The Toolbox of

W. Haeberli

University of Wisconsin

Proton Spin Physics (in historical perspective)

PST 2007 at BNL, September 12, 2007

Tool: Nuclear InteractionNuclear Shell Model: strong spin-orbit couplingJensen 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 protonsrather than neutrons (Wolfenstein)

P N N N N

9 1

9 10.8

Polarizer Analyzer

A NL NR

NL NR

P N N N N

9 1

9 10.8

A NL NR

NL NR

Double scattering expt:

PA NL NR

NL NR

R 1

R 1

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

Heusinkveld and Freier:

Fermi-Yang ambiguity:two sets of phase shifts identical

He gas

0.3 2x1012 p/s) beam -> 4x106 pol p/s

At high energies, no reactions with large analyzing powerFNAL 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) 1012 protons produce -> 106 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 An results

from Coulomb-nuclear interference

An for pp elastic

185 MeV/c vs -t

800 GeV/c

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:

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 2B 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-atom1. 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 fieldgradient of 1.0 T/cm. Splitting of 0.1 mmcorresponds to mag moment of 1 Bohr Magneton 5.8x10-5 eV/T.

Original photogaph recovered from MPI-Heidelberg

B r2

F r k

r

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 [~1.0x1016 H/s] but

108 /s108 /s108 /s

rH

H2

B

kT

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 transitionP= -1 in weak B-field

+1

0

-1

P

“mixed state”

“pure state”

e p

Ionization by electron bombardment (e.g. 200 eV) ~ 10-16 cm2

First sources used weak field ionizationImproved by strong-field ionizers (Glavish, Thirion): confine electrons in solenoid.

Early Polarized Proton Ion Sources Status 40 years ago

0.5 A polarized pP=90%10-3 Ionization efficiency

Strong-field ionizer (Glavish)

First source of neg pol H (1964)Gruebler, Schwandt, Haeberli

Making negative polarized H ions

H0 beam 0.4x1016 /sH+ beam 0.15 A = 1012 /sH- beam 108 /sP = 0.47 (weak field)Ionizer: 0.2A electrons, 250 eVIonizer 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. PS2Lamb-Shift

T.B. Clegg 12 MeV1968

A

Parity violation exptsSIN 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) 100-300 A H+

BUT: Negative ions preferred for injection in to synchrotrons(multiturn charge-exchange injection)

Two-step process H0 -> H+ -> H- is inefficient

Is there a better way?

Primarily improved IONIZERS:

A NEW TOOL:Electron transfer to H0 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 H0

H0+Cs0 (30keV) -> H-+ Cs+ (= 4x10-16 cm2)

Cs

Cs+ (30 keV)CsH0

B

BUT best modern sources (BNL-RHIC, INR-Moscow) producea hundred times more intense negative ions - how is it done?

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 5 mA H-95% PolarizationBELOV

“

A Different Tool to Produce H0 Pickup of Polarized Electrons by H+

Instead of SLOW H0atomic beam) Produce FAST (keV) H0by charge exchange.

First proposed by Zavoiskii (1957): magnetized Fe foil as donor1965 suggestion: instead, use polarized H in vessel or optically pumped vapor

H+ POLARIZEDH+ AND H-

POLARIZED H0

(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+ POLARIZEDH+ AND H-

DONOR:

OPTICALLY PUMPEDCHARGE

EXCHANGE

B B

“SONA”TRANSITION

10 W

25 kG --> <-- 2.5 kG

~10-14cm2

H-

H R b

H 0

A. Zelenski, PST 2005 Tokyo

Another toolbox: Polarizing the Targets!

Conventional solid target: e.g. NH3 at 1K and 5T B-field, P = 85%

The DREAM: Pure Hgas Target in Storage Ring

For H beam 4x1016/s-cm-2, v=2000m/starget density ~2x1011 cm-2

1984 Experiment at Stanford (-scattering) 4 counts per HOUR!1985 Novosibirsk 290 MeV ring, 0.3A electrons1990 COSY 1-3.3 GeV/c“jet target”

H0

PARTICLEBEAM

Recyle, don’t waste!

“Storage Cell”

10cm

3x1016 H/s

target thickness 1013 Hcm2

(100-times better than jet!)

Beam tube

feed tube

Carcasonne (Fr)

Actually a 13th century idea …

“Storage Cell” in Medieval Warfare

10cm

3x1016 H/s

target thickness 1013 Hcm2

(100-times better than jet!)

Beam tube

feed tube

Carcasonne (Fr)

Tool: Recyling of atoms - “Storage Cell” Target

expected target thickness 1013 Hcm2

(100-times better than jet!)

10cm

3x1016 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 depolarizationTeflon-coated cell permits coolingNo radiation damageLong beam life time

Target thickness: 5x1013 atoms/cm2

Two states: 1014 atoms/cm2

Novosibirsk 1989 VEEP-3 e-d

Improved atomic beam ->

permanent magnetsextupole - 1.7 Tgradient 5.7 T/cm

Atomic-beam improvements

From 1 to 10x1016 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.) -> 12x1016 atoms/s.

-> absolute beam polarization calibration at high energy (Y. Makdisi 3:40 pm)

permanent magnetsextupole - 1.7 Tgradient 5.7 T/cm

Atomic-beam improvements

From 1 to 10x1016 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 polarizationRapid polarization cyclingLarge 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).