• B.X. Yang, A.H. Lumpkin
  ANL, Argonne, Illinois

The Advanced Photon Source (APS) is a third generation hard x-ray source serving a large user community. In order to characterize the high-brilliance beams, the APS diagnostics beamlines have been developed into a full photon diagnostics suite. We will describe the design and capabilities of the APS visible light imaging line, the bend magnet x-ray pinhole camera, and a unique diagnostics undulator beamline. Their primary functions are to support the APS user operations by providing information on beam sizes (20 - 100 micrometers), divergence (3 – 25 microradians), and bunch length (20 – 50 ps). Through the use of examples, we will show how these complementary imaging tools are used to visualize the electron dynamics and investigate beam instabilities. Special emphasis will be put on the use of undulator radiation, which is uniquely suitable for time-resolved imaging of electron beam with high spatial resolution, and for measurements of longitudinal beam properties such as beam energy spread and momentum compaction.

• C. Yao, M. Borland, A. Grelick, A.H. Lumpkin, N. Sereno
  ANL, Argonne, Illinois

A particle accumulator ring (PAR) is used at the Advanced Photon Source (APS) to collect multiple linac bunches and compress them into a 0.3-ns (rms) single bunch for booster injection. A 9.77-MHz fundamental rf system and a 117.3-MHz harmonic rf system are employed for initial beam capture and bunch length compression. Satellite bunches with very low charge form due to rf phase drifts or beam loading change. These satellites, when injected into the booster and then into the storage ring (SR), cause bunch impurity at three buckets from the target bucket. Storage ring and booster bunch cleaning was tried but proved to be difficult due to the top-up mode of operation in the storage ring and tune drift in the booster synchrotron. Recently we implemented a PAR bunch-cleaning system with tune-modulated harmonic rf knockout. Preliminary tests gave a measured SR bunch purity of better than 10-6, which shows that the cleaning method is feasible and could achieve a bunch purity goal of 10-8. This report describes the system configuration, test results, and system performance.

• V.E. Scarpine, C.W. Lindenmeyer, G. R. Tassotto
  Fermilab, Batavia, Illinois
• A.H. Lumpkin
  ANL, Argonne, Illinois

Optical transition radiation (OTR) detectors are being developed at Fermi National Acceleratory Laboratory (FNAL) as part of the collider Run II upgrade program and as part of the NuMI primary beamline. These detectors are designed to measure 150 GeV antiprotons as well as 120 GeV proton beams over a large range of intensities. Design and development of an OTR detector capable of measuring beam in both directions down to beam intensities of ~5·10⁹ particles for nominal beam sizes is presented. Applications of these OTR detectors as an on-line emittance monitor for both antiproton transfers and reverse-injected protons, as a Tevatron injection profile monitor, and as a high-intensity beam profile monitor for NuMI are discussed. In addition, different types of OTR foils are being evaluated for operation over the intensity range of ~5·10⁹ to over 1·10¹³ particles per pulse and these are described.

• A.H. Lumpkin, W. Berg, N. Sereno, C. Yao
  ANL, Argonne, Illinois

The development of nonintercepting (NI) diagnostics continues to be of interest at the Advanced Photon Source (APS) as well as elsewhere. In the three rings of the APS facility we use optical synchrotron radiation generated as the electron beam transits the dipole magnetic fields as an NI mechanism to image the beam during top-up operations. However, in the straight transport lines an alternative method is needed. Optical diffraction radiation (ODR) is under investigation to monitor 7-GeV beam trajectory and potentially transverse shape in the booster-to-storage ring (BTS) beamline during top-up operations. We have performed our initial measurements with an Al blade/mirror that served as an optical transition radiation (OTR) monitor when fully inserted into the beam and as an ODR monitor when the beam passed near the edge. In the case of ODR, appreciable signal is emitted by the metal when gamma times the reduced ODR wavelength is comparable to the impact parameter, where gamma is the Lorentz factor. Visible light optics and a standard CCD camera could thus be used for a few-mm impact parameter. We attribute the near-field signal for 1.5- to 3.0-mm impact parameters predominately to the ODR mechanism.

• A.H. Lumpkin, B.X. Yang
  ANL, Argonne, Illinois
• F. Sakamoto
  UTNL, Ibaraki

The Advanced Photon Source (APS) is a hard x-ray user facility based on a 7-GeV storage ring (SR). To accommodate the requests of the diverse user community, the APS normally runs with a 24-singlets fill pattern, a hybrid fill with a singlet and eight septuplets, or a 324-singlet fill pattern. In all cases the total stored beam current is 100 mA, with the lattice providing a natural emittance of about 2.5 nm rad. The first two patterns are used with a top-up mode that involves injection of one pulse of ~2.5 nC every two minutes into the designated SR bucket. Since the partition of bunch current varies for the different fills as well as the loading of the rf cavities, dual-sweep streak camera measurements (Hamamatsu model C5680) have been performed to characterize the average and individual bunch lengths in the fill patterns and the phase slew that occurs within the patterns. The bunch lengths vary from 32 ps (σ) within the septuplet to 50 ps (σ) for the singlet in the hybrid fill. The phase slew is significant in the hybrid fill across the eight septuplets. Example streak images of each pattern will be presented and discussed.