MICROPHONES AT HRM

Results of microphone tests in HiRadMat

Collimation WG Meeting15.10.2012

Daniel Deboyon behalf of the Collimation team,

thanks to A. Masi, J. Lendaro, C. Derrez and teamI. Efthymiopoulos and HRM team

1Collimation WG Meeting 15.10.2012

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!

2Collimation WG Meeting 15.10.2012

Microphone Positions

3

ca 6.5 m

ca 13.5 mca 13.5 m

ca 25 m

DownstreamUpstream

Collimation WG Meeting 15.10.2012

4

Localization with TDOA

∆T3

Mic 3 Mic 2 Mic 1

∆T2 ∆T1

Beam impact position

Beam

Speed of sound cs= 343 m/s (@20° C)Reference location sref = ∆T2 * cs = - ∆T1 * cs

Estimated location simp = sref + (∆T2-∆T1) * cs

Reference location

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

Mic Downstream Measurements taken during HRMT 12 experimentExtrapolated and scaled assuming 1/r2 mitigation-> Estimate of distances needed to avoid signal overload

Upper limit of Mic sensor (eq. 163dB SPL)

Collimation WG Meeting 15.10.2012

Test 1 Mic Signals

7

ca 114 ms Sensor Saturation

Blue: 13.5m DownstreamGreen: 13.5m UpstreamRed: 24 m Upstream

Sou

nd P

ress

ure

(Pa)

High Intensity Shot – Spike from Radiation

Time (s)

Test 1:1 Nominal LHC Bunch @7TeV

Equ. 3.2E12 p @440GeV at HiRadMat

Shot on Collimator Jaw

Collimation WG Meeting 15.10.2012

Test 1 Sound

8

RMS Noise ca 70 dB

RMS Noise ca 60 dB

Delay ca 44 ms = 15 m

Delay ca 84 ms = 28 m

Peak Value ca 100 dB

Peak Value ca 90 dB

Delay ca 114 ms (sound lost due to sensor saturation)

Sou

nd P

ress

ure

(Pa)

Sound after High-Pass Filtering (Butter 3rd, 100Hz)

Downstream

Upstream

PatchRack

Time (s)

Amp Output Sensitivity: 3.16mV/Pa

Amp Output Sensitivity: 31.6mV/Pa

Collimation WG Meeting 15.10.2012

Test 1 Peak Estimate

9

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

Collimation WG Meeting 15.10.2012

Test 2:No Damage

Test 1:Damage expected

Test 3:Severe Damageexpected

11

Algorithm: Localization and Damage

HighPassFilter

Peak Detection

CalculateDelay Time

CalculateMagnitude

HighPassFilter

Peak Detection

CalculateDelay Time

CalculateMagnitude

Estimate Location(TDOA)

EstimateImpact Strength

EstimateDamage Level

Mic 1

Mic 2

Reference Data

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