ION SOURCES FOR MEIC

1
ION SOURCES FOR MEIC

• Vadim Dudnikov
• Muons, Inc., Batavia, IL

Mini-Workshop for MEIC Ion Complex Design,
Jefferson Lab. Jan 27, 2011
2
Abstract

• Ion sources for production of polarized negative
  and positive light and heavy ions will be
  considered. Universal Atomic bean ion source can
  be used for generation of polarized H-, H, D-,
  D , He, Li ions with high polarization and
  high brightness.
• Generation of multicharged ions, injection and
  beam instabilities will be considered.
• References
• Belov A.S., Dudnikov V.,et. al., NIM A255, 442
  (1987).
• Belov A.S., Dudnikov V.,et al., . NIM A333, 256
  (1993).
• Belov A.S, Dudnikov V., et. al., RSI, 67, 1293
  (1996).
• Belchenko Yu. I. , Dudnikov V., et. al., RSI,
  61, 378 (1990)
• Belov A.S. et. al., NIM, A239, 443 (1985).
• Belov A.S. et. al., 11 th International
  Conference on Ion Sources, Caen, France,
• September 12-16, 2005
• A.S. Belov, PSTP-2007, BNL, USA A.S. Belov,
  DSPIN2009, DUBNA, Russia
• A. Zelenski, PSTP-2007, BNL, USA DSPIN2009,
  DUBNA, Russia

3
EIC Design Goals

• Energy
• Center-of-mass energy between 20 GeV and 90 GeV
• energy asymmetry of 10,
• ? 3 GeV electron on 30 GeV proton/15 GeV/n
  ion up to
• 9 GeV electron on 225 GeV proton/100
  GeV/n ion
• Luminosity
• 1033 up to 1035 cm-2 s-1 per interaction point
• Ion Species
• Polarized H, D, 3He, possibly Li
• Up to heavy ion A 208, all striped
• Polarization
• Longitudinal polarization at the IP for both
  beams
• Transverse polarization of ions
• Spin-flip of both beams
• All polarizations gt70 desirable

Yuhong Zhang For the ELIC Study Group Jefferson
Lab
4
ELIC Design Goals

• Energy
• Wide CM energy range between 10 GeV and 100 GeV
• Low energy 3 to 10 GeV e on 3
  to 12 GeV/c p (and ion)
• Medium energy up to 11 GeV e on 60 GeV
  p or 30 GeV/n ion
• and for future upgrade
• High energy up to 10 GeV e on 250
  GeV p or 100 GeV/n ion
• Luminosity
• 1033 up to 1035 cm-2 s-1 per collision point
• Multiple interaction points
• Ion Species
• Polarized H, D, 3He, possibly Li
• Up to heavy ion A 208, all stripped
• Polarization
• Longitudinal at the IP for both beams, transverse
  of ions
• Spin-flip of both beams
• All polarizations gt70 desirable
• Positron Beam desirable
• 
  
  Andrew Hutton

5
MEIC Low and Medium Energy
6
MEIC Detailed Layout
7
ELIC High Energy Staging
Circumference m 1800
Radius m 140
Width m 280
Length m 695
Straight m 306
Serves as a large booster to the full energy
collider ring
Stage Stage Max. Energy (GeV/c) Max. Energy (GeV/c) Ring Size (m) Ring Size (m) Ring Type Ring Type IP
p e p e p e
Low 12 5 (11) 630 630 Warm Warm 1
Medium 60 5 (11) 630 630 Cold Warm 2
High 250 10 1800 1800 Cold Warm 4
8
ELIC Main Parameters
Beam Energy GeV 250/10 150/7 60/5 60/3 60/3 12/3
Collision freq. MHz 499 499
Particles/bunch 1010 1.1/3.1 0.5/3.25 0.74/2.9 1.1/6 1.1/6 0.47/2.3
Beam current A 0.9/2.5 0.4/2.6 0.59/2.3 0.86/4.8 0.86/4.8 0.37/2.7
Energy spread 10-4 3 3 3 3 3 3
RMS bunch length mm 5 5 5 5 5 50
Horiz.. emit., norm. µm 0.7/51 0.5/43 0.56/85 0.8/75 0.8/75 0.18/80
Vert. emit. Norm. µm 0.03/2 0.03/2.87 0.11/17 0.8/75 0.8/75 0.18/80
Horizontal beta-star mm 125 75 25 25 25 5
Vertical beta-star mm 5 5 5 5 5 5
Vert. b-b tune shift/IP 0.01/0.1 0.015/.05 0.01/0.03 .015/.08 .015/.08 .015/.013
Laslett tune shift p-beam 0.1 0.1 0.1 0.054 0.054 0.1
Peak Lumi/IP, 1034 cm-2s-1 11 4.1 1.9 4.0 4.0 0.59
High energy
Low energy
Medium energy
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Achieving High Luminosity

• MEIC design luminosity
• L 4x1034 cm-2 s-1 for medium energy (60
  GeV x 3 GeV)
• Luminosity Concepts
• High bunch collision frequency (0.5 GHz, can be
  up to 1.5 GHz)
• Very small bunch charge (lt3x1010 particles per
  bunch)
• Very small beam spot size at collision points
  (ßy 5 mm)
• Short ion bunches (sz 5 mm)
• Keys to implementing these concepts
• Making very short ion bunches with small
  emittance
• SRF ion linac and (staged) electron cooling
• Need crab crossing for colliding beams
• Additional ideas/concepts
• Relative long bunch (comparing to beta) for very
  low ion energy
• Large synchrotron tunes to suppress
  synchrotron-betatron resonances
• Equal (fractional) phase advance between IPs

10
Forming a High-Intensity Ion Beam
Stacking proton beam in ACR
Circumference m 100
Energy/u GeV 0.2 -0.4
Cooling electron current A 1
Cooling time for protons ms 10
Stacked ion current A 1
Norm. emit. After stacking µm 16
Energy (GeV/c) Cooling Process
Source/SRF linac 0.2 Full stripping
Prebooster/Accumulator-Ring 3 DC electron Stacking/accumulating
Low energy ring (booster) 12 Electron RF bunching (for collision)
Medium energy ring 60 Electron RF bunching (for collision)

• Stacking/accumulation process
• Multi-turn (20) pulse injection from SRF linac
  into the prebooster
• Damping/cooling of injected beam
• Accumulation of 1 A coasted beam at space charge
  limited emittance
• Fill prebooster/large booster, then acceleration
• Switch to collider ring for booster, RF bunching
  staged cooling

11
Stacking polarized proton beam over space charge
limit in pre-booster

• To minimize the space charge impact on transverse
  emittance, the circular painting technique can
  be used at stacking. Such technique was
  originally proposed for stacking proton beam in
  SNS 7. In this concept, optics of booster ring
  is designed strong coupled in order to realize
  circular (rotating) betatron eigen modes of two
  opposite helicities. During injection, only one
  of two circular modes is filled with the injected
  beam. This mode grows in size (emittance) while
  the other mode is not changed. The beam sizes
  after stacking, hence, tune shifts for both modes
  are then determined by the radius of the filled
  mode. Thus, reduction of tune shift by a factor
  of k (at a given accumulated current) will be
  paid by increase of the 4D emittance by the same
  factor, but not k2.

Stacking proton beam in pre-booster over space
charge limit 1 painting resonators 2, 3
beam raster resonators 4 focusing triplet 5
stripping foil
Circular painting principle transverse velocity
of injected beam is in correlation with vortex of
a circular mode at stripping foil
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Overcoming space charge at stacking
Stacking parameters Unit Value
Beam energy MeV 200
H- current mA 2
Transverse emittance in linac µm .3
Beta-function at foil cm 4
Focal parameter m 1
Beam size at foil before/after stacking mm .1/.7
Beam radius in focusing magnet after stacking cm 2.5
Beam raster radius at foil cm 1
Increase of foil temperature oK lt100
Proton beam in pre-booster after stacking
Accumulated number of protons 2 x1012
Increase of transverse temperature by scattering 10
Small/large circular emittance value µm .3/15
Regular beam size around the ring cm 1
Space charge tune shift of a coasting beam .02
This reduction of the 4D emittance growth at
stacking 1-3 Amps of light ions is critical for
effective use of electron cooling in collider
ring.
13
Future Accelerator RD

• Focal Point 3 Forming high-intensity short-bunch
  ion beams cooling
• sub tasks Ion bunch dynamics and space charge
  effects (simulations)
• Electron cooling dynamics (simulations)
• Dynamics of cooling electron bunch in ERL
  circulator ring
• Led by Peter Ostroumov (ANL)
• Focal Point 4 Beam-beam interaction
• sub tasks Include crab crossing and/or
  space charge
• Include multiple bunches and
  Interaction Points
• Led by Yuhong Zhang and Balsa Terzic (JLab)
• Additional design and RD studies
• Electron spin tracking, ion source
  development
• Transfer line design

14
MEIC (e/A) Design Parameters
Ion Max Energy (Ei,max) Luminosity / n (7 GeV x Ei,max) Luminosity / n (3 GeV x Ei,max/5)
(GeV/nucleon) 1034 cm-2 s-1 1033 cm-2 s-1
Proton 150 7.8 6.7
Deuteron 75 7.8 6.7
3H1 50 7.8 6.7
3He2 100 3.9 3.3
4He2 75 3.9 3.3
12C6 75 1.3 1.1
40Ca20 75 0.4 0.4
208Pb82 59 0.1 0.1
Luminosity is given per unclean per IP
15
High polarization importance

• High beam polarization is essential to the
  scientific productivity of a collider.
• Techniques such as charge-exchange injection and
  use of Siberian snakes allow acceleration of
  polarized beams to very high energies with little
  or no polarization loss.
• The final beam polarization is then determined by
  the source polarization. Therefore, ion sources
  with performances exceeding those achieved today
  are key requirements for the development of the
  next generation high-luminosity high-polarization
  colliders.

16
Existing Sources Parameters

• Universal Atomic Beam Polarized Sources (most
  promising, less expensive for repeating)
• IUCF/INR CIPIOS pulse width up to 0.5 ms
  repetition 2Hz (Shutdown 8/02 Rebuilded in
  Dubna)
• Peak Intensity H-/D- 2.0 mA/2.2 mA Max
  Pz/Pzz 85 to 91 Emittance (90) 1.2 pmmmrad.
• INR Moscow pulse width gt 0.1 ms repetition 5Hz
  (Test Bed since 1984)
• Peak Intensity H/H- 11 mA/4 mA Max Pz
  80/95
• Emittance (90) 1.0 pmmmrad/ 1.8
  pmmmrad
• Unpolarized H-/D- 150/60 mA.
• OPPIS/BNL H- only Pulse Width 0.5 ms (in
  operation)
• Peak Intensity up to 1.6 mA Max Pz 85 of
  nominal
• Emittance (90) 2.0 pmmmrad.

17
Polarization detected

• Proton polarization up to 95 was measured with
  low plasma ion flux (5mA D) ?
• Polarization of 80 has been recorded for high
  ion flux in the storage cell
  ?

18
ABPIS basis

• Polarized ions are produced in polarized ion
  sources via several steps process
• polarization of neutral atoms (atomic beam method
  or optical pumping)
• Conversion of polarized neutral atoms into
  polarized ions (ionization by electron impact,
  electron impact charge-exchange, charge
  exchange, nearly resonant charge-exchange )
• Nearly resonant charge-exchange processes have
  large cross sections. This is base for high
  efficiency of polarized atoms conversion into
  polarized ions.

19
ABIS with Resonant Charge Exchange Ionization

• INR Moscow
• H0? D ?H? D0
• D0? H ?D? H0
• s 5 10-15cm2
• H0? D-?H-? D0
• D0? H-?D-? H0
• s 10-14cm2

Limitations Pumping is high Extraction voltage
Uexlt25 kV.
A. Belov, DSPIN2009
20
Atomic Beam Polarized Ion source

• In the ABS, hydrogen or deuterium atoms are
  formed by dissociation of molecular gas,
  typically in a RF discharge. The atomic flux is
  cooled to a temperature 30K - 80K by passing
  through a cryogenically cooled nozzle. The atoms
  escape from the nozzle orifice into a vacuum and
  are collimated to form a beam. The beam passes
  through a region with inhomogeneous magnetic
  field created by sextupole magnets where atoms
  with electron spin up are focused and atoms with
  electron spin down are defocused.Nuclear
  polarization of the beam is increased by inducing
  transitions between the spin states of the atoms.
  The transition units are also used for a fast
  reversal of nuclear spin direction without change
  of the atomic beam intensity and divergence.
  Several schemes of sextupole magnets and RF
  transition units are used in the hydrogen or
  deuterium ABS. For atomic hydrogen, a typical
  scheme consists of two sextupole magnets followed
  by weak field and strong field RF transition
  units. In this case, the theoretical proton
  polarization will reach Pz -1. Switching
  between these two states is performed by
  switching between operation of the weak field and
  the strong field RF transition units. For atomic
  deuterium, two sextupole magnets and three RF
  transitions are used in order to get deuterons
  with vector polarization of Pz -1 and tensor
  polarization of Pzz 1, -2Different methods for
  ionizing polarized atoms and their conversion
  into negative ions were developed in many
  laboratories. The techniques depended on the type
  of accelerator where the source is used and the
  required characteristics of the polarized ion
  beam (see ref. 2 for a review of current
  sources).For the pulsed atomic beam-type
  polarized ion source (ABPIS) the most efficient
  method was developed at INR, Moscow 3-5.
  Polarized hydrogen atoms with thermal energy are
  injected into a deuterium plasma where polarized
  protons or negative hydrogen ions are formed due
  to the quasi-resonant charge-exchange reaction

21
Ionization of Polarized Atoms

• Resonant charge-exchange reaction is charge
  exchange between atom and ion of the same atom
  A0 A ?A A0
• Cross -section is of order of 10-14 cm2 at low
  collision energy
• Charge-exchange between polarized atoms and
  ions of isotope relative the polarized atoms to
  reduce unpolarized background
• W. Haeberli proposed in 1968 an ionizer with
  colliding beams of 1-2 keV D- ions and thermal
  polarized hydrogen atoms
• H0? D-?H-? D0

22
Cross-section vs collision energy for process H?
H0 ? H0 H? ? 10-14 cm2 at 10eV collision
energy
23
Cross-section vs collision energy for process
He He0 ? He0 He? 5?10-16 cm2 at
10eV collision energy
24
(No Transcript)
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Destruction of Negative Hydrogen Ions in Plasma

• H? e ? H0 2e ? 4?10-15 cm2
• H? D ? H0 D0 ? 2?10-14
  cm2
• H? D0 ? H0 D ? ?
  10-14 cm2
• H? D2 ? H0 D2 e ? 2?10-16 cm2
• H? D0 ? HD0 e ? 10-15 cm2

26
Details of ABIS with Resonant Charge Exchange
Ionization
27
Resonance Charge Exchange Ionizer with Two Steps
Surface Plasma Converter
Jet of plasma is guided by magnetic field to
internal surface of cone fast atoms bombard a
cylindrical surface of surface plasma converter
initiating a secondary emission of negative ions
increased by cesium adsorption.
28
Schematic of Negative Ion Formation on the
Surface (Fgts) (formation of secondary ion
emission Michail Kishinevsky, Sov. Phys. Tech.
Phys, 45,1975)

• Affinity lever S is lowering by image forces
  below Fermi level during particle approaching to
  the surface
• Electron tunneling to the affinity level
• During particle moving out of surface electron
  affinity level S go up and the electron will
  tunneling back to the Fermi level
• Back tunneling probability w is high at slow
  moving (thermal) and can be low for fast moving
  particles Ionization coefficient ß- can be high
  0.5 for fast particles with Slt f

29
Coefficient of Negative Ionization As Function of
Work Function and Particle Speed
Kishinevsky M. E., Sov. Phys. Tech. Phys., 48
(1978), 773 23 (1978), 456
30
Probability of H- Emission as Function of Work
Function (Cesium Coverage)
The surface work function decreases with
deposition of particles with low ionization
potential and the probability of secondary
negative ion emission increases greatly from the
surface bombarded by plasma particles.
Dependences of work function on surface cesium
concentration for different W crystalline
surfaces (1-(001) 2-(110) 3-(111) 4-(112),
left scale) and 5-relative yield Y of H-
secondary emission for surface index (111), right
scale
31
Production of Surfaces with Low Work Function
(Cesium Coverage)
The surface work function decreases with
deposition of particles with low ionization
potential (CS) and the probability of secondary
negative ion emission increases greatly from the
surface bombarded by plasma particles.
Dependences of desorption energy H on surface
Cesium concentration N for different W
crystalline surfaces 1-(001) 2-(110) 3-(111)
4-(112).

• The work function in the case of cesium
  adsorption in dependence upon the ratio of sample
  temperature T to cesium-tank temperature TCs for
  collectors of
• a molybdenum polycrystalline with a tungsten
  layer on the surface,
• (110) molybdenum,
• a molybdenum polycrystalline,
• an LaB6 polycrystalline.

32
Probability of particles and energy reflection
for low energy H particles
33
INR ABIS Oscilloscope Track of Polarized H- ion
Polarized H- ion current 4 mA (vertical
scale-1mA/div) Unpolarized D- ion current 60 mA
(10mA/div)
A. Belov
34
ABIS polarized H-/D- source in Institute of
Nuclear Research, Troitsk, Russia
A possible Prototype of Universal Atomic Beam
Polarized ion source (H-, D-, Li-, He, H, D,
Li) left- solenoid of resonant change
exchange Ionizer right- atomic beam source with
RF dissociator.
35
Main Systems of INR ABIS with Resonant Charge
Exchange Ionization
36
Main Systems of INR ABIS with Resonant Charge
Exchange Ionization
37
Main Systems of INR ABIS with Resonant Charge
Exchange Ionization
38
Schematic Diagram of IUCF APPIS with Resonant
Charge Exchange Ionization
39
The pulsed polarized negative ion source
(CIPIOS) multi-milliampere beams for injection
into the Cooler Injector Synchrotron (CIS).
Schematic of ion source and LEBT showing the
entrance to the RFQ.
The beam is extracted from the ionizer toward the
ABS and is then deflected downward with a
magnetic bend and towards the RFQ with an
electrostatic bend. This results in a nearly
vertical polarization at the RFQ entrance.
Belov, Derenchuk, PAC 2001
40
Plans of Work

• Review of existing versions of ABPIS components
  for choosing an optimal combinations
• Review production of highest polarization
• General design of optimal ABPIS
• Estimation availability of components and
  materials
• Estimation of project cost and RD schedule.
• INR, A. Belov
• BINP, D. Toporkov, V. Davydenko,
• BNL, A. Zelenski,
• IUCF, Dubna, V. Derenchuk, A. Belov,
• COSY/Julich, R. Gebel.

41
Components of IUCF ABPIS (sextupole, ionization
solenoid, RF dissociator, bending magnet, Arc
discharge plasma source)
42
Arc Discharge Ion Source
Dimov BINP 1962
Ionization 99.9 , dissociation 99, transverse
ion temperature 0.2 eV multi-slit extraction.
43
Long Pulse Arc-discharge Plasma Generator with
Lab6 Cathode
Version with one LaB6 disc
Version with several LaB6 discs
Metal-ceramic discharge channel is developed
44
Fast, compact gas valve, 0.1ms, 0.8 kHz

• 1 -current feedthrough
• 2- housing
• 3-clamping screw
• 4-coil
• 5- magnet core
• 6-shield
• 7-screw
• 8-copper insert
• 9-yoke
• 10-rubber washer-
• returning springs
• 11-ferromagnetic plate-
• armature
• 12-viton stop
• 13-viton seal
• 14-sealing ring
• 15-aperture
• 16-base
• 17-nut.

45
Fast, Compact Cesium Supply

• Cesium oven with cesium pellets and press-form
  for pellets preparation.
• 37-cesium oven body
• 38- oven assembly
• 39- heater
• 40-thermal shield
• 41- heart connector
• 42-wire with connector
• 43- plug with copper gasket
• 44-press nut
• 45- cesium pellets
• 46- press form body
• 47- press form piston
• 48- press form bolt.

46
Injection of Background Gas at Different Position
ATTENUATION OF THE BEAM IS DEPENDENT FROM THE
POSITION OF THE GAS INJECTIOJN
NOT MANY EXPERIMENTAL DATA AVAILABLE Remote fine
positioning now available
D.K.Toporkov, PSTP-2007, BNL, USA
INJECTION OF BACKGROUND GAS AT DIFFERENT POSITION
47
Cryogenic Atomic Beam Source
BINP Atomic Beam Source with Superconductor
Sextupoles (2 1017 a/s)
Two group of magnets S1, S2 (tapered magnets)
and S3, S4, S5 (constant radius) driven
independently, 200 and 350 A respectively
Cryostat
Liquid nitrogen
48
Focusing Magnets
Permanent magnets B1.6 T Superconducting B4.8 T

• DW pa2 pmB/kT
• B 1.6 T DW 1.510-2 sr a
  0.07 rad
• B 4.8 T DW 4.510-2 sr a
  0.21 rad

49
BNL Polarimeter vacuum system

• The H-jet polarimeter includes three major parts
  polarized Atomic Beam Source (ABS), scattering
  chamber, and Breit-Rabi polarimeter.
• The polarimeter axis is vertical and the recoil
  protons are detected in the horizontal plane.
• The common vacuum system is assembled from nine
  identical vacuum chambers, which provide nine
  stages of differential pumping.
• The system building block is a cylindrical vacuum
  chamber 50 cm in diameter and of 32 cm length
  with the four 20 cm (8.0) ID pumping ports.
• 19 TMP , 1000 l/s pumping speed for hydrogen.

50
Proposed Sources Parameters

• Universal Atomic Beam Polarized Sources (most
  promising, less expensive for repeating)
• pulse width up to 0.5 ms repetition up to 5 Hz
• Peak Intensity H-/D- 4.0 mA/4 mA N1013 p/pulse
• Max Pz/Pzz up to 95
• Emittance (90) 1.0 pmmmrad/1.8 pmmmrad
• Unpolarized H-/D- 150/60 mA.

51
General Polarized RHIC OPPIS Injector Layout
ECR electron-cyclotron resonance proton source
in SCS SCS superconducting solenoid Na-jet
sodium-jet ionizer cell LSP Lamb-shift
polarimeter M1, M2 dipole bending magnets.
52
Advanced OPPIS with High Brightness BINP Proton
Injector
1- proton source 2- focusing solenoid 3-
hydrogen neutralizing cell 4- superconducting
solenoid 5- helium gas ionizing cell 6-
optically pumped Rb vapor cell 7- deflecting
plates 8- Sona transition region 9- sodium
ionizer cell 10- pumping lasers PV-pulsed gas
valves.
53
Realistic Extrapolation for Future

• ABS/RX Source
• H- 10 mA, 1.2 pmmmrad (90), Pz 95
• D- 10 mA, 1.2 pmmmrad (90), Pzz 95
• OPPIS
• H- 40 mA, 2.0 pmmmrad (90), Pz 90
• H 40 mA, 2.0 pmmmrad (90), Pz 90
• Polarization in ABS/RX Source is higher
  because ionization of polarized atoms is very
  selective and molecules do not decrease
  polarization.

54
3He Ion source with Polarized 3He Atoms and
Resonant Charge Exchange Ionization
A.S. Belov, PSTP-2007, BNL, USA
55
Cross-section vs collision energy for process
He He0 ?He0 Hes510-16cm2 at 10eV
collision energy
A.S. Belov, PSTP-2007, BNL, USA
56
Polarized 6Li Optionsand other elements with
low ionization potential

• Existing Technology
• Create a beam of polarized atoms using ABS
• Ionize atoms using surface ionization on an 1800
  K Tungsten (Rhenium) foil singly charged ions
  of a few 10s of µA
• Accelerate to 5 keV and transport through a Cs
  cell to produce negative ions. Results in a few
  hundred nAs of negative ions (can be increased
  significantly in pulsed mode of operation)
• Investigate alternate processes such as
  quasiresonant charge exchange, EBIS ionizer
  proposal or ECR ionizer. Should be possible to
  get 1 mA (?) fully stripped beam with high
  polarization
• Properties of 6Li Bc 8.2 mT, m/mN 0.82205, I
  1
• Bc critical field, m/mN magnetic moment,
  I nuclear spin

57
Multicharged Ion Beam from Advanced ECR Ion
Sources
58

• Advantages of the new pre-injector
• Simple, modern, low maintenance
• Lower operating cost
• Can produce any ions (noble gases, U, He3?)
• Higher Au injection energy into Booster
• Fast switching between species, without
• constraints on beam rigidity
• Short transfer line to Booster (30 m)
• Few-turn injection
• No stripping needed before the Booster,
• resulting in more stable beams
• Expect future improvements to lead to
• higher intensities

Stripper
J. Alessi, PSTP-2007, BNL, USA
59
Example of Using Ion Stripping in Acceleration
and Injection (RHIC BNL)
60
Performance of the Preinjectorwith EBIS and RFQ
Linac (BNL)

• Species He to U
• Intensity (examples) 2.7 x 109 Au32 / pulse
• 4 x 109 Fe20 / pulse
• 5 x 1010 He2 / pulse
• Q/m 0.16, depending on ion species
• Repetition rate 5 Hz
• Pulse width 10-40 µs
• Switching time between species 1 second
• Output energy 2 MeV/amu (enough for stripping
  Au32 )

61
Principle of EBIS Operation

• Radial trapping of ions by the space charge of
  the electron beam.
• Axial trapping by applied electrostatic
  potentials on electrode at ends of trap.
• The total charge of ions extracted per pulse is
  (0.5 0.8) x ( electrons in the trap)
• Ion output per pulse is proportional to the trap
  length and electron current.
• Ion charge state increases with increasing
  confinement time.
• Charge per pulse (or electrical current)
  independent of species or charge state!

62
Performance Requirements of BNL EBIS
Species He to U
Output (single charge state) 1.1 x 1011 charges / pulse
Intensity (examples) 3.4 x 109 Au32 / pulse (1.7 mA) 5 x 109 Fe20 / pulse (1.6 mA) gt 1011 He2 / pulse (gt 3.0 mA)
Q/m 0.16, depending on ion species
Repetition rate 5 Hz
Pulse width 10 - 40 µs
Switching time between species 1 second
Output emittance (Au32) lt 0.18 ? mm mrad,norm,rms
Output energy 17 keV/amu
63
LEBT/Ion Source Region
64
ECR 28 GHz Heavy Ion Source Region
290 MY
65
BNL RFQ Pre-injector Development
66
History of Surface Plasma Source development
(J.Peters, RSI, v.71, 2000)
Cesium patent V. Dudnikov. The Method for
Negative Ion Production, SU Author Certificate,
C1.H013/04, No. 411542, Application filed at 10
Mar., 1972, granted 21 Sept,1973.
Invention formula Enhancement
of negative ion production comprising admixture
into the discharge a substance with a low
ionization potential, such as cesium.
67
Production of highest polarization and reliable
operation are main goals of ion sources
development in the Jefferson Lab

• Development of Universal Atomic Beam Polarized
  Sources (most promising, less expensive for
  repeating) .
• It is proposed to develop one universal H-/D-/He
  ion source design which will synthesize the most
  advanced developments in the field of polarized
  ion sources to provide high current, high
  brightness, ion beams with greater than 90
  polarization, good lifetime, high reliability,
  and good power efficiency.
• The new source will be an advanced version of
  an atomic beam polarized ion source (ABPIS) with
  resonant charge exchange ionization by negative
  ions, which are generated by surface-plasma
  interactions.

68
Ion Sources for Electron Ion Colliders

• Optimized versions of existing polarized ion
  sources (ABPS and OPPIS) and advanced injection
  methods are capable to delivery ion beam
  parameters necessary for high luminosity of EIC.
• Combination of advanced elements of polarized ion
  source and injection system are necessary for
  reliable production of necessary beams
  parameters.
• Advanced control of instabilities should be
  developed for support a high collider luminosity.

69
History of e-p instability observation
Was presented in Cambridge PAC67 but only INP was
identified as e-p instability
From F. Zimmermann report
70
Simulation of electron cloud accumulation and e-p
instability development (secondary ion/electron
emission) Penning discharge
71
Plasma generators for space charge compensation
1- circulating proton beam 2- magnetic poles 3-
filaments, (field emission) electron sources 4-
grounded fine mesh 5- secondary emission plate
with a negative potential.
Electrons e emitted by filaments 3 are
oscillating between negative plates 5 with a high
secondary emission for electron multiplication. A
beam density and plasma density must be high
enough for selfstabilization of e-p instability
(second threshold). Secondary ion accumulation
is important for selfstabilization of e-p
instability.
72
Beam accumulation with a plasma generator on and
off
on
off
on
off