A 0 Ti Sapph Expts A 0 Photoinjector

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A 0 Ti: Sapph Exp’ts A 0 Photoinjector December 9 th, 2010 Tim Maxwell

A 0 Ti: Sapph Exp’ts A 0 Photoinjector December 9 th, 2010 Tim Maxwell November 18 th, 2010

TOD compensation • Determining Ti: Sph phase correction: – Run Dazzler in self-compensating mode

TOD compensation • Determining Ti: Sph phase correction: – Run Dazzler in self-compensating mode – Minimize basic autocorrelation via Spit. Fire compressor – Collect series of FROG traces with these settings • Use mean of curves as phase correction November 18 th, 2010

TOD before Mean from 10 traces Mean±σ from 10 traces November 18 th, 2010

TOD before Mean from 10 traces Mean±σ from 10 traces November 18 th, 2010

After feeding back measured phase Mean from 10 traces Mean±σ from 10 traces Still

After feeding back measured phase Mean from 10 traces Mean±σ from 10 traces Still some small chirp? November 18 th, 2010

“Porcupine Trick” • Made ansatz about a special phase modulation… Spectrum ω Note that

“Porcupine Trick” • Made ansatz about a special phase modulation… Spectrum ω Note that phase is integral of group delay: a piece-wise pair of offset parabolas ϕ’ (group delay) • Chirp + advance first half of pulse by half the bandwidth (retard second half) • Distinct result: – Elongated pulse (from chirp) – Temporally modulated at 1/bandwidth (back of spectrum “beating” against front) November 18 th, 2010

Porcupine’s FROG trace November 18 th, 2010

Porcupine’s FROG trace November 18 th, 2010

Porcupine phase recovered November 18 th, 2010

Porcupine phase recovered November 18 th, 2010

FROG • Femtosoft FROG 3. 2. 2 received – Compensation curve measured – Reproducability

FROG • Femtosoft FROG 3. 2. 2 received – Compensation curve measured – Reproducability studied • RMS experimental group delay error about 30 fs with strong signal • Degrades as spectrum approaches 2% of max (as configured) • Repeatability better than resolution of measurement – Trick “porcupine” laser pulse generated with Dazzler and diagnosed with FROG • Conclusion: Current Spit. Fire phase control/diagnostics look consistent. November 18 th, 2010