1 / 22

HZB, Berlin (Germany)

Vision for the Future: BESSY VSR A V ariable Pulse Length S torage R ing*. A. Föhlisch, A. Jankowiak, J.Knobloch, P. Kuske A. Neumann, M. Ries and G. Wüstefeld. HZB, Berlin (Germany). * G. Wüstefeld et al., IPAC 2011.

sissy
Download Presentation

HZB, Berlin (Germany)

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. Vision for the Future: BESSYVSR A Variable Pulse Length Storage Ring* A. Föhlisch, A. Jankowiak, J.Knobloch, P. Kuske A. Neumann, M. Ries and G. Wüstefeld HZB, Berlin (Germany) * G. Wüstefeld et al., IPAC 2011 ICFA Workshop on Future Light Sources, March 5-9, 2012Thomas Jefferson National Accelerator Facility, Newport News, VA (USA)

  2. BESSYVSR Outline - Motivation - Current limit of short bunches: measurements & scaling laws - Long. bunch focusing by sc-cavities - Expected results 2

  3. Motivation why short e- bunches: - time resolved, picoseconds X-ray experiments - CSR for THz experiments present situation at BESSY: - dedicated low-a shifts, s=3ps 4 blocks of 3 days per year, two operation modes: 40 mA (bursting) and 15 mA (stable) future goal: - simultaneously 15 ps & 1.5 ps bunch mode up to 100x more current in short bunches ( 10000x more THz power) 3

  4. BESSY II ring 1.7 GeV 240/p m nat. bunch length s0 = 13 ps (rms) BESSY II synchrotron radiation source storage ring parameters number of cells beam current nat. emittance nat. moment. spread 2x8 <300 mA 6 nm rad 0.7x10-3 4 rf-cavities 0.5 GHz , 1.5 MV 4

  5. Low-a optics a tool to produce and study short bunches definition of a relation s0 , a and V’ (=dV/dt=2pfrfV0): - BESSY THz-optics short bunch, low current operation 15 ps  3 ps (rms) 700 fs are proven and analyzed - MLS – ring of PTB advanced, successful low-a optics coherent THz radiation short bunch studies double-beam 5

  6. Bunch length – current relation for the BESSY II ring fixed rf voltage amplitude of 1.35 MV measurements theory user optics streak camera Stupakov & Heifets PRSTAB 5, 054402 (2002) Fourier transform spectrometer 10 THz optics THz bursting threshold P. Kuske et al., PAC 2003 bunch length s / ps (rms) - beyond bursting threshold bunches blow up in energy spread 1 s ~ Ib3/7 - rule of thumb: (s, Ib)  (2s, 5Ib) threshold from coasting beam good agreement between measurement and prediction ! 8 nC 0.1 1E-4 1E-3 1E-2 0.1 1 10 single bunch current Ib/ mA Are short bunches limited to low currents ?? 6

  7. Are short bunches limited to low currents ?? scaling law betweenaand Ipredicted by: - Vlasov-Fokker-Planck simulation - bunched beam theory (Sacherer) - and coasting beam (Landau Damping) recent papers: K.L.F. Bane, Y. Cai, and G. Stupakov, Phys. Rev. STAB 13, 104402 (2010) and Y. Cai, talk, IPAC 2011 ‘Keil-Schnell’: I~a  I~V’ for fixed s bunch length s  increasing the rf-gradient V’ x 100  a can be increased x 100  I can be increased x 100 7

  8. Y. Cai, talk, IPAC 2011 10 8 6 4 2 1 before 2003 scaled bunch current Nov. 2011 rms bunch length / ps coasting beam theory Jan. 2012 BCS: x=0.5+0.34c+dip BCS:x=0.5+0.34c+dip 1 10 100 1000 scaled single bunch current mA / MV scaled bunch length Scaling of CSR bursting threshold threshold of instability for CSR of parallel metal plates CSR bursting measurements BESSY II comparison with theory, good agreement zero current bunch length caculated from Voltage, a and long. tune Voltage range: 0.6MV – 1.8 MV 8

  9. BESSY II & sc-cavities sc-cavities for bunch shortening bunch length – current relation sc-cavities (scheme) 100x enhanced rf-gradient cavity V1,f1 cavity V2,f2 ~ 5 m straight ->J. Feikes et al, EPAC 2006 9

  10. sc-cavity # 1 & 2 (focusing) present nc-cavity (power) sc-cavity # 1 (focusing) long bunch short & long bunches Voltage / MV short bunch sum voltage rel. long. phase position / ns 0.5 GHz, 1.5 MV V’=Vxfrf= 0.75 MVGHz 1.5 GHz, 25 MV V’=Vxfrf= 37.5 MVGHz 1.75 GHz, 21.4 MV V’ = Vxfrf= 75 MVGHz Simultaneously long & short bunches - flexible fill pattern, I<300 mA - 15 ps & 1.5 ps pulses simultaneous at all beam ports - all IDs available 10

  11. MAD tracking single particle tracking, BESSY II user optics & two sc-cavities short long 40 20 0 -20 -40 40 20 0 -20 -40 4% 4% Dp/p acceptance short & long bunch momentum acceptance > +/- 4% rel. momentum / 0.001 rel. momentum / 0.001 -300 -200 -100 0 100 200 300 -300 -200 -100 0 100 200 300 rel. long. position / ps rel. long. position / ps quantum limit 2 1 0 -1 -2 2 1 0 -1 -2 short & long bunch quantum excitation & damping 10 damping times 0.7ps (rms) rel. momentum / 0.001 rel. momentum / 0.001 -20 -10 0 10 20 -20 -10 0 10 20 rel. long. position / ps rel. long. position / ps 11

  12. a0>0 a0<0 More advanced scheme: double beam chromatic orbit length: orbits of equal length L=L0: 2 solutions if a=0, a1=0 I) II) double beam scheme beam port short puls 2 sc-rf cavities & low a optics - double beam scheme combined with two sc-rf cavities long and short bunches longitudinally and transversely separated long puls alternatively: short bunches are kicked on separate orbits, like the quasi-SB operation G. Portmann, et al., Proc. 2008 BIW, Tahoe City, CA (2008). 12

  13. e- beam, beam profile image beam current: 170 mA lifetime: 10 h vertical displacement horizontal displacement 6cm More advanced scheme: double beam measurements at MLS photonbeam image (beam port exit) transverse separation of photon beams double beam can be easily produced at the MLS (low-a optics) good life time, high currents 13

  14. BERLinPro and BESSYVSR: cavity design for BESSYVSR is similar to BERLinPro, 1.3 GHz structures to be scaled to 1.5 GHz and 1.75 GHz high current beam interaction with sc cavities to be studied at BERLinPro - - BERLinPro HZB expertise BESSYVSR 14

  15. Summary long & short bunches simultaneously : - 175 long bunches, 15 ps < 300 mA - 175 short bunches, 1.5 ps (rms) - at all beam ports available - all IDs available - present transverse user optics applied expected results: present 350 bunch filling THz optics BESSYVSR 175 bunch filling user optics BESSYVSR 175 bunch filling THz optics beam parameter 15

  16. 17

  17. 17

  18. MLS measurements 21

  19. Measurements from SPEAR3 J. Corbett et al. 22

  20. Measurements from DIAMOND priv. comm. Ian Martin, DIAMOND 23

  21. 10 10 10 10 10 5 20 BESSY: sub-ps bunch diagnostics at low currents • - 870 fs, 140 nA • 700 fs, 300 nA • - 1.2 ps, 140 nA Pcoh / Pincoh 6 - Gaussian fit 5 4 3 -1 wave number / cm applied currents below bunch lengthening /deforming effects 26

  22. 11 N = 10 e N form factor e 5 10 15 20 25 5 10 15 20 25 -1 -1 wave number cm wave number cm CSR in frequency domain power spectrum analysis power spectra detector signal / a.u. Pcoherent / Pincoherent 7 7 10 gain 10 gain power spectra by Fourier transform spectroscopy BESSY II user optics, single bunch 15 mA 27

More Related