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Results of Microphone Tests in HiRadMat Collimation WG Meeting

This document presents the results of microphone tests conducted in the HiRadMat Collimation WG Meeting on 15.10.2012. The tests aimed to analyze sound signals, localize impacts, and investigate the limitations of the system for impact detection and localization at LHC collimators.

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Results of Microphone Tests in HiRadMat Collimation WG Meeting

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  1. Results of microphone tests in HiRadMatCollimation WG Meeting15.10.2012Daniel Deboyon behalf of the Collimation team, thanks to A. Masi, J. Lendaro, C. Derrez and teamI. Efthymiopoulos and HRM team Collimation WG Meeting 15.10.2012

  2. MICROPHONES AT HRM Purpose of Sound Analysis • Can we (roughly) localize Impacts with correlation measures between two or more microphone signals? • Sound Pressure Level -> Amplitude of pressure wave • Spectral Components -> Damage/ no damage? • Investigate limitations of the system (EM noise, R2E) Application: Impact detection and localization at LHC collimators! Collimation WG Meeting 15.10.2012

  3. Microphone Positions Upstream Downstream ca 13.5 m ca 13.5 m ca 6.5 m ca 25 m Collimation WG Meeting 15.10.2012

  4. Localization with TDOA Beam impact position Reference location Beam ∆T3 ∆T1 ∆T2 Mic 3 Mic 1 Mic 2 Speed of sound cs= 343 m/s (@20° C) Reference location sref = ∆T2 * cs = - ∆T1 * cs Estimated location simp = sref + (∆T2-∆T1) * cs Collimation WG Meeting 15.10.2012

  5. Microphone Signals Typical radiation induced noise spikes during impact Peak amplitude linear dependent on beam intensity -> saturation limit at signal amplitude equal to a sound pressure level of approximately 163 dB SPL (ca 2700Pa = 3V with 10mV/Pa output sensitivity) Collimation WG Meeting 15.10.2012

  6. Noise from Radiation vs. Intensity Upper limit of Mic sensor (eq. 163dB SPL) Mic Downstream Measurements taken during HRMT 12 experiment Extrapolated and scaled assuming 1/r2 mitigation -> Estimate of distances needed to avoid signal overload Collimation WG Meeting 15.10.2012

  7. Test 1 Mic Signals High Intensity Shot – Spike from Radiation Blue: 13.5m Downstream Green: 13.5m Upstream Red: 24 m Upstream Test 1: 1 Nominal LHC Bunch @7TeV Equ. 3.2E12 p @440GeV at HiRadMat Shot on Collimator Jaw Sound Pressure (Pa) ca 114 ms Sensor Saturation Time (s) Collimation WG Meeting 15.10.2012

  8. Test 1 Sound Sound after High-Pass Filtering (Butter 3rd, 100Hz) Amp Output Sensitivity: 3.16mV/Pa RMS Noise ca 70 dB Downstream Delay ca 114 ms (sound lost due to sensor saturation) Upstream Peak Value ca 100 dB Delay ca 44 ms = 15 m Sound Pressure (Pa) Amp Output Sensitivity: 31.6mV/Pa RMS Noise ca 60 dB PatchRack Peak Value ca 90 dB Delay ca 84 ms = 28 m Time (s) Collimation WG Meeting 15.10.2012

  9. Test 1 Peak Estimate Artifacts from Radiation Spike are cut for estimation of peak value. Peak value of cut signal: Ca 93 dB SPL Energy normalized to peak value! RMS Noisefloor: Reached after 0.7s Estimated Energy at expected onset (42ms): +4.6 dB Estimated Peak SPL: 97.6 dB Collimation WG Meeting 15.10.2012

  10. Sound Pressure vs. Intensity Test 3: Severe Damage expected Test 1: Damage expected Test 2: No Damage Collimation WG Meeting 15.10.2012

  11. Algorithm: Localization and Damage Mic 1 Peak Detection HighPass Filter Calculate Delay Time Calculate Magnitude Reference Data Estimate Damage Level Estimate Location (TDOA) Estimate Impact Strength Mic 2 Peak Detection HighPass Filter Calculate Delay Time Calculate Magnitude Collimation WG Meeting 15.10.2012

  12. Remarks • Localization of impacts and damage estimation is possible using only two microphones for a set of collimators! • Radiation induced noise spike can be used as “trigger” signal, however… • …Signal to Noise Ratio is bad due to radiation spike (long distances, low gain) • Improvement: Analogue HP Filter (allows higher gain factor) • Prototype Test of optical microphone solution (-> Balthasar Fischer - TU Vienna) • Next steps: • Analyze Sound Pressure vs. Distance • Find robust methods to determine Time difference of arrival (TDOA) • Derive estimate for energy of pressure wave at outer shell of collimator • Visual Inspection of HRM09 damage for reference classification (2013) Collimation WG Meeting 15.10.2012

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