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Commissioning of the Radio Frequency Quadropole Buncher Cooler

TRI µP – T rapped R adioactive I sotopes: µ -laboratories for fundamental P hysics. U Dammalapati, S. De, P G Dendooven, O Dermois L. Huisman, K Jungmann, A.J. Mol, G Onderwater, A Rogachevskiy, M Sohani, E Traykov, L Willmann and H W Wilschut.

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Commissioning of the Radio Frequency Quadropole Buncher Cooler

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  1. TRIµP – Trapped Radioactive Isotopes: µ-laboratories for fundamental Physics U Dammalapati, S. De, P G Dendooven, O Dermois L. Huisman, K Jungmann, A.J. Mol, G Onderwater, A Rogachevskiy, M Sohani, E Traykov, L Willmann and H W Wilschut Commissioning of theRadio Frequency Quadropole Buncher Cooler Lorenz Willmann SMI-06, Groningen 27/28.3.2006

  2. TRImP project and facility TrappedRadioactiveIsotopes: micro-laboratoriesfor FundamentalPhysics AGOR cyclotron Magnetic separator D Q Q D Production Target Wedge Q MeV Q Q Nuclear Physics D Q Magnetic Separator D Production target Ion Catcher Q keV Q Atomic Physics eV RFQ Cooler Thermo Ionizer: Talk by M. Sohani Thermo-ioniser meV AGOR cyclotron MOT RFQ cooler/buncher MOT Beyond the Standard Model TeV Physics Particle Physics neV MOT Low energy beam line

  3. Origin of Parity Violation • in Weak Interactions •  details of b-decays • Na, Ne isotopes Experimental Program of TRImP group Investigating discrete symmetry violations C, P, and T. • Dominance of Matterover Antimatter CP - Violation Time Reversal Symmetry Parity Violation  permanent electric dipole moments Ra isotopes

  4. Why do we need neutral atom traps?

  5. The role of atom trapping • long storage times • isotope (isomer) selective • spin manipulation • point source, no substrate • recoil ion momentum spectrometry • state preparation (for APNC,edm…) • “low” EM fields (otherwise ion traps) • Ideal environment • for precision experiments

  6. TRImP project and facility TrappedRadioactiveIsotopes: micro-laboratoriesfor FundamentalPhysics AGOR cyclotron Magnetic separator D Q Q D Production Target Wedge Q MeV Q Q Nuclear Physics D Q Magnetic Separator D Production target Ion Catcher Q keV Q Atomic Physics eV RFQ Cooler meV AGOR cyclotron MOT MOT Beyond the Standard Model TeV Physics Particle Physics neV MOT Low energy beam line

  7. RF capacitive coupling 2 x 330 mm • DC drag resistor chain • Standard vacuum parts (NW160) • UHV compatible design and materials • RF: 05-1.5MHz, 200Vpp, TRImP RFQ cooler/buncher concept U+VcosWt -(U+VcosWt) Buffer gas pressure (He): Trap position ~10-1 mbar ~10-3 mbar 10eV RFQ ion cooler thermal RFQ ion buncher Switching on end electrodes

  8. RFQ System/Drift Tube Pulsed extraction tube RFQ buncher Ion Pulses to experiments RFQ cooler pHe~ 10-6 mbar Beam from TI pHe~ 10-3 mbar pHe~ 10-1 mbar Background pressure 10-8 mbar

  9. RFQ Rods: • Many UHV resistors • segments individually coupled • flexible axial potential design • few RF connections • Drift tube Accelerator: • ideal for pulsed setup • no HV platform

  10. Transmission efficiencies with He buffer gas pA pA  (RFQ1)= I(EL3+10)/I(load) = =50÷70%  (RFQ2)= I(10)/I(EL3+10) = =50÷80%  (RFQ1+RFQ2)= I(10)/I(load) = =25÷40% I(load) = max.(I(EL2)+I(EL3)+I(10)) Both I(EL2) and I(10) increase with increase of difference between U(3,5) and U(4) (DU  14 V) I(EL2) RF off I(EL3) Acceleration-deceleration essential for transmission between RFQ1 and RFQ2! I(EL2) I(10) 23Na+ ions @ 10 eV, 15 eV U(acc) = 10 V, 15 V p(1): from 10-6 to 10-1 mbar U(4): from 0 V to +36 V (EL2), (EL3) and (10) connected to pA-meter (11) at same potential as (1) U(acc) = 10 V p(1) = 3.5*10-2 mbar U(4): from 0 V to +36 V EL3 and (10) connected to pA-meter (11) at same potential as (1) pA EL1 EL2 EL3 MCP Ion Source (8) (11) (1) p(1) p(2) (3) (5) Low Energy beam line Drift tube (4) (7) (9) (10)

  11. Simple Diagostic Tool: MCP with phosphor screen 2 2 -2 2 -2 2 -2 -2 119 V pp 120 V pp • Positional resolution, transverse emittance • Counting mode for low rate

  12. Filling of trap with different loading rates Space charge limited Heater Current On ion source

  13. Storage times of RFQ buncher Storage time limitations: - Space charge effect - Impurities in the gas 3.5.10-4 mbar He gas (~10-8 mbar background) without baking of system and standard gas purity (Helium 5.0)

  14. Direct detection of ion pulse on readout electrode Signal [V] Time [ms] • Charge integrating amplifier • rise time 40 nsec • integration time 20 msec • sensitivity 1 mV/1500 ions • noise 3 mV Storage time 100 msec Data averaged over 128 extraction cycles 10 msec 1 msec Extraction pulse Drift tube pulse

  15. TRImP RFQ cooler buncher system • Storage time several seconds achieved -> purity of buffer gasexpected 21Na production rate fills trap in 1s • Drift tube accelerator -> no high voltage platform • Good transmission > 70% of RFQ • Vacuum conditions good to couple to Magneto-optical Trap More results in the forthcoming thesis of Emil Traykov

  16. Coupling of RFQ and Low Energy beamline to MOT Trapping while operating RFQ achieved last Friday -> good differential pumping

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