Progress Towards an (Anti)Proton g - Factor Measurement

Transcription

1 Progress Towards an (Anti)Proton g - Factor Measurement Stefan Ulmer K. Blaum, H. Kracke, A. Mooser, W. Quint, C.C. Rodegheri und J. Walz Introduction Experimental techniques Measuring process Status and outlook e µ = g S m p

2 Motivation: Test of CPT-Symmetry CPT TESTS: 1 E E E E E e e : g- + - µ µ : g- LEPTONS + - e e : charge e+e- : mass MESONS K0 K0 pp: q/m BARYONS pp: q and m pp: g H-Atom: 1ss ATOMS 1 E E - 0 H-Atom: HFS - MASER 1 E E E -5 1 Relative Precision No figure of merit for CPT violation observe simple systems with high precision! This experiment aims at a relative precision of 10-9

3 Main-Tool: The Penning Trap modified cyclotron motion radial confinement B = Bez ω ω+ = c+ axial confinement ω ωc z magnetron motion r Φ (r, z ) = U 0 c z + ω ω ω ω = c c z axial motion ωz= B Ucorr U0 Ucorr q cu 0 mp B = 1.89 T This experiment: - Cylindrical Penning trap stack ν + 9 MHz ν z 690 khz ν 8.5 khz

4 Measuring Principle determination of the g-factor measurement of two frequencies of the proton in the trap: cyclotron frequency Larmor frequency ωl= g ω e B m p ωc= ωl νl g= = ωc νc L Excitation of the particle with a radio frequency field at ωl detection of the spin direction (continuous Stern-Gerlach effect) ω ' z ( ) ω ' z ( ) = δ ω!!! CRITICAL!!! z Non-destructive measurement of frequencies e B mp B e m Brown-Gabrielse invariance theorem ωc= ω+ +ω +ω z Measurement of image-current technique eigenfrequencies

5 Feedback Free Single Particle Frequency Measurement - Cryogenic detection systems detection circuit - Ultra low noise amplifiers - Superconducting tank circuits amplifier Ctrap Rp Cp Lres typical values U ind = IR p = IQω r L B I 1 fa R p 30 MΩ U ind 300 nv Penning trap 9,5 T = 4K Q = 5600 /(4000) L = 1.45 mh R p = 35 MΩ ν = 690 khz en = 1.3 nv Hz Work continued by ANDI MOOSER 9,0 8,5 Signal (a.u.) Axial Detector 8,0 7,5 7,0 6,5 6,0 5, Frequency (Hz) S. Ulmer et al.: Rev. Sci. Instrum. 80, 1330

6 Dip Detection detection circuit - Particle acts as a series LC circuit amplifier Ctrap Rp Cp Lres B Penning trap - Shorts detector noise - Resulting in a dip in the FFT spectrum of the detector N Rp q N ν = = π m D π τ Frequency measurement in thermal equilibrium with the detector 4K - small particle amplitudes - negligible energy dependence of frequency - measurement of the REAL magnetic moment

7 Larmor Frequency Measurement magnetic bottle leads to a coupling of m of a particle with its axial frequency ωz in a Penning trap ( Φ = µ B ) Φ mag z ρ = µ z B0 + B z axial frequency shift 1 µ z B ν z π mν z µ me = mp µ e p It s several times harder compared to e- B,sim = 300 kt/m νz,sim= 180 mhz

8 Phase Sensitive Detection Problem: - Frequency-shift of 00mHz requires for measuring time of at least 60s - Requires for voltage stability of 500nV/minute. PHASE SENSITIVE DETECTION METHOD Basic Idea: - Measure proton frequency relative to a phase locked sine. - Measure relative phase. Φ = (ν up ν 1 down ) T = 7 s T reduces measuring time by a factor of 60 to 100! Currently: 00mHz resolution in 1 second

9 Measuring Process Double Penning Trap electron gun analysis trap transport electrodes precision trap target 60 - Spin flip detection in the magnetic bottle field of the analysis trap 50 Spin Flip Probability (%) - High precision frequency measurement in the homogeneous precision trap 40 SIM 30 0 ULA 10 T IO N 0-0,1 5-0,1 0-0,0 5 0,0 0 0,0 5 0,1 0 0,1 5 Irradiated Larmorfrequency (Hz)

10 Status and Details

11 Experimental Setup Cryogenic operation SC-low noise detection long storage times (months) superconducting magnet cryo-cooler electronic flanges heat shields bellow adjustment table axial detector KEVLAR support trap can cyclotron detector conduction rods GFK - tube insulation vacuum rails 000 mm

12 Loading and Cleaning 1.) Load particles with EBIS.) Clean trap from contaminants -84 after loading after SWIFT CLEANING: 1.) Tune Particles to notch-filter.) Axial SWIFT-signal Signal (dbm) N + 1 C PROTONS C + H PURE PROTON CLOUD Ring Voltage (V)

13 Single Particle Preparation 4 Line-width (Hz) - Cloud excitation - Lowering of trapping potentials - FWHM of particle dip indicates proton number 1 N Rp q N ν = = π m D π τ Number of Particles Cyclotron Signal of a Single Proton Axial Signal of a Single Proton FFT Signal (dbvpk) FFT Signal (dbvpk) Frequency (Hz) ,9465 8,9470 8,9475 8,9480 8,9485 Frequency (MHz) Currently achieved relative precision: 10-8

14 Challenge: The Analysis Trap Proton in a Bottle electron gun analysis trap transport electrodes precision trap target First success after one year of sweat and tears! - Diameter of trap tower reduces between precisionand analysis-trap. Resonances, redesign of transport tube. - First trap design not practical for experimental operation, new trap-design. - Small diameter of analysis trap potential very sensitive on patch effects special surface treatment. new trap design Cricia C. Rodhegeri - Due to coulomb coupling trap has to be optimized with single particle non-harmonic parametric resonance optimization.

15 First Charged Particle Stored in Such a Strong Magnetic Bottle Amplitude(-dBVpk) Frequency (Hz) Next Step Bottle characterization and systematic investigation

16 Measurement of the Magnetic Bottle Application of cyclotron excitation to particle stored in magnetic bottle 1 ν z = 4π m pν z B E+ B Axial Frequency (Hz) Measure modified cyclotron frequency for different particle positions ,80 17,8 17,84 17,86 17,88 17,90 17,9 Excitation Frequency (MHz) 1,174 Magnetic Field (T) 1,173 1,17 1,171 1,170 1,169 1,168 B = 385 (5) kt/m 1, Axial frequency jump due to spin flip: 50 mhz Axial frequency as function of the radial energy: 1Hz/µeV Bottle well suited for systematic studies Position (µ m)

17 Temperature Measurements ν z ( Er ) = 1 E der exp r ν z + 4π mν kt - Vary feedback amplitude - Magnetron side band coupling to resonator - Detect axial frequency Measure convolution of Boltzmann distribution and drifts 0,50 T3 < T < T1 Fraction of Total Counts 0,45 0,40 0,35 0,30 0,5 0,0 0,15 0,10 0,05 0, Axial Frequency Deviation (Hz) z B Er B0 10 Minimum axial feedback temperature: 1.9K Cyclotron temperature can be measured in a very similar way. Variation between 6 K and K possible. See also N. Guise, G. Gabrielse PRL 010 (in press)

18 Problems: Axial Frequency Stability First measurements: Peak-to-peak long-term stability (h): 100 Hz Short-term stability (RMS 30s): 4 Hz 6 weeks optimization: Trap-tuning particle cooling ground loops 8th order filtering temperature stabilization Axial Frequency (Hz) Time (h) Peak-to-peak long-term stability (h): 10 Hz Short-term stability (RMS 30s): 350 mhz 700 mhz Sorting frequencies in low rms-jitter areas we can observe proton cyclotron frequency jumps Axial Frequency (Hz) , , , , , , Time (min)

19 Cyclotron Quantum Jumps ν z = 1 4π m pν z B E+ B0 n8 = n7+1 n+ = 85 mhz Axial Frequency (Hz) ,0 n7 = n6+1 E+ = 75 nev n6 = n5+1 n5 = n4+1 n4 = n3+1 n3 = n+1 n = n ,5 n1 = n0+1 n0 Cyclotron Energy Ladder (B=385 kt/m ) Number (#)

20 Conclusion and outlook Present measurement of the free cyclotron frequency of a single isolated proton with a relative precision detection of proton signals in magnetic bottle of 385 kt/mm². phase-sensitive detection established. Observed cyclotron quantum jumps Future improve axial frequency stability observation of spin-flips g-factor measurement.

21 Thanks to: AG-Walz at the institute of physics - Mainz Abteilung für gespeicherte und gekühlte Ionen at MPI-K GSI-Darmstadt VH-NG-037 Thanks for your attention!

22 The (Anti)Proton g Factor Team Andreas Mooser Holger Kracke Cricia Rodhegeri Stefan Ulmer

23 Spare Slides

24 Phase Sensitive Detection (Simulated in PT) Frequency Standard SR-٧٨٠ - FFT Analyzer Timing Unit FFT Trigger Free Particle Evolution Splitter Frequency Mixer Switch Particle Excitation Frequency Mixer Phase Shifter Switch Switch Trigger ٠ ٢٠٠ ٤٠٠ ٣٠٠K Amplifier ٦٠٠ ٨٠٠ ١٠٠٠ Trap Time (ms) Rp Cp Attenuator L Splitter Detection LC Cryogenic Amplifier Definite spin flip resolution in 1 s For maximum phase resolution (15 rms) optimize - Excitation time and amplitude - Active feedback damping "Spin up" "Spin down" ٤ Counts (#) - Trap compensation ٥ ٣ ٢ ١ - Measuring time ٠-١٦٠ -١٢٠-٨٠ -٤٠ ٠ ٤٠ ٨٠ Relative Phase ( ) ١٢٠ ١٦٠

25 Future Prospects improvement of detection systems Idea: toroidal coil based independent superconducting detectors for every trap. Higher inductances, higher RP, faster measuring cycles T = 4K P = 5.5 mw en = 0.9 nv in < 5 fa Qloaded = ν z = 600 khz L =.5 mh R p = 130MΩ Hz SNR > 5dB Hz ν z = 600 khz Current status: Detector improvement by a factor of 4 Andreas Mooser s workout

26 Frequency Measurement via Sideband Coupling - Irradiate coupling field: E p = E0 exp(iω k t )( xez + zex ) ENERGY EXCHANGE Ω Ω t Ω t z (t ) = k R0 sin k + Z 0 cos k exp(iω z t ) Ω k FFT signal (dbv) - Resonant with sideband frequencies: Principle also suitable for mode cooling Frequency (Hz) δ δ νr=νz + Frequency (Hz) νl=νz Ωk Ωk δ = (ν z + ν ) ν k δ + = ν k (ν + ν z ) One double dip includes two unknown frequencies Coupling Frequency (Hz) TRIPLE DIP METHOD

27 Motivation and History O. Stern: Molecular hydrogen beam in a SternGerlach apparatus (1933) 10 1 mp =.5 mk mp =.785 mk F. Bloch: NMR method in water (1946). 0,1 Relative Precision I. Rabi: Molecular hydrogen beam in a Rabi apparatus (1939) Stern Gerlach mp =.79 mk 0,01 Rabi 1E-3 Jeffries - Collington 1E-4 1E-5 1E-6 Aim of this Experiment Ap p aratu s 1E-7 Winkler - Kleppner 1E-8 1E-9 W all Limitation 1E W. Jeffries: Combination of NMR and direct cyclotron measurement (1951). In the evaluation the magnetic field cancels mp =.7976 mk D. Kleppner: Measurement of the electron and proton magnetic moment ratio via frequency measurement in a hydrogen maser in magnetic field (197). mp = mk M ag n etic Field Bloch Year ωl= g e B m p g= ωl ωc Single particle in a cryogenic double Penning trap

28 Triple Dip Two Frequencies Simultaneously Signal (a.u.) Modulate coupling signal with FFT matched TTL Frequenz(Hz) toothed measurement of two eigenfrequencies

29 Tests of CPT symmetry Tests of particle/antiparticle symmetry (PDG) planned Prof. W. Oelert: No figure of merit for CPT violation observe simple systems with high precision! Prof. Th. Schäfer: What about comparison of proton antiproton magnetic moment? ro m E. Experiment aims at a relative precision of 10-9 Wi d m a n n 9

30 Feedback Cooling and Trap Control Detection method using feedback 1.) Increase of signal to noise by a factor of 30 to 50.) Tremendous decrease in measurement time 3.) Particle still cold 1.) Rabi Oscillations Efficient Cooling Complete mode energy can be cooled within 00 ms compared to 10 s with SWIFT-cooling technique

31 Comparison Axial Detector Harvard Frequenz (khz) Güte Induktivität (mh) RP (Ohm) , ,5 Bottle / Spinflip Harvard B0 (T) B (mt/mm²) D\nu_z (mhz) 5, Axial Detector Mainz Frequenz (khz) Güte Induktivität (mh) RP (Ohm) , Bottle / Spinflip Mainz B0 (T) B (mt/mm²) D\nu_z (mhz) 1,

32 Type II: Model for CPTV: standard model extention SME CPT & Lo re ntz v io la tio n Mo d i f i e d Di r a c e q. i n S ME Lo re ntz v io la tio n Spontaneous Lorentz symmetry breaking by (exotic) string vacua Note: there is a preferred frame, sidereal variation due to earth rotation may be detectable fro m E. Wi d m a n n 3 3

33 Instability of the axial motion Instability due to DC-voltage drifts Instability due to potential couplings sextupolar perturbation: Φ z + ω z TRAP ρ ρ + C3 z z = C z ρ z = K (C 3 / C ) z ρ + ω ρ ρ + ω 1 + f ( Az ) Γ (C 3 / C )ω ω ρ z ρ ρ = K (C 3 / C )[ z ρ ] cos( ω z t ) ρ = 0 Parametrically pumped radial oscillator ACTION TRANSFER Magnetic bottle coupling: ν z = 1 π mν z B E ρ = 1MHz / ev B0 AMPLITUDE REDUCTION BY ELECTRONIC FEEDBACK