Recent progress with TES microcalorimeters and signal multiplexing J. Ullom NIST NASA GSFC SRON J. Beall R. Doriese W. Duncan L. Ferreira G. Hilton R.

Recent progress with TES microcalorimeters and signal multiplexing

J. UllomNIST

NASA GSFC

SRON

J. BeallR. DorieseW. DuncanL. FerreiraG. HiltonR. HoranskyK. IrwinB. Mates

G. O’NeilN. MillerC. ReintsemaD. SchmidtL. ValeY. XuB. Zink

Transition-edge sensor (TES) calorimetry

Tem

pera

ture

Time

C

EC

G

energy (x-ray)

ConductanceG ThermalC

HeatCapacity

temperature response

0.02

0.04

0.06

095.8 96 96.2

Temperature (mK)

Res

ista

nce

()

I

V SQUIDcurrent amp

thermometer

TES issues• single pixel performance

energy resolution

capture efficiency speed

• multipixel arraysease of fabrication, homogeneity

• stability of operation

• readout of arrays

• expected noise sources:- fluctuations in thermal impedances- Johnson noise

• unexpected noise source:- behaves like white voltage noise

Obstacle to better TES resolution: unexplained noise

L/R roll-off

Johnson noise

phonon noise

unexplained noise

Different TES geometries

additional normal metal features

definition: = (T/R) dR/dT perpendicular bars reduce

Noise vs. geometry: unexplained noise and correlated

• low designs have little unexplained noise

• perpendicular normal features reduce noise and

all data at 60% RN

7

6

5

4

3

2

1

0

Unexplained Noise/Johnson Noise

10008006004002000

standard

parallel&perp

sparsepartial perp

densepartial perp

wedge

dense parallel

islands

#2standard

densefull perp

≈≈ 450 450 ≈≈ 450 450 ≈≈ 500 500 ≈≈ 150 150

≈≈ 4400 ≈≈ 40 40 ≈≈ 1515

SRON parameter study

normal islands and bars …

noise measurements to follow

Design strategy: match E-max to 5.9 keV, lower

= 45C = 0.9 pJ/KM = 1.2-1.4

1.5 m Bi50% at 6 keV261 s

400 m

2.0

1.5

1.0

0.5

0.0

C (pJ/K)

100806040200

25%RN

A:3.2eVB:2.9eV

C:2.4eV

E-max10.2keV

E-max20.6keV

sllerE-max

lrerE-max

X-ray absorbers

simplest absorber = material stacked on TES

need machined collimator to shield streets

what is fill fraction ?

for NxN array, max wires in 1 street = N (near center)

demonstrated: 2 wires & spaces in 3.5 m for N=30, min street width ~ 55 m with litho development, ~ 25 m ?

fill fraction = 67% [83%] for 250 m pixels = 86% [93%] for 700 m pixels

= 90% [95%] for 1 mm pixels

demonstrated: 2.4 eV in 250 m device 2.9 eV in 400 m devicepredict 4.5 eV in 680 m, 6.0 eV in 830 m

element

d for 95% QE at 6 keV

C/m2 [10-19 J/K] size for C = 2.5 pJ/K

Au 3.5 m 240 (at 100 mK) 320 m x 320 m

Bi 6.3 m 5.8 (?) 2080 m x 2080 m

Cu 29.5 m 2900 90 m x 90 m

Sn 7.8 m 1.3 4390 m x 4390 mHgTe, …

BiTES

SiNx

Si

~ 4 eV

(L pix+Lstreet)2

L pix2

X-ray absorbers - mushrooms

very high fill fractionoverhang can shield streetsmore challenging design, fabrication

absorber

SiNx

Si

TES

normal metal - Au

normal metal - heat pipe

Bi

GSFC - 4 m electroplated Au~2.5 eV at 6 keVTc = 65 mK, = 7 ms

GSFC

BiCu, ~4.5 eV at 6 keV

NIST

TES for 100 keV: attach bulk absorber

1 mmSn aborber: QE = 20% at 100 keV

Mo/Cu thermometer

now 27 eV at 103 keV

Arrays: fabrication straightforward

GSFC

NIST

SRONNIST

E = 4.9 eV;Number of counts = 255534;

5825 5850 5875 5900 5925Energy(eV)

0

5000

10000

15000

stnuo C

16 hour acquisition, no gain correction E 10% worse than in short record

3/4 hour acquisition, no gain correctionno detectable drift

TES stability

stable long-term operation possible …

SRON NIST/CSTL

… but cannot yet be taken for granted. Requires close attention to stray RF power, stray magnetic fields, and temperature stability. Also, some dependence on device andbias point. These dependencies not yet understood.

Time-Division SQUID Multiplexing

schematic data stream

...

Measure many TESs in multiplexed test setup

6.25 mm

interfacechip

32:1 multiplexerchip

8 x 8 sensorarray

individualsensor

8- and 16-channel results

8-channel TDM 16-channel TDM

Multiplexed x-ray calorimeter results

128-pixel MUX facility complete

four 32-channel SQUID

MUX chips16 x 16 x-ray array will be tested at the end of June

presently: -ray cal

Arrays lots of data: multiplexed R(T) curves

• variation in transition shape variation in response• we can already engineer the transition width; soon we will engineer the transition smoothness

sensor± (s)

open loop BW (MHz)

E (eV) single muxed

pixels per column

pixels in square array

1000 3.5 3.6 4.0 196 38416

300 12 1.8 2.0 95 9025

50 12 4.5 5.0 32 1024

Future mux performance

presently, cryogenic BW ~1.5 MHz and electronics BW 3 MHz (designed in 1999)

we will increase system BW to 3.5 MHz …- minor adjustments

and then to 12 MHz.- cold series array, electronics redesign

simulated MUX performance:

but …NeXT ?

New SQUIDS!

gradiometric summing coils

gradiometric SQUIDs

asymmetric V-

• mutual inductance optimized for x-ray measurements

• asymmetric V- greater dynamic range & linearity

• gradiometric design less magnetic shielding & crosstalk

(will help system engineering)

• 100 mK testing in June; production run scheduled for July

optimism is in order - TES calorimeters continue to improve

• energy resolutions < 3 eV at 5.9 keV, 27 eV at 103 keV

• very promising results in complex absorber structures - mushrooms: ~ 2.5 eV - attached bulk absorbers: 27 eV (-ray)

• array fabrication feasible- some work ahead to improve homogeneity

• lengthy, stable spectra feasible- some work ahead to make routine

• time-domain SQUID mux works well

> 196 NeXT-like pixels [1 ms] in 1 channel in 2007 ?

> 32 fast pixels [50 s] in 1 channel also very feasible

Conclusions

a TES option forNeXT could be VERY large

does the science casejustify a -ray array ?