The Science and Technology of Undulators and Wigglers

Clarke, James

doi:10.1093/acprof:oso/9780198508557.001.0001

Cited by 165 publications

(127 citation statements)

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“…The wavelength λ of the radiation produced by an electron undergoing oscillations inside an undulator is λ = λ u 1 + K 2 /2 /2γ 2 , where λ u is the undulator period, γ is the Lorentz factor of the electron, and K is the undulator strength parameter. Presently, the undulator period is limited to >1 mm using conventional magnetic undulators [2]. Reducing λ u is highly beneficial as it will decrease the required electron energy for the same specified radiation wavelength and, hence, decrease the size of the light source.…”

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confidence: 99%

Plasma Undulator Based on Laser Excitation of Wakefields in a Plasma Channel

et al. 2015

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confidence: 99%

Plasma Undulator Based on Laser Excitation of Wakefields in a Plasma Channel

et al. 2015

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“…Undulators have a sinusoidal transverse magnetic field with an amplitude B 0 and period λ u that define the deflection parameter 19 K ∝ B 0 · λ u . In the rest frame of the relativistic electrons moving through this field, λ u is contracted by the Lorentz factor γ , which is defined as the total electron energy E in units of the electron rest energy m o c 2 .…”

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confidence: 99%

“…The wavelength of the second harmonic is slightly longer than half the fundamental owing to its emission characteristics. In contrast to the fundamental, its flux distribution is peaked off-axis 19 (Θ > 0) with correspondingly longer wavelengths according to equation (1). Owing to the horizontally focusing mirror, these components are propagated through the slit onto the detector, shifting the peak of the observed on-axis spectrum to longer wavelengths.…”

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confidence: 99%

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Laser-driven soft-X-ray undulator source

et al. 2009

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Synchrotrons and free-electron lasers are the most powerful sources of X-ray radiation. They constitute invaluable tools for a broad range of research 1 ; however, their dependence on largescale radiofrequency electron accelerators means that only a few of these sources exist worldwide. Laser-driven plasmawave accelerators 2-10 provide markedly increased accelerating fields and hence offer the potential to shrink the size and cost of these X-ray sources to the university-laboratory scale. Here, we demonstrate the generation of soft-X-ray undulator radiation with laser-plasma-accelerated electron beams. The well-collimated beams deliver soft-X-ray pulses with an expected pulse duration of ∼10 fs (inferred from plasma-accelerator physics). Our source draws on a 30-cmlong undulator 11 and a 1.5-cm-long accelerator delivering stable electron beams 10 with energies of ∼210 MeV. The spectrum of the generated undulator radiation typically consists of a main peak centred at a wavelength of ∼18 nm (fundamental), a second peak near ∼9 nm (second harmonic) and a highenergy cutoff at ∼7 nm. Magnetic quadrupole lenses 11 ensure efficient electron-beam transport and demonstrate an enabling technology for reproducible generation of tunable undulator radiation. The source is scalable to shorter wavelengths by increasing the electron energy. Our results open the prospect of tunable, brilliant, ultrashort-pulsed X-ray sources for small-scale laboratories.Resolving the structure and dynamics of matter on the atomic scale requires a probe with ångstrøm resolution in space and femtosecond to attosecond resolution in time. Third-generation synchrotron sources produce X-ray pulses with durations of typically a few tens of picoseconds and can achieve 100 fs by using complex beam-manipulation techniques 12,13 . They have already proven their capability of imaging static structures with atomic (spatial) resolution 1 and upcoming X-ray free-electron lasers hold promise for also extending the temporal resolution into the atomic/sub-atomic range [14][15][16][17][18] . Both of these sources consist of an electron accelerator and an undulator, which is a periodic magnetic structure that forces the electrons to oscillate and emit radiation 19 . Whereas current facilities require a kilometre-scale accelerator, new laser-plasma accelerators offer the potential for a marked reduction in size and cost as well as pulse durations of a few femtoseconds.Femtosecond-laser-driven plasma accelerators have produced quasi-monoenergetic electron beams 2-7 with energies up to 1 GeV (refs 8, 9, 20, 21) from centimetre-scale interaction lengths. The concept is based on an ultra-intense laser pulse, which ionizes atoms of a gas target and excites a plasma wave. This trails the pulse at 1 Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Str. 1, 85748 Garching, Germany, 2 Department für Physik, Ludwig-Maximilians-Universität, Am Coulombwall 1, 85748 Garching, Germany, 3 Forschungszentrum Dresden-Rossendorf, Bautzner Landstraße 128, 01328 Dresden, Germany, 4 ...

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“…This fact has to be taken into account to compute the power spectrum of undulator spontaneous emission. Inside the cone, the angular power density is given by [20]:…”

Section: ) Optical Transition Radiation (Otr) Is Emitted When a Beammentioning

confidence: 99%

A Proof-of-Principle Echo-enabled Harmonic Generation Free Electron Laser Experiment at SLAC

Pernet

2010

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With the advent of X-ray Free Electron Lasers (FELs), new methods have been developed to extend capabilities at short wavelengths beyond Self-Amplified Spontaneous Emission (SASE). In particular, seeding of a FEL allows for temporal control of the radiation pulse and increases the peak brightness by orders of magnitude. Most recently, Gennady Stupakov and colleagues at SLAC proposed a new technique: Echo-Enabled Harmonic Generation (EEHG). Here a laser microbunches the beam in an undulator and the beam is sheared in a chicane. This process is repeated with a second laser, undulator and chicane. The interplay between these allows a seeding of the X-ray laser up to the 100th harmonic of the first laser. After introducing the physics of FELs and the EEHG seeding technique, we describe contributions to the experimental effort. We will present detailed studies of the experiment including the choice of parameters and their optimization, the emittance effect, spontaneous emission in the undulators, the second laser phase effect, and measurements of the jitter between RF stations. Finally, the status and preliminary results of the Echo-7 experiment will be outlined.

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The Science and Technology of Undulators and Wigglers

Cited by 165 publications

References 0 publications

Plasma Undulator Based on Laser Excitation of Wakefields in a Plasma Channel

Plasma Undulator Based on Laser Excitation of Wakefields in a Plasma Channel

Laser-driven soft-X-ray undulator source

A Proof-of-Principle Echo-enabled Harmonic Generation Free Electron Laser Experiment at SLAC

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