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