RF Cavity Breakdown Localization: Sensor and Signal Studies on Al - - PowerPoint PPT Presentation

▶
rf cavity breakdown localization
SMART_READER_LITE
LIVE PREVIEW

RF Cavity Breakdown Localization: Sensor and Signal Studies on Al - - PowerPoint PPT Presentation

Oct 19, 2022 373 likes •541 views

RF Cavity Breakdown Localization: Sensor and Signal Studies on Al Disk Peter Lane Pavel Snopok 1 Overall Setup Aluminum disk from mock cavity as medium Ultrasonic ping generator Sensors and speaker around disk circumference

slide-1
SLIDE 1

1

RF Cavity Breakdown Localization:

Sensor and Signal Studies on Al Disk

Peter Lane Pavel Snopok

slide-2
SLIDE 2

2

Overall Setup

  • Aluminum disk from mock cavity as medium
  • Ultrasonic “ping” generator
  • Sensors and speaker around disk

circumference

slide-3
SLIDE 3

3

Ultrasonic Ping Generator

  • 555 for pulse width and pulse frequency
  • 555 for signal frequency
  • LM386 audio amplifier driving the transducer
  • Scavenged piezoelectric transducer
  • Separate 9V wall adapter powering the circuit

– signal pollution and battery voltage issues

slide-4
SLIDE 4

4

Sensor Calibration

  • Check that sensor polarities are the same
  • Check that sensor response is similar
  • Input Signal

– One pulse every 3.6 s – Pulse width of 0.48 ms – Signal frequency of 79 kHz

  • Positioned speaker and sensor next to each
  • ther on side of Al disk
slide-5
SLIDE 5

5

Sensor Calibration Setup

slide-6
SLIDE 6

6

Sensor Polarity

slide-7
SLIDE 7

7

Sensor Response

slide-8
SLIDE 8

8

Sensor Calibration Conclusions

  • Polarities are all the same.

– Any polarity flips would have to come from

reflections at metal/air boundary.

  • Amplitudes can vary among sensors by ~2V.

– Makes relative peak finding more difficult. – Hypothesis: Any signal which is observed

having a uniform amplitude on all channels is EMI.

slide-9
SLIDE 9

9

3-Channel Signal Analysis

  • Use a consistent acoustic signal to better

understand what is happening inside the cavity walls.

  • Input Signal

– One pulse every 270 ms – Pulse width of 32 µs – Signal frequency of 120 kHz

  • Senors placed at 90 degree intervals around

the circumference

slide-10
SLIDE 10

10

3-Channel Signal Setup

slide-11
SLIDE 11

11

3-Channel Signal Overview

slide-12
SLIDE 12

12

2D Modeling of the Disk

  • Model a pressure wave with the same

symmetric arrangement of sensors as before

slide-13
SLIDE 13

13

Asymmetric Source Signal Simulation

slide-14
SLIDE 14

14

3-Channel Signal Conclusions

  • Signal envelope mean lifetime about 9 ms.
  • Sensors close to the source are clean.
  • Sensor further from the source is dirty due to

reflection interference.

  • Envelope oscillations due to reflections
  • Time domain wave front detection is rather

difficult even with nice input signals

slide-15
SLIDE 15

15

Alternative Ideas for Wave Front Detection

  • Integrate sensor data backwards in time to

reconstruct the source position

– Too computationally intensive for an online tool

  • Use signal database or neural network

– Requires the luxury of training on known

  • utcomes
  • Sensor symmetry correlations

– Try to match signals from symmetrically placed

sensors

slide-16
SLIDE 16

16

Alternative Ideas for Wave Front Detection

  • Rolling FFT idea from Keith Pedersen

– Density plots show visible bands at points in

time related to the beginning of the pulse

– Need to see if this has sufficient resolution and

can be turned into an detection algorithm

– Will experiment with this if there are no other

suggestions

  • Need DAQ card to experiment in realtime