An RF Wien Filter as Spin Manipulator MT Student Retreat 2015

Transcription

1 An RF Wien Filter as Spin Manipulator MT Student Retreat 2015 Hamburg, February 23, 2015 Sebastian Mey Forschungszentrum Jülich

2 Content The RF-ExB Dipole Spin Motion in an RF-Wien-Filter Measurements Conclusion Hamburg, February 23, 2015 The RF-ExB Dipole 2

3 The RF-ExB Dipole shielding Box RF-B Dipole RF-E Dipole ferrite blocks two electrodes in vacuum camber distance 54 mm, length 580 mm coil: 8 windings, length 560 mm ceramic beam chamber two separate resonance circuits Hamburg, February 23, 2015 s.mey@fz-juelich.de The RF-ExB Dipole 3

4 RF-B Circuit * signal gen. (k-γg)f R +50 db max. 500W dir. coupler -30 db C S P IN P REF 500 pf RF-B dipole 30 µh oszi C P R P 5000 pf 10 kω current trafo 0.1 V/A amplitude limited by losses Î max 5 P in 90 W matching to 50 Ω with bidirectional coupler frequency range 630 khz khz current in coil directly available via current transformer [* A. Schnase, RF-Dipole System at COSY for spin-flipping experiments, IKP Annual Report 2002] Hamburg, February 23, 2015 s.mey@fz-juelich.de The RF-ExB Dipole 4

5 RF-E Circuit signal gen. dir. coupler (k-γg)f R +50 db -30 db RF-E dipole 220 pf max. 500W C S IN REF 500 pf 1000:1 Voltage div. 100 nf 1 MΩ 100 pf oszi C P 5000 pf R P 20 kω L P 10 µh 1:4 BalUn 1000:1 voltage div. 100 pf 100 nf 1 MΩ Û max 2 P in 90 W frequency range 630 khz khz electrode voltage directly available via capacitive voltage divider Hamburg, February 23, 2015 s.mey@fz-juelich.de The RF-ExB Dipole 5

6 Lorentz Force Compensation eê y ecβˆbx F y = e (Ê y + cβ ˆBx ) β β z = 0.459; Î = 1 A; ˆBx dz T mm Û = 395 V; Êy dz = 4818 V simulated optimization for integral compensation along beam path ˆFy dz = 0 ev/m Hamburg, February 23, 2015 s.mey@fz-juelich.de The RF-ExB Dipole 6

7 Content The RF-ExB Dipole Spin Motion in an RF-Wien-Filter Measurements Conclusion Hamburg, February 23, 2015 Spin Motion in an RF-Wien-Filter 7

8 Thomas-BMT Equation in Case of a Wien-Filter consider device with pure radial magnetic and vertical electric field adjust net Lorentz force to zero = β B E c Thomas-BMT Eq.: d S dt = e m S Ω MDM E β/c β z y E/c x B Ω = (1 + γg) B + (1 + G) B 0 ( γ ( ) = 1 β2 γ + γ+1 (1 β2 )γg B = 1+G γ B = β ( β B)=β 2 B {}}{ ) + β γ+1 γg E c Hamburg, February 23, 2015 s.mey@fz-juelich.de Spin Motion in an RF-Wien-Filter 8

9 Spin-Resonance Strength of an RF-Wien-Filter * particles sample localized RF field once each turn at orbit angle θ b(θ) = ˆB dl cos( f RF f rev θ + φ) n= δ(θ 2πn) intrinsic resonance strength given by spin rotation by turn, calculate with Fourier integral over driving fields along orbit : ɛ k = f spin = 1+G 2πγ = 1+G 2 2πγ f rev = 1+G b(θ) 2πγ Bρ eik θ dθ ˆB dl Bρ n= cos(2πn f RF f rev ˆB dl Bρ [* S. Y. Lee, /PhysRevSTAB (2006)] + φ)e i2πkn ( ) n e±iφ δ(n K f RF Hamburg, February 23, 2015 s.mey@fz-juelich.de Spin Motion in an RF-Wien-Filter 9 f rev )

10 Resonance Condition spin tune given by γg, resonance at every sideband with K! = γg = n ± f RF f rev f RF = f rev n γg ; n Z d at 970 MeV/c: β = 0.459; γ = 1.126; G = ; f rev = 750 khz; γg = : n f RF / khz Hamburg, February 23, 2015 s.mey@fz-juelich.de Spin Motion in an RF-Wien-Filter 10

11 Content The RF-ExB Dipole Spin Motion in an RF-Wien-Filter Measurements Conclusion Hamburg, February 23, 2015 Measurements 11

12 Polarimetry and Beam Setup massive carbon target with slow extraction polarization rate asymmetries in 12 C( d, d) : P y N left N right N left +N right use Cross Ratio to suppress offset and first order systematic errors CR y = r 1 r + 1 ; r 2 = L( )R( ) L( )R( ) Beam Target position along ring / m bunch-shape evolution per fill time in cycle / s Hamburg, February 23, 2015 s.mey@fz-juelich.de Measurements 12 all events left, right up, down

13 Field Compensation Phase 30% Output Amplitude, Natural Beamloss (38.2±1.1)% measurement on betatron frequency for max. sensitivity polarimeter target directly above beam-pipe-center as defining acceptance exited part of beam is removed diagnosis with COSY beam current transformer determination of amplitudes and phase corresponding to Lorentz force compensation down to per mille! fqy = khz, f = khz, Î RF-B = (232.6±0.6) ma, Û RF-E = (132.0±0.3) V rel. beam loss / % beam loss w. o. RF ExB 38.2 ± 1.1 % preliminary data Input φ(e-b) / Amplitude 30% Output Amplitude, Natural Beamloss (38.2±1.1)% rel. beam loss / % fqy = khz, f = khz, Î RF-B = (232.5±0.6) V, Input φ(e-b) = 90 beam loss w. o. RF ExB 38.2 ± 1.1 % preliminary data Û RF-E / V Hamburg, February 23, 2015 s.mey@fz-juelich.de Measurements 13

14 Measurement of Resonance Strength Run3577 fpy: Hz, τ: s Run3584 fpy: Hz, τ: s fpy = Hz at f RF = khz min CR y 0.3 CR y fpy / Hz 0.4 χ 2 / ndf / 3 Curvature Minimum at 1.73e+06 ± ± 9.91e e χ / ndf / χ / ndf / Offset ± cos Offset ± cos Phase ± cos Freq / Hz ± exp scale ± exp τ / s 6.64 ± cos Offset ± cos Phase ± 4.81 cos Freq / Hz ± exp scale ± exp τ / s ± t / s t / s 0.3 CR y 0.3 Run3585 fpy: Hz, τ: s CR y 0.3 Run3574 fpy: Hz, τ: s χ / ndf / 95 cos Offset ± cos Phase ± 4.50 cos Freq / Hz ± exp scale ± exp τ / s 4.68 ± t / s χ / ndf / 95 cos Offset ± cos Phase ± 8.89 cos Freq / Hz ± exp scale ± exp τ / s ± t / s f RF =(1-Gγ)f / khz rev total spin flip only on resonance average polarization 0 minimum of vertical polarization oscillation frequency resonance strength ε = f Py min f rev Hamburg, February 23, 2015 s.mey@fz-juelich.de Measurements 14

15 Preliminary result of Fixed Frequency Scans RF-solenoid: f Py 1+G RF-dipole: f Py 4π 1+γG 4π ˆB dl ˆB dl Bρ Bρ ; RF-Wien-Filter: f P y 1+G 4πγ ˆB dl Bρ + interference from beam oscillations (2-qy)frev / khz preliminary data qy Hamburg, February 23, 2015 s.mey@fz-juelich.de Measurements 15 fpy / Hz

16 Content The RF-ExB Dipole Spin Motion in an RF-Wien-Filter Measurements Conclusion Hamburg, February 23, 2015 Conclusion 16

17 Conclusion RF-ExB dipole acting on MDM with minimal disturbance has been successfully commissioned RF-B amplitude: ˆBx dz 0.18 T Î max = 5 A RF-E amplitude: Ê y dz 24 Û max = 1975 V ±1 spin harmonics at 629 khz and 871 khz available for studies field strengths necessary for spin manipulation ( 0.01 T mm) available at very low input powers ( 10 W) Wien filter as RF spin manipulator is a concept that works high precision version with stripline layout scheduled for commissioning in Septermber 2015 [* see talk given by J. Slim] Hamburg, February 23, 2015 s.mey@fz-juelich.de Conclusion 17

18 Content The RF-ExB Dipole Spin Motion in an RF-Wien-Filter Measurements Conclusion Hamburg, February 23, 2015 Spares 18