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Metallic magnetic calorimeters (MMC) for high resolution x-ray spectroscopy

Metallic magnetic calorimeters (MMC) for high resolution 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. 4.2 K. 50 mK. 300 K. B. +. +. +. +.

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Metallic magnetic calorimeters (MMC) for high resolution x-ray spectroscopy

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  1. Metallic magnetic calorimeters (MMC) for high resolution x-ray spectroscopy Loredana GASTALDO, Markus LINCK, SönkeSCHÄFER, HannesROTZINGER, AndreasBURCK, SebastianKEMPF , Jan-PatrickPORST, AndreasFLEISCHMANN, ChristianENSS, George M. SEIDEL

  2. 4.2 K 50 mK 300 K B + + + + Au:Er 300 ppm Au:Er 300 ppm Specific heat C [104 J mol1K1] Magnetization M [A/m] Temperature T [mK] Inverse Temperature T1 [K 1] Detector 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 Very stable material suitable for long lasting measurements

  3. Noise & energy resolution Fluctuations of energy in a canonical ensemble Magnetic Johnson noise (thermal currents in the metallic sensor ) Flux noise of the SQUID-magnetometerenergy sensitivity close to quantum limit required, 1/f noise Cabs Cspins (order of magnitude: 1eV for a 10 keV x-ray detector) electron sensor SQUID

  4. Aluminum thin window Lead Collimator Field coil Brass holder Circuit board Superconducting shield (lead) Detector set-up Detector SQUID 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: KSUP-10-50 (IBM) Amplifier SQUID: CCBlue (IPHT Jena)

  5. Magnetization and chip temperature Tchip [K] Magnetic Flux Tbath [K] Dissipation on the SQUID chip leads to a decoupling of the chip temperature from the bath temperature

  6. Pulse analysis Temperature T [mK] Time t [ms] The amplitude of pulses saturates at low temperatures and high fields Rise time 100 s fast decay time 650 sDecay time slow decay time 8.1 ms

  7. 55Fe energy spectrum Counts / 15 eV Counts / 2 eV Energy E [keV] Energy E [keV] Energy [keV] Transition A 3.695 keV B  3.775 keV Very low background

  8. Energy resolution and linearity Measured energy Eexp [keV] Relative pulse amplitude A Counts / 0.24 eV A - Ai Difference [eV] Energy E [keV] Energy Energy E [keV] 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 Counts / 0.12 eV Energy E [keV]

  9. Conclusion 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

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