First Results from Thermal Kinetic Inductance Detectors ...

First Results from

Thermal Kinetic Inductance Detectors:

Highly Multiplexible Bolometric

MKIDs for X-ray Spectroscopy

G. Ulbricht, B.A. Mazin, P. Szypryt, A. B. Walter, C. Bockstiegel

Department of Physics, University of California, Santa Barbara, CA 93106, USA

LTD-16, Grenoble, July 21, 2015

Thermal Kinetic Inductance Detectors for X-Ray Spectroscopy G. Ulbricht, B.A. Mazin, P. Szypryt, A. B. Walter, C. Bockstiegel


Why TKIDs for X-ray detection?

TKIDs

Thermal Kinetic Inductance Detectors (TKIDs):

· single pixel energy resolution an utilize frequency domain multiplexing

· usable in a big energy / wavelength range

· can utilize frequency domain multiplexing

· no read noise

· ……… promising as

X-ray detectors!

TKID vs. TES:

TES: · impressive energy resolution

· high time resolution

· multiplexing is complex and

challenging

TKID: · comparable time resolution

· much easier to multiplex

· energy resolution: …..

ideal where spatial resolution is required!


TKID design

TKIDs

Many X-ray photons would penetrate the

superconductor

Microcalorimeter: inductor & absorber on

a free floating Si3N4 membrane


TKIDs

TKID design

: sub-stoichiometric TiNx


superconductor




TKIDs

TKID design


: Si3N4 (etched with XeF2)


superconductor




TKIDs

TKID design



: absorber (Ta or Au)


superconductor




TKIDs

TKID design





superconductor




TKIDs

TKID design




: Nb feedline & ground plane

Mushroom shaped absorbers planned,

current simple absorbers just to reduce

prototype complexity.

Bridges: 0.25 x 2 µm2 cross section

140 µm long


Single photon pulses

Data analysis


Single photon pulses

Data analysis


Analysing max. pulse height doesn’t work.

Data analysis

140 150 160pulse max. [degrees]

no

. o

f e

ve

nts

140 150 160pulse max. [degrees]

no

. o

f e

ve

nts

pulse maximum [degrees]


Data analysis

Pulse rise time depends on absorption location.


Why fit pulses?

Pulse fitting


Pulse fitting

Why fit pulses?


Pulse fitting

Why fit pulses?

free parameters in pulse model: photon arrival time rise time

fall time max. membrane temperature


Pulse model: resonance frequency over T

Pulse fitting


Pulse model: phase shift over frequency

Pulse fitting

as measured

after feedline subtraction


Pulse model: assumed temperature behaviour

Pulse fitting


Pulse fitting



Pulse fitting



Pulse model construction

Pulse fitting

base temperature

increased temperature


Pulse fitting

Pulse model construction

Resolution of 75 eV at 5.9 keV, despite significant design flaws in first TKID prototype


Energy resolution still restrained by saturation

Achieved energy resolution


Resonator saturation

Interaction between thermal design and critical temperature



Interaction between thermal design and critical temperature


Resonator sensitivity



Wrong thermal design


too small heat capacity ΔTmembrane = 150 – 200 mK


Wrong thermal design + high sensitivity = saturation


Simple extrapolation: We should be able to resolve

below 10 eV at 5.9 keV by eliminating saturation.


How to eliminate saturation?

eliminating saturation:

reduce Qi:

reduces best achievable resolution

increase TiNx Tc:


reduces heat capacity

increase measurement temperature:

already near upper limit

increases noise

reduce membrane heat capacity:

issues with Au absorber but


…..

measure below resonance frequency:


eliminating saturation:

reduce Qi:


increase TiNx Tc:


reduces heat capacity

increase measurement temperature:

already near upper limit

increases noise

reduce membrane heat capacity:

issues with Au absorber but


…..

measure below resonance frequency:


How to eliminate saturation?



Measurement below resonance.

driving a TKID below resonance frequency:



No longer saturated but still high sensitivity.



More challenging data analysis.

Work in progress.

Δf = 0 kHz Δf = -140 kHz

Δf = -540 kHz Δf = -340 kHz


Many thanks to:

Everybody involved

Mazin group at UCSB:

Ben Mazin

Seth Meeker Matt Strader

Paul Szypryt Alex Walter Clint Bockstiegel

Giulia Collura


First Results from Thermal Kinetic Inductance Detectors ...

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