Preservation of low slice emittance in bunch compressors

Bettoni, S.; Aiba, M.; Beutner, Bolko; Pedrozzi, M.; Prat, Eduard; Reiche, S.; Schietinger, T.

doi:10.1103/physrevaccelbeams.19.034402

Cited by 14 publications

(11 citation statements)

References 18 publications

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“…VII for details). They have been shown to be reproducible within a few percent and stable under longitudinal bunch compression [187]. At the electron source, we have measured intrinsic emittance values close to the theoretical limit [44,165,166].…”

Section: Discussionsupporting

confidence: 58%

Commissioning experience and beam physics measurements at the SwissFEL Injector Test Facility

Schietinger¹,

Hauff²,

Pal³

et al. 2016

Phys. Rev. Accel. Beams

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The SwissFEL Injector Test Facility operated at the Paul Scherrer Institute between 2010 and 2014, serving as a pilot plant and testbed for the development and realization of SwissFEL, the X-ray Free-Electron Laser facility under construction at the same institute. The test facility consisted of a laser-driven rf electron gun followed by an S-band booster linac, a magnetic bunch compression chicane and a diagnostic section including a transverse deflecting rf cavity. It delivered electron bunches of up to 200 pC charge and up to 250 MeV beam energy at a repetition rate of 10 Hz. The measurements performed at the test facility not only demonstrated the beam parameters required to drive the first stage of an FEL facility, but also led to significant advances in instrumentation technologies, beam characterization methods and the generation, transport and compression of ultra-low-emittance beams. We give a comprehensive overview of the commissioning experience of the principal subsystems and the beam physics measurements performed during the operation of the test facility, including the results of the test of an in-vacuum undulator prototype generating radiation in the vacuum ultraviolet and optical range.

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Section: Discussionsupporting

confidence: 58%

Commissioning experience and beam physics measurements at the SwissFEL Injector Test Facility

Schietinger¹,

Hauff²,

Pal³

et al. 2016

Phys. Rev. Accel. Beams

Self Cite

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“…Little variation was seen in the GPT results with space-charge switched off. Comparisons between CSR simulations and experimental data have been studied previously [2][3][4], but only for moderate compression factors (up to around 15 at a given bunch compressor). Indeed, at moderate compression factors-up to around 15-20, at which point the bunch length approaches 100 fs, we see relatively good agreement between the codes and experimental data to within 10%.…”

Section: Resultsmentioning

confidence: 99%

“…The emission of coherent synchrotron radiation (CSR) on curved trajectories can present a significant issue for short electron bunches, such as those used in free electron lasers (FELs) [1][2][3][4][5]. CSR can degrade the quality of electron bunches through an increase in projected and slice emittance, and energy spread.…”

Section: Introductionmentioning

confidence: 99%

Beyond the limits of 1D coherent synchrotron radiation

et al. 2018

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An understanding of collective effects is of fundamental importance for the design and optimisation of the performance of modern accelerators. In particular, the design of an accelerator with strict requirements on the beam quality, such as a free electron laser (FEL), is highly dependent on a correspondence between simulation, theory and experiments in order to correctly account for the effect of coherent synchrotron radiation (CSR), and other collective effects. A traditional approach in accelerator simulation codes is to utilise an analytic one-dimensional approximation to the CSR force. We present an extension of the 1D CSR theory in order to correctly account for the CSR force at the entrance and exit of a bending magnet. A limited range of applicability to this solution-in particular, in bunches with a large transverse spot size or offset from the nominal axis-is recognised. More recently developed codes calculate the CSR effect in dispersive regions directly from the Liénard-Wiechert potentials, albeit with approximations to improve the computational time. A new module of the General Particle Tracer code was developed for simulating the effects of CSR, and benchmarked against other codes. We experimentally demonstrate departure from the commonly used 1D CSR theory for more extreme bunch length compression scenarios at the FERMI FEL facility. Better agreement is found between experimental data and the codes which account for the transverse extent of the bunch, particularly in more extreme compression scenarios.

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“…with the bunch head having a lower energy than the bunch tail) in the witness beam that allows bunch compression after a drift. Such wakefields have also been used for generation of THz pulses [28][29][30], beam acceleration [31,32] and manipulation [33][34][35][36][37][38][39][40][41]. The electron beam temporal profile is measured with a 5-cell c-band (5712 MHz) deflecting cavity at a screen (P1).…”

Section: Pacs Numbersmentioning

confidence: 99%

Few-femtosecond electron beam with terahertz-frequency wakefield-driven compression

Zhao

Jiang

et al. 2018

Phys. Rev. Accel. Beams

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We propose and demonstrate a novel method to produce few-femtosecond electron beam with relatively low timing jitter. In this method a relativistic electron beam is compressed from about 150 fs (rms) to about 7 fs (rms, upper limit) with the wakefield at THz frequency produced by a leading drive beam in a dielectric tube. By imprinting the energy chirp in a passive way, we demonstrate through laser-driven THz streaking technique that no additional timing jitter with respect to an external laser is introduced in this bunch compression process, a prominent advantage over the conventional method using radio-frequency bunchers. We expect that this passive bunching technique may enable new opportunities in many ultrashort-beam based advanced applications such as ultrafast electron diffraction and plasma wakefield acceleration. PACS numbers:Ultrashort electron beams are of fundamental interest in accelerator physics and ultrafast science communities. In x-ray free-electron lasers (FELs [1-3]), ultrashort electron beams with high peak current and low emittance are used to produce coherent and intense x-rays that have already opened new opportunities in many areas of science [4]. In keV and MeV ultrafast electron diffraction (UED [5-15]), ultrashort electron beams are used to probe the atomic structure changes in many nonequilibrium processes. In beam-driven plasma wakefield accelerator (PWFA [16,17]), ultrashort electron beams are essential for exciting the high-gradient plasma wakefield. Ultrashort electron beams are also important for producing intense terahertz (THz) pulses [18,19].For an electron beam that contains millions of electrons, Coulomb repulsion force tends to broaden the pulse width and in general ultrashort electron beams are obtained with bunch compression [20][21][22]. The process requires first a mechanism to imprint energy chirp (correlation between a particle's energy and its longitudinal position) in the beam longitudinal phase space and then sending the beam through a dispersive element such that the longitudinal displacement of the electrons is changed in a controlled way to yield a beam with shorter pulse width. The required energy chirp is typically established by accelerating the beam off-crest in radio-frequency (rf) cavities and the widely used dispersive elements are magnetic chicanes for ultra-relativistic electron beam and drifts for near-relativistic and sub-relativistic beams.The main drawback of this active bunching technique is that the phase jitter in the rf cavity will be converted into timing jitter after compression [23,24]. This is because the rf phase jitter leads to variation of the beam centroid energy, which is further translated to variation of time-of-flight after passing through a dispersive element. In this Letter, we demonstrate a passive bunching technique where an electron beam is compressed from about 150 fs (rms) to about 7 fs (rms, upper limit) with the wakefield produced by a leading drive beam in a dielectric tube. Furthermore, with laser-driven THz streaking tec...

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Preservation of low slice emittance in bunch compressors

Cited by 14 publications

References 18 publications

Commissioning experience and beam physics measurements at the SwissFEL Injector Test Facility

Commissioning experience and beam physics measurements at the SwissFEL Injector Test Facility

Beyond the limits of 1D coherent synchrotron radiation

Few-femtosecond electron beam with terahertz-frequency wakefield-driven compression

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