1. Beam Loss Analysis Tool for the CTF3 PETS Tank M. Velasco, T. Lefevre, R. Scheidegger, M. Wood, J. Hebden, G. Simpson Northwestern University, Evanston, Il - ICAR Beam Loss Analysis Tool for the CTF3 PETS Tank M. Velasco, T. Lefevre, R. Scheidegger, M. Wood, J. Hebden, G. Simpson Northwestern University, Evanston, Il - ICAR In the CLIC project, the 30 GHz RF power source is produced in the so called ‘Drive Beam decelerator’ where resonant structures called ‘Power Extraction and Transfer Structures (PETS)’ decelerate a high current electron beam and convert the particles’ energy into RF power. The strong coupling in the PETS could lead to important beam losses if the beam optics are set incorrectly. It is thus crucial to monitor beam losses accurately in order to check the Drive Beam decelerator stability, to protect the accelerator itself from any beam induced damages and to keep the radiation level and activation as low as possible. The goal of this study is to develop a tool to quantify the beam losses along a PETS tank installed in the CLIC Test Facility 3 (CTF3) machine at CERN. Any future machine protection system will rely on measuring accurately the position and intensity of beam losses. Beam Loss Simulations Simulations of e + /e - showers distribution inside the PETS were generated with Geant3.21. The losses were simulated for 10M electrons with an energy of 50MeV hitting the top of the structure every 5cm with an angle of 3mrad. Simulations were also generated for 20cm of beam pipe before and after the PETS tank. Beam loss in the beam pipe induces secondary particle fluxes an order of magnitude higher than in the PETS A 1.5m long PETS Tank is already installed in the CTF3 tunnel 5 detectors are distributed along the PETS Tank to monitor the beam losses The detectors are Aluminum Cathode Electron Multipliers. They have a fast time response (2ns) which allows to observe the time evolution of the beam losses All the BLM’s are fed in parallel from the same power supply The output signals are then sent to fast Analog to Digital converters Experimental Setup e-e- Tunnel Gallery 8 channels digitizer VME module 12 bits acquisition @ 96 MHz 0-2kV, 100mA Power supply Electronic Rack Looking inside a PETS Tank Vacuum tank diameter is 30cm Resonant Cell Iris diameter is 6.7mm Resonant cavities 30GHz Output Waveguide Vacuum Tank For beam loss at a given zed position, the flux measured strongly depends on the transverse position of the detector (Phi angle). For beam loss at a given phi position, the measured flux only depends on the distance from the detector to the beam loss position : It is maximum for losses that occur 40cm before the detector. mn Amplifier box High voltage from the gallery SIC Signals Signals to the ADC’s High voltages to the SIC Future Beam Loss Monitoring Setup SIC detectors specifically designed for beam loss measurements will be used to monitor the showers along the PETS. The SIC detectors are sensitive to charged particles and offer a very good resistance to radiation and a high dynamic range (>10 5 ). The SIC output signals will be amplified in the tunnel using a 300MHZ, 26/46dB amplifier card Installing more detectors at each zed position to cover the azimuthal angle. Connect them together and use a single electronic per zed position 6 detector zed positions: every 40cm starting at the beginning of the tank An improved detector configuration that takes into account the transverse distribution of the showers is foreseen to measure beam losses accurately. 300MHz 26 to 46dB amplification Multiple tests and processing steps are required to ensure that each detector is measuring the best signal possible and that clear signals are used in the analysis step. Beam Loss Analysis Tool Display Only one loss position per beam time slice Beam energy is constant throughout the PETS Assumptions Qualitative and Quantitative Beam Loss Analysis First, the qualitative analysis phase finds overall patterns of the signals to qualify the beam loss. The following beam loss cases are investigated: Continuous loss all along the tank Constant intensity loss for multiple beam timings Region of loss for the beginning, middle and end of the beam Then the quantitative phase compares the signals’ time slices to the simulations to find the beam loss zed position and intensity. Beam Loss Analysis Tool The beam loss analysis tool was developed with Matlab 6.5. It is divided into four main parts: a signal quality testing phase, a signal processing phase, a qualitative analysis phase and a quantitative analysis phase that relies on the simulations’ results to find the position and intensity of beam loss along the PETS tank. Flux as a Function of Distance to Beam Loss Position for Detectors at phi = 90 Flux for Detectors at zed = 82 cm Beam Loss Signals Before and After Signal Processing Check for detector saturation Check for detector long decay time Check signal amplitude and suggest best amplification Correct zero offset Synchronize signals Smooth noise Select timing region where beam is present Reset amplitude according to detector calibration and amplification Signal Quality and Signal Processing Future Software Improvements Assume beam is decelerating Error Calculation Multiple PETS in a row