J. R. Chen

Vacuum chamber for the wiggler of the Taiwan Light Source at the Synchrotron Radiation Research Center

An aluminum vacuum chamber 3 m long and 21.5 mm high was fabricated, tested and installed in the wiggler section of the Taiwan Light Source at the Synchrotron Radiation Research Center. The chamber was made by the extrusion method and machined to a flatness of <±0.1 mm/3 m. The inner aperture included an elliptical channel (17 mm×80 mm) for electron beam and a pumping channel for a nonevaporable getter (NEG) strip. Two heat‐treated Be–Cu springs were used to absorb the thermal expansion of the NEG strip during activation. After installation of the wiggler chamber in the storage ring, a pressure of 0.45 nTorr was reached after an in situ bakeout with NEG activated. The high temperature properties of the Be–Cu spring and the vacuum performance of the complete chamber have been tested. No obvious influence, due to the narrow beam aperture or limited gas conductance to the beam life time was found.

Outgassing behavior on aluminum surfaces: Water in vacuum systems

Several different effects of water in vacuum systems were studied. An outgassing rate measurement system was used to measure outgassing rates for different venting conditions. Both diffusion and desorption phenomena were observed. The drier the venting gas, the more significant the diffusion behavior. From the pressure buildup tests, it was shown that the increasing H2O partial pressure is much less than that of the other gases. More effective surface pumping for water vapor than for the other gases is thought to be the reason. For the outgassing behaviors mentioned, an effort was made to describe the phenomenon quantitatively by using simple models. In addition to the behavior in the static vacuum, water vapor also shows an interesting behavior in the dynamic vacuum. A few results will be discussed.

Vacuum system of the 3 GeV Taiwan photon source

The design and a prototype of the vacuum system of a low-emittance 3 GeV synchrotron light source, the Taiwan photon source (TPS) (with circumference of 518.4 m), are described. The TPS vacuum system has low-outgassing aluminum beam ducts, a low-impedance structure, an oil-less pumping system, and oil-less fabrication. Little dust, a stable mechanical structure, and highly reliable components are achieved for this vacuum system. A prototype (length 14 m) of the TPS vacuum system was fabricated. Two bending-magnet chambers, 4 m long, were made with computer-numerical control machining and lubricated with ethanol to protect the aluminum surface from oil contamination. Cleaning with ozonized water was applied to decrease the rate of photostimulated desorption from the chamber surfaces. Then an automatic welding system is used to implement the side welding seams of bending chambers. The design considerations, the critical factors in fabrication, and the test results of the vacuum system prototype are presented.

Vacuum design for the 3 GeV TPS synchrotron light source

The 3 GeV Taiwan Photon Source (TPS) is a synchrotron light accelerator which is designed for a beam emittance of < 2 nmrad at a beam current of 400 mA. The vacuum system for the electron storage ring provides a pressure of < 1 nTorr for the electron beam with long beam life time and small disturbance from trapped ions. Due to the limited space for the pumps and the poor conductance of the beam ducts, the vacuum chambers should be manufactured with a clean surface of very low outgassing rate. Aluminum alloys vacuum chambers and the structures of confined-pumping for the localized photo-desorption are selected to meet the design requirement. The CNC-machining for the bending chambers in pure alcohol spraying, followed by ozonated water cleaning and TIG welding in clean room, provides a clean surface and simple structure which lowers the outgassing rate and the chamber impedance. Combinations of the lumped non-evaporable getters (NEG) and the sputtering ion pumps are located near the absorbers for higher efficiency of localized pumping capability. Either the NEG-strips or interior NEG-coating will be used for the Undulator chambers for providing a good linear pumping feature. The design concept will be described in this paper. Besides, the simulation of the pressure distribution and some test results of outgassing measurement for the aluminum chambers will be discussed.

Low contamination ultrahigh vacuum system of the Synchrotron Radiation Research Center 1.3 GeV electron storage ring

The vacuum system of the Synchrotron Radiation Research Center 1.3 GeV electron storage ring was designed as a low contamination ultrahigh vacuum system. In addition to the standard treatments for the ultrahigh vacuum components, several contamination reduction methods, such as oil‐free machining processes, completely oil‐free pumping systems, and dust‐controlled installation processes, were adopted in the manufacturing processes. The benefits of the low‐contamination treatments were verified by the resultant fast‐beam cleanup, low degree of dust trapping, and low partial pressures of the carbonaceous residual gases in the vacuum system.

The straight vacuum chambers of the SRRC 1.3 GeV electron storage ring

Abstract The straight vacuum chambers (S-chamber) of the SRRC 1.3 GeV electron storage ring are designed, fabricated and tested. Vacuum pipes, bellows, flanges, pumping ports and most of the other components are made of aluminum. The S-chambers are designed to have the function of reducing radio-frequency ( rf ) impedance and removing the heat created by synchrotron radiation. A stringent tungsten-inert gas (TIG) welding process is performed to minimize the deformations in both longitudinal and transverse directions. In order to achieve uhv, in situ bakeout by tape heaters is adopted. The testing results showed that the designs for removing the baking-related problems work well.

An aluminum vacuum chamber for the bending magnet of the SRRC synchrotron light source

Abstract A bending magnet vacuum chamber of the SRRC synchrotron light source has been studied. The A6061-T6 aluminum alloy was chosen as the chamber material, and a numerical-controlled oil-less machining process was applied for the fabrication. The AES and SIMS surface analysis methods have been applied to analyse the contaminations on the surface of this chamber. After a TIG welding process, the deformation of this chamber was ⪅ 0.3 mm per meter length. The ‘concentrated’ pumping method was designed and a distributed ion pump was also built in this chamber. A static vacuum of ⩽ 1 × 10 −10 torr has been reached after a bakeout of 150°C. In addition to the above-mentioned works, the residual gases of the system and the pumping speeds of the distributed ion pump were also measured.

Effects of the film thickness on the interfacial reaction of Pt/(111)Si

Pt thin films 50–300 A thick were deposited onto the p‐type, (111)‐oriented Si substrate with the substrate kept at 450u2009°C during film deposition, while silicide formations and their microstructures were investigated by transmission electron diffraction and x‐ray diffraction analysis. It was found that for different thicknesses of the deposited Pt films, the silicides were formed in different phases and different microstructures in the as‐deposited sample. β‐Pt2Si was observed in the samples of 50‐ and 200‐A‐thick deposited Pt films, but with different orientations. And if the thickness of the Pt deposited layer was increased to 300 A, the as‐deposited sample will present the formation of the PtSi epitaxial layer, Pt polycrystalline, and the texture polycrystalline of α‐Pt2Si. This film thickness effect is believed to be due to the grain growth and/or grain transformation of various grain orientations at different film thickness depositions.

Secondary ion mass spectroscopy analysis for aluminum surfaces treated by glow discharge cleaning

Glow discharge cleaning treatments on aluminum surfaces were studied by the secondary ion mass spectroscopy method. The cleaning effects of direct current and radio frequency glow discharges with H2 and Ar gases were compared. The elements or compounds of the contamination or reaction depositions were identified from analyses of the mass spectra and energy distribution of the secondary ions. Base material, chemical solvents, sputtered depositions, hydrogen –oxygen–hydroxyls, and hydrocarbons were the five major sources of the secondary ions. The energy distribution curves were similar for secondary ions with similar compound complexity, and the cleaning effects were nearly identical for secondary ions with the same type of origin.

Construction and commissioning of the Synchrotron Radiation Research Center vacuum system

The installation of the vacuum system of the Synchrotron Radiation Research Center 1.3 GeV electron storage ring was completed in January 1993. Both the straight (S‐) chambers and bending (B‐) chambers are made of aluminum alloy. Oil‐less machining processes were adopted in the fabrication of the B‐chambers and some components of the S‐chambers. Stringent welding processes were performed in a clean room in order to get a good welding quality and a clean chamber surface. The pumping system is a combination of several kinds of oil‐free pumps. In the commissioning phase, the photon induced desorption phenomenon was clearly observed. The major desorbed gases are H2, CH4, CO, and CO2. The desorption yields of these gases are described in this paper. An interlock system for the purpose of vacuum safety is also built in the system in order to increase the reliability of the vacuum operation. In the early stage of the commissioning, the malfunction of some ion gauges and quadrupole mass spectrometers were observe...