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Patricia Aguar Bartolomé , Kurt Aulenbacher , Valery Tioukin , Jürgen Diefenbach

Møller Polarimetry with Polarized Atomic Hydrogen at MESA. Patricia Aguar Bartolomé , Kurt Aulenbacher , Valery Tioukin , Jürgen Diefenbach Institut für Kernphysik , Universität Mainz PAVI’14, Syracuse, NY 17th July 2014. Outline. Physics Motivation

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Patricia Aguar Bartolomé , Kurt Aulenbacher , Valery Tioukin , Jürgen Diefenbach

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  1. MøllerPolarimetry with Polarized Atomic Hydrogen at MESA Patricia AguarBartolomé, Kurt Aulenbacher, Valery Tioukin, Jürgen Diefenbach InstitutfürKernphysik, UniversitätMainz PAVI’14, Syracuse, NY 17th July 2014 Patricia Aguar Bartolome - PAVI'14

  2. Outline • Physics Motivation • Polarized Atomic Hydrogen Target • Status of the Mainz Hydro-MøllerTarget • Beam Stabilization Test • Summary Patricia Aguar Bartolome - PAVI'14

  3. Physics Motivation Goal: Low energy PV electron scattering experiments at MESA with systematic accuracy < 0.5% for beam polarization measurements Hydro-Møller PV Detector MESA (Mainz Energy recovering Superconducting Accelerator) Patricia Aguar Bartolome - PAVI'14

  4. Physics Motivation Polarimetry Methods • ComptonScattering:Accurateenough at Ebeam > 4GeV, butaccuracy • around1% at lowenergiesNotenoughfor PV-experiments • MøllerScatteringwithferromagnetic target Patricia Aguar Bartolome - PAVI'14

  5. Physics Motivation PolarimetryMethods • MøllerScatteringwithpolarizedatomichydrogen gas, stored in • a ultra-coldmagnetictrap • E.Chudakov and V.Luppov IEEE Trans. on Nucl. Sc., 51, 1533 (2004) Patricia Aguar Bartolome - PAVI'14

  6. Polarized Atomic Hydrogen Target Magneticfield B splits H1groundstate At B = 8T, sinq≈0.3% Mixingangle tan2q ≈ 0.05/B(T) Mixture ~ 53% of and ~ 47% of , Pe ~ 1-d,  ~ 10-5 Storage Cell • In a field gradient a force • Pulls,intothestrongfield • Repels,out of thestrongfield H+H H2 • recombination(releasing ~ 4.5 eV) • higherat lowT cellwallscoatedwith ~50nm • superfluid4He • Gas density: cm-3 Patricia Aguar Bartolome - PAVI'14

  7. Dilution Refrigerator and Magnet T=300mK of theatomictrap can be reachedusing a DilutionRefrigerator and therequieredB=8Tusing a superconductingsolenoid Dilutionrefrigerator and magnet shippedfrom UVA toMainz Patricia Aguar Bartolome - PAVI'14

  8. Status of the Atomic Hydrogen Target New DilutionRefrigeratorneeds tobedesigned and produced!! Test superconductingsolenoid Patricia Aguar Bartolome - PAVI'14

  9. Status of the Atomic Hydrogen Target UVA SuperconductingSolenoidTest • 8 thermo sensors (4 Pt-100, Pt-1000, Si-Diode, 2 Cernox) placed in different • points of the solenoid • Several tests with Nitrogen (T~77K) were successfully performed • Infeasible Helium (T~4K) test due to the appearance of a big leakrate • New cooling set up for the solenoid needs to be designed and produced Patricia Aguar Bartolome - PAVI'14

  10. Status of the 8T Superconducting Magnet New coolingsystemsetup design • Most of the new cooling system • componentscurrently under • construction • Estimated time to assemble • the new set up ~ August • Cooling down of the magnet • with Helium ~ September Vacuum Vessel Courtesy of J.Bibo and D. Rodriguez Patricia Aguar Bartolome - PAVI'14

  11. Status of the 8T Superconducting Magnet New coolingsystemsetup design • Most of the new cooling system • components currently under • construction • Estimated time to assemble • the new set up ~ August • Cooling down of the magnet • with Helium ~ September Copper Shields (T ~77K) Courtesy of J.Bibo and D. Rodriguez Patricia Aguar Bartolome - PAVI'14

  12. Status of the 8T Superconducting Magnet New coolingsystemsetup design • Most of the new cooling system • components currently under • construction • Estimated time to assemble • the new set up ~ August • Cooling down of the magnet • with Helium ~ September Solenoid (T~4K) Courtesy of J.Bibo and D. Rodriguez Patricia Aguar Bartolome - PAVI'14

  13. Status of the 8T Superconducting Magnet New coolingsystemsetup design • Most of the new cooling system • components currently under • construction • Estimated time to assemble • the new set up ~ August • Cooling down of the magnet • with Helium ~ September Courtesy of J.Bibo and D. Rodriguez Patricia Aguar Bartolome - PAVI'14

  14. Status of the 8T Superconducting Magnet Patricia Aguar Bartolome - PAVI'14

  15. Status of the Atomic Hydrogen Target Preliminary design of the new Dilution Refrigerator • General considerations • Lowtemperature (T=300mK) and highcoolingpower (Q=75-100mW) • Optimizationby a carefulcalculation: • - Heatexchangers • - Pressuredrop in thepumpinglines • - Condensation of the mixture • - Amount of 3He and 4He gas needed • - Volumes of allpartsinsidethe DR (separator, evaporator, • still) and alsopumps and lines • - Produce new mixingchamber Patricia Aguar Bartolome - PAVI'14

  16. Status of the Atomic Hydrogen Target Preliminarydesign of the new DilutionRefrigerator • HeatExchangers (HE) • Design of the HE is of majorimportance. Theimportantparameters • are: • 1. Small volumetoreachtheequilibriumtemperatureveryfast • 2. Small thermalresistancebetweenthestreamstogetgood • temperatureequilibriumbetweenthem • Imperfections and impurities can influencethetransport of heat • Thermalboundaryresistancebetweenhelium and the HE material • at T<1K Kapitzaresistance~ T3 Patricia Aguar Bartolome - PAVI'14

  17. Status of the Atomic Hydrogen Target Preliminarydesign of the new DilutionRefrigerator 1.1K stage HE currentlyunder construction in ourMechanical Workshop Patricia Aguar Bartolome - PAVI'14

  18. Beam Stabilization for PV experiments Requirementsforthe PV experiment at MESA • P2 expectedphysicsasymmetry< 50 ppb • Beamenergy~ 150 MeV(externalbeam) • DPB/PB ≤ 0.5% • Beamquality: • Beammustbestabilized(DAi0) • Helicitycorrelationsmustbesuppressed(Ai 0) • Beamparameters are correlatedwithhelicityAi • Noiseonbeamparameters (helicity un-correlated) DAi Patricia Aguar Bartolome - PAVI'14

  19. Beam Stabilization Beam stabilization and solenoid test set up Reliable 3T solenoidfor first tests Patricia Aguar Bartolome - PAVI'14

  20. Beam Stabilization Principle of beamstabilization • Cavitymonitorsmeasurebeam position (XYMOs) • Steeringmagnetscorrectbeamdirection (WEDLs) Patricia Aguar Bartolome - PAVI'14

  21. Beam Stabilization Beamtestswithsolenoid • Use anavailable 3T superconductingsolenoid • Gainexperiencesteering <200 MeVbeamthrough a superconductingsolenoid • Operatebeam position/anglestabilizationacrossthesolenoid • Mostrealistic test of polarimetry+beamstabilizationfor P2 possiblebefore • MESA is in operation Patricia Aguar Bartolome - PAVI'14

  22. Summary/Outlook • PV electronscatteringexperiments at MESA are planned • systematicaccuracy of < 0.5% forthebeampolaizationmeasurements • AtomicHydrogen gas, stored in a ultra-coldmagnetictrap can provide • thisaccuracy • A solenoid and a dilutionrefrigeratorwereshippedfromtheUniversity • of Virginia toMainz • New coolingdownsetupof thesolenoidand new DR design and • productionisin progress • Productionof a new mixingchamberand a atomichydrogendissociator • isalsorequired • Beamstabilization test isplannedwithinthenextyear Patricia Aguar Bartolome - PAVI'14

  23. BACKUP Patricia Aguar Bartolome - PAVI'14

  24. Beam Stabilization PlannedBeam test setup Patricia Aguar Bartolome - PAVI'14

  25. Beam Stalilization Patricia Aguar Bartolome - PAVI'14

  26. Beam Stalilization Patricia Aguar Bartolome - PAVI'14

  27. Polarized Atomic Hydrogen Target Gas Lifetime in the Cell • Loss of hydrogen atoms from the cell due to: • Thermal escape through the magnetic field gradient dominates at T > 0.55 K • Recombination in the gas volume negligible up to densities of ~1017 cm-3 • Recombination in the cell surface constant feeding the cell with atomic • hydrogen E.Chudakov and V.Luppov IEEE Trans. on Nucl. Sc., 51, 1533 (2004) Patricia Aguar Bartolome - PAVI'14

  28. Polarized Atomic Hydrogen Target Contamination and Depolarization of the Target Gas No Beam • Hydrogenmolecules~ 10-5 • High energyatomicstates and < 10-16 • Excitedatomicstates< 10-5 • Helium and residual gas < 0.1% empty target measurement • withthebeam Beam Impact • Depolarization by beam generated RF field • Gas heating by beam ionization losses < 10-10 • Depolarized ions and electrons contamination < 10-5 • Contamination by excited atoms < 10-5 Expecteddepolarization Patricia Aguar Bartolome - PAVI'14

  29. Polarized Atomic Hydrogen Target Dynamic Equilibrium and Proton Polarization As a result, the cell contains predominantly In a dynamic equilibrium, P ~ 80 % in about 10 min. Patricia Aguar Bartolome - PAVI'14

  30. Physics Principles of the DR Cooling power: Below 0.3K the dilution refrigerator has much higher cooling power Patricia Aguar Bartolome - PAVI'14

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