kSIST FprEN IEC 61788-15:2025

SLOVENSKI STANDARD
oSIST prEN IEC 61788-15:2025
01-april-2025
Superprevodnost - 15. del: Meritve elektronskih karakteristik - Lastna površinska
impedanca superprevodnih plasti pri mikrovalovnih frekvencah
Superconductivity - Part 15: Electronic characteristic measurements - Intrinsic surface
impedance of superconductor films at microwave frequencies
Supraleitfähigkeit - Teil 15: Messungen der elektronischen Charakteristik -
Oberflächenimpedanz von Supraleiterschichten bei Mikrowellenfrequenzen
Supraconductivité - Partie 15: Mesures de caractéristiques électroniques - Impédance de
surface intrinsèque de films supraconducteurs aux fréquences micro-ondes
Ta slovenski standard je istoveten z: prEN IEC 61788-15:2025
ICS:
17.220.20 Merjenje električnih in Measurement of electrical
magnetnih veličin and magnetic quantities
29.050 Superprevodnost in prevodni Superconductivity and
materiali conducting materials
oSIST prEN IEC 61788-15:2025 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

oSIST prEN IEC 61788-15:2025
oSIST prEN IEC 61788-15:2025
90/539/CDV
COMMITTEE DRAFT FOR VOTE (CDV)
PROJECT NUMBER:
IEC 61788-15 ED2
DATE OF CIRCULATION: CLOSING DATE FOR VOTING:
2025-01-31 2025-04-25
SUPERSEDES DOCUMENTS:
90/523/CD, 90/534/CC
IEC TC 90 : SUPERCONDUCTIVITY
SECRETARIAT: SECRETARY:
Japan Mr Jun Fujikami
OF INTEREST TO THE FOLLOWING COMMITTEES: HORIZONTAL FUNCTION(S):

ASPECTS CONCERNED:
SUBMITTED FOR CENELEC PARALLEL VOTING NOT SUBMITTED FOR CENELEC PARALLEL VOTING
Attention IEC-CENELEC parallel voting
The attention of IEC National Committees, members of
CENELEC, is drawn to the fact that this Committee Draft
for Vote (CDV) is submitted for parallel voting.
The CENELEC members are invited to vote through the
CENELEC online voting system.
This document is still under study and subject to change. It should not be used for reference purposes.
Recipients of this document are invited to submit, with their comments, notification of any relevant patent rights of
which they are aware and to provide supporting documentation.
Recipients of this document are invited to submit, with their comments, notification of any relevant “In Some
Countries” clauses to be included should this proposal proceed. Recipients are reminded that the CDV stage is
the final stage for submitting ISC clauses. (SEE AC/22/2007 OR NEW GUIDANCE DOC).

TITLE:
Superconductivity - Part 15: Electronic characteristic measurements - Intrinsic surface
impedance of superconductor films at microwave frequencies

PROPOSED STABILITY DATE: 2032
NOTE FROM TC/SC OFFICERS:
electronic file, to make a copy and to print out the content for the sole purpose of preparing National Committee positions.
You may not copy or "mirror" the file or printed version of the document, or any part of it, for any other purpose without
permission in writing from IEC.

oSIST prEN IEC 61788-15:2025
IEC 61788-15 ED2 © IEC 2024 3 90/539/CDV
1 CONTENTS
3 FOREWORD . 5
4 INTRODUCTION . 7
5 1 Scope . 8
6 2 Normative references . 8
7 3 Terms and definitions . 8
8 4 Requirements . 9
9 5 Apparatus . 9
10 5.1 Measurement equipment . 9
11 5.2 Measurement apparatus . 10
12 5.3 Dielectric rods . 14
13 5.4 Superconductor films and copper cavity . 15
14 6 Measurement procedure . 15
15 6.1 Set-up . 15
16 6.2 Measurement of the reference level. 15
17 6.3 Measurement of the R of oxygen-free high conductivity copper . 16
S
18 6.4 Determination of the R of superconductor films and tan δ of standard
Se
19 dielectric rods . 19
20 6.5 Determination of the penetration depth . 20
21 6.6 Determination of the intrinsic surface impedance . 21
22 7 Uncertainty of the test method . 21
23 7.1 Measurement of unloaded quality factor . 21
24 7.2 Measurement of loss tangent. 22
25 7.3 Temperature . 22
26 7.4 Specimen and holder support structure . 23
27 7.5 Uncertainty in the intrinsic surface impedance . 23
28 Test Report . 23
29 8.1 Identification of test specimen . 23
30 8.2 Report of the Z values . 23
S
31 8.3 Report of the test conditions . 23
Annex A (informative)  Additional information relating to clauses 1 to 8 . 24
33 A.1 Concerning the Scope . 24
34 A.2 Requirements . 25
35 A.3 Theory and the measurement procedure for the intrinsic surface impedance . 26
36 Theoretical relation between the Z and the Z [14] . 26
A.3.1 S Se
37 A.3.2 Calculation of the geometrical factors [22] . 30
38 A.4 Dimensions of the standard sapphire rod . 32
39 A.5 Dimensions of the closed type resonators . 33
40 A.6 Test results for type A and type B sapphire resonators . 33
41 Bibliography . 52
43 Figure 1 – Schematic diagram for the measurement equipment for the intrinsic ZS of
HTS films at cryogenic temperatures . 11
45 Figure 2 – Schematic diagram of a dielectric resonator with a switch for thermal
46 connection . 11
47 Figure 3 – Typical dielectric resonator with a movable top plate . 12
48 Figure 4 – Switch block for thermal connection . 13
49 Figure 5 – Dielectric resonator assembled with a switch block for thermal connection . 14

oSIST prEN IEC 61788-15:2025
90/539/CDV 4 IEC 61788-15 ED2 © IEC 2024
50 Figure 6 – A typical resonance peak. Insertion attenuation IA, resonant frequency f0

51 and half power bandwidth ∆f are defined . 17
3dB
52 Figure 7 – Reflection scattering parameters S11 and S22 . 18
53 Figure 8 – Definitions for terms in Table 5 . 22
54 Figure A.1 - Schematic diagram for the measurement system . 24
55 Figure A.2 – A motion stage using step motors . 25
56 Figure A.3 – Cross-sectional view of a dielectric resonator . 26
57 Figure A.4 – A diagram for simplified cross-sectional view of a dielectric resonator . 30
58 Figure A.5 – Mode chart for type A sapphire resonator with a cavity diameter of 12 mm . 33
59 Figure A.6 – Frequency response of type A sapphire resonator . 34
60 Figure A.7 – QU versus temperature for the TE021 and the TE012 modes of type A
61 sapphire resonator with 360 nm-thick YBCO films . 34
62 Figure A.8 – The resonant frequency f versus temperature for the TE021 and TE012
63 modes of type A sapphire resonator with 360 nm-thick YBCO films . 35

64 Figure A.9 – The temperature dependence of the RSe of YBCO films with the
65 thicknesses of 70 nm to 360 nm measured at ~40 GHz . 35
66 Figure A.10 – The temperature dependence of ∆λ for the YBCO films with the
e
67 thicknesses of 70 nm and 360 nm measured at ~40 GHz . 36
68 Figure A.11 – The penetration depths λ of the 360 nm-thick YBCO film measured at
69 10 kHz using the mutual inductance method and at ~40 GHz using type A sapphire
70 resonator . 36
71 Figure A.12 – The temperature dependence of the RS of YBCO films with the
72 thicknesses of 70 nm to 360 nm measured at ~40 GHz . 37
73 Figure A.14 – Frequency response of type B sapphire resonator . 39

74 Figure A.15 – The temperature dependence of the R for the 300 nm-thick YBCO films
Se
75 measured at ~38 GHz Inset-The tan δ of the sapphire rod used for the measurements . 39
76 Figure A.16 – The temperature dependence of ∆λ for the 300 nm-thick YBCO film
e
77 measured at ~38 GHz Inset-The penetration depths λ of the 300 nm-thick YBCO film
78 measured at ~38 GHz using type B sapphire resonator . 40
79 Figure A.17 – The σ vs. temperature data for the 300 nm-thick YBCO films measured
80 at ~38 GHz Inset-The σ vs. temperature data for the same YBCO films at ~38 GHz . 40
81 Figure A.18 – The R vs. temperature data for the 300 nm-thick YBCO films measured
S
82 at ~38 GHz Inset- The XS for the same YBCO films at ~38 GHz . 40
84 Table 1 – Typical dimensions of a sapphire rod . 15
85 Table 2 – Typical dimensions of OFHC cavities and HTS films . 15
86 Table 3 – Geometrical factors and filling factors calculated for the standard sapphire
87 resonators . 18
88 Table 4 – Specifications of Vector Network Analyzer . 22
89 Table 5 – Type B uncertainty for the specifications on the sapphire rod . 22
oSIST prEN IEC 61788-15:2025
IEC 61788-15 ED2 © IEC 2024 5 90/539/CDV
92 INTERNATIONAL ELECTROTECHNICAL COMMISSION
93 __________
95 SUPERCONDUCTIVITY –
97 Part 15: Electronic characteristic measurements –
98 Intrinsic surface impedance of superconductor films at microwave
99 frequencies
102 FOREWORD
103 1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
104 all national electrotechnical committees (IEC National Committees). The object of the IEC is to promote
105 international co-operation on all questions concerning standardization in the electrical and electronic fields. To
106 this end and in addition to other activities, the IEC publishes International Standards. Their preparation is
107 entrusted to technical committees; any IEC National Committee interested in the subject dealt with may
108 participate in this preparatory work. International, governmental and non-governmental organizations liaising with
109 the IEC also participate in this preparation. The IEC collaborates closely with the International Organization for
110 Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.
111 2) The formal decisions or agreements of the IEC on technical matters express, as nearly as possible, an
112 international consensus of opinion on the relevant subjects since each technical committee has representation
113 from all interested National Committees.
114 3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
115 Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
116 Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
117 misinterpretation by any end user.
118 4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
119 transparently to the maximum extent possible in their national and regional publications. Any divergence between
120 any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter.
121 5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
122 assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
123 services carried out by independent certification bodies.
124 6) All users should ensure that they have the latest edition of this publication.
125 7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
126 members of its technical committees and IEC National Committees for any personal injury, property damage or
127 other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
128 expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC Publications.
129 8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
130 indispensable for the correct application of this publication.
131 9) IEC draws attention is drawn to the possibility that the implementation of the document may involve the use of a
132 patent. IEC takes no position concerning the evidence, validity or applicability of any claimed patent rights in
133 respect thereof. As of the date of publication of this document, IEC had not received notice of a patent, which
134 may be required to implement this document. However, implementers are cautioned that this may not represent
135 the latest information, which may be obtained from the patent database available at http://patents.iec.ch and/or
136 www.iso.org/patents. IEC shall not be held responsible for identifying any or all such patent rights.
137 International Standard IEC 61788-15 has been prepared by IEC technical committee 90:
138 Superconductivity.
139 This second edition cancels and replaces the first edition published in 2011. This edition
140 constitutes a technical revision.
141 This edition includes the following significant technical changes with respect to the previous
142 edition
144 a) Iinformative Annex B, combined relative standard uncertainty in the intrinsic surface
145 impedance is added;
146 b) The terms, ‘precision and accuracy’, are replaced with uncertainty;
147 c) Results from a round robin test are added.
149 The text of this standard is based on the following documents:
FDIS Report on voting
oSIST prEN IEC 61788-15:2025
90/539/CDV 6 IEC 61788-15 ED2 © IEC 2024
90/XXX/FDIS 90/XXX/RVD
151 Full information on the voting for the approval of this standard can be found in the report on voting indicated in the
152 above table.
153 The language used for the development of this international standard is English.
154 This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in accordance with ISO/IEC
155 Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available at www.iec.ch/members_experts/refdocs. The
156 main document types developed by IEC are described in greater detail at www.iec.ch/standardsdev/publications.
157 The committee has decided that the contents of this amendment and the base publication will remain unchanged
158 until the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data related to the specific
159 document. At this date, the publication will be
160 • reconfirmed,
161 • withdrawn,
162 • replaced by a revised edition, or
163 • amended.
oSIST prEN IEC 61788-15:2025
IEC 61788-15 ED2 © IEC 2024 7 90/539/CDV
166 INTRODUCTION
167 Since the discovery of high T superconductors (HTS), extensive researches have been
C
168 performed worldwide on electronic applications and large-scale applications with HTS filter
169 Cu O (YBCO) having already been commercialized [1].
subsystems based on YBa2 3 7-δ
170 Merits of using HTS films for microwave devices such as resonators, filters, antennas, delay
171 lines, etc., include i) microwave losses from HTS films could be extremely low and ii) no signal
172 dispersion on transmission lines made of HTS films due to extremely low intrinsic surface
173 resistance (R ) [2] and frequency-independent penetration depth (λ) of HTS films, respectively.
S
174 In this regard, when it comes to designing of HTS-based microwave devices, it is important to
175 measure the intrinsic surface impedance (ZS) of HTS films with ZS = RS + jXS and XS = ωμλ
176 (Here ω and μ denote the angular frequency and the permeability of vacuum, respectively,
177 XS, the intrinsic surface reactance, and XS = ωμλ is valid at temperatures not too close to
178 the critical temperature T of HTS films).
C
179 Various reports have been made on measuring the RS of HTS films at microwave frequencies
180 with the typical R of HTS films as low as 1/100 - 1/50 of that of oxygen-free high-purity copper
S
181 (OFHC) at 77 K and 10 GHz. The RS of conventional superconductors such as niobium (Nb)
182 could be easily measured by using Nb cavities by converting the resonator quality factor (Q) to
183 the RS of Nb. However, such conventional measurement method could no longer be applied to
184 HTS films grown on dielectric substrates, with which it is basically impossible to make all-HTS
185 cavities. Instead, for measuring the RS of HTS films, several other methods have been useful,
186 which include microstrip resonator method [3], coplanar microstrip resonator method [4],
187 parallel plate resonator method [5] and dielectric resonator method [7-11]. Among the stated
188 methods, the dielectric resonator method has been very useful due to the fact that the method
189 enables to measure the microwave surface resistance in a non-invasive way and with accuracy.
190 In 2002, International Electrotechnical Commission (IEC) published the dielectric resonator
191 method as a measurement standard [12].
192 The test method given in this standard enables to measure not only the RS but also the XS of
193 HTS films regardless of the film’s thickness by using single sapphire resonator, which differs
194 from the existing IEC standard (IEC 61788-7:2020) that is limited to measure the surface
195 resistance of superconductor films having the thicknesses of more than 3λ at the measured
196 temperature by using two sapphire resonators. In fact, the measured surface resistances of
197 HTS films with different thicknesses of less than 3λ mean effective values instead of intrinsic
198 values, which cannot be used for directly comparing the microwave properties of HTS films
199 among one another [13, 14]. Use of single sapphire resonator as suggested in this standard
200 also enables to reduce uncertainty in the measured surface resistance that might result from
201 using two sapphire resonators with sapphire rods of different quality.
202 The test method given in this standard can also be applied to HTS coated conductors, HTS
203 bulks and other superconductors having established models for the penetration depth.
204 This standard is intended to provide an appropriate and agreeable technical base for the time
205 being to engineers working in the fields of electronics and superconductivity technology.
206 The test method covered in this standard has been discussed at the VAMAS (Versailles Project
207 on Advanced Materials and Standards) TWA-16 meeting.
oSIST prEN IEC 61788-15:2025
90/539/CDV 8 IEC 61788-15 ED2 © IEC 2024
212 SUPERCONDUCTIVITY –
214 Part 15: Electronic characteristic measurements – Intrinsic surface
215 impedance of superconductor films at microwave frequencies
217 1 Scope
218 This part of IEC 61788 describes measurements of the intrinsic surface impedance (Z ) of HTS
S
219 films at microwave frequencies by a modified two-resonance mode dielectric resonator method
220 [14, 15]. The object of measurement is to obtain the temperature dependence of the intrinsic
221 surface impedance, ZS, at the resonant frequency f0.
222 The frequency and thickness range and the measurement resolution for the Z of HTS films are
S
223 as follows:
224 − frequency: Up to 40 GHz;
225 − film thickness: Greater than 50 nm;
226 − measurement resolution: 0,01 mΩ at 10 GHz.
227 The ZS data at the measured frequency, and that scaled to 10 GHz, assuming the f rule for the
228 intrinsic surface resistance, R (f < 40 GHz), and the f rule for the intrinsic surface reactance,
S
229 XS, for comparison, shall be reported.
230 2 Normative references
231 The following referenced documents are indispensable for the application of this document. For
232 dated references, only the edition cited applies. For undated references, the latest edition of
233 the referenced document (including any amendments) applies.
234 IEC 60050-815:2000, International Electrotechnical Vocabulary – Part 815: Superconductivity
235 IEC 61788-15:2011, Superconductivity – Part 15: Electronic characteristic measurements –
236 Intrinsic surface impedance of superconductor films at microwave frequencies
237 IEC 61788-7:2020, Superconductivity – Part 7: Electronic characteristic measurements –
238 Surface resistance of high-temperature superconductors at microwave frequencies
239 3 Terms and definitions
240 For the purposes of this standard, the definitions given in IEC 60050-815 apply.
241 3.1
242 Surface impedance
243 (see IEC 60050-815:2000, 815-04-62)
244 3.2
245 Intrinsic surface impedance
246 In general, for conductors (or superconductors) having the thicknesses sufficiently greater than
247 the skin depth (or the penetration depth) of electromagnetic fields, ZS is defined as the ratio of
248 the tangential component of the electric field (Et) and that of the magnetic field (Ht) at a
249 conductor or a superconductor surface:
250 ZS = Et/Ht = RS + jXS.                            (1)
251 Here R denotes the intrinsic surface resistance and X is the intrinsic surface reactance if the
S S
252 thickness of the conductor (or the superconductor) under test is sufficiently greater than the
253 penetration depth of electromagnetic fields. In this case, Z is expressed by
S
oSIST prEN IEC 61788-15:2025
IEC 61788-15 ED2 © IEC 2024 9 90/539/CDV
255 with ε and µ denoting the permittivity and the permeability of the conductor (or the
256 superconductor) under test, respectively, µ , the permeability of vacuum, σ (= σ1 - jσ2), the
257 conductivity of the conductor (or the superconductor), and ω, the measured angular frequency.
258 σ is real for normal conductors with σ = 0 and complex for superconductors in the
259 superconducting state .
260 3.3
261 Effective surface impedance
262 If the thickness of the conductor (or the superconductor) under test is not sufficiently greater
263 than the penetration depth of electromagnetic fields, ZS as defined by Equation (1) in 3.2
264 becomes significantly different from that defined by Equation (2) in 3.2. In this case, Z as
S
265 defined by Equation (1) becomes the effective surface impedance, ZSe, with
266 Z = E /H = R + jX .                          (3)
Se t t Se Se
267 Here RSe denotes the effective surface resistance and XSe is the effective surface reactance.
268 4 Requirements
269 The ZS of HTS films shall be measured by applying a microwave signal to a dielectric resonator
270 with the superconductor specimen and then measuring the attenuation of the resonator at each
271 frequency. The frequency shall be swept around the resonant frequency as the centre, and the
272 attenuation - frequency characteristics as well as the scattering parameters shall be recorded
273 to obtain the Q-value, which corresponds to the loss.
274 The target relative uncertainty of this method is less than 20 % at temperatures of 30 K to 60
275 K.
276 It is the responsibility of the user of this standard to consult and establish safety and health
277 practices and to determine the applicability of regulatory limitations prior to use.
278 Hazards exist in this type of measurement. The use of a cryogenic system is essential to cool
279 the superconductors to allow transition into the superconducting state. Direct contact of skin
280 with cold apparatus components can cause immediate freezing, as can direct contact with a
281 spilled cryogen. The use of an r.f.-generator is also essential to measure high-frequency
282 properties of materials. If its power is too high, direct exposure to human bodies can cause an
283 immediate burn.
284 5 Apparatus
285 5.1 Measurement equipment
286 Figure 1 shows a schematic diagram of the equipment required for the microwave measurement.
287 The equipment consists of a network analyzer system for transmission measurements, a
288 measurement apparatus, and thermometers for monitoring the temperature of HTS films under
289 test.
290 An incident power generated from a suitable microwave source such as a synthesized sweeper
291 is applied to the dielectric resonator fixed in the measurement apparatus. The transmission
292 characteristics are shown on the display of the network analyzer.
—————————
σ is a parameter associated with the appearance of Cooper pairs in superconductors at temperatures below the critical
temperature.
oSIST prEN IEC 61788-15:2025
90/539/CDV 10 IEC 61788-15 ED2 © IEC 2024
293 The measurement apparatus is fixed in a temperature-controlled cryocooler. For the penetration
294 depth measurements, vibrations from the cryocooler should be dampened by using dampers
295 between the vacuum chamber and the cryocooler.
296 For measuring the Z of HTS films, a vector network analyzer is recommended because it has
S
297 better measurement accuracy than a scalar network analyzer due to its wider dynamic range.
298 5.2 Measurement apparatus
299 Figure 2 shows a schematic diagram of a typical measurement apparatus for the ZS of HTS
300 films deposited on a substrate with a flat surface. The lower HTS film is pressed down by a
301 spring, which is made of beryllium copper. Use of a plate type spring is recommended for the
302 improvement of measurement uncertainty. This type of spring reduces the friction between the
303 spring and the other part of the apparatus and enables smooth motion of HTS films in the course
304 of thermal expansion/contraction of the dielectric-loaded cavity. The upper HTS film is glued to
305 the Cu plate at the top using adhesives with good thermal conductivity.
306 The R is measured with the upper HTS film being in contact with the top of the Cu cavity.
Se
307 During measurements of the RSe, the whole resonator is first cooled down to the lowest
308 temperature with the cryocooler turned on and then warmed up to higher temperatures with the
309 cryocooler turned off. Meanwhile, the XSe is measured with a small gap between the upper HTS
310 film and the top of the Cu cavity. The gap distance shall be set to a value predetermined at the
311 room temperature by using either a micrometer or a step motor connected to the upper
312 superconductor film through a Teflon rod. The real gap distances would be a little longer at
313 cryogenic temperatures than the corresponding predetermined ones due to thermal contraction
314 of the Teflon rod. The gap distance should be small enough not to cause significant radiation
315 loss and large enough to enable control of the temperature of the upper superconductor film.
316 More detailed descriptions on a dielectric resonator with a movable top plate, a switch block for
317 thermal connection, and the dielectric resonator assembled with the switch block are given in
318 Figures 3 to 5, respectively. Procedures for controlling the temperature of the upper HTS film
319 for measurements of the XS are described in 6.6.
320 Each of the two semi-rigid cables shall have a small loop at the end as shown in Figure 3. The loop,
321 shaped like a semicircle, is affixed to the cross-sectional part of the outer conductor via soldering
322 at its terminal point. The plane of the loop shall be set parallel to that of the HTS films in order to
323 suppress the unwanted TMmn0 modes. The coupling loops shall be carefully checked prior to the
324 measurements to keep the good coupling conditions. For measuring the Q values as a function of
325 temperature, these cables can be moved to the right or to the left to maintain the insertion
326 attenuation (IA) slightly higher than 20 dB at the lowest temperature, with the vertical position of
327 each loop fixed in the middle of the sapphire rod. The distance between the loop and the sapphire
328 rod should be adjusted to a smaller value if the resonant signal gets too noisy at higher temperatures.
329 In this adjustment, coupling of unwanted cavity modes to the interested dielectric resonance mode
330 shall be suppressed. Unwanted, parasitic coupling to the other modes not only reduces the high-Q
331 value of the TE mode resonator but also increases uncertainty in the measured resonant frequency
332 of the TE mode resonator, making it difficult to measure changes in the resonant frequency vs.
333 temperature data with accuracy. For collecting the temperature dependence of the resonant
334 frequency data, the distance between the loop and the sapphire rod should not be changed during
335 measurements. In this case, IA at the lowest temperature can be lower than 20 dB.
336 For suppressing the parasitic coupling, dielectric resonators shall be designed in such a way
337 that the frequencies of the resonance modes of interest are well separated from those of nearby
338 parasitic modes. The dielectric rod should be fixed at the center of the bottom superconductor
339 film by using low-loss glue. It is noted that effects of glue on the measured Q-value should be
340 negligible.
oSIST prEN IEC 61788-15:2025
IEC 61788-15 ED2 © IEC 2024 11 90/539/CDV
342 Figure 1 – Schematic diagram for the measurement equipment for the intrinsic Z of
S
343 HTS films at cryogenic temperatures
345 Key
346 1 Teflon rod
347 2 Cu plate
348 3 superconductor (or metal) film
349 4 Cu wire
350 5 switch for thermal connection
351 6 Cu plate
352 7 superconductor (or metal) film
353 8 Be-Cu spring
354 9 cold finger
355 10 Cu cavity
356 11 dielectric rod
357 12 temperature sensor
358 Figure 2 – Schematic diagram of a dielectric resonator with a switch
359 for thermal connection
oSIST prEN IEC 61788-15:2025
90/539/CDV 12 IEC 61788-15 ED2 © IEC 2024
362 Key
1 acryl plate 6 dielectric rod 11 screw
2 z-axis stage 7 superconductor film 12 superconductor film
3 teflon screw 8 Cu plate 13 Cu plate
4 connector 9 Be-Cu spring 14 semi-rigid coaxial cable
5 screw 10 Cu plate
363 Figure 3 – Typical dielectric resonator with a movable top plate
oSIST prEN IEC 61788-15:2025
IEC 61788-15 ED2 © IEC 2024 13 90/539/CDV
370 Key
371 1 stainless steel rod
372 2 micrometer
373 3 Cu block
374 4 sliding guide
375 5 Teflon plate
376 Figure 4 – Switch block for thermal connection
oSIST prEN IEC 61788-15:2025
90/539/CDV 14 IEC 61788-15 ED2 © IEC 2024
382 Key
1 screw 6 Cu braid 11 Cu block
2 Cu block 7 Cu plate 12 spring
3 Cu braid 8 screw 13 Cu cavity block
4 thermal switch block 9 Cu braid 14 Cu block
5 Cu block 10 screw 15 screw
383 Figure 5 – Dielectric resonator assembled with a switch block for thermal connection
384 5.3 Dielectric rods
385 Dielectric resonators shall be designed in such a way that the TE and the TE modes
021 012
386 appeared next to each other without being coupled to the other TM or HE modes. Furthermore,
387 the resonant frequencies of the two modes shall be close enough for reducing the measurement
388 uncertainty in ZS and far enough not to cause any coupling between them. The difference
389 between the resonant frequencies of the TE and the TE modes shall be less than 400 MHz,
021 012
390 a value corresponding to ~ 1% of each resonant frequency.
391 The dielectric rods shall have low tan δ and low temperature variation of the dielectric constants
392 and X , respectively. In this regard, c-cut
to achieve the requisite measurement accuracy in RS S
393 sapphire rods are recommended for measuring the ZS with accuracy (The relative permittivity
394 along the a-b plane ε ‘= 9,28 at 77 K for sapphire).
a-b
395 Designing schemes for the standard sapphire rod are described in Annex A.4 and A.5. Table 1
396 shows typical dimensions of the standard sapphire rod used for type A 40 GHz TE -mode
397 sapphire resonator and type B 38 GHz TE021-mode sapphire resonator, respectively. The
398 resonant frequencies become lower if the dimensions are greater, for which, however, larger

oSIST prEN IEC 61788-15:2025
IEC 61788-15 ED2 © IEC 2024 15 90/539/CDV
399 HTS films are to be used to maintain the requisite measurement uncertainty. The resonant
400 frequencies of the TE -mode for type A and type B resonators are provided in Table 1, which
401 are used during test to see if the respective resonators are installed correctly.
402 Table 1 – Typical dimensions of a sapphire rod
403                                  (Unit: GHz)

Resonator diameter height
TE -mode TE -mode TE -mode
011 012 021
frequency frequency frequency
type (mm) (mm)
A
5,00 2,86 25,27 40,06 39,97
B
5,26 2,99 24,10 38,23 38,05
405 5.4 Superconductor films and copper cavity
406 Oxygen-free high-purity copper (OFHC) shall be used for the surrounding wall of the dielectric
407 resonator. The diameter of the OFHC cavity shall be determined in such a way that the requisite
408 measurement uncertainty can be realized. Typical dimensions of OFHC cavities and HTS films
409 suggested for the standard sapphire rod are listed in Table 2.
410 Table 2 – Typical dimensions of OFHC cavities and HTS films
411                                                                          (Unit: mm)

Sapphire rod OFHC cavity HTS films
Resonator type
Diameter Height Diameter Height Diameter
A
5,00 2,86 12,0 2,86 ≥ 14.0
B
5,26 2,99 15,8 2,99 ≥ 18,0
413 6 Measurement procedure
414 6.1 Set-up
415 The measurement equipment shall be set up as shown in Figure 1. The measurement apparatus,
416 standard dielectric rods, and HTS films shall be kept in a clean and dry state as dust and high
417 humidity may affect the measurement results.
418 6.2 Measurement of the reference level
419 The level of full transmission power (reference level) shall be measured prior to measurements
420 of the resonator Q-value as a function of temperature. The measurement procedure is as follows.
421 (1) Fix the output power of the synthesized sweeper at a value below 10 mW (typically 1 mW)
422 because the measurement uncertainty depends on the measuring signal level.
423 (2) Connect a reference line of semi-rigid cable between the input and output connectors. The
424 length of the reference line shall be the same as the sum of the lengths of the two semi-
425 rigid cables with a loop at each end as described in 5.2.
426 (3) Measure the transmission power level over the frequency range and temperature range of
427 interest.
oSIST prEN IEC 61788-15:2025
90/539/CDV 16 IEC 61788-15 ED2 © IEC 2024
428 6.3 Measurement of the R of oxygen-free high conductivity copper
S
429 The surface resistance of OFHC which forms a cavity wall shall be measured as a function of
430 temperature prior to measurements of the surface resistance of superconductor films under test.
431 For this purpose, the loaded Q–value shall be measured through a transmission method with
432 the coupling loops placed near the bottom of the cavity. The coupling loops can be also placed
433 at the middle of the cavity for all the modes. In this case, the position of the coupling loops
434 needs to be closer to the dielectric rod for the TE012 mode than for the TE021 mode due to the
435 weaker coupling strength for the TE mode. The followings describe a way to measure
436 temperature dependences of the loaded TE021 mode Q-value and the corresponding unloaded
437 Q-value.
438 (1) Place the standard dielectric rod at the center of the lower OFHC endplate and fix the
439 position using low-loss glue. The glue should not degrade the microwave properties of the
440 OFHC plate and the superconductor film and be easily removable by using acetone. The
441 OFHC endplates shall be larger than the HTS films under test with the surface of the OFHC
442 endplates being well polished and clean before being used for the test.
443 (2) Connect the input and output connectors to the measurement apparatus (Figure 1) and set
444 the distance between the rod and each of the loops of the semi-rigid cables to be equal to
445 each other so that this transmission-type resonator can be under-coupled equally to both
446 loops.
447 (3) Put down an upper OFHC endplate gently to touch the top of the OFHC cavity. For the type
448 B resonator, place a 45 μm-thick Teflon ring with the respective inner and outer diameters
449 of 15.78 mm and 21.78 mm between the OFHC cavity and the upper OFHC endplate for
450 suppressing unwanted couplings between the TE021 mode and parasitic modes.
451 (4) Evacuate and cool down the specimen chamber below the T of the superconductor film to
C
452 the lowest temperature.
453 (5) Identify the TE mode resonance peak of this resonator using the calculated TE mode
021 021
454 resonant frequency.
455 (6) Set the frequency span such that only the TE resonance peak is displayed (Figure 6) and
456 confirm that the insertion attenuation IA of this mode is greater than 20 dB from the
457 reference level at the lowest temperature. Confirm that IA increases as the temperature
458 increases.
459 (7) Measure the TE mode f and the half power band width ∆f . The loaded Q-value, Q , of
021 0 3dB L
460 the TE021 mode resonator is given by
462 (8) The unloaded Q-value, QU, shall be obtained from the QL by at least one of the two
463 techniques described below.
464 The first technique is to use the IA values for obtaining the QU from the QL, for which QU is
465 expressed by
467 The QU values obtained from Equation (5) is valid if the input coupling is the same as the
468 output coupling for the resonator. The coupling loops are difficult to prepare, and the
469 coupling factors are dependent on orientation of the loop and the temperature. The potential
470 asymmetry in coupling can result in large uncertainties in calculating the coupling factor if
471 the coupling is strong (IA ≤ 10 dB). For a weak coupling of IA being greater than 20 dB,
472 asymmetry in the coupling becomes less important.
oSIST prEN IEC 61788-15:2025
IEC 61788-15 ED2 © IEC 2024 17 90/539/CDV
476 Figure 6 – A typical resonance peak. Insertion attenuation IA, resonant frequency f
477 and half power bandwidth ∆f are defined
3dB
478 The second technique is to use reflection scattering parameters at both sides of the
479 resonator at the resonant frequency, for which Q is expressed by [16, 17]
U
480 Q = Q (1 + η + η ) (6)
U L 1 2
481 with
483 S11 and S22, illustrated in Figure 7, are measured in linear units of power, not relative dB.
484 η and η denote the input and output coupling coefficients, respectively. The technique
1 2
485 employing reflection scattering parameters has two merits and demerits. The merits include
486 i) exemption of the additional step for calibrating the reference level and ii) measurements
487 of the coupling values for both sides of the resonator. Meanwhile, the demerits include that
488 the second technique is applicable only for a narrow band resonance and limited by the
489 dynamic range of the network analyzer in measuring the reflection coefficients.
490 A combination of the two techniques provides an excellent way to justify validity of the
491 measured QU, which is therefore recommended. Also, it is recommended for QU to be
492 measured with IA greater than 20 dB throughout the measured temperatures.
oSIST prEN IEC 61788-15:2025
90/539/CDV 18 IEC 61788-15 ED2 © IEC 2024
496 Figure 7 – Reflection scattering parameters S11 and S22
498 (9) The surface resistance of OFHC is obtained from the measured Q using the following
U
499 relation
501 which gives
504 for k tan δ b
...