Fermilab, Batavia
Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
Characterization of the micropulse bunch lengths and phase stability of the drive laser and the electron beam continue to be of interest at the Fermilab A0 Photoinjector facility. Upgrades to the existing Hamamatsu C5680 streak camera were identified, and initially a synchroscan unit tuned to 81.25 MHz was installed to provide a method for synchronous summing of the micropulses from the drive laser and the optical transition radiation (OTR) generated by the e-beam. A phase-locked delay box was also added to the system to provide phase stability of ~1 ps over tens of minutes. Initial e-beam measurements identified a significant space-charge effect on the bunch length. Recent measurements with a re-optimized transverse emittance allowed the reduction of the micropulse number from 50 to 10 with 1 nC each to obtain a useful streak image. This increased signal also would facilitate dual-sweep operations of the streak camera to explore macropulse effects. Installation of the recently procured dual-sweep module in the mainframe has now been done. Initial commissioning results and sub-macropulse effects in the beams will be presented as available.
Fermilab, Batavia
ANL, Argonne
Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357
Strong enhancements of the optical transition radiation (OTR) signal sampled after bunch compression in the Advanced Photon Source (APS) linac chicane have been observed as has been reported in LCLS injector commissioning. A FIR CTR detector and interferometer were used to monitor the bunch compression process of the PC gun beam down to sub-0.5 ps (FWHM) and correlate the appearance of spatially localized spikes of OTR signal (5 to 10 times brighter than adjacent areas) within the beam image footprint. We also observed that a beam from a thermionic cathode gun with much lower charge per micropulse (but a similar total macropulse charge to the PC gun) showed no enhancement of the OTR signal after compression. Reconstructions of the temporal profiles from the autocorrelations of both beams were performed and will be presented. Spectral-dependence measurements of the enhanced OTR were done initially at the 375-MeV station using a series of bandpass filters inserted before the CCD camera. Tests with an Oriel spectrometer with ICCD readout are now being planned to extend those studies. Discussions of the possible mechanisms for the OTR enhancements will be presented.
JLAB, Newport News, Virginia
CASA, newport news
Fermilab, Batavia
Optical diffraction radiation (ODR) is a promising technique, which could be used for non interceptive beam size measurements at future light sources. An ODR diagnostic station was designed and installed on a CEBAF transfer beam line. The purpose of the setup is to evaluate experimentally the applicability range for an ODR based non interceptive beam size monitor and to collect data to benchmark numerical modeling of the ODR. An extensive set of measurements were made at the electron beam energy of 4.5 GeV. The ODR measurements were made for both pulsed and CW electron beam of up to 80 uA. The wavelength dependence and polarization components of the ODR were studied using a set of insertable bandpass filters and polarizers. The typical transverse beam size during the measurements was ~150 microns. Complete ODR data, wavelength and polarization, were recorded for different beam sizes and intensities. The beam size was also measured with an optical transition radiation (OTR) as well as wire scanner located next to the ODR station. In this contribution we describe the experimental setup and present first results of the measurements with the comparison to the numerical simulations.
Rutgers University, The State University of New Jersey, Piscataway, New Jersey
Fermilab, Batavia
Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy.
An experiment has been developed at the Fermilab A0 Photoinjector Lab to demonstrate the exchange of longitudinal emittance with the horizontal emittance. Our apparatus consists of a 3.9 GHz TM110 deflecting rf cavity placed between two magnetic dogleg channels. The first dogleg generates the needed dispersion to appropriately position the off-momentum electrons in the TM110 cavity. The TM110 cavity reduces the momentum spread and imparts a time dependent transverse kick. The second dogleg finishes the exchange and yields the exchange of the emittances. We report on the measurement of the exchange beamline matrix elements as well as an inital report on measuring the exchange emittances directly.
