20th Advanced Accelerator Concepts Workshop

6 Nov 2022, 15:00 → 11 Nov 2022, 17:10 America/New_York

Hyatt Regency Long Island

Mark Palmer (Brookhaven National Laboratory) , Navid Vafaei-Najafabadi (Stony Brook University)

The AAC’22 workshop is the 20th in a series of by-invitation biennial fora for intensive discussions on long-term research in advanced accelerator physics and technology. This research supports the development of capabilities for the basic sciences, from photon science to high energy physics, as well as the development of compact accelerators for industrial, medical and security applications.

AAC'22 will be organized into eight working groups covering the following topical areas:

1. Laser-Plasma Wakefield Acceleration 
2. Computation for Accelerator Physics
3. Laser and High-Gradient Structure-Based Acceleration
4. Beam-Driven Acceleration
5. Beam Sources, Monitoring, and Control
6. Laser-Plasma Acceleration of Ions
7. Radiation Generation and Advanced Concepts
8. Advanced Laser and Beam Technology and Facilities

Conference Home:  https://www.aac2022.org/

 

Sunday, 6 November

18:00 → 19:30 Welcome Reception

Monday, 7 November

10:20 → 10:40 Coffee Break

12:10 → 13:30 Lunch

13:30 → 15:00 WG7: Radiation Generation and Advanced Concepts: Session 1

Conveners: John Palastro (University of Rochester, Laboratory for Laser Energetics) , Julia Mikhailova

13:30 Seeded FEL lasing of the COXINEL beamline driven by the HZDR plasma accelerator

Laser Plasma Accelerators (LPAs), harnessing gigavolt-per-centimeter accelerating fields, can generate high peak current, low emittance and GeV class electron beams paving the way for the realization of future compact free-electron lasers (FELs). Here, we report on the commissioning of the COXINEL beamline driven by the HZDR plasma accelerator and experimental demonstration of FEL lasing at 270 nm in a seeded configuration[1]. Control over the radiation wavelength is achieved with an improved bandwidth stability. Furthermore, the appearance of interference fringes, resulting from the interaction between the phase-locked emitted radiation and the seed, confirms longitudinal coherence, representing a key feature of such a seeded FEL. These results are cross-checked with simulations, ELEGANT for beam optics and GENESIS for FEL radiation. We anticipate a navigable pathway toward smaller-scale free-electron lasers at extreme ultra-violet wavelengths.

[1] M. Labat, J.P. Couperus Cabadağ, A. Ghaith, A. Irman, “Seeded free-electron laser drive by a compact laser plasma accelerator” accepted Nature Photonics (2022)

Speaker: Dr Arie Irman (Helmholtz-Zentrum Dresden - Rossendorf, Bautzner Landstrasse 400, 01328 Dresden, Germany)

13:50 Multi-color operation via coherent harmonic generation in a plasma driven attosecond X-ray source

The ongoing Plasma-driven Attosecond X-ray source experiment (PAX) at FACET-II aims to produce coherent soft x-ray pulses of attosecond duration using a Plasma Wakefield Accelerator [1]. These kinds of X-ray pulses can be used to study chemical processes where attosecond-scale electron motion is important. As a future upgrade to this concept, we investigate scaling to shorter soft X-ray wavelength by cascading undulators tuned to higher harmonics of the fundamental in a coherent harmonic generation (CHG) configuration. This configuration leverages the increase in the bunching factor of the higher harmonics to produce radiation at the fifth and tenth harmonics, corresponding to radiation wavelengths of 2 nm and 1 nm. In this contribution, we consider two CHG schemes. The first consists of using three 20 period-long undulator stages tuned to the fundamental, the fifth harmonic, and the tenth harmonic respectively, while the second consists of 20 periods at the fundamental, then 40 at the tenth harmonic. We demonstrate in both of these schemes using undulators with retuned fundamental frequencies can produce TW-scale pulses of fifth and tenth harmonic radiation with tens of attosecond-scale pulse lengths, an order of magnitude shorter than current state-of-the-art attosecond XFELs.

[1] C. Emma, X.Xu et al APL Photonics 6, 076107 (2021)

Speaker: Rafi Hessami (SLAC National Accelerator Laboratory)

AAC_2022_talk_CHG.pptx

14:10 The Ion Channel Laser: Physics Advances and Experimental Plans

The ion channel laser (ICL) is an alternative to the free electron laser (FEL) that uses the electric fields in an ion channel rather than the magnetic fields in an undulator to transversely oscillate a relativistic electron beam and produce coherent radiation. The strong focusing force of the ion channel leads to a Pierce parameter more than an order of magnitude larger than the typical values associated with FELs. This allows the ICL to lase in an extremely short distance while using electron beams with an energy spread of up to a few percent. The ICL may thus be able to accommodate beams that can be produced by laser wakefield accelerators today. ICLs have several practical challenges, however, including stringent constraints on the beam’s transverse phase space and the creation of a wakeless ion channel of sufficient length. We discuss recent advances in the physics of the ion channel laser as well as experimental plans for the first demonstration of an optical wavelength ICL at SLAC’s FACET-II facility and to potential future x-ray laser devices.

Speaker: Claire Hansel (University of Colorado Boulder)

talk2.pptx

15:00 → 15:30 Coffee Break

15:30 → 17:00 WG7: Radiation Generation and Advanced Concepts: Session 2

Conveners: John Palastro (University of Rochester, Laboratory for Laser Energetics) , Julia Mikhailova

15:30 Status report on nonlinear Compton scattering study

Recent progress of fundamental study on nonlinear inverse Compton scattering (ICS) will be reported. Experiment has been performed in Brookhaven National Laboratory Accelerator Test Facility. Counter collision of TW CO2 laser and 60-70 MeV electron beam having 300 pC of charge per pulse induce clear structure of nonlinear electrodynamics in X-ray radiation characteristics. In addition, utilization of the near infrared YAG laser expands the study on bi-harmonic Compton interaction or general applications in medicine and material research at hard X-ray energy of 87.5 keV in single shot basis.

Speaker: Yusuke Sakai (University of California Los Angeles)

2022_AAC_StatusReportOfNonlinerICSvfinal.pdf

15:50 HIGH-BRILLIANCE COMPTON LIGHT SOURCES BASED ON CO2 LASERS

Inverse Compton scattering (ICS) from relativistic electron beams colliding with laser pulses can be used for relatively compact and affordable x-ray and gamma sources complementing conventional synchrotron light sources (SLSs). Several proposals have been put forward on converting electron accelerators to Inverse Compton Scattering (ICS) gamma sources. Different types of particle accelerators have been considered including superconducting energy recovery linacs (S-ERL) and a synchrotron storage rings. A common approach implies combining e-beams with near-IR solid state lasers operating at multi-megahertz repetition rate inside Fabri-Perot optical cavity.
We evaluate here a complementary method of using a long-wave-IR (LWIR) CO2 gas laser of a novel pulse-burst architecture by examples of perspective ICS sources based on a synchrotron accelerator DANE and an S-ERL CBETA, each paired either with a near-IR solid state laser or with CO2 gas laser. For each of these schemes, we show that a LWIR laser with its 15 kHz cumulative pulse repetition rate can produce average spectral fluxes and brightness competitive with the approach based on state-of-the-art multi-MHz solid state laser. Simultaneously, the LWIR laser driver will provide about four orders of magnitude higher x-ray peak characteristics. This can be achieved due to considerable increase in acting laser pulse energy, combined with an order of magnitude higher number of laser photons per Joule. Operated at 50-500 keV photon energy with peak brilliances 1020-1021 ph/s-mm2-mrad2-0.1%BW the proposed ICS sources will become indispensable for pump-probe and other ultra-fast material studies that require building up meaningful data sets from a single x-ray pulse at the energy scale of atomic interactions.

Speaker: Igor Pogorelsky (BNL)

WG7.pptx

WG7summaryIgor.pptx

16:10 Nonlinear Thomson Scattering with Ponderomotive Control

In nonlinear Thomson scattering, a relativistic electron reflects and reradiates the photons
of a laser pulse, converting optical light to x rays or beyond. While this extreme frequency
conversion offers a promising source for probing high-energy-density materials and
driving uncharted regimes of nonlinear quantum electrodynamics, conventional nonlinear
Thomson scattering has inherent trade-offs in its scaling with laser intensity. Here we
discover that the ponderomotive control afforded by spatiotemporal pulse shaping enables
novel regimes of nonlinear Thomson scattering that substantially enhance the scaling of
the radiated power, emission angle, and frequency with laser intensity. By appropriately
setting the velocity of the intensity peak, a spatiotemporally shaped pulse can increase the
power radiated by orders of magnitude. The enhanced scaling with laser intensity allows
for operation at significantly lower electron energies and eliminates the need for a high-energy electron accelerator. This material is based upon work supported by the Department
of Energy National Nuclear Security Administration under Award Number DE-NA0003856 and by OFES under Award Number DE-SC0019135 and DE-SC00215057.

Speaker: Dillon Ramsey (LLE/UR)

16:30 Superradiance and temporal coherence in the non-linear blowout regime

Well known light emitting mechanisms (e.g. betatron radiation and non-linear Thomson scattering) are based on the motion of single-particles. Experiments demonstrated that these mechanisms can lead to the emission of bright radiation bursts, with frequencies extending up to the x-rays and beyond. These sources have intrinsic limitations: the electron velocity is always lower than the speed of light, and the acceleration that can imparted to an electron is not arbitrary.

Here, we consider instead the radiation emitted by collective excitations such as plasma waves. We show theoretically that the trajectory of the centroid of a plasma fully determines the temporal coherence features of the emitted radiation, just as if it were a real particle executing the same trajectory. A key feature of this concept is that the trajectory of a collective excitation such as a plasma wave can be arbitrary: it can go faster than light and have arbitrarily large accelerations. Instead of relying on electric and magnetic fields to accelerate particles, these features are a result of a coordinated reorganisation of the light emitting medium.

To illustrate the concept, we performed 2D and 3D simulations using the particle-in-cell code OSIRIS (including the Radiation Diagnostic for OSIRIS - RaDiO) to purposefully design wave trajectories which are inaccessible to single particles, with both examples of broadband and narrow band emission. We show that a superluminal laser/plasma wakefield will generate an optical shock at the Cherenkov angle. The emission is superradiant for all frequencies, thus potentially leading to a plasma-based source of temporally coherent broadband radiation. In contrast, a laser propagating in a sinusoidally modulated plasma density profile results in a periodic motion of the plasma wave centroid that results in temporally coherent narrow-band emission. Here we observe the generation of temporally coherent harmonics at the double doppler shifted frequency of the plasma wave centroid trajectory. This leads to a narrow frequency spectrum and to temporally coherent emission up to 100-1000 times the plasma frequency.

Speaker: Bernardo Malaca (GoLP/Instituto Superior Técnico, University of Lisbon)

AAC_presentation_2022_v4.pdf

Tuesday, 8 November

10:00 → 10:30 Coffee Break

12:00 → 13:20 Lunch

15:00 → 15:30 Coffee Break/Exhibits

15:30 → 17:00 WG7: Radiation Generation and Advanced Concepts: Session 4

Conveners: John Palastro (University of Rochester, Laboratory for Laser Energetics) , Julia Mikhailova

15:30 Status and Prospects for the Plasma-drived Attosecond X-ray (PAX) source experiment at FACET-II

Plasma-driven light source development has recently made significant progress with multiple demonstrations of plasma-FEL gain [1-2] and the ongoing work of various facilities dedicated to plasma-FEL development [3]. In this contribution, we report on the status and prospects for one-such plasma-driven light source effort, the Plasma-driven Attosecond X-ray (PAX) experiment at FACET-II [4]. This unique experimental thrust seeks to compress electron beams generated by plasma accelerators to 10s of nm bunch length and use these beams as drivers for an attosecond X-ray source. This approach is motivated by the possibility to generate ultra-short (10s of as) high power (TW) X-ray pulses, as well as the order-of-magnitude increased tolerances of this method to emittance, energy spread and pointing jitter compared to a plasma-driven XFEL starting from noise. We present recent experimental developments in the process of demonstrating this concept at FACET-II and discuss potential extensions of this method to scale towards shorter wavelengths in the future.

[1] W. Wang et al Nature 595, 516 (2021)
[2] R. Pompili Nature 605, 659–662 (2022)
[3] C. Emma et al High Power Laser Science and Engineering, 2021, Vol. 9, e57 (2021)
[4] C. Emma et al APL Photonics 6, 076107 (2021)

Speaker: Claudio Emma

AAC2022PAX_talk.pdf

15:50 Laser-Plasma Acceleration Driven Electron Radiography of High Energy Density Materials on the OMEGA-EP Laser

Contact and projection electron radiography using a laser-plasma electron accelerator driven by the OMEGA-EP laser are shown for static targets. Initial electron radiographs of laser-driven foils are shown along with a discussion of future experiments and applications. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0003856 and the U.S. Department of Energy under Awards DE-SC00215057.

Speaker: Jessica Shaw (University of Rochester Laboratory for Laser Energetics)

Shaw_AAC2022.pdf

16:10 High Resolution Radiography with Self-Modulated and Blowout Regime Laser Wakefield Acceleration generated X-ray sources

We aim to develop a diagnostic capable of high spatio-temporal resolution, specifically to be used in High Energy Density Science (HEDS) experiments. A Self-Modulated laser wakefield acceleration (SM-LWFA) driven broadband X-ray source was observed at the Titan target area, Jupiter Laser Facility. The spectral range was between 10 KeV to > 1 MeV, and took advantage of Betatron, Inverse Compton Scattering, and Bremsstrahlung processes to create X-rays. In order to design an X-ray source we can apply to dynamic radiography in HEDS experiments, we must thoroughly examine spectral and spatial attributes. Our results include a comparison of spectral output and source size for each method of generating X-rays from SM-LWFA. An inertial confinement fusion hohlraum and modified Air force resolution target were imaged to demonstrate potential for applications. The radiographs are also used to determine the X-ray source size, or resolution capability. The modified Air Force target is approximated as a “knife edge” and the Fresnel diffraction formalism is used to model the diffraction pattern at different source sizes, and compare to the experimental data. In order to minimize error induced by misalignment in the z plane [1], a curved object (the hohlraum) was also used to determine source size. A modified X-ray ray tracing code creates a line out of a curved object radiograph. In the future, we will apply these analysis tools to compare blowout regime wakefield with other injection schemes and potentially SM-LWFA on the Texas Petawatt.

[1] R. Tommasini et al. POP 24, 053104 (2017).

Speaker: Isabella Pagano (UT Austin/LLNL)

Isabella Pagano AAC presentation 2022-1.pdf

16:30 High-energy two-color terahertz generation

A laser pulse composed of a fundamental and properly phased second harmonic exhibits an asymmetric electric field that can drive a time-dependent current of photoionized electrons. The current produces a near-single-cycle burst of terahertz (THz) radiation. Experiments using ~1-TW ultrashort laser pulses observe optimal THz energies (~10-uJ) when the “two-color” pulse undergoes filamentary propagation in low pressure gas. Here we use simulations to investigate the optimal conditions for two-color THz generation driven by >100-TW ultrashort laser pulses. Simple scalings indicate that the number of photoionized electrons is independent of gas pressure. As a result, use of a low-pressure, small nonlinear refractive index, high-ionization potential gas such as helium can mitigate multiple filamentation of the high-power pulse, while strengthening the field experienced by electrons at the instant of ionization, thereby increasing the current and THz energy. A high-energy (~1-mJ), THz source would enable access to a novel physics regime in which bound electron nonlinear optics and relativistic plasma physics coexist.

Speaker: Tanner Simpson (Laboratory for Laser Energetics, University of Rochester)

Wednesday, 9 November

10:00 → 10:30 Coffee Break/Exhibits

12:00 → 13:20 Lunch

Thursday, 10 November

10:00 → 10:30 Coffee Break/Exhibits

12:00 → 13:20 Lunch

15:00 → 18:00 Afternoon at Leisure

Friday, 11 November

10:00 → 10:30 Coffee Break

12:00 → 13:00 Lunch

14:40 → 15:00 Coffee Break