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

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

Goal is to make an intensive polarized 3He++ beam in the JINR 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.

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

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.

Rb-3Не polarizer 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).

Optical system involves polarizing cube, mirrors, lenses, /4 plates.

It is supposed to use pyrex glass(Corning7740) cells.

Polarizing cell parameters

Volume - 100 cm3 3Не pressure – 1.5-3 bar

Cell temperature - 180-200 оС

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

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%.

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

It is known the polarized gas can be moved from the polarizing field of Rb-3Не polarizer 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.

3He-polarized gas container

1. 3Не transport cell 2. permanent magnet

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.

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.

The electrostatic voltage distribution on drift tubes at accumulation and extraction.

Diagram of the of the project ionizer

10kV

10-1

5 kV

pulse extraction

accumulation

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.

Project ionizer parameters:

Energy of electrons – 10-20 keVEffective current – 5-20 ALength of ion trap – 1 m3Не++ ion beam intensity - 21011 51011

electronic charge/pulse

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,

Diagram of the polarized D+ Penning ionizer

It is scheduled to accumulate the volume charge of electrons in trap at 10-15 keV electron energy up to

51011 - 1012 electronic charge and obtain 3Не++ polarized beam intensity up to

21011 51011 electronic charge/pulse from the source.

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.

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

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.

1000

O15 O

80

300

O95

to LINAC

1 23 4 56

7

8

910

11

to pump

O1

12

About 3Не+ depolarization in time of ionization:

956.0

)99.0(22.3

96.0

)0.1(3.3

10102.3)(

)1(2

21

33

2

2

zationSafePolari

Tx

zationSafePolari

Tx

if

GsHeB

B

Bx

Here

x

xP

c

c

At NUCLOTRON parameters we have the following resonances: