Synchrotron Radiation Research Center Research Articles

Cryogenic oxygen deficiency hazard assessment at the National Synchrotron Radiation Research Center

The National Synchrotron Radiation Research Center (NSRRC) uses cryogenic fluids to create a low-temperature cooling environment for equipment and to conduct various experiments. However, exposure to these cryogenic fluids can cause frostbite, hypoxic suffocation, behavioral incapacitation, insanity, and even death in severe cases. To evaluate oxygen deficiency hazard (ODH) in the NSRRC, we adopted the Fermilab assessment methodology and conducted ODH assessments in the Cryogenic Compressor Room, Taiwan Light Source (TLS) Tunnel, and TLS15A hutch. The results of the evaluation of the Cryogenic Compressor Room and TLS Tunnel revealed that the ODH class is 0 both when the exhaust fan is operating normally and when the exhaust fan is damaged. The exhaust equipment in the TLS15A hutch is only for emergency use. Without the emergency exhaust fan, the ODH class in the area is 1. If the emergency exhaust fan is always on, the ODH class is 0. Therefore, we recommend that those in TLS15A should undergo safety education and receive hazard notifications. In addition, we strongly recommend installing oxygen detectors in the beamline hutch to ensure safety.

Respiratory protective equipment fit tests for researchers at the national synchrotron radiation research center

Researchers at the National Synchrotron Radiation Research Center should use respiratory protective equipment to prevent respiratory damage caused by gases, steam, solvents, chemicals, materials containing toxic substances, and oxygen-deficient environments. Those working with organic matter and certain chemical substances and those exposed to occupation dust should use respiratory protective gear to ensure their health. This study conducted qualitative and quantitative fit tests for various mask brands and sizes, namely 3M-9042, N95-9211, P95-8576, and 3M-6200 masks. The gear worn by all 18 participants in the qualitative fit test passed. By contrast, the gear worn by 12 of the 15 participants in the quantitative test passed; the failure of the remaining gear was due to differences in face shape. The N95-9211 mask can be used in three-piece protective gear because it exhibited a tight fit. Additionally, the 3M-6200 negative-pressure half-face mask exhibited the most satisfactory fit and can be used in protective gear.

Development of EUV interference lithography for 25 nm line/space patterns

In this study, we present the performance of an extreme ultraviolet interference lithography (EUV-IL) setup that was reconstructed at Taiwan Light Source 21B2 EUV beamline in the National Synchrotron Radiation Research Center (NSRRC), Taiwan. An easy-to-perform fabrication method to produce a high-quality transmission grating mask and a simple design of experimental setup for EUV-IL were developed. The current EUV-IL setup is capable of fabricating line/space patterns down to 25 nm half-pitch in hydrogen silsesquioxane (HSQ) resist. Preliminary exposure results revealed that optimized slit width and exposure time significantly improved line/space pattern quality. The current EUV-IL tool at NSRRC can be used for nano-patterning and resist screening to advance the next generation of semiconductor devices.

Special issue celebrating Professor Yu Wang's 80th birthday

Prof. Yu Wang [the middle of the front row] with friends and colleagues at her 70th birthday symposium and celebration, 2013 It is our great pleasure to organize this special issue of the Journal of the Chinese Chemical Society (JCCS) dedicated to the occasion of Professor Yu Wang's 80th birthday. We do appreciate all authors' great efforts in this special issue. Professor Wang was born in June 1943 and grew up in Hsinchu, Taiwan. She received her bachelor degree in chemistry from National Taiwan University (NTU) in 1966 and her Ph.D. degree from University of Illinois, USA in 1973. After completing her post-doctoral research at State University of New York Buffalo for 1 year and assistant researcher at National Research Council of Canada for 5 years, Professor Wang returned to Taiwan and took up her teaching post as an associate professor at NTU in 1979. She became a full professor in 1981 and served as the Dean of the College of Science from 2002 to 2005. She retired in 2013 as an Emeritus Professor and continued to be active in the community. In addition, she served as the Director General at Department of Math and Physical Science, NSC (1998–2001), and as the Vice President of Academia Sinica, 2014–2016. Professor Wang is a world-renowned scientist for her frontier research on crystallography and chemistry. Several pioneer works have been accomplished during her research career. Two areas are worth mentioning: Charge density studies by combining highly accurate X-ray diffraction data and relevant molecular calculations lead to obtain the insights of chemical bonding and physical properties. This area is expanded now to Quantum Crystallography. The other is her works in spin crossover system, where she accomplished a single crystal to single-crystal spin transition via photo excitation (Photo Crystallography). She has published more than 300 papers. Because of her excellence in research, Professor Wang was awarded as an academician of Academia Sinica in 2010. In addition to her research, she also made a great deal of contributions to both local and international academic communities. She played an important role in the development of local crystallographic society and was instrumental in helping Taiwan become a member of IUCr since 1996. She is reputed as the “Mother of crystallography in Taiwan.” Over the years, she served on several prestigious crystallographic societies: Chairman of Crystallographic Committee, Academia Sinica, Taipei (1995–2003), Commission Member of CSMD, IUCr (1996–2002), the President of Asian Crystallographic Association (AsCA) (2002–2004), and Chairman of CSMD, IUCr (2005–2008). She also served as the Editor-in-Chief of the Journal of Chinese Chemical Society, co-published by Wiley in 2006–2014. In addition to her scientific achievement, Professor Wang is also an excellent educator. She is the most gifted educator I have ever known. She always gives her students the best ever-ending love and enthusiasm. Being her student is our greatest reward. To celebrate Professor Wang's 80th birthday, we dedicate this special issue of the JCCS to her. There are 30 cutting-edge articles in this issue contributed from her former students, colleagues, and friends over the years. We are grateful to all authors who have endeavored to bring about a refreshing novelty in this special issue. Dr. Kuan-Jiuh Lin Chairman and Lifetime Distinguished Professor Department of Chemistry National Chung Hsing University Dr. Hwo-Shuenn Sheu Scientist National Synchrotron Radiation Research Center Dr. Biing-Chiau Tzeng Professor Department of Chemistry and Biochemistry National Chung Cheng University

The highly efficient protein crystallography beamline TLS 13B1 at the National Synchrotron Radiation Research Center

AbstractSynchrotron protein crystallography (PX) is one of the most powerful and dominant tools for determining the three‐dimensional structures of biological macromolecules. At the National Synchrotron Radiation Research Center, TLS 13B1 is the first dedicated energy‐tunable and highly automated PX beamline for efficiently solving de novo protein structures in Taiwan and has been open for users since September 2005. With remote access, user support services, and annual PX training courses over 17 years, the number of user groups at TLS 13B1 has grown from 11 to 139. In total, 1,429 projects were supported, and 2090 experiments were hosted during 67,846 hr of beamtime. This paper describes the photon source, beamline components, experimental station equipment, beamline software, beamline application process, and results from our users.

An integrated system for user-friendly X-ray intensity attenuation in a wide energy range

For undulator hard X-ray beamlines of a wide energy range, the beam intensity control is often needed to regulate the photon flux impinging on delicate detectors. Despite the capability of state-of-the-art X-ray pixel detectors being greatly advanced recently, the frontier undulator beamlines in synchrotron facilities often carry outstanding photon fluxes that are sometimes too high for certain measurements. Here, we report a developed protocol that allows intensity attenuation of an X-ray beam in the 4-23 keV energy range with flexible attenuation factors; a prototype is installed and tested on the 13A biological small-angle X-ray scattering beamline of the 3 GeV Taiwan Photon Source (TPS) of the National Synchrotron Radiation Research Center, Hsinchu, Taiwan. The intensity attenuation system is modified from a commercially available pneumatically actuated, vacuum-type precision X-ray attenuator of ADC ABS-300; the system provides beam attenuation factors covering 8 orders of intensity attenuation for an X-ray beam in 4-23 keV. This was achieved with selected combinations of 10 sets of metal foils comprising different thicknesses of Al, Ti, Cu, and Ta foils. A user-friendly protocol is established to automatically compare a subscribed attenuation factor with all the possible attenuation factors from the 1024 combinations of the 10 sets of foils in the X-ray energy used, and determine a set of the metal foils having a best-matched attenuation factor. Calculation of beam intensity attenuations with the selected foils is coded with Python and integrated into the Experimental Physics and Industrial Control System (EPICS). The input of an attenuation factor is done through a graphical display of the attenuator system based on the Control System Studio (CSS). The developed X-ray beam attenuation system provides a convenient and intuitive beam intensity control and has the potential to be adopted in future beamlines.

Integrate a high precision scan magnet power supply in NSRRC

This work describes the integration of a high precision power supply in a scan magnet in National Synchrotron Radiation Research Center (NSRRC). Horizontal and vertical energy transmission to the scan magnet are independent. The high precision and sinewave are utilised to produce a smooth circle field. This power supply has an air cooling system and a more protective function to keep the machine and magnet from being damaged. During the scan magnet application, the maximum current is 12.5 A, and the inductor is 30 mH at 20 Hz sine wave. Accordingly, Kecpo BOP 72-14 model with a maximum current of 14 A and maximum output voltage of 72 V is chosen. Finally, an integrated high-precision scan magnet power supply is created in the laboratory. Experimental result shows the output current ripple and bandwidth, with the output current being 14 A and the maximum ripple being 0.45 A. This combination is simple because no resistor is in parallel with the magnet coils. Lastly, this work demonstrates the magnetic field, output current ripple, and frequency variation with output current to prove that this power supply meets the requirements.

Using Synchrotron Techniques, Investigation of Electrochemical Interfaces in Ni-Rich NMC and Sulfide Electrolytes in All-Solid-State Lithium Metal Batteries

a Nano-electrochemistry Laboratory, Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology, Taipei 106, Taiwan, R.O.C b National Synchrotron Radiation Research Center (NSRRC), Hsinchu, 30076, Taiwan, R.O.CIn all-solid-state lithium metal batteries enable long cyclability of high voltage oxides cathode persistent problem for the large scale application as their underprivileged interfacial steadiness in contrast to sulfide solid-state electrolyte. In this context, the interfaces of the solid electrolyte and Ni-rich NMC811 active material are looked upon as interfacial chemical responses induced by delithiation. In this study, we monitor the impedance progress at the unstable electrode|electrolyte interface due to the electrochemical interfacial response and help us understand the complex nature of reactivity and degradation kinetics with the solid-solid interface redox decomposition, which makes decoupling each effect difficult. we investigated the interfacial phenomenon between LPSC and high voltage cathode NMC811. The effects of spontaneous retort by the side of the interface were separated, and the intrinsic electrochemical decomposition of LPSC was quantified. Moreover, we show that the notch of interfacial degradation surges and the presence of oxidation mechanisms. At the higher delithiation stage, the cathode might twitch structural defenselessness and oxygen utter and resulting in further stark degradation. This complex kinetic degradation behavior was investigated at the solid-solid interface in a delithiation NMC811 and SSE based on the local oxidation state of NMC811, and LPSC SE interfacial chemical response. In this work, we used various characterization techniques to investigate the interfacial phenomenon between LPSC|NMC811 combining EIS and advanced synchrotron techniques such as sXAS, XPS, XRF-XANES mapping, and In-situ Raman spectroscopy. Keywords: delithiation, Ni-rich cathode, Sulfide-solid-state electrolyte, interfacial reaction, Synchrotron XPS, XRF.

Microscopic Views of Ge Segregation and Scavenging Ge on Thin Si on Epi-Ge(001)

Si capping layer is the most notable approach used in Ge metal-oxide-semiconductor (MOS);1-2 however, the Ge segregation and diffusion occurred during the growth of Si.3-4 The formation of undesirable GeOx is detrimental to the Ge nMOS reliability.5 This work focuses on using the scavenging process to reduce the segregated Ge atoms and to completely remove GeOx in the high-k/epi-Si/epi-Ge(001). We used high-resolution synchrotron radiation photoelectron spectroscopy (SRPES) to show the detailed development of Ge segregation and scavenging Ge using in-situ film growth, oxidation, and annealing. The Si films in 8Å thickness were grown on the epi-Ge(001) in a semiconductor molecular beam epitaxy (MBE) chamber.2 These samples were in-situ transferred to National Synchrotron Radiation Research Center in Taiwan for electronic structure studies using photoemission. Molecular oxygen was exposed to the epi-Si/epi-Ge(001) surfaces at 300°C in the photoemission chamber. The samples were then in-situ annealed at 500°C for 5 min under an ultra-high vacuum (UHV).The topmost surface of epi-Ge(001) is terminated with Ge-Ge buckled dimers.6 In the case of room-temperature grown amorphous Si (a-Si) film, the intensity of the Ge down-dimer component from the underlying epi-Ge remains as it is. The Ge up-dimer atoms were partly diffused into the a-Si film, and some of them were segregated to the top of the a-Si surface. The epi-Si grown at 260 - 280°C causes the rest of the Ge down-dimer atoms to move to the epi-Si surface to become both segregated Ge (segGe) and diffused Ge (diff-Ge). The growth of Si merely affects the topmost surface, and the Ge atoms in the second layer of the epi-Ge remain intact. A comparison of the amount of GeOx for HfO2/epi-Si/epi-Ge(001) and HfO2/epi-Ge(001) shows that the epi-Si has greatly reduced the amount of GeOx. However, the GeOx, segGe and diff-Ge components are still observed in the HfO2/epi-Si/Ge(001) samples.We have previously reported that three-time scavenging cycles have greatly reduced the amount of segGe and diff-Ge atoms in high-κ/epi-Si/n-Ge(001), thus decreasing electron traps.7 Each scavenging cycle includes room-temperature oxidation followed by thermal annealing. In this study, the oxidation of the as-grown epi-Si/epi-Ge(001) samples was performed at 300°C. It is worth noting that there is no GeOx formation on the surface after the thermal oxidation, which is different from the room-temperature oxidation of the epi-Si/epi-Ge(001) surfaces. In addition, the oxidation at 300°C affects part of the diff-Ge atoms to evaporate from the surface, which is also different from our previous work, where the diff-Ge component shows no change in intensity since the oxidation occurred at room temperature. The subsequent in-situ annealing at 500°C moved the residual Ge-boned Si (diff-Ge) inside the epi-Si to the surface to become part of the segGe atoms. In conclusion, we have used the aforementioned process to further reduce the segregated Ge, and thus the GeOx, on top of the epi-Si/epi-Ge(001).To whom the correspondence is addressed: mhong@phys.ntu.edu.tw (M. Hong), raynien@phys.nthu.edu.tw (J. Kwo), and pi@nsrrc.org.tw (T. W. Pi)AcknowledgmentsThis work is supported by MOST 110-2112-M-002-036-, 110-2622-8-002-014-, 110-2923-M-002-001-, and 110-2112-M-213-012- of the Ministry of Science and Technology in Taiwan.Reference 1 H. Arimura, E. Capogreco, A. Vohra, C. Porret, R. Loo, E. Rosseel, A. Hikavyy, D. Cott, G. Boccardi, L. Witters, G. Eneman, J. Mitard, N. Collaert, and N. Horiguchi, IEEE Int. Electron Devices Meet., 2.1.1−2.1.4 (2020). 2 H. W. Wan, Y. J. Hong, Y. T. Cheng, C. K. Cheng, C. H. Hsu, C. T. Wu, T. W. Pi, J. Kwo, and M. Hong, M., ACS Appl. Electron. Mater. 3, 2164−2169 (2021). 3 R. Loo, H. Arimura, D. Cott, L. Witters, G. Pourtois, A. Schulze, B. Douhard, W. Vanherle, G. Eneman, O. Richard, P. Favia, J. Mitard, D. Mocuta, R. Langer, N. Collaert, ECS J. Solid State Sci. Technol. 7, 66−72 (2018). 4 Y. T. Cheng, H. W. Wan, C. K. Cheng, C. P. Cheng, J. Kwo, M. Hong, T. W. Pi, Appl. Phys. Express 13, 085504 (2020). 5 J. Franco, B. Kaczer, P. J. Roussel, J. Mitard, S. Sioncke, L. Witters, H. Mertens, T. Grasser, G. Groeseneken, IEEE Int. Electron Devices Meet., 15.2.1−15.2.4 (2013). 6 Y. T. Cheng, Y. H. Lin, W. S. Chen, K. Y. Lin, H. W. Wan, C. P. Cheng, H. H. Cheng, J. Kwo, M. Hong, T. W. Pi, Appl. Phys. Express 10, 075701 (2017). 7 Y. T. Cheng, H. W. Wan, T. Y. Chu, T. W. Pi, J. Kwo, M. Hong, ACS Appl. Electron. Mater. 3, 4484-4489 (2021).

Machine Learning and Prediction of Masked Motors With Different Materials Based on Noise Analysis

The effect of noise on the human body has attracted increasing research attention. In particular, many factories generate motor noise pollution, which exposes general workers to noise for extended periods. To solve this problem, masks made of different materials are used for reducing the noise generated by motors. In this study, we attempted to predict the acoustic sound of masked motors. We collected noise level data in decibels for different operation frequencies of motors used at National Synchrotron Radiation Research Center (NSRRC) and developed a machine learning model according to the characteristics of the collected data to simulate the effect of masks on the motor sound. We use the Gradient Boost Model (GBM) as the main learning method because the model is suitable for predicting noise from comparison results of the five models are very common predictive models and may performed as compare method to predict acoustic noise. The results indicated that the prediction accuracy of the GBM was considerably higher than other four traditional machine learning methods (random forests, support vector machine, gaussian processes regression model and multiple linear regression models). Moreover, we used a general multiple linear regression method as the worst method of comparison and conducted time–frequency visualization of the sound for analysis. At NSRRC, we examined the effects of three observation locations and three mask materials, namely wood, metal, and acrylic, on the sound prediction accuracy achieved with the developed model. The highest sound prediction accuracy was obtained behind the motor and under an acrylic mask.

Design a H-bridge low ripple and high bandwidth air core magnet corrector power supply in NSRRC

This paper is the study of a low-current-ripple and high-bandwidth corrector power supply. The main circuit of this power supply is using a full bridge (H-bridge) structure, and the output current through the high-precision direct current current transducers (DCCT) to transfer the reference voltage to the controller. Previous TPS corrector power supply had a 4.7 kHz current bandwidth, and its output current ripple was 100 μA. Such current ripple and bandwidth do not satisfy the requirements of a rapidly orbiting feedback system of air core loading. Therefore, our research team designed a novel prototype power supply with a high bandwidth (more than 10 kHz) and low output current ripple (less than 10 μA) which was developed via a novel topology circuit. The operation frequency of the main power switch's n-type metal-oxide-semiconductor logic of this novel circuit is increased to 245 kHz. Moreover, the output results of the filter inductor and filter capacitor are modified to 80 μH and 2.46 μF, respectively. The prototype power supply bandwidth reached 10.546 kHz and increase of 124% and its output current ripple was lowered below than 5 μA. The properties of this corrector power supply are very important for the beam correction in storage rings. Finally, A circuit with an input voltage of 48 V, a maximum output current of 10 A, and an output power of 400 W is tested in a laboratory to verify the performance of the developed corrector for the National Synchrotron Radiation Research Center.

Optical design and performance of the biological small-angle X-ray scattering beamline at the Taiwan Photon Source.

The optical design and performance of the recently opened 13A biological small-angle X-ray scattering (SAXS) beamline at the 3.0 GeV Taiwan Photon Source of the National Synchrotron Radiation Research Center are reported. The beamline is designed for studies of biological structures and kinetics in a wide range of length and time scales, from angstrom to micrometre and from microsecond to minutes. A 4 m IU24 undulator of the beamline provides high-flux X-rays in the energy range 4.0-23.0 keV. MoB4C double-multilayer and Si(111) double-crystal monochromators (DMM/DCM) are combined on the same rotating platform for a smooth rotation transition from a high-flux beam of ∼4 × 1014 photons s-1 to a high-energy-resolution beam of ΔE/E ≃ 1.5 × 10-4; both modes share a constant beam exit. With a set of Kirkpatrick-Baez (KB) mirrors, the X-ray beam is focused to the farthest SAXS detector position, 52 m from the source. A downstream four-bounce crystal collimator, comprising two sets of Si(311) double crystals arranged in a dispersive configuration, optionally collimate the DCM (vertically diffracted) beam in the horizontal direction for ultra-SAXS with a minimum scattering vector q down to 0.0004 Å-1, which allows resolving ordered d-spacing up to 1 µm. A microbeam, of 10-50 µm beam size, is tailored by a combined set of high-heat-load slits followed by micrometre-precision slits situated at the front-end 15.5 m position. The second set of KB mirrors then focus the beam to the 40 m sample position, with a demagnification ratio of ∼1.5. A detecting system comprising two in-vacuum X-ray pixel detectors is installed to perform synchronized small- and wide-angle X-ray scattering data collections. The observed beamline performance proves the feasibility of having compound features of high flux, microbeam and ultra-SAXS in one beamline.

The new X-ray absorption fine-structure beamline with sub-second time resolution at the Taiwan Photon Source.

The new TPS 44A beamline at the Taiwan Photon Source, located at the National Synchrotron Radiation Research Center, is presented. This beamline is equipped with a new quick-scanning monochromator (Q-Mono), which can provide both conventional step-by-step scans (s-scans) and on-the-fly scans (q-scans) for X-ray absorption fine-structure (XAFS) spectroscopy experiments, including X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine-structure (EXAFS) spectral measurements. Ti and Te K-edge XAFS spectra were used to demonstrate the capability of collecting spectra at the limits of the working energy range. The Ni and Cu K-edge XAFS spectra for a Cu-doped Pt/Ni nanocomposite were acquired to test the performance of the newly commissioned beamline. Pt L3- and Ru K-edge quick-scanning XAFS (QXAFS) spectra for standard Pt and Ru foils, respectively, revealed the stability of the q-scan technique. The results also demonstrated the beamline's ability to collect XAFS spectra on a sub-second timescale. Furthermore, a Zn(s)|Zn2+(aq)|Cu(s) system was tested to indicate that the states of the Zn electrode could be observed in real time for charging and discharging conditions using an in situ/operando setup combined with QXAFS measurements.

Noise Prediction Using Machine Learning with Measurements Analysis

The noise prediction using machine learning is a special study that has recently received increased attention. This is particularly true in workplaces with noise pollution, which increases noise exposure for general laborers. This study attempts to analyze the noise equivalent level (Leq) at the National Synchrotron Radiation Research Center (NSRRC) facility and establish a machine learning model for noise prediction. This study utilized the gradient boosting model (GBM) as the learning model in which past noise measurement records and many other features are integrated as the proposed model makes a prediction. This study analyzed the time duration and frequency of the collected Leq and also investigated the impact of training data selection. The results presented in this paper indicate that the proposed prediction model works well in almost noise sensors and frequencies. Moreover, the model performed especially well in sensor 8 (125 Hz), which was determined to be a serious noise zone in the past noise measurements. The results also show that the root-mean-square-error (RMSE) of the predicted harmful noise was less than 1 dBA and the coefficient of determination (R2) value was greater than 0.7. That is, the working field showed a favorable noise prediction performance using the proposed method. This positive result shows the ability of the proposed approach in noise prediction, thus providing a notification to the laborer to prevent long-term exposure. In addition, the proposed model accurately predicts noise future pollution, which is essential for laborers in high-noise environments. This would keep employees healthy in avoiding noise harmful positions to prevent people from working in that environment.

Regulating Electronic Status of Platinum Nanoparticles by Metal–Organic Frameworks for Selective Catalysis

Selective hydrogenation of alkynes to alkenes remains challenging in the field of catalysis due to the ease of over-hydrogenated of alkynes to alkanes. Favorably, the incorporation of metal nanopar...

High-resolution angle-resolved photoemission study of oxygen adsorbed Fe/MgO(001)**Present address: Synchrotron Radiation Research Center, National Institutes for Quantum and Radiological Science and Technology, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan

We have investigated the electronic states of clean Fe(001) and oxygen adsorbed Fe(001)–p(1 × 1)-O films epitaxially grown on MgO(001) substrates by means of polarization-dependent angle-resolved photoemission spectroscopy (ARPES) and extensive density-functional theory (DFT) calculations. The observed Fermi surfaces and band dispersions of pure Fe near the Fermi level were modified upon oxygen adsorption. By the detailed comparison of ARPES and DFT results of the oxygen adsorbed Fe surface, we have clarified the orbital-dependent p–d hybridization in the topmost and second Fe layers. Furthermore, the observed energy levels and Fermi wave numbers for the oxygen adsorbed Fe surface were deviated from the DFT calculations depending on the orbital characters and momentum directions, indicating an anisotropic interplay of the electron correlation and p–d hybridization effects in the surface region.

Li–Ti Cation Mixing Enhanced Structural and Performance Stability of Li‐Rich Layered Oxide

Adv. Energy Mater. 2019, 9, 1901530 The affiliation information for the National Synchrotron Radiation Research Center was presented incorrectly. The corrected affiliation is, Prof. C.-T. Chen, Dr. S.-C. Liao National Synchrotron Radiation Research Center Hsinchu 30076, Taiwan The authors apologize for any inconvenience caused.

Vertical Test of a 500-MHz SRF Cavity With a Closed-Loop Cryogenic Helium System

A vertical test for a 500-MHz superconducting radio frequency (SRF) cavity succeeded in the RF laboratory of the National Synchrotron Radiation Research Center. The test system, consisting of a vertical test cryostat, an RF power amplifier, a tunable coupler, and a low-level RF control system is integrated with the existing long-distance cryogenic transfer system and radiation shield. Relying neither on a gasbag nor a purifier, the vertical test cryostat is directly connected to the 400-W cryogenic plant that simultaneously provides liquid helium to the SRF module in the Taiwan Light Source. Applying special cleaning, drying, and purging processes, the vaporized helium gas suffers no pollution during the vertical tests. The valve on the return line for the gaseous helium regulates the helium pressure of the vertical test cryostat at an acceptable fluctuation of +/– 100 Pa. The measurement results for a KEKB-type 500-MHz SRF cavity are illustrated herein to demonstrate the integrated performance of this measurement system.

Development of a long trace profiler in situ at National Synchrotron Radiation Research Center.

To achieve an ultrahigh resolution of a beamline for soft X-rays at the Taiwan Photon Source (TPS), the profile of a highly precise grating is required at various curvatures. The slope error could be decreased to 0.1 µrad (rms) at a thermal load with a specially designed bender having 25 actuators. In the meantime, a long-trace profiler (LTP) was developed in situ to monitor the grating profile under a thermal load; it consists of a moving optical head, an air-bearing slide, an adjustable stand, and a glass viewport on the vacuum chamber. In the design of this system, a test chamber with an interior mirror was designed to simulate the chamber in the beamline. To prevent an error induced from a commercial viewport, a precision glass viewport (150CF, flatness 1/150 λ rms at 632.8 nm) was designed. The error induced from the slope error of the glass surface and the vacuum deformation was also simulated. The performance of the optical head of the LTP in situ (ISLTP) has been tested in the metrology laboratory. The sources of error of this LTP including the linearity and the glass viewport were corrected after the measurement. For the beamline measurement, an optical head was mounted outside the vacuum chamber; the measuring beam passed through the glass viewport to measure the grating profile in vacuum. The measurement of the LTP after correction of the above errors yielded a precision about 0.2 µrad (rms). In a preliminary test, an ISLTP was used to measure the grating profile at soft X-ray beamline TPS45A. The measured profile was for the bending mechanism to optimize the slope profile. From the measured energy spectrum, the slope error of the grating was estimated with software for optical simulation to be about 0.3 µrad (rms), consistent with our estimate of the ISLTP. In the future, it will be used to monitor the thermal bump under a large thermal load. In addition, an ISLTP was used to monitor the properties of optical elements-the twist and radius in the beamline during the installation phase.

Study on Thermionic RF Electron Gun after Retuning Process

Relativistic femtosecond electron bunches can be produced from the electron accelerator system at the PBP-CMU Electron Linac Laboratory of the Plasma and Beam Physics (PBP) Research Facility, Chiang Mai University (CMU). A thermionic radio-frequency (RF) gun is used as an electron source for this accelerator. The RF gun has a 1.6-cell standing-wave structure with side-coupling cavity. The 2856 MHz RF wave is transmitted from the klystron to the gun through a waveguide system. So far, two RF guns have been used at our laboratory. The first gun was designed and constructed mostly in Thailand. The second one was constructed at the National Synchrotron Radiation Research Center (NSRRC), Taiwan, R.O.C. It was then transported from the NSRRC to our laboratory and was tested after the cavity retuning process. The low-level and high-level RF measurements were conducted. This gun has a resonant frequency of 2855.68 MHz at 26.2°C with a quality factor of 12264. The high-power RF measurements showed that an optimal operating temperature of the gun was 34°C. The electromagnetic (EM) field distribution inside the gun was simulated by using the 3D-model created with program CST Microwave Studio 2012@. Study of electron beam dynamics in the gun using program PARMELA was done to estimate the beam properties at the gun exit. Moreover, measurements of the beam properties were performed. The results showed that at optimal conditions the RF gun could produce the beam of ∼2 μs (FWHM) pulse width with a charge of 850.1 ± 34.7 nC. The major fraction of the beam has an energy in the range of 1.5-2.5 MeV.