A Novel RF-ExB Spin Manipulator at COSY Contribution to SPIN2014

Transcription

1 A Novel RF-ExB Spin Manipulator at COSY Contribution to SPIN2014 Beijing, October 21, 2014 Forschungszentrum Jülich Sebastian Mey and Ralf Gebel for the JEDI Collaboration

2 Content The RF-ExB Dipole Spin Motion in an RF-Wien-Filter Measurements Conclusion Beijing, October 21, 2014 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 Beijing, October 21, 2014 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] Beijing, October 21, 2014 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 Beijing, October 21, 2014 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 Beijing, October 21, 2014 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 Beijing, October 21, 2014 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 net Lorentz force can be adjusted to zero E = β B c Thomas-BMT Eq.: E β c d S dt = e γm S Ω Ω =(1 + γg) B + 0 (1 + G) B + E β/c β z y E/c x B ( γ ) E β γ γg c = ( β B) β = β ( β }{{ B) B } ( β β) = β 2 B =0 ( Ω = 1 β2 γ γ (1 β2 )γg ) B = 1 + G B γ Beijing, October 21, 2014 s.mey@fz-juelich.de Spin Motion in an RF-Wien-Filter 8

9 Spin-Resonance Strength of a RF-Wien-Filter * B(t) = ˆB cos(ωrf t + φ) particles sample localized RF field once each turn, define modulation tune ν m = ω RF ω rev b(θ) = ˆB dl cos(νm θ + φ) n= δ(θ 2πn) ˆB dl cos(2πnνm + φ) is the spin kick in turn n intrinsic resonance strength given by amplitude of Fourier integral over driving fields along orbit: ɛ = 1+G = 1+G 2πγ = 1+G 2 2πγ b(θ) 2πγ Bρ eikθ dθ ˆB dl Bρ ˆB dl Bρ [* S. Y. Lee, /PhysRevSTAB (2006)] n= cos(2πnν m + φ)e i2πkn ( e iφ n ei2π(k+νm)n + e iφ n ei2π(k νm)n) Beijing, October 21, 2014 s.mey@fz-juelich.de Spin Motion in an RF-Wien-Filter 9

10 Resonance Condition spin tune given by γg resonance at k =! γg = n ± ν m 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 Beijing, October 21, 2014 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 Beijing, October 21, 2014 Measurements 11

12 Field Compensation measurement on betatron frequency for max. sensitivity polarimeter target directly above beam-pipe-center * exited part of beam is removed diagnosis with COSY beam current transformer measurement gives minimal beam disturbance at Î = 1.76 ma/v Û Bx dz T mm [* E. Stephenson, contribution to SPIN2014] Phase 30% Output Amplitude, Natural Beamloss (38.2±1.1)% 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 Beijing, October 21, 2014 s.mey@fz-juelich.de Measurements 12

13 Vertical Beam Spectrum analogue signal from one vertical BPM pickup electrode 100 db spectra taken after beam prep. (black) and after RF-ExB is switched on (red) optimum matching results in narrow beam response very slight coherent beam oscillation not fully matched RF-ExB dipole results in more wideband beam response 130 db 100 db 130 db f = 10 khz f = 10 khz Beijing, October 21, 2014 s.mey@fz-juelich.de Measurements 13

14 2 Measurement of Resonance Strength Run3576 fpy: Hz, τ: s CR y 0.3 continuous polarimertry allows fixed frequency scan for resonance determination damping due to time-of-arrival ( p p ) and decoherence * cross-ratio of UD-asymmetries goes to zero ( average polarization) minimum vertical polarization oscillation frequency gives resonance strength ε = f Py min f rev χ / ndf / 95 cos Offset ± cos Phase ± 4.7 cos Freq / Hz ± exp scale 0.15 ± 0.01 exp τ / s ± t / s fpy = Hz at f RF = khz min fpy / Hz χ 2 / ndf / 3 Curvature Minimum at 1.73e+06 ± ± 9.91e e-06 Offset ± [* E. Stephenson, contribution to SPIN2014] Beijing, October 21, 2014 s.mey@fz-juelich.de Measurements f =(1-Gγ)f / khz RF rev

15 Preliminary result of Fixed Frequency Scans RF-solenoid: f Py 1+G 4π ˆB dl Bρ ; RF-Wien-Filter: f P y 1+G 4πγ 1+γG ˆB dl Bρ RF-dipole w.o. driven beam osc.: f Py 4π ˆB dl normalization has to be done to compare resonance strengths ˆB dl Bρ (2-Qy)frev / khz fpy / Hz preliminary data [M.A. Leonova et Al., contribution to Spin 2008, Charlottsville, VA)] Qy Beijing, October 21, 2014 s.mey@fz-juelich.de Measurements 15

16 Content The RF-ExB Dipole Spin Motion in an RF-Wien-Filter Measurements Conclusion Beijing, October 21, 2014 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) complicated and time-consuming matching of Wien-Filter condition routine operation of the prototype requires sophisticated phase and amplitude control system (feedback?) Beijing, October 21, 2014 s.mey@fz-juelich.de Conclusion 17

18 ToDo offline analysis of resonance scans incorporate LR-asymmetries, driven vertical oscillation appears in Fourier spectrum of idle horizontal spin precession statistically independent analysis ˆB dl determination from measurements resonance strength independence of betatron tune field calibration from fit of intrinsic resonance strength formula to scans at different amplitudes repeat measurements at +1 spin harmonic (629 khz) less damping of driven oscillation finally turn the RF-ExB dipole upright for systematics estimation in EDM mode Beijing, October 21, 2014 Conclusion 18

19 Content The RF-ExB Dipole Spin Motion in an RF-Wien-Filter Measurements Conclusion Beijing, October 21, 2014 Spares 19

20 Example measurement to determine B dl varying phase between the RF-ExB dipole and the RF-Solenoid to compensate both spin kicks at minimum vary RF-Solenoid amplitude to set the sum resonance strength to 0 f(py) / Hz both systems have exactly RF-Sol the@ same 1.5 resonance Vpp strength 1,6 1,4 1,2 1 0,8 0,6 0,4 0, f / Hz Input φ / Δf/2 / Hz [measurement idea by A. Saleev] Beijing, October 21, 2014 s.mey@fz-juelich.de Spares 20

21 RF-Solenoid and RF-Wien-Filter on Resonance RF-Wien-Filter at 0.01 T mm Beijing, October 21, 2014 RF-Solenoid at T mm s.mey@fz-juelich.de Spares 21