Perspectives for Highly Polarized Ion Sources Developmen高極化離子源的發(fā)展前景

1、perspectives for highly perspectives for highly polarized ion sources polarized ion sources development development vadim dudnikov, muons, inc., batavia, il usathe xvth international workshop on polarized sources, targets and polarimetry (ptsp 2013) the university of virginia, charlottesville, usa,

2、september 2013muons, inc.1outline outline features of an universal abp ion source are discussed.the main innovation of this approach is the strong suppression of parasitic generation of unpolarized h-/d- ions by using novel designs of the dissociator, plasma generator, and surface-plasma ionizer, ex

3、traction system, which prevent adsorption and depolarization of particles from the polarized atomic beam. the same system with some modifications can be capable of producing positive and negative ion beams of different species including polarized and unpolarized h-, d-, h+, d+, 3he, and li. producti

4、on of polarized 3he- ion beam with intensity ma will be discussedintroductionintroduction*high beam polarization degree is essential to the scientific productivity of a collider. *a figure-8 shape of booster and collider rings is an optimized solution to preserve ion beam polarization by avoiding sp

5、in resonances during acceleration and to ensure energy independence of spin tune. *in addition, a figure-8 shape ring is the only practical way for accelerating and storing polarized deuterons at a medium energy range. if there is no depolarization during acceleration and storage, the final beam pol

6、arization is determined by the initial polarization at extraction from the ion source. * ion sources with performances exceeding those achieved today is a key requirement for the development of the next generation high-luminosity high-polarization colliders.budker institute of nuclear physics www.in

7、p.nsk.sunovosibirsk state university www.nsu.rurequirements to the polarized source.requirements to the polarized source.requirement to ion sources intensity was decreased for many orders by development of charge exchange injection, capable to accumulate beams during tens thousand turns.high intensi

8、ty 51011 h-/pulse at 200 mev after the linac. at booster beam intensity acceptances are limited by about 11011 protons/bunch. the intensity excess can be used to reduce transversal and longitudinal beam emittances by a strong dynamical collimation in the booster.highest possible polarization is requ

9、ired to reduce a systematical and statistical errors in polarization experiments. double spin asymmetry statistical error is proportional to 1/sqrt(l p4), therefore a 5% polarization increase in the source (or 5% polarization losses decrease in booster and eic is effectively equivalent to 30% increa

10、se in the data taking time. beam intensity and polarization must be equal at spin-reversal and from pulse to pulse. i/i 10-3 and p/p 0.1 ms (test bed since 1984); peak intensity h+/h- 11 ma/4 ma; max pz 80%/95%; emittance (90)% 1.0 mmmrad/ 1.8 mmmrad; unpolarized h-/d- 150/60 maspi dubna up to 10 ma

11、 for d+ ( h+) under spi dubna up to 10 ma for d+ ( h+) under commissioningcommissioningthe d+ polarization will be up to 90% of the maximal vector d+ polarization will be up to 90% of the maximal vector ( (1) &tensor (+1,-2) polarization1) &tensor (+1,-2) polarizationoppis/bnl: h- only; puls

12、e width 0.5 ms (in operation); peak intensity 1.6 ma; max pz 85% of nominal emittance (90%) 2.0 mmmrad.muons, inc.first polarized-proton sources described at theinternational symposium on polarization phenomena of nucleonsbasel, july 1960sources of polarized ions a review of early worksources of pol

13、arized ionsby w. haeberliannual review of nuclear science vol. 17, 1967the status 40 years ago:w. haeberli, pstp-2007, bnl, usamethod based on 1968 proposal (nim 62 p. 335)s s = 22x10-16cm2 at 2kev - 100 x10-16cm2 at 10ev a.s. belov et al. (inr-moscow) - 20 yrs development workintense beam of unpola

14、rized d- fromdeuterium surface-plasma ionizes an atomic beam (2x1017 h0 / /sec puled) pulsed 4 ma h- 95% polarizationbelov“w. haeberli, pstp-2007, bnl, usazelenskioppis: zelenski, mori et al. 20 years of development 1.6 ma h- 85-90% polarization with new proton source 20-50ma possiblel.w. anderson (

15、wisconsin) - optically pumped na as donor (1979) 3 kev h+polarizedh+ and h-donor:optically pumpedcharge exchangebb“sona”transitionw. haeberli, pstp-2007, bnl, usaa. belov & v. derenchuk: a. belov & v. derenchuk: iucf/inr cipios developersdevelopersabpis with resonant charge exchange ionizati

16、on and surface-plasma d- generationmuons, inc.inr moscowh0+ d+ h+h+ d0d0+ h+ d+d+ h0 5 10-15cm2h0+ dh h+ d0d0+ hd d+ h0 10-14cm2a. belov, dspin2009 main systems of inr abpis with resonant charge exchange ionizationmuons, inc.atomic beam polarized ion sourceatomic beam polarized ion sourcein the abs,

17、 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

18、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 tr

19、ansition 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 sextupo

20、le 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 deuteriu

21、m, 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 de

22、pended 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 hydrog

23、en 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 atomsionization of polarized atomsresonant charge-exchange reaction is charge exchange between ato

24、m and ion of the same atom: a0 + a+ a + + a0cross -section is of order of 10-14 cm2 at low collision energycharge-exchange between polarized atoms and ions of isotope relative the polarized atoms to reduce unpolarized backgroundw. haeberli proposed in 1968 an ionizer with colliding beams of 1-2 kev

25、d- ions and thermal polarized hydrogen atoms: h0+ dh h+ d0destruction of negative hydrogen destruction of negative hydrogen ions in plasmaions in plasma h + e h0 + 2e s 410-15 cm2 h + d+ h0 + d0 s 210-14 cm2 h + d0 h0 + d s 10-14 cm2 h + d2 h0 + d2 + e s 210-16 cm2 h + d0 hd0 + e s 10-15 cm2details

26、of abis with resonant charge exchange ionizationresonance charge exchange ionizer with two resonance charge exchange ionizer with two steps surface plasma convertersteps surface plasma converter*jet of plasma is guided by magnetic field to internal surface of cone; *fast atoms bombard a cylindrical

27、surface of surface plasma converter initiating a secondary emission of negative ions increased by cesium adsorption.*an electron blocker collects plasma electrons, decreases electron extraction and h-destructioninr abpis: oscilloscope track of polarized h- ionpolarized h- ion current 4 ma (vertical

28、scale-1ma/div) unpolarized d- ion current 60 ma (10ma/div)parasitic h- current without polarized h atomic beama. belovprobability of h- emission as function of work function (cesiation effect)the surface work function decreases with deposition of particles with low ionization potential and the proba

29、bility of secondary negative ion emission increases greatly from the surface bombarded by plasma particles. dependence of work function on surface cesium concentration for w crystalline surfaces and relative yield y of h- secondary emission for w surface index (111), right scale muons, inc.20schemat

30、ic of negative ion formation on the surface (s) (formation of secondary ion emission; (formation of secondary ion emission; michail kishinevsky) michail kishinevsky) sov. phys. tech. phys, 45 (1975)sov. phys. tech. phys, 45 (1975) affinity lever s is lowering by image forces below fermi level during

31、 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

32、particles; ionization coefficient - can be high 0.5 for fast particles with s can be produced and then quenching one of the hyperfine levels by an rf resonant field can be produced 3he- beam with polarization 100%. (s. manson, pr a,3, 1,147,1971)the decay curve of 4he- measured at 10 k.the decay cur

33、ve of 4he- measured at 10 k.the solid curve is a fit to the data. the insert shows a time region in which the decay of the short lived j =1/2 and j=3/2 levels dominate the intensity. (p. reinhed, et al.,prl 103, 213002 (2009) ) temperature dependence of the measured lifetime of the 1s2s2p 4po5/2 lev

34、el of 4he-. the effect on the decay rate from photodetachment by blackbody radiation can readily be seen as a decrease in the measured lifetime above 100 k.separation of fine components of he- in the separation of fine components of he- in the magnetic fieldmagnetic fieldcomponents with highest mome

35、ntum 5/3 have largest lifetime 350 sec when components with lower momentum have lifetime 10 sec. 3he- ion beam composed only of hyperfine components 5/2, +-5/2 can be produced and then quenching one of the hyperfine component by an rf resonant field can be produced 3he- beam with 100% polarization.t

36、he fine-structure results are: 53= 825.23 + 0.82 mhz,51 = 8663 + 56 mhz.separation of fine components of 7 liseparation of fine components of 7 li* * in the in the magnetic fieldmagnetic fieldenergy as a function of magnetic field for various (1s2s2p) 4p substates of 7li the positions of the three o

37、bserved anticrossings are indicated by a. production of polarized 7li through different lifetime of metastable states is also available.(physical review a volume 3, nu mb e r january 1971, determination of energies and lifetimes of the metastable auto-ionizing (1s2s2p) 4p states of 6li and 7li by a

38、zeeman-quenching technique, m. levitt and r. novick, p. d. feldman).he-/he+ yield and beam intensity vs. he+ energy in k he-/he+ yield and beam intensity vs. he+ energy in k target.target. with 2 a he+ current from binp arc discharge source it is possible to have 0.1 a of he- ions. up to 4 ma of 3he

39、- with high nuclear polarization can be produced.a. szanto de toledo and 0. sala, production of negative helium ions, revista brasileira de fsica, vol. 7, n 1, 1977).polarized 3he- ion sourcepolarized 3he- ion source binp high brightness arc discharge ion source with cs jet charge exchange target (a

40、s for bnl oppis)a schematic of the experiment on he- beam production. 1- he+ source, 2 extraction system, 3 space charge compensation xe, 4 k (rb, cs) target, 5 bending magnet, 6 decay channel with solenoid and rf transition, 7-he+ beam; 8-space charge compensated beam; 9-he- beam.polarized 3he- ion

41、 sourcepolarized 3he- ion source binp high brightness arc discharge ion source with cs jet charge exchange target (as for bnl oppis)a schematic of the polarized 3he- beam production. 1- he+ source, 2 extraction system, 3 space charge compensation xe, 4 k (rb, cs) target, 5 bending magnet, 6 decay ch

42、annel with solenoid and rf transition, 7-he+ beam; 8-space charge compensated beam; 9-he- beam; 10-polarized 3he- beam; 11-neutrals of 3he beam.3he- negative ion are separated from 3he neutrals by separating magnets (5). the separated 3he- beam (10) is accelerated for further use and can be converte

43、d to 3he+ by stripping in a foil or he gas target. beam tubes need be cooled below t150k. references have been foundit was suggested earlier that the differentialmetastability of the (1s2s2p) 4p levels would providea possible mechanism for producing polarized electrons and nuclei, especially those o

44、f 3he (i =1/2, ) and 6li (i=1).p. feldman and r. novick, in comptes rendus du congres international de physique nucleaire, paris, 1964, edited by p. gugenberger (cnrs, paris, 1964), vol. ii, 4a/c144, pp. 785-786.muons, inc.polarized 6li+ optionsand other elements with low ionization potentialexistin

45、g technology:existing technology:create a beam of polarized atoms using abscreate a beam of polarized atoms using absionize atoms using surface ionization on an 1800 k ionize atoms using surface ionization on an 1800 k tungsten (rhenium) foil tungsten (rhenium) foil singly charged ions of a few sing

46、ly charged ions of a few 1010s of s of a aaccelerate to 5 kev and transport through a cs cell to accelerate to 5 kev and transport through a cs cell to produce negative ions. results in a few hundred naproduce negative ions. results in a few hundred nas of s of negative ions (can be increased signif

47、icantly in pulsed negative ions (can be increased significantly in pulsed mode of operation)mode of operation)investigate alternate processes such as quasiresonant investigate alternate processes such as quasiresonant charge exchange, ebis ionizer proposal or ecr ionizer. charge exchange, ebis ioniz

48、er proposal or ecr ionizer. should be possible to get 1 ma (?) fully stripped beam should be possible to get 1 ma (?) fully stripped beam with high polarizationwith high polarizationproperties of 6li: bc= 8.2 mt, m/mn= 0.82205, i = 1properties of 6li: bc= 8.2 mt, m/mn= 0.82205, i = 1 bc = critical f

49、ield m/mn= magnetic moment, i = nuclear bc = critical field m/mn= magnetic moment, i = nuclear spinspinmuons, inc.production of highest polarization and reliable operation are main goals ofthese ion sources development development of universal atomic beam polarized sources (most promising, less expe

50、nsive for repeating) . it is proposed to develop one universal h-/d-/he it is proposed to develop one universal h-/d-/he ion source design which will synthesize the most ion source design which will synthesize the most advanced developments in the field of polarized advanced developments in the field of polarized ion sources to provide high current, high ion sources to provide high current, high brightness, ion beams with greater than 90% bri