Thermal Analysis of the Al Window for a New CESR-C Luminosity Monitor

A luminosity monitor using photons from radiative bhabha events at the CLEO interaction point (IP) has been installed in the Cornell Electron Storage Ring (CESR) [1]. A key vacuum and detector component is the photon window/converter whose uniformity and thickness are critical for determining the resolution of the total energy deposited in the segmented luminosity monitor. The window design must accommodate the operational requirements of the new monitor at CLEO-c beam energies of 1.5-2.5 GeV and also provide sufficient safety margin for operation at 5.3 GeV beam energies for Cornell High Energy Synchrotron Source (CHESS) running. During 5.3 GeV operation, intense stripes of synchrotron radiation (SR) from the interaction region (IR) superconducting quadrupole magnets (SC Quads) as well as nearby bending magnets strike the window. During the course of window development, several materials and designs were considered. Thermal stresses were calculated using ANSYS for various beam conditions to guide the cooling design. A window using aluminum (Al) alloy 6061-T6 was ultimately chosen to provide optimal performance for both CLEO-c and CHESS running conditions. The window has been in successful operation since September 2004.