ION SOURCES FOR MEIC Vadim Dudnikov Muons Inc

ION SOURCES FOR MEIC Vadim Dudnikov Muons, Inc. , Batavia, IL Mini-Workshop for MEIC Ion Complex Design, Jefferson Lab. Jan 27, 2011 1

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 A 255, 442 (1987). • Belov A. S. , Dudnikov V. , et al. , . NIM A 333, 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, A 239, 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, DSPIN 2009, DUBNA, Russia; • A. Zelenski, PSTP-2007, BNL, USA; DSPIN 2009, DUBNA, Russia

EIC Design Goals § Energy • • Center-of-mass energy between 20 Ge. V and 90 Ge. V energy asymmetry of ~ 10, 3 Ge. V electron on 30 Ge. V proton/15 Ge. V/n ion up to 9 Ge. V electron on 225 Ge. V proton/100 Ge. V/n ion § Luminosity • 1033 up to 1035 cm-2 s-1 per interaction point § Ion Species • • Polarized H, D, 3 He, 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 Zhang For the ELIC Study Group Jefferson Lab

ELIC Design Goals § § § Energy Wide CM energy range between 10 Ge. V and 100 Ge. V • Low energy: 3 to 10 Ge. V e on 3 to 12 Ge. V/c p (and ion) • Medium energy: up to 11 Ge. V e on 60 Ge. V p or 30 Ge. V/n ion and for future upgrade • High energy: up to 10 Ge. V e on 250 Ge. V p or 100 Ge. V/n ion Luminosity • 1033 up to 1035 cm-2 s-1 per collision point • Multiple interaction points Ion Species • Polarized H, D, 3 He, 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 Ge. V electron • Up to 12 Ge. V/c proton (warm) • Up to 60 Ge. V/c proton (cold)

MEIC: Detailed Layout polarimetry

ELIC: High Energy & Staging Circumference Serves as a large booster to the full energy collider ring SRF Linac electron ring m 280 m 695 Straight p p 140 Length Ion Sources m Width prebooster 1800 Radius p m m 306 Interaction Point MEIC collider ring ELIC collider ring e e Ion ring e Stage injector Max. Energy (Ge. V/c) p e Low 12 5 (11) Medium 60 High 250 12 Ge. V CEBAF Vertical crossing Ring Size (m) p e Ring Type IP # p e 630 Warm 1 5 (11) 630 Cold Warm 2 10 1800 Cold Warm 4

ELIC Main Parameters Beam Energy Ge. V 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. 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. 054 0. 1 Peak Lumi/IP, 1034 cm-2 s-1 11 4. 1 High energy 1. 9 4. 0 0. 59 Low energy Medium energy

Achieving High Luminosity MEIC design luminosity L~ 4 x 1034 cm-2 s-1 for medium energy (60 Ge. V x 3 Ge. V) Luminosity Concepts • • High bunch collision frequency (0. 5 GHz, can be up to 1. 5 GHz) Very small bunch charge (<3 x 1010 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 low energy ring cooling SRF Linac source pre-booster. Accumulator ring Medium energy collider ring Energy (Ge. V/c) Stacking proton beam in ACR Circumference Energy/u Cooling electron current Cooling time for protons Stacked ion current Norm. emit. After stacking Cooling m Ge. V 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 4 D emittance by the same factor, but not k 2. 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 Me. V 200 H- current m. A 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 o. K <100 Proton beam in pre-booster after stacking Accumulated number of protons Increase of transverse temperature by scattering 2 x 1012 % 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 4 D 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 Ge. V x Ei, max) Luminosity / n (3 Ge. V x Ei, max/5) (Ge. V/nucleon) 1034 cm-2 s-1 1033 cm-2 s-1 Proton 150 7. 8 6. 7 Deuteron 75 7. 8 6. 7 3 H+1 50 7. 8 6. 7 3 He+2 100 3. 9 3. 3 4 He+2 75 3. 9 3. 3 12 C+6 75 1. 3 1. 1 40 Ca+20 75 0. 4 208 Pb+82 59 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 2 Hz (Shutdown 8/02; Rebuilded in Dubna); Peak Intensity H-/D- 2. 0 m. A/2. 2 m. A; Max Pz/Pzz 85% to 91%; Emittance (90%) 1. 2 π·mm·mrad. • INR Moscow: pulse width > 0. 1 ms; repetition 5 Hz (Test Bed since 1984); Peak Intensity H+/H- 11 m. A/4 m. A; Max Pz 80%/95%; Emittance (90)% 1. 0 π·mm·mrad/ 1. 8 π·mm·mrad; Unpolarized H-/D- 150/60 m. A. OPPIS/BNL: H- only; Pulse Width 0. 5 ms (in operation); Peak Intensity up to 1. 6 m. A; 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 (5 m. A 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 17

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 chargeexchange ) • Nearly resonant charge-exchange processes have large cross sections. This is base for high efficiency of polarized atoms conversion into polarized ions. 18 September 10 14, 2007

ABIS with Resonant Charge Exchange Ionization INR Moscow • H 0↑+ D+ ⇒H+↑+ D 0 • D 0↑+ H+ ⇒D+↑+ H 0 • σ~ 5 10 -15 cm 2 • H 0↑+ D−⇒H−↑+ D 0 • D 0↑+ H−⇒D−↑+ H 0 • σ~ 10 -14 cm 2 Limitations: Pumping is high; Extraction voltage Uex<25 k. V. A. Belov, DSPIN 2009

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 30 K - 80 K 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, 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: A 0 + A+ →A + + A 0 • Cross -section is of order of 10 -14 cm 2 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 ke. V D- ions and thermal polarized hydrogen atoms: H 0↑+ D−⇒H−↑+ D 0

Cross-section vs collision energy for process H + H 0 + H = 10 -14 cm 2 at ~10 e. V collision energy

Cross-section vs collision energy for process He++ + He 0 + He++ = 5 10 -16 cm 2 at ~10 e. V collision energy

Destruction of Negative Hydrogen Ions in Plasma • • • H + e H + D + H + D 0 H + D 2 H + D 0 H 0 + 2 e H 0 + D 0 H 0 + D 2 + e HD 0 + e ~ 4 10 -15 cm 2 ~ 2 10 -14 cm 2 ~ 2 10 -16 cm 2 ~ 10 -15 cm 2

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 La. B 6 polycrystalline.

Probability of particles and energy reflection for low energy H particles

INR ABIS: Oscilloscope Track of Polarized H- ion current 4 m. A (vertical scale 1 m. A/div) Unpolarized D- ion current 60 m. A (10 m. A/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 e. V; multi-slit extraction.

Long Pulse Arc-discharge Plasma Generator with Lab 6 Cathode Version with one La. B 6 disc Metal-ceramic discharge channel is developed Version with several La. B 6 discs

Fast, compact gas valve, 0. 1 ms, 0. 8 k. Hz 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. • • • 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 – S 1, S 2 (tapered magnets) and S 3, S 4, S 5 (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 = *a 2 = *m*B/k. T 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): • • • pulse width up to 0. 5 ms; repetition up to 5 Hz Peak Intensity H-/D- 4. 0 m. A/4 m. A; 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 m. A.

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; M 1, M 2: 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 m. A, 1. 2 π·mm·mrad (90%), Pz = 95% • D- ~ 10 m. A, 1. 2 π·mm·mrad (90%), Pzz = 95% OPPIS: • H- ~ 40 m. A, 2. 0 π·mm·mrad (90%), Pz = 90% • H+ ~ 40 m. A, 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.

3 He++ Ion source with Polarized 3 He Atoms and Resonant Charge Exchange Ionization A. S. Belov, PSTP-2007, BNL, USA

Cross-section vs collision energy for process He++ + He 0 →He 0 + He++ σ=5⋅10 -16 cm 2 at ~10 e. V collision energy A. S. Belov, PSTP-2007, BNL, USA

Polarized 6 Li+++ 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 ke. V and transport through a Cs cell to produce negative ions. Results in a few hundred n. A’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 m. A (? ) fully stripped beam with high polarization • Properties of 6 Li: Bc= 8. 2 m. T, m/m. N= 0. 82205, I = 1 Bc = critical field, m/m. N= magnetic moment, I = nuclear spin

Multicharged Ion Beam from Advanced ECR Ion Sources

Advantages of the new pre-injector: Stripper 12 • • • Simple, modern, low maintenance Lower operating cost Can produce any ions (noble gases, U, He 3 ) 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) • • • Species He to U Intensity (examples) 2. 7 x 109 Au 32+ / pulse 4 x 109 Fe 20+ / pulse 5 x 1010 He 2+ / 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 Me. V/amu (enough for stripping Au 32+ )

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 Au 32+ / pulse (1. 7 m. A) 5 x 109 Fe 20+ / pulse (1. 6 m. A) > 1011 He 2+ / pulse (> 3. 0 m. A) 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 (Au 32+) < 0. 18 mm mrad, norm, rms Output energy 17 ke. V/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, C 1. H 013/04, 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 PAC 67 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 on on off