Post on 11-Jan-2016
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Metallic magnetic Metallic magnetic calorimeters (MMC) for high calorimeters (MMC) for high resolution x-ray spectroscopyresolution x-ray spectroscopy
Loredana GASTALDO, Markus LINCK, Sönke SCHÄFER, Hannes ROTZINGER, Andreas BURCK, Sebastian KEMPF , Jan-Patrick PORST,
Andreas FLEISCHMANN, Christian ENSS, George M. SEIDEL
Inverse Temperature T1 [K 1]
Ma
gn
etiz
atio
n
M
[A/m
]
Au:Er 300 ppm
Temperature T [mK]
S
pe
cific
he
at
C
[1
04 J
mo
l1K
1]
Au:Er 300 ppm
Detector setupDetector setup
Thermodynamic properties of interacting spins (RKKY) can be calculated with confidence by mean field approximations or Monte Carlo simulations optimization by numerical methods is possible
totC
ET
totC
E
T
MT
T
M
11
IM2GR
+ + + +I V
50 mK 4.2 K 300 K
B
Very stable material suitable for long lasting measurements
Fluctuations of energy in a canonical ensemble
Magnetic Johnson noise(thermal currents in the metallic sensor )
Flux noise of the SQUID-magnetometer energy sensitivity close to quantum limit required,
1/f noise
sensorelectron
SQUID
(order of magnitude: 1eV for a 10 keV x-ray detector)
Cabs Cspins
100 .. 502/ LS
Noise & energy resolutionNoise & energy resolution
4/1
1
02 2436.2
TCkE absBFWHM
Aluminum thin window
Lead
Collimator
Brass holder Circuit board
Field coil
Superconducting shield (lead)
Detector set-upDetector set-up
Detector SQUID: KSUP-10-50 (IBM)
Amplifier SQUID: CCBlue (IPHT Jena)
Sensor Au:Er 600 ppm x (12.5)2 x 8 m3 Absorber Au 180 x 180 x 5 m3 stopping power above 98% @ 6 keV
Pulses acquired at different temperatures and at different magnetic fields
Detector SQUID
Magnetization and chip temperatureMagnetization and chip temperature
M
agne
tic F
lux
Tbath [K]T
chip
[K]
Dissipation on the SQUID chip leads to a decoupling of the chip temperature from the bath temperature
Pulse analysisPulse analysis
Rise time 100 s fast decay time 650 s Decay time slow decay time 8.1 ms
Time t [ms]
The amplitude of pulses saturates at low temperatures and high fields
Temperature T [mK]
5555Fe energy spectrum Fe energy spectrum
C
ount
s / 2
eV
C
ount
s / 1
5 eV
Energy E [keV] Energy E [keV]
Very low background A 3.695 keVB 3.775 keV
Energy [keV] Transition
Energy resolution and linearityEnergy resolution and linearity C
ou
nts
/ 0
.24
eV
C
ou
nts
/ 0
.12
eV
Energy Energy E [keV]
Energy E [keV]
Rela
tive
pu
lse a
mp
litu
de A
Measu
red
en
erg
y E
exp [
keV
]D
iffere
nce
[eV
]
Energy E [keV]
A -
Ai
TFN 0.38 eV+ SQUID 1.14 eV+ 1/f 1.6 eV ???? 1.85 eV still missing!
1/f2 due to temperature fluctuations of the chip
Conclusion and future plansConclusion and future plans
•2,7 eV energy resolution is a good result but it does not rapresent the limit of magnetic calorimeters
•Improvements of our detector will follow the good results we are obtaining with microstructuring techniques
-166Er enriched Au:Er sputter target-Sputtered Au:Er sensor-Overhanging absorber