Improved SR extraction chamber for KEKB LER SR monitor

We have recently replaced the synchrotron light extraction chamber for the KEKB Low Energy Ring (LER) SR monitor. The beam pipe was changed to copper to minimize resistive-wall heating, and the optical apertures were made as small as permitted by light extraction requirements in order to reduce HOM power leakage. The new chamber shows almost none of the heating problems of the old chamber, and previous problems with the orientation of the extraction mirror changing due to heat expansion of the beam pipe have been essentially eliminated. The design and performance of the new chamber are presented.