Metallic Magnetic Calorimeters for High-Resolution X-ray Spectroscopy D. Hengstler, C. Pies, S. Schäfer, S. Kempf, M. Krantz, L. Gamer, J. Geist, A. Pabinger, E. Pavlov, P. Ranitzsch, M. Wegner, V. Wißdorf, T. Wolf, L. Gastaldo, A. Fleischmann, C. Enss Kirchhoff-Institute for Physics Heidelberg University

1 x 8 pixel array for X-rays up to 20 keV 250  m 5  m X-ray absorber: Electrodeposited Au Stems: Electrodeposited Au Temperature sensor: Co-sputtered Au:Er 300 ppm Superconducting pickup coil: Sputtered Nb SQUID magnetometer

1 x 8 pixel array for X-rays up to 20 keV

@ 0 keV:  EFWHM=3.0 eV 55 Mn characterization measurements Counts / 0.3 eV Energy [keV] Counts / 0.3 eV Energy [keV] Baseline Compared to expected energy resolution  E FWHM =2.6 eV slightly degraded due to untriggered small 6 keV:  EFWHM=3.4 eV

55 Mn characterization measurements Measured energy [keV] Energy [keV] Difference [keV] Non-linearity ~ 0.5% Quadratic deviation As expected from theory Flux change [ Φ 0 ] Time [  s] Rise time ~80 ns Given by Korringa relation of Er in Au

Cross talk Electromagnetic and thermal ≈ 10-4 in gradiometric setup Only relevant if  EFWHM < 1eV Cross talk x 10 -4

X-ray spectroscopy at an EBIT at the MPIK* detector ADR EBIT * Max-Planck-Institute for Nuclear Physics, Heidelberg

Superconducting Nb grid Magnetic Shielding 7 mm Nb cup attached to 4K plattform Microfabricated Spacing 100  m Width 5  m Thickness 3  m Trancparency ~ 90%

Magnetic Shielding Al cup attached to detector plattform Mechanical noise supressed Without Al shield With Al shield

X-ray spectroscopy at an EBIT at the MPIK Transitions in Sc-like (W 53+ )... Ni-like (W 46+ ) tungsten electron energy (eV) photon energy (eV) S. Georgi, Max-Planck-Institute for Nuclear Physics, Heidelberg, 2013

Detecting 60 0 keV:  EFWHM= 1.5 eV Non-linearity: keV 6.4  0

1 x 8 pixel array for X-rays up to 200 keV keV:  EFWHM=40 eV 2000  m 500  m 140  m In perfect agreement with expected resolution

Introduce stems as thermal bottle neck 1 x 8 pixel array for X-rays up to 200 keV  E FWHM =60 eV SQUID Au:Er sensor Au absorber 1st Nb layer Massive absorber on 7  m thick stems MeasuredSimulated 60 keV:  EFWHM=60 eV Degradation due to position dependent pulse shape

Towards a 2d-array 7 mm 1 mm 2 mm 8 mm Planned detector geometries Detector will be mounted on the side arm of a dry dilution fridge

Summary Design for low-energy X-rays  FWHM = keV Magnetic shielding with microstructured Nb grid Non-linearity 60 keV Design for high-energy X-rays  FWHM = keV  FWHM = keV Introduce stems to prevent position dependent pulse shape Towards a 2d array Different geometries Covering a large energy range Mounted on a 40 cm long side arm

Applications  maXs: X-ray spectroscopy atomic physics astronomy  X-ray imaging large MMC arrays microwave SQUID multiplexing  Detection of molecular fragments  Radiation standards for metrology  Neutrino mass experiments β decay of 187 Re (MARE) EC of 163 Ho β β decay of 100 Mo (AMoRE) U 91+ Advantages of MMCs  High energy resolution  Large energy bandwidth  Quantum efficiency up to 100%  Excellent linearity  Fast signal rise time

maXs (Micro-Calorimeter Arrays for High Resolution X-Ray Spectroscopy) e.g. at Gas-Jet-Target behind HITRAP at GSI/FAIR 2d detector array

Towards a 2d-array For X-rays up to 100 keV 8 x 8 pixel array Absorber volume 500 x 500 x 30 µm 3 4 mm Future geometry Stopping power keV keV keV Expected energy resolution  EFWHM=6 20mK 7 mm 48 large area absorbers For high-energy X-rays 1 x 1 mm 2 detection area 16 high-resolution absorbers For low-energy X-rays In center of the array 1 mm

Towards a 2d-array For X-rays up to 100 keV 8 x 8 pixel array Absorber volume 500 x 500 x 15 µm 3 4 mm Alternative geometrie Stopping power keV keV keV Expected energy resolution  EFWHM=10 eV 7 mm 49 large area absorbers For high-energy X-rays 16 high-resolution absorbers In center of the array For low-energy X-rays 1 mm Detector will be placed on the side arm of a dry dillution fridge

55 Mn characterization measurements Expected energy resolution  E FWHM =2.48eV Measured energy resolution Baseline:  E FWHM 6 keV:  E FWHM =3.4eV Non-linearity ~ 0.5% Rise time ~80 ns

Crosstalk maXs-200 Non-gradiometric setupGradiometric setup überprüfen Slow rise  Thermal cross talk ≈ 0.01% in gradiometric setup  Only relevant if  E FWHM < 1eV