Beam diagnostics

For the full characterization of the electron source detailed measurements of transverse and longitudinal phase space properties have to be done. The increased beam energy requires various new diagnostics elements. A list of the diagnostic tools foreseen for PITZ2 is given below:

  • The beam offset at different positions along the beamline has to be known in order to steer the beam onto the ideal orbit as well as for lattice devices alignment studies. For these purposes Beam Position Monitors (BPMs) have to be installed.
  • Faraday Cups (FC) allow absolute bunch charge measurements, at the same time they can serve as beam collector.
  • The transverse electron beam distribution at various longitudinal positions along the beamline has to be determined by means of observation screens and CCD cameras. The increased beam energy allows to use Optical Transition Radiation (OTR) screens. However, Yttrium:Aluminum:Garnet (YAG) screens are suitable for measurements of low intensity and low energy beams (for example, behind a slit-mask or directly after the gun).
  • For cross-checking the profile measurements two wire scanner stations will be installed.
  • The transverse projected emittance can be measured using an Emittance Measurement System (EMSY), composed of slit masks and/or hole masks (pepper pot), and screens 1.5−2 m downstream which are observed by CCD cameras. In an alternative method - a quadrupole scan - the gradient of a quadrupole is varied and the corresponding beam size variation is measured on screens. Later, Twiss parameter analysis yields a beam emittance computation. In order to observe the beam emittance evolution along the beamline, three EMSYs have to be installed: at the place of the smallest emittance (approximately at z=6 m), as well as at the beginning and at the end of the beamline (i.e. at z=4 m and z=12 m).
  • For a non-interceptive beam current measurement a commercial Integrating Current Transformers (ICT) will be used.
  • For the bunch length measurements as well as for the corresponding longitudinal phase space analysis, OTR screens with streak camera readout are needed.
  • For measuring the beam momentum distribution spectrometers are required, consisting of a dipole magnet and a screen in the dispersive section. The image can be recorded by a conventional CCD camera as well as by a streak camera. Two high-energy spectrometers HEDA1 and HEDA2 will be installed downstream to the booster.
  • The slice emittance can be measured by using off-crest acceleration in the booster and a quadrupole in the dispersive arm. A better slice emittance measurement is possible using a RF deflecting cavity. This device is hoped to be realized with external funding from the EU and an own DESY contribution.
  • A complete phase space analysis can be done using a set of several quads and view screens. This phase space tomography module is designed in collaboration with CCLC Daresbury.
  • Beam phase space analysis becomes possible using one out of two OTR screens placed one behind the other. Beam energy, intensity and divergence can be determined by analyzing the interference pattern of forward and backward scattered radiation.