1 / 24

Beyond the RF photogun

Beyond the RF photogun. Jom Luiten Seth Brussaard Fred Kiewiet - RF photogun Benjamin Canuel Dimitri Vyuga - DC photogun Marieke de Loos - GPT Bas van der Geer - GPT Jan Botman Marnix van der Wiel. Eindhoven University of Technology Netherlands. Pancake bunches & Extreme fields.

adrina
Download Presentation

Beyond the RF photogun

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Beyond the RF photogun Jom Luiten Seth Brussaard Fred Kiewiet - RF photogun Benjamin Canuel Dimitri Vyuga - DC photogun Marieke de Loos - GPT Bas van der Geer - GPT Jan Botman Marnix van der Wiel Eindhoven University of Technology Netherlands

  2. Pancake bunches & Extreme fields 1 mm 30 m high pressure SF6 Energy: 10 MeV Peak Current: 1 kA  X-ray SASE FEL Emittance: 1  mm mrad Length: 100 fs  injector for LWFA Charge: 100 pC Target bunch: Laser-triggered spark gap: 1 GV/m during 1 ns (BNL) 50 fs UV laser pulse Keep bunches short during acceleration - no magnetic compression!

  3. Outline • Pancake bunches accelerated in uniform fields • Space charge fields in pancake bunches • Longitudinal phase space • Transverse phase space • GPT simulations • 2 MeV DC gun • DC + RF gun (2+8 MeV) • 10 MeV 1 GV/m DC gun? • Experimental progress • 2 MeV DC gun • 8 MeV, 2½ cell RF photogun

  4. L/R=0 0 MeV 2 MeV L/R=0.3 R ½ L/R=1.2 10 MeV 0 -L/2 L/2 L Z 0 -½ Space charge fields in pancake bunches bunch=100 fs, R=0.5 mm, Q=100 pC Long. field Radial field Lab frame Rest frame ½ Ez/Es 1 Er/Es 0 -L/2 L/2 -½ 0 ½ R 1 L/2 0 -L/2 0 -½ R 1 R r

  5. - - - E0 Ez Ez E0 E0 E0-Es E0-Es 0 z 0 0 z z (cf. Serafini et al., NIMA 387, 305 (1997)) Longitudinal phase space + + + Ez Peak current in surface charge regime: E0=1 GV/m, R=0.5 mm  I0=4 kA

  6. E0=1 GV/m R=0.5 mm Q=100 pC  Transverse phase space • Worst case: L/R=0 geometry • Negligible radial motion px RMS normalized emittance: x Incl. thermal emittance 0.6 n,x 0.5 ( mm mrad) 0.4 Excl. thermal emittance 0.3 0.2 0.1 0.5 1 1.5 2 Z (mm)

  7. GPT simulations: 2 MeV DC gun (1) (Van der Geer et al., PRE 65, 046501 (2002)) Evaluate bunch at z=4.5 mm Q=100 pC, R=0.5 mm, E0=1 GV/m Highly nonlinear radial fields at iris!

  8. GPT simulations: 2 MeV DC gun (2) 100 fs • Longitudinal phase space at z=4.5 mm: • FWHM bunch length 73 fs • Energy spread ~ 2% • Peak current 1.2 kA 2% 1.2 kA In agreement with simple model!

  9. GPT simulations: 2 MeV DC gun (3) • RMS normalized transverse emittance at z=4.5 mm: • n=0.4  mm mrad • nonlinear electrostatic emittance compensation! (spherical aberration cancels nonlinear space charge fields) • uniform field results in agreement with simple model.

  10. GPT simulations: DC + RF gun (1) 2 MV across 2 mm Cylindrically symmetric 2½ cell 8 MeV S-band RF booster RF Solenoid field strength 0.42-0.52 T

  11. GPT simulations: DC + RF gun (2) Hollow cathode surface (radius of curvature 3 mm) to minimize beam divergence.

  12. GPT simulations: DC + RF gun (3) • At z = 0.2 m: • n = 1.0  mm mrad • zFWHM/c = 250 fs • I = 400 A Particle trajectories for B=0.46 T

  13. GPT simulations: DC + RF gun (4)

  14. 9.6 9.4 400 200 0 -200 0 200 GPT simulations : DC + RF gun (5) Energy [MeV] Longitudinal phasespace At z=200 mm. Current [A] Position [fs]

  15. electrons trigger laser t0 t1 t2 t3 10 MeV 1GV/m DC gun? Electrons accelerated by transverse E-fields in coaxial lines Requirement: pulses with picosecond rise time!

  16. 4 mm 2 MV 1 ns 3 mm Near threshold / Tunneling ionization: Laser intensity > 1018 W/m2 High power Ti:Sapphire laser: 50 mJ / 50 fs = 1 TW plasma diameter = 0.3 mm Spark-gap plasma column E < 1GV/m 1.5 MV in less than 1 picosecond

  17. 25 mm 2 MV, 1 ns pulse Laser trigger Accelerator structure Electron bunch Spark-gaps GPT simulations: 12 MeV pulsed DC gun (1) EM field calculations: CST Microwave Studio

  18. Emittance [pi mm mrad] z [mm] Current [A] z [mm] GPT simulations: 12 MeV pulsed DC gun (2) I = 0.7 kA; n=0.6  mm mrad @ 12 MeV

  19. Experimental status: Pulsed DC acceleration Brookhaven National lab: 1 MV (5 MV?) pulses 1 GV/m @ 1 ns Under construction @ TU/e: 2.5 MV pulses 1 ns

  20. 10 MW 2.998 GHz 2½ cell 8 MeV Experimental status: RF Photogun TE10 mode TEM mode Doorknob (DESY) Movable short

  21. Superfish: f0=2998.0 MHz Q=6500 Reflection < 1% 0-mode: Intermediate mode: -mode: Measurement: Superfish 0 Measurement 1.0 0.8 -10 Reflection [dB] 0.6 |E/Emax| -20 0.4 -30 0.2 -40 0.0 0 20 40 60 80 100 120 140 160 2.992 2.994 2.996 2.998 3.000 Position [mm] Frequency [GHz]

  22. Experimental setup RF photogun

  23. First results RF photogun: Beam on phosphorescent screen: Energy : 5..6 MeV Charge : 100 .. 500 pC UV laser power : 50 J 1 mm

  24. Summary DC/RF hybrid RF photogun Operational multi stage DC?

More Related