X-ray pulse-shape analysis on pulse-shape analysis on X-ray - - PowerPoint PPT Presentation

X-ray X-ray pulse-shape analysis on pulse-shape analysis on bridge-type bridge-type microcalorimeters microcalorimeters with with Ti-Au Ti-Au transition-edge sensors transition-edge sensors

Masahiro Ukibe*a, Keiichi Tanaka b, Fuminori Hirayama a, Taku Mizuki c, Tomotaka Hikosaka d, Toshimitsu Morooka b, Kazuo Chinone b, Ushio Kawabe d, Toshio Nemoto c, Masao Koyanagi a, Masataka Ohkubo a, Naoto Kobayashi a

a Electrotechnical laboratory, b Seiko Instruments Inc., c Univ. of Meiji,

d Chiba Inst. of Tech.

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Story

• Introduction
• Experiment

1) Fabrication of the bridge-type membrane

2) Fabrication of the TES 3) Characteristics of TES microcalorimeter 4) Setup for X-ray measurement

• Results and Discussion
• Summary

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Introduction - 1

ETL ETL (3) Biology Optical spectroscopy (1) Industry Microanalysis (EDAX) (2) Astronomy Satellite mission

(Astro-E, Constellation-X, XEUS)

High energy resolution, Fast response time , Large detection area Advanced ED spectrometer

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Energy resolution - 4.5 eV for 5.89 keV x-ray Response time - ~ 102 cps Detection area - ~ 0.1 mm2

Introduction - 2

Candidate of advanced X-ray detectors

• Microcalorimeter of Transition Edge Sensor (TES)

The status of the art Goal

Energy resolution - < 5 eV for 6 keV x-ray Response time - > 102 cps Detection area - > 50 mm2 (7.5 mm x 7.5 mm)

Increasing the detection area Array of the TES microcalorimeters

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Introduction - 3

Array of the TES microcalorimeters

Membrane Absorber electrode TES Substrate <1mm ~1mm

Conventional TES Frangible structure

• 1. Thin membrane < 1µm
• 2. Open space under the membrane

Difficult to make large scale array of TESs

Improving the robustness

New membrane structure - Bridge type membrane

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Experiment - 1

1) Fabrication of bridge type membrane

• 1. Cleaning of a SOI wafer to remove a
• xide layer in buffered HF.
• 2. Deposition of SiNx layer(<1µm) on

the front side of the SOI by plasma- CVD in SH4 and N2 gases.

• 3. Deposition and pattering of Al layer
• n the SiNx layer.
• 4. RIE etching of SiNx with SF6 and O2

gases, and then removing of the Al mask.

• 5. After the making the TES,absorber,

and wires, anisotropic etching of the SOI layer from the front side in Hydrazine monohydrate solution at 73℃ for about 4 hours.

Al (3) (4) SiN (2) Si SiO 2 (1) (5) Membrane 30-50 m m

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Experiment - 2

2) Fabrication of TES

• 1. Deposition of Ti(70 nm) and Au(30 nm)

films on the SOI wafer by RF- sputtering and patterning by 1% HF and KI+I solutions, respectively.

• 2. Deposition of 300 nm-thick Au

absorber layer on the Ti/Au bilayer by RF-sputtering and patterning by lift-off technique.

• 3. Deposition of 200 nm-thick Nb film by

RF-sputtering and forming of electric leads with lift-off technique. Nb (3) Ti Au (1) absorber (2)

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Experiment - 3

TES microcalorimeter

SiO2 SiO2 SiNX SiNX Au Nb Nb TES Si Si

(100) (111) <010> <001>

Si (111) Si (100)

SiO2

Membrane

Size TES : 500 µm x 1000 µm Absorber : 300 µm x 300 µm Membrane : 2100 µm x 700 µm Membrane Thickness : 1 µm SOI wafer : Si(30-50)/SiO2(1)/Si(525) in µm, (100) orientation

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Experiment - 4

3) Characteristics of TES microcalorimeter

0.05 0.1 0.15 0.2 0.25 0.3 0.426 0.428 0.430 0.432 0.434

Resistance(Ω) Temperature(K)

TES : Ti(70 nm)/Au(30 nm) Absorber : Au(300 nm) Bias current: 2µA

Normal resistance RN : 0.27 Ω Transition temperature TC : 0.43 K Thermal conductance G :13 nW/K K : 41 nW/K4

4) Setup for X-ray measurement

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Experiment - 5

Ω TES SQUID Modulation 0.4K 4.2K

Bias resistance Rbisa : 0.1 Ω SQUID amp gain ASQUID : 600 V/A RT amp gain ART : 100 X-ray source :55Fe Kα : 5.89 keV Kβ : 6.49 keV

4) Setup for X-ray measurement - SQUID array

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Experiment - 6

SQUID array

NSQUID 200 S SQUID 5.8 pA/ Hz1/2 B SQUID 1 MHz ASQUID 600 V/A TOPERATE 4.2 K Minput 60pH

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Results and Discussion - 1

60 80 100 120 140 160 180 200 220 0.5 1 1.5 2 2.5 3 3.5 0.00 5.00 10.0 15.0 20.0 25.0 30.0

Current(µA) Power(nW) Voltage(µV)

TES(Ti:70nm Au:30nm) RBias=0.1Ω and R0=0.27Ω

Bias current(IBias) and Joule power(PJOULE) as a function of bias Voltage(VBias)

Narrow plateau region (ETF region) of PJOULE(VBias)

Feedback curve

Residual Resistance(Rresi)

• f the bias circuit

25 mΩ Large Rbisa : 0.1 Ω

10 20 30 40 50

• 100

100 200 300 400

Pulse height(mV) Time(µsec)

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Results and Discussion - 2

X-ray pulse

VBisa : 18 µV IBias : 70 µA TES resistance R : 0.25 Ω TES temperature TOPERATE : 0.43 K Bath temperature TBATH : 0.35 K Operation condition

There are two types of pulses : Large and Small pulses

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Results and Discussion - 3

Large pulse

)) exp( ) exp( ( )) exp( (

2 5 1 4 3 2 1 decay decay rise

t a t a t a a a τ τ τ − + − × − − +

10 20 30 40 50

• 100

100 200 300 400

Pulse height(mV) Time(µsec)

τrise : ~3 µsec τdecay1 : ~10 µsec τdecay2 : ~130 µsec

Fitted curve

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Results and Discussion - 4

Small pulse

• 5

5 10 15 20

• 100

100 200 300 400

Pulse height(mV) Time(µsec)

Fitted curve

τrise : ~10 µsec τdecay1 : ~130 µsec

) exp( )) exp( (

1 4 3 2 1 decay rise

t a t a a a τ τ − × − − +

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Results and Discussion - 5

Estimation of time constants - 1

) / 1 ( / n G C

eff

αφ τ + =

n OPERATE BATH T

T ) / ( 1− = φ

) 1 ( −

=

n OPERATE

nKT G

• 1. Slow decay time : ~130 µsec

Effective response time (τeff) of TES α ≅ 50, TOPERATE = 0.43 K ,TBATH = 0.35 K

τeff = 115 µsec

• 2. Rise decay time of large pulses : ~3 µsec

Electrical response time (τele) of TES R = 0.25 Ω, L ≅ 1 µH

τele = L/R τele = 4 µsec

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Results and Discussion - 6

Estimation of time constants - 2

• 3. Fast decay time of large pulses and rise time of small pulses

~10 µsec

Time of heat transfer between TES and Absorber

Time constant of large pulses :TES to Absorber small pulses : Absorber to TES

absorber TES SiN X membrane Si 2 1

X-ray absorption 1. TES

• 2. Absorber

X-ray Heat flow

τ1 ~10 µsec τ2 ~130 µsec

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Summary

• We have fabricated the bridge-type TES

microcalorimeters .

(Ti(70 nm)/Au(30 nm) bilayer TES and Au(300 nm) absorber)

• 5.9 keV X-ray was measurement with 200-series

array of SQUIDs .

• X-ray pulses are put into two categories.

1) Large pulse :Large pulse height,

Fast rise and two decay time 2) Small pulse :Small pulse height, Slow rise and one decay time 3) Large pulses 4) Small pulses

X-ray events in the TES X-ray events in the absorber

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Future

Each TES size TES : 500 µm x 1000 µm Absorber : 300 µm x 300 µm Membrane : 2100 µm x 700 µm

The total 5 x 5 array size 7 mm x 11 mm