detectors readoutoberon.roma1.infn.it/lezioni/laboratorio_specialistico_astrofisica/... · • a...
TRANSCRIPT
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Detectors&
Readout
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History: early days• The infrared range has been discovered by
astronomers!– Friedrich Wilhelm Herschel, using a prism and
balckened bulb thermometers, detects the infraredsection of the solar spectrum (calorific rays, 1800)
• The final demonstration that IR is also EM waves happens a bit later– Macedonio Melloni in 1829 develops the
thermomultiplier, a sensitive IR detector. With thissystem he demonstrates that calorific rays have the same nature as light, also demonstrating that theyhave polarization properties exactly like light rays. He names the calorific rays “ultrared radiation”.
• The first astronomical observation is carriedout soon after:– IR radiation from the moon is detected by Charles
Piazzi Smyth in Tenerife, using a thermocouple. Healso shows that IR radiation is better detected at higher altitudes.
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History: early days• The first bolometers were developed for
astronomy, and allowed the first IR spectroscopy of an astronomical source– Samuel Pierpoint Langley in 1878 develops the
bolometer: a thin blackened platinum strip, sensitive enough to measure the heat of a cow from a distance of ¼ mile.
– The detector works because the resistance of the Pt strip changes when heated by the absorbedradiation.
– The detector is differential: 4 strips are placed in a Wheatstone bridge but only one is blackenedand exposed to incoming radiation. Common-mode effects are rejected by the bridge and tinyvariations of bolometer resistance can bemeasured.
• With his bolometer Langley is able tomeasure the IR spectrum of the sun, discovering atomic and molecular lines.
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Old times• Further developments:
– 1915 : William Coblentz uses thermopiles (an improved version of Macedonio Melloni’s detector !) to measure the infrared radiation from 110 stars, as well as from planets, such as Jupiter and Saturn, and several nebulae.
– 1920’s : systematic IR observations with vacuumthermopiles (Seth B. Nicholson, Edison Pettit and others): diameters of giant stars
– 1948: IR observations show that the moon is covered by dust.
– 1950s: Lead Sulphide photodetectors – Johnson’sstar photometry
– First Semiconductor bolometers, slicing carbonresistors to make the thermistor (W. S. Boyle and K. F. Rodgers, J . Opt . Soc . Am . 49 :66 (1959))
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One generation ago• The revolution :
– 1961: Franck J. Low develops the first cryogenic Ge bolometer, boosting the sensitivity by orders of magnitude.
– 1960’s and ff. bolometers and semiconductorsdetectors with their telescopes are carried tospace using stratospheric balloons and rockets.
• Consequence:– First sky surveys @ λ 100 μm
– 1968 First IR ground basedlarge area sky survey (2 μm, from Mt. Wilson)
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Few decades ago
• mm-wave bolometers– cooled at 1.5K or 0.3K – operating from space
• become sensitive enough to measure the finestdetails of the Cosmic Microwave Background.
• Breakthrough:– The composite bolometer (absorber and thermistor
separated and each optimized independently): N. Coron, P. Richards …
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Circa 1970
Circa 1980
Composite Bolometer(Coron, Richards …)
monoliticbolometer(Goddard, ..)
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Cryogenic Bolometers• For FIR & mm-waves spectroscopy we need very wide band
detectors. Bolometers provide the optimal choice: they are senitivefrom mm-waves to the visible range.
filter(frequencyselective)
FeedHorn(angle selective)
IntegratingcavityRadiation
Absorber (ΔT)
Thermometer(Ge thermistor (ΔR)at low T, or TES)
IncomingPhotons (ΔB)
• Fundamental noise sources are Johnson noise in the thermistor(<ΔV2> = 4kTRΔf), temperature fluctuations in the thermistor((<ΔW2> = 4kGT2Δf), background radiation noise (Tbkg
5) needto reduce the temperature of the detector and the radiativebackground.
Load resistor
ΔV
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Arno Penzias and Robert Wilson (1965):We get microwavesisotropically fromevery direction of the sky. It’s the Cosmic MicrowaveBackground.Nobel Prize in Physics, 1977
F. Melchiorri (high mountain, 1974), …. P. Richards et al.(balloon, 1980) … and then John Mather et al.(1992) with the FIRAS on the COBE satellite: these microwaveshave exactly a blackbody spectrum
Nobel Prize in Physics, 2006
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COBE-FIRAS• COBE-FIRAS was a Martin-Puplett
Fourier-Transform Spectrometer withcomposite bolometers. It was placed in a 400 km orbit.
• A zero instrument comparing the specific sky brightness to the brightnessof a cryogenic Blackbody
• The output was nulled (within detector noise) for Tref=2.725 K
• The brightness of empty sky is a blackbody at the same temperature !
• The early universe was in thermalequilibrium at high Temperature.
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σ (cm-1) wavenumber
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Primeval Fireball Additionalevidence
for an earlyhot phase
Srinand et al. Nature 408 931 (2000)
COBE Molecules in cosmic clouds(rotational levels)
)1( zTT o +=
KTo 725.2=
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Two decades ago
• The spider-web absorber isdeveloped–It minimizes the heat capacity of the
absorber–It minimizes the cross-section to
cosmic rays, while maintaining high cross-section for mm-waves
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Spider-Web Bolometers
Absorber
Thermistor
Built by JPL Signal wire
2 mm
•The absorber is micromachined as a web of metallized Si3N4 wires, 2 μm thick, with 0.1 mm pitch.
•This is a good absorber formm-wave photons and features a very low cross section for cosmic rays. Also, the heat capacity isreduced by a large factorwith respect to the solidabsorber.
•NEP ~ 2 10-17 W/Hz0.5 isachieved @0.3K
•150μKCMB in 1 s
•Mauskopf et al. Appl.Opt. 36, 765-771, (1997)
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1900 1920 1940 1960 1980 2000 2020 2040 2060
102
107
1012
1017
Langley's bolometerGolay Cell
Golay Cell
Boyle and Rodgers bolometer
F.J.Low's cryogenic bolometer
Composite bolometer
Composite bolometer at 0.3K
Spider web bolometer at 0.3KSpider web bolometer at 0.1K
1year
1day
1 hour
1 second
Development of thermal detectors for far IR and mm-waves tim
e re
quire
d to
mak
e a
mea
sure
men
t (se
cond
s)
year
Photon noise limit for the CMB
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Crill et al., 2003 – BOOMERanG 1998 bolometers, 300 mKThe same kind of bolometer is used now in Planck @100mK
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Measured performance of Planck HFI bolometers (0.1K)(Holmes et al., Appl. Optics, 47, 5997, 2008)
=Photonnoiselimit
Multi-moded
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• In steady conditions the temperature rise of the sensor isdue to the background radiativepower absorbed Q and to the electrical bias power P:
• The effect of the background power is thus equivalent to an increase of the reference temperature:
Cryogenic Bolometers
PQTTG +=− )( 0
GQTT
TTGGQTTGP
+=
−=⎥⎦⎤
⎢⎣⎡ +−=
00
00
'
)'()(
T0’
Q(pW)0.27K
0.28K
0.26K0 1 2
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• In presence of an additional signalΔQ ejωt (from the sky)
• There is a tradeoff between high sensitivity and fast response. The heat capacity C should beminimized to optimize both.
• Using a current biased thermistor toreadout the temperature change:
Cryogenic Bolometers
QTGdt
TdC eff Δ=Δ+Δ
GC
GdQdT
eff
=
+=
τ
ωτ 2211
221/
/)()(
ωταα
αα
+===ℜ
==⇒=
effGTRi
dQdT
TRi
dQdV
TRdTiidRdVdT
TdRTR
T
Small sensorat low
temperature
Responsivity
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• A large α isimportant forhigh responsivity.
• Gethermistors:
221/
)()(
ωτα
α
+=ℜ
=
effGTRi
dTTdR
TRT
110 −−≈ KTα
Cryogenic Bolometers
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• Johnson noise in the thermistor
• Temperature noise
• Photon noise
• Total NEP (fundamental):
Cryogenic Bolometers
kTRdf
Vd J 42
=Δ
( )22
22
24
fCGGkT
dfWd
eff
effT
π+=
Δ
( )( ) dxeex
hcTk
dfWd
x
xBGPh
∫ −
+−=
Δ2
4
32
552
114 εε
dfWd
dfWd
dfVd
NEP PhTJ222
22 1 Δ
+Δ
+Δ
ℜ=
Again, needof low
temperatureand low
background
Q
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1900 1920 1940 1960 1980 2000 2020 2040 2060
102
107
1012
1017
Langley's bolometerGolay Cell
Golay Cell
Boyle and Rodgers bolometer
F.J.Low's cryogenic bolometer
Composite bolometer
Composite bolometer at 0.3K
Spider web bolometer at 0.3KSpider web bolometer at 0.1K
1year
1day
1 hour
1 second
Development of thermal detectors for far IR and mm-waves tim
e re
quire
d to
mak
e a
mea
sure
men
t (se
cond
s)
year
Photon noise limit for the CMB
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Spider-Web Bolometers
Absorber
Thermistor
Built by JPL Signal wire
2 mm
•The absorber is micromachined as a web of metallized Si3N4 wires, 2 μm thick, with 0.1 mm pitch.
•This is a good absorber formm-wave photons and features a very low cross section for cosmic rays. Also, the heat capacity isreduced by a large factorwith respect to the solidabsorber.
•NEP ~ 2 10-17 W/Hz0.5 isachieved @0.3K
•150μKCMB in 1 s
•Mauskopf et al. Appl.Opt. 36, 765-771, (1997)
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Crill et al., 2003 – BOOMERanG 1998 bolometers, 300 mK
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Cryogenic Bolometers• Ge thermistor bolometers have
been used in many CMB experiments:– COBE-FIRAS, ARGO, MAX,
BOOMERanG, MAXIMA, ARCHEOPS
• Ge thermistor bolometers are extremely sensitive, but slow: the typical time constant C/G isof the order of 10 ms @ 300mK
• Once bolometers reach BLIP conditions (CMB BLIP), the mapping speed can only beincreased by creating largebolometer arrays.
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Bolometer Arrays• BOLOCAM and MAMBO are
examples of large arrayswith hybrid components (Si wafer + Ge sensors)
• Techniques to build fullylitographed arrays for the CMB are being developed.
• TES offer the naturalsensors. (A. Lee, D. Benford, A. Golding ..hear Richards..)
Bolocam Wafer (CSO)
MAMBO (MPIfR for IRAM)
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SWIPE• The Short Wavelength Instrument for the Polarization Explorer • Uses overmoded bolometers, trading angular resolution for sensitivity• Sensitivity of photon-noise limited bolometers vs # of modes:
3.23.32.5NET Focal Plane (μK/sqrt(Hz))=
302515NET (μK/sqrt(Hz) ) =
1.61.92.4FWHM (deg) =
835837N det =
1.42.13.3λ (mm)
22014590f (GHz)
402515N modes (geom) =
m0.8F =Instrumentm0.4D lens =Bolometric
0.25eff =LSPE - SWIPE
Number of modes actually coupling to the bolometer absorber
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SWIPE• Overmoded detectors are obtained coupling large area bolomete
absorbers to Winston horns. • Example of large-throughput spider-web bolometer (being
developed in Italy, F. Gatti)
• SWIPE bolometers will be made also in Cambridge (Withington)
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SWIPE• Overmoded detectors are obtained coupling large area bolometer
absorbers to Winston horns.
Simulations confirm that about halfof the modes collected by the Winston horn actually couple to the bolometer absorber(in single-polarization detectors).
Simulations by L.Lamagna, G.Pisano
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EBEX
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EBEX Focal Plane
• Total of 1476 detectors• Maintained at 0.27 K• 3 frequency bands/focal plane
738 element array 141 element hexagon Single TESLee, UCB
3 mm
5 cm
• G=15-30 pWatt/K • NEP = 1.4e-17 (150 GHz)• NEQ = 156 μK*rt(sec) (150 GHz)• msec, 3=τ
150
150 150
150250
250
420
Slide: Hanany
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William JonesPrinceton University
for the
Spider Collaboration
The Path to CMBpolJune 31, 2009
Suborbital Polarimeter for Inflation Dust and the Epoch of Reionization
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Suborbital Polarimeter for Inflation Dust and the Epoch of Reionization
Spider: A Balloon Borne CMB Polarimeter
• Long duration (~30 day cryogenic hold time) balloon borne polarimeter
• Surveys 60% of the sky each day of the flight, with ~0.5 degree resolution
• Broad frequency coverage to aid in foreground separation
• Will extract nearly all the information from the CMB E-modes
• Will probe B-modes on scales where lensing does not dominate
• Technical Pathfinder: solutions appropriate for a space mission
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Carbon Fiber Gondola
Attitude Control• flywheel• magnetometer• rate gyros• sun sensor
Flight Computers/ACS• 1 TB for turnaround• 5 TB for LDB
Pointing Reconstruction• 2 pointed cameras• boresight camera• rate gyros
Six single freq. telescopes
30 day, 1850 lb, 4K / 1.4 K cryostat
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• Constant current bias• Very high impedance voltage follower as close as possible to the
detector (inside dewar)• Very low noise OP amp amplifier (1 nV/sqrt(Hz)
Ge Bolometer Readouthigh impedance (10 MΩ) detector
To A/D converterand data storageB
+
ib
X 1000
Inside dewar Outside dewar
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JFET Preamplifier fordifferential AC bias
• AC bias currentis betterbecause the amplifier is usedat a frequencyfar from 1/f noise.
• Sine wave or triangle wavebias
• Demodulatorneeded.
• Differentialbiasing is betterbecausedifferentialamplificationremovescommon interference.
• Low noise, high CNRR amplifierneeded.
BAC
-1+1
10MΩ
5 pF
5 pF
+Vb
-Vb
180Hz +
-VACJFETs,
x100Lock-in Vout
REF
IN
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Planck is a veryambitiousexperiment.
It carries a complex CMB experiment (the state of the art, a few years ago) all the way to L2,
improving the sensitivity wrtWMAP by at least a factor 10,
extending the frequencycoveragetowards high frequencies by a factor about 10
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PLANCKESA’s mission to map the Cosmic Microwave Background
Image of the whole sky at wavelengths near the intensity peak of the CMB radiation, with• high instrument sensitivity (ΔT/T∼10-6)
• high resolution (≈5 arcmin)
• wide frequency coverage (25 GHz-950 GHz)
• high control of systematics
•Sensitivity to polarization
Launch: 14/May/2009; payload module: 2 instruments + telescope
• Low Frequency Instrument (LFI, uses HEMTs)
• High Frequency Instrument (HFI, uses bolometers)
• Telescope: primary (1.50x1.89 m ellipsoid)
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ESA : Jan TauberHFI PI : Jean Loup Puget (Paris)HFI IS : Jean Michel Lamarre (Paris)LFI PI : Reno Mandolesi (Bologna)LFI IS : Marco Bersanelli (Milano)
Almost 20 years of hard work of a very large team, coordinated by:
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HFI
LFI
ScientificLaboratories
Satellite
+ subcontractors
NationalAgencies
PI Puget
PI Mandolesi
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Ecliptic plane1 o/day
Boresight(85o from spin axis)
Field of viewrotates at 1 rpm
E
M
L2
Observing strategyThe payload will work from L2, toavoid the emission of the Earth, of the Moon, of the Sun
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Why so far ?
• Good reasons to go in deep space:– Atmosphere– Sidelobes– Stability
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• In the case of CMB observations, the detectedbrightness is the sum of the brightness from the sky(dominant for the solid anglesdirected towards the sky, in the main lobe) and the Brightness from ground(dominant for the solid anglesdirected towards ground, in the sidelobes).
RA(θ)θmain lobe
side lobes
FWHM=λ/D
boresight
⎥⎥⎥
⎦
⎤
⎢⎢⎢
⎣
⎡Ω+Ω= ∫∫ dRABdRABAW
lobesside
Ground
lobemain
sky ),(),(),(),( ϕθϕθϕθϕθ
• The angular response (beam pattern) RA(θ,φ)is usually polarization-dependent
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<<3x10-67x10-8 srad1’
<<3x10-47x10-6 srad10’
<<0.012x10-4 srad1o
<<12x10-2 srad10o
<RAsidelobes>ΩmainlobeFWHM
Going to L2 reduces the solid angle occupied bythe Earth by a factor 2π/2x10-4=31000, thusrelaxing by the same factor the required off-axisrejection.
1.5Mkm
900km L2
COBEWMAP,Planck
No day-night changes up there … extreme stability
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Planck – HFI polarization sensitive focal plane
Ponthieu et al. 2010
Scan direction
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z
NEPb = 15 aW/Hz1/2 -> 70 μK/Hz1/2
Total NET (bolo+photon) = 85 μK/Hz1/2
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LFI
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LFIPseudo-correlationDifferential radiometerMeasures I,Q,U30, 44, 70 GHz
t
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Primary
secondary
Focal Plane
Off-axis Dragone Telescope, wide field, good polarizationproperties, 1.89mx1.50m aperture
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Thermal performance :Planck collaboration: astro-ph/1101:2023
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LFI FocalPlane Unit
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Thermal performance :Planck collaboration: astro-ph/1101:2023
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Mission :Planck collaboration: astro-ph/1101:2022
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Mission : Planck collaboration: astro-ph/1101:2022
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Real data (from just 15 days of operation)
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Planck 2013 CMB anisotropy map and power spectrum data (red dots with error bars)Green line is the best fit to a 6-parameters cosmology model (inflationary Λ-CDM)
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• A large α isimportant forhigh responsivity.
• Ge thermistors:• Superconducting
transition edgethermistors:
Cryogenic Bolometers
221
)()(
1
ωτα
α
+=ℜ
=
effGRidT
TdRTR
110 −−≈ KTα
11000 −≈ KTα
S.F. Lee et al. Appl.Opt. 37 3391 (1998)
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• Have very low R, so work better at constant voltage. Lets’write in detail the equations:
Voltage-Biased Superconducting Bolometers
[ ]
PCiG
TP
eTTeCiGT
PP
TeCiTeGeTT
dTdR
RT
RVP
TeCiTeGTedTdR
RdRdVPe
TedtdCTeG
RVPe
dtdQTTeTG
RV
RVPeP
TTGR
VP
ii
iiib
tititib
ti
titibti
otibbti
ob
δωαδδωαδ
ωδδδδ
ωδδδδ
δδδδ
δδδ
ϕϕ
ϕϕϕ
ϕωϕωϕωω
ϕωϕωω
ϕωω
++=⇒⎥⎦
⎤⎢⎣⎡ ++=
+=⎥⎦⎤
⎢⎣⎡−
+=⎥⎦⎤
⎢⎣⎡+
+=⎥⎦
⎤⎢⎣
⎡+⇒
+−+=⎥⎦
⎤⎢⎣
⎡+++
−=+
−
+++
++
+
2
)()()(2
)()(2
)(22
2
1
)(
)(
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• The effective thermal conductivity is
• The first part is the Electro-Thermal Feedback (ETF) part.• When δP increases (a signal arrives) T increases; this increases the
resistance which in turns decreases the bias power Pb=Vb2/R. As a
result the total power (P + Pb) does not decrease as much, and the temperature does not change much.
• For a given incoming power, the ETF reduced the temperature change. • It is the reverse of what happens in a semiconductor bolometer, where
the negative α produces a negative ETF, increasing the temperature change.
• But here we measure the bias current at constant voltage. The currentneeded to keep the bias more stable is increased by the ETF. So wedefine
Voltage-Biased Superconducting Bolometers
PCiG
TP
eTTeCiGT
PPi
i δωαδδωαδ
ϕϕ
++=⇒⎥⎦
⎤⎢⎣⎡ ++=
−
CiGT
PGeff ωα++=
( )oi
L
GCi
GTP
CiGT
P
Lωτω
α
ω
α
ω+
=+
=+
=11
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• The Responsivity is
• And using
• We get
• Defining
• We get
Voltage-Biased Superconducting Bolometers
( )PT
TP
VPR
RRV
VPRRV
PRV
Pi b
b
b
b
bbb
δδα
δδ
δδ
δδ
δδ 111/ 2
2 −=−=−===ℜ
)1( o
iii
iLGe
CiGT
Pe
PTP
CiGT
PeT
ωτωαδδδ
ωαδϕϕϕ
++=
++=⇒
++=
−−−
)1(1
)1(11
o
i
bo
ib
b
b
b iLLe
ViLGe
TP
VPT
TP
V ωτωτα
δδα ϕϕ
++−=
++−=−=ℜ
−−
1+=
Loττ
ωτϕ
iLL
Ve
b
i
++−=ℜ
11
)1(1
For large ETF (L>>1): • the time constant is
reduced wrt the standard one by L+1
• For slow signals (ω<<1/τ) and large ETF the responsivity is simply-1/Vb
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Such a high value for α(which is >0 for TES) induces a large change in the bias power whenradiation hits the detector (electrothermal feedback)
This results in a largereduction of the time constant and in stabilization of the responsivity.
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• Are the future of this field. See recent reviewsfrom Paul Richards, Adrian Lee, Jamie Bock, Harvey Moseley … et al.
• In Proc. of the Far-IR, sub-mm and mm detector technology workshop, Monterey 2002.
TES arrays
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Cryo:0.3K
Space qual.
receiver (1pixel of 1000)
antenna
stripline
filter
membraneisland
loadTES
Si substrate withSi3N4 film
SQUIDReadoutMUX
TES for mm waves(Cardiff, Phil Mauskopf)… and many others …
150μm
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PROTOTYPE SINGLE PIXEL - 150 GHz (Mauskopf)Schematic:
Waveguide
Radial probe
Nb Microstrip
Silicon nitride
Absorber/termination
TESThermal links
Similar to JPL design, Hunt, et al., 2002 but withwaveguide coupled antenna
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PROTOTYPE SINGLE PIXEL - 150 GHz (Mauskopf)Details:
Radial probe
Absorber - Ti/Au: 0.5 Ω/square - t = 20 nmNeed total R = 5-10 Ωw = 5 μm → d = 50 μm Microstrip line: h = 0.3 μm, ε = 4.5 → Z ~ 5 Ω
TES
Thermal links
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TES Readout
A very low impedance, extremely low current noiseamplifier is needed
SQUID (Superconducting quantum interference device)Offers the perfect solution.
Martedi’.
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Very resistant: materials are all suitable for satellite and space missions.
Extremely simple cold electronics: one single LNA can be used for103-104 pixels. The rest of the readout is warm.
Very flexible: different materials and geometries can be chosen totune detectors to specific needs.
order of 103-104 pixels read with a single coax
Ease of fabrication: one single layer of material is needed.
Kinetic Inductance Detectors
A possible solution:
Main characteristics:
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The CPs have zero DC resistance, but the reactance is non-zero and has two distinctcontribution kinetic and magnetic L.
KIDs working principle:
In a superconductor below Tc , electrons can bind to form CPs withbinding energy E=2Δ =3.5*kbTc .
The total conductivity of the material can beestimated using the two-fluid model
CPs
QPs
The values of ss and sn depend on the densities of QPs and CPs. By measuring them, we can getinformation on nqp .
Js Jn
-is2nCP-is2nQP s1nQP
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A better estimate of ss and sn is obtained using the MattisBardeen integrals:
A better theory...
Note that:
• Rs decreases exponentially
• Xs becomes constant
• Xs/ Rs grows exponentially
D. C. Mattis and J. Bardeen, in Phys Rev 111 (1958)
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How can we measure the small variations of Lk?
The superconductor can be inserted in a resonating circuit with extremelyhigh Q, since:
ss RXQ ∝
The resonator is extremely simple to do, and consists of a shorted length of superconducting line capacitevely coupled to the feedline l/4 resonator
Cc
RQP
Lkin
Lmag
Cl
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KIDs are intrinsically multiplexable:
• Unitary transmission off resonance
• Q values very large (~106)
Multiplexing
Each resonator acts at the same time as detector and filter
Cnc
RnQP
Lnkin
Lnmag
Cnl
C1c
R1QP
L1kin
L1mag
C1l
C2c
R2QP
L2kin
L2mag
C2l
RF carrier (f 1 + f 2 + ... + f n )
Pixel 1, f 1 Pixel 2, f 2 Pixel n, f n
One single amplifier needed!Many potential applications
M. Calvo et al. in Conf. Proc. of 1st International LDB Workshop (2008)E.Andreotti et al. in NIMR A 572 (2008)
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How do we actually measure the incoming radiation?
n′CP< nCP
QPs
CPs
• Suppose a photon hits the detector
• If its energy is high enough (hν > 2ΔE) it can break CPs
• The density of CPs therefore changes
• This leads to a variation of Lkin
The same effect can be accomplishedby increasing the temperature of the superconductor
The readout is accomplished bymonitoring the phase of the transmittedsignal
Lf 10 ∝
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dq
Readout techniqueUsually the phase is redefined and referred to the center of the resonant circle:
This kind of plots can give allthe information regardingresonator parameters
It is also the basis for actualmeasurements of radiation
Remember that:
Tδδϑ
QPnδδϑ)T(nQP
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Cryogenic system overview
SCN-CN coax
VNA / IQ mixers
2xDC block2xDC block2x10dB atten
1xDC block1xDC block1x10dB atten
KID
300K
30K
2K
300mK
SCN-CN coax
SS-SS coax
warm amplifier
cold amplifier
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KIDs readout system
0.3K 2K
Re(S21)
Im(S21)
DAQ
fsynt
fsynt
PC
DAC
ADC
fsynt
fsynt ± f0 , fsynt ± f1...
f0, f1...
f0, f1...
fsynt ± f0 , fsynt ± f1...
Single pixel readout systemMultipixel readout system
Both systems share the core components!
0.3K 2K
Re(S21)
Im(S21)
PC
DAC
ADC
fsynt
fsynt
f0, f1...
f0, f1...
fsynt ± f0 , fsynt ± f1...
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10 mm
8 mm
capacitive coupling
2.5 mm
0.7 mm
Al CPW (200nm)
SiO2 (1μm)
Silicon Substrate(0.5mm)
KID chip descriptionMaterial: Aluminium6 resonators of varying length
Substrate:
The dielectric constant is notexactly determined!
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Base temperature characterization
All 6 resonances observed!
Typical resonanceamplitude curve
51011 ⋅≈ .Q
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Effect of temperature variation - 1
Higher T Higher nqp Higher losses
Higher T Lower nqp Lower f0
Amplitude
Phase
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Effect of temperature variation - 2
)T(Lf
TOT
10 ∝
TOT
kin
LL
=α)(L
)T(L)(f)T(f
kin
kin
021
00
0 αδ−=
δ
Quality factor increase
Estimate of kinetic inductance fraction
α ≈ 0.018
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2D data analysis
A fitting procedure has been developed to estimate the parametersof the resonators and the effect of the IQ mixers
The results are in very good agreement with the data:
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Temperature variation - 3
The blue points correspond to the base temperature resonant frequency
We obtain sensitivities of 10-3-10-2 deg/nqp
equivalent to 10-9-10-8 deg/Nqp
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Optical measurementsSystem modified by adding a filter chain
Polyethilene
window
Fluorogold(400G
Hz low
pass)
Fluorogold+
145GH
z bandpassfilter
Horn KIDGunn diode
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Quasiparticle lifetimeTo estimate the absorbed power that induces the signal we stillneed one piece of information:
QP
qpabs
nP
ητ
Δ=
τQP ≈ 30μs
When T decreases, the quasiparticlelifetime increases (nQP smaller!)
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A possible solution: LEKID
Distributed element KIDs
Lumped element KIDs
Needs some sort of antennaResponse depends on where the photon hits the sensor
C
L
It is possible to tune the meandersto match free space impedance!
ADS simulation
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Electrical NEP measurement
Dominant contribution given by the warm readout components!
Still too high for real applications, but:
High sample rate data acquired
( )22
2
2 1 QPQP
QP
NSNEP τω+
⎥⎥⎦
⎤
⎢⎢⎣
⎡
δδϑ
Δ
ητ=
−
ϑ
Theoretical limit given by GR noiseis as low as 10-20W/Hz0.5 at 100mK
P. K. Day et al. Lett. Nature 425 (2003)
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ConclusionsThe KIDs concept has been studied and theoretical
models have been developed to analyze their reponse
The experimental testbench has been completed and characterized
The first chip has been made and thouroughly tested
The first results are very promising
Yet still some open issues
• High Q factors even at 300mK multiplexing!
• Good agreement with theoretical predictions
• First light already seen
• Develop a system to reach lower T (dilution fridge?)
• Optimize optical coupling LEKID
Thanks for your attention!