Polarisation Experiments in Storage Rings

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1 COSY Summer Student Program 2004 Polarisation Experiments in Storage Rings Frank Rathmann Institut für Kernphysik Forschungszentrum Jülich Jülich, September 14, 2004 Frank Rathmann Polarisation Experiments in Storage Rings 1

2 Past ~15 years, tremendous progress in spin-physics experiments with polarized beams on internal targets Near future exploitation at COSY Experimental and theoretical developments pave the way to Future Hadron Physics programs at FAIR Introduction Hadronic Probes: IUCF-PINTEX: Proton-Proton Elastic NN NNπ Proton-Deuteron Elastic COSY EDDA: Proton-Proton Elastic Time-Reversal Invariance ANKE: Proton-Deuteron Breakup Proton-Neutron Elastic - WASA: -Parity of θ+ RHIC-SPIN Electromagnetic Probes: Bates-BLAST Novosibirsk-VEPP-3 HERA-HERMES Frank Rathmann Polarisation Experiments in Storage Rings 2

3 Outline Basics Medieval Warfare Storage Rings and Internal Targets Polarimetry Selected Experimental Results Production of Polarized Antiprotons Medical Application of Polarized Targets Frank Rathmann Polarisation Experiments in Storage Rings 3

4 Basics: Polarization Spin s: 2s+1 possible orientations along quantization axis z spin ½ 2 orientations spin 1 3 orientations magnetic quantum number m=s z (z-component in units of hbar) s=½ m=-½ N - m=+½ N + Two numbers N - and N + fully characterize the beam. Usually linear combinations are used: Intensity I = N - + N + Polarization P z = (N + -N - )/(N + + N - ) -1 P z +1 z Frank Rathmann Polarisation Experiments in Storage Rings 4

5 Basics: continued s=1 z m=-1 N - m=0 N 0 m=+1 N + Three numbers N -, N 0 and N +, or linear combinations: Intensity I = N - + N 0 + N + Vector Polarization P z = (N + -N - )/(N + + N 0 + N - ) -1 P z +1 Tensor Polarization P zz = (N + -2 N 0 +N - )/(N + + N 0 + N - ) -2 P zz +1 Q: What is P z if P zz =0? A: -2/3 P z +2/3 Frank Rathmann Polarisation Experiments in Storage Rings 5

6 Basics: continued P zz = 0 N + -2 N 0 =0 N + =2 N 0 P z = (N + -N - )/(N + + N 0 + N - ) = 2 N 0 /(2N 0 + N 0 ) = +2/3 (other case analog) Frank Rathmann Polarisation Experiments in Storage Rings 6

7 Example: ½+0 ½+0 Basics: A Polarization Experiment Target 4 He, 12 C proton beam θ θ Left Scattering Plane Right Experiment measures asymmetry N L N R ε = Py A y = N + N L R Analyzing Power A y (θ,e) Beam Polarization Approximation N L ~N R ~N A y = P 1 1 ~ 2 N P I A y =0.1 N(~t) P=1 50 P=½ 200 FOM=P 2 I Frank Rathmann Polarisation Experiments in Storage Rings 7

8 Basics: Spin-dependence of NN interaction Description of Interaction between Nucleons requires spin-orbit term in the NN potential r r V LS (r)(l S) r L = r r p Left-Right Asymmetry to scattering plane Frank Rathmann Polarisation Experiments in Storage Rings 8

9 Outline Basics Medieval Warfare Storage Rings and Internal Targets Polarimetry Selected Experimental Results Production of Polarized Antiprotons Medical Application of Polarized Targets Frank Rathmann Polarisation Experiments in Storage Rings 9

10 Carcassonne South of France, between Toulouse and the Mediteranian Frank Rathmann Polarisation Experiments in Storage Rings 10

11 Carcassonne Philippe III (the Strong) built the fortress ( ). Frank Rathmann Polarisation Experiments in Storage Rings 11

12 Medieval Warfare Figure from Willy Haeberli Workshop on Polarized Sources and Targets Erlangen, Germany (1999) Multiple use of a projectile oscillating in a potential well. Frank Rathmann Polarisation Experiments in Storage Rings 12

13 Internal Target in a Storage Ring H, H, r D, etc. 3 D, r He r Target Beam orbiting beam of projectiles Storage Ring: Re-usable Projectiles Carcassonne application (type 1) Frank Rathmann Polarisation Experiments in Storage Rings 13

14 External vs Internal New approach (~15 years) to scattering experiments L=I beam d t Target atoms (cm -2 ) L=10 34 cm -2 s -1 L=N stored f rev d t Projectiles (s -1 ) Frank Rathmann Polarisation Experiments in Storage Rings 14

Parity WASA-COSY with a polarized gas target C. Hanhart et al., PLB 590 (2004) 39 d t =0.93g/cm 3 0.8cm =0.74g/cm 2 =3.7 10 23 nucl./cm 2 I=5 10 6 s -1 FOM=(3/17 0.

15 Example: Parity of θ + Pentaquark Double polarization experiment fixes parity of θ + free of any model! Spin-correlation coefficient A xx in pp θ + Σ + TOF-COSY with a NH 3 polarized target A xx neg. Parity 50 Q [MeV] pos. Parity WASA-COSY with a polarized gas target C. Hanhart et al., PLB 590 (2004) 39 d t =0.93g/cm 3 0.8cm =0.74g/cm 2 = nucl./cm 2 I= s -1 FOM=(3/17 0.6) 2 d t I = cm -2 s x shorter measurement time d t,jet =10 12 nucl./cm 2 d t,cell = nucl./cm 2 I= s -1 FOM Jet =(0.8) 2 d t,jet I = cm -2 s -1 FOM Cell = cm -2 s -1 Frank Rathmann Polarisation Experiments in Storage Rings 15

16 Polarized Storage Cell Target Atomic Beam Projectile beam Atomstrahl pumped away After wall collisions, atoms can intercept beam again. Cell Target: Re-usable target atoms Carcassonne application (type 2) Frank Rathmann Polarisation Experiments in Storage Rings 16

17 Principle of a polarized internal target Target Source Detector Beam Storage Cell Polarimeter Interaction Region point-like 5-10 mm free jet low density cm -2 extended mm storage cell high density cm -2 Frank Rathmann Polarisation Experiments in Storage Rings 17

18 Principle of a polarized internal target Target Source Detector Distinct advantages over solid or high pressure targets: rapid reversal of target spin (x,y,z): In H/D up to 100 Hz achieved Beam Polarimeter Storage Cell isotopically pure, no contamination by unpolarized components in the target low background due to absence of container walls no radiation damage, target gas replenished every few ms Ideally suited for high precision experiments Frank Rathmann Polarisation Experiments in Storage Rings 18

19 Four main types of sources for PIT s Atomic beam source 2 Ultra-cold source SC Coil W +1/2 extracted -1/2 trapped z Atoms with m j =+½ focused in sextupole magnets. RF transitions select HFS. W thermal W magnetic One electron spin state m j =½ extracted from strong solenoid field and focused Frank Rathmann Polarisation Experiments in Storage Rings 19

20 Main types of sources (cont d) 3 Spin-Exchange source 4 3 He source K + D spin-exchange K + D 3 3 He(2 S 1) 3 metastable He(g.s.) exchange collisions OP OP Deuterium or Hydrogen atoms polarized by spin-exchange with optically pumped potassium vapor Small fraction of metastable 3 He (2 3 S 1 ) atoms pumped with laser optical pumping. Ground state atoms polarized via exchange collisions Frank Rathmann Polarisation Experiments in Storage Rings 20

21 Stern-Gerlach Experiment (1922) beam of Silver atoms z magnetic field with gradient db/dz 0 Intensity Magnet on Magnet off Aperture electromagnet glass plate Frank Rathmann Polarisation Experiments in Storage Rings 21

22 Spin-Selection Selection Deflection through interaction between magnetic field and magnetic dipole moment of silver atoms. potential Energy Force r v U = µ B = F du dz z = = µ u z z B db dz classically: Smearing of atoms over area Silver atoms possess same dipole moment, as single electron, one component m s =+½ ( ) other one m s =-½ ( ). Frank Rathmann Polarisation Experiments in Storage Rings 22

23 Erlangen (Birthplace of polarized Sources) Prof. Rudolph Fleischmann ( ): Selection of H-Atoms, in the gradient field of a Quadrupol B~r F=const. Frank Rathmann Polarisation Experiments in Storage Rings 23

24 Nuclear Polarization W=h MHz ( ev) B c =50.7 mt Target holding field Hyperfine Transitions (1-3) or (2-4) enable to make beams of ONE state only. Frank Rathmann Polarisation Experiments in Storage Rings 24

25 Modern Sources Use of Permanent- Sextupoles (VAC): B~r 2 F~r One quadrant I= H/s Frank Rathmann Polarisation Experiments in Storage Rings 25

26 Exact caclulations Progress since 1956 ~ 10 6 more Flux of atoms Frank Rathmann Polarisation Experiments in Storage Rings 26

27 Outline Basics Medieval Warfare Storage Rings and Internal Targets Polarimetry Selected Experimental Results Production of Polarized Antiprotons Medical Application of Polarized Targets Frank Rathmann Polarisation Experiments in Storage Rings 27

28 Polarimetry of PIT s Three different approaches are distinguished: I. Calibration by a known reaction FILTEX test (αp scattering) pp elastic scattering (PINTEX at IUCF) II. Ion extraction NIKHEF Ion extraction polarimeter III. Neutral gas extraction Breit-Rabi Polarimeter for HERMES Lamb-shift Polarimeter for ANKE Method I does not distinguish atoms from molecules or any other material in the target 1 st choice where applicable Methods II and III measure the polarization of atoms in the target, with additional instrumentation also the degree of dissociation in the target but: Molecules dilute the polarization! and: What is the polarization of the molecules? (ISTC Project) Frank Rathmann Polarisation Experiments in Storage Rings 28

29 Ex. 1: αp p scattering at 27 MeV Apparatus for Filtex test at TSR Frank Rathmann Polarisation Experiments in Storage Rings 29

30 FILTEX Results Sept. 2, 1992 Oct. 1, 1992 FOM T opt = 125 K P = 0.80 ± 0.02 P = 0.79 ± 0.02 d t = (5.4 ± 0.3) /cm 2 d t = (5.4 ± 0.3) /cm 2 No radiation damage of the wall coating Frank Rathmann Polarisation Experiments in Storage Rings 30

31 Ex. 2: PINTEX pp elastic scattering (IUCF) Beam Intensity: 2 HFS H/s Polarization: P max =0.87 Dissociator Sextupole Magnets MFT Cooler Beam Storage Cell & Recoil detectors Weak guide-field ( 3 G) Frank Rathmann Polarisation Experiments in Storage Rings 31

32 T= MeV Conservation of Polarization in a Storage Ring Indiana Cooler H.O. Meyer et al., PRE 56, 3578 (1997) Frank Rathmann Polarisation Experiments in Storage Rings 32

33 Target Polarization vs time and vs z Q=½(Q x +Q y ) no radiation damage! no change of Q along cell Prob depol /bounce=1/5000 with I beam = µa L = cm -2 s -1 Frank Rathmann Polarisation Experiments in Storage Rings 33

34 Spincorrelation Parameters Before W. Haeberli et al., PRC 55, 597 (1997) F. Rathmann et al., PRC 58, 658 (1998) B.v. Przewoski et al., PRC 58, 1897 (1998) B. Lorentz et al., PRC 61, (2000) After Relativ statistical error of the normalization δk/k (%) Frank Rathmann Polarisation Experiments in Storage Rings 34

35 Ex. 3: NIKHEF Ion-extraction polarimeter Principle based on Price & Haeberli Z.L. Lou et al, Nim A 379 (1996) NIM A 326 (1993) Measurement of Tensorpolarization via 3 r H(d, n) 4 He Frank Rathmann Polarisation Experiments in Storage Rings 35

36 Ex. 3: NIKHEF Ion-extraction polarimeter Ionization in AmPS via stored e - : σ(1 kev)/ σ(565 kev) ~1/50 Z.L. Lou et al, Nim A 379 (1996) Polarized Ion Measurement with a prototype 0.89 ± 0.03 stat. ± 0.01 stat. ± 0.05 syst. < Pzz < ± 0.03 syst. Frank Rathmann Polarisation Experiments in Storage Rings 36

37 Ex. 4: HERMES Breit-Rabi Polarimeter Determination of Hyperfine state population numbers by RF transitions sextupole magnet system Frank Rathmann Polarisation Experiments in Storage Rings 37

38 Polarized Internal Target for ANKE Atomic Beam Source 3 magnets form a schikane Spectrometer magnet D2 moves transversly Lamb-Shift Polarimeter Frank Rathmann Polarisation Experiments in Storage Rings 38

39 Outline Basics Medieval Warfare Storage Rings and Internal Targets Polarimetry Selected Experimental Results Production of Polarized Antiprotons Medical Application of Polarized Targets Frank Rathmann Polarisation Experiments in Storage Rings 39

40 Polarization Buildup: General Features I σ tot = σ 0 + σ P Q + σ (P k)(q k) P beam polarization Q target polarization k beam direction For initially equally populated spin states: (m=+½) and (m=-½) transverse case: longitudinal case: σ tot ± = σ 0 ± σ Q σ tot ± = σ 0 ± ( σ + σ ) Q τ I I beam τ + pol = = (t) = (t) = ( σ σ 0 pol 1 + σ ) d I0 e 2 I0 e 2 τ τ c 1 Q d t t beam t beam f t rev e e f rev t τ pol t + τ pol Time dependence of P, I, and FOM P(t) = I I I(t) = I I + I + I = FOM(t) = t = tanh τ I 0 e P(t) τ 2 t beam pol I(t) t cosh τ pol Frank Rathmann Polarisation Experiments in Storage Rings 40

41 Polarization Buildup: General Features II statistical error of a double polarization observable (A TT ) δ A TT 1 = P Q N (N ~ I) Measuring time t to achieve a certain error δ ATT t ~ FOM = P 2 I Optimimum time for Polarization Buildup given by maximum of FOM(t) t filter = 2 τ beam I/I Beam Polarization t/τ beam Frank Rathmann Polarisation Experiments in Storage Rings 41

42 1992 Filter Test at TSR with protons Experimental Setup Results T=23 MeV F. Rathmann. et al., PRL 71, 1379 (1993) Low energy pp scattering σ 1 <0 σ tot+ <σ tot- Expectation Target Beam Frank Rathmann Polarisation Experiments in Storage Rings 42

43 Experimental Setup at TSR (1992) Frank Rathmann Polarisation Experiments in Storage Rings 43

Beam Polarization in a dedicated Antiproton Polarizer Polarisation buildup through spin transfer Beam Polarization P(2 τ beam ) 0.4 0.3 0.2 0.

44 Beam Polarization in a dedicated Antiproton Polarizer Polarisation buildup through spin transfer Beam Polarization P(2 τ beam ) r p + e p + e r Horowitz & Meyer, PRL 72, 3981 (1994) H.O. Meyer, PRE 50, 1485 (1994) ψ acc (mrad) T (MeV) PAX will exploit spin-transfer to polarize antiprotons and to do Spin-Physics at the HESR Frank Rathmann Polarisation Experiments in Storage Rings 44

45 Outline Basics Medieval Warfare Storage Rings and Internal Targets Polarimetry Selected Experimental Results Production of Polarized Antiprotons Medical Application of Polarized Targets Frank Rathmann Polarisation Experiments in Storage Rings 45

46 Polarized 3 He for NMR s of the human lung (Werner Heil) Spin-Off of Polarized Gas Target Technology Human Lung with 0.7 bar liter of polarized 3 He P H ~ µ B/kT ~ P He ~ 1 ρ H /ρ He ~ 2500 signal P µ ρ S/S H > 10 Proton - MRI (1 H) Helium - MRI ( 3 He) DKFZ, HD Nov. 1995; Lancet 1996 amount of gas: 1 bar liter Frank Rathmann Polarisation Experiments in Storage Rings 46

47 Transport time: Mainz-Sheffield :10 h Mainz-Copenhagen : < 7 h Mainz-Orsay ( Paris ): 8 h T 1 ~160 h Frank Rathmann Polarisation Experiments in Storage Rings 47

48 Funktionelle NMR mit 3 He Frank Rathmann Polarisation Experiments in Storage Rings 48

49 Final Remark In 1981 Rudolf Fleischmann ( ) Professor of Physics in Erlangen originator of the first polarized atomic beam source (1956) asked himself at a conference, why progress in physics sometimes was so slow and took so many roundabouts. It seems to me that the main reason is that too much confidence is put in theoretical, and therefore quite hypothetical concepts and models, which are popular during the corresponding period and that it is very difficult to free oneself from them. from D. Fick, Talk held on in the Physics Colloquium at University of Erlangen Frank Rathmann Polarisation Experiments in Storage Rings 49

Towards Polarized Antiprotons at FAIR

Towards Polarized Antiprotons at FAIR http://www.fz-juelich.de/ikp/pax Frank Rathmann Institut für Kernphysik Forschungszentrum Jülich Kyoto, October 3, 2006 Outline PAX physics program Accelerator configuration