• S. Okuda, T. Kojima, Y. Sakamoto, R. Taniguchi
  Osaka Prefecture University, Sakai

The coherent synchrotron and transition radiation from electron bunches of a linear accelerator (linac) has continuous spectra in a submillimeter to millimeter wavelength range at relatively high peak-intensities. This light source has been applied to absorption spectroscopy by the authors for various kinds of matters with relatively strong light absorbance such as water and aqueous solutions. The other important characteristics of the coherent radiation are picosecond pulsed light and the high peak intensity of the electric field which can be introduced into matters. In our new project the light source using the pulsed coherent synchrotron and transition radiation will be developed by using the electron beams of a 18 MeV S-band electron linac at Osaka Prefecture University (OPU). The pulse shape of the radiation has been evaluated from the shape of the electron bunch. The system of the light source has been optimized and is under construction. The light source will be applied to the pulsed excitation of matters and to the pump-probe experiment using the electron beam and the coherent radiation.

• C. Christou, V.C. Kempson, S.J. Singleton
  Diamond, Oxfordshire

Several modifications have been made to the 100 MeV Diamond Light Source pre-injector linac since initial commissioning in 2005 to improve beam stability and reliability and to increase the scope of operation of the system. Stability enhancements include tighter thermal control of low-level rf electronics, and a modified timing system for gun and linac operation. The linac has been optimised for multibunch filling of the storage ring and for single-bunch top-up operation with gun charge and timing determined by the state of the storage ring fill. Low-energy beam generation has been studied for fault-mode operation using one of the two rf stations, and a study of the options available for Diamond based on routine operation in this mode has been carried out. A summary of operational experience is presented, together with options for future development

• A.H. Lumpkin
  Fermilab, Batavia
• W. Berg, M. Borland, Y.L. Li, S.J. Pasky, N. Sereno
  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.