1. AWAKE: A Proton-Driven Plasma Wakefield Acceleration Experiment at CERN C. Bracco on behalf of the AWAKE collaboration C. Bracco - ICHEP2014

2. Outlines  Motivation  AWAKE at CERN  Experimental Setup  Needed modifications  Planning and milestones  Next steps  Summary C. Bracco - ICHEP2014

3. Motivation C. Bracco - ICHEP2014  A plasma acts as an energy transformer: energy is transferred from the driver to the witness bunch that is accelerated.  The maximum energy gain of the accelerated beam in a single plasma stage is limited by the energy of the driver  Current proton synchrotrons are capable of producing high energy protons, reaching up to multi TeV (the LHC)  proton bunches are the most promising drivers of wakefields to accelerate electrons to the TeV energy scale  Lepton colliders driver medium witness

4. Motivation C. Bracco - ICHEP2014  A plasma acts as an energy transformer: energy is transferred from the driver to the witness bunch that is accelerated.  The maximum energy gain of the accelerated beam in a single plasma stage is limited by the energy of the driver  Current proton synchrotrons are capable of producing high energy protons, reaching up to multi TeV (the LHC)  proton bunches are the most promising drivers of wakefields to accelerate electrons to the TeV energy scale  Lepton colliders p+ beam = driver plasma =medium e- beam = witness

5. Motivation C. Bracco - ICHEP2014  At present, metallic cavities achieve maximum accelerating gradients around 100 MV/m  10s Km to reach the TeV scale in a conventional linear accelerator.  A plasma is a medium consisting of ions and free electrons  it can sustain very large electric fields (>GV/m)  more compact machines*! *According to simulations, it is possible to gain 600 GeV in a single passage through a 450 m long plasma using a 1 TeV p+ bunch driver of 10e11 protons and an rms bunch length of 100  m p+ beam = driver plasma =medium e- beam = witness

6. AWAKE at CERN C. Bracco - ICHEP2014 CNGS physics program completed in 2012 SPS TT41 TI8 Dump CNGS Target ~ 1100 m

7. AWAKE at CERN C. Bracco - ICHEP2014 SPS TT41 TI8 Dump AWAKE ~ 1100 m 10 m long plasma Rb vapor cell

8. Experimental Setup Phase 1 C. Bracco - ICHEP2014 Laser Plasma cell Laser dump SPS p+ beam p+ dump OTR for SMI diagnostics p+ beam Characteristics # bunches1 p+ per bunch3e11 Repetition rate0.5 Hz r.m.s. norm. emittance3.5 mm mrad Bunch length12 cm (0.4 ns) Momentum400 GeV/c Momentum spread0.35% Laser beam Characteristics Power2 TW Pulse wavelength260 nm Repetition rate10 Hz Pulse length10 ps Pulse energy 32  J

9. Experimental Setup Phase 1 C. Bracco - ICHEP2014 Laser Plasma cell Laser dump SPS p+ beam p+ dump OTR for SMI diagnostics  Condition to excite large amplitude wakefields:  z ~ p (~1 mm)  A long (  z =12 cm) and narrow (  x,y =200  m) particle bunch in a dense plasma experiences a two-stream instability or Self Modulation Instability (SMI)  modulation into micro-bunches with  z ~ p.  The laser is used to ionize the plasma and seed the SMI in a controlled way

10. Experimental Setup Phase 1 C. Bracco - ICHEP2014 Laser Plasma cell Laser dump SPS p+ beam p+ dump OTR for SMI diagnostics Requirements for SMI:  Laser and proton beam synchronized at the 100 ps level  Laser and proton beam coaxial over the full length of the plasma cell  100  m and 15  rad proton pointing accuracy (800 m long Transfer Line, during CNGS operation an rms pointing accuracy, averaged over several days, of 50  m was measured)  high resolution diagnostics to perform and monitor relative alignment  Plasma density uniformity better than 0.2% (  = 10 14 - 10 15 cm -3 )

11. Experimental Setup Phase 1 C. Bracco - ICHEP2014 Laser Plasma cell Laser dump p+ dump OTR for SMI diagnostics SPS p+ beam *prototype, the real cell will be 10 m long *

12. Experimental Setup Phase 1 C. Bracco - ICHEP2014 Physics goal: study the physics of self-modulation. Dedicated diagnostics! Laser Plasma cell Laser dump SPS p+ beam p+ dump OTR for SMI diagnostics  OTR and ~ps (~100 fs) resolution streak camera  Additional CTR and TCTR for: high frequency (273 GHz) and broadband (500 GHz) measurements

13. Experimental Setup Phase 2 C. Bracco - ICHEP2014 e- beam Characteristics # bunches1 e- per bunch1.2e9 Repetition rate10 Hz r.m.s. norm. emittance2 mm mrad Bunch length1.2 mm (4 ps) Momentum10-20 MeV/c Momentum spread0.5% Main physics goal: probe proton driven wakefield acceleration with a witness e- bunch. OTR for SMI diagnostics Laser dump Laser RF gun e- spectrometer Plasma cell SPS p+ beam p+ dump e- beam

14. Experimental Setup Phase 2 C. Bracco - ICHEP2014 FC E,  E MS BPR Laser +Diagnostics RF GUN Emittance Incident, Reflected Power and phase Spectrometer Corrector MTV VPI FCT Accelerator MTV, Emittance Matching triplet BPR Incident, Reflected, transmitted Power Klystron OTR for SMI diagnostics Laser dump Laser RF gun e- spectrometer Plasma cell SPS p+ beam p+ dump e- beam

15. Experimental Setup Phase 2 C. Bracco - ICHEP2014 FC E,  E MS BPR Laser +Diagnostics RF GUN Emittance Incident, Reflected Power and phase Spectrometer Corrector MTV VPI FCT Accelerator MTV, Emittance Matching triplet BPR Incident, Reflected, transmitted Power Klystron Photo injector (PHIN) used for the CLIC test facility at CERN (5 MeV electrons) OTR for SMI diagnostics Laser dump Laser RF gun e- spectrometer Plasma cell SPS p+ beam p+ dump e- beam

16. Experimental Setup Phase 2 C. Bracco - ICHEP2014 FC E,  E MS BPR Laser +Diagnostics RF GUN Emittance Incident, Reflected Power and phase Spectrometer Corrector MTV VPI FCT Accelerator MTV, Emittance Matching triplet BPR Incident, Reflected, transmitted Power Klystron e- beam diagnostics (current, profile, etc.) OTR for SMI diagnostics Laser dump Laser RF gun e- spectrometer Plasma cell SPS p+ beam p+ dump e- beam

17. Experimental Setup Phase 2 C. Bracco - ICHEP2014 FC E,  E MS BPR Laser +Diagnostics RF GUN Emittance Incident, Reflected Power and phase Spectrometer Corrector MTV VPI FCT Accelerator MTV, Emittance Matching triplet BPR Incident, Reflected, transmitted Power Klystron Booster linac (1 m): 5 MeV  20 MeV OTR for SMI diagnostics Laser dump Laser RF gun e- spectrometer Plasma cell SPS p+ beam p+ dump e- beam

18. Experimental Setup Phase 2 C. Bracco - ICHEP2014 FC E,  E MS BPR Laser +Diagnostics RF GUN Emittance Incident, Reflected Power and phase Spectrometer Corrector MTV VPI FCT Accelerator MTV, Emittance Matching triplet BPR Incident, Reflected, transmitted Power Klystron e- beam line OTR for SMI diagnostics Laser dump Laser RF gun e- spectrometer Plasma cell SPS p+ beam p+ dump e- beam

19. Experimental Setup Phase 2 C. Bracco - ICHEP2014 MBPS magnet (CERN) 1.84 T 3.80 Tm Horiz. Aperture: 300 mm L=1670 mm W=1740 mm 15 t e- spectrometer OTR for SMI diagnostics Laser dump Laser RF gun e- spectrometer Plasma cell SPS p+ beam p+ dump e- beam

20. Experimental Setup Phase 2 C. Bracco - ICHEP2014 p+ e-e- Scintillator screen Camera OTR for SMI diagnostics Laser dump Laser RF gun e- spectrometer Plasma cell SPS p+ beam p+ dump e- beam

21. Simulation of e- Beam Dynamics in Plasma

22.  Trapping efficiency: 10-15% (high sensitivity diagnostics)  Average energy gain: 1.3 GeV  Energy spread: ± 0.4 GeV  Angular spread up to ± 4 mrad Exit of plasma cell Large acceptance (aperture and magnetic field) spectrometer

23. C. Bracco - ICHEP2014 TargetHorn TSG41 Storage gallery (120 m) Proton beam line TT41 Target chamber Access Gallery CNGS  AWAKE CNGS

24. C. Bracco - ICHEP2014 TargetHorn TSG41 Storage gallery (120 m) Proton beam line TT41 Target chamber Access Gallery CNGS  AWAKE CNGS AWAKE

25. Planning C. Bracco - ICHEP2014 201320142015201620172018 Proton beam- line Experimental area Electron source and beam-line Installation Studies, design FabricationInstallation Commissioning data taking Commissio ning data taking Modification, Civil Engineering and installation Study, Design, Procurement, Component preparation Study, Design, Procurement, Component preparation  June 2012 first AWAKE collaboration meeting (Lisbon)  AWAKE Design Report completed in February 2013  Project approved in August 2013  Works ongoing (excavation of e- and laser tunnel starting on July 4 th 2014)  First p+ and laser beam in 2016 (Phase 1)  First e- beam in 2017-2018 (Phase 2)

26. Next Steps  New technology plasma cell for acceleration (Helicon, Argon plasma discharge)  Need ultra-short e- bunches (≥300 fs)  bunch compression!  Almost 100% capture efficiency  Narrower energy spread and large transfer efficiency (~GV/m)

27. Summary  Proton bunches are the most promising drivers of wakefields to accelerate electrons to the TeV energy scale  Lepton colliders  AWAKE is a proof of principle accelerator R&D experiment which is currently being built at CERN:  400 GeV SPS protons as drive beam  2 TW laser for plasma ionization and seeding of SMI  10-20 MeV electrons as witness bunch  AWAKE goals:  Study the physics of self-modulation as a function of plasma and beam parameters (2016)  Probe longitudinal accelerating wakefields with externally injected electrons (2017-2018)  Study injection dynamics and production of multi-GeV electron bunches (2022)  Final scope:  Accelerate electrons up to 100 GeV in 100 m  “Good quality” beams  TeV e+e- colliders!

28. C. Bracco - ICHEP2014 THANK YOU FOR YOUR ATTENTION

29. C. Bracco - ICHEP2014 Back up slides

30. Abstract The AWAKE Collaboration has been formed in order to demonstrate proton- driven plasma wakefield acceleration for the first time. This technology could lead to future colliders of high energy but of a much reduced length compared to proposed linear accelerators. The CERN SPS proton beam in the CNGS facility will be injected into a 10 m plasma cell where the long proton bunches will be modulated into significantly shorter micro-bunches. These micro- bunches will then initiate a strong wakefield in the plasma with peak fields above 1 GV/m that will be harnessed to accelerate a bunch of electrons from about 20 MeV to the GeV scale within a few meters. The experimental program is based on detailed numerical simulations of beam and plasma interactions. The main accelerator components, the experimental area and infrastructure required as well as the plasma cell and the diagnostic equipment are discussed in detail. First protons to the experiment are expected at the end of 2016 and this will be followed by an initial 3-4 year experimental program. The experiment will inform future larger-scale tests of proton-driven plasma wakefield acceleration and applications to high energy colliders. C. Bracco - ICHEP2014

31. SMI C. Bracco - ICHEP2014 Controlling the initial SMI seeding fields and shifting the laser position with respect to the proton bunch  change the number of protons effectively available to drive the SMI. Optimal configurations leading to larger acceleration gradients in comparison to half-cut bunches can be scanned by varying the delay between ionizing laser and SPS proton bunch in AWAKE. The front of the laser beam also sets the initial phase of the wakefield, thereby fixing the position of the accelerating/decelerating wakefield regions relative to the position of the laser. The optimal injection position of external electron bunches can therefore be determined by scanning different electron injection positions

32. Experimental Setup Phase 1 C. Bracco - ICHEP2014 Laser Plasma cell Laser dump SPS p+ beam p+ dump OTR for SMI diagnostics 3 m long prototype

33. Experimental Setup Phase 1 C. Bracco - ICHEP2014 Laser Plasma cell Laser dump p+ dump OTR for SMI diagnostics SPS p+ beam Ultra-fast (15 ms) valves > 40 000 cycles!

34. Phase I – Proton Bunch Self-Modulation OTR + Streak Camera (MPI Munich) Edda Gschwendtner, CERN34 Plasma density: n e = 7 E14 cm -3.  Plasma wavelength = 1.2 mm  4 ps  Streak camera with ~ps resolution  Direct evidence of the occurrence of the SMI.

35. Phase I – Proton Bunch Self-Modulation Coherent Transition Radiation - CTR MPI Munich) Edda Gschwendtner, CERN35 Real-time Oscilloscop e Broadband Detector 237.5 GHz Filter p+p+ Spectrum analyzer 237.5 GHz Mixer ~ Oscillator e.x: 228.5 GHz p+p+ Coherent radiation around plasma wavelength emitted (microwave frequency range 100-400GHz)  Intense signal: for 2mm 2 antenna several Watts of radiation power. B) A) A) Look at cut-off frequency  Use cut-off waveguides B) Mix with local oscillator signal, detect intermediate frequency signal with fast oscilloscope  Direct evidence of the occurrence of the SMI.

36. Phase I – Proton Bunch Self-Modulation Edda Gschwendtner, CERN36 Transverse Coherent Transition Radiation - TCTR (MPI Munich) Probe configuration Transverse CTR  Normal E-field component to the screen  Signal is modulated by beam density to first order  237.5 GHz @ n e ~ 7*10 14 cm -3  Hundredths of kV/m at about 10 mm distance Micro-bunches metal foil Transverse coherent transition radiation disc Use transverse coherent radiation to frequency modulate a probe laser: Radiation modifies birefringency of crystal  modifies laser pulse sidebands.  Measurement of p + -bunch modulation frequency and amplitude  MPI plans to have first tests end 2014 at DESY/Zeuthen

37. p+ Beam Line C. Bracco - ICHEP2014  Displace existing magnets of final focusing to fulfill optics requirements at the entrance of the plasma cell  Move existing dipole + 4 additional dipoles to create a chicane for laser mirror integration  x,y = 200  m

38. Laser Beam C. Bracco - ICHEP2014 p+  1m compressor 2 x 1 m optical table SAS CV units 4m 3m 0.9m 2 x 1 m optical table 2.5 x 1 m optical table 2.5 x 1 m optical table Fore-vacuum laser transfer line for e-gun (on the ceiling) PP+ power supply 600x600x(H)850 CCM rack 700x800x(H)1400 ~1m Laser system comprises:  Laser with 2 beams (for plasma and for the e-gun)  Delay line in either one of these beams  Focusing telescope (lenses, in air), 40m long focusing  Optical compressor (in vacuum)  Small optical in-air compressor and 3 rd harmonics generator for e-gun RF gun New tunnel

39. e- Beam Line Completely new beam line and tunnel for the e- beam Common beam line for p+ and e- over the last ~5 m before plasma cell Common diagnostics for very different beams (very low e- beam intensity wrt p+) Flexible e- beam optics: the focal point can be varied by up to 6 m inside the plasma cell. New tunnel

40. Next Steps C. Bracco - ICHEP2014 OTR for SMI diagnostics Laser dump Laser RF gun e- spectrometer Plasma cell SPS p+ beam p+ dump e- beam Side-injection  Smaller momentum spread of the e- beam at the exit of plasma cell  Integration issues and need of custom- built and expensive designs for vacuum and diagnostics.  No direct measurement of e- beam inside plasma (angle? merging point?)