Distributed Ion Pumps Research Articles

ESR vacuum system for the photon factory

The vacuum system for the electron storage ring in the Photon Factory project is now under construction. In the beginning, we chose aluminum as the predominant material for the beam duct because of its cooling and forming properties, and ICF flanges for the connections because of its high reliability. These choices compelled us to employ some kind of transition material. Our tests showed that the transition between aluminum alloy (Al) and stainless steel (SUS) can be made either by using an Al-SUS clad plate (by explosion- and diffusion-bonding) or TIG welding with Ag and Ni plates in the spaces between. The vacuum system forms an elliptical ring with circumference of 187 m, and is mainly composed of three kinds of beam ducts and their pumping units. A B-type duct made of Al is installed at every bending magnet section, and has a passage for the distributed ion pump (DIP) along it inner arc wall. Q-type ducts can be classified into two kinds of straight ducts, types a and type b. Type-a duct made of Al is partially indented for the in-situ Ar discharge cleaning electrode, while type-b duct is made of SUS without any additional component. About 28 DIP units, 48 sputter ion pumps and 6 units of roughing pump will be installed around the ring. The design of the rough pumping units is in progress.

Vacuum system for national synchrotron light source

This paper describes the vacuum system for the National Synchrotron Light Source (NSLS) which is now under construction at Brookhaven National Laboratory (BNL). The system will consist of an electron linac, booster, vuv and x-ray storage rings, and up to 44 experimental beam lines. The pressures will range from 10−7 Torr in the linac and booster, to 10−10 Torr (without beam) in the storage rings. Stringent quality control and cleaning procedures are necessary to reduce the adverse effects of hydrocarbon contamination on optical elements which are used for beam handling. This thought is also reflected in the selection of materials, pumps, and other vacuum components, as well as in fabrication techniques. Sputter ion pumps are used throughout with distributed ion pumps and titanium sublimination pumps on the storage rings. Rough pumping is done with liquid-nitrogen-trapped turbomolecular pumps. In situ argon glow discharge conditioning is planned for the storage rings to reduce the desorption due to synchrotron radiation.

Synchrotron-radiation-induced heating effects in the PEP storage ring vacuum system

The advent of large high-energy storage rings has facilitated the need for more detailed analysis of synchrotron radiation interactions and related thermal effects. In the PEP storage ring, a maximum of 5 MW of synchrotron radiation with a critical energy of 44 keV will interact with 2200 m of vacuum hardware. A Monte Carlo based computer code, EGS, was employed to follow electromagnetic reactions of the synchrotron radiation through various computerized models of the vacuum system. The computer simulated structures with hundreds of discrete regions and varying materials. Results showed that typically 70% of the synchrotron power was absorbed in incident surfaces and 20% was scattered outside the vacuum vessel. The remaining power was deposited in varied vacuum components. Sensitive PEP ring components, particularly distributed ion pumps, were subsequently designed to minimize power absorption and to maximize cooling effects. Other thermal calculations were employed to design for minimal wall temperatures in areas of direct synchrotron radiation incidence.

23. The vacuum system for the Daresbury synchrotron radiation source

At the Daresbury Laboratory a new facility is being built for research using synchrotron radiation. The source will be a 2 GeV 1 A electron storage ring of about 30 m dia, which can accommodate up to 12 beam lines radiating tangentially from it. The ultra-high vacuum in the storage ring will be maintained by ion and titanium sublimation pumps in the straight sections and distributed ion pumps in the bending magnet chambers. For adequate beam lifetime and for tolerable bremsstrahfung down each beam line a working pressure of 10 −9 torr for CO is required. To reach this pressure a number of measures will be necessary to obtain low enough desorption rates from photo-electrons produced by up to 255 kW of synchrotron radiation.