Polarized solid deuteron targets EU-SpinMap Dubrovnik

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1 Experimentalphysik I Arbeitsgruppe Physik der Hadronen und Kerne Prof. Dr. W. Meyer G. Reicherz, Chr. Heß, A. Berlin, J. Herick Polarized solid deuteron targets EU-SpinMap Dubrovnik Polarized Target Nuclear Magnetic Resonance NMR Asymmetry-Method (Line Shape) Deuterated Materials used in different Exp. / Labs Material Investigation: D-Styrene with Trityl Summary 1

2 Polarized Target High magnetic field Low temperature: cryo-system Microwave system DNP P=f B kt Nuclear Magnetic Resonance polarization detection Target material with high content of polarizable nucleus and free e- Slow control and DAQ 3 He/4He or 4He cryo-system Thermometry µ-wave generator NMR T : 1K 50 mk B : T µ-w. : Ghz NMR RF - D : MHz - P : MHz PS magnet 2

3 DNP: Solid State Effect Dipolar coupling positive negative B = 2.5T (T=1K: P-e=93%, Pp=0.26%) 3

4 DNP: Solid State Effect example polarization/% µ - frequency scan for protons in trityl doped propandiol 212 MHz µ-wave frequency 4

5 NMR Applying a static magn. field B0 to a spin ensemble leads to a degeneration into 2s+1 sublevels, the shift of the sublevels is given by Emagn(m)=m ħ ωl (ωl :Larmor-frequency) N2 =e N1 Boltzmann-distribution among the m-sublevels: N m exp [ E magn m /k B T ] s s ℏ L kbt mn m S Z m= s P := = s S S Nm m= s S Z = m= ss ℏ m exp [ E magn m / k B T ] m= s exp [ E magn m / k B T ] 5

6 NMR 2 Brillouin - Function: sz 2s 1 2s =P s= coth coth S 2s 2s 2s 2s g N s B = kbt with T, B,s & g as temperature, magnetic field, spin and g-factor n Magnetization: i M = i V the expectation value of Susceptibility: B 0 M n iz M z = = N P s V i P s M N density of the spins 0 2ℏ s P s= 2 2 ' ' d g N N 0 6

7 TE Method Acquire NMR signals at thermal equilibrium ( T and B are known) Ps= 2s 1 2s coth coth 2s 2s 2s 2s Area under the line shape is proportional to P P TE K= AU TE Dynamical polarization P dyn = K AU dyn 7

8 Asymmetry-Method (Line Shape) -Quadrupol moment interacts with electrical field gradient (if consisting) - 2 transitions (-1 0) and (0 1) - P = f(ratio of the tr. rates) - r = 0.7 -> P = -23.3% H1 r= H2 2 r 1 P= 2 r r 1 - Quadrupol line shape function is fitted to the signal and r is extracted PHD Th. Chr. Dulya 1996 N r 2 r 1 3qR r 1 3qR 1 = F plus R 1 qr F minus R 1 qr Q r r 8

9 Quadrupol Line Shape Fit Method subjects to some conditions dp/dt small (MW switched off) Both transitions must be emancipated For the final factor K, signals from both polarization signs are needed, to get rid of the off set coursed by the false asymmetry Only the slope is from interest 9

10 The deuteron NMR signal with quadrupole interaction The maximum polarizations at B = 2.5T!!! D-Propanediol : D-Butanol : 10

11 EPR lines of dif. Radicals in D-Butanol B=0.33 T B=2.5 T ν [MHz] TEMPO irrad. 6LiD for comparison irrad. trityl EU-SpinMap Workshop Width 0,22 mtdubrovnik 11

12 D-Butanol SMC 1995 Difference P+-P- between the polarizations of the target cells during the 1995 deuteron gd1 measurement P(d)max = 50% Dilution refrigerator Tmin = 60 mk B = 2.5 T FM switched on 12

13 D-Butanol GDH Mainz 2003 D D C D D C D D C D D C O D D Butanol doped with trityl radical Butanol doped with porphyrexid 13

14 6 LiD COMPASS 2006 Preparation by irradiation with electrons (Ee= 20 MeV, T=190K) f = 4/8 = 0.5 (6Li: α + D) Max. Polarization P = >50 % t1(b=1t,t=60mk) = 10kh 14

15 Polystyrene Density: 1.05 g/cm3 Structure formula: (C8D8)n L. Wang et al. High Deuteron Polarization in Trityl Doped D-Polystyrene Will be published soon in NIM 15

16 Doping of D-Polystyrene Solvent: Tetrahydrofuran (THF) EPR spectra of Finland D36 in D-polystyrene with spin concentration spins/g C4H8O Structure Melting point C ( K) Assembly: - D-polystyrene and Finland D36 are dissolved in THF - pour mixture in desired form - wait for evaporation of THF Polarizationresults: field/t T/K P/% ± > ± >

17 D-Materials Material Doping method LiD Irradiation D-Butanol Irradiation 6 B-Field Experiment / Laboratory > 50 % 2.5 T (<0.1 K) COMPASS > 55 % 2.5 T (<0.1 K) Bochum > 70 % 5.0 T (<0.1 K) Bochum abs. max. Polarization ND3 Irradiation > 50 % 3.5 T (0.3 K) Bonn D-Butanol Trityl (chem. dop.) > 80 % 2.5 T (<0.1 K) GDH Mainz D-Propandiol Trityl (chem. dop.) > 80 % 2.5 T (<0.1 K) Bochum D-Styrene Trityl (chem. dop.) > 30 % 2.5 T (0.4 K) Bochum > 60 % 5.0 T (0.4 K) Bochum 17

18 Summary CW-NMR plus line shape fit are the best technique to determine the polarization Deuterated target materials Doped by irradiation Doped by dissolving radicals Depending on material, temperature, magnetic field and doping method very high polarizations are achievable 18

19 Measurement time Calculations are made for same target volume Deuteron materials Material P ρ[g/cm³] f D-Butanol 80% ND3 50% LiD 50% HD 50% D-Polystyrene 60% F[10-2 g/cm³] t/thd 19

20 Radiation length NA =4 r e Z Z 1 ln X0 A Z α fine structure constant re classic radius of electron NA Avogadro -constant A atomic mass Z atomic number X 0= A 2 g cm 287 Z Z 1 ln Z Material ρ [g/cm H-Butanol 0.94 NH D-Butanol 1.07 LiD 0.82 HD X [g/cm ] ]

21 Absorption of Radio Waves n1 h = B 0 n2 Probe w. rf-coil B RF B0 B RF =2 B 1 cos t - Excitation of Zeeman transitions by applying RF - Transition probability n2-n1 (population no.) - Resonance curve has definite width, because db and relaxation processes - Breakdown B RF in rotating fields B RF =B1 e i t B 1 e i t : Bloch B= B1 cos t e x B1 sin t e y B 0 e z d I V = M B dt n M = I i /V = I /V i dm = M B dt M x = B1 M 0 L,0 L,0 2 2 /4 B M 1 M y = T2 L,0 /4 2 = 1 2 B12 T 1 T 2 T2 T1 spin-lattice relax., T2 spin-spin relax. & Γ line width 21

22 CW NMR 0 2ℏ s 2ℏ s P= 2 2 ' ' d 2 2 A g N N 0 g N N A is the area under the signal P=k S d k includes the properties of the material and of the Q-meter Series Q-meter: GV 0 Z, V a, = R0 1 x Z, with x = 1/R0+1/Ri as admittance, G as the gain of the amplifiers and Z(ω, χ) as circuit impedance 22

23 Signal Processing CW-NMR Sweeping frequency over resonance Signal averaging: signal grows with no. of sweeps noise with square root of same Acquire background signal with tuned off B-field Signal minus background Subtracted signal minus baseline (baseline fitted to the wings of the spectra) Sum up the area under the signal P = AUdyn PTE/AUTE 23

24 Sweeping with Online Tuning Serial Q-meter circuit is tuned online Varicap voltage is updated every frequency step higher stability and more homogeneous noise distribution higher S/N 24

25 P

26 P