Going towards the read-out of a
160 pixel FDM system for SAFARI
76 pixels connected
R.A. Hijmering
R. den Hartog
J. van der Kuur
J.R. Gao
M. Ridder
A.J. v/d Linden
SPICA/SAFARI
SPICA (JAXA/ESA)
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Infrared mission
~ 2.5m, ~8K mirror, Background limited
Proposed for M5, launch in ~2028 to L2
Explores dusty area and find a route to habitable planets
SAFARI instrument on SPICA (SRON + partners)
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34-210μm
Three band grating spectrometer
S-band 2x10-19 W/√Hz
3400 TESs per band
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FDM requirements for SPICA
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Pixels /channel
160 (22 channels)
Detector resolution
0.2-0.4 aW/√Hz
Signal band
60Hz
crosstalk
<0.2 10-4
Noise at SQUID input
10.5pA/√Hz
Carrier frequency range
1-3MHz
Carrier frequency spacing
12.5kHz
Carrier frequency deviation
1.2kHz
LC quality (Q)
>2355f0(MHz)~7000
Using in house developed and fabricated superconducting LC filters
In house developed TES arrays
In house fabricated Front End Electronics and Demux Board
And operated using in house developed software
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FDM readout Circuit
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Each TES has its own LC filter with unique resonance frequency
Multiple carries are send down at f0 to bias the individual TESs
Signal from the TES creates an amplitude modulation read out via SQUID
Demodulation at the resonance frequency reveals the signal
• FDM read out assembly with flexible, superconducting connection to kilo-pixel TES detectors
M. Bruijn (poster session 1 wednesday)
• The development of frequency domain multiplexing readout of TES-based X-ray microcalorimeters for Athena
H. Akamatsu (today)
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2 coil
Real Circuit
3 times voltage step down ~1M
- Resistive 2/400Ω
- Inductive 2/2000nH
- Capacitive in LC 1:9
• 2 LC filters in unit cell high+low f0
• L gradiometric
Main C
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Bias C
L div.
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FDM readout electronics
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DACbias supplied bias carriers
Summed at SQUID amplifier
Amplified by LNA
ADC I and Q
Remodulated send to input coil by DACfb for BBFB
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First itteration of the 160 pixel FDM
Changing Rstray
off
on
step
Stays normal
Changing Rn
Varying IVmin
No step
step
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Loading at high R
Varying Rn
IV curves vary pixel to pixel
Rn varies considerably
Step features
Switching neighbors on big effect
Saturation power varies with f0
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First itteration of the 160 pixel FDM
Changing Rstray
off
on
step
Loading at high R
Crosstalk!
Changing Rn
System not optimized against crosstalk
Stays normal
Varying IVmin
No step
Unable to read out 160 pixels simultaneously
step
Varying Rn
• Mutual inductance:
magnetic coupling between channels
• Common impedance:
impedance outside circuit acting as voltage divider
• Carrier leakage:
openess of filters for neighboring carriers
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160V2-pixel experiment
PTBC5 SQUID
LC
array
TES array
LC
array
LC filter chips:
• 176 resonators (87% yield)
• Spread over 2 chips
• 1MHz-3.8MHZ
GOALS
 ~160 pixels read out
 No effect of crosstalk
 High yield of TES+LC filters
 Variation of ∆f <2kHz
 TES limited noise
 No read out effects in TES
characterisation
TES bolometer array:
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176 TES +8R's (87% yield)
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Tc : 107±3 mK
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RN : 140 mΩ
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Psat,design:20 fW @ 65 mK
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NEPdesign: 7x10-19 W/√Hz
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160 pixel experiment V2
• Reduction in wire bonds (Lcom↓)
• Reduction in inductance division coils
5µH:50nH→2µH:20nH (Lcom↓)
• Mounting in stages (¼ , ½, 1)
coil
Themometer
Connection for coil
Absorbing
material
Nb foil for shielding
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160 pixel experiment V2 LC
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2 LC chips alternating f0 (M↓)
Shuffling f0 (M↓)
LC filter larger unit cell 3x3mm (M↓)
Δf in unit cell >1MHz (M↓)
Lcom total 6nH to 4.5nH, incl. SQUID
L from 2 to 3µH (CL↓)
factor 2 reduction
Δf from 14 to 16kHz (CL↓)
}
rij/kolom
1
2
3
4
5
6
7
8
9
10
11
L1/H1
1
47
133
7
93
55
141
15
101
63
149
23
109
71
157
31
117
79
165
39
125
87
173
LC chip 1
L2/H2
2
3
89
51
137
11
97
59
145
19
105
67
153
27
113
75
161
35
121
83
169
43
129
3
45
135
5
95
53
143
13
103
61
151
21
111
69
159
29
119
77
167
37
127
85
175
odd
4
1
91
49
139
9
99
57
147
17
107
65
155
25
115
73
163
33
123
81
171
41
131
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160 pixel experiment V2 TES
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Wet etch procedure
Detector chip is smaller+symmetric
Wiring shorter (M↓)
Coplanar wiring further apart (M↓)
Extra resistors for mapping
Wiring 24mm ± 0.1mm=120Hz
Development of ultra low noise TES bolometer arrays
T. Suzuki (Talk Monday)
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Measured results with one LC filter
• Connected 38 pixels followed by 76 pixels
• All TES' and R's connected found
• 76 Q's between 20k and 60k
• 76 ESR between 0.8 and 1.2 m; <ESR> = 1.0 m
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Resonance frequencies
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7 frequencies with multiple seperation due to disconnected pixels
Variation in ∆f up to 10kHz → -0.1 to 0.4% of f0
Variation in f0 caused by lithographic tolerances, first suspect is
dielectric of capacitors
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Reduction in crosstalk common impedance
dL
The measured common impedance is 1.5nH
4.5nH is expected and the difference is due to the screening of the
input coil by the feedback coil in the SQUID
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Crosstalk: effect of neighbors
90
80
70
60
50
100
120
140
160
180
Switching on neighbors has no effect on the IV curves or Power Plateaus
No influence of neighbors, no noticeable electrical crosstalk
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TES measurements
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Power Plateaus vary factor 2 due to lithographic tolerance and
production issues with wet-etch
DRIE process enables higher fabrication accuracy, ultra low noise ~40%
No frequency dependent results, (caused by biasing circuit)
Detector noise not electronic noise limited
Fabrication of low noise TES array for the SAFARI instrument on SPICA
M. Ridder (Poster G1.16 today)
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Conclusions
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Significant reduction in electrical crosstalk
Close to high yield of TES and LC filters (87%)
Frequency separation up to 10kHz >2kHz
Device limited noise
No read-out effects in device measurements as f0 dependent results
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