• C.A. Thomas, I.P.S. Martin, G. Rehm
  Diamond, Oxfordshire

During normal operation of synchrotron third generation light source like Diamond, the measurement of the electron bunch profile, of the order of 10~ps, is perfectly done with a streak camera. However, in 'low alpha' operation, where the momentum compaction factor is reduced in order to shorten the bunch length, the measurement becomes extremely close to the resolution of the camera. In such a case, performing a good measurement and extracting the real information requires a good knowledge of the impulse response of the streak camera. We present analysis and measurement of the contributions to the point spread function of the streak camera: the static point obtained by measuring a focussed beam without any sweep, which can be achieved at best around 5.5 pixels (0.7~ps with the fastest sweep), but also the chirp introduced by refractive optics and a large spectral beam, measured with a spectrograph at 26~fs/nm. Then we discuss short bunch measured in 'low alpha' operation and the agreement between measurements and expectation from theory.

• C. Bloomer, J.R. Brandao-neto, G. Rehm, C.A. Thomas
  Diamond, Oxfordshire

A relatively new development for synchrotron light sources is the concept of producing two independent X-ray beams in a single straight using two canted undulators. Two beams, separated by an angular divergence in the order of 1 mrad, proceed down the same front end before being separated into two experimental hutches. This creates a challenge for the position measurement of the two adjacent X-ray beams in the front end. Traditional four blade tungsten vane XBPMs are an established solution for accurate and reliable monitoring of the position of a single beam, so this approach has been developed to create an eight blade XBPM that is capable of resolving two beams independently. This paper presents first results from Diamond’s I04 and J04 IDs and illustrates the techniques used for position calibration and background subtraction.

• G. Rehm, I.P.S. Martin, A.F.D. Morgan
  Diamond, Oxfordshire
• R. Bartolini, V. Karataev
  JAI, Egham, Surrey

The operation of the Diamond storage ring with short electron bunches using ‘low alpha’ optics for generation of Coherent THz radiation and short X-ray pulses for time-resolved experiments is limited by the onset of microbunch instabilities. We have installed two ultra-fast (time response is about 250 ps) Schottky Barrier Diode Detectors sensitive to radiation within the 3.33-5 mm and 6-9 mm wavelength ranges. Bursts of synchrotron radiation at these wavelengths have been observed to appear periodically above certain thresholds of stored current per bunch. The fast response allows a bunch-by-bunch and turn-by-turn detection of the burst signal, which facilitates study of the bursts’ structure and evolution. In this paper we present our first results for various settings of alpha and also discuss future plans for the modification of a beam port to improve sensitivity of the system.