some Perovskite-type Cu-containing oxides, extensive research and

development (R & D) work on high-temperature oxide superconductors has been, and is being,

made worldwide, and its application to high-field magnet machines, low-loss power

transmission, electronics and many other technologies is in progress.

In various fields of electronics, especially in telecommunication fields, microwave passive

devices such as filters using oxide superconductors are being developed and are undergoing

on-site testing [1,2] .

Superconductor materials for microwave resonators, filters, antenna and delay lines have the

advantage of very low loss characteristics. Knowledge of this parameter is of primary

importance for the development of new materials on the supplier side and for the design of

superconductor microwave components on the customer side. The parameters of

superconductor materials needed for the design of microwave low loss components are the

surface resistance R and the temperature dependence of the surface resistance.

Recent advances in high Tc superconductor (HTS) thin films with R several orders of

magnitude lower than that of normal metals have increased the need for a reliable

characterization technique to measure this property [3,4]. Traditionally, the R of Nb or any

other low temperature superconducting material was measured by first fabricating an entire

three dimensional resonant cavity and then measuring its Q-value. The R could be calculated

by solving the EM field distribution inside the cavity. Another technique involves placing a

small sample inside a larger cavity. This technique has many forms but usually involves the

uncertainty introduced by extracting the loss contribution due to the HTS films from the

experimentally measured total loss of the cavity.

The best HTS samples are epitaxial films grown on flat crystalline substrates and no high

quality films have been grown on any curved surface so far. What is needed is a technique

that: can use these small flat samples; requires no sample preparation; does not damage or

change the film; is highly repeatable; has great sensitivity (down to 1/1 000 the R of copper);

has great dynamic range (up to the R of copper); can reach high internal powers with only

modest input powers; and has broad temperature coverage (4,2 K to 150 K).

The dielectric resonator method is selected among several methods [5,6,7] to determine the

surface resistance at microwave frequencies because it is considered to be the most popular

and practical at present. Especially, the sapphire resonator is an excellent tool for measuring

the R of HTS materials [8,9].

The test method given in this standard can be also applied to other superconductor bulk

plates including low Tc material.

This standard is intended to provide an appropriate and agreeable technical base for the time

being to engineers working in the fields of electronics and superconductivity technology.

The test method covered in this standard is based on the VAMAS (Versailles Project on

Advanced Materials and Standards) pre-standardization work on the thin film properties of

superconductors.
___________
Figures in square brackets refer to the Bibliography.
---------------------- Page: 10 ----------------------
61788-7 © IEC:2006(E) – 7 –
SUPERCONDUCTIVITY –
Part 7: Electronic characteristic measurements –
Surface resistance of superconductors
at microwave frequencies
1 Scope

This part of IEC 61788 describes measurement of the surface resistance of superconductors

at microwave frequencies by the standard two-resonator method. The object of measurement

is the temperature dependence of R at the resonant frequency.

The applicable measurement range of surface resistances for this method is as follows:

– Frequency: 8 GHz < f < 30 GHz
– Measurement resolution: 0,01 mΩ at 10 GHz

The surface resistance data at the measured frequency, and that scaled to 10 GHz, assuming

the f rule for comparison, are reported.
2 Normative references

The following referenced documents are indispensable for the application of this document.

For dated references, only the edition cited applies. For undated references, the latest edition

of the referenced document (including any amendments) applies.

IEC 60050-815, International Electrotechnical Vocabulary (IEV) – Part 815: Superconductivity

3 Terms and definitions

For the purposes of this document, the terms and definitions given in IEC 60050-815 apply.

In general, surface impedance Z for conductors, including superconductors, is defined as the

ratio of the electric field E to the magnetic field H , tangential to a conductor surface:

t t
Z = E /H = R + jX
s t t s s
where R is the surface resistance and X is the surface reactance.
s s
4 Requirements

The surface resistance R of a superconductor film shall be measured by applying a

microwave signal to a dielectric resonator with the superconductor film specimen and then

measuring the attenuation of the resonator at each frequency. The frequency shall be swept

around the resonant frequency as the centre, and the attenuation–frequency characteristics

shall be recorded to obtain Q-value, which corresponds to the loss.

The target precision of this method is a coefficient of variation (standard deviation divided by

the average of the surface resistance determinations) that is less than 20 % for the

measurement temperature range from 30 K to 80 K.
---------------------- Page: 11 ----------------------
– 8 – 61788-7 © IEC:2006(E)

It is the responsibility of the user of this standard to consult and establish appropriate safety

and health practices and to determine the applicability of regulatory limitations prior to use.

Hazards exist in this type of measurement. The use of a cryogenic system is essential to cool

the superconductors to allow transition into the superconducting state. Direct contact of skin

with cold apparatus components can cause immediate freezing, as can direct contact with a

spilled cryogen. The use of an r.f.-generator is also essential to measure high-frequency

properties of materials. If its power is too high, direct contact to human bodies can cause an

immediate burn.
5 Apparatus
5.1 Measurement system

Figure 1 shows a schematic diagram of the system required for the microwave measurement.

The system consists of a network analyzer system for transmission measurement, a

measurement apparatus, and a thermometer for monitoring the measuring temperature.

An incident power generated from a suitable microwave source such as a synthesized

sweeper is applied to the dielectric resonator fixed in the measurement apparatus. The

transmission characteristics are shown on the display of the network analyzer.
Vector network
analyser
Synthesized
sweeper
Thermometer
S-parameter
test set
Thermal sensor
Measurement apparatus
Cryocooler
IEC 004/02
Figure 1 – Schematic diagram of measurement system
for temperature dependence of R using a cryocooler
The measurement apparatus is fixed in a temperature-controlled cryocooler.

For the measurement of R for superconductor films, a vector network analyzer is recom-

mended. A vector network analyzer has better measurement accuracy than a scalar network

analyzer due to its wide dynamic range.
System interface
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61788-7 © IEC:2006(E) – 9 –
5.2 Measurement apparatus for R

Figure 2 shows a schematic of a typical measurement apparatus (closed type resonator) for

the R of superconductor films deposited on a substrate with a flat surface. The upper

superconductor film is pressed down by a spring, which is made of phosphor bronze. The

plate type spring is recommended to be used for the improvement of measurement accuracy.

This type of spring reduces the friction between the spring and the other part of the apparatus,

and allows the smooth movement of superconductor films due to the thermal expansion of the

dielectric rod. In order to minimize the measurement error, the sapphire rod and the copper

ring shall be set in coaxial.

Two semi-rigid cables for measuring transmission characteristics of the resonator shall be

attached on both sides of the resonator in an axial symmetrical position (φ = 0 and π, where φ

is the rotational angle around the central axis of the sapphire rod). Each of the two semi-rigid

cables shall have a small loop at the ends. The plane of the loop shall be set parallel to that

of the superconductor films in order to suppress the unwanted TM modes. The coupling

mn0

loops shall be carefully checked for cracks in the spot weld joint that may have developed

upon repeated thermal cycling. These cables can move right and left to adjust the insertion

attenuation (IA). In this adjustment, coupling of unwanted cavity modes to the interested

dielectric resonance mode shall be suppressed. Unwanted, parasitic coupling to the other

modes reduces the high Q value of the TE mode resonator. For suppressing the parasitic

coupling, special attention shall be paid to designing high Q resonators. Two other types of

resonators along with the closed type shown in Figure 2 can be used. They are explained in

Clause A.4.
---------------------- Page: 13 ----------------------
– 10 – 61788-7 © IEC:2006(E)
Screw Screws
Hexagonal
head bolt
Phosphor bronze
plate spring
Copper supports
Copper plate
Spot welding
Superconductor film
Copper ring
Small loop
Connector
Semi-rigid
Superconductor film
coaxial cable
Sapphire rod
Copper block
Screws to fix on
a cold stage
IEC 1733/06
Figure 2 – Typical measurement apparatus for R
---------------------- Page: 14 ----------------------
61788-7 © IEC:2006(E) – 11 –

A reference line made of a semi-rigid cable shall be used to measure the full transmission

power level, i.e., the reference level. This cable has a length equal to the sum of the two

cables of the measurement apparatus. The semi-rigid cable with the outer diameter of

1,20 mm is recommended.

In order to minimize the measurement error, two superconductor films shall be set to be

parallel to each other. To ensure that the two superconductor films remain in tight contact with

the ends of the sapphire rod, without any air gap, both of the surfaces of the films and the

ends of the rod shall be cleaned carefully.
5.3 Dielectric rods

Two dielectric rods with the same relative permittivity, ε’, and loss factor, tan δ, preferably cut

from one cylindrical dielectric rod, are required. These two rods, standard dielectric rods, shall

have the same diameter but different heights: one has a height three times longer than the

other.

It is preferable to use standard dielectric rods with low tan δ to achieve the requisite

measurement accuracy on R . Recommended dielectric rods are sapphire rods with tan δ less

than 10 at 77 K. Specifications on the sapphire rods are described in 7.1. In order to

minimize the measurement error in R of the superconductor films, both ends of the sapphire

rods shall be polish
...

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