Diapositiva 1

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Transcript Diapositiva 1

"The Extreme sky: Sampling the Universe above 10 keV"
IXO TES Microcalorimeters:
from Focal Plane instruments to Anticoincidence Detectors
Claudio Macculi,
Luca Colasanti, Luigi Piro
INAF/IASF Roma
13th - 17th October 2009
Otranto (Lecce) Italy, Castello Aragonese
Italian collaboration
Piro Luigi
Morelli E. (IASF-Bo)
Colasanti L. Rubini A.
Macculi C.
Mastropietro M. (CNR/ISC)
Natalucci L. Lotti S.
Mineo T.
Barbera M.
La Rosa
Perinati E.
Gatti F.
Ferrari L. + Tech. personnel
Bagliani D.
Torrioli G.
Bastia P.
Bonati A.
Outline
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TES microcalorimeter: working Principle
Cryogenics and Readout electronics
Detector Sizes, Single Pixel and Array results
IXO X-ray Microcalorimeter Spectrometer
Cryogenic AntiCoincidence Detector
•
Preliminary Test
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Conclusion
Future: CryoAC as Hard X-ray ray detectors?
TES microcalorimeter: working Principle
…used from Microwave to soft-Gamma ray domain...

T dR

R dT
The X-ray micro calorimeter consists of a:
• X-ray absorber (CABS)
• temperature sensor
• a thermal link (G) that connects the absorber to a heat bath
A thermal bath to keep the absorber's temperature constant is necessary
(restore the Working Point)
Photon absorption  Absorber temperature change  Change in TESresistance. Since the TES is Voltage polarised  Change in current
Weak currents (also < μA), low TES Resistance (~ 0.1 Ohm)  a special lownoise current amplifier is required  SQUID Amp. (Superconducting
Quantum Interference Device Amplifier)
2
VTES
dT (t )
C
 G[T (t )  Tb ] 
 E (t )
dt
RTES [T (t )]
t
E  ETF
T  Tb  e
C
T R  I
Electro-Thermal Feedback – Energy Bandwidth – Energy Resolution
C
 th 
G
 ETF 
 th
1 L
Tb  TTES   ETF 
 
 T 
L   1   b 
n   TTES 

n



 th
  th
1  n
The Joule heating produced by Voltage bias
PJ = V2/R:
if T  R  PJ  R
 Electro-Thermal stability
Moreover: strong reduction of the decay time
constant  fast signals  high count rate
(bright sources or big area optics)
En. Bandwidth EMAX 
CT
0.63  
En. Resolution EFWHM  2.35
1

Attenuation of thermal bath
temperature fluctuations
 kT 2C  kTEMAX
High En. BW  High C, Low alfa (wide transition)
High En. Res.  low T  cryogenic detector
 low C  high alfa (narrow transition)
Trade off is necessary to reach the wanted
performances
Tb/TTES
Cryogenics and Readout electronics
Readout electronics:
Cryogenics:
3He/4He
mixture (working on phase separation)
few-10 mK base temperature (tens to hundred
μ[email protected])
4He Pulse tube + ADR (ADR works on
paramagnetic salt demagnitazion) about 30 mK
base temperature (3 μ[email protected] for 20 h
operation)
Temp. stability: about 10 μKrms (several hours)
3He
fridge
insert
(Kelvinox)
SQUID (micro-machined device):
Magnetic flux is generated by TES-current
flowing in a coil coupled to the SQUID. Such a
flux crosses the Josephson junction where it is
transformed in Voltage.
Noise: few pA/rtHz up to some MHz bandwidth
Bias Power: few nW
Vericold ADR
system
Supracon
Cold
finger
Niobium can
for magnetic
shielding
Magnicon
Detector Sizes and Single Pixel results
TES on silicon membrane (tech. used for the Array):
- Ir/Au, Ti/Au or Mo/Au (total thickness about 1E+2 nm) onto SiN (1
um) suspended membrane (TES area depends on the pxl area)
- Absorber (Au, Au/Bi, Cu/Bi, Sn, few um thick) growth on the TES
substrate
- Pixel about 250x250 um
EFWHM = 3.6 eV
INFN and Genova Univ.
Ferrari, Gatti et al.
INFN and Genova Univ.
TMU-ISAS
SRON
Hoevers et al., J Low Temp Phys, 151, (2008) Akamatsu, LTD13, in press, (2009) Bandler et al., J Low Temp Phys, 151, (2008)
What about the Array?
Multiplexing technique is necessary to minimize the heat load caused by thermal conduction through
the harness to the cold finger (thousand wires). The array is powered and read by rows or by columns
using different Multiplexing methods:
32x32 NASA GSFC – IXO/XMS
• FDM (sinusoidal excitation)
(bond pads for 256 channels only)
• TDM (switch ON/OFF line by line)
• CDM (inversion bias polarity)
FDM technique:
• Pixels are AC-biased (line by line)
• Summing node (column by column)
• De-modulation by the same frequency
to recover the pulse
Eckart, Doriese, SPIE Newsroom , 2009
IXO X-ray Microcalorimeter Spectrometer
IXO consortium-CoPI  NASA/GSFC, SRON, ISAS-JAXA, INAF/IASF Roma
 Central, core array:
Layout wich fits the IXO Reqs.
– Individual TES
– 42 x 42 array with 2.9 arc sec
pixels
– 2.0 arcmin FOV
– 2.5 eV resolution (FWHM)
– ~ 300 sec time constant
– 0.2-10 keV
 Outer, extended array:
– 4 absorbers/TES
– Extends array to 5 arcmin FOV
– 52 X 52 array with 5.8 arcsec
pixels
– <10 eV resolution
– <2 msec time constant
Inner Pixel: ~ 300x300 m2
Outer Pixel: ~ 600x600 m2
Absorber: Bismuth 7 m
Cryogenic AntiCoincidence Detector
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Bkg requirement: 2·10-2 cts cm2 s-1 keV-1
Without AC: at least 10 times larger (from preliminary simulation only GCR
accounts for 0.15 cts/cm2/s/keV)
Requires an AC with > 95% rejection efficiency
AC need to be < 1mm near to the TES  Cryogenic detector
Rej eff. = 99%
D < 1mm
TES-Array:
Cryo-AC
MIP Events
to be rejected
CryoAC Design
We decide for TES-based Cryo AC made of Silicon due to the experience inside our collaboration
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Baseline Geometry: Assembly of 4 sub-unit
Detector technology: TES, the same of the focal plane instrument  simplification of the
Electrical, Mechanical and Thermal I/F ( increase reliability the TRL)
DT Analysis (Cosmic ray flux plus soft protons from mirrors plus Solar flare):
– 5% DT  To be conservative CryoAC “Total recovery time” < 500 μs
– Without Solar Flare, a DT = 1% corresponds to a “Total recovery time” up to 1 ms
– “Total recovery time” to be compared with the TES-Array time constant
Expected maximum deposited energy ~ 4 MeV  CryoAC Energy Bandwidth: 0.5-1 MeV (to increase
BW solving the saturation  trade-off with the time constant and Dead Time)
Suppose up to 300 μm thick  about 90 keV released from MIP. At least S/N > 10  Emin = 5 KeV
CryoAC
Different thickness  EMAX and Eth(Epr)
if Eth(Epr) > EMAX  Saturation
18 mm
18 mm
TES Array
30 mm
Thickness
(μm)
Emax
(MeV)
Saturation Range
Primary pr En. (MeV)
100
0.4
0.9-15
150
0.6
1.05-15
200
0.8
1.2-15
250
1
1.4-15
300
1.2
1.6-15
IXO-CryoAC Prototype measurements: Preliminary Test
Thickness = 300 um
Produced at Genova University
3.3 mm
ABSORBER Si n-type: 16-27 ohm*cm
A ~ 16.5 mm2
TES  Iridium V = 3.7mm2 x 90nm
5 mm
Illumination
hole
EMAX ~ 450 keV
SQUID
55Fe
Source
setup
Results: Fast signals and low energy events detected
55Fe
Source
Ib = 650 uA
Amplitude Variance
under investigation
PH 
E
CT
 I bias
Conclusion
Results from a detector of C ~ 16.5 pJ/K and A ~ 16.5 mm2 (~ x200 usual pixel area):
1.
2.
3.

Events from 55Fe detected
Fast Rise time ~ 2 μs
Fast Decay time ~ 100 μs for near null ETF  we got Fast signals (D TES array ~ 300 μs)
NOT FAR FROM THE GOAL
Next future
Further Investigation for amplitude Variance
Test on 10x10 mm2 pixel, 50 μm thick (V ~ 5 mm3)
 Same Volume of the present detector but 6x in Area (final size 18x18 mm2)
 It is also foreseen to use 241Am (~ 5.5 MeV) to study the saturation regime (Dead time)
Future: CryoAC as Hard X-ray ray detectors?
Already exists TES-detector with E/dE > 2000 at 60 keV
adopted for nuclear materials analysis
Tin bulk absorber (~ 1x1x0.25 mm3) by-layer Mo/Cu TES
D.T.Chow et al.,
Proceedings of SPIE Vol. 4141 (2000)
TES: 200 nm thick
[email protected] (expected ~ 23 eV)
TES
400 μm square
W.B. Doriese et al., J Low Temp Phys (2008) 151
Ciao!