FEMTOSECOND

TIMING!ByMichael Rocco WhalenandCara Perkins

PUMP – PROBE EXPERIMENTS A pump-probe experiment excites an atom

or molecule with a visible laser beam, then probes the object with a hard X-ray. By measuring the timing difference between the two laser pulses, one can rearrange the captured images and create a “movie” of the chemical dynamics.

SIGNAL MIXING

2

=

TESTING FREQUENCY MIXERS FOR POWER SENSITIVITY

CALCULATING SENSITIVITY

SENSITIVITY PERFORMANCE OF THE MIXERS

Mini-Circuits ® Model ZX05-HW-S+

Mini-Circuits ® Model ZFM-4H-S+

Mini-Circuits ® Model ZFM-150

Mixer

Number

Sensitivity

(V/ps)

1 0.023 00

2 0.018 60

3 0.005 96

Average Sensitivity of the Mixers

CAN YOU HEAR ME NOW?

White Noise Spectrum

Pink Noise Spectrum

TESTING THE RF COMPONENTS FOR THEIR NOISE-TO-SENSITIVITY RATIO

Mini-Circuits Splitter Model ZFSC-2-1W+

Anaren Splitter Model 40263

RESOLUTION BANDWIDTH (RBW)

Smaller RBW’s have better resolution. Therefore, harmonics are more apparent. Here, one can see the 60 Hz harmonics coming from nearby power lines.

Larger RBW’s look at a much wider frequency band. The averaging of the frequency measurements eliminates most of the harmonics seen at lower RBW’s.

10 Hz Resolution Bandwidth 10 kHz Resolution Bandwidth

THE SEARCH FOR PINK NOISE

The spectrum analyzer revealed a noise floor that resembled a 1/f curve, but further investigation showed that this was simply the result of averaging the incoming frequencies.

This noise floor was taken at a 100 Hz RBW.

NOISE-TO-SENSITIVITY RATIOS

0 2 4 6 8 10 12 14 16 180.00E+00

5.00E-07

1.00E-06

1.50E-06

2.00E-06

2.50E-06

3.00E-06

Mixer 1, Splitter 1, 100 Hz RBW

5 dBm LO10 dBm LO17 dBm LO20 dBm LO

RF Input

ps/ √

(Hz)

Combination

Noise-to-Sensitivity

Ratio (fs/√(Hz))

LCLS Timescale at 200 kHz RBW

(fs) #1 Mixer, #1 Splitter

6.95E-04 0.311

#1 Mixer, #2 Splitter

7.56E-04 0.338

#2 Mixer, #1 Splitter

9.00E-04 0.402

#2 Mixer, #2 Splitter

7.47E-04 0.334

#3 Mixer, #1 Splitter

1.62E-03 0.724

#3 Mixer, #2 Splitter

1.70E-03 0.760

Average Noise of Mixer and Splitter Combinations

TESTING THE COMPONENTS FOR TEMPERATURE-DEPENDENT PHASE DRIFT

TEMPERATURE AND PHASE DRIFT RESULTS

ComponentPhase Drift

(fs/⁰C)Mini-Circuits Splitter Model ZFSC-2-1W+ 3.780594406Anaren Splitter Model 40263 8.503419973Mini-Circuits Mixer Model ZX05-HW-S+ 26.79407713Mini-Circuits Mixer Model ZFM-4H-S+ 1.694897959Mini-Circuits Mixer Model ZFM-150 6.952019732Aeroflex Phase Shifter Model 980 24.5629370610' Belden Coaxial 50 Ohm Microwave Cable Model 1673A 81.58277672

THANK YOU,

APE (Accelerator

Physics & Engineering)

LAB, for all your assistance in femtosecond measuring!!