1 / 34

Ultracolod Photoelectron Beams for ion storage rings

Ultracolod Photoelectron Beams for ion storage rings. Electron cooling. Electron-ion collision spectroscopy. D. A. Orlov, C. Krantz, A. Shornikov, A. Wolf. Max-Planck-Institut für Kernphysik, 69117, Heidelberg, Germany. 1 v e = v i. CSR (electrostatic).

ray
Télécharger la présentation

Ultracolod Photoelectron Beams for ion storage rings

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. Ultracolod Photoelectron Beams for ion storage rings Electron cooling Electron-ion collision spectroscopy D. A. Orlov, C. Krantz, A. Shornikov, A. Wolf Max-Planck-Institut für Kernphysik, 69117, Heidelberg, Germany 1 ve= vi CSR (electrostatic) TSR (magnetic) e-target e-cooler CSR E-Cooler TSR E-target • Low e-energies: => low current (100-1µA) =>higher kT|| • e-transport by B => slow ions distorted 2 ve ≠ vi Elab : 10-1eV Elab: 100-4000 eV Current - 2 mA Lifetime - 24 h kT< 1.0 meV kT|| = 0.02 meV DR of Sc18+ 6 meV Extremely high resolution is demonstrated! Cooling at eV-energies - it is a challenge!

  2. 2 E-cooling Collision resolution 6 Cooling of CF+ ions at TSR by 53 eV photoelectrons 7 Manipulation with 0.1-10 eV e-beams at TSR target 1 HOW TO: cold e-beams 3 electron collision spectroscopy @ TSR (keV) 4 Why? Electrostatic Cryogenic Storage Ring OUTLINE cold electrons 5 e-beams of eV energies, CSR cooler Dmitry Orlov, MPI-K, PESP-08

  3. kT=110-120 meV Evac EF Thermocathode vacuum T=1300-1500 K Cold electrons. How to (A): Photocathode kTC = 10 meV Thermocathode kTC > 100 meV kT=10 meV Ec Evac Suppression Suppression EF Suppression Ev (CsO) vacuum GaAs T= 80 K Suppression Strong energy and impulse relaxations Energy spreads of about kT Laser: 1W @ 800 nm9 (transmission) 2W @ 532 nm (reflection) E-current: 0.1- 2.5 mA Lifetime : >24 h Fully activated cathode: QY= 15-35% QYeff=1 % D.A. Orlov et al., APL, 78 (2001) 2721; Dmitry Orlov, MPI-K, PESP-08

  4. E ΔE U0 ΔE v║ Δv' Δv Cold electrons. How to make them colder (B): Reduction of kT 1. Magnetic expansion B0 (high field) Bguide(low field)  = 20 Photocathode kT = 0.5 meV Thermocathode kT = 5-6 meV 2. Acceleration Reduction of kT|| Phase-space conservation kT|| = 0.02-0.1 meV

  5. Cold electrons. How o keep them cold (C): High magnetic field is required high current + magnetic field high current low current e 1. To avoid beam divergence e e rc e 2. To suppress TLR keeping dT|| / dZ < 5 μeV/m : B ne-1/3 ne-1/3 e rc << λc e 3. To provide adiabatic transport Typical transition lengths R=100 mm R λc << R B

  6. 6 Cooling of CF+ ions at TSR by 53 eV photoelectrons 7 Manipulation with 0.1-10 eV e-beams at TSR target 3 electron collision spectroscopy @ TSR (keV) 4 Why? Electrostatic Cryogenic Storage Ring 2 E-cooling Collision resolution cold electrons 1 HOW TO: cold e-beams 5 e-beams of eV energies, CSR cooler Dmitry Orlov, MPI-K, PESP-08

  7. Principle of Electron Cooling 10-3 e-cooling TSR Dmitry Orlov, MPI-K, PESP-08

  8. Flattened electron distribution V kT║≪ kT V║ Recombination velocity Electron-ion collision resolution ve= vi Real resonance position DR rate coefficient For high energiesEr: Dmitry Orlov, MPI-K, PESP-08

  9. 6 Cooling of CF+ ions at TSR by 53 eV photoelectrons 7 Manipulation with 0.1-10 eV e-beams at TSR target 3 electron collision spectroscopy @ TSR (keV) 4 Why? Electrostatic Cryogenic Storage Ring 2 E-cooling Collision resolution cold electrons 1 HOW TO: cold e-beams 5 e-beams of eV energies, CSR cooler Dmitry Orlov, MPI-K, PESP-08

  10. Electron collision spectroscopy.TSR electron target. Detectors (ions and neutrals) ~0.2 ... 8 MeV/u Neutrals detector Movable ion detector e-target Collector Electron gun with magnetic expansion ≈10...90 TSR dipole e-source Adiabatic acceleration e- Interaction section 1.5m Ion beam Dmitry Orlov, MPI-K, PESP-08

  11. e - nℓ nℓ (Aq +)*+ nℓ ( A(q -1)+ )* Aq + + e = ( A(q -1)+ )** Electron captureresonance Productdetection Eres Electron collision spectroscopyon multi-charged ions

  12. E 1s2 2p3/2 En ΔEcore (1s2 2p3/2 nℓ'j )J 1s22s Eres = 1.0 meV T┴ T|| ~ 0.02 meV 100 meV Core excitation energies ΔE (2s–2p) = 44.30943(20) eV (±0.2 meV, 4.6 ppm) (<1% few body QED) n = 10 PRL, 100, 033001 (2008) (2p3/210d5/2)J = 4 (2p3/210d3/2)J = 2 Electron target Photocathode (2p3/210d3/2)J = 3 45Sc18+ TSR – 4 MeV/u

  13. Rotational resolution (DR rate) direct & indirect process Dissociative recombination of HD+: rate spectrum - e B* A + + e - (AB+)*+ nℓ = AB ** AB+ HD+ (1sσ, v = 0, J ) + e → HD** (1sσ nℓλ , v'J' ) → H(n) + D(n' ) Vibration v=0 -> 1 0.15 eV Rotation j=0 -> 1 4.5 meV PRL 100, 193201 (2008) Dmitry Orlov, MPI-K, PESP-08

  14. EKER – ECM-kT, milli-eV 0 20 50 5 100 HF**(V 1S+) Probability (normalized) v=0 PRELIMINARY Rotational resolution J=0,1,2,…. 8 6 d2D [mm] 4 10 2 0 Particle distance, mm Dissociative recombination of HF+: 2D imaging ~ 12 m ~cm vbeam (~MeV) detector surface Electron - Target H(n=2) + F(2P3/2,1/2) HF**(V 1S+) HF+ (X 2P,v=0 ,J) + e- H(n=2) + F(2P3/2) Dmitry Orlov, MPI-K, PESP-08

  15. 6 Cooling of CF+ ions at TSR by 53 eV photoelectrons 7 Manipulation with 0.1-10 eV e-beams at TSR target 3 electron collision spectroscopy @ TSR (keV) 4 Why? Electrostatic Cryogenic Storage Ring 2 E-cooling Collision resolution cold electrons 1 HOW TO: cold e-beams 5 e-beams of eV energies, CSR cooler Dmitry Orlov, MPI-K, PESP-08

  16. T< 10 K is required after production in the ion source Clusters, biomolecules (M up to few 1000 amu) ELECTROSTATIC Storage Rings (no mass limitation) n=4 HD+ + e- H + D vibrational quantum state n=3 after some second storage n=2 n=1 Boltzmann distribution (300 K @ TSR) n=0 rotational quantum state Electrostatic Storage Ring Reaction microscope M= 1-100(1000) amu T=10 (2K) neutrals CSR E-target XHV (n<103 cm-3) Diagnostic section Ion injection Electrostatic Cryogenic Storage Ring at 2 K Dmitry Orlov, MPI-K, PESP-08

  17. 6 Cooling of CF+ ions at TSR by 53 eV photoelectrons 7 Manipulation with 0.1-10 eV e-beams at TSR target 3 electron collision spectroscopy @ TSR (keV) 4 Why? Electrostatic Cryogenic Storage Ring 2 E-cooling Collision resolution cold electrons 1 HOW TO: cold e-beams 5 e-beams of eV energies, CSR cooler Dmitry Orlov, MPI-K, PESP-08

  18. Ion mass [amu] Ion energy [keV] Electron energy [eV] Electron current [mA] Electron density [10 6 cm -3] Cooling time (cold beam) [s] 1 300 165 2.1 10 0.03 1 20 11 0.02 0.7 1.8 3 300 54 0.4 3.2 0.28 32 300 5.1 0.01 0.3 28 100 300 1.6 0.002 0.1 280 Features of low-energy e-beams (A) 1. Low voltage Low current @ density High-perveance? P=1 μPerv kBTe=1.0 meV Lc=3.3 C=0.028 Dmitry Orlov, MPI-K, PESP-08

  19. Features of low-energy e-beams (B) 2. Low voltage High kT|| Photoelectron source Low T║ 3. High Bguid {avoid beam divergence; suppress TLR; adiabatic transport} Strong ion deflection Better for slow electrons Dmitry Orlov, MPI-K, PESP-08

  20. New Concept for the CSR Electron Cooler/Target We need to cool 20 keV protons Bmin≈20 G toroid merging Dipole merging 1-2 G 30 G Dmitry Orlov, MPI-K, PESP-08

  21. General view Ion track New Concept for the CSR Electron Cooler/Target We need to cool 20 keV protons Bmin≈20 G toroid merging Dipole merging 1-2 G 30 G Merging Box Dmitry Orlov, MPI-K, PESP-08

  22. - Larmor length Heating start at app. Adiabatic electron transport Adiabatic motion Adiabatic criterion Transverse temperature For modeled field geometry Scaling rule for critical energy Results of e-tracking calculation (TOSCA code) Cross-sections of Heating of paraxial beam kT┴0 Finite element analysis with TOSCA code

  23. 7 Manipulation with 0.1-10 eV e-beams at TSR target 3 electron collision spectroscopy @ TSR (keV) 4 Why? Electrostatic Cryogenic Storage Ring 2 E-cooling Collision resolution cold electrons 1 HOW TO: cold e-beams 5 e-beams of eV energies, CSR cooler 6 Cooling of CF+ ions at TSR by 53 eV photoelectrons Dmitry Orlov, MPI-K, PESP-08

  24. Themocathode Themocathode, September 2006, 0eV, 12-30 s center-of-mass 12-30 s Ecm = 0 eV C F Photocathode Electron-target Photocathode, March 2007, 0eV, 12-30 s center-of-mass 12-30 s Ecm = 0 eV Photocathode C F T~ 1.0 meV I = 0.34 mA ne=3∙106 cm-3 Low-energy cooling of CF+ cooling by 53 eV electrons Dmitry Orlov, MPI-K, PESP-08

  25. CF+– cooling time TSR Photocathode, March 2007 • Current: 0.34 mA • B-expansion: 20 • ne=3∙106 cm-3 • T┴ =1.0 meV • cool< 2 s • Detector (X/Y): σ 0.4 / 0.3 mm • Ion beam: X Y ε2.5∙10-3 0.9∙10-3 mm∙mrad σ 200 37 μm ΔP/P 2.5∙10-5 2.5∙10-5 x=1.8 s 1 mm y=1.4 s 1 mm Dmitry Orlov, MPI-K, PESP-08

  26. 3 electron collision spectroscopy @ TSR (keV) 4 Why? Electrostatic Cryogenic Storage Ring 2 E-cooling Collision resolution cold electrons 1 HOW TO: cold e-beams 5 e-beams of eV energies, CSR cooler 6 Cooling of CF+ ions at TSR by 53 eV photoelectrons 7 Manipulation with 0.1-10 eV e-beams at TSR target Dmitry Orlov, MPI-K, PESP-08

  27. Manipulation with magnetized eV-electrons TSR target EDC, log. scale Ekin Wemission Drift tubes Wcathode EF Ekin SC SC Wmetal V0 Wmetal V Cathode Collector Cathode Dmitry Orlov, MPI-K, PESP-08

  28. Manipulation with magnetized eV-electrons TSR target EDC, log. scale Ekin Wemission Drift tubes Wcathode EF Ekin SC SC Wmetal V0 Wmetal V Cathode Collector To collector Cathode Drift tubes • 1. Work function difference • 2. Space charge at the cathode • 3. Space charge SC(Ie, V) in the interaction • region can be calculated independently. Ekin ≠ q(V0V) Ekin = q(V0V)(WmetalWemission)SC Dmitry Orlov, MPI-K, PESP-08

  29. Drift tubes Cathode Collector Manipulation with magnetized eV-electrons Ekin Wemission SC EF Wmetal V0 V To collector Cathode Drift tubes Ekin = q(V0V)(WmetalWemission)SC Ie=3µA A A V0=20 V Ie=40 pA B B Ekin (WmetalWemission) SC

  30. Drift tubes Cathode Collector Manipulation with magnetized eV-electrons Ekin Wemission SC EF Wmetal V0 V To collector Cathode Drift tubes Ekin = q(V0V)(WmetalWemission)SC Ie=4.5 µA A V0=20 V A Ie=40 pA Ekin (WmetalWemission) SC

  31. 3 electron collision spectroscopy @ TSR (keV) 4 Why? Electrostatic Cryogenic Storage Ring 2 E-cooling Collision resolution THANK YOU ! 1 HOW TO: cold e-beams 5 e-beams of eV energies, CSR cooler 6 Cooling of CF+ ions at TSR by 53 eV photoelectrons 7 Manipulation with 0.1-10 eV e-beams at TSR target Questions? Dmitry Orlov, MPI-K, PESP-08

  32. Dmitry Orlov, MPI-K, PESP-08

  33. 50 Bg 80 φ=100 Cathode, -100 V Extraction electrode, 0 V Entrance, extraction electrode Cathode Electron beam formation – adiabaticity adiabaticity: dB/dz, dE/dz small against cyclotron length Higher adiabaticity Low energies ζ=0.1-0.2 Typical transition lengths 100 – 200 mm 40 G 80 G 320 G Dmitry Orlov, MPI-K, PESP-08

  34. Electron target at TSR TSR dipole Preparation chamber (photocathode) Acceleration section Interaction section electron beam Correction dipoles Toroid Collector Ion beam Rails Dmitry Orlov, MPI-K, PESP-08

More Related