R. Hashimoto, N. Igarashi, R. Kumai, H. Takagi, S. Kishimoto Application of the SOPHIAS Detector to Synchrotron Radiation X-ray Experiments KEK IMSS R. Hashimoto, N. Igarashi, R. Kumai, H. Takagi, S. Kishimoto RIKEN T. Kudo, T. Hatsui

Introduction Development of a pixel detector for X-ray structural analysis. ・ Small angle X-ray scattering (SAXS) experiment for functional thin films. ・ X-ray diffraction (XRD) experiment for functional materials such as ferroelectrics. etc… Area detector using SOI +P -P Crystal, Thin film Precise analysis of position for hydrogen atoms Time response of the domain structure by pulsed external electric field X rays We are developing a pixel detector which is used for X-ray structural analysis, for example small angle X-ray scattering, as it is called SAXS experiment for functional thin films, X-ray diffraction, as it is called XRD experiment for functional materials such as ferroelectrics. The Silicon-On-Insulator (SOI) technology plays a very important roll on our detector. Complementary use of hard and soft X-ray on X-ray diffraction. The Silicon-On-Insulator (SOI) technology plays a very important roll on our detector.

Introduction SOI detector Ground Positive SOI wafer (n-type substrate) This is a schematic view of our detector based on SOI technology called SOI detector. In this figure, the n-type silicon substrate of an SOI wafer was used for sensor part. And the thinner Si layer used for the circuit layer was located on the sensor through the buried oxide layer. Positive bias is applied to back plane. SOI wafer (n-type substrate) Back plane : positive bias

Introduction Main theme of this talk ; SOPHIAS : Developed by RIKEN Data Acquisition Team (Team leader : Takaki Hatsui) for SACLA FEL experiment. → Photon Factory, KEK We are trying to apply the SOPHIAS detector to synchrotron radiation X-ray experiments, such as SAXS or XRD. In this talk, I will introduce the result on SAXS experiment by use of SOPHIAS detector. Now we are trying to apply the new SOI pixel detector SOPHIAS to synchrotron radiation X-ray experiments. SOPHIAS detector is developed by RIKEN data acquisition team for using in SACLA Free Electron Laser experiment. It has a very fine pixel array which consists of 30 micro meter square pixel. We thought this detector is very useful tool for the structural analysis experiment so we started this research. In this talk, I will introduce our result on SAXS experiment by use of SOPHIAS detector.

Main gate Experiments Photon Factory, KEK (KEK/PF) The experiments were done at Photon Factory in KEK so called KEK/PF. This is the photograph of a part of KEK. PF is located here.

Experimental setup @KEK/PF BL-15A2 Small angle X-ray scattering (SAXS) Structural analysis in nanometer scale SOPHIAS Move Sample SOPHIAS Distance from sample to detector : ～3600 mm These photographs show the experimental setup. This is the beam line 15A2 used for SAXS experiment. Structural analysis for any sample which has nanometer scale structure can be done by SAXS experiment. This is SOPHIAS. And moving to right side, SOPHIAS is set at the end of the beam line. Incident X-ray comes from this direction in vacuum and irradiate to a sample. Scattering X-ray also goes in vacuum until just in front of the SOPHIAS. The distance from the sample to SOPHIAS is almost 3600 mm. X-ray

Small angle X-ray scattering (SAXS) Collagen sample SAXS pattern by SOPHIAS a TEM image a : ～64 nm I’ll show you a typical result of the SAXS in which a collagen sample was used. Left figure is an image of collagen obtained by transmission electron microscope (TEM). Collagen is a very famous material. And it is also famous in photon science because it has periodic structure in about 64 nanometer. Right figure is the SAXS pattern obtained by SOPHIAS. The scattering peaks appeared according to collagen’s periodic structure. And peak position on the detector plane depends on the X-ray energy and the distance from sample to detector. Therefore, collagen is often used for the calibration of the scattered angle because of its well known structure. SAXS pattern appeared caused by the periodic structure. → Collagen sample was often used for the scattered angle calibration because of its well known structure.

SOPHIAS detector Developed for FEL experiments. Charge integration type detector 30 μm square pixel 2157×891 pixel array 30.58 mm 65.598mm Pixel array I’ll introduce our detector SOPHIAS. SOPHIAS is a charge integration type Si pixel detector. For one chip, it has a 2157 times 891 pixel array which consists of 30 micro meter square pixel. In this figure, SOPHIAS has 2 chips. One chip size is 65.598 mm times 30.58 mm.

Photon Energy limitation SOPHIAS detector Higher Peak Signal Density Specifications Pixel Size 30 um×30um Pixel Number 1.9 M Chip size 65.598 mm ×30.58 mm Frame Rate 60 frame/sec Noise 180 e-rms Depletion Depth 500 μm @VHV=200V Peak Signal 19 Me-/pixel Photon Energy limitation < 7 keV Gain High : 2.7uV/e Low :0.05uV /e H:L=60:1 These are specifications of SOPHIAS. Except for the 30 micro meter pixel, its wide dynamic range is included in characteristics of SOPHIAS. SOPHIAS has the High gain and the Low gain output. Using both of them, wide dynamic range was realized. The right figure is a graph of pixel area size versus peak signal. The blue lines mean same peak signal per unit area. We can see that SOPHIAS has the very high peak signal. Wide dynamic range was realized by use of High gain and Low gain.

SAXS experiment Diblock copolymer blending with homopolymer Investigation of the micro-phase separation structure → Depending on the molecular weight of blended homopolymer, diblock copolymer melts into various phase. I’ll show you detail of this experiment. The principal of our experiment is investigation of the micro-phase separation structure appearing in the melting state of polymers. This is based on the interests of material science. We use the diblock copolymer blending with homopolymer for a sample. For this kind of polymer, depending on the molecular weight of blended homopolymer, diblock copolymer melts into various micro-phase separation structure. micro-phase separation structures

SAXS experiment Sample : poly(ε-caprolacton)-polybutadiene diblock copolymer /polybutadiene blends Searching for the Frank-Kasper σ phase by SAXS experiment on this sample. We select the poly(ε-caprolacton)-polybutadiene diblock copolymer blending with polybutadiene homopolymer for a sample in this SAXS experiment. One a of the micro-phase separation structure, Frank-Kasper σ phase will appear or not on this diblock copolymer? This is our interests of this experiment. Frank-Kasper σ phase

SAXS experiment EX-ray = 5.7 keV I’ll show you experimental data. The right figure is a SAXS pattern of poly(ε-caprolacton)-polybutadiene diblock copolymer in melting state. And we use 5.7 keV X-ray. The important region is inside of this red line and I expanded this region. Because of this complicated SAXS pattern, a fine pixelated detector is very important for our measurement. Necessity of the fine pixelated detector because of the complicated SAXS pattern measurement.

SAXS experiment Converting to 1D histogram from 2D image by circular integration SOPHIAS ● 30 μm pixel In order to check the peak structure in detail, I converted to 1D histogram from 2D image by circular integration. The horizontal axis means momentum transfer q in nanometer inverse unit. The vertical axis means normalized counts of detected photon. Some peaks were clearly appeared and in particular, these two peaks were located very close together so that it is difficult to resolve them.

SAXS experiment Converting to 1D histogram from 2D image by circular integration SOPHIAS ● 30 μm pixel PILATUS 2M ○ 172 μm pixel I also use another detector PILATUS 2M which has 172 μm square pixel for cross check of data. But it could not resolve these peaks in same experimental setup with SOPHIAS, because of its pixel size. Our result was already published in this paper. → H. Takagi et al., Journal of Physics : Condens. Matter 29 (2017) 204002

SAXS experiment Resolved by SOPHIAS A part of the peak position (410) (330) Resolved by SOPHIAS (202) (212) (411) (331) A part of the peak position and reflection index peak position 0.347 0.357 0.360 0.370 0.382 0.391 0.398 reflection index 410 330 202 212 411 331 222 (222) I summarized a part of the significant peak position corresponding to reflection index. For this experiment, we should measure all of the significant peaks predicted by theory. PILATUS 2M is very useful for measuring wide region like this because it has a large detection area of about 25 cm times 29 cm. But only SOPHIAS could resolve this peak in 330 and 202 peak in this experiment. SOPHIAS data confirmed existence of Frank-Kasper sigma phase on poly(ε-caprolacton)-polybutadiene dibloch copolymer. from H. Takagi et al., Journal of Physics : Condens. Matter 29 (2017) 204002

Summary Application of the SOPHIAS detector to synchrotron radiation X-ray experiments @KEK/PF ・ The ability of the SOPHIAS detector which developed for FEL experiments was not fully confirmed in synchrotron radiation experiments, but we have proved that SOPHIAS was very useful for synchrotron radiation experiments. ・ In SAXS experiment using 5.7 keV X-ray, we succeeded to resolve very close scattering peaks with the fine pixels of 30 μm. This result proved existence of the Frank-Kasper σ phase on poly(ε-caprolacton)-polybutadiene diblock copolymer. Further more, Aiming to the wide dynamic range as well as the fine pixel, we continue further study and optimization of the applicability of SOPHIAS detector to synchrotron radiation experiments.

Thank you for your attention !