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ION SOURCES FOR MEIC. Vadim Dudnikov Muons, Inc., Batavia, IL. Mini-Workshop for MEIC Ion Complex Design, Jefferson Lab. Jan 27, 2011. Abstract. - PowerPoint PPT Presentation
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ION SOURCES FOR MEIC
Vadim Dudnikov
Muons, Inc., Batavia, IL
Mini-Workshop for MEIC Ion Complex Design, Jefferson Lab. Jan 27, 20111
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)• 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
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 >70% desirable
Positron Beam desirable Yuhong ZhangFor 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
Ion Sources
SRF Linac
p
e
e e
pp
prebooster
ELIC collider
ring
MEIC collider
ring
injector
12 GeV CEBAF
Ion ring
electron ring
Vertical crossing
Interaction Point
Circumference m 1800
Radius m 140
Width m 280
Length m 695
Straight m 306
Stage Max. Energy (GeV/c)
Ring Size (m)
Ring Type IP#
p e p e p e
Low 125
(11)630 Warm
Warm
1
Medium
605
(11)630 Cold
Warm
2
High250
10 1800 ColdWarm
4
Serves as a large booster to the full energy collider ring
ELIC Main Parameters
Beam Energy GeV 250/10
150/7 60/5 60/3 12/3
Collision freq. MHz 499
Particles/bunch 1010 1.1/3.1
0.5/3.25
0.74/2.9 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 0.37/2.7
Energy spread 10-4 ~ 3
RMS bunch length
mm 5 5 5 5 50
Horiz.. emit., norm.
μm 0.7/51 0.5/43 0.56/85 0.8/75 0.18/80
Vert. emit. Norm. μm 0.03/2 0.03/2.87
0.11/17 0.8/75 0.18/80
Horizontal beta-star
mm 125 75 25 25 5
Vertical beta-star mm 5
Vert. b-b tune shift/IP
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• 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/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
Circumference m 100
Energy/u GeV0.2 -
0.4Cooling electron
current A 1
Cooling time for protons
ms 10
Stacked ion current A 1Norm. emit. After
stackingµm 16
Stacking proton beam in ACR
Energy (GeV/c)
Cooling Process
Source/SRF linac 0.2 Full stripping
Prebooster/Accumulator-Ring
3DC
electronStacking/accumulating
Low energy ring (booster)12 Electron
RF bunching (for collision)
Medium energy ring60 Electron
RF bunching (for collision)
source
SRF Linac
pre-booster-Accumulator ring
low energy ring
Medium energy collider ring
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 resonators2, 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
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.
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: 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 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 6.73H+1 50 7.8 6.7
3He+2 100 3.9 3.34He+2 75 3.9 3.312C+6 75 1.3 1.1
40Ca+20 75 0.4 0.4208Pb+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 high-luminosity 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.
September 10-14, 2007A.S. Belov, PSTP-2007, BNL, USA 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
September 10-14, 2007A.S. Belov, PSTP-2007, BNL, USA
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.
ABIS with Resonant Charge Exchange Ionization
INR Moscow• H0↑+ D+ ⇒H+↑+ D0
• D0↑+ H+ ⇒D+↑+ H0
• σ~ 5 10-15cm2
• H0↑+ D−⇒H−↑+ D0
• D0↑+ H−⇒D−↑+ H0
• σ~ 10-14cm2
A. Belov, DSPIN2009
Limitations:
Pumping is high;
Extraction voltage
Uex<25 kV.
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:
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++
= 510-16 cm2 at ~10eV collision energy
Schematic diagram of the ionizerfor polarized negative hydrogen ions production
Destruction of Negative Hydrogen Ions in Plasma
• H + e H0 + 2e ~ 410-15 cm2
• H + D+ H0 + D0 ~ 210-14 cm2
• H + D0 H0 + D ~ 10-14 cm2
• H + D2 H0 + D2 + e ~ 210-16 cm2
• H + D0 HD0 + e ~ 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 molyb denum polycrystalline with a tungsten layer on the surface,
2) (110) molybdenum, 3) a molyb denum 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 scale-1mA/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
Ionization 99.9 %, dissociation 99%, transverse ion temperature 0.2 eV;
multi-slit extraction.
Dimov BINP 1962
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
Fast, compact gas valve, 0.1ms, 0.8 kHz1 -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.
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.
ATTENUATION OF THE BEAM ISDEPENDENT FROM THE POSITIONOF THE GAS INJECTIOJN
NOT MANY EXPERIMENTAL DATAAVAILABLERemote fine positioning now available
D.K.Toporkov, PSTP-2007, BNL, USA
Injection of Background Gas at Different Position
INJECTION OF BACKGROUND GAS AT DIFFERENT POSITION
Cryogenic Atomic Beam Source
Two group of magnets – S1, S2 (tapered magnets) and S3, S4, S5 (constant radius) driven independently, 200 and 350 A respectively
BINP Atomic Beam Source with Superconductor Sextupoles (2 1017 a/s)
CryostatCryostat Liquid nitrogen
Focusing Magnets
Permanent magnetsB=1.6 TSuperconductingB=4.8 T
sr rad srrad
• 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.
BNL Polarimeter vacuum system
BNL Polarimeter vacuum system
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; 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-cyclotronresonance 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; PV-pulsed 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+++ 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 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:
• 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
12
Stripper
J. Alessi, PSTP-2007, BNL, USA
Example of Using Ion Stripping in Acceleration and Injection (RHIC BNL)
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+ )
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!
Principle of EBIS Operation
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 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)
Invention formula:
“Enhancement of negative ion production comprising admixture into the discharge a substance with a low ionization potential, such as cesium”.
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.
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
From F. Zimmermann report
Was presented in Cambridge PAC67 but only INP was identified as e-p instability
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
onoff
off
on