Gen'ichi Horikoshi

ESR vacuum system for the photon factory

Abstract 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.

New All Aluminum Alloy Vacuum System for the TRISTAN e+e- Storage Accelerator

A new all aluminum alloy vacuum system for TRISTAN e+e- storage accelerator is described. The system is designed to satify such conditions as high reliability, simplicity, low residual radioactivity, impedance matching, low space factor, light weight, standerdization of the components and low cost. Aluminum alloy is chosen to be as material of the vacuum system. The construction of the accumulator ring starts from April 1981.

Vacuum System for the KEK Proton Synchrotron

The construction and characteristic points of the vacuum system of KEK 12 GeV proton synchrotron are reported. The whole system is divided into three, i.e., for the injector and the beam transportation line to the booster, for the booster and transportation line to the main ring and for the main ring. Of these, only the last two vacuum systems will be reported in the following. In the design and construction, many new attempts have been made and some of them will be reported. The designed value of the average pressures in the booster and in the main ring are 4 × 10-4 Pa and 1 × 10-4 Pa respectively. These values correspond to the beam lives of 300 ms (in the booster) and 10 s (in the main ring), for a beam with injection energies of 20 MeV and 500 MeV respectively. Actually, the average pressures of 6 × 10-5 Pa in the booster and 3 × 10-5 Pa in the main ring are accomplished, which are much less than the designed value.

Vacuum System for Tristan Electron-Positron Collider

最 も大 きな 問題 はDIPの カ ソー ド材 料 で あ った. 1986年12月 に先行 して8台(約1000 mmLの 単位電極 を 6連 結 した ものを1台 と呼び この1台 は偏 向マグネ ッ ト 1台 に対応 す る)のAl-DIPの カ ソー ドをTiに 交 換 し た.1月 の運転 でTi-DIPの 排 気特 性 を検 討 した 結果 (Ti-DIPの 特性 については本連合講 演会で発表),す べ てのDIP264台 に つい て交換 したほ うが よい と決断 し 1987年 春の シャッ トダウンに作業 を行 った.次 の問題 は DCセ パ レータの電極構造 であ った.16台 のDCセ パ レ ータは ビームのない場合 は平行平板 電極 に±約90kVを 安定に印加保持する ことができる.と ころが ビームがあ る状態 では2台 が最悪 の場合,±20kVで も異常放 電を 起 こし,DCセ パ レータ として機能 しなか った.こ れは ビームに伴 う高周波壁電流の影響 で,高 電圧導入部 と並

A Simple Analysis of Outgassing Process

Recently, some experimental results show that outgassing rate depends largely on the pumping speed of the system. For complete understanding of these facts, a simplified model was proposed. In the model, we consider only one kind of diffusion process from the inside of the bulk and one kind of adsorption and desorption processes with a sojourn time τ1. Practically, we can only measure net outgassing rate, i.e., the difference of coming out flux and incident one to the surface. When a surface is exposed to the absolute vacuum, the incident flux is zero and the outgassing rate is equal to the coming out flux which is much larger than the practical outgassing rate. The analysis shows that the outgassing rate depends not only on the pumping speed of the system but also on the surface conditions such as the surface density of adsorbed gas molecules and their sojourn time and approaches finally to a value which depends only on the material after a very long time.