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A Proposal of a Polarized 3 He ++ Ion Source with Penning Ionizer for JINR

This proposal suggests the installation of a 3He++ polarized ion source at JINR, Dubna, for the production of an intensive polarized 3He++ beam in the NUCLOTRON accelerator. The source will consist of a polarizing apparatus for 3He gas and an ionizing system. The project includes a Rb-3He polarizer, an ionizer based on EBIS and Penning ionization, and a spin-precessor for spin orientation.

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A Proposal of a Polarized 3 He ++ Ion Source with Penning Ionizer for JINR

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  1. A Proposal of a Polarized 3He++ Ion Source with Penning Ionizer for JINR N.N. Agapov, Yu.N. Filatov, V.V. Fimushkin, L.V. Kutuzova, V.A. Mikhailov, Yu.A. Plis, Yu. V. Prokofichev, V.P. Vadeev Joint Institute for Nuclear Research, Dubna, Russia

  2. There is some interest to 3Не++polarized beam.

  3. Goal is to make an intensive polarized 3He++ beam in theJINR superconducting accelerator NUCLOTRON. The installation of the 3He++polarized ion source at the accelerator complex of JINR, Dubna will allows to continue the spin physics experiments. This is an important part of the Laboratory of High Energies scientific program.

  4. The source will consistof an apparatus for for polarizing of 3Не and for ionizing of polarized 3Не gas.

  5. Rb - 3Не polarizer • There are two methods of the 3Не-gas polarization, namely: • by spin exchange with an opticallly pumped Rb-vapour, and • by metastability exchange scattering with optically pumped metastable 3Не-atoms in their 1s 2s 3S1-state • Our option is Rb-3Не method.

  6. Rb-3Неpolarizer hardware. • Rb-3Не polarizer includes FAPSYSTEM (COHERENT production) 25W laser (Wavelength - 795 nm, Width - 2 nm), • optical system, • glass polarizing cell (3Не, Rb, N2), • cell baking and Rb distillation, • refilling system (3Не – N2 mixture), • magnet coils system, 3Не system of cryosorption purification, • system of polarization measurements (NMR – polarimeter).

  7. Optical system involves polarizing cube, mirrors, lenses, /4 plates. • It is supposed to use pyrex glass(Corning7740) cells.

  8. Polarizing cell parameters • Volume - 100 cm3 • 3Не pressure – 1.5-3 bar • Cell temperature - 180-200 оС

  9. Magnet system consisting of four coils will provide for the 100 Gs magnetic field with a degree of homogeneity 10-4

  10. NMR detection is the most important tool for monitoring the polarization process. • This is possible to do measuring the signal of the forced precession. • The project polarization of 3Не gas into 0.1 l·bar cell is 50%.

  11. Rb-3Не polarizer • 1. magnet system 2.optical system 3.support 4. glass polarizing cell (3Не, Rb, N2)5. cell baking system 6. polarimeter coil

  12. It is known the polarized gas can be moved from the polarizing field of Rb-3Неpolarizer in a special container saving polarization. • We would like to use this possibility having the special movable 3Не-cell and attach this one to ionizer. • This is convenient under accelerator conditions.

  13. 3He-polarized gas container • 1. 3Не transport cell 2. permanent magnet

  14. 3Не polarized beam is injected into an ionization volume restricted by drift Al-tubes system through a 0.1mm capillary. • Capillary gas flow is about 1 cm3/hour or less.

  15. The ionizer is based on the Electron Beam Ion Source (EBIS) in the reflex mode of operation processes and Penning ionizer. • Principle of operation is the 3Не++ion accumulation in the ion trap with the following 10 μs pulse extraction.

  16. Diagram of the of the project ionizer • The electrostatic voltage distribution on drift tubes at accumulation and extraction.

  17. The ion trap is produced by space charge of oscillating electrons in a drift tubes region. In the same place the ionization by an electron impact is accomplished also. • In radial direction the electron cloud is holded by 1 T solenoid magnetic field. This field is needed to exclude 3Не gas depolarization on the walls of drift tubes. • It is scheduled to use Ne-Fe-B permanent magnet for the ionizer.

  18. Project ionizer parameters: • Energy of electrons – 10-20 keV • Effective current – 5-20 A • Length of ion trap – 1 m • 3Не++ ion beam intensity - 2101151011 electronic charge/pulse

  19. The advantages of this type of ionizer - high factor of ionization is not required in other words the 3Не holding time in the ion trap is short, - ultrahigh vacuum is not required in comparison with EBIS ionizer,

  20. Diagram of the polarized D+ Penning ionizer

  21. It is scheduled to accumulate the volume charge of electrons in trap at 10-15 keV electron energy up to • 51011 - 1012 electronic charge • and obtain 3Не++ polarized beam intensity up to • 2101151011 electronic charge/pulse • from the source.

  22. Ionizer consists of a vacuum chamber, Ne-Fe-B-permanent magnet system, electron optical system ( electron gun, electron optical structure and ion optics ), ionizator control system, 20 kV modulator, 10 μs system of a fast extraction and remote control system.

  23. At the exit of the ionizer we have to install a spin-precessor for 3Не++space spin orientation as the concording apparatus with direction of the accelerator magnetic field. • The spin-precessor includes a spherical electrostatic mirror and solenoid

  24. Schematic view of the 3Не++polarized source • 1.electron gun 2.drift tube sections 3. electron reflector 4. ion optical lens 5. movable Faraday cup 6. Nd B Fe permanent magnet 7.turbomolecular pump 8.spherical electrostatic mirror 9. spin precessor solenoid 10. flexible permanent magnet and magnetic shield 11. movable cell 12. capillary.

  25. About 3Не+ depolarization in time of ionization:

  26. At NUCLOTRON parameters we have the following resonances:

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