P. Hautle, Santa Fe Polarized Drell-Yan Physics Workshop, Nov 2010 AFP – a fast & easy nuclear polarization reversal ? P. Hautle Paul Scherrer Institut CH-5232 Villigen PSI Switzerland Santa Fe Polarized Drell-Yan Physics Workshop October 31- November 1, 2010 Santa Fe, NM 87501, USA

P. Hautle, Santa Fe Polarized Drell-Yan Physics Workshop, Nov 2010 Outline Introduction polarised targets = unique DNP systems Overview of Experimental Data overview of experimental data some details / comments AFP Theory thermodynamic of a nuclear spin system classical picture - rotating frame quantum statistical description – spin temperature which effects set limits on the optimum efficiency Implementation technical and physics constraints what can be expected

P. Hautle, Santa Fe Polarized Drell-Yan Physics Workshop, Nov 2010 PSI East PSI West Aare SLS cw Proton accelerator (590 MeV, 2.2 mA) ( , ,  SR  SINQ, UCN) SwissFEL Accelerator Facilities

P. Hautle, Santa Fe Polarized Drell-Yan Physics Workshop, Nov cm 3 „Frozen Spin“ Polarised Target Particle physics experiments on beams of pions, protons, neutrons…..

P. Hautle, Santa Fe Polarized Drell-Yan Physics Workshop, Nov μm thick polystyrene foil cooled to 200 mK by a sub micron thick film of superfluid 4 He cell with two 500 nm thick Si 3 Ni 4 windows “Ultra-thin” polarised solid target [J.P Urrego Blanco et al., NIM B 261 (2007) 1112]

P. Hautle, Santa Fe Polarized Drell-Yan Physics Workshop, Nov 2010 suppress background scattering by TOF coincident in situ detection of low energy recoil protons in the target itself polarised nuclei in the scintillating detector itself O N H C H C n CH 3 O N · B. van den Brandt et al., NIM A 446 (2000) 592

P. Hautle, Santa Fe Polarized Drell-Yan Physics Workshop, Nov 2010 Beam Detector neutron beam Observe DNP build up with small angle neutron scattering through spin contrast variation Europhys. Lett. 59 (2002) 62 Eur. Phys. J. B 49 (2006) 157–165 J. Appl. Cryst. 40 (2007) s106-s110

P. Hautle, Santa Fe Polarized Drell-Yan Physics Workshop, Nov 2010 B 0 =2.5T 58 mm d-PS target doped with d-TEMPO Ø 5 mm x 1.2 mm 6 LiF targetholder 45 mm Pseudomagnetic precession of cold neutrons [F. M. Piegsa et al., NIM A 611 (2009) 231]

P. Hautle, Santa Fe Polarized Drell-Yan Physics Workshop, Nov 2010 Dissolution DNP for MRI / NMR Polarize organic samples labeled with 13 C, 6 Li, 15 N nuclei in solid state (1 K / 5T) image of brain metabolism Dissolve rapidly and inject into rat in imager (9.4 T) => image of brain metabolism Details and List of publications see: http//: sdnpi.epfl.ch

P. Hautle, Santa Fe Polarized Drell-Yan Physics Workshop, Nov 2010 Nuclear Spin Thermodynamics

P. Hautle, Santa Fe Polarized Drell-Yan Physics Workshop, Nov 2010 equation of motion External field ( ~ T) including rf field (~ G) “Local field” which spin i feels because of neighbours (averaged over all orientations and spin states) ~ few G Nuclear spin system (in a solid) in external field FWHM (Gaussian) Magnetization

P. Hautle, Santa Fe Polarized Drell-Yan Physics Workshop, Nov 2010 Energy – Entropy – Isentropic cooling Curie Law Energy Entropy Applied fieldLocal field constant Isentropic cooling Adiabatic demagnetization (spin energy / thermal energy)

P. Hautle, Santa Fe Polarized Drell-Yan Physics Workshop, Nov 2010 Isentropic cooling – Adiabatic demagnetization constant HLHL H0H0 precession about H 0 H 0 is decreased precession about H L Important change when H 0  H L : Entropy transferred from polarizationspin-spin ordering polarization to spin-spin ordering Reversibility: Reversibility: change of H 0 slow compared to equilibration time (  H L )  1

P. Hautle, Santa Fe Polarized Drell-Yan Physics Workshop, Nov 2010 Adiabatic fast passage (AFP)

P. Hautle, Santa Fe Polarized Drell-Yan Physics Workshop, Nov 2010 rf field - Rotating frame of reference [F. Bloch, Phys Rev 70 (1946) 460] [A. Abragam, Principles of Nuclear Magnetism, 1961] rotating frame External field rf field contains rf field Larmor frequency: static field:rf field: H1H1 HeHe H 0  ω/γ H0H0

P. Hautle, Santa Fe Polarized Drell-Yan Physics Workshop, Nov 2010 rf field - Rotating frame of reference [F. Bloch, Phys Rev 70 (1946) 460] [A. Abragam, Principles of Nuclear Magnetism, 1961] rotating frame External field rf field contains rf field Larmor frequency: static field:rf field: H1H1 HeHe H 0  ω/γ H0H0 H e can be rotated by 180° sweeping H 0 or ω through resonance

P. Hautle, Santa Fe Polarized Drell-Yan Physics Workshop, Nov 2010 Adiabatic Theorem equation of motion For any vector satisfying a similar equation of motion the angle between and remains constant provided the change of direction of in time is sufficiently slow Possible to reverse the magnetization What happens to the magnetization ? Adiabatic Adiabaticity: Fast Faster than relaxation:

P. Hautle, Santa Fe Polarized Drell-Yan Physics Workshop, Nov 2010 Adiabatic Theorem equation of motion For any vector satisfying a similar equation of motion the angle between and remains constant provided the change of direction of in time is sufficiently slow Possible to reverse the magnetizationconstant What happens to the magnetization ? Thermodynmics in solid sample Adiabtic demagnetization in the rotating frame (ADRF) Isentropic passage Important change when H e  H LR : Entropy transferred from polarizationspin-spin ordering polarization to spin-spin ordering (Zeeman to dipolar ordering) Adiabatic Adiabaticity: Fast Faster than relaxation:

P. Hautle, Santa Fe Polarized Drell-Yan Physics Workshop, Nov 2010 Estimate the losses - AFP in the spin temperature model [M. Goldman et al., Phys Rev 168 (1968) 301] Provotorov equations describe mixing between Zeeman and spin-spin subsystem: Conditions: High temperatures Low nuclear polarizations Mixing rate: AFP: AFP: variation of  very small during time T 2  D  Evolution of inverse spin temperatures  and  to common value

P. Hautle, Santa Fe Polarized Drell-Yan Physics Workshop, Nov 2010 Sweep of field / frequency through the resonance Fast sweepshorter Fast sweep – in time much shorter than mixing time W  1 Slightly saturating passage H1H1 Quasiadiabatic fast passagelonger Quasiadiabatic fast passage – in time much longer than mixing time W  1 Quasiadiabatic part Relaxation Sudden to adiabatic transition ~ 5 – 8 % loss, almost independant of Spin-lattice relaxation of the spin-spin (dipolar) interactions

P. Hautle, Santa Fe Polarized Drell-Yan Physics Workshop, Nov 2010 Spin-lattice relaxation in the rotating frame Theoretical prediction Sample temperature & dopant concentration !! narrow line width long relaxation time in RF = Spin-lattice relaxation of the spin-spin system

P. Hautle, Santa Fe Polarized Drell-Yan Physics Workshop, Nov 2010 Experimental results I - Protons effect of sample temperature

P. Hautle, Santa Fe Polarized Drell-Yan Physics Workshop, Nov 2010 Experimental results II – 7 LiH

P. Hautle, Santa Fe Polarized Drell-Yan Physics Workshop, Nov 2010 Experimental results III substancenucleusdopant e- conc. [spins/g] T [K]  P max 1-butanol 1H1Hporphyrexide4.0 x  butanol 1H1HCrV EHBA4.0 x  LiH 7 Li irradlow ?0.08  H1H  fluoro-pentanol 19 F TEMPO2.0 x  H1H  0.40 d-butanol 2H2H CrV EDBA6.35 x  H2H0.5  H2H0.08  0.90 d-butanol 2H2HCrV EDBA2.36 x  0.92 Deuterated alcohols are a different story: large quadrupolar coupling small dipolar coupling 1 and ½ sweep to reverse the polarization of the spin 1 system

P. Hautle, Santa Fe Polarized Drell-Yan Physics Workshop, Nov 2010 Experiment & Theory Data fitted with spin temperature model

P. Hautle, Santa Fe Polarized Drell-Yan Physics Workshop, Nov 2010 Sample temparature / dopant concentration d-butanol + EHBA(Cr V )-d 22 increase sweep rate for higher temperatures

P. Hautle, Santa Fe Polarized Drell-Yan Physics Workshop, Nov 2010 Line width / Polarization FWHM (Gaussian)   50 kHz  H LR = 2.9 G

P. Hautle, Santa Fe Polarized Drell-Yan Physics Workshop, Nov 2010 Line width / Polarization FWHM (Gaussian)   50 kHz  H LR = 2.9 G

P. Hautle, Santa Fe Polarized Drell-Yan Physics Workshop, Nov 2010 Two nuclear spin species Coupling of the nuclear spin systems through electron non-Zeeman system start microwaves [Cox, Bouffard, Goldman, J Phys C 6 (1973) L100] polarization of both nuclear spin systems should be reversed heat capacity !

P. Hautle, Santa Fe Polarized Drell-Yan Physics Workshop, Nov 2010 In practice: polarization reversal AFP vs DNP T =80 mK / B = 2.5 T gain can be dramatic in certain cases (especially at low temperatures) DNP reversal AFP reversal AFP efficiency DNP build up time

P. Hautle, Santa Fe Polarized Drell-Yan Physics Workshop, Nov 2010 radiation damping asymmetry of efficiency superradiance e.g. typical AFP parameters for protons: Technical aspects I requirements challanges solutionstune and match the rf coil ? B 1 = 0.3 G perpendicular to static field B 0 homogeneity  B 1 /B 1 ~ 0.5 dB/dt = 10 – 20 G/s or 40 – 80 kHz/s frequency sweep width = 400 kHz – 1 MHz produce the required B 1 amplitude do not excessively heat the sample potential pitfalls

P. Hautle, Santa Fe Polarized Drell-Yan Physics Workshop, Nov 2010 Technical aspects II radiation damping -> superradiance threshold electromagnetic energy provided by the spins compensates losses in the circuit auto-oscillation Two coupled systems: resonance circuit rotating magnetization damping time constant [S. Bloom, J Appl Phys 28 (1957) 800] [M. Odehnal, V. Petricek, Physica 67 (1973) 377] [Yu. F. Kiselev et al., JETP 67 (1988) 413] AFP gets asymmetric superradiance superradiant polarization reversal  [L.A. Reichertz et al., NIM A 340 (1994) 278] (NH 3, V = 6.5 cm 3 ; Q = 33)

P. Hautle, Santa Fe Polarized Drell-Yan Physics Workshop, Nov 2010 Technical aspects III Example Example design of a rf irradiation system 5 T / 1 K system (S. Pentilla) magnetic to be rotated to have vertical field sample size polarized target system sample cylinder of 8 cm length/ 1.5 cm diameter ammonia / 6 LiD reversalevery 2 h rf structure rf structure (coil) B 1 ~ 0.3 – MHz G/A large sampletuning not possible (superradiance) solenoid match to 50 Ohm rf power ~ 10 W or more -> heat load !!

P. Hautle, Santa Fe Polarized Drell-Yan Physics Workshop, Nov 2010 AFP used by the Standford group AFP 180° pulse (pulsed NMR) need to excite ~ 100 kHz apply strong pulse: H 1 > H L    5  s B 1  11.7 G [F. Bloch, W.W. Hansen, M Packard, Phys Rev 70 (1946) 474] superradiance !!

P. Hautle, Santa Fe Polarized Drell-Yan Physics Workshop, Nov 2010 Conclusion low temperature, T 1 K low concentration of paramagnetic centers experimental conditions sample properties one „free“ parameter : relaxation time in the rotating frame local field H L line width  (dipolar relaxation time T 1D ) dipolar relaxation time T 1D “Strategy“ to get a high AFP efficiency ?? What can be expected (conservative guess) 6 LiD5 T / 1K  P >  T / 80 mK  P ~  0.9 Ammonia 5 T / 1K  P <  T / 80 mK  P ~  0.7 Trade off between AFP efficiency and DNP build up time

P. Hautle, Santa Fe Polarized Drell-Yan Physics Workshop, Nov 2010