June-Rong Chen

Water adsorption–desorption on aluminum surface

Abstract Water adsorption–desorption on aluminum surface studied at the Synchrotron Radiation Research Center (SRRC) is described. Both the thermal desorption and the photon stimulated desorption were studied. It was observed that the outgassing behavior of water is quite different from that of the other gases. Experimental results showed that the processes of venting, evacuation and vacuum treatment are sensitive to the water desorption behavior.

Utility optimization for the beam orbit stability at SRRC

At the Taiwan Light Source (TLS), the stability of the electron beam orbit is sensitive to the utility conditions. The beam position showed strong correlation with the temperature while the tunnel temperature variation was more than 0.4/spl deg/C. In this work, the coolant temperature and the air temperature in the storage ring tunnel were tuned to test the sensitivity of the electron beam orbit. The temperature difference of the devices in the TLS might be as high as 10/spl deg/C between the system shutdown and operation. These temperature variations affected the beam stability through some specific routes. Some modeling technique was also applied to identify the correlation factors among the beam position and the utility conditions.

A synchrotron radiation beam-position monitor at the Taiwan Light Source.

A prototype photon-beam-position monitor has been designed, fabricated and tested at the Taiwan Light Source of the Synchrotron Radiation Research Center. Aluminium was chosen as the material of the blade electrodes due to its low atomic number and high thermal conductivity. The resolution of this photon-beam-position monitor was <+/-1 micro m. The sensitivity of the blade electrode has been measured in situ. Results of measurements for bending-magnet light and undulator light with different gaps are described.

Desorption of the NEG‐coated Aluminum Chamber

We first apply the transformation of mixing azimuthal with wrapped coordinate to the 11D M-theory with a stack N M5-branes to find the spacetime of a stack of N D4-branes with magnetic field in 10D IIA string theory, after the Kaluza-Klein reduction. In the near-horizon limit the background becomes the Melvin magnetic field deformed AdS6×S. Although the solution represents the D-branes under the Melvin RR one-form we use a simple observation to see that it also describes the solution of D-branes under the Maxwell magnetic field. As the magnetic field we consider is the part of the background itself we have presented an alternative to previous literature, because our method does not require the assumption of negligible back reaction. Next, we use the found solution to investigate the meson property through D4/D8 system (Sakai-Sugimoto model) and compare it with those studied by other authors. Finally, we present a detailed analysis about the Wilson loop therein and results show that the external Maxwell magnetic field will enhance the quark-antiquark potential.The NEG‐coating, composed of ZrTiV with a lower temperature of activation, has been developed as a large surface getter pump for the aluminum (Al) chamber of small aperture and long length with a very poor conductance. However, the outgas of discharged gases, Ar or Kr, as well as the hydrocarbon molecules inside the NEG‐coated Al chamber has been observed. The desorption of the so‐called inert gases with heavier atomic mass residing inside the chamber results in the potential problem of higher cross section of scattering with the traveling beam hence reduces the life time seriously. To verify the outgas source of CH4, the NEG‐coated Al‐chamber exposed with heavy water (D2O) has been investigated. It shows the D2O and methane are the only outgases from the non‐coated Al chamber exposed with D2O. However, more outgas of CDxHy, CD4, and the C2DxHy complexes have been measured in the case of NEG‐coated Al chamber. Desorption of C2DxHy molecules can be reduced by exposing the NEG‐coated surface with synchrotro...

A differential pumping system for the gas filter of the high flux beamline at SRRC

Abstract A gas filter system is designed for the high flux beam line at SRRC to reduce the intensity of the high order contamination to

Air Temperature Analysis and Control Improvement for the Storage Ring Tunnel

The stability of the electron beam orbit had been observed to be sensitive to the utility conditions. The stability of air temperature in the storage ring tunnel is one of the most critical factors. Accordingly, a series of air conditioning system upgrade studies and projects have been conducted at the Taiwan Light Source (TLS). Computational fluid dynamics (CFD) is applied to simulate the flow field and the spatial temperature distribution in the storage ring tunnel. The circumference and the height of the storage ring tunnel are 120m and 2.8m, respectively. The temperature data and the flow rates at different locations around the storage ring tunnel are collected as the boundary conditions. The k-ε turbulence model is applied to simulate the flow field in the three dimensional space. The global air temperature variation related to time in the storage ring tunnel is currently controlled within ± 0.1oC. However, the temperature difference between two different locations is as high as 2oC. Some measures improving the temperature uniformity will be taken according to the CFD simulated results.

Design and fabrication of aspherical bimorph PZT optics

Abstract Bimorph piezoelectric optics with a third-order-polynomial surface is designed and a prototype is fabricated as active optics. Two pairs of silicon (Si) and lead zirconate titanate (PZT) piezoelectric ceramic are bonded as Si–PZT–PZT-Si together with a multi-electrode or thin film resistor coating used as the control electrode between Si and PZT and metallic films as grounding between the interface of PZT ceramics. A linear voltage is applied to the bimorph PZT optics by probing the control electrodes from a two-channel controllable power supplier. In doing so, the optics surface can achieve a desired third-order-polynomial surface. Reducing hysteresis and creep in bimorph PZT X-ray optics is the only feasible way by inserting an appropriate capacitor in series with bimorph PZT optics to significantly reduce both effects.

Integration Design and Installation of Girder Systems in the Injection Section of Taiwan Photon Source

The electron beam is injected from the end of the transport line into the injection section of the storage ring in Taiwan Photon Source (TPS). A girder system for the injection section has been designed to support AC/DC septum magnets, four kicker magnets (K1–K4), and vacuum chambers. The girder system includes three girders, a Rapson-slide mechanism, and stages for the septum/kicker magnets. To improve the reliability and the stability of the injected electron beam, the girder systems are designed and installed in the injection section of TPS, as described in this chapter. The positioning accuracy of installing three girders and the stages for septum/kicker magnet are, respectively, within 0.3 and 0.05 mm.

Design and Experiment of the Auto-alignment Control System for TPS Storage Ring Girder

The auto-alignment system is designed for aligning the magnet girder system with little manpower and time as well as improving the accuracy of girder system in the whole storage ring simultaneously. The system consists of absolute length gauges between two consecutive girders, laser position-sensitive devices (PSD) between two straight-section girders, and a precision inclination sensor on each girder. The more precise angle and length between two girders obtained from these sensors module, the more precise position that can then be located. A magnet girder system with six cam movers on three pedestals is designed to provide precise adjustments of six axes and align girders automatically driven by six electric motors. This chapter consists of the construction of system, auto-alignment process, and experimental results. In the auto-alignment process, a laser tracker is employed to acquire the data as the feedback one in auto-alignment process to locate the position of girders and to simulate the status of the whole TPS storage ring. Further verification of the proposed technique of auto-alignment based on the results of several experiments in this chapter is merited.

The Position and Correction System of Laser PSD

A laser PSD positioning system is included in the TPS girder auto-alignment system that is designed for aligning and positioning the straight-segment girders of TPS storage ring. The laser PSD positioning system consists of lasers, PSD, and lenses. This chapter describes the process of assembly, installation, adjustment, and the measurement result of the laser PSD system. Installing the laser PSD system consists of several steps. The first step is to assemble lenses and PSD in mechanism, lens PSD module. The tilt angles of lens on the lens PSD module are fine tuned and the PSD position value is adjusted to zero. The positioning fixture is designed and contains six touch sensors (absolute length gauges) for detecting the position of the lens PSD module. The lens PSD module is installed and adjusted on a girder absolute position precisely by the positioning fixture. So each module is adjusted to with equal distance to the vertical and horizontal reference plane of girder. The laser is adjusted according to the position of the PSD. Finally, use the absolute length gauges to correct the PSD. According to the aforementioned process of assembly and all parameters of PSD module, the girder can be aligned and positioned within 20 um precision scale.