X-Ray Sources from Laser-Plasma Acceleration: Development and Applications for High Energy Density Sciences

X-ray sources from laser-plasma acceleration: development and applications for high energy density sciences

HEDS Center Seminar

Presented by Félicie Albert [email protected] LLNL May 9th 2019

LLNL-PRES-741326 This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344. Lawrence Livermore National Security, LLC Collaborators

N. Lemos, P. M. King, B. B. Pollock, C. Goyon, A. Pak, J. E. Ralph, Y. Ping, A. Fernandez-Panella, S. Hau-Riege, T. Ogitsu, J. D. Moody

K.A. Marsh, C.E. Clayton, and C. Joshi (UCLA) B. Barbrel, J. Gaudin, F. Dorchies (CELIA)

S. Mangles, J. Woods, K. Powder, N. very preliminaryE. Galtier, P. Heimannanalysis, E. Granados, of shock H. J. dataLee, B. Nagler, A. Fry (LCLS) Lopes, E. Hill, S. Rose, Z. Najmudin (Imperial College London)

1.6 W. Schumaker, F. Fiuza, E. Gamboa, L. Fletcher, S.H Glenzer (SLAC SIMES) A. Saunders, D. Kraus, R.W. Falcone (LBNL) 1.4 P. M. King, B. M. Hegelich (UT Austin) P. Zeitoun (LOA) shocked 1.2 A. Ravasio, F. Condamine, M. Koenig (LULI) J. Shaw, D. H. Froula (LLE) intensity a.u. 1 J. Hinojosa, A.G.R. Thomas unshocked

0.8 −100 0 100 200 300 400 500 pixel number 2 F. Albert – HEDS seminar – May 9th 2019

• Lineout clearly reveals shock front – and possibly the density difference??

RAL 2014 [email protected] X-ray sources are widely used to probe high energy density science experiments

X-ray sources – Picosecond phenomena Barrios et al, HEDP 9, 626 (2013) 1013 - Radiography Sandia Z – 3 ns Line emission Ê - X-ray diffraction NIF – 1 ns 11 10 Ê Ping et al 84, RSI 123105 (2013)

Ê - X-ray absorption spectroscopy ps ê 109 Bailey et al, Nature 517, 56 (2015) Sr ê - X-ray opacity eV ê Broadband 107 emission Jarrott et al, POP 21 031201 (2014) OMEGA – 100 ps Photons

5 10 Bremsstrahlung Titan – 10 ps

1 2 5 10 20 50 100 Photon energy keV

@ D 3 F. Albert – HEDS seminar – May 9th 2019 We are developing x-ray sources based on laser-plasma acceleration to fill a gap in HED science

Ê - X-ray absorption spectroscopy ps ê 109 Bailey et al, Nature 517, 56 (2015) Sr

ê Betatron radiation - X-ray opacity eV ps LWFA ê Broadband 107 emission Jarrott et al, POP 21 031201 (2014) OMEGA – 100 ps Photons

5 10 Bremsstrahlung Albert et al, PRL 118, 134801 (2017) Titan – 10 ps Albert et al, PRL 111, 235004 (2013) Lemos et al, PPCF 58 034108 (2016) 1 2 5 10 20 50 100 Lemos et al, PRL (in review) Photon energy keV

@ D 4 F. Albert – HEDS seminar – May 9th 2019 Outline

§ Laser-plasma acceleration: an alternative for high brightness x-ray sources § Self modulated and blowout laser-wakefield acceleration regimes for high brightness x-ray source development § X-ray source development at LLNL and applications § Betatron x-ray source development at LCLS and applications § Conclusion and perspectives

5 F. Albert – HEDS seminar – May 9th 2019 Outline

6 F. Albert – HEDS seminar – May 9th 2019 Conventional x-ray light sources are large scale national facilities

X-ray free electron laser: LCLS Synchrotron: APS

3 km

SLAC, CA Argonne Nat. Lab., IL

7 F. Albert – HEDS seminar – May 9th 2019 Sources driven by laser-plasma accelerators offer an alternative

Synchrotron Free Electron Laser Laser-plasma

APS LCLS

> 1km

Electrons from storage ring Electrons from linac wiggled Electrons from laser-produced wiggled by undulators by undulators plasma wiggled by plasma ✓Hard X-rays ✓Soft X-rays (8 keV) ✓Hard X-rays (up to MeV) ✓High brightness ✓Very High brightness ✓High brightness ✓Multiple beamlines ✓One beamline ✓Small scale ✓Not ultrafast (ps) ✓Ultrafast (fs) ✓Ultrafast (fs) ✓Not coherent ✓Coherent ✓Some spatial coherence

F. Albert, Laser wakefield accelerators: Next Generation Light Sources, Optics and Photonics News, 29, 1, 42-49 (2018)

8 F. Albert – HEDS seminar – May 9th 2019 Plasmas can naturally sustain large acceleration gradients

RF Cavity Gas cell – laser plasma

100 MV/m 100 GV/m

Acceleration gradient Plasma frequency 2 mcω p nee 18 −3 E0 = ω p = ne =10 cm → E0 = 96 GV/m e mε0

9 F. Albert – HEDS seminar – May 9th 2019 Intense laser pulses drive electron plasma waves

Wake behind a boat Plasma wave behind a laser

Width of human hair

Nuno Lemos, LLNL

10 F. Albert – HEDS seminar – May 9th 2019 Intense laser pulses drive electron plasma waves

Wake behind a boat Plasma wave behind a laser

Width of~50 human µm hair

Nuno Lemos, LLNL

11 F. Albert – HEDS seminar – May 9th 2019 Intense laser pulses drive electron plasma waves

Wake behind a boat Plasma wave behind a laser

~50 µm

Nuno Lemos, LLNL

12 F. Albert – HEDS seminar – May 9th 2019 Laser pulse

Electron plasma wave

F. Albert et al, Laser wakefield accelerator based light sources: potential applications and requirements, Plasma Phys. Control. Fusion 56 084015 (2014)

13 F. Albert – HEDS seminar – May 9th 2019 Trapped Electron

Laser pulse

Electron plasma wave

F. Albert et al, Laser wakefield accelerator based light sources: potential applications and requirements, Plasma Phys. Control. Fusion 56 084015 (2014)

14 F. Albert – HEDS seminar – May 9th 2019 Trapped Electron

Laser pulse

Electron plasma wave

F. Albert et al, Laser wakefield accelerator based light sources: potential applications and requirements, Plasma Phys. Control. Fusion 56 084015 (2014)

15 F. Albert – HEDS seminar – May 9th 2019 Trapped Electron

Laser pulse

Betatron X-ray beam Electron plasma wave

F. Albert et al, Laser wakefield accelerator based light sources: potential applications and requirements, Plasma Phys. Control. Fusion 56 084015 (2014)

16 F. Albert – HEDS seminar – May 9th 2019 Trapped Electron

Laser pulse

20 mrad Betatron X-ray beam � Electron plasma wave � Beam divergence � ~ �

F. Albert et al, Laser wakefield accelerator based light sources: potential applications and requirements, Plasma Phys. Control. Fusion 56 084015 (2014)

17 F. Albert – HEDS seminar – May 9th 2019 Trapped Electron

Laser pulse .] Ec a.u Intensity [ Intensity X-ray energy [keV] Betatron X-ray beam Electron plasma wave � �� Critical energy Ec ~

F. Albert et al, Laser wakefield accelerator based light sources: potential applications and requirements, Plasma Phys. Control. Fusion 56 084015 (2014)

18 F. Albert – HEDS seminar – May 9th 2019 Laser wakefield acceleration can produce x-ray and gamma-ray sources using several processes Electron X-rays 1 Betatron x-ray radiation keV

Scattered photon 2 Compton scattering Electron keV – MeV Laser photon

Gamma-ray photon 3 Bremsstrahlung Electron + MeV Nucleus

19 F. Albert – HEDS seminar – May 9th 2019 X-ray sources from LWFA have unique properties compared to conventional light sources

1017 Unique properties § Broadband (keV - MeV) APS (SPX)

BW " § Ultrafast (fs-ps) 1014 LCLS 0.1 " s #

# § Collimated (mrad)

11 § Small source size (µm)

! photons 10 § Synchronized with drive laser or XFEL within

ALS (slicing) 105 1 5 10 50 100 500 1000 X!ray energy keV

! "

20 F. Albert – HEDS seminar – May 9th 2019 X-ray sources from LWFA have unique properties compared to conventional light sources

1017 Unique properties § Broadband (keV - MeV) APS$(SPX)$ BW " 14 § Ultrafast (fs-ps) PlasmaLCLS$ Phys. Control. Fusion 56 (2014) 084015 X-ray ImagingFAlbertet al 10 parameter increases, the photon spectrum tends towards a synchrotron-like broad spectrum, extending to much higher photon energies than the shifted fundamental. The emission of photons in such processes clearly 0.1 " indicates that a force is applied to the electron to conserve momentum. This radiation force has a classical form, which is Gamma-ray s # self-consistent within the limits that the acceleration timescale # 2 3 23 § Collimated (mrad) is much larger than τ0 2e /3mc 6.3 10− s[58], = = × XPCI& 264101-3 Ben-Ismail et al. Appl. Phys. Lett. 98, 264101 (2011) which is principally a damping of motion due to loss of radiography dense object radiography with the demonstrated gamma-ray momentum to the radiation. One of the interesting phenomena source. In summary, experimental results from a high-quality arising from this laser-electron interaction is that the radiation gamma-ray source were detailed in this article. This source was achieved using a compact laser-plasma accelerator. The damping is theoretically predicted to be so extreme that for a gamma-ray source size was measured and reveals a value in sufficiently intense laser, the electron beam may lose almost all the range of 30 lm. Such excellent resolution was obtained by using the optimum parameters (geometry and thickness of its energy in the interaction time [59–61]. This means that the the convertor) resulting from previous numerical studies.18 The presented gamma-ray sources, with such high tem- radiation force is comparable to the accelerating force, which perature, dose, and 10 lm-range size, are beneficial for fast and ultra-precise radiographies for example in automotive has the implication that the spectrum of the radiation should and aeronautics industries. These sources have the capability to identify sub-millimetric manufacturing defects, such as § 11 be strongly modified. cracks, incomplete welds and other flaws that develop during Small source size (µm) service. These gamma-ray sources are also an alternative for line ! photons 10 radiations such as K line radiations produced when intense a Absorption3. Review ofspectroscopy x- and γ-ray applications laser pulses irradiated a solid target. Such radiations are emitted in all directions and require a large amount of energy (in the 100 J level) to be useful for the case of imploding capsule radiograph. The source characteristics presented in This section discusses three specific promising applications this paper show that this required level of laser energy could be significantly reduced by keeping the same imaging qual- of laser–plasma accelerator-based light sources: x-ray phase ity. In addition, according to numerical simulations, the du- Figure 3. Single-shot x-ray phase contrast image of a cricket taken ration of the studied gamma-ray pulse is expected to be in contrast imaging (XPCI), x-ray absorption spectroscopy, and the sub-picosecond range. This duration makes this source using the Astra Gemini Laser. This 200 TW laser produces 1 GeV also of interest for the dynamical studies of imploding pellets nuclear resonance fluorescence (NRF). While this list is not electron beams and very hard x-rays (with critical energy > 30 keV). in inertial confinement fusion experiments (studies of implo- X"ray&absorp+on&intended to be exhaustive, here we describe the basic principles The image shows minimal absorption, indicative of high flux of sion stability, hydrodynamics instabilities, etc…). The authors acknowledge collaboration with Mr. Loic § Synchronized with drive laser of these applications and discuss ongoing and future efforts photons at energies > 20 keV, for which the phase-shift cross-section Le-Dain from CEA-DAM Bruye`res-le-Chatel. This work has to improve them with either betatron radiation or Compton greatly exceeds (> 100 ) that for absorption. been partially supported by ERC contract “PARIS”, by × AIMA OSEO contract and by DGA Contract No. 06.34.013. FIG. 4. (Color online) (a) Photo of the 20 mm diameter tungsten object, scattering from laser–plasma accelerators. (b) a schematic A-A cut, and (c) the resulting radiograph with the optimized 1 0 T. Tajima and J. Dawson, Phys. Rev. Lett. 43, 267 (1979). gamma-ray source. 2 phase contrast radiography using x-pinch radiation [67]. Even V. Malka et al., Science 1596, 298 (2002). 3S. P. D. Mangles et al., Nature 431, 535 (2004). 4 though, as suggested by equation (4), it is suitable to use a The demonstrated spatial and spectral qualities of our C. G. R. Geddes et al., Nature 431, 538 (2004). 5J. Faure et al., Nature 431, 541 (2004). 3.1. X-ray phase contrast imaging gamma-ray source satisfy totally the necessary conditions 6J. Faure et al., Nature 444, 737 (2006). monochromatic x-ray source for XPCI, polychromatic sources for radiography of dense objects with very high resolution. 7C. Rechatin et al., Phys. Rev. Lett. 102, 164801 (2009). 8 or XFEL within

! "

21 F. Albert – HEDS seminar – May 9th 2019 The sources and techniques we are developing are important for applications in HED science

1017 Applications § High pressure and shock APS$(SPX)$ physics BW " 14 PlasmaLCLS$ Phys. Control. Fusion 56 (2014) 084015 X-ray ImagingFAlbertet al 10 parameter increases, the photon spectrum tends towards a synchrotron-like broad spectrum, extending to much higher photon energies than the shifted fundamental. The emission of photons in such processes clearly § 0.1 " Equation of state indicates that a force is applied to the electron to conserve momentum. This radiation force has a classical form, which is Gamma-ray s # self-consistent within the limits that the acceleration timescale

# 2 3 23 is much larger than τ0 2e /3mc 6.3 10− s[58], = = × XPCI& 264101-3 Ben-Ismail et al. Appl. Phys. Lett. 98, 264101 (2011) which is principally a damping of motion due to loss of radiography dense object radiography with the demonstrated gamma-ray momentum to the radiation. One of the interesting phenomena source. In summary, experimental results from a high-quality arising from this laser-electron interaction is that the radiation gamma-ray source were detailed in this article. This source was achieved using a compact laser-plasma accelerator. The damping is theoretically predicted to be so extreme that for a gamma-ray source size was measured and reveals a value in sufficiently intense laser, the electron beam may lose almost all the range of 30 lm. Such excellent resolution was obtained by using the optimum parameters (geometry and thickness of § 18 Material strength its energy in the interaction time [59–61]. This means that the the convertor) resulting from previous numerical studies. The presented gamma-ray sources, with such high tem- radiation force is comparable to the accelerating force, which perature, dose, and 10 lm-range size, are beneficial for fast and ultra-precise radiographies for example in automotive has the implication that the spectrum of the radiation should and aeronautics industries. These sources have the capability to identify sub-millimetric manufacturing defects, such as 11 be strongly modified. cracks, incomplete welds and other flaws that develop during service. These gamma-ray sources are also an alternative for line ! photons 10 radiations such as K line radiations produced when intense a Absorption3. Review ofspectroscopy x- and γ-ray applications laser pulses irradiated a solid target. Such radiations are emitted in all directions and require a large amount of energy (in the 100 J level) to be useful for the case of imploding capsule radiograph. The source characteristics presented in This section discusses three specific promising applications this paper show that this required level of laser energy could be significantly reduced by keeping the same imaging qual- of laser–plasma accelerator-based light sources: x-ray phase ity. In addition, according to numerical simulations, the du- § Phase transitions Figure 3. Single-shot x-ray phase contrast image of a cricket taken ration of the studied gamma-ray pulse is expected to be in contrast imaging (XPCI), x-ray absorption spectroscopy, and the sub-picosecond range. This duration makes this source using the Astra Gemini Laser. This 200 TW laser produces 1 GeV also of interest for the dynamical studies of imploding pellets nuclear resonance fluorescence (NRF). While this list is not electron beams and very hard x-rays (with critical energy > 30 keV). in inertial confinement fusion experiments (studies of implo- X"ray&absorp+on&intended to be exhaustive, here we describe the basic principles The image shows minimal absorption, indicative of high flux of sion stability, hydrodynamics instabilities, etc…). The authors acknowledge collaboration with Mr. Loic of these applications and discuss ongoing and future efforts photons at energies > 20 keV, for which the phase-shift cross-section Le-Dain from CEA-DAM Bruye`res-le-Chatel. This work has to improve them with either betatron radiation or Compton greatly exceeds (> 100 ) that for absorption. been partially supported by ERC contract “PARIS”, by × AIMA OSEO contract and by DGA Contract No. 06.34.013. FIG. 4. (Color online) (a) Photo of the 20 mm diameter tungsten object, scattering from laser–plasma accelerators. (b) a schematic A-A cut, and (c) the resulting radiograph with the optimized 1 0 T. Tajima and J. Dawson, Phys. Rev. Lett. 43, 267 (1979). gamma-ray source. 2 phase contrast radiography using x-pinch radiation [67]. Even V. Malka et al., Science 1596, 298 (2002). 3S. P. D. Mangles et al., Nature 431, 535 (2004). 4 though, as suggested by equation (4), it is suitable to use a The demonstrated spatial and spectral qualities of our C. G. R. Geddes et al., Nature 431, 538 (2004). 5J. Faure et al., Nature 431, 541 (2004). 3.1. X-ray phase contrast imaging gamma-ray source satisfy totally the necessary conditions 6J. Faure et al., Nature 444, 737 (2006). monochromatic x-ray source for XPCI, polychromatic sources for radiography of dense objects with very high resolution. 7C. Rechatin et al., Phys. Rev. Lett. 102, 164801 (2009). We have used the optimised gamma-ray source to radio- 8W. P. Leemans et al., Nat. phys. 2, 696 (2006). § with high spatial coherence can also be used [68, 69]. In 9S. Kneip et al., Phys. Rev. Lett. 103, 035002 (2009). Opacity graph a complex and dense tungsten object. This object is 10 XPCI records the modifications of the phase of an x-ray beam D. H. Froula et al., Phys. Rev. Lett. 103, 215006 (2009). this case, the scheme is much simpler and does not require spherical, hollow, and etched on the inner part with sinusoi- 11N. A. M. Hafz et al., Nature Photon. 2, (2008). as it passes through a material, as opposed to its amplitude dal structures with cylindrical symmetry (cf., Figs. 4(a) and 12A. Giulietti et al., Phys. Rev. Lett. 101, 105002 (2008). 13 4(b)). R. D. Edwards et al., Appl. Phys. Lett. 80, 12 (2002). recorded with conventional x-ray radiography techniques. using complex and expensive x-ray optics. Much of the 14Y. Glinec et al., Phys. Rev. Lett. 94, 025003 (2005). The spherical object with 20 mm diameter was placed 15C. Courtois et al., Phys. Plasmas 18, 023101 (2011). sources currently used for XPCI do not have a high temporal on the laser axis, at 60 cm from the convertor and imaged on 16S. Semushin and V. Malka, Rev. Sci. Instrum. 72, 7 (2001). 8 When x-rays pass through matter, elastic scattering causes a 17 the imaging plate phosphor screen with a magnification of a Y. Glinec et al., Rev. Sci. Instrum. 77, 103301 (2006). 18 resolution desirable to take snapshots of laser-driven shocks Compton$factor 3. The resulting experimental image is shown on Fig. A. Ben-Ismaı¨l et al., Nucl. Instrum. Methods Phys. Res. A, 629 382 phase shift of the wave passing through the object of interest. (2011). 10 4(c). The clear details of the inner sinusoidal lobes confirm 19G. W. Forbes, J. Opt. Soc. Am. A , 1943 (1988). 5 The cross-section for elastic scattering of x-rays in low-Z or other phenomena. XPCI measurements of shocks done the 30 lm-level resolution and validate the possibility of 20S. Agostinelli et al., Nucl. Instrum. Methods Phys. Res. A 506,(2003). elements is usually much greater than for absorption [62]. The at synchrotrons were limited to a temporal resolution of total phase shift induced on an x-ray wave when it travels a 100 ps [70]; betatron x-ray radiation, where the source ∼ distance z through a sample with complex index of refraction size is less than a few micrometers [38], has the potential § Laboratory astrophysics n 1 δ +iβ is due to the real part of the index and calculated to offer three orders of magnitude better time resolution. = − This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP: with the relation: For a source size of 2 µm and a critical energy of 8 keV, 128.15.43.113 On: Mon, 04 Jan 2016 19:56:07 z the transverse coherence length of betatron radiation was Average X ! ray flux 2π $(z) δ(x)dx, (4) measured at L 3 µm 5 cm away from the source, which = λ trans !0 is sufficient to observe= Fresnel diffraction fringes [37]. Using where λ is the x-ray wavelength. For two distinct low-Z free spaceBetatron propagation techniques,$ proof-of-principle XPCI elements, the difference in the real part of the complex index of measurements of biological samples have recently been done refraction is much larger than the difference in the imaginary [9, 10] with betatron radiation. These promising results have part. It means that for quasi transparent objects such as led to an extension of this technique to higher x-ray energies biological samples or tissues, this technique is more sensitive [71], with an example shown in figure 3. to small density variations, and offers better contrast than To generate a single-shot image, a large photon number conventional radiography.ALS$(slicing)$ For the past decade, XPCI has is required. As an approximate threshold, a megapixel 5 been a very active topic of research for medical, biological, (1024 1024 pixels) is a reasonable number of elements to and industrial applications. Consequently, several XPCI 10 make× an image. The relative fluctuations from Poisson techniques have been developed based on interferometry [62], gratings [63]andfreespacepropagation[64]. In combination statistics will scale as 1/ N ij , where N ij is the average number of detected photons per pixel. Therefore, for a Target with these techniques, XPCI has been done with various x-ray " Drive laser sources. Examples includes images of a small fish recorded low noise image the number of photons per shot should be with a standard x-ray tube and gratings [65], images of a N 106, assuming the x-rays uniformly fill the detector and 1bee obtained with a Mo K-alpha laser-based5 source [66] and10are≫ detected. In practice N 108 is50 more realistic, given100 500 1000 ≫ X!ray4 energy keV

probe ! "

22 F. Albert – HEDS seminar – May 9th 2019 Outline

23 F. Albert – HEDS seminar – May 9th 2019 LWFA light sources are typically produced with ultrashort laser pulses in the blowout regime (cτ ~ lp/2)

cτ density -

e 1/2 0 lp=c/ωp~ 1/ne

19 -3 30 fs ne~ 10 cm 1/2 Condition to be in the blowout regime cτ ~ 1/ne

16 -3 1 ps ne~ 10 cm

30 fs Pc~ 2 TW 2 To drive a wake we need P > Pc~ 1/ne ~ τ

1 ps Pc~ 2 PW

24 F. Albert – HEDS seminar – May 9th 2019 Self modulated laser wakefield acceleration (SMLWFA) is easier to achieve with picosecond scale lasers (cτ >> lp)

cτ density -

e 1/2 0 lp=c/ωp~ 1/ne

1/2 19 -3 Condition to be in the self modulated regime cτ >>~ 1/ne 1 ps ne~ 10 cm

To drive a wake we need P > Pc~ 1/ne 1 ps Pc~ 2 TW

25 F. Albert – HEDS seminar – May 9th 2019 The laser propagates in the plasma and decays into an electron plasma wave and forward scattered waves

cτ density -

e 1/2 0 lp=c/ωp~ 1/ne

lp Plasma wave Matching conditions ω0=ωs +/-mωplasma k0 = ks +/-mkplasma

Laser pulse envelope

cτLaser

26 F. Albert – HEDS seminar – May 9th 2019 The index of refraction variations due to the plasma wave cause the laser to focus/defocus

cτ density -

e 1/2 0 lp=c/ωp~ 1/ne

lp Plasma wave

Laser pulse envelope

cτLaser

27 F. Albert – HEDS seminar – May 9th 2019 This beat pattern exerts a force on the plasma electrons and the plasma wave amplitude grows until wave breaking

cτ density -

e 1/2 0 lp=c/ωp~ 1/ne

lp Plasma wave

Laser pulse envelope

cτLaser

28 F. Albert – HEDS seminar – May 9th 2019 Upon wave breaking electrons are trapped into the plasma wave

cτ density -

e 1/2 0 lp=c/ωp~ 1/ne

lp Plasma wave

Laser pulse envelope

cτLaser

29 F. Albert – HEDS seminar – May 9th 2019 Trapped electrons undergo acceleration in the longitudinal field of the plasma wave

ne E z decelerating cτ 0 density -

e 1/2 0 accelelerating lp=c/ωp~ 1/ne

lp Plasma wave

Laser pulse envelope

cτLaser

30 F. Albert – HEDS seminar – May 9th 2019 Electrons trapped in plasma wave are accelerated to relativistic energies

ne E z decelerating cτ 0 density -

e 1/2 0 accelelerating lp=c/ωp~ 1/ne Electron acceleration Longitudinal E field from plasma wave: self-modulated wakefield acceleration (SMLWFA)1

Electrons overlap with laser field: direct laser acceleration (DLA)2, dominant if I>1020 W/cm2

Electrons trapped into several plasma wave periods: 1 continuous energy spectrum Modena et al, Nature (1995), Joshi et al, PRL (1984) 2 S. Mangles et al, PRL (2006), Gahn et al, PRL (1999)

31 F. Albert – HEDS seminar – May 9th 2019 Electrons trapped off-axis undergo betatron oscillations, reinforced by overlap with laser field

ne E z decelerating cτ 0 density -

e 1/2 0 accelelerating lp=c/ωp~ 1/ne Electron acceleration Betatron oscillations

Longitudinal E field from plasma Energy (MeV) ρ[eωp2/c2] 7 wave: self-modulated wakefield 0 75 150 225 300 x10 10-1 B E 1 )|

acceleration (SMLWFA) 2 10 136 A 10-2 136 D 10-3 8 |FFT(E c)]

Electrons overlap with laser field:-4 2 102 10 102 π

2 6 8 10 12 14 /( m) 2 direct laser acceleration (DLA) , m) 6 μ

k(x )[ /c] μ 1 ωp [e (

20 2 ( 2 68 Ω dominant if I>10 W/cm 2 68 x d x 10 C ω 4 10-1 34 34 W/d Electrons trapped into several 2 10-3 d 2

plasma0 wave periods: #parts(a.u) 0 0 continuous2860 3044 energy3219 spectrum3394 0 100 200 300 840 1680 2520 3360 0 20 40 60 80 100 120 x1 (μm) Energy (MeV) x1 (μm) Energy (keV)

32 F. Albert – HEDS seminar – May 9th 2019 Outline

33 F. Albert – HEDS seminar – May 9th 2019 Our work is part of a plan to develop LWFA-driven sources on large picosecond lasers Titan OMEGA-EP Energy: 150 J Energy: 400 J Pulse duration: 0.7 ps Pulse duration: 1 ps F/10 F/2

ü Experiments done ü 2 shot days in 2019 NIF-ARC LMJ-PETAL Energy: 250 J /beamlet Energy: 2 kJ Pulse duration: 1 ps Pulse duration: 0.5 ps ~ F/ 30 x 60 ~ F/40

Collaboration with CEA

ü 2 Shot days 2019-2020 ü Proposal short listed

34 F. Albert – HEDS seminar – May 9th 2019 Laser Wakefield Acceleration on Titan

Self modulated Titan Laser cτ 150 J ω ~ 1/n 1/2 0.7 ps lp=c/ p e

Target S. Andrews 3 -10 mm He jet (JLF) B. Pollock ne = 1019 cm-3 F. Albert

F/10 OAP 2.5 m focal length A. Saunders N. Lemos

W. Schumaker

C. Goyon J. Shaw

86 % in 28 µm 18 2 I = 5x10 W/cm 35 F. Albert – HEDS seminar – May 9th 2019 We have demonstrated the production of betatron radiation in the blowout and self-modulated regimes

70 Electron Interferometer 90 spectrometer

150

MeV 0

Detector (IP0 or500 CCD)

0 500 1000… Filters 0 500 1000 1500

500 1000 1500 2000 200 600 1000

1000 1500 2000 200 600 1000

1500 2000 200 600 1000

1000 800 nm 2000 200 600 1000 Optical Spectrometer

F. Albert et. al, Phys. Rev. Lett. 118, 134801 (2017)

36 F. Albert – HEDS seminar – May 9th 2019 We have demonstrated the production of radiation in the SMLWFA regime

70 Electron Interferometer 90 spectrometer

150

X-ray Energy Spectrum DiagnosticsMeV Ta Stepwedge filter

The x-ray filter wheel has Step Wedge sensitive to sensitivity up to ~50 [keV] energies 50 keV to 1 MeV

G. Williams et al, Rev. Sci. Instr. (2018)

37 F. Albert – HEDS seminar – May 9th 2019

28 LLNL-PRES-xxxxxx We have characterized these processes producing keV – MeV photons from SMLWFA electron beams

Laser Gas 1 Betatron x-ray radiation keV … Nozzle Filter wheel IP Stack Laser Low Z foil CH Gas 2 Compton scattering keV – MeV …

Nozzle Filter wheel IP Stack Stepwedge Laser High Z foil Gas W, Ta 3 Bremsstrahlung (LWFA) … MeV Nozzle IP Stack Stepwedge

These sources provide opportunities for new x-ray diagnostics development

38 F. Albert – HEDS seminar – May 9th 2019 P. M. King et. al, RSI 90, 033503 (2019) Electron and forward laser spectra confirm that we are in the SMLWFA regime Electron spectra Forward laser spectra

10.0 18 2 19 -3 I = 5x10 W/cm ne=0.85 x 10 cm λ 19 -3 1 5.0 ne=0.76 x 10 cm 19 -3 ne=1.45 x 10 cm MeV ê D 2.0 unit 1.0 ~ 7 nc λ2 arb .

@ 0.5

0.2

Counts 2�� 2�� 0.1 Detection threshold � = − � � 100 150 200 250 300 Electron Energy MeV

@ D F. Albert et. al, Phys. Rev. Lett. 118, 134801 (2017)

39 F. Albert – HEDS seminar – May 9th 2019 Particle-in-cell simulations performed with OSIRIS

· Massively Parallel, Fully Relativistic Particle-in-Cell (PIC) Code · Visualization and Data Analysis Infrastructure · Developed by the osiris.consortium ⇒ UCLA + IST

New Features in v2.0

· Bessel Beams · Binary Collision Module · Tunnel (ADK) and Impact Ionization Ricardo Fonseca: [email protected] · Dynamic Load Balancing Frank Tsung: [email protected] · PML absorbing BC http://exodus.physics.ucla.edu/http://cfp.ist.ut · Parallel I/O l.pt/golp/epp/

40 F. Albert – HEDS seminar – May 9th 2019 Energy (MeV) ρ[eωp2/c2] 2D PIC simulations of electron and forward laser spectrum also 7 confirm signatures of SMLWFA 0 75 150 225 300 x10 10-1 B E )|

2 10 136 A 10-2 136 D 10-3 8 |FFT(E c)] 102 10-4 Electron spectrum 102 Forward laser spectrum 2

6 8 10 12 14 Laser /( π

2 6 k(x1)[ωp/c] ω0 Energy (MeV) ( μ m) 2 2 7 ρ[eωp /c ] ( μ m) ω -ω ω0+ωplasma 2 68 0 plasma x10 2 68 0 75 150 225 300 x x 10 C 10-1 B 4 E )|

2 10 10-1 A 10-2 D 34 136 34 136W/d ω d Ω [e 2

-3 10-3 d 2 8 |FFT(E

10 c)] 2 0 #parts(a.u) 102 0 10-4 102

6 8 10 12 14 0 /( π 2860 3044 3219 3394 0 100 200 300 MeV 840 1680 2520 3360 0 20 40 60 120 2 6 k(x1)[ωp/c] 80 100 ( μ m)

x (μm) ( μ m) x ( m) 2 68 1 1 μ Energy (MeV) 2 68 Energy (keV) x 10 C x 4 10-1 34 34 W/d ω d Ω [e 2 F. Albert et. al,10 Phys.-3 Rev. Lett. 118, 134801 (2017) d 2 0 #parts(a.u) 0 41 0 F. Albert – HEDS2860 seminar – May 9th 2019 3044 3219 3394 0 100 200 300 840 1680 2520 3360 0 20 40 60 80 100 120 x1 (μm) Energy (MeV) x1 (μm) Energy (keV) Electrons accelerated in the SMLWFA regime produce betatron x-rays

D 0.15 6 4 7 3 0.10 2 8 9

Normalized 1 @ 10

0.05 11 Yield 13 12 2 4 6 8 10 12 Filter

42 F. Albert – HEDS seminar – May 9th 2019 week ending PRL 118, 134801 (2017) PHYSICAL REVIEW LETTERS 31 MARCH 2017

0.25 0.9 (a) 1010 (b) bremsstrahlung emission from the very underdense plasma. 0.8 Plate 0 9 2 0.20 0.7 10 Betatron The measured 1=e source diameter has an upper value Ec=10 keV

0.6 Sr Plate 108 of 35 μm. normalized 0.15 0.5 eV

Ratio 0.4 7 To quantify the x-ray spectrum at photon energies 1 2 3 4 5 6 7 10 Plate 0.10 Bremsstrahlung between 10 and 500 keV, we use the stacked image plate

Photons 6 Electrons accelerated10 T = 200 keVin the SMLWFA regimespectrometer. produce In addition to the betatron spectrum ray intensity 0.05 105 X betatron x-rays described by Eq. (1), we assume an additional high-energy 2 4 6 8 10 1 5 10 50 100 photon background so that the total number of photons per Filter number X ray Energy keV unit energy on axis is: 2 FIG. 3. (a) Normalized x-ray yield through filters of Fig. 1 (red dNx 1 E 2 dots) for a 3.05 and n 1019 cm−3 and critical energy fits ∝ K2=3 E=Ec A exp −E=ET ; 2 0 ¼ e ¼ dE E Ec ½ þ ½ ð Þ calculated0.50 with Eq. (1), with Ec 5 keV, 10 keV, and 15 keV ¼ (solid, dashed, and dotted lines). Inset: stacked image plate data where ET is the temperature of the exponentially decaying D Ec = 20 keV RE;i (red dots) and fit RT;i for a photon distribution [Eq. (2)] with bremsstrahlungD 0.15 spectrum and A its amplitude relative to Ec 10 unit keV,0.20 A 0.000 14, and T 200 keV. (b) Deduced the betatron spectrum. We propagate Eq. (2) through the betatron¼ and bremsstrahlung¼ spectra (see¼ text for details). different materials of the experiment and through the arb . @ 0.10 calibrated0.10 stacked image plate spectrometer [23,26]. of x rays through elements of the system (Al, Mylar The number RT;i PT;0=PT;i is calculated, where PT;0 is

X = Normalized windows)0.05 and the calibrated image plates’ absorption the@ total theoretical¼ yield in the first plate (plate C0 in Fig. 1) and efficiencyintensity [24]. For photon energies between 1 and and P the total theoretical yield in subsequent plates for 0.05T;i 30 keV,ray we utilize the filter wheel. Assuming that the Yield

- 0.02 i 1∶7. These values are compared to the experimental betatronX motion of the electrons dominates the observed ¼ results R P =P to minimize the residue R − x-ray emission in this range, we consider an intensity E;i ¼ E;0 E;i ið E;i R 2 by varying the parameters E and A. The betatron distribution per unit10 photon20 energy30 dE40 and50 solid angle d T;i 2 4 6 8 10 12T Ω criticalÞ photon energy is set at E 10 keV inP agreement as a function of theX- photonray energy energykeVE of the form: Filter c with the Ross pair filters measurements.¼ The best fit [inset of 2 2 Fig. 3(a) with the experimental data] is obtained for E d I E 2 T ∝ K@ 2=3 DE=Ec ; 1 200 keV and A 0.00014. The residue is higher by a factor¼ dEdΩ Ec ½ ð Þ of 10 if we fit¼ using only betatron or bremsstrahlung which is valid for betatron x rays on axis [25]. Here, Ec is distributions separately. We deduce that the total x-ray yield 43 the criticalF. Albert energy – HEDS seminar of – May the 9th 2019 betatron spectrum, and K2=3 is a observed in our experiment and shown in Fig. 3(b) is a modified Bessel function. The distribution function is combination of betatron radiation (dominant up to 40 keV) calculated through the different filters of the wheel and and bremsstrahlung (dominant above 40 keV). The brems- integrated to obtain the corresponding signal that it would strahlung, inevitable whenever relativistic electrons are yield on the image plate. The filters are sufficiently thin to produced, is likely due to lower energy (<500 keV) elec- neglect the effects of scattering for our range of energies. trons being strongly deflected by the magnet onto the walls Both the experimental and theoretical data are normalized of the target chamber. so that the sum of the signals of the filters is equal to 1. The To explain the observed betatron x-ray spectra, we data are analyzed through a least squares fitting method by performed 2D PIC simulations with OSIRIS for a variety minimizing the number D − T 2, where D and T of conditions [27]. We illustrate the salient observations ið i iÞ i i are, respectively, the measured and calculated normalized from one simulation that uses an a0 3, τ 0.7 ps, λ0 signals for each filter. OneP example is shown in Fig. 3(a) 1.053 μm laser pulse focused to a¼ spot size¼ of 15 μm¼ 19 3 2 for a0 3.05 and ne 10 cm− . Here, the best fit is (1=e intensity radius) into a 200 μm density up ramp. The obtained¼ for E 10 keV.¼ In our experimental conditions, pulse duration and a were chosen to match the exper- c ¼ 0 the highest critical energy Ec 20 keV was measured for imental values, and the spot size matches the value obtained 19¼ 3 2 a0 3.02 and ne 1.3 × 10 cm− . By differentiating the from the Gaussian fit (1=e intensity radius) of the signal¼ obtained in¼ the iron-chromium Ross pair (filters 6 measured spot. The pulse then propagates through a and 5, see image of Fig. 1), we can deduce the x-ray photon 3 mm-long fully ionized helium plasma of constant electron 19 −3 yield Nx at 6.5 0.5 keV. At constant electron density ne density ne 1 × 10 cm . The simulation utilizes a 19 −3Æ 8 ¼ ¼ 1.3×10 cm , it goes from Nx 3×10 photons=eVSr for moving window with box dimensions of 500 μm in the 9 ¼ a0 1.44 to Nx 1.45 10 photons=eV Sr for a0 3.02. longitudinal (laser propagation) direction and 150 μm in A sharp¼ stainless-steel¼ edge placed 22 cm from the¼ source the transverse direction. The corresponding resolutions are, casts a clear shadow on the first image plate detector, respectively, 60 and 7.2 cells per λ0. To calculate betatron indicating that for energies below 30 keV, the main source x-ray emission in these conditions, we select 750 random of x rays originates at the gas jet, consistent with betatron electrons in energy to match the overall spectrum emission. We do not expect any significant hard x-ray [Fig. 4(c)]. The simulation is run again while also tracking

134801-3 week ending PRL 118, 134801 (2017) PHYSICAL REVIEW LETTERS 31 MARCH 2017

0.25 0.9 (a) 1010 (b) bremsstrahlung emission from the very underdense plasma. 0.8 Plate 0 9 2 0.20 0.7 10 Betatron The measured 1=e source diameter has an upper value Ec=10 keV

0.6 Sr Plate 108 of 35 μm. normalized 0.15 0.5 eV

Ratio 0.4 7 To quantify the x-ray spectrum at photon energies 1 2 3 4 5 6 7 10 Plate 0.10 Bremsstrahlung between 10 and 500 keV, we use the stacked image plate

Photons 6 Electrons accelerated10 T = 200 keVin the SMLWFA regimespectrometer. produce In addition to the betatron spectrum ray intensity 0.05 105 X betatron x-rays described by Eq. (1), we assume an additional high-energy 2 4 6 8 10 1 5 10 50 100 photon background so that the total number of photons per Filter number X ray Energy keV unit energy on axis is: 2 FIG. 3. (a) Normalized x-ray yield through filters of Fig. 1 (red dNx 1 E 2 dots) for a 3.05 and n 1019 cm−3 and critical energy fits ∝ K2=3 E=Ec A exp −E=ET ; 2 0 ¼ e ¼ dE E Ec ½ þ ½ ð Þ calculated0.50 with Eq. (1), with Ec 5 keV, 10 keV, and 15 keV ¼ (solid, dashed, and dotted lines). Inset: stacked image plate data where ET is the temperature of the exponentially decaying D Ec = 10 keV RE;i (red dots) and fit RT;i for a photon distribution [Eq. (2)] with bremsstrahlungD 0.15 spectrum and A its amplitude relative to Ec 10 unit keV,0.20 A 0.000 14, and T 200 keV. (b) Deduced the betatron spectrum. We propagate Eq. (2) through the betatron¼ and bremsstrahlung¼ spectra (see¼ text for details). different materials of the experiment and through the arb . @ 0.10 calibrated0.10 stacked image plate spectrometer [23,26]. of x rays through elements of the system (Al, Mylar The number RT;i PT;0=PT;i is calculated, where PT;0 is

- 0.02 i 1∶7. These values are compared to the experimental betatronX motion of the electrons dominates the observed ¼ results R P =P to minimize the residue R − x-ray emission in this range, we consider an intensity E;i ¼ E;0 E;i ið E;i R 2 by varying the parameters E and A. The betatron distribution per unit10 photon20 energy30 dE40 and50 solid angle d T;i 2 4 6 8 10 12T Ω criticalÞ photon energy is set at E 10 keV inP agreement as a function of theX- photonray energy energykeVE of the form: Filter c with the Ross pair filters measurements.¼ The best fit [inset of 2 2 Fig. 3(a) with the experimental data] is obtained for E d I E 2 T ∝ K@ 2=3 DE=Ec ; 1 200 keV and A 0.00014. The residue is higher by a factor¼ dEdΩ Ec ½ ð Þ of 10 if we fit¼ using only betatron or bremsstrahlung which is valid for betatron x rays on axis [25]. Here, Ec is distributions separately. We deduce that the total x-ray yield 44 the criticalF. Albert energy – HEDS seminar of – May the 9th 2019 betatron spectrum, and K2=3 is a observed in our experiment and shown in Fig. 3(b) is a modified Bessel function. The distribution function is combination of betatron radiation (dominant up to 40 keV) calculated through the different filters of the wheel and and bremsstrahlung (dominant above 40 keV). The brems- integrated to obtain the corresponding signal that it would strahlung, inevitable whenever relativistic electrons are yield on the image plate. The filters are sufficiently thin to produced, is likely due to lower energy (<500 keV) elec- neglect the effects of scattering for our range of energies. trons being strongly deflected by the magnet onto the walls Both the experimental and theoretical data are normalized of the target chamber. so that the sum of the signals of the filters is equal to 1. The To explain the observed betatron x-ray spectra, we data are analyzed through a least squares fitting method by performed 2D PIC simulations with OSIRIS for a variety minimizing the number D − T 2, where D and T of conditions [27]. We illustrate the salient observations ið i iÞ i i are, respectively, the measured and calculated normalized from one simulation that uses an a0 3, τ 0.7 ps, λ0 signals for each filter. OneP example is shown in Fig. 3(a) 1.053 μm laser pulse focused to a¼ spot size¼ of 15 μm¼ 19 3 2 for a0 3.05 and ne 10 cm− . Here, the best fit is (1=e intensity radius) into a 200 μm density up ramp. The obtained¼ for E 10 keV.¼ In our experimental conditions, pulse duration and a were chosen to match the exper- c ¼ 0 the highest critical energy Ec 20 keV was measured for imental values, and the spot size matches the value obtained 19¼ 3 2 a0 3.02 and ne 1.3 × 10 cm− . By differentiating the from the Gaussian fit (1=e intensity radius) of the signal¼ obtained in¼ the iron-chromium Ross pair (filters 6 measured spot. The pulse then propagates through a and 5, see image of Fig. 1), we can deduce the x-ray photon 3 mm-long fully ionized helium plasma of constant electron 19 −3 yield Nx at 6.5 0.5 keV. At constant electron density ne density ne 1 × 10 cm . The simulation utilizes a 19 −3Æ 8 ¼ ¼ 1.3×10 cm , it goes from Nx 3×10 photons=eVSr for moving window with box dimensions of 500 μm in the 9 ¼ a0 1.44 to Nx 1.45 10 photons=eV Sr for a0 3.02. longitudinal (laser propagation) direction and 150 μm in A sharp¼ stainless-steel¼ edge placed 22 cm from the¼ source the transverse direction. The corresponding resolutions are, casts a clear shadow on the first image plate detector, respectively, 60 and 7.2 cells per λ0. To calculate betatron indicating that for energies below 30 keV, the main source x-ray emission in these conditions, we select 750 random of x rays originates at the gas jet, consistent with betatron electrons in energy to match the overall spectrum emission. We do not expect any significant hard x-ray [Fig. 4(c)]. The simulation is run again while also tracking

134801-3 week ending PRL 118, 134801 (2017) PHYSICAL REVIEW LETTERS 31 MARCH 2017

0.25 0.9 (a) 1010 (b) bremsstrahlung emission from the very underdense plasma. 0.8 Plate 0 9 2 0.20 0.7 10 Betatron The measured 1=e source diameter has an upper value Ec=10 keV

0.6 Sr Plate 108 of 35 μm. normalized 0.15 0.5 eV

Ratio 0.4 7 To quantify the x-ray spectrum at photon energies 1 2 3 4 5 6 7 10 Plate 0.10 Bremsstrahlung between 10 and 500 keV, we use the stacked image plate

Photons 6 Electrons accelerated10 T = 200 keVin the SMLWFA regimespectrometer. produce In addition to the betatron spectrum ray intensity 0.05 105 X betatron x-rays described by Eq. (1), we assume an additional high-energy 2 4 6 8 10 1 5 10 50 100 photon background so that the total number of photons per Filter number X ray Energy keV unit energy on axis is: 2 FIG. 3. (a) Normalized x-ray yield through filters of Fig. 1 (red dNx 1 E 2 dots) for a 3.05 and n 1019 cm−3 and critical energy fits ∝ K2=3 E=Ec A exp −E=ET ; 2 0 ¼ e ¼ dE E Ec ½ þ ½ ð Þ calculated0.50 with Eq. (1), with Ec 5 keV, 10 keV, and 15 keV ¼ (solid, dashed, and dotted lines). Inset: stacked image plate data where ET is the temperature of the exponentially decaying D Ec = 5 keV 0.20 RE;i (red dots) and fit RT;i for a photon distribution [Eq. (2)] with bremsstrahlungD spectrum and A its amplitude relative to Ec 10unit keV,0.20 A 0.000 14, and T 200 keV. (b) Deduced the betatron spectrum. We propagate Eq. (2) through the betatron¼ and bremsstrahlung¼ spectra (see¼ text for details). different0.15 materials of the experiment and through the arb . @ 0.10 calibrated stacked image plate spectrometer [23,26]. of x rays through elements of the system (Al, Mylar The number RT;i PT;0=PT;i is calculated, where PT;0 is X = Normalized 0.10 windows)0.05 and the calibrated image plates’ absorption the@ total theoretical¼ yield in the first plate (plate C0 in Fig. 1) and efficiencyintensity [24]. For photon energies between 1 and and PT;i the total theoretical yield in subsequent plates for

30 keV,ray we utilize the filter wheel. Assuming that the Yield 0.05 - 0.02 i 1∶7. These values are compared to the experimental betatronX motion of the electrons dominates the observed ¼ results R P =P to minimize the residue R − x-ray emission in this range, we consider an intensity E;i ¼ E;0 E;i ið E;i R 2 by varying the parameters E and A. The betatron distribution per unit10 photon20 energy30 dE40 and50 solid angle d T;i 2 4 6 8 10 12T Ω criticalÞ photon energy is set at E 10 keV inP agreement as a function of theX- photonray energy energykeVE of the form: Filter c with the Ross pair filters measurements.¼ The best fit [inset of 2 2 Fig. 3(a) with the experimental data] is obtained for E d I E 2 T ∝ K@ 2=3 DE=Ec ; 1 200 keV and A 0.00014. The residue is higher by a factor¼ dEdΩ Ec ½ ð Þ of 10 if we fit¼ using only betatron or bremsstrahlung which is valid for betatron x rays on axis [25]. Here, Ec is distributions separately. We deduce that the total x-ray yield 45 the criticalF. Albert energy – HEDS seminar of – May the 9th 2019 betatron spectrum, and K2=3 is a observed in our experiment and shown in Fig. 3(b) is a modified Bessel function. The distribution function is combination of betatron radiation (dominant up to 40 keV) calculated through the different filters of the wheel and and bremsstrahlung (dominant above 40 keV). The brems- integrated to obtain the corresponding signal that it would strahlung, inevitable whenever relativistic electrons are yield on the image plate. The filters are sufficiently thin to produced, is likely due to lower energy (<500 keV) elec- neglect the effects of scattering for our range of energies. trons being strongly deflected by the magnet onto the walls Both the experimental and theoretical data are normalized of the target chamber. so that the sum of the signals of the filters is equal to 1. The To explain the observed betatron x-ray spectra, we data are analyzed through a least squares fitting method by performed 2D PIC simulations with OSIRIS for a variety minimizing the number D − T 2, where D and T of conditions [27]. We illustrate the salient observations ið i iÞ i i are, respectively, the measured and calculated normalized from one simulation that uses an a0 3, τ 0.7 ps, λ0 signals for each filter. OneP example is shown in Fig. 3(a) 1.053 μm laser pulse focused to a¼ spot size¼ of 15 μm¼ 19 3 2 for a0 3.05 and ne 10 cm− . Here, the best fit is (1=e intensity radius) into a 200 μm density up ramp. The obtained¼ for E 10 keV.¼ In our experimental conditions, pulse duration and a were chosen to match the exper- c ¼ 0 the highest critical energy Ec 20 keV was measured for imental values, and the spot size matches the value obtained 19¼ 3 2 a0 3.02 and ne 1.3 × 10 cm− . By differentiating the from the Gaussian fit (1=e intensity radius) of the signal¼ obtained in¼ the iron-chromium Ross pair (filters 6 measured spot. The pulse then propagates through a and 5, see image of Fig. 1), we can deduce the x-ray photon 3 mm-long fully ionized helium plasma of constant electron 19 −3 yield Nx at 6.5 0.5 keV. At constant electron density ne density ne 1 × 10 cm . The simulation utilizes a 19 −3Æ 8 ¼ ¼ 1.3×10 cm , it goes from Nx 3×10 photons=eVSr for moving window with box dimensions of 500 μm in the 9 ¼ a0 1.44 to Nx 1.45 10 photons=eV Sr for a0 3.02. longitudinal (laser propagation) direction and 150 μm in A sharp¼ stainless-steel¼ edge placed 22 cm from the¼ source the transverse direction. The corresponding resolutions are, casts a clear shadow on the first image plate detector, respectively, 60 and 7.2 cells per λ0. To calculate betatron indicating that for energies below 30 keV, the main source x-ray emission in these conditions, we select 750 random of x rays originates at the gas jet, consistent with betatron electrons in energy to match the overall spectrum emission. We do not expect any significant hard x-ray [Fig. 4(c)]. The simulation is run again while also tracking

134801-3 Electrons accelerated in the SMLWFA regime produce betatron x-rays

0.50

D Ec = 10 keV 0.20 D

unit 0.20 0.15 arb . @ 0.10

X = Normalized 0.10

0.05 @ intensity ray

Yield 0.05 - 0.02 X

10 20 30 40 50 2 4 6 8 10 12 X-ray energy keV Filter

@ D 9 Best fit for Ec = 10 keV +/- 2 keV (least squares fit) – 10 photons/eV/Sr

46 F. Albert – HEDS seminar – May 9th 2019 Electrons accelerated in the SMLWFA regime produce betatron x-rays with critical energies of 10-40 keV

Measured/calculated x-ray spectrum Betatron - Experiment

Ec = 40 keV

Ec = 10 keV

Noise level

F. Albert et. al, Phys. Rev. Lett. 118, 134801 (2017)

47 F. Albert – HEDS seminar – May 9th 2019 Electrons accelerated in the SMLWFA regime produce betatron x-rays with critical energies of 10-40 keV

Measured/calculated x-ray spectrum Betatron - Experiment PIC simulation Ec = 40 keV

Ec = 10 keV

Noise level

F. Albert et. al, Phys. Rev. Lett. 118, 134801 (2017)

48 F. Albert – HEDS seminar – May 9th 2019 Optimized betatron radiation produces the most photons for energies <40 keV

Betatron, Ec = 10 keV

Laser Gas

Nozzle

19 -3 ne = 1.5 x 10 cm Elaser = 150 J a0 ~ 3

49 F. Albert – HEDS seminar – May 9th 2019 F. Albert et. al, Phys. Rev. Lett. 118, 134801 (2017) Compton scattering allows for increased photon flux up to a few 100 keV

Compton scattering Ross pairs � � � � ∝ �� − + �� − �� T1 = 36 keV (Filter wheel)

Laser Foil Gas CH, 100 µm

Nozzle

18 -3 ne = 4 x 10 cm Elaser = 120 J a0 ~ 3

N. Lemos et. al Phys. Rev. Lett. (in review)

50 F. Albert – HEDS seminar – May 9th 2019 Compton scattering allows for increased photon flux up to a few 100 keV

Compton scattering � � � � ∝ �� − + �� − �� T2 = 78 keV (Step wedge)

Step wedge Laser Foil Gas CH, 100 µm

Nozzle

18 -3 ne = 4 x 10 cm Elaser = 120 J a0 ~ 3

N. Lemos et. al Phys. Rev. Lett. (in review)

51 F. Albert – HEDS seminar – May 9th 2019 A multi-temperature Compton scattering distribution is consistent with predictions from measured electron beam energy

Electron beam spectrum Compton scattering spectrum 10.0 5.0 MeV ê D 2.0 /shot unit 1.0 1011 photons/shot arb .

@ 0.5

0.2 keV Photons/ Counts 0.1 Detection threshold 100 150 200 250 300 Electron Energy MeV Photon Energy [keV]

� ∝ 4� � @ D N. Lemos et. al Phys. Rev. Lett. (in review)

52 F. Albert – HEDS seminar – May 9th 2019 LWFA-driven bremsstrahlung produces the most photons at MeV energies

LWFA-driven bremsstrahlung Step wedge �(�) ∝ ��[−�/�] T = 838 keV (Stepwedge)

Laser Foil Gas W, 0.5 mm

Nozzle 1.5 cm

N. Lemos et. al, PPCF, 60, 054008 (2018) N. Lemos et. al, PRL (in review) P. M. King et. al, RSI 90, 033503 (2019)

53 F. Albert – HEDS seminar – May 9th 2019 The combined target can be varied to control the photon flux and temperature of the emitted x-rays

Laser Foil CH, 100 µm Gas Compton

Nozzle

54 F. Albert – HEDS seminar – May 9th 2019 P. M. King et. al, In preparation (2019) The combined target can be varied to control the photon flux and temperature of the emitted x-rays

Laser Foil Gas CH, 100 µm Compton + Brem

Nozzle Laser Foil CH, 100 µm Gas W 50 µm

Nozzle

55 F. Albert – HEDS seminar – May 9th 2019 P. M. King et. al, In preparation (2019) The combined target can be varied to control the photon flux and temperature of the emitted x-rays

Laser Foil Gas CH, 100 µm Compton + Brem

Nozzle Laser Foil CH, 100 µm Gas W 50 µm

Nozzle Laser Foil CH, 100 µm Gas W 250 µm

Nozzle

56 F. Albert – HEDS seminar – May 9th 2019 P. M. King et. al, In preparation (2019) We can radiograph typical NIF targets with this source

57 F. Albert – HEDS seminar – May 9th 2019 P. M. King et. al, In preparation (2019) We can radiograph typical NIF targets with this source

58 F. Albert – HEDS seminar – May 9th 2019 P. M. King et. al, In preparation (2019) We can radiograph typical NIF targets with this source

Laser Foil Gas CH, 100 µm

Nozzle

59 F. Albert – HEDS seminar – May 9th 2019 P. M. King et. al, In preparation (2019) We can tune the source to provide the radiograph with the best contrast and resolution

Laser Foil Gas CH, 100 µm

Nozzle Laser Foil CH, 100 µm Gas W 50 µm

Nozzle

60 F. Albert – HEDS seminar – May 9th 2019 P. M. King et. al, In preparation (2019) We can tune the source to provide the radiograph with the best contrast and resolution

Laser Foil Gas CH, 100 µm

Nozzle Laser Foil CH, 100 µm Gas W 50 µm

Nozzle Laser Foil CH, 100 µm Gas W 250 µm

Nozzle

61 F. Albert – HEDS seminar – May 9th 2019 P. M. King et. al, In preparation (2019) First Results at the OMEGA-EPAll laser shots show yielded similar 100+ MeV electron electron beamsbeam with divergences ~ 150 mrad or less properties in SMLWFA conditions Configuration for LWFA

a =3 0 Laser Parameters 18 -3 ne =5x10 cm • Appodizing Beams • f/8, f/10 on 2/BL Electron spectrum • f/6 on 1/SL TCC’ • Alternate SL, BL Beam Propagation E- spectrometer • Scan energy • All shots BC

Gas Jet • 100% He • Vary P , Φ 12 He nozzle

/MeV 10 sr

10 10 5 Analysis Needed: 1) Refine energy measurements 2) Divergence measurements Electrons/ 20 40 60 80 100 120 140 160 180 200 3) Charge analysis MeV MeV 10

2:1 SNR 160 mrad

160 mrad

62 F. Albert – HEDS seminar – May 9th 2019 We have DS shots at NIF (9/11/2019) to develop the SMLWFA platform

NEPPS 90-015 90-015 C-Tarpos Cryo-Tarpos W-NEPPS

TCC (gas target)

ARC beamlet ARC AT 90-348 TanDM e--beam 77-204 ARC

Target ARC Parameters 90-239 1 beamlet Tarpos Shortest pulse duration: 1 ps Energy: Maximum (>250 J) Intensity: 0.5 – 1 x 1018 W/cm

63 F. Albert – HEDS seminar – May 9th 2019 We will use gas tubes and a modified version of NEPPS to produce and characterize electrons up to 150 MeV

4 mm gas tube Q32T Oriented along ARC B354A

ARC B354A

Q14B

Electrons X-rays

64 F. Albert – HEDS seminar – May 9th 2019 Outline

65 F. Albert – HEDS seminar – May 9th 2019 We performed experiments at LCLS MEC end station

§ Colocation of three laser systems — XFEL (8 keV, 70 fs, 3 mJ) — ns optical laser (20 J, ns) — fs optical laser (1-7 J, 40 fs)

§ Type of experiments — ns laser pump / Betatron x-ray probe — fs laser pump / Betatron x-ray and LCLS probe — LCLS pump / Betatron x-ray probe

66 F. Albert – HEDS seminar – May 9th 2019 Betatron x-ray experiment at LCLS-MEC

cτ

1/2 lp=c/ωp~ 1/ne Blowout regime

67 F. Albert – HEDS seminar – May 9th 2019 Characterization of electron beam and betatron beam profile

70 Electron 90 spectrometer

150 MeV MEC short pulse X-ray CCD/IP 1J, 45 fs OAP

→ B Filters

Electrons X-rays (IP) X-rays (CCD + Filters)

1200 1000 800 dE 600 dN ê 400 200 50 100 150 200 Beam profile 30 mrad Electron Energy MeV 40 mrad fwhm

@ D 1010 5050 100100 200200 ElectronElectron energy Energy (MeV)[MeV]

68 F. Albert – HEDS seminar – May 9th 2019 Electron beams and betatron x-rays are produced every shot

Electrons Betatron x-rays Dispersed on LANEX screen > 4 keV on PI-MTE CCD 19 -3 ne = 10 cm 3 x 12.5 µm Al filters 90 % He, 10 % N2 mix 60 µm Ag wires grid

Energy (MeV) 50 100 200

30 mrad

69 F. Albert – HEDS seminar – May 9th 2019 Characterization of betatron x-ray focus shows 16 % rms intensity stability 70 Electron

90 spectrometer X-ray CCD 150 Al 25 µm MeV

→ B Ellipsoidal mirror

X-ray focus scan Ray tracing betatron focus

Courtesy P. Heimann

30 µm

14 mrad tangential slope error 100 mrad sagittal slope error -100 -50 0 50 100 µm

70 F. Albert – HEDS seminar – May 9th 2019 Betatron x-ray spectrum characterized with grating spectrometer

70 Electron 90 spectrometer 100 µm

150

MeV

Ellipsoidal mirror X-ray CCD

→ B

Reference spectra registered during the delay scan Spectrometer Reference 30 shots 9 % rms intensity=> high stability stability

4 2.52.5 10 4 Intensity stability ~ 9 % rms 22 1044 shot

1.5 1044 vert 30 vert 1.5 10 pix

/30 11 1044 counts #521 #562 3 55 103 #522 #566 CCD signal (int. 30 pix vert. & shots)

CCD #525 #570 #553 #573/4 #556 #577 650 450 #559 #581 0 450 500500 550550 600 650

Energy (eV) X-ray energyEnergy(eV) (eV)

71 F. Albert – HEDS seminar – May 9th 2019 We have probed nonthermal melting in SiO2 using x-ray absorption spectroscopy

energy non-equilibrium non-equilibrium thermalized deposition structure A structure B structure B

short pulse (fs)

Non thermal Thermalization transition

0 10-100fs 10-100ps time

72 F. Albert – HEDS seminar – May 9th 2019 We performed absorption spectroscopy of SiO2 a the O K-edge (535 eV)

SiO2 300 K 1 O K-edge

Conduction 0.8 band

9 eV 0.6

Valence band 0.4 Absorbance

O 2s 0.2 Si 2p Si 2s 0 O 1s 535 eV 510 520 530 540 550 560 Photon Energy eV Si 1s 1848.6 eV

@ D

73 F. Albert – HEDS seminar – May 9th 2019 No absorption of x-ray probe photons below O K-edge energy

SiO2 300 K 1 O K-edge

Conduction 0.8 band Betatron photon 9 eV 0.6 <535 eV

Valence band 0.4 Absorbance

O 2s 0.2 Si 2p Si 2s 0 O 1s 535 eV 510 520 530 540 550 560 Photon Energy eV Si 1s 1848.6 eV

@ D

74 F. Albert – HEDS seminar – May 9th 2019 Sharp transition corresponds to strong absorption of x-ray photons for energies above the O K-edge

SiO2 300 K 1 O K-edge

Conduction 0.8 band Betatron photon 9 eV 0.6 >535 eV

Valence band 0.4 Absorbance

O 2s 0.2 Si 2p Si 2s 0 O 1s 535 eV 510 520 530 540 550 560 Photon Energy eV Si 1s 1848.6 eV

@ D

75 F. Albert – HEDS seminar – May 9th 2019 Multiphoton absorption causes electrons to cross the bandgap and leave vacancies in the valence band

Heating Optical laser SiO2 10,000 K 1015 W/cm2 Conduction band

9 eV

Valence band

O 2s Si 2p Si 2s

O 1s 535 eV

Si 1s 1848.6 eV

76 F. Albert – HEDS seminar – May 9th 2019 1s-valence band transitions are now authorized: strong absorption peak 9 eV below the edge

Heating Optical laser SiO2 10,000 K 1 O K-edge 1015 W/cm2 Conduction 0.8 band Betatron photon 9 eV 0.6 9 eV

Valence band 0.4 Absorbance

O 2s 0.2 Si 2p Si 2s 0 O 1s 535 eV 510 520 530 540 550 560 Photon Energy eV Si 1s 1848.6 eV

@ D

77 F. Albert – HEDS seminar – May 9th 2019 Defect states also allow absorption within bandgap upon heating, K-edge is broadened and red shifted

Heating Optical laser SiO2 10,000 K 1 O K-edge 1015 W/cm2 Cold Conduction 0.8 Warm band Betatron photon <9 eV 0.6

Valence band 0.4 Absorbance

O 2s 0.2 Si 2p Si 2s 0 O 1s 535 eV 510 520 530 540 550 560 Photon Energy eV Si 1s 1848.6 eV

@ D

78 F. Albert – HEDS seminar – May 9th 2019 Defect states also allow absorption within bandgap upon heating, K-edge is broadened and red shifted

Heating Optical laser SiO2 10,000 K 1 O K-edge 1015 W/cm2 Cold Conduction 0.8 Warm band Betatron photon <9 eV 0.6

Valence band 0.4 Absorbance

O 2s 0.2 Si 2p Si 2s 0 O 1s 535 eV 510 520 530 540 550 560 Photon Energy eV Si 1s 1848.6 eV

@ D

79 F. Albert – HEDS seminar – May 9th 2019 We have demonstrated the use of betatron x-rays as a tool for absorption spectroscopy

70 Electron 90 spectrometer 100 µm 450 700 150 Energy (eV) MeV

Ellipsoidal mirror Cold XANES spectra registered during the delay200 scan [smoothnm SiO 7 eV]2 X-ray CCD (normalized over [550-575 eV]) 1.6 → 1.6 AmorphousMean am-SiO2 (11 spectra SiO = 330 330shots) shots B Mean cr-SiO2 (2 spectra = 60 shots)2 Crystalline SiO2 60 shots 1.2 1.2 These averages will be resp. used to estimate the pre-edge integral 0.80.8 Absorbance

0.4

Cold absorption spectra Absorbance 0.4

Not the same slope for cr-SiO2 0 (higher density ?) 0 (substrate ?) 450450 500500 550550 600600 650650 X-ray energyEnergy (eV) (eV)

80 F. Albert – HEDS seminar – May 9th 2019 We have demonstrated the use of betatron x-rays as a tool for absorption spectroscopy

70 Electron 90 spectrometer 100 µm 450 700 150 Pump Energy (eV) MeV 1015 W/cm2

Ellipsoidal mirror Cold / Hot XANES spectra average over all the delay200 scan nm [smooth SiO 27 eV] (normalized over [550-575 eV]) X-ray CCD am-SiO2 sample only 1.6 → 1.6 Mean cold 330 shots B MeanMean hot 330 cold shots SiO2 330 shots IntegrationMean range hot SiO 330 shots 1.2 of each hot - cold avg 2 1.2 = [500 - 545] eV

0.8 0.8 Alternatively = [500 - 535] eV Absorbance Cold/warm absorption spectra 0.40.4 Absorbance

00 Pre-edge

450 500500 550550 600600 650650 X-ray energyEnergy (eV) (eV)

81 F. Albert – HEDS seminar – May 9th 2019 We have demonstrated the use of betatron x-rays as a tool for absorption spectroscopy with sub ps resolution

70 3. Time-resolvedElectron XANES (4/5)! 90 spectrometer 100 µm 450 700 • Pre-edge level extracted150 from integration of “hot” – “cold” averaged" Pump Energy (eV) – Pre-edge time evolution versusMeV delay gives an upper limit for temporal resolution 1015 W/cm2 " ! Just considering date on am-SiO2 … but the run #568 seems to be aberrant" Without it, the best ﬁt gives a temporal resolution = 0.48 ± 0.13 ps rms" ! Ellipsoidal mirror 200 nm SiO2 X-ray CCD Delay scan on am-SiO2 sample Delay scan on am-SiO2 sample XANES spectra normalized XANES spectra normalized then substracted to avg cold then substracted to avg cold → and integrated over ≠ spectral range and integrated over ≠ spectral range 10 B 10 Cold over [500-545] eV y = 6*(0.5+0.5*erf((m0-m1)/m... Cold Integr. [500-545eV] (eV)y = 6*(0.5+0.5*erf((m0-m1)/m... Cold over [500-535] eV Value Error Cold Integr. [500-535eV] (eV) Value Error Hot over [500-545] eV Hot Integr. [500-545eV] (eV) Hot over [500-535] eV m1 -0.0030769 0.21992 Hot Integr. [500-535eV] (eV) m1 -0.017005 0.09553 8 m2 0.96311 0.40353 8 m2 0.68532 0.17909 Chisq 13.571 NA Chisq 2.9108 NA R 0.8086 NA R 0.95702 NA

6 6

4 4 Erf fit gives : Without #568, erf fit gives : - "t0" = 0.0 ± 0.2 ps - "t0" = 0.0 ± 0.1 ps 0.48 +/run- #5680.18 (good ps sync.)rms rise time (good sync.) 2 - temp. res. = 0.96 ± 0.40 ps 2 - temp. res. = 0.68 ± 0.18 ps Integrated 500 – 545 eV (0.67 ± 0.28 ps rms) (0.48 ± 0.13 ps rms) (1.60 ± 0.66 ps FWHM) (1.13 ± 0.30 ps FWHM) Integrated 500 – 535 eV average cold (eV) Integrated spectra hot - avg cold (eV) 0 Integrated spectra hot - avg cold (eV) 0

Error estimated from cold data : 0 2 4 6 8 10 12

0.8 rms over [500-545] – 0.6 rms over [500-535]

=> reported on error bars spectra Integrated -2 -2 -2 0 2 4 6 8 10 12 -2 0 2 4 6 8 10 12 hot hot -2 0 2 4 6 8 10 12 Delay (ps) Delay (ps) Delay (ps)

82 F. Albert – HEDS seminar – May 9th 2019 Other applications in progress

Phase contrast imaging of laser-driven shocks Relaxation of metals driven by XFEL x-rays Sample ns laser X-FEL

Betatron Sample Betatron very preliminary analysis of shockCamera data Spectrometer LCLS e- Unshocked Shocked e- hv

1 ns 13 J K L M K-Shell Radiative Auger decay photoionization decay (KLL) CourtesyRAL 2014 of S. Mangles and J. Woods, [email protected] College

83 F. Albert – HEDS seminar – May 9th 2019 Conclusions and future work § We have demonstrated the production of novel x- ray sources from laser-plasma accelerators

§ They are broadband (keV - MeV), ultrafast (fs - X-ray sources – Picosecond phenomena ps), collimated (mrad), synchronized with drive laser

13 10 § They enable new applications Sandia Z – 3 ns Line emission Ê — Study of ultrafast non-thermal melting in NIF – 1 ns SiO2 11 10 Ê — Phase contrast imaging of laser-driven shocks — Study of opacity in HED matter Ê ps

ê § Future work and challenges 109 Sr

ê Betatron radiation — Improving sources stability and flux

eV ps LWFA — Applications from proof-of-principle to ê Broadband practical 107 emission — LWFA sources as probes for HED science OMEGA – 100 ps Photons experiments

N. Lemos et al, PPCF 58 034108 (2016) 5 10 Bremsstrahlung F. Albert et al, PRL 118 134801 (2017) Titan – 10 ps F. Albert et al, POP 25 056706 (2018) N. Lemos et al, PPCF 60, 054008 (2018) P. King et. al, Rev. Sc. Instr. 90, 033503 (2019) 1 2 5 10 20 50 100 F. Albert et al, Nuclear Fusion, 59, 032003 (2019) Photon energy keV N. Lemos et. al, PRL (in review)

@ D 84 F. Albert – HEDS seminar – May 9th 2019 It is an exciting time for short pulse laser science – LaserNetUS established in August 2018

https://www.lasernetus.org

85 F. Albert – HEDS seminar – May 9th 2019