No abstract

The effects of audio sidebands from the main rf of the NSLS VUV storage ring on beam motion and specifically on spectral reproducibility in the infrared region were investigated. For this spectral region it is advantageous to use Michelson interferometers because of their high throughput (Jacquinot advantage). A second advantage is that interferometers inherently give a multiplex or Felgett advantage, since one is always looking at all the wavelengths for all of the measuring time, even though there is only one detector. In such instruments it is beneficial to scan the moving mirror at a fast rate so that any mechanical or other low-frequency noise shows up as a slow modulation in the interferogram and disappears altogether in the Fourier transform from the spectral region of interest. However, audio-frequency sidebands appear from the rf energy restoring cavity as noise on the beam. These always occur at multiples of 60 Hz and can thus be readily identified. They can also be confirmed by changing the mirror velocity which changes where they appear in the spectra in a predictable way. In the present work, spectra were measured while simultaneously reducing and shifting the sidebands in the rf and thus the effects were correlated and ultimately eliminated as a source of noise. Ultimately reproducibilities of <1% in 15 s of scanning time across the entire spectral region from 800 to 4000 cm−1 with a sample throughput of only 10−10 m2 sr were achieved.

Ab s tractWe describe a global closed orbit feedback experiment, based upon a real time harmonic analysis of both the orbit movement and the correction magnetic fields. The feedback forces the coefficients of a few harmonics near the betatron tune to vanish, and significantly improves the global orbit stability. We present the result of the experiment in the W ring using 4 detectors and 4 trims, in which maximum observed displacement was reduced by a factor of between 3 and 4 .

The National Synchrotron Light Source at BNL was the first dedicated light source facility and it has now operated for more than 20 years. During this time the user community has grown to more than 2400 users annually. To insure that this vibrant user community has access to the highest quality photon beams, the NSLS is pursuing the design of a new ultra-high brightness (_1021) electron storage ring, tailored to the 0.3-20 KeV photon energy range. We present our preliminary design and review the critical accelerator physics design issues.

The NSLS storage rings use sets of four button electrodes to determine the transverse position of the stored electron beam in the vacuum chamber. By means of GaAs switches, the 211 MHz component of the induced signals on each of the four buttons is m e a s u r e d in t u r n b y a s i n g l e amplifier/detector channel. These signals are then stored in four sample and hold circuits. The measurement cycle is repeated at a rate of 40 Mz.The required sums and difference of these signals are obtained by analog means. The results are normalized with respect to beam intensity by "servoing" the gain of the amplifier/detector channel such that the sum of the signals from the four buttons is maintained at a fixed value.