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

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

ETL ETL 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

ETL ETL Introduction - 1 (1) Industry Microanalysis (EDAX) (2) Astronomy Satellite mission (Astro-E, Constellation-X, XEUS) (3) Biology Optical spectroscopy Advanced ED spectrometer High energy resolution, Fast response time , Large detection area

ETL ETL Introduction - 2 Candidate of advanced X-ray detectors - Microcalorimeter of Transition Edge Sensor (TES) The status of the art Energy resolution - 4.5 eV for 5.89 keV x-ray Response time - ~ 10 2 cps Detection area - ~ 0.1 mm 2 Goal Energy resolution - < 5 eV for 6 keV x-ray Response time - > 10 2 cps Detection area - > 50 mm 2 (7.5 mm x 7.5 mm) Increasing the detection area Array of the TES microcalorimeters

ETL ETL Introduction - 3 Array of the TES microcalorimeters Conventional TES TES Frangible structure Absorber 1. Thin membrane < 1 µ m electrode Membrane <1mm 2. Open space under the membrane ~1mm Substrate Difficult to make large scale array of TESs Improving the robustness New membrane structure - Bridge type membrane

ETL ETL Experiment - 1 Si (1) 1) Fabrication of bridge type membrane SiO 2 1. Cleaning of a SOI wafer to remove a SiN oxide layer in buffered HF. 2. Deposition of SiNx layer(<1 µ m) on (2) the front side of the SOI by plasma- CVD in SH 4 and N 2 gases. Al 3. Deposition and pattering of Al layer (3) on the SiNx layer. 4. RIE etching of SiNx with SF 6 and O 2 gases, and then removing of the Al mask. (4) 5. After the making the TES,absorber, and wires, anisotropic etching of the 30-50 m m SOI layer from the front side in (5) Hydrazine monohydrate solution at 73 ℃ for about 4 hours . Membrane

ETL ETL Experiment - 2 2) Fabrication of TES Au Ti (1) 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. absorber 2. Deposition of 300 nm-thick Au (2) 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 Nb (3) RF-sputtering and forming of electric leads with lift-off technique.

ETL ETL Experiment - 3 TES microcalorimeter Membrane TES SiNX Nb Si SiO2 SiO2 Si Au Si (111) <001> Nb <010> Si (100) SiNX Size TES : 500 µ m x 1000 µ m (100) (111) Absorber : 300 µ m x 300 µ m Membrane : 2100 µ m x 700 µ m Membrane Thickness : 1 µ m SiO 2 SOI wafer : Si(30-50)/SiO 2 (1)/Si(525) in µ m, (100) orientation

ETL ETL Experiment - 4 3) Characteristics of TES microcalorimeter 0.3 Normal resistance 0.25 R N : 0.27 Ω TES : Ti(70 nm)/Au(30 nm) Absorber : Au(300 nm) Resistance( Ω ) 0.2 Bias current: 2 µ A Transition temperature 0.15 T C : 0.43 K Thermal conductance 0.1 G :13 nW/K 0.05 K : 41 nW/K4 0 0.426 0.428 0.430 0.432 0.434 Temperature(K)

ETL ETL Experiment - 5 4) Setup for X-ray measurement Bias resistance SQUID R bisa : 0.1 Ω Modulation SQUID amp gain A SQUID : 600 V/A TES 0.4K RT amp gain A RT : 100 Ω X-ray source : 55 Fe 4.2K K α : 5.89 keV K β : 6.49 keV

ETL ETL Experiment - 6 4) Setup for X-ray measurement - SQUID array N SQUID 200 5.8 pA/ Hz 1/2 S SQUID B SQUID 1 MHz M input 60pH A SQUID 600 V/A 4.2 K T OPERATE SQUID array

ETL ETL Results and Discussion - 1 Feedback curve 220 3.5 Narrow plateau region TES(Ti:70nm Au:30nm) R Bias =0.1 Ω and R 0 =0.27 Ω 200 3 ( ETF region ) of P JOULE ( V Bias ) 180 2.5 Current( µ A) Power(nW) 160 2 140 Large R bisa : 0.1 Ω 1.5 120 1 100 0.5 80 Residual Resistance( R resi ) 60 0 of the bias circuit 0.00 5.00 10.0 15.0 20.0 25.0 30.0 Voltage( µ V) 25 m Ω Bias current( I Bias ) and Joule power( P JOULE ) as a function of bias Voltage( V Bias )

ETL ETL Results and Discussion - 2 X-ray pulse 50 Operation condition 40 V Bisa : 18 µ V Pulse height(mV) 30 I Bias : 70 µ A 20 TES resistance R : 0.25 Ω 10 TES temperature 0 T OPERATE : 0.43 K -100 0 100 200 300 400 Bath temperature Time( µ sec) T BATH : 0.35 K There are two types of pulses : Large and Small pulses

ETL ETL Results and Discussion - 3 Large pulse 50 τ rise : ~3 µ sec 40 Pulse height(mV) τ decay1 : ~10 µ sec 30 τ decay2 : ~130 µ sec 20 10 Fitted curve 0 t + − − × a ( a a exp( )) 1 2 3 τ -100 0 100 200 300 400 rise Time( µ sec) t t − + − ( a exp( ) a exp( )) 4 τ 5 τ decay 1 decay 2

ETL ETL Results and Discussion - 4 Small pulse 20 τ rise : ~10 µ sec 15 Pulse height(mV) τ decay1 : ~130 µ sec 10 Fitted curve 5 t + − − × a ( a a exp( )) 1 2 3 τ 0 rise t − a exp( ) 4 τ -5 -100 0 100 200 300 400 decay 1 Time( µ sec)

ETL ETL Results and Discussion - 5 Estimation of time constants - 1 1. Slow decay time : ~130 µ sec Effective response time ( τ eff ) of TES τ = + αφ ( − = / ( 1 / ) φ = 1 − n 1 ) C G n n ( / ) G nKT T BATH T eff OPERATE OPERATE α ≅ 50, T OPERATE = 0.43 K , T BATH = 0.35 K τ eff = 115 µ sec 2. Rise decay time of large pulses : ~3 µ sec Electrical response time ( τ ele ) of TES τ ele = L/R R = 0.25 Ω , L ≅ 1 µ H τ ele = 4 µ sec

ETL ETL Results and Discussion - 6 Estimation of time constants - 2 3. Fast decay time of large pulses and rise time of small pulses ~10 µ sec 2 X-ray absorption 1 absorber 1. TES X-ray 2. Absorber τ 1 ~10 µ sec Heat flow SiN X membrane TES τ 2 ~130 µ sec Si Time of heat transfer between TES and Absorber Time constant of large pulses :TES to Absorber small pulses : Absorber to TES

ETL ETL 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 X-ray events in the TES 4) Small pulses X-ray events in the absorber

ETL ETL Future Each TES size TES : 500 µ m x 1000 µ m Absorber : 300 µ m x 300 µ m Membrane : 2100 µ m x 700 µ m The total 5 x 5 array size 7 mm x 11 mm