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Lumpkin, A. H.

Paper Title Page
TUPMN091 Planned Use of Pulsed Crab Cavities for Short X-ray Pulse Generation at the Advanced Photon Source 1127
 
  • M. Borland, J. Carwardine, Y.-C. Chae, P. K. Den Hartog, L. Emery, K. C. Harkay, A. H. Lumpkin, A. Nassiri, V. Sajaev, N. Sereno, G. J. Waldschmidt, B. X. Yang
    ANL, Argonne, Illinois
  • V. A. Dolgashev
    SLAC, Menlo Park, California
 
  Funding: Work supported by the U. S. Department of Energy, Office of Science, Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.

In recent years, we have explored application to the Advanced Photon Source (APS) of Zholents'* crab-cavity-based scheme for production of short x-ray pulses. Work concentrated on using superconducting (SC) cavities in order to have a continuous stream of crabbed bunches and flexibility of operating modes. The challenges of the SC approach are related to the size, cost, and development time of the cavities and associated systems. A good case can be made for a pulsed system** using room-temperature cavities. APS has elected to pursue such a system in the near term, with the SC-based system planned for a later date. This paper describes the motivation for the pulsed system and gives an overview of the planned implementation and issues. Among these are overall configuration options and constraints, cavity design options, frequency choice, cavity design challenges, tolerances, instability issues, and diagnostics plans.

*A. Zholents et al., NIM A 425, 385 (1999).**P. Anfinrud, private communication.

 
TUPMN104 A Design Study for Photon Diagnostics for the APS Storage Ring Short-Pulse X-ray Source 1156
 
  • B. X. Yang, E. M. Dufresne, E. C. Landahl, A. H. Lumpkin
    ANL, Argonne, Illinois
 
  Funding: Work supported by U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.

A short x-ray pulse source based on the crab cavity scheme proposed by Zholents* is being developed at the Advanced Photon Source (APS). Photon diagnostics that visualizes the electron bunches with transverse momentum chirp and verifies the performance of the short x-ray pulse is required. We present a design study for the imaging diagnostics inside and outside of the crab cavity zone, utilizing both x-ray and visible synchrotron radiation. Several design options of monochromatic and polychromatic x-ray optics will be explored for their compatibility with the short-pulse source. The diagnostics outside of the crab cavity zone will be used to map out stable operation parameters of the storage ring with crab cavities, and to perform single-bunch single-pass imaging of the chirped bunch, which facilitates the tuning of the crab cavity rf phase and amplitude so the performance of the short pulse source can be optimized while other users around the ring will not be disturbed.

* A. Zholents et al., NIM A 425, 385 (1999).

 
THOAC02 OTR Imaging of Intense 120 GeV Protons in the NuMI Beamline at FNAL 2639
 
  • V. E. Scarpine, G. R. Tassotto
    Fermilab, Batavia, Illinois
  • A. H. Lumpkin
    ANL, Argonne, Illinois
 
  Funding: Work Supported by the U. S. Department of Energy under Contract No. DE-AC02-CH03000 and Contract No. DE-AC02-06CH11357.

An Optical Transition Radiation (OTR) detector has been installed in the Fermilab NuMI proton beamline, which operates at beam powers of up to ~300 kW, to obtain real-time, spill-by-spill beam profiles for neutrino production. A series of Optical Transition Radiation (OTR) detectors were design, constructed and installed in various beamlines at Fermilab and previous near-field OTR images of lower-intensity 120 GeV and 150 GeV protons with larger transverse beam size have been presented at BIW06 and IEEE NSS06. NuMI OTR images of 120 GeV protons for beam intensities up to 2.8·1013 at a spill rate of 0.5 Hz and small transverse beam size of ~1 mm (σ) are presented here. The NuMI OTR detector uses a 6 micron Kapton foil with 0.12 micron of aluminum which reduces beam scatter by 70% compared to an adjacent Secondary Emission Monitor (SEM). Beam profiles are extracted from the OTR images and compared to the adjacent SEM. The OTR detector provides two-dimensional beam shape such as ellipticity and tilt, as well as complementary beam centroid and beam intensity information. In addition, response of the OTR detector over different intensities and transverse positions is presented.

 
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FRPMN112 Far-Field OTR and ODR Images Produced by 7-GeV Electron Beams at APS 4372
 
  • A. H. Lumpkin, W. Berg, N. Sereno, B. X. Yang, C. Yao
    ANL, Argonne, Illinois
  • D. W. Rule
    NSWC, West Bethesda, Maryland
 
  Funding: Work supported by U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357

We have investigated the angular distribution patterns (far-field focus) of optical transition radiation (OTR) and optical diffraction radiation (ODR) generated by 7-GeV electron beams passing through and near an Al metal plane, respectively. The 70-μrad opening angles of the OTR patterns provide calibration factors for the system. Effects of the upstream quadrupole focusing strength on the patterns as well as polarization effects were observed. The OTR data are compared to an existing OTR single-foil model, while ODR profile results are compared to expressions for single-edge diffraction. ODR was studied with impact parameters of about 1.25 mm, close to the gamma λ?bar value of 1.4 mm for 628-nm radiation. We expect angle-pointing information along the x axis parallel to the mirror edge is available from the single-lobe ODR data as well as divergence information at the sub-100-μrad level. Experimental and model results will be presented.

 
FRPMN113 Initial Far-Field OTR Images Generated by 120-GeV Protons at FNAL 4378
 
  • A. H. Lumpkin
    ANL, Argonne, Illinois
  • V. E. Scarpine, G. R. Tassotto
    Fermilab, Batavia, Illinois
 
  Funding: Work supported by U. S. Department of Energy, Office of Science,under Contract No. DE-AC02-06CH11357 and by U. S. Department of Energy under Contract No. DE-AC02-CH03000.

We have successfully imaged for the first time the angular distribution patterns of optical transition radiation (OTR) generated by 120-GeV proton beams passing through an Al metal plane. These experiments were performed at FNAL with the same chamber, foil, and camera design as with the near-field experiments previously reported. In this case the lens-to-CID-chip separation was remotely adjusted to provide the focus-at-infinity, or far-field optical imaging. The ~8-mrad opening angle of OTR patterns confirm/provide the calibration factors for the system. We also used linear polarizers to select the orthogonal polarization components of the radially polarized OTR. The OTR angular distribution results are compared to an existing analytical model. We show angle pointing information is available from the single-foil OTR data at the sub-mrad level and divergence information at about the 1-mrad level. Data have been obtained in transport lines both before the antiproton production target and before the NuMI target with particle intensities of about 5 to 22 x ·1012. A two-foil interferometer calculation was also performed. Single-foil experimental and modeling results will be presented.

 
FRPMN114 Feasibility of Near-field ODR Imaging of Multi-GeV Electron Beams at CEBAF 4381
 
  • A. H. Lumpkin
    ANL, Argonne, Illinois
  • P. Evtushenko, A. Freyberger
    Jefferson Lab, Newport News, Virginia
  • C. Liu
    PKU/IHIP, Beijing
 
  Funding: Work supported by U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357 and U. S. DOE Contract No. DE-AC05-06OR23177.

We have evaluated the feasibility of using the optical diffraction radiation (ODR) generated as a 1- to 6-GeV CW electron beam passes nearby the edge of a single metal conducting plane as a nonintercepting (NI) relative beam size monitor for CEBAF. Previous experiments were successfully done using near-field imaging on the lower-current, 7-GeV beam at APS, and an analytical model was developed for near-field imaging. Calculations from this model indicate sufficient beam-size sensitivity in the ODR profiles for beam sizes in the 30-50 micron regime as found in the transport lines of CEBAF before the experimental targets. With anticipated beam currents of 100 microamps, the ODR signal from the charge integrated over the video field time should be ~500 times larger than in the APS case. These signal strengths will allow a series of experiments to be done on beam energy dependencies, impact parameters, polarization effects, and wavelength effects that should further elucidate the working regime of this technique and test the model. Plans for the diagnostics station that will also provide reference optical transition radiation (OTR) images will also be described.

 
FRPMS001 Numerical Simulation of Optical Diffraction Radiation from a 7-GeV Beam 3850
 
  • C. Yao, A. H. Lumpkin
    ANL, Argonne, Illinois
  • D. W. Rule
    NSWC, West Bethesda, Maryland
 
  Funding: Work supported by U. S. Department of Energy, Office of Basic Energy Sciences, under Contract No. W-31-109-ENG-38.

Interest in nonintercepting (NI) beam size monitoring for top-up operations at the Advanced Photon Source (APS) motivated our investigations of optical diffraction radiation (ODR) techniques. We have reported our experiment results earlier. In particular, we wanted to monitor the beam size in the booster-to-storage ring (BTS) transport line using near-field ODR. An analytical model was numerically evaluated for the APS BTS beam size cases. In addition, the simulations show that near-field ODR profiles have sensitivity to beam size in the 20- to 50-μm region, which are relevant to X-ray FELs and the international linear collider (ILC). The simulation indicates that the orthogonal polarization component is close to a Gaussian distribution and more sensitive to beam size variations, and therefore is more suitable for beam size measurement. Under some circumstances the parallel polarization component shows a non-Gaussian distribution that is also beam size dependent. This report describes the simulation method, the results, and the comparison with experiment results.

 
FRPMS065 Bunch Length Measurements in SPEAR3 4159
 
  • W. J. Corbett, A. S. Fisher, X. Huang, J. A. Safranek, J. J. Sebek
    SLAC, Menlo Park, California
  • A. H. Lumpkin
    ANL, Argonne, Illinois
  • W. Y. Mok
    Life Imaging Technology, Palo Alto, California
 
  Funding: Work supported by US Department of Energy Contract DE-AC03-76SF00515 and Office of Basic Energy Sciences, Division of Chemical Sciences.

In the nominal SPEAR3 storage ring optics, the natural radiation pulse length is 40ps fwhm per bunch. Due to the double-bend achromat lattice configuration, it is relatively straightforward to reduce the momentum compaction factor (α) and hence reduce the bunch length by modest values. In this paper we present streak camera measurements of the bunch length in the nominal optics, and with ~α/20 and α/50 optics as a function of single-bunch current. The results demonstrate <10ps fwhm radiation pulses with up 5x108 particles/bunch (~100μ amp). Radiation pulse power, bunch length scaling and broadband impedance estimates are discussed.