ID24 Material Structure Analysis (MSA)

1. Introduction

The Material Structure Analysis (MSA) beamline is a powerful tool specifically designed for High-Resolution Powder Diffraction (HRPD) and X-ray Absorption Fine Structure (XAFS). It will be constructed at the ID24 section of the Korea-4GSR. Operating in the monochromatic 5 ~ 40 keV range, it will receive radiation from an In-Vacuum Undulator (IVU) as its light source. MSA will provide a beam with a low beam divergence of IVU, which allows for reducing the spreading of the diffracted beams from the sample. It is crucial for accurately determining lattice parameters, crystallite size, and strain in the sample, which leads to well-defined diffraction peaks. MSA will be utilized to study structure analysis in various scientific fields including material science, chemistry, physics, life science, and earth science. The Material Structure Analysis beamline is classified and constructed as an industry priority support beamline to respond to the demands of industry fields and to promote manpower in related fields.

2. Scientific objectives

Material properties are significantly correlated to the crystal structure and its changes. The crystal structure consists of an array of unit cells, and understanding these unit cells involves measuring the lattice parameters. Historically, the scientific measurement of lattice parameters has been investigated using X-ray diffraction techniques. The scientific focus of the MSA beamline is to identify crystal structures to demonstrate material properties. This identification relies on X-ray diffraction, which is based on Bragg’s law. By precisely measuring diffraction patterns, researchers can determine the crystal structure of materials, elucidating their properties and behaviors. The MSA beamline offers a natural beam of approximately 2 mm in the vertical direction and 1 mm in the horizontal direction at the sample position, located 75 meters away. This configuration provides high statistical accuracy in experimental results. The experimental equipment is designed to efficiently measure high-resolution diffraction results using high fluxes, allowing data to be collected at an accelerated rate each day. This high efficiency and precision facilitate detailed structural analysis, essential for understanding and optimizing material performance in various applications. The insights gained from this analysis are expected to enhance the performance of battery materials, improve semiconductor design, and contribute to advancements in nanotechnology. Understanding the crystal structure also plays a key role in metallurgy, helping to create stronger and more durable alloys. Moreover, it supports the study of geological samples, providing valuable information for both academic research and practical applications in mining and environmental science.

3. Beamline Requirements for the Insertion Device

The Material Structure Analysis beamline can provide an energy range of 5-40 keV using an In-Vacuum Undulator (IVU). The high-resolution powder diffraction techniques will be used at a fixed energy of 20 keV. The insertion device of Material Structure Analysis beamline is designed to give the highest brilliance and low divergence in the energy range with energy continuity above. The parameter specifications for the insertion device are listed in the table 1. The insertion device has a 24 mm period and a total length of 3 m. The maximum power is that of the beam incident through an opening aperture of 2 × 2 mm2 in front of the first optical device, high heat load mirror.

Table 1. Insertion device parameters

Und ulator	Pe riod	Len gth	:s ub :` g` (m m)	K : sub :m ax	Po wer ( kW)	Power density (kW mrad: sup:-2)	Max. power after FE (kW)
IVU24	24	3	5- 16	2. 747	1 7.9	165	0.419

In order to provide an X-ray Absorption Fine Structure, a beam with energy change or energy bandwidth of 1 keV should be provided to the sample from the undulator. To achieve this, positive tapering is required, which changes the energy by changing the undulator gap or expands the energy bandwidth by increasing the undulator gap interval depending on the total length of undulator length. The Material Structure Analysis beamline provides the beam with the expanded energy bandwidth using the gap scan that allows high brilliance beam without reducing flux. Additionally, the insertion device is equipped with a tapering mode to provide positive tapering as needed.

4. Beamline Requirements for the Front End

The front end of Material Structure Analysis beamline is required to handle a high heat load of the maximum 18 kW. This total power will be controlled with three mask systems, 1 fixed mask and 2 movable masks with water-cooling system. It will feature a keeping aperture size below 1 × 1 mm² at the maximum power in order to minimize a slope error for a vertical beam divergence caused by the heat load in the heat load mirror, which is essential for maintaining optimal performance. Depending on the total power with changing undulator gap size, the aperture size can be adjusted up to ~2 × 2 mm². Further details are referred in the section of ‘Front End’ in this report.

5. Beamline Layout

Beamline Layout

To achieve optimal angular resolution in the MSA, two key factors should be carefully managed: minimizing beam divergence from the optical device and reducing the beam divergence through the mirror system. The design of the MSA is intended to utilize the high flux and low beam divergence characteristics provided by the storage ring and insertion device to do efficiently that.

[Figure 1] Beamline layout of Material Structure Analysis beamline

Beamline component list

Table 2. Major component list of Material Structure Analysis beamline

Distance from Source (m)	Component	Description
0	IVU24
37.4	Attenuator	Water Cooled Diamond
37.9	Diamond screening monitor
39.0	White beam slit
40.8	Horizontal high heat load mirror	In-Ga eutectic cooled Sagittal cylinder collimating mirror Rh 5 nm on Pt 50 nm
41.9	White beam slit
42.2	Diamond screening monitor	Resolution 1 um Beam monitoring
43.5	DCM	VDCM
44.1	Diamond screening monitor	Resolution 1 um Beam monitoring
44.4	Monochromatic beam slit	4-way Slits
44.6	Diamond BPM	Beam position monitor Beam position Feedback with DCM
46.7	Horizontal high harmonic rejection mirror	Horizontal flat mirror high harmonic rejection mirror 3-strip coating (Si, Rh, Pt)
61.5	Nano beam position monitor	Beam position monitor Beam position Feedback with DCM
	Monochromatic beam slit	4-way Slits
	Pre ionization chamber	I0 monitoring
	Attenuator	Different thickness Al
	Monochromatic beam slit	4-way Slits
	Sample position #1	Gas ionization chamber PIPS Energy dispersive fluorescence detector 2D detector
	Sample position #2	3-circle diffractometer Multi-analyzer crystal system Scintillator detector

6. Optics overview

The detailed specifications for the optics are listed in Table 3.

Table 4. Optics specifications of Material Structure Analysis beamline

	HHLM	DCM	HHRM
Distance from source (m)	40.8	43.5	46.7
Incident Angle	2.5 mrad		2.5 mrad
Shape	Sagittal cylinder	Flat	Flat
Tangential Radius (km)	∞
Sagittal Radius (mm)	199.99
Surface normal direction	Horizontal	Vertical	Horizontal
Substrate	Si	Si (111) Si (311)	Si
Coating materials	Rh 5 nm on Pt 50 nm		Si Rh 50 nm Pt 50 nm
Beam size (H×V) @ 30 keV (μm×μm)	1030×1060	1103×1060	1160×1080
Footprint (L×H) (mm×mm)	420×1	16×1	470×1
Substrate size(L×W×H) (mm×mm×mm)	800×50×50	60×25×50	800×50×50
Roughness, σ (r.m.s)	<0.3 nm	<1 μm	<0.3 nm
Slope error (Tangential / sagittal) (μrad, r.m.s)	<1/<5	<1	<1/<0.5
Max total heat load (W)
Max surface heat load (W/mm2)

High Heat Load Mirror (HHLM)

The detailed

Double Crystal Monochromator (DCM)

The detailed

High Harmonic Rejection Mirror (HHRM)

The detailed