Transcript ION SOURCES FOR MEIC Vadim Dudnikov Muons, Inc., Batavia, IL 1

ION SOURCES FOR MEIC
Vadim Dudnikov
Muons, Inc., Batavia, IL
1
Mini-Workshop for MEIC Ion Complex Design, Jefferson Lab. Jan 27, 2011
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).
•
Bel’chenko Yu. I. , Dudnikov V., et. al., RSI, 61, 378 (1990)
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Belov A.S. et. al., NIM, A239, 443 (1985).
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Belov A.S. et. al., 11 th International Conference on Ion Sources, Caen, France,
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September 12-16, 2005;
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A.S. Belov, PSTP-2007, BNL, USA; A.S. Belov, DSPIN2009, DUBNA, Russia;
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A. Zelenski, PSTP-2007, BNL, USA; DSPIN2009, DUBNA, Russia
EIC Design Goals
 Energy
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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
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Polarized H, D, 3He, possibly Li
Up to heavy ion A = 208, all striped
 Polarization
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•
•
•
Longitudinal polarization at the IP for both beams
Transverse polarization of ions
Spin-flip of both beams
All polarizations >70% desirable
 Positron Beam desirable
Yuhong Zhang
For the ELIC Study Group
Jefferson Lab
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 >70% desirable
Positron Beam desirable
Andrew Hutton
MEIC: Low and Medium Energy
Three compact rings:
• 3 to 11 GeV electron
• Up to 12 GeV/c proton (warm)
• Up to 60 GeV/c proton (cold)
MEIC: Detailed Layout
polarimetry
ELIC: High Energy & Staging
Serves as a large booster to
the full energy collider ring
Circumference
m
1800
Radius
m
140
Width
m
280
Length
m
695
Straight
m
306
p
prebooster
SRF
Linac
Ion
Sources
p
p
electron ring
Interaction Point
MEIC
collider
ring
ELIC
collider
ring
e
e
Ion ring
Vertical crossing
e
Stage
injector
Max.
Energy
(GeV/c)
p
e
Low
12
5 (11)
Medium
60
High
250
12 GeV CEBAF
Ring Size
(m)
p
e
Ring Type
IP
#
p
e
630
Warm
Warm
1
5 (11)
630
Cold
Warm
2
10
1800
Cold
Warm
4
ELIC Main Parameters
Beam Energy
GeV
Collision freq.
MHz
Particles/bunch
1010
1.1/3.1
0.5/3.25
Beam current
A
0.9/2.5
0.4/2.6
Energy spread
10-4
RMS bunch length
mm
5
5
Horiz.. emit., norm.
μm
0.7/51
Vert. emit. Norm.
μm
Horizontal beta-star
mm
Vertical beta-star
mm
Vert. b-b tune
shift/IP
250/10
150/7
60/5
60/3
12/3
0.74/2.9
1.1/6
0.47/2.3
0.59/2.3
0.86/4.8
0.37/2.7
5
5
50
0.5/43
0.56/85
0.8/75
0.18/80
0.03/2
0.03/2.87
0.11/17
0.8/75
0.18/80
125
75
25
25
5
499
~3
5
0.01/0.1
0.015/.05
0.01/0.03
.015/.08
.015/.013
Laslett tune shift
p-beam
0.1
0.1
0.1
0.054
0.1
Peak Lumi/IP, 1034
cm-2s-1
11
4.1
1.9
4.0
0.59
High energy
Medium energy
Low energy
Achieving High Luminosity
MEIC design luminosity
L~ 4x1034 cm-2 s-1
for medium energy (60 GeV x 3 GeV)
Luminosity Concepts
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•
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High bunch collision frequency (0.5 GHz, can be up to 1.5 GHz)
Very small bunch charge (<3x1010 particles per bunch)
Very small beam spot size at collision points (β*y ~ 5 mm)
Short ion bunches (σz ~ 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
Forming a High-Intensity Ion Beam
Stacking proton beam in ACR
low energy ring cooling
SRF Linac
source
pre-boosterAccumulator ring
Medium energy
collider ring
Energy (GeV/c)
Circumference
Energy/u
Cooling electron current
Cooling time for protons
Stacked ion current
Norm. emit. After stacking
Cooling
m
GeV
A
ms
A
µm
100
0.2 -0.4
1
10
1
16
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
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.
Circular painting principle: transverse
velocity of injected beam is in correlation
with vortex of a circular mode at stripping
foil
Stacking proton beam in
pre-booster over space
charge limit:
1 – painting resonators
2, 3 – beam raster
resonators
4 – focusing triplet
5 – stripping foil
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
<100
Proton beam in pre-booster after stacking
2 x1012
Accumulated number of protons
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.
Future Accelerator R&D
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:
sub tasks:
Beam-beam interaction
Include crab crossing and/or space charge
Include multiple bunches and Interaction Points
Led by Yuhong Zhang and Balsa Terzic (JLab)
Additional design and R&D studies
Electron spin tracking, ion source development
Transfer line design
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
3H+1
50
7.8
6.7
3He+2
100
3.9
3.3
4He+2
75
3.9
3.3
12C+6
75
1.3
1.1
40Ca+20
75
0.4
0.4
208Pb+82
59
0.1
0.1
* Luminosity is given per unclean per IP
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 highluminosity high-polarization colliders.
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 π·mm·mrad.
•
INR Moscow: pulse width > 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 π·mm·mrad/ 1.8 π·mm·mrad;
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 π·mm·mrad.
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

A.S. Belov, PSTP-2007, BNL, USA
September 10-14, 2007
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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.
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September 10-14, 2007
ABIS with Resonant Charge
Exchange Ionization
INR Moscow
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H0↑+ D+ ⇒H+↑+ D0
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D0↑+ H+ ⇒D+↑+ H0
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σ~ 5 10-15cm2
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H0↑+ D−⇒H−↑+ D0
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D0↑+ H−⇒D−↑+ H0
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σ~ 10-14cm2
Limitations:
Pumping is high;
Extraction voltage
Uex<25 kV.
A. Belov, DSPIN2009
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, -2
Different 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:
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
Cross-section vs collision energy for
process
H + H0  H0 + H
 = 10-14 cm2 at ~10eV collision energy
Cross-section vs collision energy
for process
He++ + He0  He0 + He++
 = 510-16 cm2 at ~10eV collision energy
Schematic diagram of the ionizer
for polarized negative hydrogen ions production
Destruction of Negative Hydrogen
Ions in Plasma
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H + e 
H  + D+ 
H  + D0 
H  + D2 
H + D0 
H0 + 2e
H 0 + D0
H0 + D 
H 0 + D2 + e
HD0 + e
 ~ 410-15 cm2
 ~ 210-14 cm2
 ~ 10-14 cm2
 ~ 210-16 cm2
 ~ 10-15 cm2
Details of ABIS with Resonant
Charge Exchange Ionization
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.
Schematic of Negative Ion Formation
on the Surface (Φ>s)
(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 β- can be high ~0.5 for fast
particles with S<~ φ
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
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
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
1) a molybdenum polycrystalline with a tungsten layer on the
surface,
2) (110) molybdenum,
3) a molybdenum polycrystalline,
4) an LaB6 polycrystalline.
Probability of particles and energy reflection for
low energy H particles
INR ABIS:
Oscilloscope Track of Polarized H- ion
Polarized H- ion current
4 mA (vertical scale1mA/div)
Unpolarized D- ion
current 60 mA
(10mA/div)
A. Belov
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.
Main Systems of INR ABIS with Resonant
Charge Exchange Ionization
Main Systems of INR ABIS with Resonant
Charge Exchange Ionization
Main Systems of INR ABIS with Resonant
Charge Exchange Ionization
Schematic Diagram of IUCF APPIS with
Resonant Charge Exchange Ionization
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
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 R&D schedule.
•INR, A. Belov
BINP, D. Toporkov, V. Davydenko,
BNL, A. Zelenski,
IUCF, Dubna, V. Derenchuk, A. Belov,
COSY/Julich, R. Gebel.
Components of IUCF ABPIS (sextupole, ionization
solenoid, RF dissociator, bending magnet, Arc discharge
plasma source)
Arc Discharge Ion Source
Dimov BINP 1962
Ionization 99.9 %, dissociation 99%, transverse ion temperature 0.2 eV;
multi-slit extraction.
Long Pulse Arc-discharge Plasma
Generator with Lab6 Cathode
Version with one LaB6 disc
Metal-ceramic discharge channel is developed
Version with several LaB6 discs
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 washerreturning springs;
11-ferromagnetic platearmature;
12-viton stop;
13-viton seal;
14-sealing ring;
15-aperture;
16-base;
17-nut.
Fast, Compact Cesium Supply
Cesium oven with cesium pellets and
press-form for pellets preparation.
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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.
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
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
Focusing Magnets
Permanent magnets
B=1.6 T
Superconducting
B=4.8 T
DW = p*a2 = p*m*B/kT
B = 1.6 T
DW ~ 1.5*102 sr
B = 4.8 T
DW ~ 4.5*102 sr
a ~ 0.07 rad
a ~ 0.21 rad
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.
Proposed Sources Parameters
Universal Atomic Beam Polarized Sources
(most promising, less expensive for repeating):
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•
•
•
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pulse width up to 0.5 ms; repetition up to 5 Hz
Peak Intensity H-/D- 4.0 mA/4 mA; N~1013 p/pulse
Max Pz/Pzz up to 95%;
Emittance (90)% 1.0 π·mm·mrad/1.8 π·mm·mrad;
Unpolarized H-/D- 150/60 mA.
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.
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; PVpulsed gas valves.
Realistic Extrapolation for Future
ABS/RX Source:
• H- ~ 10 mA, 1.2 π·mm·mrad (90%), Pz = 95%
• D- ~ 10 mA, 1.2 π·mm·mrad (90%), Pzz = 95%
OPPIS:
• H- ~ 40 mA, 2.0 π·mm·mrad (90%), Pz = 90%
• H+ ~ 40 mA, 2.0 π·mm·mrad (90%), Pz = 90%
Polarization in ABS/RX Source is higher because
ionization of polarized atoms is very selective and
molecules do not decrease polarization.
3He++
Ion source with Polarized 3He
Atoms and Resonant Charge
Exchange Ionization
A.S. Belov, PSTP-2007, BNL, USA
Cross-section vs collision energy for process
He++ + He0 →He0 + He++
σ=5⋅10-16cm2 at ~10eV collision energy
A.S. Belov, PSTP-2007,
BNL, USA
Polarized 6Li+++ Options
and 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 10’s
of µA
• Accelerate to 5 keV and transport through a Cs cell to
produce negative ions. Results in a few hundred nA’s 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
Multicharged Ion Beam from
Advanced ECR Ion Sources
Advantages of the new pre-injector:
Stripper
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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
J. Alessi, PSTP-2007, BNL, USA
Example of Using Ion Stripping in
Acceleration and Injection (RHIC BNL)
Performance of the Preinjector
with EBIS and RFQ + Linac (BNL)
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•
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+ )
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!
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)
> 1011 He2+ / pulse
(> 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+)
< 0.18 p mm mrad,norm,rms
Output energy
17 keV/amu
LEBT/Ion Source Region
ECR 28 GHz Heavy Ion Source Region
290 MY
BNL RFQ Pre-injector Development
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”.
66
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.
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.
History of e-p instability observation
Was presented in Cambridge PAC67 but only INP was identified
instability
From F. Zimmermann report
as e-p
Simulation of electron cloud accumulation and e-p instability
development (secondary ion/electron emission); Penning discharge
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.
Beam accumulation with a plasma generator
on and off
off
on
on
off