Download A proposal of a polarized 3 He ++ ion source with penning ionizer

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.
Diagram of the of the project ionizer
pulse extraction
10kV
10-15 kV
accumulation
 The electrostatic voltage distribution on drift tubes at accumulation and extraction.
 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 keV
Effective current – 5-20 A
Length of ion trap – 1 m
3Не++ ion beam intensity - 21011  51011
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

51011 - 1012 electronic charge
 and obtain 3Не++ polarized beam intensity up to

21011  51011 electronic charge/pulse
 from the source.
 Ionizer consists of a vacuum chamber, Ne-Fe-Bpermanent 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
to LINAC
10
11
9
300
2 12
to pump
6 3
4
5
O15
O80
1
O95
O1
1000
8
7

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.
About 3Не+ depolarization in time of ionization:
1 2x2
P
2(1  x 2 )
Here
B
x
Bc
Bc ( 3He )  3.102 103 Gs
if
x  3.3  (1.0T )
SafePolarization  0.96
x  3.22  (0.99T )
SafePolarization  0.956
At NUCLOTRON parameters we have the following resonances: