One of the activities of the spatial team of the CNRS/CRTBT Samuel Leclercq, CNRS/CRTBT (Grenoble, France) European Network on Applied Cryodetectors Munich,

One of the activities of the spatial One of the activities of the spatial team of the CNRS/CRTBTteam of the CNRS/CRTBT

Samuel Leclercq, CNRS/CRTBT (Grenoble, France)

European Network on Applied Cryodetectors

Munich, Germany, 7th November 2003

ProjectsProjects• Bolometric Camera for

Millimetre wavelengths• Diabolo• Archeops• Planck• Edelweiss II

TeamTeam• Alain Benoit• Philippe Camus• François-Xavier

Désert• Samuel Leclercq

One of the activities of the spatial One of the activities of the spatial team of the CNRS/CRTBTteam of the CNRS/CRTBT

Goals for the bolometric camera

64x64 pixels @ =1.2 mm (250 GHz), 1.5x1.5 mm2/pixel (FWHM 8.5") 32x32 pixels @ =2.1 mm (143 GHz), 2.6x2.6 mm2/pixel (FWHM 15")

Shannon sampling of the unvignetted 260" field of view at the IRAM 30m telescope.

1 hour for the detection of a 3mJy source (Fgalaxy ≈ 1012 L)(10 hours with best actual instruments)

Reach optimum abilities of the IRAM 30 m telescope : angular resolution and photon noise. SZ effect and high z galaxy mapping.

Wavelength 1,2 2,1 mm

CMB power / pixel 9,7 12,5 fW

Total power / pixel 6630 4630 fW

NEP / pixel 6,0 2,8 10-17 W / Hz

NEP / Airy FWHM 17 8 10-17 W / Hz

NET / Airy FWHM 410 588 K s

NEFD / Airy FWHM 1,0 1,5 mJy s

For one pixel with 1 mm water vapour in atmosphere, and instrument NEP = 50% of total photon NEP :

1 Jy = 10-26 W/m2/Hz

0 2 4 6 8 10 12 14 16 18 200

1

2

3

4

5

6

7

8

9

Résistance différentielle en fonction de la tension

abs(V2) (mV)

Exemple of electro-thermal tests.

80mK

150mK

200mK

300mK

NbSi single bolometerBolometer on thin Si3N4 membrane

L=300mS=60m2

NbSi : Anderson insulator, variable range hopping.Goal : reach the metal-insulator transition at the dilution

temperature (100 mK). Efros and Shklovskii law :NbSi

Au/Cr

Au/Cr (thermal link)

Bi (absorber)

R(T ) R0 expT0

T

R(T)

0,00

1,00

2,00

3,00

4,00

5,00

6,00

7,00

8,00

100 120 140 160 180 200 220 240 260 280

T(mK)R

(Mž)

Ro=11kž ; To=5,4K

Ro=4,4kž ; To=7K

Ro=2,4kž ; To=8K

mesures

NEP : 5.10-17 W/ Hz

Ad lnR

d lnT

1

2.ln

0

Optimisation : A ≈ 10 and R fit to the electronic read out. Controlled by the shape of the NbSi thin layer + Nb composition

#1 à #8

#10 #13#11

Lithography : <0 resist and 365nm UV exposure

Au ≈ 1500 Å

Ti ≈ 50 Å Nb ≈ 500 Å

Ir ≈ 50 Å

NbSi ≈ 1000 Å

SiO ≈ 250 Å

Only wafers #11 and #13 have Nb electrodes deposited

with mechanical mask.4 kinds of arrays tested

Resist / Lithography

Shadow mask

NbSi arrays

Smooth edges no contact problems

No resist no pollution problems

0 5 10 15 20 25 30 35 40 45 500

10

20

30

40

50

60

70

80

90

Résistance différentielle en fonction de la tension

abs(V2) (mV)

loi d'Efros et Shklovskii

10

11

12

13

14

15

16

17

18

19

20

21

0,8 1 1,2 1,4 1,6 1,8 2 2,2 2,4 2,6 2,8 3 3,2 3,4 3,6 3,81/¦T [1/¦K]

#3

#4

#5

#6

Fits : R0 = 1,1 k16 < T0 (K) < 18,8

Ad(lnR)

d(lnT )4

R(V) = V/I still too high at low V. Films not as homogenous as expected. Yet, shapes fits with electron-phonon decoupling : ge–ph = 100 W/K5/cm3. Better results on #13 (data processing in progress).

NbSi arraysTests on wafer #11

Electronic multiplexing

Necessity for a cold multiplexing system with low current and low noise electronic

Without multiplexing system

Matrix NxN N2+2 wires between dilution and 300K too much.Ex matrix 32x32 1026 wires. input

polarisation

NxN output signals

bolometer matrix only

Rload

Rbolo

Matrix NxN 2N+2 wires.Advantages : volume occupied and conductive heat loads by wires, dissipation from cold JFET amplifiers.Ex matrix 32x32 66 wires.

With multiplexing system

Commutation transistor : HEMTs

Capacity filtering transient effects : C 1 nF

bolometer and transistors matrixes

N commutation

lines

N output signals

Electronic time multiplexing for high Z LTD

FREQUENCY REQUIREMENTSBolometer Signal bandwidth B = 10 HzBolometer Sampling frequency Fsampling > 2 B

ELECTRICAL NOISE ANALYSISBolo Johnson noise eN,bolo = (W/ )

Read time/pixel tmes = 1/Fsamping

Amplifier HF noise eN,ampl (W/ )

Sample RMS noise

TYPICAL DESIGNRb = 10M; CINT = 1.6 nF ; T=100mK ; e N,bolo=7.4 nV/

4 kB RT

eRMS2 eN,bolo

2 1.53 fRC eN ,ampl2

NFSAMPLING2

CAPACITIVE POLARISATION

• No power dissipation at low temperature• Cold capacity (CPOL ~ 5pF) to avoid any leakage current

Minimisation of transient effects when commutation occurs

Hz

Hz

Hz0,1

1

10

100

0,01 0,1 1 10 100 1000 10000Hz

nV

/Hz1

/2

Bolo before modulationAmplifier (not modulated)Bolo after modulationBolo after demodulationAmplifier after demodulation

In progress : conception and test of a complete bolometer matrix with bow tie absorber antennas

1) nitruration

2) RIE (SF6)

3) KOH thermal membrane

4) Nb electrodes with shadow mask

5) NbSi thermometer with shadow mask

6) Au track lithography

7) SiO2 isolation

8) Nb antennas lithography

9) Bi shunt lithography

10) KOH opening membranes

In progress : conception and test of a complete bolometer matrix with bow tie absorber antennas

Test of antennas absorption on a Fourier Transform Interferometer

(Martin Pupplet)

Very low capacity Cgs~1fFRON <104 ROFF>107Array of 13 HEMTs with common source in PLCC-28 supportsIg<0.1pASmall voltage variation for switchingConduction noise = Johnson [PRL]

In progress : development of Quantum Point Contacts HEMTs too improve the multiplexing system

Coming nextNbSi :- Electric tests on a bolometer matrix with field effect and electron-phonon decoupling fittings.- Fourier Transform on V(I) curves Phonon, Johnson, 1/F and "pop corn" noises.

Antennas :- Numerical analysis of electromagnetic absorption by antennas with a fourth wave cavity (in progress).- Conception of a Martin Pupplet interferometer.- Studies on different shapes and tests with the Martin Pupplet.

Bolometers :- Finishing the electronic and instrument control program.- Heat transfers in membranes.- Photon noise recording and calibration with a black body (in progress)

Around the matrix : - radiation filters - dilution fridge for the camera - lenses and mirrors for adaptation on the IRAM 30 m telescope

Optical axe of the telescope (F/D=10)

Field mirror

Focal plane of the field mirror on the cold lens

Image of the sky< 1 m