Superconducting Electronics
for Metrology
Paul Dresselhaus
Quantum Voltage Project
Superconducting Electronics Group
National Institute of Standards and Technology
Boulder, CO, USA
Sam Benz, Alain Rufenacht, Nathan Flowers-Jacobs, Horst Rogalla, Anna Fox
June 16, 2017
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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Applications of JVS systems
10 V PJVS
2 V JAWS
2 µV QVNS
“Electronic”
kilogram
Planck
constant
Electrical
power
standard
(diff.sampl.)DVM gain &
linearity, ratio
calibration
Zener
reference
calibration
AC voltmeter
calibration
Therm. trans.
standard
calibration
Impedance
ratio
calibration
“Electronic”
thermometry
Boltzmann
constant
JVS
SYSTEMS
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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New proposed SI
Unit Actual SI NEW SI
second, s Dn(133Cs)hfs Dn(133Cs)hfs Cs hyperfine transition
meter, m c c Speed of light
kilogram, kg m(K) h Planck constant
ampere, A µ0 e Elementary charge
kelvin, K TTPW k Boltzmann constant
mole, mol M(12C) NA Avogadro constant
candela cd Kcd KcdLight source intensity at a frequency of 540 THz
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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Features of a Quantum Voltage Standard
• Intrinsic accuracy is based on quantum behavior
– Josephson effect defines the electrical properties of
superconducting Josephson junctions
• Always produces an accurate voltage
– Regardless of environmental conditions or location, which
is in contrast to “artifact” standards, and
– Over a range of all bias parameters and operating
conditions, called “flat spots”.
• Voltage is only correct on-chip
– Systematic errors must be removed or characterized
– Measurement leads & circuit parasitics (“leakage” R, L
and C) have thermal voltages & error currents
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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Single
Josephson
Junctions
Single
Josephson
Junctions
Artifact Standards for DC Voltage
Varies in time & with
environmental
conditions
10 volt
Josephson
array chip
Weston Cell,
electrochemical
battery cell
Intrinsically accurate
based on quantum
behavior of Josephson
junctions
1V
Weston Cells
10 mV SingleJunctions
1-10V
Arrays
Replaced by Josephson Voltage Standards
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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• Phase quantization ensures quantized voltage pulses
• One voltage pulse for every 2 phase change
• Pulse area is always EXACTLY one flux quantum
Quantum Behavior of Josephson Junctions
dt
d
e
htV
2
1
2
e
hdt
e
hdttV
22
1
2)(
2
00
VGHzKe
h
J /4835979.0
11
20
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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Driven Damped Josephson Junction
• DC current bias, I
• Continuous microwave or periodic pulse bias
– Supercurrent oscillations entrain to the drive frequency f
– Lock at harmonic integers n
– Generate constant DC voltage steps Vn
– Over a dc bias current range or flat spot
fe
hnVn
2
V
I
n=+1
n=0
n=1
V
I
R
Ic
Bias
I V
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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Practical Voltages Require Series Arrays
• Single junction voltages 20 µV
• 10 V is desired output voltage
• Large series arrays are required
• Uniform junctions
• Uniform microwave power
• Frequency accuracy derived from atomic
clock
nNfe
hVn
2
N Accurate
Voltage
Practical Voltages Require Long, Uniform Series Arrays
GHzVe
h2
2
V
I
No Common
Bias
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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Programmable Josephson Voltage Standard
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
9
Programmable Josephson Voltage Standard
• Sub-array JJs in ternary sequence N=1, 3, 9, ….
• 20 GHz microwave bias to all sub-arrays
• DC current bias to each sub-array selects
one of three voltage steps, n
fe
hnNVArray
2
Hamilton, Burroughs and Kautz, 1995
V
I
n = +1
n = 1
–IBias
+IBias
n = 0
20 GHz
Bias 1 3 N = 9
=4
DC Current Biases
Output Voltage
Filters
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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Fabrication & Design of Superconducting Circuits
• Boulder Micro-
Fabrication
Facility
• Superconducting integrated circuits
– Uniform junctions, barrier materials,
low-defect fabrication
• Microwave circuit design
– Lumped element inductors &
capacitors, power splitters, coplanar
waveguides, simulation & modelling
32 Arrays
with
265,116 JJs
DC Input/Output Pads
(12 x 17) mm2 PJVS Chip
Microwave Input
Splitters
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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Current (mA)
Arr
ay V
olt
age
(V) 2 mA Flat Step Width
Variation of BOTH junctions
and microwave power in arrays
Flat Spots of 16 Arrays with 16800 Junctions
Uniform junctions and microwaves
18 GHz
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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• Optimized microwave, thermal and cryogenic design
• Interchangeable operation in liquid helium probes or cryostat
• Connectorization enables solder-free, fast mounting
• Reconfigurable sub-array with flex matrix bias leads
Top Bottom
PJVS Cryopackage
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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NIST Cryocooled PJVS System
• Integrated system
– Bias electronics DC & MW
– Cryogenics
– Superconducting devices
– Turn-key integrated system
– Automation software
• Optimize & check quantum
states, flat spots
• Performs measurements
• Specific measurement
techniques needed for
different applications
Compressor
Cryostat &
MW Amplifier
4 K Cold Plate
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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Leakage currents in the PJVS system
• Need high Leakage impedance
(CJB& ALR)
– PJVS (dc leakage resistance)
• 10 V/10 G Ω = 1nA
• 1 nA * 1 Ω = 1 nV– 1 part in 1010 at 10 V
Leakage resistance should be ~> 100 G Ω
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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PJVS Applications & Best Results
• Stable DC & stepwise AC voltages
– Calibrate:
• Zener reference standards
• DVM gain, linearity
• Calibrators
• Power meters
– Precision Measurements:
• Electronic kilogram for measuring Planck’s constant, h
• Uncertainty for different measurement techniques
– DC to DC comparison of PJVS: 3 x 10-11
– Differential sampling frequencies < 500 Hz: < 1 µV/V
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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Intrinsically Accurate AC Synthesis
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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AC Voltage Standards &
Arbitrary waveform Synthesizers• Step-wise approximated sine waves
– Transitions between steps compromise accuracy
• Direct digital synthesis with current pulse sequences
– Intrinsically accurate by controlling every quantized pulse
V(t)
t
( )2
pulse
hV t
e
V(t)
t
Transitions
Steps
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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Pulse-Driven Voltage Synthesis
• Arbitrary voltage waveforms
• Pulse biased
• Directly control every JJ pulse– Digital signal provided by high-speed
pulse generator
• Waveform synthesis– Timing and polarity precisely
determine the voltage waveform
• Intrinsically accurate – Pulse density determines voltage
– JJ pulses are perfectly quantized
Co-invented in 1995 by NIST & Westinghouse researchers,
A.H. Worsham, J.X. Przybysz, S. Benz, and C. Hamilton
–√2V
Time
√2V
1 ms
1 kHz sine wave
Control 3 quantum states (+, 0, pulses) for each junction
to produce bipolar waveforms
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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“Artifact” Detectors vs. “Quantum” Sources
• Conventional AC standards are RMS detectors
– Thermally AC DC voltage signals
– “Artifact” standards have similar performance, but NOT identical
Transfer Standards
Thermal Converters
• Provide a source based on quantum effects
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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First Comparisons of 1 V AC
Josephson Voltage Standard Sources
• Statistical uncertainty of first intercomparisons of 1 V AC JAWS
voltages are now below 0.1 V/V
• Systematic errors are ~1 V/V for kilohertz frequencies
1 V
JAWS
Commercial
Voltage
Calibrators
Weston Cells
SingleJunctions
PJVS
Calibrators
JAWS
DC AC
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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1V rms JAWS Chip and Circuit
• 51,240 total junctions in 4 arrays
• 2 pulse biases and 4 low-speed biases
• Clocking pulses at 15 GHz = 770x1012 quantum states/s
• Measure spectra with a 24-bit ADC digitizer
1 cm x 1 cm Chip
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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2016: 2 V cryocooled system,
4 pulse channels (2 sets of bias electronics)
Advances in the JAWS system
1 V ± 1 V output
Pulse2Pulse2Pulse1Pulse1
4.3 K cryocooler
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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Flat Spot of Quantum States
Nathan Flowers-Jacobs, 2016
1.1 mA DC
Bias Current
Difference from Sine Voltage
V(Measured) - V(Calc Sine)
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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-165 dBc from 2 V
92 nV rms
(nominally 0 V
rms)
1 V ± 1 V JAWS comparison at 1 kHz• Null measurement
2.0000
V rms
nominally
0 V rms
quadrature (V rms)
in-p
has
e (V
rm
s)
1
2
00 1-1
20 nV rms
Insensitive toADC
gain/linearity
Sensitive tosingle-pulsetime delays
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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JAWS Applications
• Calibrations:
– Voltage calibrators
– AC-DC transfer standards
– Thermal converters
• May require trans-impedance amplifier
• Characterizing analog and digital electronics:
– Gain, linearity, and distortion of analog-to-digital converters
(ADCs) and amplifiers
• Impedance comparisons (*New)
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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Josephson-Based Full Digital Bridge for high-
accuracy impedance comparisons
• Voltage ratio can be set to any desired value and frequency
– Don’t need different transformers to match different impedance ratios
– Allows direct comparison between the decadal scale and AC-QHE, 10:12.906
• Any impedance in the complex plane can be calibrated
– Because the phase between the JAWS sources can be adjusted to any value
Overney et al., Metrologia, June 2016
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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Quantum Voltage Noise Source
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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Artifact Standards in
Thermometry
• ITS-90 scale of fixed points
• K defined by triple point of water
• Scale is designed to “represent”
thermodynamic temperature
• Interpolation required for temps
between fixed points
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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(52 nV)2 rms
1600 Hz harmonics
Johnson Noise Thermometry with a
Quantized Voltage Noise Source
• Fully electrical measurement of thermodynamic temperature
• Measure Johnson noise voltage of a 100 Ohm resistor at different temperatures
• SMALL 2 nV/√Hz noise voltage amplifier noise voltage
• Requires cross-correlation measurement techniques
• Calibrate electronics with quantum-accurate “pseudo-noise” voltage synthesized with a QVNS
2 4 D DT TV S f kTR f
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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Johnson Noise Thermometry
• Compare thermal and electrical noise powers
• Temperature is determined by noise ratio, measured
resistance R, fundamental constants h, k and Rk, and
QVNS constants D, N, fclock and M)
T
Q
S
S
Water Triple Point
R, Johnson Noise
Quantized Voltage
Noise Source (QVNS)
Noise
Voltage
Correlator
SQ
ST
16
22 MNDf
R
R
S
S
k
hT clock
k
Q
T
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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Quantum Voltage Noise Source QVNS
8 junctions
Cryopackage
1 cm2
Chip
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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NIST Johnson noise thermometer
Resistor,
Triple Point Cell, and
Thermoelectric Cooler
Chargers
Batteries
Cross-Correlation
Electronics
QVNS in LHe Dewar
Pulse Bias Source is
outside shielded room
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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Johnson Noise Thermometry Results
• Electronic determination of Boltzmann’s constant, k
– Uncertainty results
• 1210-6 (5ppm Type A in 10 days) NIST USA, 2010
• 410-6 (3ppm Type A in 34 days) NIM China, 2015
• (9ppm Type A in 7 days) AIST Japan, 2016
– < 310-6 is the goal for SI redefinition
• Primary “thermodynamic” thermometer
– Measured Sn, Ga and water on ITS-90 temperature scale
– Perfect voltage and temperature linearity has potential to
increase knowledge of ITS-90 fixed-point “artifacts” and
eliminate interpolation between temps
16
22 MND
T
f
R
R
S
S
h
k
TPW
clockk
Q
T
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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Summary• Programmable Josephson Voltage Standard (PJVS)
– Intrinsically accurate DC voltages
– ±10V peak stepwise-approximated AC waveforms
– Requires differential sampling on steps to realize quantum accuracy
– Applications: DC voltage, AC voltage < 200 Hz, AC power
• Josephson Arbitrary Waveform Synthesizer (JAWS)
– Intrinsically accurate AC waveforms
– 2 V RMS sine waves, or 5.6 V peak-to-peak arbitrary waveforms
– Challenge is sourcing current to low-impedance meters
– Applications: DC voltage, AC voltage, AC power, Impedance
• Pulse-driven Quantum Voltage Noise Source (QVNS)
– Intrinsically accurate arbitrary waveforms
– 2 V peak arbitrary waveforms of harmonic combs
– Applications: Johnson noise thermometry, primary thermometry
Microwave
Bias
Pulse
Bias
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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Future of JVS for SCE
• Quantum voltage standards continue to:
– Improve in performance (V, margins, frequency)
– Replace artifact standards (DC, AC, temperature)
– Be applied in precision measurement that require quantum
accurate performance (kg, h, k, impedance, RF metrology
and perhaps quantum computing).
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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Superconductive Electronics Group in Boulder, Colorado
Thank you!
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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Flat Spots at 10 V
Alain Rufenacht, 2016
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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Flat Spots at 10 V
Alain Rufenacht, 2016
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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Flat Spots at 0 V (+5 V and 5 V)
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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Systems & Circuits
60 Conventional JVS (incl. Hypres, Inc.)
18 Programmable JVS
8 Josephson Arbitrary Waveform
Synthesizer
4 Johnson Noise Thermometer
Measurement Labs
National Measurement Institutes: international
National Laboratories: NASA, Sandia
Industry: HP, Lockheed, Fluke, Keithley, Boeing
DOD: Army, Navy, Air Force
DOE: Oak Ridge Nat. Lab.
NIST Voltage Standard Systems and Circuits
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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Uncertainty of RMS Detector-based Calibrations
1000 V
100 V
10 V
1 V
100 mV
10 mV
1 mV
10 Hz
100 Hz
1 kHz
10 kHz
100 kHz
1 MHz
5
1 V/V
10
20
100
300
50200100
1000
Frequency
Vo
ltag
e
Original JAWS
JAWS Region
of Impact
10x-100x
reduction
1 Hz
New 2V JAWS
Tom Lipe, 2005
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), No. 41, July 2017. This keynote presentation Fr-KEY-01 was given at ISEC 2017.
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