1. AWAKE Run 2 : 1) Interstage considerations 2) CALIFES as plasma technology test facility Erik Adli and Carl A. Lindstrøm University of Oslo, Norway AWAKE Physics and Experiments Board CERN, 2016-06-07

2. The AWAKE Experiment 2 Phase 1: Understand the physics of self-modulation instability processes in plasma. - Self-modulated proton bunch resonantly drives wakefields in the plasma  start Q4 2016  start Q4 2017 Phase 2: Probe the accelerating wakefields with externally injected electrons. - Demonstrate GeV scale gradients with proton driven wakefields AWAKE Run 1, 2016-2018 Laser dump e - ( ~ 4 ps, 16 MeV) SPS protons 10m plasma SMI Acceleration Proton beam dump RF gun Laser p Proton diagnostics BTV,OTR, CTR e - spectrometer AWAKE Run 1: Rb vapour source. Temperature-stability to 0.2%. Fulfills temperature (density) variation requirements for phase 1 and 2.

3. + does not need laser ionization + fully modular (no gaps) - uniformity (spatial, temporal) needs work - relatively complex (expensive?) + does not need laser ionization + cost effective? - uniformity needs work - scaling? Gaps, windows -  s discharge time ? Run 2 sources (scaleable) Helicon development Gas discharge developmentFurther Rb source development + will be proven by Run 2 + uniformity, stability - Max. length driven by laser -> stages - cost (laser needed per 10 m?) Current prototype in Greifswald For Run 2 and/or later runs : alternative plasma sources Prototype by IST/ICL

4. Run 2 Laser dump Optimized SPS protons 10m plasma SMI Proton beam dump RF gun Laser Proton diagnostics BTV,OTR, CTR e - spectrometer ~4m plasma e - ( ~ 100s fs, > 20 MeV) Bunch compression, increased acceleration e - emittance measurement Time horizon for development of alternative plasma sources : we do not need alternative plasma sources right away in order to perform electron beam acceleration experiments. More realistic may be to continue the two-stage physics studies with proven technology. 4 “Phase 3” “Phase 4” Demonstrate scalability of the AWAKE concept sustain gradient in SMI wake over long distance scalable length plasma sources Accelerate an electron beam, while preserving beam quality as well as possible injection: into the wake of an already modulated proton beam (SMI, or RF-bunching?) generate optimum electron bunch to be accelerated Acceleration

5. Staging of first two ceels 5 Laser dump Optimized SPS protons 10m plasma SMI Acceleration Proton beam dump RF gun Laser Proton diagnostics BTV,OTR, CTR e - spectrometer ~4m plasma e - ( ~ 100s fs, > 20 MeV) Bunch compression, increased acceleration e - emittance measurement Discussed earlier: effect of vacuum gap (interstage) on proton beam evolution.  Alexey: 50% of gradient with 1 m of gap.  See Steffen’s presentation Long enough for ebeam injection? Short enough to not degrade proton beam w/o optics? Time horizon for development of alternative plasma sources : we do not need alternative plasma sources right away in order to perform electron beam acceleration experiments. More realistic may be to continue the two-stage physics studies with proven technology.

6. The AWAKE Experiment 10m plasma ? SMI Acceleration Proton beam dump RF gun Laser Proton diagnostics BTV,OTR, CTR e - spectrometer ~4m plasma e - ( ~ 100s fs, > 20 MeV) Bunch compression, increased acceleration Optimized SPS protons “Scalable plasma source”. Practically and economically feasible for 100s of meters of plasma.

7. The AWAKE Experiment 20m plasma? SMI Acceleration Proton beam dump RF gun Laser Proton diagnostics BTV,OTR, CTR e - spectrometer ~4m plasma e - ( ~ 100s fs, > 20 MeV) Bunch compression, increased acceleration e - emittance measurement Optimized SPS protons “Scalable plasma source”. Practically and economically feasible for 100s of meters of plasma. Of the three technologies discussed, seems like only the helicon source can be extended for long distances without introducing new vacuum gaps. Rb source: laser ionized. Need new laser beam inserted every 10-20 m Discharge source: see Nelson’s talk.

8. Does a short “injection-free” interstage pose a problem ? SMI Acceleration RF gun Laser ~4m plasma e - ( ~ 100s fs, > 20 MeV) Bunch compression, increased acceleration Optimized SPS protons Acceleration “Injection-free interstage” Gap between long cells may not need to be as long as the first gap (1 m). Both ebeam and pbeam continues straight. For Rb source a laser beam needs to be injected What follows: a small study on electron beam interstage possibilities, assuming a minimum vacuum gap size of 10 cm + 10 cm. Similar to the study Marlene and Alexey performed, but with chromaticity considerations and discussion of plasma lenses. “ebam interstage”

9. Electron beam parameters - Energy 10 GeV (after first accelerating stage) -We assume at plasma exit beta mat = 4.1 cm (matched to ion channel of n 0 = 7e14/cm3) -Without any focusing, ebeam size will increase by a factor 5 (unacceptable) -Task : match back into next channel

10. Proton beam parameters In the following : some plots of the proton beam from the reference simulation to have a better idea of the phase space.

11. 100% of the initial charge. Initial proton beam focused down to beta = 4.5 m Particle dump from LCODE (courtesy of Konstantin and Alexey)

12. Beam after 10 m

13. 100% of the charge. Which particles drive the wake?

14. r < p. 30% of the charge.

15. r < k p -1. 3.5% of the charge.

16. Proton beam -Not evident how to make quick estimates, since the beta function of the proton beam depends strongly on the radius. -Based on Alexey’s graph we adopt for this mini-study ~0.5 m as the allowed total length for the vacuum gap (10 cm + 10 cm + up to 30 cm for electron optics). We assuming the proton beam is unperturbed by the electron focusing. This need to be studied in further detail.

17. (See Carl’s slides)

18. CALIFES

19. 4 A, 1.4us 120 MeV 4 A, 1.4us 120 MeV 30 A, 140 ns 120 MeV 30 A, 140 ns 120 MeV 30 A, 140 ns 60 MeV 30 A, 140 ns 60 MeV The CLIC Test Facility at CERN Drive Beam Linac Probe Beam Linac : CALIFES 200 MeV S-band linac, with RF-gun. Fits entirely inside the CLEX room. 19

20. Background The CLIC Test Facility at CERN, CTF3, is on schedule to reach its main objectives by the end of 2016 (thorough demonstration of the CLIC two-beam scheme, and much more) Scheduled to shut down end of 2016 Based on a study started in 2014, we propose to continue the operation of CALIFES, as an generic electron beam test facility, beyond 2016 Strong interest in using CALIFES for R&D, both CERN and external institutes A written proposal was sent to the CERN management. Answer was encouraging. After a science workshop in October, the management want a summary of the user interests with recommendations before the final approval. It is expected that external institutes and users contribute to the experimental integration and operation 20

22. CALIFES parameters Photo-injector: provides easily adjustable beam parameters, over a large range. 22 Future users are encouraged to proposing upgrades to facility. Example: bunch compression.

23. CALIFES as electron beam PWFA facility / plasma technology test facility Dual interests of having a plasma source available at CALIFES : 1)Perform electron beam-driven PWFA experiments, with the CALIFES beam and a plasma source. Some (old) slides here :https://www.dropbox.com/s/92rz88ofih7265y/20141216_CTF3_PWFA.pptx?dl=0https://www.dropbox.com/s/92rz88ofih7265y/20141216_CTF3_PWFA.pptx?dl=0 2)For AWAKE Run 2 : developing scalable plasma source technology further Will not be a high-gradient facility (in the sense GV/m), rather a precision experiment facility (small incoming emittance, well- instrumented) PWFA studies relevant for both AWAKE and for PWFA-LC can be done with AWAKE plasma densities.

24. Some first thoughts on CALIFES relevance for AWAKE Run 2 ++ Discharge source Plasma lens Test and development of plasma lenses Development of plasma sources Plasma source staging experiment Advanced interstage plasma lens experiments Relevance for AWAKE : CALIFES BEAM

25. Summary Options open for “scalable” plasma source for Run 2 Gap between plasma cells tricky, even if short. May benefit from some sort of plasma lens – Plasma density tolerances not discussed in this talk CALIFES provides an opportunity to test and develop plasma sources and lenses with an electron beam ICL has expressed interest in testing their discharge source in CALIFES (Nelson’s talk) Helicon sources may also be proposed for CALIFES Funding?