Experimental Studies on FEL Gain Controlled by Laser-induced - - PowerPoint PPT Presentation
Introduction Lasing Suppression July 2014 Studies . Experimental Studies on FEL Gain Controlled by Laser-induced Longitudinal Space Charge Amplification Christoph Lechner University of Hamburg 6th Microbunching Instability Workshop Trieste;
Introduction Lasing Suppression July 2014 Studies .
Christoph Lechner University of Hamburg 6th Microbunching Instability Workshop Trieste; October 7, 2014
Supported by BMBF under contract No.s 05K13GU4 and 05K13PE3 and by DFG GRK 1355
1 Christoph Lechner, University of Hamburg
Introduction Lasing Suppression July 2014 Studies .
315 m 5 MeV 150 MeV 1250 MeV Bunch Compressors 450 MeV Accelerating Structures RF Stations Lasers RF Gun Soft X-ray Undulators sFLASH FEL Experiments Photon Diagnostics Beam Dump THz FLASH1
2 Christoph Lechner, University of Hamburg
Introduction Lasing Suppression July 2014 Studies .
3 Christoph Lechner, University of Hamburg
Introduction Lasing Suppression July 2014 Studies .
ORS technique: Use Modulator-radiator arrangement to find precise temporal overlap. Coherent undulator radiation emitted in radiator signals laser-electron
4 Christoph Lechner, University of Hamburg
Introduction Lasing Suppression July 2014 Studies .
Observation of coherent undulator radiation to find precise temporal
ORS1overlap1causes drop1of1observed FLASH1SASE1energy
scan1time1[ps]
1h0 51h0
first1scan
70 80 90 100 110 120 FEL1pulse1energy1[µJ] 01:03:21 01:06:14 01:09:07 01:12:00 01:14:52 01:17:45
time1[hh:mm:ss]
5 Christoph Lechner, University of Hamburg
Introduction Lasing Suppression July 2014 Studies .
Laser manipulation of electron bunches offers many possibilities: Tailor electron bunches without touching machine
experiments
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− −
6 Christoph Lechner, University of Hamburg
Introduction Lasing Suppression July 2014 Studies .
Laser manipulation of electron bunches offers many possibilities: Tailor electron bunches without touching machine
experiments
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− −
6 Christoph Lechner, University of Hamburg
Introduction Lasing Suppression July 2014 Studies .
Laser manipulation of electron bunches offers many possibilities: Tailor electron bunches without touching machine
experiments Study longitudinal profile of the electron bunches
...
longitudinal5coordinate5(fs) energy5deviation5(10−3) −500 500 −5 5 10 Longitudinal5phase5space5distribution measured5with transverse5deflecting5structure5(TDS)
6 Christoph Lechner, University of Hamburg
Introduction Lasing Suppression July 2014 Studies .
7 Christoph Lechner, University of Hamburg
Introduction Lasing Suppression July 2014 Studies .
focusing channel and chicane can amplify initial density fluctuations
8 Christoph Lechner, University of Hamburg
Introduction Lasing Suppression July 2014 Studies .
focusing channel dedicated chicane shot noise
longitudinal electric field
→ plasma oscillation → growth of energy modulation driven by field
→ bunching after chicane can be stronger than initial bunching
9 Christoph Lechner, University of Hamburg
Introduction Lasing Suppression July 2014 Studies .
longitudinal electric field
→ plasma oscillation → growth of energy modulation driven by field
→ bunching after chicane can be stronger than initial bunching
combination
9 Christoph Lechner, University of Hamburg
Introduction Lasing Suppression July 2014 Studies .
Marinelli, et al. [5th MBI WS; Phys Rev Lett 110, 264802 (2013)]
Seletskiy, et al. [X. Yang, this workshop; Phys Rev Lett
111, 034803 (2013)]:
photo-injector
THz generation observed
[Fig 3 from Seletskiy, et al., PRL 111, 034803 (2013) removed]
10 Christoph Lechner, University of Hamburg
Introduction Lasing Suppression July 2014 Studies .
LongitudinalPPos.PzP[m] EnergyPDeviationP[eV] −1 −0.5 0.5 1 x 10
−5
−8 −6 −4 −2 2 4 6 8 xP10
5
longitudinalPpos.P[µm]
10 energyPdeviationP[MeV] 0.8
0.6 0.4 0.2 LongitudinalPPos.PzP[m] EnergyPDeviationP[eV] −1 −0.5 0.5 1 x 10
−5
−6 −4 −2 2 4 xP10
6
longitudinalPpos.P[µm]
10 energyPdeviationP[MeV]
4 2
Simulation: M. Dohlus
11 Christoph Lechner, University of Hamburg
Introduction Lasing Suppression July 2014 Studies .
R56 = 40 µm, third chicane off)
from chicane to TDS)
transverse deflecting structure (TDS)
TexText font size 1.5
Parameter Value electron energy E0 700 MeV peak current Ipk 0.3 kA rms bunch duration σt 0.3 ps laser pulse duration 200 fs FWHM
12 Christoph Lechner, University of Hamburg
Introduction Lasing Suppression July 2014 Studies .
200 fs long laser pulses
head tail 1.35 ps laser off R56=50 um R56=147 um R56=294 um
t E 1 MeV
13 Christoph Lechner, University of Hamburg
Introduction Lasing Suppression July 2014 Studies .
[figures removed]
In the limit of large gain, we expect σE,tot ∼ |R56| σE,tot =
E,LSCA + σ2 E,0 + σ2 E,PW
60 fs FWHM laser pulses
14 Christoph Lechner, University of Hamburg
Introduction Lasing Suppression July 2014 Studies .
SASE conditions (Ipk ≃ 0.9 kA)
23:15 23:16 23:17 23:18 23:19 23:20 50 100 time [hh:mm] FEL pulse energy [µJ]
15 Christoph Lechner, University of Hamburg
Introduction Lasing Suppression July 2014 Studies .
→ impact of any drifts removed
∆ω/ω0 = 0.0076 (on), energy reduction by factor of 3.
[figure removed]
16 Christoph Lechner, University of Hamburg
Introduction Lasing Suppression July 2014 Studies .
amplitude at expense of bunching
amplified initial modulation amplitude
after first chicane limited by slice energy spread
17 Christoph Lechner, University of Hamburg
Introduction Lasing Suppression July 2014 Studies .
[figure removed]
Reduced impact of laser in single-stage configuration
18 Christoph Lechner, University of Hamburg
Introduction Lasing Suppression July 2014 Studies .
longitudinal coordinate (fs) energy deviation (10−3) −500 500 −6 −4 −2 2 4 6 8 10 longitudinal coordinate (fs) energy deviation (10−3) −500 500 −6 −4 −2 2 4 6 8 10
For the relative timing with maximum SASE suppression effect, determine position of laser modulation using TDS
19 Christoph Lechner, University of Hamburg
Introduction Lasing Suppression July 2014 Studies .
longitudinal space charge amplification
characterize final longitudinal phase space distribution
20 Christoph Lechner, University of Hamburg
Introduction Lasing Suppression July 2014 Studies .
21 Christoph Lechner, University of Hamburg