FEMTOSECOND TIMING! By Michael Rocco Whalen and Cara Perkins

P UMP – P ROBE E XPERIMENTS  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.

S IGNAL M IXING 2 =

T ESTING F REQUENCY M IXERS FOR P OWER S ENSITIVITY

C ALCULATING S ENSITIVITY

S ENSITIVITY P ERFORMANCE OF THE M IXERS Mini-Circuits ® Model ZX05-HW-S+ Mini-Circuits ® Model ZFM-4H-S+ Mini-Circuits ® Model ZFM-150 Mixer NumberSensitivity (V/ps) Average Sensitivity of the Mixers

C AN YOU HEAR ME NOW ? White Noise Spectrum Pink Noise Spectrum

T ESTING THE RF C OMPONENTS FOR T HEIR N OISE - TO -S ENSITIVITY R ATIO Mini-Circuits Splitter Model ZFSC-2-1W+ Anaren Splitter Model 40263

R ESOLUTION B ANDWIDTH (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 Bandwidth10 kHz Resolution Bandwidth

T HE S EARCH FOR P INK N OISE 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.

N OISE - TO -S ENSITIVITY R ATIOS CombinationNoise-to-Sensitivity Ratio (fs/√(Hz)) LCLS Timescale at 200 kHz RBW (fs) #1 Mixer, #1 Splitter 6.95E #1 Mixer, #2 Splitter 7.56E #2 Mixer, #1 Splitter 9.00E #2 Mixer, #2 Splitter 7.47E #3 Mixer, #1 Splitter 1.62E #3 Mixer, #2 Splitter 1.70E Average Noise of Mixer and Splitter Combinations

T ESTING THE C OMPONENTS FOR T EMPERATURE -D EPENDENT P HASE D RIFT

T EMPERATURE AND P HASE D RIFT R ESULTS Component Phase Drift (fs/ ⁰ C) Mini-Circuits Splitter Model ZFSC-2-1W Anaren Splitter Model Mini-Circuits Mixer Model ZX05-HW-S Mini-Circuits Mixer Model ZFM-4H-S Mini-Circuits Mixer Model ZFM Aeroflex Phase Shifter Model ' Belden Coaxial 50 Ohm Microwave Cable Model 1673A

T HANK YOU, APE (Accelerator Physics & Engineering) LAB, for all your assistance in femtosecond measuring!!