Most ion sources rely on electron impact ionisation

Most ion sources rely on electron impact ionisation. In most (but not all) cases, ion production occurs in a plasma.

Plasma Irving Langmuir proposed the term ‘plasma’ in a paper in 1928 (Proc. Natl Acad. Sci. USA 14 627– 637) to describe a ‘region containing balanced charges of ions and electrons’. 2

PLASMA DENSITY ne – electron density, ni – ion density, n 0 – neutral density. For most ion sources the plasma density is in the range from 1010 -1014 сm-3 At the normal temperature and pressure (Т = 0°С, р=760 torr. ) solids ~ 1023 сm-3; gas density ~1019 сm -3, gas density at the pressure 10 -6 torr ~ 1010 сm -3. PLASMA TEMPERATURE Te – electron temperature Ti – ion temperature T 0 – neutral temperature 11600°K = 1 e. V 3

Quasineutrality Plasma (macroscopically) quasineutral if the number of positive charges per unit volume equals the negative charge density. Electric field of single charges is screened over distances larger than the Debye length Percentage Ionisation (λD – cm; Te – e. V; ne – cm-3) > 10 % → Highly ionised < 1 % → Weakly ionised 4

Debye length vs electron density Potential distribution at the plasma boundary r > λD - quasineutrality 5

Collisions Coulomb logarithm oxygen plasma with an average charge state of 4

Particle motion in the magnetic field F=Bqv = mv /q. B 7

Electron plasma frequency Ion plasma frequency Cyclotron frequency 8

Electron trajectory in (a) homogenous and (b) increasing magnetic field Trajectory of the charged particle confined in the magnetic bottle formed by two solenoids

Magnetic mirror and loss cone The gyromotion of the charged particle produces circulating current The current loop, encompassing an area produces magnetic moment the perpendicular kinetic energy In a simple magnetic mirror structure, particles are confined due to conservation of the magnetic moment

Ionization processes Ionization is possible if Ее > e i

Pj is the binding energy of electrons in the j-th subshell nj is the number of electron in the j-th subshell aj , bj , cj are empirically determined constants

Ion Impact Ionization cross sections for Ar as a function of energy for ionizing collisions with electrons, protons, and photons

Потери ионов в плазме. (рекомбинация)

Radiative Recombination (RR)

Charge Exchange перезарядка Charge exchange with neutrals is dominant and the main loss process for highly charged ions. q [cm 2] P 1 - first ionization potential of the neutral particle [e. V]

Conditions for the creation of multiply charged ions Te ~ (2 ÷ 5) φ n 0 << ne FLNR Ion Sources Group

Arthur Dempster Electron Bombardment Source (1916)

Manfred von Ardenne Plasmatron (late 1940 s)

CERN Duoplasmatron 300 m. A protons 150 μs pulses at 1 Hz

OVERVIEW OF THE FLNR (JINR) CYCLOTRONS WITH ECR ION SOURCES U 400 M + DECRIS-2 U 400 + DECRIS-2 M NEW CYCLOTRONS CI-100 + DECRIS-SC DECRIS-2 M ECR test bench DRIBs ECR 4 M, DECRIS-SC 2 DECRIS-4 DRIBs DECRIS-2 23 MASHA

Penning or Philips Ion Gauge Gas Pressure -> 1 mbar Arc Voltage ~1 k. V Arc Current 0. 1 -> 50 A Magnetic Field >0. 1 T Cathode can be Hot or Cold Electrons are accelerated by the arc voltage across th cathode sheath layer Magnetic field stops cathode electrons reaching the anode (>0. 1 T required). Some electrons strike the anticathode. Otherwise they may oscillate in the Penning Trap and ionise the gas. Electrons go to the anode by diffusion processes, plasma oscillations and the plasma-anode potential. FLNR Ion Sources Group

Б. Н. Маков Препринт ИАЭ – 1051. Москва 1966 Авторское свидетельство № 16020. 25. 01. 1950 N+ 6 m. A N 2+ 9. 5 m. A N 3+ 6. 9 m. A N 4+ 1. 3 m. A N 5+ 0. 1 m. A

PIG ion sources with solid material feed for the U-300 cyclotron. Sputtering Evaporation Ca ion current, m. A 1+ 2+ 3+ 4+ 5+ 6+ 7. 8 32 33 29 12 3 1+ 2+ 3+ 4+ 5+ 6+ 3 23 22 14 4. 5 1 FLNR Ion Sources Group

Cross-section of the PIG ion source for the U-400 cyclotron

General view of the PIG ion source for the U-300 cyclotron

PIG ion source for the U-400 cyclotron FLNR Ion Sources Group

Vertical PIG ion source for the U-400 M cyclotron

FLNR Ion Sources Group