Synchrotron Radiation Vacuum Chamber Installation and Beam Size

Knowing the coordinates of both the aperture M,N and the mask G,H, we can now use equation (1) to calculate the radiation angles and hence derive the size of the total fan and its angle. According to our experience in order to guarantee a full size fan it is desirable to make: ß ap ¿ 1.2 ß m, where ßm = beam through the water mask aperture. At the NSLS we almost always have full size beam in even numbered ports for which ßap = 1.22 ß m, however for odd ports, where the relationship is: ßap = 1.08 ßm, we typically extract only about 70 mrad instead of the expected 80 mrad.