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Beam manipulation by THz self-wakefield at ATF (I)

Explore experiments at ATF involving beam manipulation, energy modulation, transformer ratio enhancement, and technology/software. Drive advancements in high-gradient acceleration for FEL light sources. Collaboration with UCLA, SLAC, and Euclid. Focus on chirp compensation and diamond-based structures.

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Beam manipulation by THz self-wakefield at ATF (I)

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  1. ATF Users Meeting BNL, April 26-27, 2012 Beam manipulation by THz self-wakefield at ATF (I) A.Kanareykin Euclid TechLabs LLC, Gaithersburg, MD

  2. Outline • Proposed experiments • Chirp Compensation • Energy Modulation • Transformer Ratio Enhancement • What technology, software and material we’ve got to accomplish it ? • Beam manipulation • Electromagnetic simulations software • Diamond based structures • Nonlinear materials

  3. Proposal • We are pursuing three experiments at the ATF, two related to beam manipulation by its self-wakefield and one – a direct wakefield acceleration: • A demonstration of a tunable beam energy chirp compensator. • The conversion of self-wake energy modulation into a THz bunchtrain. • A demonstration of enhanced transformer ratio by a shaped beam.

  4. Motivation • Light source is an intrinsic requirement for current and future scientific research. Particularly, ultrashort x-ray pulses are a powerful tool for addressing grand challenges in science. • One particular obstacle limiting construction of FEL light source facilities is the cost, particularly, linacs to provide high energy, high brightness beam. • wanted: gradient >100MV/m, peak current >1kA, rep~1MHz, E~ a few GeV, etc. • In the past few years, the field of high gradient acceleration, aimed at the future high energy linear collider, achieved many impressive results. • e.g. GV/m level in THz; 100 MV/m in MW demonstrated in DWA structures; wanted E ~200- 300 MV/m, R>10.

  5. Currently Available Beam Resources for Euclid’s Experiments.

  6. Euclid THz DWA structures at FACET 23GeV, 3nC, r~10µm, z~30µm Through Collaboration E201 (UCLA/SLAC/Euclid) e- Kraken Chamber by UCLA/SLAC

  7. Chirp Compensation Chirp compensation: The free electron laser (FEL) is considered to be the main candidate for a short wavelength (UV to X-ray), short pulse (femto- to attosecond) light source. Demands: (1) high repetition rate (~MHz) (2) high peak current (a few kA); (3) low emittance (sub-micron emittance). At the output of the last compressor - a small energy chirp. It is required that this relatively small energy spread be compensated using a specially designed device. This compensation can be realized by a simple wakefield device. In 2011 we demonstrated energy compensation at the ATF [Antipov et al, PRL, 2012]. We now propose to test and demonstrate the first tunable energy chirp compensating system.

  8. Energy modulation Energy modulation conversion into a THz bunchtrain: a follow up experiment to our 2011 experimental program [Antipov et al, PRL 2012]. We observed energy modulation produced by a self-wake on an originally chirper beam. This energy modulation can be transferred into density modulation via a chicane. We propose to perform this transformation at the ATF. This process of self-wake energy modulation and a follow up conversion into a THz bunchtrain is the basis of an inexpensive, table top, high power THz source.

  9. Transformer Ratio Enhancement The transformer ratio: a high transformer ratio leads to a higher overall efficiency. The experiment will be the first demonstration of enhanced transformer ratio from a triangular shaped beam. This experiment is similar to the diamond structure wakefield mapping accomplished at the ATF in 2011 [Antipov et al, APL 2012]. We propose to use a motorized mask to produce a drive beam followed by a witness beam at variable distance.

  10. + r (z) W - W z d d d Transformer Ratio Enhancement Using a Bunchtrain Ramped Bunch (2007) Ramped Bunch Train Reference: Bane et. al., IEEE Trans. Nucl. Sci. NS-32, 3524 (1985) R2=3.4 Measured Enhancement factor of R2/R1=1.31 Inferred R2=2.3 Reference: Schutt et. al., Nor Ambred, Armenia, (1989)

  11. Key Technology --- bunch shaping to enhance transformer ratio TR~10 Triangular bunch Double triangular bunch TR~17 (STAB, 2012)

  12. An example ---using EEX technique Simplified sketch of the EEX beamline. Refer to Sergey’s

  13. Software Developed for DLA Waveguide’09 Multibunch’09 Rectangular’11 BBU’300 Energy Modulation’11

  14. Dielectrics Tested as DLA Loading THz experiments at ATF

  15. Motivation for CVD Diamond for DLA • CVD DIAMOND PROPERTIES: • - DC BREAKDOWN THRESHOLD OF ~ 2 GV/m • LOSS FACTOR DOWN TO 5-9 x10-5 AT 30-140 GHz • HIGHESTTHERMAL CONDUCTIVITY • MULTIPACTING CAN BE SUPPRESSED • and • CVD DEPOSITION NOW CAN BE USED TO FORM CYLINDRICAL WAVEGUIDES Element Six Element Six

  16. 35 GHz Diamond Based DLA Structure CVD diamond tube fabrication

  17. THz Diamond Tubes Scanning electron microscope images of a THz diamond microstructure produced using the hot wire deposition technique. THz diamond structure: ID = 100 μm, thickness 70 μm, 1 cm long (Bristol University, UK) Single crystal diamond

  18. Experimental Report on A Diamond Based Wakefield Structures (DoE SBIR ext. Phase II project, 2012)

  19. Wakefield Mapping of a Diamond Slab Structure at BNL/ ATF • 1st wakefield mapping experiment in THz regime (June 2011). • 1st wakefield acceleration observed in THz regime. • S. Antipov, et al, App. Phy. Lett. March 2012. 0.25 THz

  20. High Grad. Breakdown Study of A Diamond Slab Structure @ ANL/ AWA 50MV/m per 50 nC beam Our goal is to perform first WF experiment with Diamond-based DLA, test for breakdown *AWA facility can generate up to 100nC beam with σz = 2.5 mm (14 MeV) Structure is short, TM110 – based Wake is a single mode at ~ 26 GHz Q = 2800 (decay time ~35ns)

  21. Field Enhancement in the scratch beam Avoiding hot spots on diamond holder Diamonds (E6) ...scratched 50nC  250 MV/m Field is ~5 times higher beam

  22. Diamond groove SEM image Image: “BEFORE” SEM: Z. Yusof (AWA) Cut: J. Butler (NRL)

  23. High Gradient Beam Test • 72nC (σz=2.5mm) went through which is eqv. to ~ 0.3 GV/m gradient on axis for decay time τ~ 35ns. • Preliminary examination shows No evidence of breakdowns during the beam test. More examinations or additional test will be carried out. before after SEM: Sergey Antipov, Euclid and Sergey Baryshev, MSD ANL

  24. Nonlinear Ferroelectric Materials for DLA Based Accelerator Structure (DoE SBIR. Phase II project, completed)

  25. Temperature Tuning Effects in Dielectric-Based Accelerating Structure Temperature tuning 14 MHz/0K ε(E) for ferroelectric dielectric composite

  26. Nonlinear Effects at FACET DLA Lineout of the electric field on axis for different beam intensities. Red: Q=0.03 nC; Blue: Q=0.30 nC; Green: Q=3 nC (cf. Fig.21). For ease of comparison the data is scaled to Q=3.0 nC. Relative permittivity as a function of electric field strength for a composite ferroelectric dielectric DoE SBIR. Phase I, to be submitted 2012

  27. Euclid DLA Experiments planned in 2012 • Chirped electron bunch energy compensation for an x-ray light source, Phase II submitted, BES • Enhanced transformer ratio using a double triangular beam generated with the E-EX technique, Phase II submitted, HEP • THz DWA at FACET /SLAC (April 2012) • THz DWA test at ATF/BNL (fall 2012)

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