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Frequency Analysis of BPM Signals in Particle Accelerator

This study analyzes signal frequencies in Beam Position Monitor data from a particle accelerator, highlighting variations and dominant components for different BPMs as well as the impact of parameter adjustments. Shot-to-shot variations and signal suppression/enhancement effects are examined.

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Frequency Analysis of BPM Signals in Particle Accelerator

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  1. 3243 Fri 23 Nov Summary • INJ-BPM-01: took 1 shot of data, just a reference to compare with previous recent shifts • Did not see a strong dominant 100 kHz signal, but it might be present in 0-200 kHz frequency content • INJ-BPM-02: vs steering, solenoid, buncher • 300 kHz signal in x,y, charge is the dominant, particularly in x • But also ~ 100 kHz signal (as well as other low freq components) • The frequency content between 0-200 kHz in x and y shows some shot to shot variation in this. • When offset large in y (6 mm), y trace looks similar to charge trace, and 300 kHz is enhanced in y. • No 6 MHz, as is the case since commissioning break • Droop towards end of train in charge signal (as in 3205, is this seen in FCUP/PI laser ?) • INJ-BPM-03: • Can see 100 kHz in x which is small but in dominates other frequencies. Shot-to-shot variation. • Can suppress 100 kHz and enhance 300 kHz by steering. • INJ-BPM-04: • Low frequency content 0 -200 kHz. 100 kHz probably there but not dominant. • AR2-BPM-01: First time this BPM had been used • Large slope on x. . 100 kHz there but not dominant • AR1-BPM-01 • The usual dominant ~ 100 kHz in x

  2. NOTE: • I am normalising the x,y DFT so that the amplitude is measured in mm, following the recipe in …. • \\Dlfiles03\alice\Analysis\Period 14 data\AP_period13and14\BPM\fouriernormalisation.pptx

  3. INJ-BPM-01 Observe the same features as in #3205, -droop in x -low frequency (< 200 kHz) content in x/y but no single defined frequency dominating -300 kHz strong signal in BPM charge leaking to x and y For Fourier analysis, take portion of bunch 6 – 60 μsec to remove early transient + droop

  4. INJ-BPM-02 Nominal Set-Up Initial shot Return to original settings 50 mins later after much steering, param scans etc Relatively strong 300 kHz in x. Low frequency (< 200 kHz) content in x/y but, as BPM-01, no single defined frequency dominating. The amplitudes are higher (5-10 times) compared to INJ-BPM-01

  5. INJ-BPM-02 Shot to Shot Variation After steering to get more central x position on INJ-BPM-02 The low frequency (< 200 kHz) content does vary a bit shot-to-shot

  6. INJ-BPM-02 Shot to Shot Variation After steering to get more central y position on INJ-BPM-02 Again, the low frequency (< 200 kHz) content does vary a bit shot-to-shot

  7. Parameter Variation vs INJ-BPM-02 observations • Varied SOL-02 and Buncher Power independently. • Neither parameter had a dramatic effect on INJ-BPM-02 observations. Frequencies and amplitudes changed slightly from nominal set-up • Then changed SOL-01, with steering adjustment to keep centred on INJ-BPM-01. Again nothing dramatic … • But one observation ….

  8. Large Offset in Y INJ-BPM-02 y large offset and looks similar to charge trace. here have changed SOL-01 and H/VCOR-01 compared to nominal settings Can see the 300 kHz is enhanced in y

  9. And if large offset in X ??INJ-BPM-02 • Looked through other data to see if the same thing happened with large x offset • This conditioned occurred when varying SOL-02 • 300 kHz is enchanced in x, but raw trace not very similar to charge

  10. INJ-BPM-03 • Evidence of fairly strong ~ 100 kHz was seen previously (#3191) There is a “cleaner” low frequency feature in x ~ 100 kHz But the Fourier reveals the amplitude of this feature is SMALLER than on INJ-BPM-02. However the 300 kHz is very much suppressed and this makes the 100 kHz more noticable. Amplitudes in x,y, charge all suppressed compared to INJ-BPM-02

  11. INJ-BPM-03 shot-to-shot Again, the low frequency (< 200 kHz) content does vary a bit shot-to-shot

  12. INJ-BPM-03 steer horizontally thru booster • Steering directly upstream of BOOSTER i.e. steering through buncher not affected. x offset large and negative, 100 kHz suppressed, 300 kHz enhanced compared to nominal steering

  13. INJ-BPM-03 steer horizontally thru booster • Can change relative size of ~ 100 KHz or 300 kHz in x and y by steering vertically

  14. INJ-BPM-04 NOTE MAGNIFIED SCALE Again, the low frequency (< 200 kHz) content does vary a bit shot-to-shot

  15. AR2-BPM-01 • Not been used before Large slope in both x and y, somewhat unexpected since this is nominally zero dispersion ~100 kHz, 300 kHz freq components as usual

  16. AR1-BPM-01 100 KHz enhanced significantly, in agreement with previous data

  17. Conclusions on 100 kHz • There is some frequency content at ~ 100 kHz in x and y (but mainly x) everywhere in the machine. It has different amplitude on different BPMs, and its amplitude relative to 300 kHz is also different on different BPMs • 100 kHz is enhanced (and other frequencies supressed) in AR1, so that it is very obvious there. But it is seen in the injector, and before the booster. • Relatively large 100 kHz amplitude on INJ-BPM-02 but there is also a large 300 kHz component here which disguises it. • On INJ-BPM-01 it might be present but obscured by several frequency components 0-200 kHz. • On AR1-BPM-01, 100 kHz in x is dominant and large • On AR2-BPM-01, 100 kHz in x is much smaller than on AR1-BPM-01

  18. Other Conclusions • Injector steering enhances different frequencies (100, 300 kHz) on the injector BPMs in different ways. Needs understanding. • Droop towards end of train in x, y, charge evident in injector

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