1 / 37

Coherent Synchrotron Radiation Studies at the Advanced Light Source and the IKNO proposal

INFN - LNF, Frascati, Italy, July 10, 2008. Coherent Synchrotron Radiation Studies at the Advanced Light Source and the IKNO proposal. Fernando Sannibale. A Team Work. CSR Studies at the ALS and IKNO. F.Sannibale. INFN - LNF, Frascati, Italy, July 10, 2008.

hal
Download Presentation

Coherent Synchrotron Radiation Studies at the Advanced Light Source and the IKNO proposal

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. INFN - LNF, Frascati, Italy, July 10, 2008 Coherent Synchrotron Radiation Studies at the Advanced Light Source and the IKNO proposal Fernando Sannibale

  2. A Team Work CSR Studies at the ALS and IKNO. F.Sannibale INFN - LNF, Frascati, Italy, July 10, 2008 AFRD (ALS Acc. Physics and CBP):J. M. Byrd, D. S. Robin, F. Sannibale, A. Zholents, M. Zolotorev. ALS:Z. Hao, M. C. Martin. MSD:R. W. Schoenlein. Collaborations:BESSY, DLR (Berlin), SLAC Important contributions: M. Abo-Bakr, J. Feikes, E. Forest, S. Heifets, K. Holldack, H. W. Hubers, P. Kuske, W. Leemans, A. Loftsdottir, B. Marcelis, J. Murphy, T. Scarvie, C. Steier, G. Stupakov, M. Venturini, R. Warnock, G. Wustefeld, ... Present IKNO Collaboration:P. Innocenzi, A. Marcelli, F. Sannibale.

  3. Why Studying CSR? CSR Studies at the ALS and IKNO. F.Sannibale INFN - LNF, Frascati, Italy, July 10, 2008 Coherent Synchrotron Radiation (CSR) has been matter of great interest and study in the last years: • As something to carefully avoid or at least control in every short bunch high charge accelerator where CSR can jeopardize the performances (linear colliders, short pulses synchrotron radiation sources, damping rings, ...); • As a powerful diagnostic for bunch compressors in free electron lasers (FEL) (FLASH, LCLS, FERMI, …); • But also as a ‘dream’ for potential revolutionary synchrotron radiation (SR) source in the THz frequency range.

  4. The “Terahertz Gap” CSR Studies at the ALS and IKNO. F.Sannibale Hz INFN - LNF, Frascati, Italy, July 10, 2008 Scarcity of broadband powerful source in such a region of the spectrum 1 THz = 4.1 meV = 33 cm-1 = 300 mm THz Science: collective excitations, protein motions & dynamics, superconductor gaps, magnetic resonances, terabit wireless, medical imaging, security screening, detecting explosives & bio agents … “DOE-NSF-NIH Workshop on Opportunities in THz Science” February 12-14, 2004 http://www.science.doe.gov/bes/reports/abstracts.html#THz

  5. Why CSR from Storage Rings CSR Studies at the ALS and IKNO. F.Sannibale INFN - LNF, Frascati, Italy, July 10, 2008 • High Stability • Many users capability • Multicolor experiments capability • Capability of "exotic" experiments (femtoslicing, stacking, ...) • Non interceptive radiation processes are required. • Synchrotron and edge radiation most efficient

  6. A Multi-Year Effort CSR Studies at the ALS and IKNO. F.Sannibale INFN - LNF, Frascati, Italy, July 10, 2008 2002: The microbunching instability (MBI): First experimental proof. (J.M.Byrd et al., PRL 89, 224801, 2002.) 2003-2004: Stable CSR in storage rings: Development of a model accounting for experimental observations. (F. Sannibale et al., PRL 93, 094801, 2004.) 2004-2005: CSR from “femtoslicing” experiment: First experimental data and characterization. (J.M.Byrd et al., PRL 96, 164801, 2006.) 2004-2006: Laser seeding of the MBI: First experimental observation and model for the phenomenon. (J.M.Byrd et al, PRL 97, 074802, 2006.)

  7. CSR Basic CSR Studies at the ALS and IKNO. F.Sannibale Single particle power spectrum for the radiating process under consideration (including shielding effects) Synchrotron radiation from a bend CSR for: Normalized Bunch Longitudinal Distribution INFN - LNF, Frascati, Italy, July 10, 2008 The power spectrum of the radiation from a bunch with N particles is given by: The CSR factor g(w) determines the high frequency cutoff for CSR, while the vacuum chamber (shielding) defines the low frequency one.

  8. CSR Form Factorvs. Bunch Length CSR Studies at the ALS and IKNO. F.Sannibale 1.0 ps - Gaussian Distribution 1.5 ps - Gaussian Distribution 2.0 ps - Gaussian Distribution Very sensitive knob! INFN - LNF, Frascati, Italy, July 10, 2008 To extend the CSR spectrum towards higher frequencies the bunches must be shortened.

  9. CSR Form Factor vs.Longitudinal Bunch Distribution CSR Studies at the ALS and IKNO. F.Sannibale INFN - LNF, Frascati, Italy, July 10, 2008 To extend the CSR spectrum towards higher frequencies: the ‘saw-tooth’ distribution is the "best".

  10. The “Cocktail” for a Good THz Source CSR Studies at the ALS and IKNO. F.Sannibale INFN - LNF, Frascati, Italy, July 10, 2008 Extend the vacuum chamber cutoff towards wavelengths as long as possible. Shorten the bunches as much as possible. Find a mechanism for generating sharp edged distributions at equilibrium (saw-tooth like possibly). And of course, put as much particles as possible in the bunch. Unfortunately, in this description a major player is missing. We will see that for short bunches (~ ps) the situation becomes a little bit more complicate...

  11. The Synchrotron Radiation Wake CSR Studies at the ALS and IKNO. F.Sannibale SR Emission Cone e- Ef r bunch distribution Back Front SR wake accelerates bunch front INFN - LNF, Frascati, Italy, July 10, 2008 Because of the curved trajectory of the beam, the photons radiated from particles in the tail of the bunch catch up with the particles in the head. The curved trajectory also allows for the electric field of these photons to have a component parallel to the direction of the motion of the particles in the head, and therefore to change their energy.

  12. The Analytical Expression for the SR Wakefield CSR Studies at the ALS and IKNO. F.Sannibale ~ Free Space Infinite parallel plate shield Coulomb Tail Head Tail Head INFN - LNF, Frascati, Italy, July 10, 2008 J.B. Murphy, S. Krinsky, R. Gluckstern , Particle Accelerators 57, 9 (1997) Typical region of interest

  13. Increasing the Current per Bunch. CSR Studies at the ALS and IKNO. F.Sannibale Simulated instability showing the microbunching. Venturini, WarnocK SLAC INFN - LNF, Frascati, Italy, July 10, 2008 The bunch distribution in a real ring is never completely smooth and shows a modulated profile that changes randomly with time (noise). These micro-structures have characteristic length << than the bunch length and radiate CSR. The CSR wakefield modulates the energy of the neighbor particles that start to move inside the bunch due to the accelerator longitudinal dispersion. Some particles move in the direction that increases the radiating micro-structure, and thus increasing the CSR intensity and creating a gain mechanism. Above a current threshold, this gain becomes large enough to sustain the micro-bunching process against the decoherence effect due to the energy spread, and to generate an exponential growth of the micro-structure amplitude (up to saturation in the non linear regime of the instability). Such an instability, often referred as the micro-bunching instability (MBI), is nothing else that a SASE process in the THz regime. The MBI, for the case of storage rings, was predicted by Sam Heifets and Gennady Stupakov (PRST-AB 5, 054402, 2002) and simulated by Marco Venturini and Bob Warnock(PRL 89, 224802, 2002)

  14. Terahertz CSR Bursts CSR Studies at the ALS and IKNO. F.Sannibale 10 mA ALS Data 29 mA Bolometer signal (V) 40 mA Time (msec) A. Anderson et al.:, Opt. Eng. 39, 3099, (2000). G.L. Carr et al.:, NIMA 463, 387, (2001). M. Abo-Bakr et al.:, EPAC2000 Proceedings. ... INFN - LNF, Frascati, Italy, July 10, 2008 According to what said before, the presence of the micro-bunching instability should be associated with the emission of random "burst" of CSR. In many electron storage rings around the world, strong random pulses (“bursts”) of CSR in the THz frequency range were observed for high single bunch current.

  15. CSR Instability ExperimentalVerification CSR Studies at the ALS and IKNO. F.Sannibale wavelength wavelength Model predictions The MBI dramatically limits the maximum stable single bunch current in the short bunch regime! Burst threshold (mA) J. Byrd, et. al. PRL 89, 224801, (2002). Energy (GeV) INFN - LNF, Frascati, Italy, July 10, 2008 Experiments at the ALS provided the experimental confirmation that the THz CSR bursts were associated with the MBI. The instability thresholds predicted by the Heifets-Stupakov model for the instability were in agreement with the measured thresholds The beam becomes unstable if the single bunch current is larger than (SI Units):

  16. Below the MBI Threshold CSR Studies at the ALS and IKNO. F.Sannibale Head Tail Free Space SR Wake INFN - LNF, Frascati, Italy, July 10, 2008 Below the MBI threshold, the strongly nonlinear SR wake generates a distortion of the parabolic potential well due to the RF cavity, and the bunch assumes non-Gaussian equilibrium distributions. The current distribution I(s) can be calculated by the Haissinski Equation: where S(s) is the Step Function Wake and szo is the natural bunch length. The free space SR wake generates the saw-tooth like distributions we were looking for! (Bane, Krinsky and Murphy AIP Proc. 367, 1995)

  17. Vacuum Chamber Shielding CSR Studies at the ALS and IKNO. F.Sannibale Shielded SR Wake Head Tail Free Space SR Wake Tail Head INFN - LNF, Frascati, Italy, July 10, 2008 The vacuum chamber shielding reduces the CSR emitted power In a CSR optimized source the shielding effects must be minimized: J.B. Murphy, S. Krinsky, R. Gluckstern , Particle Accel. 57, 9 (1997)

  18. Other Wakefields CSR Studies at the ALS and IKNO. F.Sannibale INFN - LNF, Frascati, Italy, July 10, 2008 Other wakes can be added to the CSR one in the calculation of the equilibrium distribution by the Haissinski equation. From the distribution the CSR factor and spectrum are then readily evaluated. Long range resistive wall: if not controlled it can reduce the CSR intensity. In general larger gap (once more) and high conductivity chambers are preferred. The wake fields due to the vacuum chamber of an accelerator can be modeled by using the a generic impedance model: In the short bunch regime (~ 1 ps), one finds that the effect of these wakes is usually negligible.

  19. The BESSY II Results CSR Studies at the ALS and IKNO. F.Sannibale INFN - LNF, Frascati, Italy, July 10, 2008 In 2002, The BESSY-II group provided the first demonstration of stable CSR in a storage ring. Abo-Bakr et al., PRL 88, 254801 (2002), and M. Abo-Bakr et al., Phys. Rev. Lett. 90, 094801 (2003) • Very interesting characteristics of the BESSY results were: • a very stable CSR flux (no presence of bursts), • an impressive power radiated in the THz region, • and a spectrum significantly broader than the one expected for a Gaussian distribution their bunch length. We started a collaboration with them…

  20. Understanding the BESSY Results CSR Studies at the ALS and IKNO. F.Sannibale g(l) C = 2.642 10-21 [SI units] G = 7.463 INFN - LNF, Frascati, Italy, July 10, 2008 (F. Sannibale et al., PRL 93, 094801, 2004.) (F.Sannibale et al., ICFA BD-Newsletter 35, 2004) The understanding of the physics behind the BESSY results showed the dominant role played in the short bunch regime by the SR wake and allowed to develop a model for optimizing a storage ring as a stable source of THz CSR. Such a model has been used for calculating the CSR performance of a number of existing storage rings (DAFNE, Bates, SPEAR, …) and also for designing storage rings completely optimized for the generation of stable CSR in the THz frequency range (CIRCE, IKNO).

  21. The `Femtoslicing’ Experiment CSR Studies at the ALS and IKNO. F.Sannibale INFN - LNF, Frascati, Italy, July 10, 2008 Beamline optimized for the generation of femtosecond x-ray pulses • A. A. Zholents, M. S. Zolotorev, Phys. Rev. Lett. 76, 912, (1996) In operation at the ALS since 1999, and in the last few years also at BESSY II, SLS and UVSOR, …

  22. Energy Modulation CSR Studies at the ALS and IKNO. F.Sannibale Right before modulation Right after modulation INFN - LNF, Frascati, Italy, July 10, 2008 For a few GeV electron beam, laser pulses with several mJ per pulse are required. This limits the max rep-rate to the order of few KHz

  23. From Energy Modulation to CSR Emission CSR Studies at the ALS and IKNO. F.Sannibale BL 5.3 BL 1.4 INFN - LNF, Frascati, Italy, July 10, 2008 Because of the ring longitudinal dispersion, when the beam propagates the energy modulation induces a density modulation. The characteristic length of these modulations is ~ the laser pulse length (~100 fs) after the energy modulation, of the order of the ps after ~ a turn, and it is completely absorbed by the bunch in the next few turns. Such density modulation radiate intense CSR in the THz frequency range

  24. THz CSR From Femtoslicing CSR Studies at the ALS and IKNO. F.Sannibale INFN - LNF, Frascati, Italy, July 10, 2008 Our group at the ALS did the first experimental observation and characterization of the CSR from the femtoslicing experiment: (J.M.Byrd et al., PRL 96, 164801, 2006.) The CSR signal is now one of the main diagnostics for the tune-up for the slicing experiment. The femtoslicing scheme, if optimized, could be used as a source of high energy per pulse THz radiation (~ 10 mJ) for pump and probe experiments. Similar results have been obtained also at BESSY II: K. Holldack et al., PRL 96, 054801 (2006) and K. Holldack et al., PRST-AB 8, 040704 (2005).

  25. The ‘Waveguide’ Effect CSR Studies at the ALS and IKNO. F.Sannibale INFN - LNF, Frascati, Italy, July 10, 2008 Window Position Qualitative agreement. Actual geometry difficult to simulate. Wavefront for photons with wavenumber of 50 cm-1 at the window position

  26. Optimized CSR by Slicing (CIRCE) CSR Studies at the ALS and IKNO. F.Sannibale Longitudinal Distribution Modulation at Radiator [ps] INFN - LNF, Frascati, Italy, July 10, 2008 • Laser Modulation: 6 times the energy spread • Laser pulse width: 50 fs FWHM • Distance modulator-radiator: 2.5 m • Current per bunch: 10 mA • Horizontal Acceptance 100 mrad (single mode) • Energy per pulse: 8.5 mJ • Electric field ~ 1 MV/cm • Rep. rate: 10 - 100 kHz • Pulse shaping capability Physics Retreat, Sept. 22, 04

  27. "Multicolor" Experiments Capability CSR Studies at the ALS and IKNO. F.Sannibale INFN - LNF, Frascati, Italy, July 10, 2008 • In the described femtoslicing experiment, severalmutually synchronousphoton beams with very different wavelengths are simultaneously available: • x-ray pulses with ~ 100 fs length • Near-IR or visible ~ 100 fs pulse from the slicing laser • THz CSR synchrotron radiation pulse with transform limited length This opens the possibility for many interesting combinations of"pump and probe" experiments where one of the beams is used for exciting the sample while another is used for measuring its characteristics during the excitation transient. By varying the delay between the pulses, one can reconstruct the whole sample response with resolution of the order of ~ 100 fs. Physics Retreat, Sept. 22, 04

  28. Tailoring the Shape of the THz Pulse CSR Studies at the ALS and IKNO. F.Sannibale Laser Intensity Charge distribution at the “source” point Spectrum at the “source” point INFN - LNF, Frascati, Italy, July 10, 2008 One additional interesting possibility of this scheme is the ability of tailoring the electric field of a terahertz pulse by an appropriate shaping of the slicing laser pulse. The example shows how by using a train of laser pulses instead of one single pulse one can concentrate the CSR power within a narrow bandwidth. The number of pulses defines the bandwidth while the distance between pulses defines the central frequency of the peak. In principle by this technique, arbitrary spectrum shapes can be obtained An example of application that could benefit from this capability is the control of complex chemical reactions where the shape of the exciting radiation is dynamically adjusted for optimizing the reaction. (J.M.Byrd et al., PRL 96, 164801, 2006.)

  29. Tailoring the THz Pulse is Really Possible! CSR Studies at the ALS and IKNO. F.Sannibale INFN - LNF, Frascati, Italy, July 10, 2008 A. Mochihashi et al., UVSOR Workshop on THz CSR (September 2007)

  30. Laser Seeding of the MBI CSR Studies at the ALS and IKNO. F.Sannibale INFN - LNF, Frascati, Italy, July 10, 2008 During the experiments for characterizing the CSR from femtoslicing, we discovered that if the beam is sliced above the MBI threshold the instability can be seeded. The MBI CSR bursts become synchronous with the slicing laser and the radiated THz power increases exponentially with the current per bunch.

  31. A Model for the Seeded MBI CSR Studies at the ALS and IKNO. F.Sannibale I I I I I I I IT IT IT IT IT IT IT INFN - LNF, Frascati, Italy, July 10, 2008 In the framework of the Heifets-Stupakov MBI theory the micro-bunching can be represented by the combination of “modes” with shape: In the “cold beam” approximation, the authors derived an analytical expression for the dispersion function between w and k=2p/l . From that, the growth rate and the velocity for the mode can be calculated: If one assumes, that the dynamic of the micro-bunch is dominated by the mode with larger growth rate then the for the CSR power radiated by the micro-bunch will be:

  32. Comparing with Data CSR Studies at the ALS and IKNO. F.Sannibale INFN - LNF, Frascati, Italy, July 10, 2008 J.M.Byrd et al, PRL 97, 074802, 2006 The comparison of this simple model predictions with the experimental data showed a good agreement up to a certain current (~19 mA). Above this value, the experimental points show a saturation effect that we think is due to the fact that at high currents, the MBI goes in the nonlinear regime before the perturbation arrives at the threshold point. Heifets and Stupakov studied the case by considering the combination of all unstable modes (SLAC-PUB-11815, 2006).

  33. Possible Applications CSR Studies at the ALS and IKNO. F.Sannibale INFN - LNF, Frascati, Italy, July 10, 2008 The graph shows how the 1 kHz power (synchronous with the laser) loses the quadratic dependence for currents above the MBI threshold at ~13 mA. At saturation, the average power of the seeded CSR burst is about two orders of magnitude larger than for the “conventional” slicing case, but shows very large power fluctuations. Pump and probe and other experiments not requiring shot to shot intensity stability could benefit from this several orders of magnitude increase in power. In a speculative scenario, part of the THz signal can be brought back into the ring to co-propagate the bending magnet with a subsequent electron bunch, modulating its energy and seeding the MBI that generates a new burst that is then used in the loop for seeding a new fresh bunch. By this process, that continues involving all the bunches, one can in principle bring the CSR emission to a stable high power saturation regime where all the bunches radiate coherently. Other FEL-like schemes exploiting the MBI gain are possible as well.

  34. The IKNO Infrastructure Proposal CSR Studies at the ALS and IKNO. F.Sannibale INFN - LNF, Frascati, Italy, July 10, 2008 IKNO (Innovation and KNOwledge) is also the ancient name of Sardinia and in our proposal to the Italian Roadmap of the Research Infrastructure, is the name of the Italian infrastructure, proposed in Sardinia to host this new high performance electron storage ring. • IKNO is a multi-user facility completely optimized for the THz CSR production and exploits all the described techniques for generating extremely powerful radiation on a very broad spectrum. • IKNO also produces an incoherent photon flux extending up to the VUV frequencies comparable with the one of existing 3rd generation light sources Present IKNO Collaboration:P. Innocenzi, A. Marcelli, F. Sannibale.

  35. The IKNO Storage Ring CSR Studies at the ALS and IKNO. F.Sannibale INFN - LNF, Frascati, Italy, July 10, 2008 More CIRCE STORY The IKNO storage ring is a more compact version of CIRCE (the LBNL proposal). It includes six periods (DBA cells) with six 3.1 m straight sections. Sextupole and octupole magnets allow full control of the ring nonlinear dynamics. Physics Retreat, Sept. 22, 04 Fernando Sannibale

  36. IKNO: The Optimized CSR Source CSR Studies at the ALS and IKNO. F.Sannibale INFN - LNF, Frascati, Italy, July 10, 2008 In the ultra-stable mode, IKNO generates a photon flux of CSR many order of magnitude higher than in existing 3rd generation light sources. The 3.1 m straight sections, allow for CSR for femtoslicing systems, extending the spectrum to few tens of THz, allowing for pulse shaping and opening to multicolor pump and probe experiments

  37. The IKNO As a Source of Incoherent UV SR CSR Studies at the ALS and IKNO. F.Sannibale INFN - LNF, Frascati, Italy, July 10, 2008 More CIRCE STORY The bending magnet ports and the 3.1 m straight sections, can also be used for generating a powerful flux of incoherent synchrotron radiation in the UV-VUV frequency range. Physics Retreat, Sept. 22, 04 Fernando Sannibale

More Related