Taiwan Photon Source Research Articles

A novel generation design dipole magnet power supply of booster to storage ring transport line in NSRRC

The Taiwan Light Source (TLS) is a synchrotron radiation facility located in Taiwan. The booster ring at TLS injects electrons into the storage ring, which then circulates the electrons to produce synchrotron radiation for various experiments. The Taiwan Light Source (TLS) has been in service for more than 20 years, and some of the power supplies used in the facility are old and hard to maintain repair and the component are phase-out. The upgrade is specifically aimed at replacing the power supply for the BTS (Booster to Storage ring) transmission line with a new machine. During the regular shunt down time, dipole magnet power supply replacements were completed. The main reason for using the Chroma 62075H-30E power supply is commonality, for this machine is widely used in Taiwan Photon Source (TPS), and the output current of the power supply is paralleled to a dipole magnet. Therefore, a total of 17 power supplies are used in this upgrade planned to be executed. This novel generation upgrade design is important because the power supply for the BTS transmission line is critical for the operation of the facility, as it is responsible for maintaining the electron beam at a stable energy level as it is injected from the booster ring into the storage ring. A more reliable and efficient power supply can help improve the stability and quality of the electron beam, leading to better experimental results and more efficient use of the facility. Overall, this novel generation upgrade design is part of the ongoing effort to modernize and improve the infrastructure of the TLS, ensuring that it remains a state-of-the-art research facility for years to come.

Optimization stability and performance of the TPS storage ring dipole magnet power supply

This article focuses on the current status of the dipole magnet power supply (DMPS) and improvement in the Taiwan Photon Source (TPS) storage ring. The DMPS provides a stable and precise magnetic field for the storage ring operation. Appropriate wiring methods are employed to minimize magnetic field interference across the entire TPS area to meet the demands of high-energy output and overcome the challenges of operating at high currents. The target energy is set at 850 V and 750 A, utilizing a single-pole switching voltage regulator as a high-precision constant current source output structure. The system incorporates a closed control loop that uses the Direct Current Current Transducer (DCCT) to provide current signal feedback to the system. FPGA (Field-Programmable Gate Array) calculates PID (Proportional-Integral-Derivative) compensation values, generating a 2.1 kHz pulse width modulation (PWM) signal to regulate the output current. At the same time, insulated gate bipolar transistor (IGBT) modules are switching components. However, even after several years of practical operation, the stability and performance of the DMPS in the storage ring still require improvements. To enhance long-term output current stability and address peripheral issues, the current TPS utilizes the Beam Orbit Feedback (FOFB) system to suppress and fine-tune the magnetic field and compensate for the impact of temperature drift on the DMPS's output current. This improvement ensures a more stable circulation of the photon beam within the storage ring. By optimizing the temperature control circuit of the main control card, the long-term output current stability has been successfully enhanced to within ± 10 ppm. Simultaneously, the FOFB system reduces uncertainties in adjusting the X-axis beam position, improving beam stability and quality. Furthermore, relevant protective measures have been implemented to ensure robust system operation. Ultimately, these improvement measures have successfully met TPS's stringent requirements for the DMPS, enabling the synchrotron accelerator light source to operate at higher performance levels and fostering advanced scientific research. The results of these upgrades underscore the success of the power supply enhancements, making significant contributions to the overall improvement of the Taiwan Photon Source facility.

Development of bipolar high-current correction magnet power supply for TPS facility

Taiwan Photon Source (TPS) is a globally renowned 3 GeV synchrotron accelerator light source. With a successful decade of operation, various subsystems have continuously improved and maintained an optimal research facility environment. Presently, there is a concerted effort towards energy conservation. This technical report focuses on the future development of the TPS-II Permanent Magnet Trim Coil Power Supply for the correction magnet, emphasizing a Bipole high-current correction magnet power source. According to the prototype specifications, the maximum output current is 20 A with an operating voltage of 48 V. This augmentation increases the amplitude of the magnetic field correction in the permanent magnet-associated Trim core, providing greater flexibility in manufacturing the permanent magnet correction coils. To design a power supply with high current and stability, the system adopts the Danisense DP50-IP-B DC Current Transducers (DCCT) as the current feedback component and Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) as power switches in a full-bridge (H-bridge) configuration. The driving frequency is set at 40 kHz. Analog modulation control circuitry and protective circuits ensure precise control loop modulation. In the power laboratory, a hardware prototype circuit was constructed, featuring a 48 V input voltage, 20 A output current, a maximum power of 960W, and a current ripple component maintained within 100 μA. This experiment validates the control loop design of the prototype, showcasing the ability to achieve rapid and stable output current performance. Using a 1 V input reference signal for small-signal testing, the bandwidth displayed a -3 dB bandwidth of 8.51 kHz. Long-term current stability is within ± 10 ppm, and interface compatibility with the existing TPS correction magnet power source interface allows direct operation within the current system.

The Study and Improvement of Pressure Degradation of Helium Cryogenic System at NSRRC

This paper is aimed at studying and improving the phenomenon of pressure degradation in a helium cryogenic system. There are two 450W helium cryogenic systems for the Taiwan light source (TLS) and one 890W helium cryogenic system for the Taiwan photon source (TPS) housed at the National Synchrotron Radiation Research Center (NSRRC). The TLS helium cryogenic system is used for one superconducting radio frequency (SRF) cavity and five superconducting magnets. The TPS helium cryogenic system is used for two SRF cavities at the present stage. These three helium cryogenic systems have experienced pressure degradation, which reduced their performance and increased liquid nitrogen consumption for precooling over the past few years. A cryogenic adsorber was set up in an effort to capture the impurities, but this made no difference for pressure degradation in the system. The impurities were comprised of not only gas but also moisture. It was found that the cryogenic adsorber was not efficient enough to remove the moisture. This paper presents the study for the phenomena of pressure degradation. A moisture removal system was designed which is also discussed.

From design and construction to operation of the APPLE undulator at TPS

Abstract The APPLE type of Elliptically Polarized Undulator (EPU) not only serves as a crucial circularly polarized light source in existing accelerator facilities but also acts as a standard light source for soft X-rays at the Taiwan Photon Source (TPS). Up to the present, we have autonomously designed, constructed, and operated various EPU configurations. The experience gleaned from the construction of various designs and the choice of material will be outlined in this paper. We also elaborate upon the actions taken to address the adverse effects on the magnetic fields due to the characteristics of non-identical magnets and mechanical deformation. In particular, a method for correction of discrepancies in the magnetic field of the EPU with operation in numerous phase modes employing iron shims is described. In addition, we also discuss the adverse effects on the storage ring that must be dealt with for stable operation of the EPU at the TPS and optimization of the magnetic field during the laboratory construction phase. This paper will further explain management issues related to the susceptibility of the EPU to radiation damage. The comprehensive experience related to the EPU at the TPS, from design and construction to operation will be presented in this paper.

Develop an automated data acquisition system for TPS correction magnet power supply

Taiwan Photon Source is a third-generation 3 GeV synchrotron light source. Since the successful operation of the first beamline in 2013, comprehensive long-term testing and acceptance work has been carried out to ensure the stable operation of various types of correction magnet power supplies, totalling 1038 units. To standardise and save workforce and time for the measurement of correction magnet power supplies, an automated data acquisition system platform for correction magnet power supplies was developed using LabVIEW. This platform integrates control interface cards, high-resolution digital voltmeters, and analysis instruments. It also includes linearization and calibration compensation for the multi-channel direct constant current transformer to ensure simultaneous measurement of 24 magnet power supplies. Furthermore, it can automatically generate test reports in Word format, saving significant human resources and time. This platform has verified TPS correction magnet power supplies before installation, reducing the failure rate. Regarding measurement results, the output current ripple for the DCCT version is within five ppm, while the shunt resistor version is within ten ppm. The long-term current stability is consistently within ten ppm. The development of the fully automated data acquisition system platform and the measurement of 1038 power supplies were completed in four months.

Performance investigation of conduction-cooled cryogenic permanent magnet undulator at high beam currents

A conduction-cooled cryogenic permanent magnet undulator, CU15, with a period length of 15 mm and 133 periods has been successfully developed. This undulator has been operated at the Taiwan Photon Source (TPS) storage ring at a beam current of 500 mA for more than 3 years. In CU15, two cryocoolers are used to cool the PrFeB magnets to 80 K. The effective magnetic field measures 1.33 Tesla for a magnet gap of 4.2 mm, maintaining an rms phase error below 2.6°. The bunch length of the electron beam in TPS is as short as 16 psec, leading to a serious issue with high beam-induced heating in CU15. This report addresses the above issues and provides detailed adaptations of CU15 to operate at a beam current of 500 mA. Published by the American Physical Society 2024

Combination of XEOL, TR-XEOL and HB-T interferometer at the TPS 23A X-ray nanoprobe for exploring quantum materials.

In this study, a combination of X-ray excited optical luminescence (XEOL), time-resolved XEOL (TR-XEOL) and the Hanbury-Brown and Twiss (HB-T) interferometer at the Taiwan Photon Source (TPS) 23A X-ray nanoprobe beamline for exploring quantum materials is demonstrated. On the basis of the excellent spatial resolution rendered using a nano-focused beam, emission distributions of artificial micro-diamonds can be obtained by XEOL maps, and featured emission peaks of a selected local area can be obtained by XEOL spectra. The hybrid bunch mode of the TPS not only provides a sufficiently high peak power density for experiments at each beamline but also permits high-quality temporal domain (∼200 ns) measurements for investigating luminescence dynamics. From TR-XEOL measurements, the decay lifetime of micro-diamonds is determined to be approximately 16 ns. Furthermore, the XEOL spectra of artificial micro-diamonds can be investigated by the HB-T interferometer to identify properties of single-photon sources. The unprecedented strategy of combining XEOL, TR-XEOL and the HB-T interferometer at the X-ray nanoprobe beamline will open new avenues with significant characterization abilities for unraveling the emission mechanisms of single-photon sources for quantum materials.

TLS Fast Orbit Feedback Upgrade

The Orbit Feedback System (OFB) at the Taiwan Light Source (TLS) was implemented two decades ago and has undergone multiple upgrades to enhance its performance. The loop bandwidth was constrained by the available hardware. The system is unable to eliminate perturbations from a fast source. In order to enhance the performance of orbit feedback, the system underwent an upgrade in 2008. The upgrade involved the replacement of the analog-type BPM electronics with digital BPM electronics, as well as the replacement of the corrector power supply with a high-performance switching-type power supply that has a wide bandwidth. Following the commissioning of the Taiwan Photon Source (TPS) in 2015, a decision was made to gradually migrate the control system of the Taiwan Light Source to the Experimental Physics and Industrial Control System (EPICS). This decision was made in order to facilitate resource sharing between the two facilities since EPICS had already been adopted by TPS. The Orbit Feedback System is a revitalized subsystem that now benefits from EPICS support. Additionally, the feedback computation unit has been upgraded to a Field Programmable Gate Array (FPGA), resulting in an increase in the calculating cycle from 2.5 kHz to 10 kHz. This report presents a concise overview of the integration of fast orbit feedback and the outcomes of the orbit stability enhancement following the upgrade.

Numerical analysis on the air conditioning system of the experimental hall at TPS

Taiwan Photon Source (TPS) had delivered the first synchrotron light on the last day of 2014. Installation of 16 beamlines of the first and second phases of TPS beamline project was completed. The third phase project also was launched in 2021. To confront the situation that the experimental hall is more compact, we performed Computational Fluid Dynamic (CFD) simulation to analyse the effects of the air conditioning system and various heat sources to the temperature and flow fields in the experimental hall.

Status and upgrades of radio frequency system at Taiwan Photon Source

In order to meet the upcoming RF power requirements of TPS, a five-year upgrade project to construct a new RF station was completed in early 2022. This new RF station mainly consists of an SRF module, a 300-kW SSPA, an analog LLRF control system, RF transmission components, and accessary cooling systems. Test results of the SRF module and 300-kW SSPA met the expected performances. Also presented are the operation statistics of the two original RF stations and the ongoing upgrades. Meantime between RF failures during TPS user time reached 600 hours in 2022, while the construction and tests on DLLRF control system, power combination of klystron and SSPA, and 2-cell 1.5-GHz SRF module have all progressed well.

Implementation and performance estimation of new archive system for the TLS control system

The TLS (Taiwan Light Source) is a third generation of synchrotron light source that has been operated for more than 25 years, and its control system is a proprietary designed system. The TLS control system maintenance is difficult because of component outage problems. Some parts of the control system are being rejuvenated with the help of the EPICS framework used in the TPS (Taiwan Photon Source) control system to ensure that TLS continues to operate normally, saving both manpower and money. A new EPICS archive system was needed to efficiently record various machine parameters and status information during routine operations. As a result, the EPICS Archiver Appliance has been evaluated as suitable for deploying to archive TLS machine data which encapsulated the PV (Process Variable) channel access. Specific graphical user interfaces and API packages have been supported for quickly retrieving archived data, as well as a plotting function for easy diagnosis. Furthermore, the performance of this new TLS archive system has been estimated, and related system resources will be manually adjusted for better service. The efforts will be summarized in this paper.

Analysis of the bi-bridge topology and power device circuit of the TPS booster dipole power supply

This study primarily discusses a unique topology for constructing a double full bridge circuit. The study establishes a push-pull inverter model and analyses the balance circuit in its architecture. This allows the power supply to initiate the balance circuit and ensures the TPS (Taiwan Photon Source) booster magnet power supply operates smoothly in a safe and balanced voltage region when magnet energy is recovered. We employ the approach of adding Y circuits to mitigate the impact of common mode (CM) noise. Adding a Y circuit effectively suppresses the common-mode noise generation, improving the quality of the output current of the TPS dipole magnet power supply at low currents state and ramping the beam current energy from 150 MeV to 3 GeV. Furthermore, the reproducibility and stability of the injection point can enhance the injection efficiency of the TPS booster magnet power supply. This study presents the results obtained from these efforts.

TPS Fast Orbit Feedback Upgrade

The orbit feedback system for the Taiwan Photon Source (TPS) was delivered in 2014. With the installation of an increasing number of insertion devices, a variety of wide-band disturbances are produced. In 2019, a proposal was put forth to enhance the stability of the orbit through the implementation of the fast orbit feedback (FOFB) system upgrade. The upgrade plan encompasses the revision of the power supply controller and an increase in the feedback computation rate from 10 kHz to 30 kHz. Following the upgrade, the bandwidth of the TPS fast orbit feedback system has been expanded from 250 Hz to 400 Hz in the vertical plane and from 200 Hz to 250 Hz in the horizontal plane. The integrated power spectrum density of the orbit could be reduced by approximately 20% with effective measures.

Performance of a photoelectron momentum microscope in direct- and momentum-space imaging with ultraviolet photon sources.

The Photoelectron-Related Image and Nano-Spectroscopy (PRINS) endstation located at the Taiwan Photon Source beamline 27A2 houses a photoelectron momentum microscope capable of performing direct-space imaging, momentum-space imaging and photoemission spectroscopy with position sensitivity. Here, the performance of this microscope is demonstrated using two in-house photon sources - an Hg lamp and He(I) radiation - on a standard checkerboard-patterned specimen and an Au(111) single crystal, respectively. By analyzing the intensity profile of the edge of the Au patterns, the Rashba-splitting of the Au(111) Shockley surface state at 300 K, and the photoelectron intensity across the Fermi edge at 80 K, the spatial, momentum and energy resolution were estimated to be 50 nm, 0.0172 Å-1 and 26 meV, respectively. Additionally, it is shown that the band structures acquired in either constant energy contour mode or momentum-resolved photoemission spectroscopy mode were in close agreement.

Tuner Loop Based on FPGA for Petra Cavity at TPS Booster Ring

The low-level radio frequency system of the Taiwan Photon Source, TPS, booster ring was replaced by the digital low-level RF system, DLLRF, in 2018. After that, the phase drift compensation loop for energy-saving operation and the tuner loop were also implemented in the DLLRF system sequentially. We used Altera-DE3 to build the core of DLLRF and handle the high-speed ADC/DAC procedure for RF signal sampling. As we con-sider the response time of the tuner, we choose an-other low-cost board, Altera-DE0-Nano, to develop the tuner loop for 5-Cell-Petra-Cavity. It has an eight-channel 12-bits-ADC, 150 ksps, ADC128S022, to detect the positions of two tuners and two transmitted powers sampled from two cells of the 5-Cell-Petra-Cavity for a power balance function. The phase information of for-ward power and cavity gap voltage will come from the Altera-DE3 to tell the tuner loop in the Altera-DE0-Nano whether the cavity is on resonance or not. The tuner loop controls the cavity to work not only at the resonance frequency but also with a balanced electric field distribution. This study presents the tuner loop’s architecture, including the locking resonance frequency and field balance functions. The performance of the field balance function is observed by the archive data of the two tuners positions and two transmit power signals.

Bunch-by-bunch transverse position measurement during injection

Bunch-by-bunch systems have been developed at the Taiwan Light Source and the Taiwan Photon Source to monitor transverse position and filling patterns. The system comprises four channels with a 500 MHz sampling rate synchronized with the accelerator’s radio frequency. It is utilized to diagnose injection transients due to kick mismatch, beam oscillations resulting from damped betatron oscillations and wakefield, and monitor the injection current of each bunch.

Development of linear power operational amplifier power supply with pre-regulated voltage controller for TPS correction magnets

The Taiwan Photon Source (TPS) is a renowned 3 GeV synchrotron accelerator light source. Over the past decade of successful operation, it has demonstrated outstanding performance, notably in average beam trip downtime, meeting international standards. A continuous regimen of scheduled equipment upgrades has been maintained across all subsystems to ensure ongoing improvement and the preservation of an optimal research facility environment. The central focus of this study revolves around the design and realization of a TPS correction magnet power supply employing Linear Power Operational Amplifiers (LPOA) in conjunction with a pre-regulated voltage controller. The power source predominantly features APEX Corporation's PA05 LPOA, characterized by bipolar output, high internal power dissipation, and wide bandwidth. Additionally, a DC Current Transducer (DCCT) was employed as the current feedback element, integrated with the pre-regulator voltage controller to form a closed-loop current modulation circuit, providing the variable voltage required by the LPOA. Through these measures, we have successfully developed an LPOA power supply unit equipped with a pre-regulated voltage controller for TPS correction magnets. The prototype device boasts a maximum output current of ±10 A, operating at 24 V. Validation through control loop design has led to rapid and stable output current performance. The output current ripple is maintained within 100 μA, with a rise time of 75 μs during step response. During frequency response testing utilizing a 0.1 V disturbance signal, the gain margin resides within -3 dB at an 11.2 kHz bandwidth and the phase margin within -45∘ at a 5.1 kHz range. Long-term output current stability is sustained within ten ppm. Finally, a hardware prototype circuit has been constructed in the power supply laboratory, featuring a ±24 V input voltage and ±10 A output current, achieving a maximum rated power of 240 W.

Online bunch-by-bunch position monitoring and analysis at the Taiwan Photon Source

The online bunch-by-bunch position monitor has been established through the utilization of a high-speed analog-to-digital converter, synchronized meticulously with the accelerator's radio frequency. This implementation serves the purpose of refining the alignment of the four injection kickers. A substantial volume of data needs to be managed when dealing with the motion of the bunches. To untangle the intricacies of bunch motion, an independent component analysis has been employed. This method efficiently segregates the bunch motion into discrete sources. The resulting bunch motion is a direct outcome of the linear combination of these distinct sources. Consequently, this approach significantly simplifies the overarching data analysis procedure. Throughout the injection phase, the predominant factors influencing the oscillation of filled bunches originate from three distinct sources. Firstly, there is a contribution arising from the mismatch among the four kickers during their activation period. Additionally, the damped betatron oscillation and the oscillation generated by wake fields constitute the other sources of bunch motion. To comprehend the tune variation in these sources, an examination is conducted through a numerical analysis of fundamental frequencies. Specifically, the tune associated with the betatron oscillation is contingent upon the amplitude of said oscillation. In contrast, the tune corresponding to the wake-field oscillation displays comparably minor fluctuations during both the growing and damping phases.

Ptychography at the Taiwan Photon Source

Ptychography at the Taiwan Photon Source