THz Activities at PITZ PITZ studies towards an accelerator driven - PowerPoint PPT Presentation

THz Activities at PITZ PITZ studies towards an accelerator driven high power, tunable THz source for pump-probe experiments at European XFEL Prach Boonpornprasert for the PITZ team 1 st ARD Alliance Meeting DESY Hamburg, 5.9.2018

Outline of the Talk  Photo Injector Test facility at DESY, Zeuthen site (PITZ)  A proposal for Accelerator based THz source for P&P at E-XFEL  IR/THz Options at PITZ: • High-gain SASE FEL Topic of my PhD thesis • Coherent Transition Radiation (CTR) and Coherent Diffraction Radiation (CDR)  SASE FEL based on PITZ accelerator and LCLS-I undulators  LUSIA proposal ( A ttosecond SI ngle-cycle U ndulator L ight  Horizon2020 FETOPEN call) THz Activities at PITZ | Prach Boonpornprasert | 1st ARD Alliance Meeting | DESY Hamburg | 5.9.2018 Page 2 / 15

Photo Injector Test facility at DESY, Zeuthen site (PITZ) Development, test and optimization of high brightness e-sources for SC linac driven FELs + applications: • test-bed for FEL injectors: FLASH, the European XFEL (conditioning, characterization and optimization of gun cavities and photo injector subsystems, e.g. photocathode laser) • high brightness  small transverse emittance (projected and slice) • further studies  e.g. cathodes: dark current, photoemission, QE, thermal emittance , …  applications like THz , plasma acceleration, UED, … <7 MeV <25 MeV Total length of ~22 m but can be reduced significantly if some diagnostics parts are removed. THz Activities at PITZ | Prach Boonpornprasert | 1st ARD Alliance Meeting | DESY Hamburg | 5.9.2018 Page 3 / 15

PITZ “engine”: RF -Gun and Photocathode Laser Highlights of the facility Photocathode laser(s) (UV) RF gun Default laser system Institute of (Max-Born-Institute, Berlin) Applied Physics • L-band (1.3 GHz) 1.6-cell copper cavity Gaussian: of the Russian • Ecath>~60MV/m  7MeV/c e-beams Academy of FWHM FWHM • 650us x 10Hz  up to 45 kW av. RF power Sciences ~7 ps ~ 2 ps New laser system • Cs 2 Te PC (QE~5-10%)  up to 5nC/bunch • LLRF control for amp&phase stability FWHM FWHM • Solenoids for emittance compensation ~ 11 ps ~ 17 ps 3D ellipsoidal Pulse shapers: Multicrystal birefringent pulse shaper • Spatial Light Modulator containing 13 crystals (SLM) based Pulse Train Time Structure : • Upgrade with Volume Bragg Grating (VBG) PITZ and EXFEL trains with up to 600 ( 2700 ) laser pulses Oscillator upgrade – 600  s Pharos-20W-1MHz frontend t Flattop Pulse length 0.25-10ps+ 100 ms Different lasers Cathode laser pulse: temporal profile t  Possible to use OSS signal (UV) PITZ  EU-XFEL  t = 1  s FWHM = 25 ps simultaneously (222ns) edge 10-90 edge 10-90 “Same hardware, same time structure” ~ 2 ps ~ 2.2 ps  various THz options birefringent shaper, 13 crystals THz Activities at PITZ | Prach Boonpornprasert | 1st ARD Alliance Meeting | DESY Hamburg | 5.9.2018 Page 4 / 15

Accelerator based tunable IR/THz source for P&P at E-XFEL PITZ can be used as a prototype! Pump X-ray PITZ-like accelerator based XFEL (~3.4 km) & THz source (~20 m) Transverse profile probe THz correction E.A. Schneidmiller, M.V. Yurkov, (DESY, Hamburg), M. Krasilnikov, F. Stephan, (DESY, Zeuthen), “ Tunabale IR/THz source for pump probe experiments at the E uropean XFEL”, Contribution to FEL 2012, Nara, Japan, August 2012 • Accelerator based IR/THz source meets all requirements for pump-probe experiments (e.g., the same pulse train structure!). • Construction of a radiation shielded annex (reduced copy of PITZ facility) is possible close to user experiments at the European XFEL. • Prototype of the accelerator already exists.  PITZ facility at DESY in Zeuthen. Photo by Dirk Noelle, 06.06.2013 XFEL (experimental hall) XFEL ( photon beamline tunnel) PITZ  PITZ can be used for proof of principle and optimization! THz Activities at PITZ | Prach Boonpornprasert | 1st ARD Alliance Meeting | DESY Hamburg | 5.9.2018 Page 5 / 15

IR/THz Options at PITZ: High-gain SASE FEL Case studies of generating THz radiation by PITZ electron beam Photocathode Booster (Linac) APPLEII Undulator RF Gun Deflecting Cavity Quadrupole magnet Proposal extension for SASE FEL Dipole magnet HEDA2 Screen 0 m PITZ beamline layout extension for simulation studies PITZ Highlights: ► SASE FEL for λ rad ≤ 100 µm (f ≥ 3 THz) • Pulse train structure • High charge feasibility (4 nC) • Advanced photocathode laser shaping • E-beam diagnostics Current PITZ “boundary conditions”: • 22-25 MeV/c max • Available tunnel annex • No bunch compressor • … • No undulator (yet…) • … THz Activities at PITZ | Prach Boonpornprasert | 1st ARD Alliance Meeting | DESY Hamburg | 5.9.2018 Page 6 / 15

THz SASE FEL at PITZ Undulator and beam parameter space Conditions : λ rad = 20 µm λ rad of 20 – 100 µm λ rad = 100 µm Example: APPLE- II Undulator* Max P z ~ 22 MeV/c Radiation wavelength gap g ≥ 10 mm 𝜇 𝑣 2 𝜇 𝑠𝑏𝑒 = 2𝛿 2 1 + 𝐿 𝑠𝑛𝑡 𝐿 𝑠𝑛𝑡 = 0.66 ∙ 𝐶 0 𝑈 ∙ 𝜇 𝑣 𝑑𝑛 Selections : 2 −4.46 𝑕 𝜇 𝑣 +0.43 𝑕 λ u of 40 mm 𝜇 𝑣 𝐶 0 = 1.54𝑓 22 MeV/c for 20 µm * Conceptual Design Report ST/F-TN-07/12, Fermi@Elettra, 2007 15 MeV/c for 100 µm FEL Parameter Space with FAST code ( λ rad = 100 µm) Saturation power [W] Saturation length [cm] SASE FEL simulations assuming: • Helical undulator with period length of 40 mm 400 2E+08 400 • Electron beam with 15 MeV/c momentum, 300 4 nC bunch charge, ~2 mm rms bunch length 1E+08 I [A] I [A] Preliminary conclusions: 7E+07 • Transverse normalized emittance ε n has 200 200 5E+07 almost no impact on saturation power Courtesy 600 3E+07 400 M. Yurkov • Higher ε n  lower saturation length 500 • Beam peak current (charge)  most impact 2 4 6 8 10 12 14 16 18 20 2 4 6 8 10 12 14 16 18 20  n [mm-mrad]  n [mm-mrad] THz Activities at PITZ | Prach Boonpornprasert | 1st ARD Alliance Meeting | DESY Hamburg | 5.9.2018 Page 7 / 15

THz SASE FEL: Beam Dynamics Simulations and Experiments λ rad = 100 µm (3 THz) Setup: 4nC  I peak ~200A, ~15MeV/c, FEL pulse energy FEL radiation pulse at undulator exit l u =40 mm, K=1.8, L u =5m (average and rms fluct.) temporal profiles spectral profiles Start-to-end: ASTRA  GENESIS1.3 • Photocathode laser:  5mm, flattop 2/20\2ps • Gun and booster phases and main solenoid 2.7 mJ optimized for high I peak and small d E 8.4% E-beam from experiment  GENESIS1.3 • Photocathode laser:  3.7mm, Gaussian 11ps FHWM • Phase spaces  from measurements X- X’ Y- Y’ 1.7 mJ 10.2% 11.05 mm mrad 7.13 mm mrad t-P z THz Activities at PITZ | Prach Boonpornprasert | 1st ARD Alliance Meeting | DESY Hamburg | 5.9.2018 Page 8 / 15

THz SASE FEL: Comparison with laser-based THz sources PITZ-like accelerator TELBE@1nC can produce ~mJ THz pulses ( l rad =20-100  m) TELBE@100pC matching time structure ~mJ THz pulse @ MHz train Laser based THz to XFEL X-ray pulses. (SASE simulation with PITZ pulse energy is limited beam, ~4 nC, I peak ~200A) at high repetition rate P.Boonpornprasert, et al. MOP055, FEL2014, Basel, Switzerland Plot based on talk of M. Gensch “Follow up on THz Radiation” at ARD -ST3 Annual Workshop 19-21.07.2017,DESY, Zeuthen and paper B. Green ,. et al. High-Field High-Repetition-Rate Sources for the Coherent THz Control of Matter. Sci. Rep. 6, 22256; doi: 10.1038/srep22256 (2016). But still SASE (starting from the shot noise) ... ?How to improve stability (CEP= carrier envelope phase)? THz Activities at PITZ | Prach Boonpornprasert | 1st ARD Alliance Meeting | DESY Hamburg | 5.9.2018 Page 9 / 15

Options to improve THz radiation stability Pre-bunching  “Seeding” Courtesy I. Zagorodnov ∆ 𝐹 [mJ] • Photocathode laser pulse temporal modulation 0.45 𝐹 0 = 8 MeV • Using IR laser, modulator and BC for E or d E modulations 0.4 𝑔 ≈ 0.33 THz 0.35 • Using CDR from short seeding bunch 0.3 0.25 50 • Using corrugated structures 40 𝐹 0 = 20 MeV 30 0.2 20 10 𝑔 ≈ 0.3 THz 0 -5 0 5 • Using Dielectric Lined Waveguides - DLW (first experiments) 0.15 0.1 0.05 0 Measured e-beam current profile 0 0.5 1 1.5 2 𝑨 [m] without (blue trace) with DLW (red trace), l =1.03 mm; The peaks are consistent with the wavelength of the structure 3.3 ps. Measured Longitudinal phase space Future topics for PhD research at PITZ In collaboration with CFEL (F. Lemery) and APC FNAL (P. Piot) F. Lemery et al., Experimental demonstration of ballistic bunching with dielectric-lined waveguides at PITZ, IPAC 2017, WEPAB122 THz Activities at PITZ | Prach Boonpornprasert | 1st ARD Alliance Meeting | DESY Hamburg | 5.9.2018 Page 10 / 15