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 PhysicsHeidelberg University

1 x 8 pixel array for X-rays up to 20 keV250 m

250 m

5 m

X-ray absorber:Electrodeposited Au

Stems:Electrodeposited Au

Temperature sensor:Co-sputtered Au:Er300 ppm

Superconducting pickup coil:Sputtered Nb

SQUID magnetometer

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

@ 0 keV: DEFWHM=3.0 eV

55Mn characterization measurementsCo

unts

/ 0.

3 eV

Energy [keV]Co

unts

/ 0.

3 eV

Energy [keV]

Baseline

Compared to expected energy resolution DEFWHM=2.6 eV slightly degraded due to untriggered small pulses

@ 6 keV: DEFWHM=3.4 eV

55Mn characterization measurementsM

easu

red

ener

gy [k

eV]

Energy [keV]

Diffe

renc

e [k

eV]

Non-linearity ~ 0.5%• Quadratic deviation• As expected from

theory

Flux

cha

nge

[Φ0]

Time [s]

Rise time ~80 ns• Given by Korringa

relation of Er in Au

Cross talk

Only relevant if DEFWHM < 1eV

Cross talkx 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 (W53+) ... Ni-like (W46+) tungsten

electron energy (eV)

phot

on e

nerg

y (e

V)

photon energy (eV)

photon energy (eV)

S. Georgi, Max-Planck-Institute for Nuclear Physics, Heidelberg, 2013

Detecting 60 keV

@ 0 keV: DEFWHM= 1.5 eVNon-linearity: 3.3 % @ 60 keV

6.4 0

1 x 8 pixel array for X-rays up to 200 keV 

SQUID

@ 0..10 keV: DEFWHM=40 eV

2000 m

500 m140

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

DEFWHM=60 eV

SQUID

Au:Er sensor

Au absorber

1st Nb layer

Massive absorber on 7 m thick stems

Measured Simulated (FEMM)

@ 60 keV: DEFWHM=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• DEFWHM = 3.4 eV @ 6 keV• Magnetic shielding with microstructured Nb grid• Non-linearity 3.3% @ 60 keV

Design for high-energy X-rays• DEFWHM = 40 eV @ 0..10 keV• DEFWHM = 60 eV @ 60 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 187Re (MARE) EC of 163Ho β β decay of 100Mo (AMoRE)

U91+

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)

Gas-Jet Target

(U Frankfurt)Beam of decelleratedHighly Charged Ions (HITRAP, GSI/FAIR)

X-Ray Lens for soft x-rays (U Jena)10

keV

100 keV

e.g. at Gas-Jet-Target behind HITRAP at GSI/FAIR

2d detector array

Towards a 2d-array

For X-rays up to 100 keV8 x 8 pixel array

Absorber volume• 500 x 500 x 30 µm3 4

mm

Future geometry

Stopping power• 100 % @ 10 keV• 53 % @ 40 keV• 26 % @ 100 keVExpected energy resolution• DEFWHM=6 eV @ 20mK

7 mm

48 large area absorbers• For high-energy X-rays• 1 x 1 mm2 detection area16 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 keV8 x 8 pixel array

Absorber volume• 500 x 500 x 15 µm3 4

mm

Alternative geometrie

Stopping power• 97 % @ 10 keV• 32 % @ 40 keV• 14 % @ 100 keVExpected energy resolution• DEFWHM=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