BL17SU High efficiency photon analyzer
問い合わせ番号
INS-0000000325
High efficiency photon analyzer (A3 station)
A progress in the study of the electronic structure of solids using soft X-ray emission has lead our interest to the electronic structure of liquid materials. In this experimental station, we focus on two types of soft X-ray emission experiments: microscopic investigation of a liquid itself and a metal center in aqueous metalloproteins. We can directly investigate the electronic structure of liquids as well as functional metal centers in a bioactive metalloprotein. A representative of the former is water, where chemical reactions take place for many processes. An example of the latter is myoglobin. Myoglobin is cast as hydrogen in proteins. As well as intensive studies on its structure, many focus on the electronic structure of the iron-porphyrin complex in many types of myoglobins. However, it is still very difficult to directly observe the Fe 3d levels that are related to the function of myoglobin.
To approach the electronic structure of liquid materials, we have developed a liquid cell with an external pumping system to circulate liquid in a tube that passes by a thin (150nm) Si3N4 membrane. The membrane isolates the liquid in atmospheric pressure from a high vacuum. The incident photon passing through the membrane interacts with the liquid and the emitted photon again passes through the membrane. We can obtain damage-free soft X-ray emission spectra by the sample circulation. As soft X-rays are insensitive to the electric and magnetic fields, effect of external fields on liquid will be future projects. For metalloproteins and tiny amount of liquids we have developed a sample freezing system with a rotation disk. During experiments frozen samples on the disk are placed close to the thin Si3N4 membrane and scanned against the incident soft X-ray by the rotation of the disk to obtain damege-free spectra. Inside the sample chamber pure helium gas is circulated to increase transmission of incident and emitted soft X-rays.
Schematic view of the total system with High Efficiency Photon Analyzer 2 (HEPA2)
The high efficiency soft X-ray emission spectrometer (HEPA2) has been developed from a prototypical HEPA that is installed in the BL27SU-C3 station. HEPA2 has a varied line spacing cylindrical grating for flat field focusing, a back-illuminated CCD detector with a linear drive for soft X-ray detection, and no entrance slit for high detection efficiency. We have obtained extremely focused beam by placing a post focusing mirror very close (0.5m) to the focal point in order to gain the reduction ratio. The vertical spot size of around 5μm FWHM has been achieved and utilized to potentiate high detection efficiency and high energy resolution.
A liquid flow system with a quartz cell attached to the main chamber.
A sample rapid freezing system for metalloproteins and tiny amount of solutions
Typical energy range and the energy resolution estimated by a ray-tracing program developed for HEPA2. The energy resolution depends on the vertical spot size of the incident beam at the focused position.