Ion sources for EICs

Vadim Dudnikov#,

Muons, Inc., Batavia, IL USA

EIC Meeting at Stony Brook, January 10, 2010

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Outline• Ion sources for production of polarized

negative and positive light and heavy ions will be considered. 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;

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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

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Yuhong ZhangFor the ELIC Study Group

Jefferson Lab

ELIC (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

Existing Sources ParametersUniversal Atomic Beam Polarized Sources (most promising,

less expensive for repeating):• IUCF/INR CIPIOS: Pulse Width Up to 0.5 ms (Shutdown 8/02,

Rebuild in Dubna); Peak Intensity H-/D- 2.0 mA/2.2 mA; Max Pz/Pzz 85% to

90%; Emittance (90%) 1.2 π·mm·mrad.• INR Moscow: Pulse Width > 0.1 ms (Test Bed since 1984); Peak Intensity H+/H- 11 mA/4 mA; Max Pz 85%/91%; 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 >1.6 mA; Max Pz 85% of nominal Emittance (90%) 2.0 π·mm·mrad.

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First polarized-proton sources described at theINTERNATIONAL SYMPOSIUM ON POLARIZATION

PHENOMENA OF NUCLEONSBasel, July 1960

Sources of Polarized Ions a review of early work

SOURCES OF POLARIZED IONSBY W. HAEBERLI

ANNUAL REVIEW OF NUCLEAR SCIENCE Vol. 17, 1967

The status 40 years ago:

W. Haeberli, PSTP-2007, BNL, USA

Method based on 1968 proposal (NIM 62 p. 335)

= 22x10-16cm2 at 2keV -> 100x10-16cm2 at 10eV

A.S. Belov et al. (INR-Moscow) - 20 yrs development workIntense beam of unpolarized D- fromdeuterium plasma ionizes an atomic beam(2x1017 H0sec puled)

Pulsed 4 mA H-95% PolarizationBELOV

“

W. Haeberli, PSTP-2007, BNL, USA

Zelenski

OPPIS: Zelenski, Mori et al. 20 years of development

1.6 mA H-85%-90% Polarization with new proton souce 20-50mA possible

L.W. Anderson (Wisconsin) - optically pumped Na as donor (1979)

3 keV H+ POLARIZEDH+ AND H-

DONOR:

OPTICALLY PUMPEDCHARGE

EXCHANGE

B B

“SONA”TRANSITION

W. Haeberli, PSTP-2007, BNL, USA

ABIS with Resonant Charge Exchange Ionization

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• 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

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.

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.

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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

Main Systems of INR ABIS with Resonant Charge Exchange Ionization

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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

INJECTION OF BACKGROUND GAS AT DIFFERENT POSITION

ATTENUATION OF THE BEAM ISDEPENDENT FROM THE POSITIONOF THE GAS INJECTIOJN

NOT MANY EXPERIMENTAL DATAAVAILABLE

D.K.Toporkov, PSTP-2007, BNL, USA

Cryogenic Atomic Beam Source

Liquid nitrogenCryostatCryostatTwo 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

Focusing magnets (BINP)

Permanent magnetsB=1.6 TSuperconductingB=4.8 T

sr rad srrad

Polarimeter vacuum system RHIC

Polarimeter vacuum system RHIC

• 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.

A general polarized RHIC OPPIS injector layout.

ECR: electron-cyclotronresonance proton source in SCS; SCS: superconducting solenoid; Na-jet: sodium-jetionizer 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.

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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

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Multicharged Ion Beam from Advanced ECR Ion Sources

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Advantages of the new preinjector:

• 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

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Stripper

J. Alessi, PSTP-2007, BNL, USA

Example of Using Ion Stripping in Acceleration and Injection (RHIC BNL)

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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+ )

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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 the 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

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.

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Conclusion

Optimized versions of developed 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 sources and injection system are necessary for reliable production of necessary beams parameters and need be developed. Collaborations will be established for these development.

Advanced control of instabilities should be developed for support a high collider luminosity.

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