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Overview of Beam Physics Department

Overview of Beam Physics Department. Yunhai Cai ARD Meeting October 26, 2010. Cai, Yunhai [Department Head] (Ng, Cho-Kuen) [ Deputy]. (Cai, Yunhai) [Group Leader, Optics ] Nosochkov, Yuri Wang, Min-Huey Yan, Yiton. Stupakov, Gennady [Group Leader, Collective Effects ] Bane, Karl

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Overview of Beam Physics Department

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  1. Overview of Beam Physics Department Yunhai Cai ARD Meeting October 26, 2010

  2. Cai, Yunhai [Department Head] (Ng, Cho-Kuen) [Deputy] (Cai, Yunhai) [Group Leader, Optics] Nosochkov, Yuri Wang, Min-Huey Yan, Yiton Stupakov, Gennady [Group Leader, Collective Effects] Bane, Karl Chao, Alexander Jiao, Yi +Ratner, Daniel Novokhatski, Sasha Wang, Lanfa *Warnock, Robert Xiang, Dao Huang, Zhirong [Group Leader, FELPhysics] Ding, Yuantao Fawley, Bill Ruth, Ron +Baxevanis, Panagiotis *Herrmannsfeildt, W. Lutman, Alberto Wu, Huhao Ko, Kwok [Group Leader, ACD] Candel, Arno Ge, Lixin Lee, Ki Hwan Li, Zenghai Ng, Cho-Kuen Rawat, Vineet Schussman, Greg Xiao, Liling Beam Physics Department (October 2010), +students, *associates

  3. Core Competencies • Lattice design and single-particle beam dynamics • Optics for LCLS-II, FACET, ATF2, SuperB, and PEP-X • Accelerator modeling and improvement, LCLS, ATF2 • Nonlinear dynamics and resonances • Wakefield and impedance, collective effects and instabilities of intensely charged beam • Impedance at very high frequency • Coherent synchrotron radiation and its dynamical effects • Physics related to ultra-short bunches • Beam-beam effects in the colliders • Simulation, parallel computing, and computational science • Suite of electromagnetic software: ACE3P (Omega3P, T3P, …) • Lie-algebra-based linear and nonlinear analysis codes: LEGO and Zlib • PIC simulation of beam-beam interaction and luminosity: BBI • Nonlinear Vlasov solver for microwave instability: VFP • Theory of free-electron laser • LCLS upgrades, seeding, polarization, partial lasing in storage ring • Teach at Stanford University and US Particle Accelerator School • Single-particle dynamics, FEL physics, impedance and instabilities

  4. Funding Profile in FY2011 • HEP projects: ILC, LARP, SciDAC • Others: Spear3, Echo-7, PEP-X, …

  5. Research in Accelerator Science Mission • Charged particle optics and accelerator design • Analytical calculation of impedance and collective instabilities • Electromagnetic computation and RF design • FEL physics and seeding schemes Highlights (in this year) • Published 55 papers (12 on peer-reviewed journals) • Taught two courses at USPAS • Served on review committees, reviewed proposals, refereed journal papers

  6. CSR Wakefield and Impedance in Free Space Wakefield due to CSR is given For z>0. It vanishes when z<0 (force is on the particle ahead). The Impedance is derived by Falten and Laslett where r is the bending radius.

  7. FACET Beam Simulations with CSR Short bunch length in Sector-20 (60 to 20 mm) results in strong CSR effects leading to growth of horizontal beam size at IP. ELEGANT simulations: sx = 11.6 mm with ISR , sx = 15.0 mm with ISR and CSR, E = 23 GeV, N = 2∙1010 part/bunch Sector-20 e+ (upgrade) Beam profile and beam size at IP Z-d d Final Focus Experimental area X-Y Y IP e- Dump X Z Gaussian fit X-Y size: sx = 15.0 mm sy = 7.1 mm Gaussian fit bunch length: sz = 18.6 mm

  8. Horizontal emittance after BC1 vs. RF phase Elegant Meas-1 Meas-2 CSR energy loss after BC1 measured with BPM Simulation Simulation operating point operating point CSR Studies at LCLS • Studied CSR effects on beam quality at BC1 and BC2; • Measured energy loss and emittance growth due to CSR, compared with 1D and 3D model; • 1D model results are in good agreement with data, as shown in the following BC1 examples. K. Bane, et al. PRSTAB 12 (2009) 030704

  9. Theory: Stupakov, Kotelnikov, PRSTAB 12 (2009) 104401 Steady state wakefields (black) in the toroid for the aspect ratio A = 3 and various values of b: a) b = 4 cm, b) b = 2 cm, c) b = 1 cm, and d) b = 0.5 cm. Red-parallel plates model with gap b, blue-free space. CSR Wakefields in Bend Magnets A computer code was written which calculates the CSR wakefields for a bend of finite length with account of the transients at the entrance to and the exit from the magnet. The code was used for simulations of the CSR wake in PEP-X and SuperKEK-B. The CSR threshold as a function of the wavelength for SuperKEK-B. The blue solid, red dashed and green dashed-dotted lines are results of CSR impedances by A & Y formulae, our code, and free space model, respectively. D. Zhou et al. IPAC, 2010.

  10. Threshold of Microwave Instability Phase space of the microwave instability. Scaling property of CSR threshold A simple scaling law based on the shielding parameter and normalized current was found. The dimensionless parameters are Scsr=Inr1/3/sz4/3 and P = r1/2sz/h3/2, where In=reNb/2pnsgsd. Bane, Cai, Stupakov, Phys. Rev. ST Accel. Beams 13, (2010) 104402.

  11. nominal (6 mJ) Laser heater OFF Heater OFF 0.01% at 14 GeV with compression factor 90 1.5 Å 0.4-mm emit 0.5-mm emit Heater OFF Heater ON Laser Heater Improves FEL Power & Gain Length Heater is effective, and µ-bunching is under some control Z. Huang, FEL2009

  12. SIMULATED FEL PULSES 1.5 Å, 3.61011 photons Ipk = 4.8 kA ge 0.4 µm Simulation at 1.5 Å based on measured injector & linac beam & Elegant tracking,with CSR, at 20 pC. 15 Å, 2.41011 photons, Ipk = 2.6 kA, ge 0.4 µm 1.2 fs time-slicing at 20 pC Simulation at 15 Å based on measured injector & linac beam & Elegant tracking,with CSR & 20 pC. Measurements and Simulations for 20-pC bunch MEASURED SLICE EMITTANCE 135 MeV 20 pC Extremely short electron & x-ray pulses possible… gex = 0.14 µm Y. Ding et al., PRL 102 254801, June 2009

  13. Single-Shot Method for Measuring fsBunches To high-resolution energy spectrometer Slightly adjust BC2 R56 add a diagnostic chicane R56’ BC2 4.3 GeV Run L3 at zero crossing (-90 deg) h3 L2 (2) Over-compression Zero-crossing sd d z =0 • Diagnostic chicane can be part of BC2 sz • Final energy spread/profile corresponds to short bunch length/profile • Wakefield of long linac must be taken into account Z. Huang, K. Bane, Y. Ding, P. Emma, PRST-AB, 2010

  14. Preliminary Results of Ultrashort LCLS bunch measured with A-line spectrometer • Use A-line high-dispersion screen (PR18) as spectrometer • Use LCLS low-charge (10-40 pC), highly compressed electron bunches • Preliminary measurements show the technique can measure bunch length down to ~1 mm and observe double-horn current profile • Improvement to PR18 resolution is planned Preliminary 40 pC Under compression Double-horn observed on PR18 (A-line)

  15. Parallel Electromagnetic Code Suite ACE3P • Meshing - CUBIT for building CAD models and generating finite-element meshes. http://cubit.sandia.gov. • Modeling and Simulation – SLAC’s suite of conformal, higher-order, C++/MPI based parallel finite-element electromagnetic codes • https://slacportal.slac.stanford.edu/sites/ard_public/bpd/acd/Pages/Default.aspx • Postprocessing- ParaView to visualize unstructured meshes & particle/field data. http://www.paraview.org/. ACE3P (Advanced Computational Electromagnetics 3P) Frequency Domain: Omega3P – Eigensolver (damping) S3P – S-Parameter Time Domain:T3P – Wakefields and Transients Particle Tracking: Track3P – Multipacting and Dark Current EM Particle-in-cell:Pic3P – RF gun (self-consistent) Multiphysics: TEM3P –Thermal, RF and Structural Goal is the Virtual Prototyping of accelerator structures

  16. T3P – Short Bunch Wakefields in ERL Energy Recovery Linac Bunch length = 0.6 mm Vacuum chamber transition model Beam direction Longitudinalwakefield Scalability on jaguar Loss factor = 0.413 V/pC

  17. CEBAF BBU - Solving the Inverse Problem High Q modes CEBAF 12-GeV upgrade – • Beam breakup (BBU) observed at beam currents well below design threshold. • Used measured RF parameters such as f, Qext, and field profile as inputs • Solutions to the inverse problem identified the main cause of the BBU instability: Cavity is 8 mm shorter – predicted and confirmed later from measurements • The fields of the 3 abnormally high Q modes are shifted away from the coupler • Showed that experimental diagnosis, advanced computing and applied math worked together to solve a real world problem as intended by SciDAC Ideal Deformed Omega3P Field profiles in deformed cavity HOM coupler

  18. T3P – CLIC Two-Beam Accelerator Compact Linear Collider two-beam accelerator unit PETS Dielectric absorbers (SiC) 10 hours, 12000 cores on jaguar TD24 PETS +TD24

  19. G. Stupakov, Phys. Rev. Lett. 102 (2009) 074801.

  20. The Echo-7 experiment at NLCTA existing New echo beam line since Oct, 2009 Current NLCTA beam line • EEHG is proposed in late 2008 at SLAC and first demonstrated in 2010 at SLAC • Echo-7 is collaborated among BP, TF, AARD within ARD • About one year from inception to execution & demonstration

  21. First Demonstration of the EEHG Principle (a) 1590 nm seed laser on 1590 nm laser on H3 HGHG H4 (b) 795 nm laser on H2 795 nm laser on H2 HGHG Both lasers on H4 H2 H3 HGHG + EEHG E1 E3 E2 350 400 450 500 550 600 Radiation wavelength (nm) The experiment confirms the feasibility of preservation of the phase space correlations D. Xiang, et al., Phys. Rev. Lett. 105 (2010) 114801.

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