- Количество слайдов: 40
Muons, Inc. Ion sources for EICs Vadim Dudnikov#, Muons, Inc. , Batavia, IL USA EIC Meeting at Stony Brook, January 10, 2010 1
Muons, Inc. 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 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; 2
Muons, Inc. 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 3
ELIC (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
Muons, Inc. Existing Sources Parameters Universal 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 m. A/2. 2 m. A; 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 m. A/4 m. A; Max Pz 85%/91%; 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 >1. 6 m. A; Max Pz 85% of nominal Emittance (90%) 2. 0 π·mm·mrad.
Sources of Polarized Ions a review of early work First polarized-proton sources described at the INTERNATIONAL SYMPOSIUM ON POLARIZATION PHENOMENA OF NUCLEONS Basel, July 1960 The status 40 years ago: SOURCES OF POLARIZED IONS BY W. HAEBERLI W. Haeberli, PSTP-2007, BNL, USA ANNUAL REVIEW OF NUCLEAR SCIENCE Vol. 17, 1967
Method based on 1968 proposal (NIM 62 p. 335) “ = 22 x 10 -16 cm 2 at 2 ke. V -> 100 x 10 -16 cm 2 at 10 e. V A. S. Belov et al. (INR-Moscow) - 20 yrs development work Intense beam of unpolarized D- from deuterium plasma ionizes an atomic beam (2 x 1017 H 0 /sec puled) Pulsed 4 m. A H- 95% Polarization W. Haeberli, PSTP-2007, BNL, USA BELOV
L. W. Anderson (Wisconsin) - optically pumped Na as donor (1979) OPPIS: Zelenski, Mori et al. DONOR: OPTICALLY PUMPED 20 years of development CHARGE EXCHANGE 3 ke. V H+ B “SONA” TRANSITION POLARIZED H+ AND H- B 1. 6 m. A H- 85%-90% Polarization with new proton souce 20 -50 m. A possible W. Haeberli, PSTP-2007, BNL, USA Zelensk i
Muons, Inc. ABIS with Resonant Charge Exchange Ionization • • INR Moscow H 0↑+ D+ ⇒H+↑+ D 0↑+ H+ ⇒D+↑+ H 0 σ~ 5 10 -15 cm 2 H 0↑+ D−⇒H−↑+ D 0↑+ H−⇒D−↑+ H 0 σ~ 10 -14 cm 2 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.  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.
Muons, Inc. 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. 18
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
Muons, Inc. Main Systems of INR ABIS 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
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 D. K. Toporkov, PSTP-2007, BNL, USA
BINP Cryogenic Atomic Beam Source atomic beam source with superconductor sextupoles Two group of magnets – S 1, S 2 (tapered magnets) and S 3, S 4, S 5 (constant. Cryostatdriven independently, 200 and 350 A respectively radius) Liquid nitrogen
Focusing magnets (BINP) 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
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-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.
Muons, Inc. 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
Muons, Inc. 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
Muons, Inc. Multicharged Ion Beam from Advanced ECR Ion Sources
Advantages of the new preinjector: Stripper 12 • • • J. Alessi, PSTP-2007, BNL, USA 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
Muons, Inc. Example of Using Ion Stripping in Acceleration and Injection (RHIC BNL)
Muons, Inc. 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 the 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
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. Muons, Inc.
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. Muons, Inc.