BL practice

BL17SU : Instrumentation for Time-resolved Soft X-ray Emission Spectroscopy
1. Introduction
Soft x-ray emission (SXE) spectroscopy is a technique which is applicable to investigation ofelectronic structure of various systems such as solid, surface adsorbate, gas, liquid and solution.
Recently, a time resolving two dimensional position encoder [1] has been applied to the detection
system of the SXE spectrometer [2] installed at BL17SU [3]. This enables us to perform
time-resolved measurement for SXE spectrometry.
In the course, the participants will learn a principle of the position encoder as well as the soft x-ray
emission spectrometer, and gain experience in time-resolved measurements. The course will includealignment and evacuation of the apparatus, sample preparation and introduction to the sample bankchamber and transfer to the main chamber under UHV condition, calibration of the BL
monochromator by measuring some absorption spectra of gaseous target, data acquisition withvarious NIM and CAMAC modules, and measurement of soft x-rays scattered by a Au sample oremitted from unknown materials by the SXE spectrometer. The full menu of the course will last for
two days.
2. Outline of the soft x-ray undulator beamline BL17SU and the experimental apparatus
BL17SU is aimed at advancing the spectroscopic studies for mainly solid state physics andmaterials science using high brilliant soft x-ray undulator radiation. Photoabsorption, photoemission
and SXE spectroscopies are adopted to investigate the electronic structure of various kinds ofmaterials. A novel insertion device ID17, called a multi-polarization-mode undulator, has beendeveloped for BL17SU [4], and ID17 can be operated as a helical, elliptical, pseudo-linear orpseudo-vertical undulator. The intense soft x-ray beam of circularly/linearly polarized light or themixed polarization state of the beam can thus be obtained by changing the operational mode of ID17.
The BL has branched beamlines (branch-a and -b) which can be switched by the pre-mirror and usedalternatively. Each branch has high resolution and highly stabilized monochromator [3,5] and several
end-stations. The available energy is ranged between 300 and 1800 eV. The resolving power E/ΔE ofthe monochromator is higher than 10,000 and the flux is of the order of 1011 photons/s.
In this course, we will utilize the instruments for time-resolved SXE spectroscopy newly installedat Bc station of the branch-b. A flat field spectrometer developed for the SXE spectroscopy [2] isremodeled for the time-resolved measurement. The apparatus consists of the main chamber equippedwith the xyzθ-sample-manipulator, the SXE spectrometer and the sample bank chamber with sample
transfer equipments. The squared DLD is mounted as the detector for the SXE spectrometer. Various
kinds of NIM and CAMAC modules are prepared, and the position of the dispersed soft x-ray isvisualized by encoding all the analog signals from the DLD.
3. Experimental procedure3.1 Alignment of the apparatus.
By using a laser transit, the apparatus will be aligned to the photon beam axis. At this moment,
the apparatus will be under the condition of atmospheric pressure.
3.2 Evacuation of the apparatus.
After the alignment, the apparatus will be sealed and evacuated.
3.3 Calibration of the BL monochromator.
During the evacuation of the apparatus, calibration of the BL monochromator will be performedat the different station, e.g. beam diagnostic station, by measuring some absorption spectra ofgaseous target such as Ne and O2 gas.
3.4 Sample preparation.
Two samples will be used for the course. One is the Au thin film for the adjustment of the SXE
spectrometer, and the other one is unknown sample which is a powdered materials. The
participants will be asked to prepare the pellet of the powder as a sample. In the menu of 3.6,
the participants will examine the unknown materials by measuring the characteristic x-rays
emitted from the sample.
3.5 Adjustment of the DLD position encoder.
Preparation of the electronic circuit, such as various NIM modules, will be performed. All thesignals from the DLD position encoder are fed into the discriminator and the output NIM
signals are fed into the Time-to-Digital Converters (CAMAC TDC).
3.6 Measurements of soft x-ray spectra.
At first, the SXE spectrometer will be calibrated by using the calibrated soft x-rays provided
from the BL monochromator. After the calibration of the SXE spectrometer, the participants willtransfer the unknown sample from the sample bank chamber to the main chamber under theUHV condition. Then the participants will measure the characteristic x-rays emitted from theunknown sample. The energy of the exciting photon beam will be adjusted appropriately and theparticipants will be asked to examine the unknown materials.
3.7 Discussion for the available time-resolved measurement.
At the end of the course, we will discuss about the potential use of the time-resolved SXEspectrometer. Several applications will be introduced.
References[1] Time and position sensitive delay line detector (DLD) with microchannel plates (MCP) ; See, forexample, http://www.roentdek.com/index.html[2] T.Tokushima et al., Surf. Rev. Lett. 9, 503 (2002).
[3] H.Ohashi et al., AIP Proc. 879, 523 (2007).
[4] T.Tanaka et al., Rev. Sci. Instrum. 73, 1724 (2002) ; K.Shirasawa et al., Phys. Rev. ST Accel.
Beams 7, 020702 (2004) ; K.Shirasawa et al., AIP Proc. 705, 203 (2004) ; M.Oura et al., J.
Synchrotron Rad. 14, 483 (2007).
[5] Y.Senba et al., AIP Proc. 879, 718 (2007).