Review of Synchrotron Radiation based Diagnostics for Transverse Profile Measurements Gero Kube DESY / MDI gero.kube@desy.de � Introduction � Small Emittance Measurements � Non-standard Profile Measurements
D eutsches E lektronen SY nchrotron one of the world's leading centres for the investigation of the structure of matter develops, runs and uses accelerators and detectors for photon science and particle physics carries out fundamental research in a range of scientific fields and focuses on three principal areas: Accelerators Photon science Particle physics John Adams Institute (Oxford), December 4, 2008 Gero Kube, DESY / MDI
DESY Accelerators Shut down of ep collider HERA in June 2007 no high energy physics accelerator on-site no need for proton accelerator chain Remaining accelerators e injector chain: Linac II, PIA, DESY II, PETRA II DORIS III 1 st generation synchrotron light source FLASH VUV Free Electron Laser (4 th generation synchrotron light source) → accelerator center for synchrotron radiation Future accelerator projects European XFEL: 4 th generation linac based synchrotron light source PETRA III: 3 rd generation storage ring based synchrotron light source John Adams Institute (Oxford), December 4, 2008 Gero Kube, DESY / MDI
Accelerator Projects @ DESY : 4 th generation light source 3.4km John Adams Institute (Oxford), December 4, 2008 Gero Kube, DESY / MDI
Accelerator Projects @ DESY : 4 th generation light source Energy: 20 GeV Bunch Charge: 1 nCb Bunch Length: 80 fsec One injector initially installed λ min = 0.1 nm (12.4 keV) Connection to 2 nd stage upgrade included in beam distribution layout John Adams Institute (Oxford), December 4, 2008 Gero Kube, DESY / MDI
Accelerator Projects @ DESY Thursday 29/11/2007: Hans Weise (DESY), The European XFEL project http://www.adams-institute.ac.uk/lectures/XFEL_JAI.pdf Conversion of PETRA in a dedicated light source John Adams Institute (Oxford), December 4, 2008 Gero Kube, DESY / MDI
PETRA History The discovery of the gluon, the carrier particle of the strong nuclear force, in 1979 is counted as one of PETRAs biggest successes. 23.3 GeV / beam !!! John Adams Institute (Oxford), December 4, 2008 Gero Kube, DESY / MDI
PETRA History PETRA II pre-accelerator for HERA (1988-2007) 12 GeV electrons (positrons); 40 GeV protons, Sync. Radiation Facility since 1995: equipped with one undulator to create synchrotron radiation especially in the X- ray part of the spectrum. John Adams Institute (Oxford), December 4, 2008 Gero Kube, DESY / MDI
PETRA III Upgrade Project Reconstruction of 1/8 of PETRA (288 m) in a new experimental hall 9 new straight sections in the new arc, canted undulators → 14 separate undulator beamlines 100 m damping wiggler in the long straights Renewal of the entire machine Renewal of injection system (and removal of the blue) Start commissioning: Middle/End of February 2009 Parameters: E = 6 GeV I = 100 mA (200 mA) – top-up ε ≈ 1.0 nm rad κ = 1% 960 bunches, 40 bunches, variable patterns Additional options for long undulators John Adams Institute (Oxford), December 4, 2008 Gero Kube, DESY / MDI
Renewal of Entire Machine impressions from the accelerator tunnel Middle 2008 … Beginning 2007 … July 2007 … renewal of individual components New Magnet Coils John Adams Institute (Oxford), December 4, 2008 Gero Kube, DESY / MDI
Damping Wiggler Sections improvement of natural emittance: 4.5 nm rad → 1.0 nm rad 2 damping wiggler sections (~ 100m long) complicated vacuum system: → absorption of up to 400 kW per section John Adams Institute (Oxford), December 4, 2008 Gero Kube, DESY / MDI
Diagnostics Elements AC - Monitor Stripline - Monitor Laser Wire Scanner DC - Monitor John Adams Institute (Oxford), December 4, 2008 Gero Kube, DESY / MDI
Experimental Hall Middle 2006 … Middle 2008 … John Adams Institute (Oxford), December 4, 2008 Gero Kube, DESY / MDI
Experimental Hall Accelerator Tunnel Dipole Girder Photon Beamline John Adams Institute (Oxford), December 4, 2008 Gero Kube, DESY / MDI
Light Sources: Remarks key parameter: spectral brilliance Number of photons = B measure for phase space density of photon flux 2 2 [sec] [mm ] [ mrad ][ 0.1% bandwidth] user requirement: high brightness → lot of monochromatic photons on sample Brilliance Comparison connection to machine parameters N I γ beam ∝ ∝ B σ σ σ σ ε ε ' ' x x y y x y requirements for storage ring and diagnostics i) high beam current ii) small beam emittance � achieve high currents � achieve small emittance (task of lattice designer) � cope with high heat load (stability) � preserve emittance (stability) � measure small emittance diagnostics is important › John Adams Institute (Oxford), December 4, 2008 Gero Kube, DESY / MDI
PETRA III Diagnostics PETRA III: • 228 BPMs (Orbit) • 6 Current Monitors • 2 Stripline-BPMs and 2 Button-BPMs for Multibunch Feedback • 1 Button-BPM for longi- tudinal Feedback • 1 Wall Gap Monitor • 1 Laser-Wirescanner • 2 Beamlines for Emit- tance Diagnostics • 3 Screens Transfer Lines: • 20 BPMs • 10 Current Monitors • 4 Wall Gap Monitors • 11 Screens John Adams Institute (Oxford), December 4, 2008 Gero Kube, DESY / MDI
Synchrotron Radiation Properties non-invasive bending magnets opening angle choice of operational range ~ 1/ g define angular divergence John Adams Institute (Oxford), December 4, 2008 Gero Kube, DESY / MDI
Synchrotron Radiation Spectrum Radiation Spectrum Polarization (Photons / s ·m rad (0.1% band pass)) 10 15 10 14 Photon flux critical critical energy: 3 γ 3 c 10 13 ω = h h c ρ 2 l c g : Lorentz factor 10 12 ω h r : bending radius c l ( Å) 10 5 10 4 10 3 10 2 10 1 10 0 10 -1 Infrared Visible Ultraviolet Soft X-ray Hard X-rays ω (eV) h 10 -1 10 0 10 1 10 2 10 3 10 4 10 5 John Adams Institute (Oxford), December 4, 2008 Gero Kube, DESY / MDI
Synchrotron Radiation Properties numerical near field calculation (SRW, SPECTRA,…) influence single particle field John Adams Institute (Oxford), December 4, 2008 Gero Kube, DESY / MDI
Single Particle Time Structure • geometrical interpretation t Q t+ D t ρ 4 Δ = t D t 3 Q 3 γ c r 2Q Q = 2/g D t: distance in travel time between photon and particle • radiation field in time domain -1/w c +1/w c consequence: time interval from ρ maximum to zero 4 Δ = ω = t 2 c 3 3 γ c crossing defines spectrum ( w c ) 6 GeV electron, field in orbit plane John Adams Institute (Oxford), December 4, 2008 Gero Kube, DESY / MDI
Synchrotron Radiation Properties monitoring parameter › emittance - size - divergence John Adams Institute (Oxford), December 4, 2008 Gero Kube, DESY / MDI
Beam Emittance • projected area of transverse phase space volume emittance ε not directly accessible for beam diagnostics • • beam size σ = ε β • beam divergence σ = ε γ ' 2 2 σ = ε β + η Δ σ = ε γ + η Δ ( / ) ' ( ' / ) • dispersion: p p p p σ • influence of radiation properties rad σ • monitor resolution mon σ ε β γ η η Δ σ σ σ photon beam spot ( , , , ' , / , , , ) › › p p ph ph mon rad measure calculate John Adams Institute (Oxford), December 4, 2008 Gero Kube, DESY / MDI
Radiation Properties λ spatial resolving detector ∆Ψ ∆σ e lens λ • resolution limit: uncertainty principle Δ σ ≈ ΔΨ 2 • synchrotron radiation: small vertical emission angle DY 1 / 3 λ ≥ λ ⎛ ⎞ λ typical half opening angle : ( ) 1 ΔΨ = ⎜ ⎟ << 1 mrad c ⎜ ⎟ γ λ ⎝ ⎠ c resolution fully limited by uncertainty principle › • example: E = 6 GeV, l c = 0.35 nm (ESRF) Ds v = 260 m m l= 500 nm (s v = 30 m m) › John Adams Institute (Oxford), December 4, 2008 Gero Kube, DESY / MDI
Resolution Improvements 1.) decrease of wavelength VUV, soft X-ray, hard X-ray, … › Ds v = 1 m m l= 0.124 nm (10 keV photons) › 2.) interferometric approach T. Mitsuhashi , Proc. Joint US-CERN-Japan-Russia School of Particle Accelerators, Montreux, 11-20 May 1998 (World Scientific), pp. 399-427. visibility: probing spatial coherence of synchrotron radiation › − I I max min = V + I I max min point source V = 1 T. Mitsuhashi, Proc. BIW04, AIP Conf. Proc. 732, pp. 3-18 D n: photon number Δ n ⋅ ΔΦ ≈ • resolution limit: uncertainty principle 1 DF : photon phase John Adams Institute (Oxford), December 4, 2008 Gero Kube, DESY / MDI
Resolution Improvements 1.) decrease of wavelength VUV, soft X-ray, hard X-ray, … › Ds v = 1 m m l= 0.124 nm (10 keV photons) › 2.) interferometric approach T. Mitsuhashi , Proc. Joint US-CERN-Japan-Russia School of Particle Accelerators, Montreux, 11-20 May 1998 (World Scientific), pp. 399-427. visibility: probing spatial coherence of synchrotron radiation › − I I max min = V + I I max min extended source V < 1 T. Mitsuhashi, Proc. BIW04, AIP Conf. Proc. 732, pp. 3-18 D n: photon number Δ n ⋅ ΔΦ ≈ • resolution limit: uncertainty principle 1 DF : photon phase John Adams Institute (Oxford), December 4, 2008 Gero Kube, DESY / MDI
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