Advanced Accelerator R&D: Flat Beam Transform & Emittance Exchange

1. Advanced Accelerator R&D: Flat Beam Transform & Emittance Exchange Kwang-Je Kim ANL & U of C June 27, 2008 ANL-UChicago-FNAL Collaboration Meeting at Fermilab

2. Emittance Exchange and Flat Beam Transform • Emittance Exchange (EEX): Complete exchange between x- and z-phase spaces: (ex,ez) (ez,ex) • Flat Beam Transform (FBT): Transform a round photo-cathode beam to a flat beam with a desired emittance ratio in (x,y) phase space • Applications often require a combination of these manipulations

3. Flat Beam Transform • Produce angular-momentum dominated beam and remove correlation • R. Brinkmann, Y. Derbenev, and K. Floettmann (1999, 2001) • Experimentally demonstrated at A0 • D. Edwards, et. al., emittance ratio of 40 at Fermilab A0 (Linac2000, PAC2001) • Yin-e Sun, U of C thesis (2005) • Ph. Piot, Y.-e. Sun, and KJK, emittance ratio>100 (PRSTAB 9, 031001, 2006)

4. 3.9 GHz TM110 D1 Initial e- bunch ex < ez D2 D3 final e- bunch D4 ex > ez Emittance Exchange Scheme • First dogleg provides dispersion at deflecting cavity. • The cavity reduces the momentum spread of the beam and gives a shear deflection to the beam. • The second dogleg finishes the exchange. • The scheme improves on the previous approximate scheme by Cornacchia and Emma in which the second dog-leg is reversed. Diagram by Tim Koeth.

5. Improve HG X-Ray FEL Performance(P. Emma, Z. Huang, P. Piot, KJK) • Electron bunch emittance of current X-ray FEL projects is (ex, ey)=(1, 1) mmwith Q=1 nC • This is about 10 times larger than ideal (to match the x-ray beam phase space) • Due to small energy spread, can make ez=0.1 mm • FBT: (ex, ey, ez)=(10, 0.1, 0.1) mm • Exchange x & z  (ex, ey, ez)=(0.1, 0.1, 10) mm Q=30 pC, sz=10 fs • Higher gain • Lower K • Lower E-energy

6. To Obviate Electron Damping Ring from ILC • Emittances of ILC electron bunches are (ex, ey, ez)=(8, 0.02, 3000) mm • These bunches are produced by a 5 GeV, 6 km damping ring • Theemittance eT= (ex ey)1/2 is too small for photocathode • A possibility: (1, 1, 8)(50,0.02, 8)(8, 0.02,50) (Ph. Piot)

7. EEX Demonstration Experiment • FNAL/A0 • Initiated by Helen Edwards, December, 2006, and T. Koeth engaged • (ex, ey, ez): (6, 6, 120)(120, 6, 6)mm, Q=1 nC • Use CKM cavity design and existing RF power • Exciting dataTim will be able to graduate! • ANL/AWA-NIU-TsingHua U • Argone Acclerator Institute activity, funded by LDRD • (ex, ey, ez): (10,3, 3)(3,3,10)mm , Q=0.1 nC • NIU (Marwan Rihauoi, GS) and Tsinghua U (defl. cavity) • To be finished by 2010-2011 • ANL-FNAL collaboration • Bi-(Tri-) weekly meetings and common web page • Especially productive in exchanging ideas on diagnostics

8. A0 People • Helen Edwards – The Boss • Don Edwards • Ray Fliller (The Manager) • Yin-e Sun (Recently from ANL) • Jinhao Ruan – Laser, All things optical • Jamie Santucci – Operations • Tim Koeth – Rutgers Ph.D. Student • Artur Paytan – Yerevan U. Ph.D. Student • Mike Davidsaver – UIUC staff, controls • Grigory Kazakevich – Guest Scientist, OTRI • Manfred Wendt – Instrumentation, BPMs • Randy Thurman-Keup – Instrumentation, Interferometer • Vic Scarpine – Instrumentation, OTR and cameras • Alex Lumpkin – Instrumentation, Radiation Diagnostics (On leave from ANL) • Ron Rechenmacher – CD, controls • Lucciano Piccoli – CD, controls • Gustavo Cancelo – CD, Low Level RF • Wade Muranyi – Mechanical Support, Lead Tech. • Many Others from AD/RF, AD/MS

9. EEX at FNAL-A0 A0 Photoinjector Layout with EEX beamline Vertical Spectrometer Dipoles 3.9 GHz TM110 (deflecting mode) Cavity Use a 3.9GHz, 5 cell copper cavity based on the CKM SRF deflecting cavity cooled with liquid N2. An 80 kW klystron is available.

10. First Deflected Beam by a CKM type Cavity Operating phase for exchange

11. Recent Measurements at A0( Tim Koeth) • Change the input momentum (0.70% Increments) • Measure the vertical offset after exchange line spectrometer • Increase Deflecting Cavity Strength As the cavity strength is increased, the momentum change after the exchange line is reduced TM110 cavity strength, ko OFF 73% 90% 100% 105% Vertical Beam Position after Vertical Spectrometer (mm) Intro dp from 9-Cell Vary cavity strength record vertical BPM reading

12. Diagnostics for A0 EEX • Prior to the exchange : • OTR screens for beam spot size measurement • Slits for uncorrelated beam divergence measurement • Combined with above gives a transverse emittance measurement • Horizontally bending spectrometer for energy and energy spread measurement • Streak Camera for bunch length • After the exchange: • Same diagnostics for measuring transverse emittance • Vertically bending spectrometer for momentum spread • Allows us to decouple the momentum spread measurement from any residual horizontal dispersion from the doglegs • Martin-Puplett interferometer for bunch length measurement • Also the streak camera (> 1 ps)

13. Recent Measurements at A0 ( cont’d) A preliminary measurements of several of EEX matrix elements: Onto an attempt to directly measure the exchange: Bunch length measurement with a streak camera. (A. Lumpkin) TM110 Cavity OFF TM110 Cavity ON Output energy spread measurement Resulting emittances values: Close to CSR increased emittace (R. Fliller)

14. ANL-NIU-TsingHua Collaboration For EEX • AWA • Wei Gai (Leader) • Sergey Antipov • Manoel Conde • Felipe Franchini (Tech) • Feng Gao (Student) • Chunguang Jing ( Euclid supported) • Richard Konecny (Super Tech) • Wanming Liu • John Power • Zikri Yusof • APS • Kathy Harkay, (Yin-e Sun), (Alex Lumpkin) • NIU • Philippe Piot • Marwan Rihaoui (GS) • TsingHua • Cavity fabrication

15. Emittance Exchange (EEX) at the Argonne Wakefield Accelerator AWA photoinjector: Q=100pC; K= 12 MeV; Laser: sx=sy=2.5 mm; sz=1.15 ps; Photoinjector TQ1,TQ2,TQ3 Gun Linac Emittance Exchanger YAG1 YAG2 GV GV ICT1 TM110 ex=10 mm ey=3 mm ez= 3 mm Overall Goal: exchange small ez for largeex withsmall Qbunches ex= 3 mm ey=3 mm ez= 10 mm EEX beamline: Q=15 deg; hx = 25 cm; k=4 N.B.  Exchanged many idea with Fermilab Emittance Exchange Group

16. Diagnostics for AWA EEX • ANL diagnostics will be more challenging than A0 due to small longitudinal emittance, thus short bunch length • Spot size • OTR screens for beam spot size measurement (same as A0) • Beam divergence • pepper pot, (allows us to look at correlations, including x-y for flat beam) • Energy and energy spread before and after EEX: • Spectrometer (same as A0) • Bunch length • zero-crossing method with linac, deflecting cavity (short bunch) • Exploring EOS ( help from Jinhao Ruan) • In addition: • Time-of-flight monitor: stripline-based phase detection • Longitudinal phase space: linac phase scan or deflecting cavity + spectrometer

17. Deflector Cavity • Trajectory offset in a deflector cavity • D. Edwards (theory), J. Power (simulation) • Developed a theory to eliminate by adjust cavity parameters • Deflector cavity arrives from Tsinghua U (soon) • Installation to AWA beamline (Fall, 2008) • Improved Longitudinal Emit Measurement with deflector cavity + Spectrometer Cavity fabricated at Tsinghua U in Beijing