Laser-plasma interactions

Transkript

1 Mitglied der Helmholtz-Gemeinschaft Autumn Lectures / Tbilisi / 2013 Laser-plasma interactions 22 October 2013 Markus Büscher

2 Conventional (RF) accelerators 22 October 2013 Markus Büscher 2

3 Need for novel approaches Ú Accelerating fields ~ 1 MV/m Electron Energy (MeV) 22 October 2013 Markus Büscher 3

4 Need for novel approaches Ú Accelerating fields ~ 1 MV/m Electron Energy (MeV) Laser-induced particle acceleration ~ 100 GV/m 22 October 2013 Markus Büscher 4

5 Development of laser intensities Focussed intensity (W/cm²) Characteristic electron energy 22 October 2013 Markus Büscher 5

6 High intensities 1367 W/ m² 1020 W/ cm² 22 October 2013 Markus Büscher 6

7 Extreme conditions In the core of the sun, the energy density is about J/cm 3 The energy density produced by a pulse of 500 J and 1 ps in duration, focused into a 5 µm focal spot, is about J/cm 3 The light pressure is in the order of Gigabar (10 9 atm) This is the basis for the enormous application potential of powerful lasers 22 October 2013 Markus Büscher 7

8 Laser: basic properties LASER = Light Amplification by Stimulated Emission of Radiation Laser beam Energy Well defined color (wavelength) Emission in narrow cone Coherent oscillations Very high intensities available 22 October 2013 Markus Büscher 8

9 Laser: basic properties LASER Laser beam Focus (Ø typically 10 µm) Energy Lens Intensity = Power Area 22 October 2013 Markus Büscher 9

10 Laser: basic properties LASER Laser pulse Focus Energy Power = Energy Time Nowadays peak powers up to Petawatt = Watt are available (e.g. 1 Joule in 1 fs) 22 October 2013 Markus Büscher 10

11 Chirped pulse amplification (CPA) stretcher compressor 22 October 2013 Markus Büscher 11

12 CPA: Ti:Sa crystals Emission and absorption spectrum 22 October 2013 Markus Büscher 12

13 CPA: Pulse shape Measured at ARCturus / Düsseldorf Univ. I W/cm² 22 October 2013 Markus Büscher 13

14 DARCTURUS Institute für Laser- und Plasmaphysik, Univ. Düsseldorf (Prof. O.Willi) PULSAR Ti:Sapphire Laser: 100 TW, 800 nm ~ 2,5 Joule, less than 25 femtoseconds focused on 10 microns 22 October 2013 Markus Büscher 14

15 Particle acceleration: typical setup I ultra-short high-intense laser pulse ~ W/cm 2 * target gas jets underdense plasma particles electrons up to ~100 MeV* solid targets overdense plasma protons / ions up to ~10 MeV* Video from: * typical values at HHUD 22 October 2013 Markus Büscher 15

16 Response of electrons to plane waves Lab system mooving system E field electron trajectory B field Electron is at rest again when laser pulse is gone! 22 October 2013 Markus Büscher 16

17 Response to finite wave packet Intensity gradient Response to focused light pulse plane wave Ponderomotive force 22 October 2013 Markus Büscher 17

18 Ponderomotive force Force that a charged particle experiences in an inhomogeneous oscillating electromagnetic field F = p e2 4m e ω 2 E 0 2 U p [ev] = I[W/cm 2 ] λ[µm] 22 October 2013 Markus Büscher 18

19 Acceleration mechanisms 1) Radiation pressure ( direct, thin foil targets) 2) Wake fields / bubbles (gas targets) 3) Target Normal Sheath Acceleration (foil & pellet targets) 4) Break-Out Afterburner (thin foil targets) 5) 22 October 2013 Markus Büscher 19

20 Radiation Pressure Acceleration (RPA) Strong electro-magnetic fields *) in the laser pulse accelerate charged particles *) Typical values: E = V/m, B ~ 10 5 I = W/cm² 22 October 2013 Markus Büscher 20

21 Radiation Pressure Acceleration (RPA) I 0 = W/cm 2, n 0 = cm -3 (100n c ), r 0 = 10 µm electrons E field of laser ions simulation: P.Gibbon, FZ Jülich see also (for lower laser intensities): B. Qiao et al., Phys. Rev. Lett. 105, (2010) 22 October 2013 Markus Büscher 21

22 Laser-plasma interaction Some electrons are pushed out Some electrons oscillate ( wake fields ) 22 October 2013 Markus Büscher 22

23 Wake fields in plasmas wake field oscillating electrons laser pulse plasma 22 October 2013 Markus Büscher 23

24 Plasma oscillation Rapid oscillations of the electron density in conducting media such as plasmas or metals Frequency only depends weakly on the wavelength ω p = n ee 2 ε 0 m e f p [Hz] 8980 n e [cm 3 ] n e = electron density e = electron charge m e = electron mass ε 0 = permittivity of vacuum 22 October 2013 Markus Büscher 24

25 Critical plasma density n [cm -3 ] / ( λ [µm]) 2 cr Laser n e n cr wave speed = speed of light plasma transparent, under-dense plasma gas targets N e n cr plasma electrons short-circuit Laser E-field wave is damped & reflected, over-dense plasma solid (foil) targets 22 October 2013 Markus Büscher 25

26 Wake fields: low laser intensity Electron density perturbation & longitudinal wake field V.Malka et al., Nature Physics 4, (2008) 22 October 2013 Markus Büscher 26

27 Wake fields: high laser intensity Electron density perturbation & longitudinal wake field 22 October 2013 Markus Büscher 27

28 Wake fields: bubble regime A.Pukhov & J.Meyer-ter-Vehn, Appl. Phys. B 74, (2002) surfing behind a wake boat M. Geissler et al., New J. of Phys. 8, 186, (2006) 22 October 2013 Markus Büscher 28

29 Bubble acceleration (gas targets) simulation: P.Gibbon, FZ Jülich accelerates electrons 22 October 2013 Markus Büscher 29

30 Observation of plasma channel J.Hein, R.Sauerbrey, Generation of ultrahigh light intensities and relativistic laser-matter interaction, in Springer Handbook of Lasers and Optics (2007), ISBN October 2013 Markus Büscher 30

31 Plasma observation: shadow images Shadow image Laser 60 TW, 7.8 bar He Images reveal plasma development and rapid filamentation Time resolution: few 10 fs (!) Electron density Height above nozzle 100 µm Spatial coordinate parallel to laser direction 22 October 2013 Markus Büscher 31

32 Plasma observation: interferometry Electron density 22 October 2013 Markus Büscher 32

33 Target Normal Sheath Acceleration (TNSA) Target foil ~ 100 GV/m 22 October 2013 Markus Büscher 33

34 TNSA: foil targets simulation: P.Gibbon, JSC, FZ Jülich accelerates protons/ions 22 October 2013 Markus Büscher 34

35 TNSA: mass limited targets Proton rich dot 20x20x0.5 µm ~ 100 GV/m H. Schwörer et al., Nature 439, 445 (2006) 22 October 2013 Markus Büscher 35

36 TNSA: Hydrogen pellet targets 2-D Simulations from the JSC Jülich Laser pulse with λ=1 µm and fokus Ø =10 µm hits a 10 µm frozen H 2 pellet COSY injection energy maximum proton energy can further be increased (factor 4) by optimization of the focus size 22 October 2013 Markus Büscher 36

37 Break-Out Afterburner (BOA) a) Target Normal Sheath Acceleration (TNSA) phase b) Intermediate phase c) Laser Breakout Afterburner (BOA) phase (plasma becomes underdense) 22 October 2013 Markus Büscher 37

38 TNSA vs. BOA 22 October 2013 Markus Büscher 38

39 RF vs. laser acceleration RF cavity Plasma "cavity" 1 m 1 MV/m 100 µm 100 GV/m } 1 MeV } 10 MeV 22 October 2013 Markus Büscher 39

40 An up-and-coming technology October 2013 Markus Büscher 40

41 Technological revolutions do happen! Has a conventional electron accelerator Has plasma technology 60% larger diagonal, 3 times lower weight, 15 times thinner, 3-4 times cheaper, 1 extra dimension, Oct 2002: largest CRT display, 102cm diagonal, $15,000, 63cm deep, 92kg Oct 2010: plasma display, 159cm diagonal, $4,000, 3.6cm deep, 33kg 22 October 2013 Markus Büscher 41

42 Helmholtz Association HGF List Helgoland SCHLESWIG- HOLSTEIN Research Centers: 18 Bremerhaven BREMEN Greifswald HAMBURG MECKLENBURG-VORPOMMERN Geesthacht Total staff: ~ NORDRHEIN-WESTFALEN NIEDERSACHSEN Braunschweig Wolfenbüttel- Remlingen Göttingen Magdeburg Sachsen-Anhalt Potsdam Niemegk BERLIN 2 4 Zeuthen Teltow BRANDENBURG Total budget ~ 3.4 billion Halle S. Jülich Bonn Köln RHEINLAND-PFALZ SAARLAND Sankt Augustin Darmstadt Heidelberg HESSEN Karlsruhe Stuttgart BADEN-WÜRTTEMBERG Lampoldshausen THÜRINGEN Bad Lauchstädt BAYERN Neuherberg Garching München Oberpfaffenhofen Leipzig SACHSEN * Stammsitz* Zweig- bzw. Außenstelle* mit Anzahl der Einrichtungen in einer Gemeinde Research Fields: Energy Earth and Environment Health Key Technologies Structure of Matter Aeronautics, Space and Transport 22 October 2013 Markus Büscher 42

43 Big lasers in the HGF: e.g. DESY Hamburg List Helgoland Bremerhaven BREMEN SCHLESWIG- HOLSTEIN Greifswald HAMBURG MECKLENBURG-VORPOMMERN Geesthacht Sept. 2010: Laser/plasma group established Jülich NORDRHEIN-WESTFALEN Bonn Köln Sankt Augustin NIEDERSACHSEN HESSEN Braunschweig Wolfenbüttel- Remlingen Göttingen THÜRINGEN Magdeburg Sachsen-Anhalt Halle S. Bad Lauchstädt Potsdam Niemegk Leipzig BERLIN 2 4 Zeuthen Teltow BRANDENBURG SACHSEN RHEINLAND-PFALZ SAARLAND Darmstadt Stammsitz* Zweig- bzw. Außenstelle* Heidelberg Lampoldshausen Karlsruhe Stuttgart BAYERN * mit Anzahl der Einrichtungen in einer Gemeinde J. Osterhoff, Talk at 470 W.-E. Heraeus-Seminar, 12/2010 BADEN-WÜRTTEMBERG Neuherberg Garching München Oberpfaffenhofen Ú Plasma-based particle accelerators 22 October 2013 Markus Büscher 43

44 Big lasers in the HGF: e.g. GSI Darmstadt List Jülich Bonn Köln Sankt Augustin Helgoland NORDRHEIN-WESTFALEN Bremerhaven BREMEN NIEDERSACHSEN HESSEN SCHLESWIG- HOLSTEIN Greifswald HAMBURG MECKLENBURG-VORPOMMERN Geesthacht Braunschweig Wolfenbüttel- Remlingen Göttingen THÜRINGEN Magdeburg Sachsen-Anhalt Halle S. Bad Lauchstädt Potsdam Niemegk Leipzig BERLIN 2 4 Zeuthen Teltow BRANDENBURG SACHSEN 2008: PHELIX (Petawatt Hoch- Energie Laser für SchwerIoneneXperimente) 500 TW RHEINLAND-PFALZ SAARLAND Darmstadt Stammsitz* Zweig- bzw. Außenstelle* Heidelberg Lampoldshausen Karlsruhe Stuttgart BAYERN * mit Anzahl der Einrichtungen in einer Gemeinde BADEN-WÜRTTEMBERG Neuherberg Garching München Oberpfaffenhofen Ú Ion-laser interactions Ú X-ray laser 22 October 2013 Markus Büscher 44

45 Big lasers in the HGF: e.g. Dresden-Rossendorf List Helgoland SCHLESWIGHOLSTEIN Greifswald HAMBURG Geesthacht Bremerhaven MECKLENBURG-VORPOMMERN 2008: High-Power Laser Laboratory 150 TW laser DRACO (Dresden laser acceleration source) BREMEN NIEDERSACHSEN Potsdam Braunschweig BERLIN 2 4 Magdeburg WolfenbüttelRemlingen NORDRHEIN-WESTFALEN Niemegk Zeuthen BRANDENBURG Sachsen-Anhalt Göttingen Teltow 2012: PW Laser Halle S. Jülich Bonn Köln Bad Lauchstädt Sankt Augustin Leipzig SACHSEN HESSEN THÜRINGEN RHEINLAND-PFALZ Stammsitz* Darmstadt Zweig- bzw. Außenstelle* SAARLAND Heidelberg Lampoldshausen Karlsruhe BAYERN * mit Anzahl der Einrichtungen in einer Gemeinde Stuttgart BADEN-WÜRTTEMBERG Neuherberg 22 October 2013 Garching München Oberpfaffenhofen Ú Laser particle acceleration Ú Cancer research Markus Büscher 45

46 JuSPARC = Jülich short-pulse particle and radiation centre Manufacturer Wave length Amplitude Technologies 800 nm Focus Ø 20 µm Peak power Pulse energy Pulse length Repetition rate 1.5 PW 40 J fs 5 Hz 22 October 2013 Markus Büscher 46