T. Lefevre

Sub-micrometer transverse beam size diagnostics using optical transition radiation

Optical transition radiation (OTR) arising when a relativistic charged particle crosses a boundary between two media with different optical properties is widely used as a tool for diagnostics of particle beams in modern accelerator facilities. The resolution of the beam profile monitors based on OTR depends on different effects of the optical system such as spherical and chromatic aberrations and diffraction. In this paper we present a systematic study of the different optical effects influencing the OTR beam profile monitor resolution. Obtained results have shown that such monitors can be used for sub-micrometer beam profile diagnostics. Further improvements and studies of the monitor are discussed.

Zemax Simulations of Transition and Diffraction Radiation

Charged particle beam diagnostics is a key task in modern and future accelerator installations. The diagnostic tools are practically the eyes of the operators. Precision and resolution of the diagnostic equipment are crucial to define the performance. Transition and Diffraction Radiation (TR and DR) are widely used for electron beam parameter monitoring. However, the precision and resolution of those devices are determined by how well the production, transportation and detection of these phenomena are understood. This paper reports on initial simulations of TR and DR spatial characteristics. A good consistency with theory is demonstrated. Also, optical system alignment issues are discussed.

Performance of the AWAKE Proton Beam Line Beam Position Measurement System at CERN

The Advanced Proton Driven Plasma Wakefield Acceleration Experiment (AWAKE), based at CERN, explores the use of a proton driven plasma wake-field to accelerate electrons at high energies over short distances. This paper introduces the Beam Position Measurement (BPM) system of the proton beamline and its performance. This BPM system is composed of 21 dual plane button pickups distributed along the 700m long transfer line from the CERN Super Proton Synchrotron (SPS) extraction point to beyond the plasma cell. The electrical pulses from the pickups are converted into analogue signals proportional to the displacement of the beam using logarithmic amplifiers, giving the system a high dynamic range (>50 dB). These signals are digitized and processed by an FPGA-based front-end card featuring an ADC sampling at 40MSps. Each time a bunch is detected, the intensity and position data is sent over 1km of copper cable to surface electronics through a serial link at 10Mbps. There, the data is further processed and stored. The dynamic range, resolution, noise and linearity of the system as evaluated from the laboratory and 2016 beam commissioning data will be discussed in detail.

The Giga Bit Transceiver based Expandable Front-End (GEFE)—a new radiation tolerant acquisition system for beam instrumentation

The Giga Bit Transceiver based Expandable Front-End (GEFE) is a multi-purpose FPGA-based radiation tolerant card. It is foreseen to be the new standard FMC carrier for digital front-end applications in the CERN BE-BI group. Its intended use ranges from fast data acquisition systems to slow control installed close to the beamlines, in a radioactive environment exposed to total ionizing doses of up to 750 Gy. This paper introduces the architecture of the GEFE, its features as well as examples of its application in different setups.