Design of the vacuum system for the elliptical multipole wiggler at the Advanced Photon Source

Abstract

A vacuum system for the Advanced Photon Source elliptical multipole wiggler (EMW) that will operate at a pressure of 10 -9 Torr with a storage ring current of 100 mA at 7.0 GeV has been designed and is being fabricated. The major part of the system is a stainless steel chamber with a 66.6 mm by 19.6 mm rectangular cross section. The length of the vacuum chamber is 3100 mm, and the wall thickness is 1.2 mm. Two versions of the vacuum chamber will be produced: with and without distributed nonevaporable getter (NEG) pumping. The version with NEG pumping will have slides on the top and bottom walls to accommodate sintered plates available from SAES. To activate these plates, the entire vacuum chamber will be baked from the outside up to a temperature of 350°C-450°C. Provision for the baking is included in the design of the vacuum system, its support, and in the EMW itself. The complexity introduced into the design by the need for external activation of the NEG plates is eliminated in the design of the second version of the chamber. In this chamber, a sufficiently low outgassing rate may be achieved by extensive surface cleaning and baking in a vacuum furnace (10 -6 Torr) up to a temperature of 950°C as has been achieved at ESRF. Both versions are being pursued in parallel.

Design study of distributed pumping system using multilayer NEG strips for particle accelerators

“…The NEG strips considered here were St707-type NEG strips (ST707/CTAM/30D Strip, SAES Getters SpA, Italy), which had a width and a thickness of 30 mm and approximately 0.3 mm, respectively [62]. This type has been commonly used in many accelerators thus far [24,[27][28][29][30][31][32][33][34][35]37,38]. The total height of the multilayer NEG strips was assumed to be 8 mm, considering the thermal insulation from the beam pipe during activation, the space for supports in the NEG assembly, and the fabrication accuracy of the pumping space.…”

“…A strip-type NEG, on the other hand, can be used anywhere, irrespective of the presence of magnetic fields, and they have been used widely since they were adopted on a large scale in LEP [20,21,26]. NEG strips have been adopted in Spring-8 [24], NSLS [25], APS [27,29], KEKB [28], TLS [30], TEVATRON [35], etc. The DIP and NEG strips have been used together in some cases [36][37][38].…”

“…The commonly used pumps are distributed sputter-ion pumps (DIP) [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] or NEG (Non-Evaporable Getter) pumps [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35]. A DIP is an integrated sputter-ion pump, and it utilizes a magnetic field of bending or quadrupole magnets.…”

Advanced Photon Source experience with vacuum chambers for insertion devices

“…One 12-mm-aperture chamber is used with a 2.4-m-long wiggler (APS 12). One stainless steel chamber has been built and installed for a specialized elliptical multipole wiggler (EMW) [2]. All have operated with beam, and 16 have been coupled with IDS, including the EMW.…”