PI laser jitter measurements

Data taken on 11th April 2013

• 11th April 2013• Quadrant photodiode mounted on virtual

cathode table• Photodiode has ‘bandwidth’ of 150 kHz • Measured 100 μs trains @ 10 Hz, 16 MHz

within train ? pulse power (LA = 0.65)?• Measured x-y, and sum for several single

shots, on hi-res scope (1 Gsample/sec)

Sample single shot x,y, chargeRaw scope dataUnits on vertical axis are arbitraryHorizontal units are nanoseconds

20 000 40000 60 000 80 000 100 000

0.2

0.4

0.6

0.8

1.0

1.2

zoomed trace0.1 ns sample spacingindividual pulses not discernible

Data (5 shots)x

x

charge

chargey

DFTx

x

charge

chargey

REMINDER OF BPM VARIATIONS SEEN IN 2012

Nominal Lattice• FEL-like set-up. • Nominal ar1q1/4 = 2.2 A

3133 AR1

3205 INJ-BPM-01 INJ-BPM-01 fast bunch electronics RAW DATA

Note significant droop in all 3 observables

Small transient at start of train

x y charge15 pC

21 pC

30 pC

43 pC

60 pC

BPM frequency content, 0 – 1 MHz

Strong 300 kHz

100 kHz not obviously apparent

Norrmalised the x,y DFT so that the amplitudes are in mm

3205 INJ-BPM-01

INJ-BPM-03• Nominal FEL set-up. ‘Typical’ 1-shot BPM train measurement

100 KHz obvious in xy very similar to sum_pickup voltage6 Mhz present, smaller than 100 KHz‘usual’ 300 KHz present

x (mm), y (mm), sum voltageFourier transform vertical axis amplitude^2horizontal axis frequency in MHzFourier transforms done after subtracting mean values

3191 INJ-BPM-03

INJ-BPM-02 Shot to Shot Variation

Again, the low frequency (< 200 kHz) content does vary a bit shot-to-shot

After steering to get more

central y position on INJ-BPM-02

3243