The Toolbox of W. Haeberli University of Wisconsin Proton Spin Physics (in historical perspective) PST 2007 at BNL, September 12, 2007

Tool: Nuclear Interaction Nuclear Shell Model: strong spin-orbit coupling Jensen and Goepper-Mayer 1949 (Nobel prize 1963) force between proton (spin s) and nucleus depends on orientation of spin relative to orbital. differs from Thus: -> polarize protons by scattering from nucleus -> determine sign of spin-orbit coupling.

J. Schwinger (Abstract at APS meeting 1946) suggested double-scattering to determine sign of spin-orbit splitting First nuclear polarization eperiment by Heusinkveld and Freier 1951 experiment is feasible only with protons rather than neutrons (Wolfenstein)

Polarizer Analyzer Double scattering expt: elastic scattering: P=A P in reaction [e.g. 3 He(d,p) 4 He] = A of inverse reaction[ 4 He(p,d) 3 He]

Heusinkveld and Freier: Fermi-Yang ambiguity:two sets of phase shifts identical  He gas

0.3  2x10 12 p/s) beam -> 4x10 6 pol p/s

At high energies, no reactions with large analyzing power FNAL 185 GeV/c polarized proton channel uses protons from  decay polarized proton beam line (D. P. Grosnick et al. 1990) Proton intensity (20 s spill) protons produce -> 10 6 polarized protons with P= 45% Polarized ion SOURCE - even if feeble - would be MUCH better! Problems to overcome: make ions - accelerate without loss of pol. note scale! Small-angle analyzing power A n results from Coulomb-nuclear interference A n for pp elastic 185 MeV/c vs -t 800 GeV/c

First polarized-proton sources described at the INTERNATIONAL SYMPOSIUM ON POLARIZATION PHENOMENA OF NUCLEONS Basel, July 1960 Sources of Polarized Ions a review of early work SOURCES OF POLARIZED IONS BY W. HAEBERLI ANNUAL REVIEW OF NUCLEAR SCIENCE Vol. 17, 1967 The status 40 years ago:

Associated with proton spin is a magnetic moment  : N S So why not use a strong magnet to line up the proton spins? In a magnetic field spin is either up or down (space quantization) Up-down energy difference is 2  B where  proton = 8.8x10 -8 eV/T Even for 10T field (100 kG) thermal energy kT at 300K (room temp) is 14,000-times larger! At 0.3K still 14-times. Polarizing protons is difficult …… Need a better POWERTOOL!

mag moment of H atom Powertool: H-atom 1. The electron has the same spin but 660-times larger magnetic moment than the proton. 2. H atom is neutral - suitable for deflection in inhomogenous magnetic field. 3. B-field of electron at proton is large (17.4T) E. Wrede (Hamburg, 1927 student of Stern) and T.E. Phipps and J.E. Taylor (U. Illinois) observed deflection of H atom in magnetic field gradient of 1.0 T/cm. Splitting of 0.1 mm corresponds to mag moment of 1 Bohr Magneton 5.8x10 -5 eV/T. Original photogaph recovered from MPI-Heidelberg

Polarized Atomic H Beam -Principle Great increase in intensity by use of multipole field, suggested by Wolfgang Paul,Bonn 1951-(Nobel 1989). Spin-up is focussed, spin-down defocussed Development of atomic-beam sources in Europe starting in Erlangen (1958). 1960: good beam intensities achieved [~1.0x10 16 H/s] but 10 8 /s r H H2H2 

P=0! no net nuclear polarization! State 1 State 2 In STRONG magnetic field:

P=0! no net nuclear polarization! In WEAK magnetic field: + P = 1/2 (used in some early work) State 1 State 2 In “weak” field e and precess (hyperfine interaction) In STRONG magnetic field: How weak? Critical field = 0.05T (507 G) “mixed state”

Better: RF transitions to induce spin flips (developed at Saclay) State 1 State 2 “Strong-field” transition P= +1 in strong B-field Weak-field transition P= -1 in weak B-field +1 0 P “mixed state” “pure state” e p

Ionization by electron bombardment (e.g. 200 eV)   ~ cm 2 First sources used weak field ionization Improved by strong-field ionizers (Glavish, Thirion): confine electrons in solenoid. Early Polarized Proton Ion Sources Status 40 years ago 0.5  A polarized p P=90% Ionization efficiency Strong-field ionizer (Glavish)

First source of neg pol H (1964) Gruebler, Schwandt, Haeberli Making negative polarized H ions H 0 beam 0.4x10 16 /s H + beam 0.15  A = /s H - beam 10 8 /s P = 0.47 (weak field) Ionizer: 0.2A electrons, 250 eV Ionizer efficiency 0.25x10 -4 A feeble beam…

d,p reaction: when neutron is captured by nucleus, which way does spin point? Use POLARIZED deuterons! T. Yule 1967 p-d and p-p scattering- is there spin dependence? Wisc. PS2 Lamb-Shift T.B. Clegg 12 MeV 1968 A Parity violation expts SIN and TRIUMF ±2x10 -4 ±5x10 -3 ±1x10 -7 but some interesting results A

Steve Vigdor as doctoral student at Wisconsin, 1971

Progress in Atomic-Beam Ion Sources From  A to mA! Penning ionizers (solenoid) 50  A H + (P=80%) ECR ionizers (e.g. TUNL, PSI)  A H + BUT: Negative ions preferred for injection in to synchrotrons ( multiturn charge-exchange injection ) Two-step process H 0 -> H + -> H - is inefficient Is there a better way? Primarily improved IONIZERS:

A NEW TOOL: Electron transfer to H 0 from atoms or ions First test (Wisconsin): 1  A H - - large polarization (90%). present (COSY-Jülich): 50  A H - Proposal (1968) to transfer an electron from Cs to H 0 H 0  +Cs 0 (30keV) -> H -  + Cs + (  = 4x cm 2 ) Cs Cs + (30 keV) CsH0H0 B BUT best modern sources (BNL-RHIC, INR-Moscow) produce a hundred times more intense negative ions - how is it done?

Method based on 1968 proposal (NIM 62 p. 335)  = 22x cm 2 at 2keV -> 100x cm 2 at 10eV   A.S. Belov et al. (INR-Moscow) - 20 yrs development work Intense beam of unpolarized D - from deuterium plasma ionizes an atomic beam (2x10 17 H 0  sec puled) Pulsed 5 mA H -  95% Polarization BELOV “

A Different Tool to Produce H 0  Pickup of Polarized Electrons by H + Instead of SLOW H 0  atomic beam) Produce FAST (keV) H 0  by charge exchange. First proposed by Zavoiskii (1957): magnetized Fe foil as donor 1965 suggestion: instead, use polarized H in vessel or optically pumped vapor H+H+ POLARIZED H + AND H - POLARIZED H 0 (IN WEAK FIELD) DONOR OF POLARIZED ELECTRONS FOIL Advantage of FAST beam: easy efficient ionization

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 + POLARIZED H + AND H - DONOR: OPTICALLY PUMPED CHARGE EXCHANGE BB “SONA” TRANSITION

10 W 25 kG --> < kG  ~ cm 2 H-H- A. Zelenski, PST 2005 Tokyo

Another toolbox: Polarizing the Targets! Conventional solid target: e.g. NH 3 at 1K and 5T B-field, P = 85% The DREAM: Pure H  gas Target in Storage Ring For H beam 4x10 16 /s-cm -2, v=2000m/s target density ~2x10 11 cm Experiment at Stanford (  -scattering) 4 counts per HOUR! 1985 Novosibirsk 290 MeV ring, 0.3A electrons 1990 COSY GeV/c “jet target” H0H0 PARTICLE BEAM Recyle, don’t waste!

“Storage Cell” 10cm 3x10 16 H  /s target thickness H  cm 2 (100-times better than jet!)  Beam tube feed tube Carcasonne (Fr) Actually a 13 th century idea …

“Storage Cell” in Medieval Warfare 10cm 3x10 16 H  /s target thickness H  cm 2 (100-times better than jet!)  Beam tube feed tube Carcasonne (Fr)

Tool: Recyling of atoms - “Storage Cell” Target expected target thickness H  cm 2 (100-times better than jet!)  10cm 3x10 16 H  /s Beam tube feed tube Carcasonne (Fr) S. Price, Wisconsin 1990 First test (Wisconsin) 1981

Polarized gas target and storage ring - an ideal marriage! But objections: atoms may depolarize in wall collisions (radiation damage to wall), beam lifetime, background etc. etc. Storage ring MPI-Hdb (1991) No depolarization Teflon-coated cell permits cooling No radiation damage Long beam life time Target thickness: 5x10 13 atoms/cm 2 Two states: atoms/cm 2 Novosibirsk 1989 VEEP-3 e-d Improved atomic beam ->

permanent magnet sextupole T gradient 5.7 T/cm Atomic-beam improvements From 1 to 10x10 16 atoms/s in 40 years cool beam sextupoles: rare-earth permanent magnets reduced gas scattering achromatic beam transport multidimensional search for optimum 240 mm Magnet for RHIC polaried H-jet target (T. Wise et al.) -> 12x10 16 atoms/s. -> absolute beam polarization calibration at high energy (Y. Makdisi 3:40 pm)

permanent magnet sextupole T gradient 5.7 T/cm Atomic-beam improvements From 1 to 10x10 16 atoms/s in 40 years cool beam sextupoles: rare-earth permanent magnets reduced gas scattering achromatic beam transport multidimensional search for optimum 1 cm

T. Wise et al.( 1992) One Example: IUCF storage ring (400 MeV) free orientation of target polarization Rapid polarization cycling Large solid-angle detectors Proton Storage Rings: IUCF, COSY, RHIC

Slide 35 Spin-correlation in pp-scattering 200 MeV Rathmann 1998

Beautiful research with storage cell targets (H and D) at Novosibirsk, MIT-Bates, DESY, Amsterdam MIT-Bates target Electron strorage rings: E. Steffens: 2 pm today

The RHIC Polarized Jet Target ABS Polarimeter Absolute calibration of high- energy beam polarization. Y. Makdisi 3:40 pm today (H. Okada, Monday)

Conclusions: polarized beams and gas targets have become a beautiful precision tool important, unique experiment became possible and very personally: happy to have been part of it for 50 years grateful for fun of discovery, fufilled dreams. …and thanks to: my students, postdocs, scientist (Tom Wise) and collaborators (ETH, SIN, MPI-Heidelberg, DESY, IUCF, BNL).