Neue Methoden der Teilchenbe-schleunigung

1. NeueMethodenderTeilchenbe-schleunigung R.W. Aßmann Herbstschule der Teilchenphysik, Maria Laach, 2010 Accelerator Beam Physics Group Beams Department - CERN

2. Content • Lecture 1: Old and New Acceleration Techniques • Lecture 2: Experimental Status • Principle of plasma-based acceleration • Beam-driven experiments • Laser-driven experiments • Beyond this • Lecture 3: Towards a Plasma Linear Collider

3. A Great Idea or More?

4. M. Downer, U. Texas

5. Principle of Plasma-Based Acceleration

6. Concepts For Plasma-Based Accelerators Pioneered by J.M. Dawson • Plasma Wake Field Accelerator(PWFA) • A high energy electron/proton bunch • Laser Wake Field Accelerator(LWFA) • A single short-pulse of photons • Plasma Beat Wave Accelerator(PBWA) • Two-frequencies, i.e., a train of pulses • Self Modulated Laser Wake Field Accelerator(SMLWFA) • Raman forward scattering Instability evolves to Courtesy T. Katsouleas

7. Laser Plasma = ion = electron Basic principle and scaling rules 1 I) Generate homogeneous plasma channel: Gas II) Send dense electron beam towards plasma: Beam density nb > Gas density n0 Beam excited plasma. Also lasers can be used (laser wakefield acceleration).

8. Electrons are expelled r Ion channel z Basic principle and scaling rules 2 III) Excite plasma wakefields: Space charge force of beam ejects all plasma electrons promptly along radial trajectories Pure ion channel is left: Ion-focused regime, underdense plasma

9. n Drive beam Quasineutral plasma n0 r Ion channel an (neutralization radius) Basic principle and scaling rules 3 Equilibrium condition: Ion charge neutralizes beam charge: Beam size SLC: nb/n0 = 10 Beam and plasma densities determine most characteristics of plasma wakefields!

10. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - + + + + + + + + + + + + + + + - + + + + + + + + + + + + + + + - - - - - - - - - + + + + + + + + + + + + + + + + - - + + + + + - + + + + + - + + + + - + - + - + + + + + - + + + + + + + + + + + + + + + + + + + - - - - - - - - - - - electron beam - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Ez Basic principle and scaling rules 4 Electron motion solved with ... Space charge of drive beam displaces plasma electrons. driving force: Space charge oscillations (Harmonic oscillator) Plasma ions exert restoring force restoring force: Longitudinal fields can accelerate and decelerate!

12. Basic principle and scaling rules 5 Wavelength: Accelerating field (roughly) Plasma density n0 1014 to 1015... lp ~ mm ~ GV/m

13. Basic principle and scaling rules 6 Plasma ions move relatively little  transverse focusing gradient: Plasma structures are also super-strong quadrupoles (many kT/m)!

14. Makes Things Difficult… • Conventional acceleration structures: • Optimized to provide longitudinal acceleration and no transverse forces on the beam. • Due to imperfections, transverse forces can be induced. These “wakefields” caused major trouble to the first and only linear collider at SLAC. • Plasma acceleration: • Ultra-strong longitudinal fields  high accelerating gradient. • Ultra-strong transverse fields  transverse forces cannot be avoided and must be controlled. • How does the beam look like?

15. Worries • Acceleration only over very short distances  energy gain not interesting (“100 GV/m in 1 mm”). • Transverse fields ruin the beam  huge spot size will make the beam unusable. • Various particles in the bunch get different energy gains  dispersion of energy makes beam unusable (large energy spread, no “mono-energetic” beam). • Strong experimental efforts over last 30 years to address these worries…

16. Slide: T. Raubenheimer, ICHEP

17. Beam-Driven Experiments: SLAC

18. Parameters for SLAC Beam • Beam energy: 50 GeV • Bunch population: 4 x 1010 • Repetition rate: 60 Hz • Energy per pulse: 320 J • Spot size: 10 mm • Pulse width: 50 fs • Focused intensity: 7 x 1021 W/cm2

19. One vs Two Bunches • Ideally: Two bunches within short distance. • A first short bunch to drive the plasma wake field (“drive”). • The drive bunch pumps energy into the plasma and is decelerated. • A second short bunch at the right distance (“witness”). • The witness bunch is accelerated. • Problem: • Lifetime of plasma structure is only a few ps. • Not possible to generate two bunches within such short distance in the SLAC linac. • Trick: • Use a longer bunch to both drive and witness the plasma wakefield. • Head and core of bunch are declerated. • Tail of bunch is decelerated.

20. Ideal Two Bunch Scheme

21. Experimental Layout

25. UCLA Beam Propagation Through A Long Plasma • Smaller “matched” beam size at the plasma entrance reduces amplitude of the betatron oscillations measured at the OTR downstream of the plasma • Allows stable propagation through long plasmas (> 1 meter ) E-162 Run 2 E-157 sx (µm) Plasma OFF Phase Advance  ne1/2L Phase Advance  ne1/2L C. E. Clayton et al., PRL 1/2002 E-157/E-162 collaboration

26. UCLA E-162: Use Imaging Spectrometer To Measure Energy Loss & Gain Preliminary… Picosecond Gaussian Slice Analysis of Many Events Average energy loss (slice average): 159 ± 40 MeV Average energy gain (slice average): 156 ±40 MeV (≈1.5 ×108 e-/slice) E-162 collaboration

28. More than 1 GeV Acceleration E167 collaboration SLAC, UCLA, USC

29. Record Acceleration: 42 GeV E167 collaboration SLAC, UCLA, USC I. Blumenfeld et al, Nature 445, p. 741 (2007)

30. Laser-Driven Experiments

31. Advantages of Lasers • Most experiments around the world work on laser acceleration. • Lasers can be procured in a university framework. • With laser-generated wakefields you can capture and accelerate plasma-electrons to generate the beam from scratch. • With present state-of-the-art one can create mono-energetic beams this way! • No need for heavy beam infrastructure up to some beam energy. • The more powerful your laser, the higher the energy of the beam that you can create!

32. The “Power” of Lasers GeV beams are now state-of-the-art!

33. Slide: T. Raubenheimer, ICHEP

34. Laser-Driven Wakefield B. Hidding

35. Experimental Setup 7.5 TW peak Ti:Saphir-Lasersystem JETI am Institut für Optik und Quantenelektronik (IOQ) der Friedrich-Schiller-Universität Jena B. Hidding

36. Plasma Channel Forming B. Hidding

37. Mono-Energetic Electron Beam B. Hidding

38. Experiments in Dresden: ELBE  Preparing a 200 TW laser! B. Hidding

39. German Results Overview • Different regimes are being exploited. • Characterized by plasma density and laser parameters. SMLWFA, Jena Capillar, MPQ Garching LWFA, MPQ Garching B. Hidding

40. Pioneering Role: LBNL E. Esarey

41. 3cm gas-fill capillary 4cm ablative capillary 1 GeV capillary accelerator experiment at LBNL/Oxford U. 0.56 GeV capillary accelerator experiment at CAEP/KEK Slide T. Tajima

42. Stable electron beams and more high-energies from 1 cm gas jet at GIST, Korea 100TW laser system at Gwangju Institute of Science and Technology Intensity (arb.u.) Intensity (arb.u.) Recent results at 50 TW Divergence Angle (mrad) Electron Beam Energy (MeV) Mean electron energy = 236.9 MeV SD/Mean E = 5 % Charge: ~100pC Divergence angle: ~a few mrad Slide T. Tajima (N. Hafz et al., nature photonics, 2, 571, 2008)

43. Example: Advances of Laser Andreas Tünnermann

44. Beam Quality and Output Power Andreas Tünnermann

45. The New Livingston Plot B. Hidding

46. Gradient vs Plasma Wavelength B. Hidding

47. Kilometer-scale X-ray FEL Linac Coherent Light Source X-ray Holography Microscope Hologram Beam stop Coherent X-ray Pin hole sample CCD camera Zone plate Laser-driven table-top X-ray Free Electron Laser Slide T. Tajima The “dream” starts…

48. Beyond This…

49. EuroLEAP

50. ELI European Project for development of extreme light Beam acceleration is one work package … hundreds of GeV …