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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).

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Ultracolod Photoelectron Beams for ion storage rings

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  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

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