• M. Koujili, J. De Freitas, B. Dehning, J. Koopman, D. Ramos, M. Sapinski
  CERN, Geneva
• Y. Ait Amira
  UFC, Besançon
• A. Djerdir
  UTBM, Belfort

Scanning of a high intensity particle beam imposes challenging requirements on Wire Scanner system. It is expected to reach scanning speed of 20 m/s with position accuracy of the order of 1 μm. In addition a timing accuracy better than 1 millisecond is needed. The adopted solution consists of a wire holding fork rotating by maximal of 200°. Fork, rotor and angular position sensor are mounted on the same axis and located in a chamber connected to the beam vacuum. The requirements imply the design of a system with extremely low vibration, vacuum compatibility, radiation, and temperature tolerance. The adopted solution consists of a rotary brushless synchronous motor with the permanent magnet rotor installed inside of the vacuum chamber and the stator installed outside. The accurate position sensor will be mounted on the rotary shaft inside of vacuum chamber and has to resist bake-out temperature of 200°C and ionizing radiation up to tenth of kGy/years. A digital feedback controller allows maximum flexibility for the loop parameters and feeds the 3 phases input for the linear power driver. The paper will present a detail discussion of chosen concept and the selected components.

• S. Jackson, B. Dehning, J. Emery, J. Fitzek, F. Follin, V. Kain, G. Kruk, M. Misiowiec, C. Roderick, M. Sapinski, C. Zamantzas
  CERN, Geneva

The LHC Beam Loss Monitoring (BLM) system is one of the most complex instrumentation systems deployed in the LHC. As well as protecting the machine, the system is also used as a means of diagnosing machine faults, and providing feedback of losses to the control room and several systems such as the Collimation, the Beam Dump and the Post-Mortem. The system has to transmit and process signals from over 4'000 monitors, and has approaching 3 million configurable parameters. This paper describes the types of configuration data needed, the means used to store and deploy all the parameters in such a distributed system and how operators are able to alter the operating parameters of the system, particularly with regard to the loss threshold values. The various security mechanisms put in place, both at the hardware and software level, to avoid accidental or malicious modification of these BLM parameters are also shown for each case.

• G.G. Venturini, B. Dehning, E. Effinger, C. Zamantzas
  CERN, Geneva

A novel radiation hardened current digitizer ASIC is in planning stage, aimed at the acquisition of the current signal from the ionization chambers employed in the Beam Loss Monitoring system in CERN accelerator chain. The purpose is to match and exceed the performances of the existing discrete component design, currently in operation in the Large Hadron Collider (LHC). The specifications include: a dynamic range of nine decades, defaulting to the 1pA-1mA range but adjustable by the user, ability to withstand a total integrated dose of at least 10 kGray in 20 years of operation and user selectable integrating windows, as low as 500ns. Moreover, the integrated circuit can be employed to digitize currents of both polarity with a minimum number of external components and without needing any configuration. The target technology is IBM 130 nm CMOS process. The specifications, the architecture choices and the reasons on which they're based upon are discussed in the paper.

• G.G. Venturini, B. Dehning, E. Effinger, J. Emery, C. Zamantzas
  CERN, Geneva

A discrete components design of a current digitizer based on the current-to-frequency converter (CFC) principle is currently under development at CERN. The design targets at rather high input current compared to similar designs, with a maximum equal to 200mA and a minimum of 1nA, as required by the ionization chamber that will be employed in the Proton Synchrotron and Booster accelerators as well as in the LINAC. It allows the acquisition of currents of both polarities without requiring any configuration and provides fractional counts through an ADC to increase the resolution. Several architectural choices are being considered for the front-end circuit, including charge balance integrators, dual-integrator input stages, integrators with switchable-capacitor, in both synchronous and asynchronous versions. The signal is processed by an FPGA and transmitted over a VME64x bus. Design, simulations and measurements are discussed in this article.

• J. Emery, B. Dehning, E. Effinger, G. Ferioli, C. Zamantzas
  CERN, Geneva
• H. Ikeda
  KEK, Ibaraki
• E. Verhagen
  UW-Madison/PD, Madison, Wisconsin

For the LHC beam loss measurement system the high voltage supply of the ionisation chambers and the secondary emission detectors is used to test their connectivity. A harmonic modulation of 0.03 Hz results in a current signal of about 100 pA measured by the beam loss acquisition electronics. The signal is analyzed and the measured amplitude and phase are compared with individual channel limits for the 4000 channels. It is foreseen to execute an automatic procedure for all channels every 12 hours which takes about 20 minutes. The paper will present the design of the system, the circuit simulations, measurements of systematic dependencies of different channels and the reproducibility of the amplitude and phase measurements.

• M. Sapinski, B. Dehning, A. Guerrero, J. Koopman, E. Métral
  CERN, Geneva

Carbon fibres are commonly used as moving targets in Beam Wire Scanners. Because of their thermo mechanical properties they are very resistant to particle beams. Their strength deteriorates with time due to low-cycle thermal fatigue. In case of high intensity beams this process can accelerate and in extreme cases the fibre is damaged during a scan. In this work a model describing the fibre temperature, thermionic emission and sublimation is discussed. Results are compared with fibre damage test performed on the CERN SPS beam in November 2008. For the operation of Wire Scanners with high intensity beams damage threshold are predicted.