| AVS 64th International Symposium & Exhibition | |
| Vacuum Technology Division | Tuesday Sessions |
| Session VT-TuM |
| Session: | Large Vacuum Systems |
| Presenter: | Xianghong Liu, Cornell Laboratory for Accelerator-Based Sciences and Education |
| Authors: | X. Liu, Cornell Laboratory for Accelerator-Based Sciences and Education S. Barret, Cornell Laboratory for Accelerator-Based Sciences and Education D.C. Burke, Cornell Laboratory for Accelerator-Based Sciences and Education J.V. Conway, Cornell Laboratory for Accelerator-Based Sciences and Education A.T. Holic, Cornell Laboratory for Accelerator-Based Sciences and Education Y. Li, Cornell Laboratory for Accelerator-Based Sciences and Education A. Lyndaker, Cornell Laboratory for Accelerator-Based Sciences and Education |
| Correspondent: | Click to Email |
A sextant of Cornell Electron Storage Ring (CESR) will be upgraded with Double Bend Achromat (DBA) lattice and CHESS Compact Undulators (CCUs) to significantly boost the performance of Cornell High Energy Synchrotron Source (CHESS). A lot of efforts are being made in preparation for the final installation in late 2018 for this upgrade project, dubbed CHESS-U. With this upgrade, CESR will be converted from a counter-propagating two-beam ring to a single-beam ring. The beam energy will be increased from 5.3 GeV to 6 GeV, and the beam current for normal operation will be increased from 120 mA to 200 mA. Because of the geometrical constraints from the magnets, the beampipe aperture of this new section is 52mm (horizontal) by 22mm (vertical), which is much smaller than the rest of CESR. The vacuum pumping for this new section will be different too, consisting of a combination of Non-Evaporable Getter (NEG) strips, modular NEG pumps, and ion pumps.
The beam pipes are mainly made of three types of aluminum extrusions, fitting inside quadrupole magnets, dipole magnets, and undulators respectively. All extrusions have cooling water channels to handle the thermal load from synchrotron radiation. The same channels are also used for vacuum hot-water bake-out. Dipole extrusions are formed to the correct bending radius by stretch forming in a softer temper, and heat treated to higher temper after forming. With required space available, the dipole extrusion includes an ante-chamber for NEG strip (SAES St 707) pumping. The NEG strip is activated by resistive heating to about 400°C for half an hour. The electrically insulating support mechanism of the NEG strip is adapted from the design used in APS. Instead of being built from extrusions, the dipole chamber where the X-ray beam exits is made of two machined halves that are welded together; a cylindrical crotch is inserted at the flared end of this chamber to absorb approximately 4 kW of synchrotron radiation.
In this presentation, we will give an overview of the design of the vacuum system, and report the estimated pressure profile based on Molflow+ calculations, some design details of major components, results from NEG strip pumping tests, and progress in vacuum chamber productions.