Highlights from COSY (JEDI project) August 29, 2016 | Andreas Lehrach Forschungszentrum Jülich (IKP-4) & RWTH Aachen University (Ex.Physik IIIb) on behalf of the JEDI collaboration (Jülich Electric Dipole Moment Investigations)

Outline Introduction Motivation for EDM measurements Principle and methods Achievements Spin coherence time investigation Spin tune measurement Preparation for spin tune feedback Preparation for improved closed-orbit correction Technical developments RF Wien filter Electrostatic deflector Polarimetry Beam position monitor

Electric Dipole Moments Permanent EDMs violate parity P and time reversal symmetry T Assuming CPT to hold, combined symmetry CP violated as well. EDMs are candidates to solve mystery of matter-antimatter asymmetry

EDMs – Ongoing / planned Searches @CAPP/IBS P. Harris, K. Kirch … A huge worldwide effort

Limits for Electric Dipole Moments EDM searches - only upper limits up to now (in ecm): Particle/Atom Current EDM Limit Future Goal Neutron  3 10-26 10-28 199Hg  3.1 10-29 10-29 129Xe  6 10-27 10-30 – 10-33 Proton  7.9 10-25 Deuteron ? CP can have different sources It is important not only to measure neutron, but also proton, deuteron and light nuclei EDMs in order to disentangle various sources of CP violation Kern EDMs können viel größer sein(thoeretische Vorhersage) 5 5

Storage Ring EDM Project … measure for development of vertical polarization  EDM Challenges: Huge E-fields Shielding B-fields Spin coherence Beam position Polarimetry (...) JEDI Jülich Electric Dipole Moment Investigations ~ 136 members (11 countries and 37 institutes) http://collaborations.fz-juelich.de/ikp/jedi/

Spin Precession with EDM Equation for spin motion of relativistic particles in storage rings for . The spin precession relative to the momentum direction is given by: Thomas-BMT equation plus extension for EDM Magnetic Dipole Moment Electric Dipole Moment

Frozen-Spin Method for Storage Ring EDM Searches Approach: EDM search in time development of spin in a storage ring: B “Freeze“ horizontal spin precession; watch for development of a vertical component ! A magic storage ring for protons (electrostatic), deuterons, and helium-3 particle p (GeV/c) E (MV/m) B (T) proton 0.701 16.789 0.000 deuteron 1.000 -3.983 0.160 3He 1.285 17.158 -0.051 One machine with r ~ 30 m 8 8

Cooler Synchrotron COSY Dedicated EDM Storage Ring Stepwise Approach Measurements of charged particle EDMs from COSY to a dedicated EDM storage ring Cooler Synchrotron COSY Dedicated EDM Storage Ring R&D at COSY Precursor experiment for first direct measurement Injector for dedicated EDM ring CW-CCW beams Dedicated ring with high-precision beam diagnostics and polarimetry

Cooler Synchrotron COSY Experimental Setup for R&D at COSY polarimeter Inject and accelerate vertically polarized deuterons Spin rotated with RF fields into horizontal plane Move beam slowly (in 100 s) on internal target Measure asymmetry and determine spin precession precession At 970 MeV/c deuterons: γG ·frev ≈ 120 kHz turn spin RF ExB Wien filter Electron Cooler RF Solenoid Cooler Synchrotron COSY Polarized protons, deuterons 300/600 MeV/c - 3.7 GeV/c Precision Polarimeter Sextupole Magnets Polarized proton and deuteron source Ideal starting point to investigate EDM measurements in storage rings

Measurement of Spin Coherence Time 109 polarized deuterons at 970 MeV/c, bunched and electron cooled adjust three arc sextupoles to increase spin coherence time  Longest SCT for beam chromaticities close to zero at regular betatron tunes (Qx,y = 3.5 – 3.6)

Record In-Plane Polarization Lifetime Using a Gaussian width definition, the lifetime is 782 ±117 s. The exponential width 2280 ± 336 s. This is a new record for in-plane polarization lifetime, exceeding the Novosibirsk results for electrons by about three orders of magnitude. Phys. Rev. Lett. 117, 054801 (2016).

EDDA Detector to measure asymmetries Spin Tune Measurement at COSY EDDA Detector to measure asymmetries Sophisticated read-out system, which can time stamp individual event arrival times with respect to turn number: Map events into first spin oscillation period Analyse the spin phase advance throughout the cycle Phys. Rev. STAB 17 (2014)   Phys. Rev. Lett. 115 (2015)

Stability on a Turn-by-Turn Basis Study long term stability of an accelerator Develop feedback systems to minimize variations Phase-locking the spin precession to RF devices possible

In-plane polarization Resonance Method in Magnetic Rings RF ExB dipole in “Wien filter” mode  Avoids coherent betatron oscillations Modulation of horizontal spin precession in the RF Wien filter EDM’s interaction with the motional electric field in the rest of the ring continuous buildup of vertical polarization in a horizontally polarized beam. net effect due to EDM Investigation of sensitivity and systematic limitations In-plane polarization

Spin-tune Based Feedback System Left/right asymmetry as a measure of the vertical polarization. At t=85 s the spins are rotated into the horizontal plane, at t=115 s the solenoid is turned back on. The absolute values for the build-up for the two states are different as the initial polarization differs. Initial slope of the polarization build-up as function of the relative phase (online result). The difference in amplitude is due to the different degrees of polarization of the two initial states. Courtesy: V. Hejny

Systematic Limitations for EDM Measurements at COSY Absolute average change of the vertical spin component ΔSy per turn for different ΔyRMS and an initial Wien filter phase 0°. Utilized Wien filter magnetic field: 10-4 mT and corresponding electric field with a length of 0.8 m. Different ΔyRMS generated by randomized vertical quadrupole shifts assuming Gaussian distributed misalignment errors. Solid line shows the 90% upper confidence limit for pure misalignments. Dashed line refers to the location for which the false signal by misalignments is equal to an EDM signal corresponding to ηEDM = 10-4. This value corresponds to an EDM magnitude of dd ≈ 5∙10-19 e cm. Courtesy: M. Rosenthal

Preparation for Improved Closed-Orbit Correction Horizontal closed-orbit Random positioning and rotation errors of dipoles and quadrupoles Gaussian distributed. For each point 1000 seeds. Dashed line: measured “rms” orbit at COSY. p0: slop of linear fit. New survey of COSY has been provided and discussed. Alignment procedure will be performed soon. Upgrade of beam position monitor electronics also in preparation. (Alignment accuracy of 0.2 mm is possible). Courtesy: V. Schmidt

RF 𝑬×𝑩 Wien filter: Strip line design In cooperation with RWTH Aachen

Clamps for the Ferrit cage New RF Wien Filter   BPM (Rogowski coil) Copper electrodes Vacuum vessel with small angle rotator Clamps for the Ferrit cage   Ferrit cage Beam pipe (CF 100) Support structure for electrodes Inner support tube Support for geodetics RF feedthrough Ferrit cage Mechanical support   Magnetic fields were modelled with an accuracy of 10-6.  

Electrostatic Deflector Development Courtesy K. Grigoryev

Polarimeter Development The current engineering drawing (detector and the target chamber). From left to right there are two cross type flanges, one for beam position monitors (BPM's) and the second one for the target. In the middle there is a vacuum chamber. Next, the two layer of φ-sensitive plastic scintillator and the LYSO HCAL are placed to absorb the total energy of the scattered particles. LYSO calorimeter module in the carbon fiber enclosure. Courtesy: I Keshelashvilli

Quadrant signals of Rogowski coil sensitive to beam position. Challenge BPMs: Rogowski coil Integral signal measures beam current Quadrant signals sensitive to position EDM experiment needs bunched beams Rogowski coils well suited Small size allows flexible installation up     left right   down Quadrant signals of Rogowski coil sensitive to beam position.

Rogowski Type Beam Position Monitor Half and quarter winded Rogowski coils in the defined coordinate system. The shown configuration on the left enables a position measurement in x-direction. The configuration shown on the right corresponds to a measurement in both directions: x and y. Test of the linearity of the BPM response to the corrector magnet excitation, which is proportional to a horizontal beam displacement at the BPM. Courtesy: F. Hinder, F. Trinkel

Highlights Experimental Achievements at COSY Record In-Plane Polarization Lifetime Ultra-High Precision Spin Tune Measurement Spin-tune Based Feedback System Progress of Technical Developments Novel Waveguide RF Wien Filter Electrostatic Deflector Development Polarimeter Development Rogowski Type Beam Position Monitor Beam and Spin Dynamics Systematic Limitations for EDM Measurements at COSY Investigation of Lattices for a Deuteron EDM Ring

Conclusion Zusammenfassung Achievements: - Spin tune measurement with precision of 10-10 in a single cycle - Long spin coherence time of more than 1000s - Spin tracking codes developed and benchmarked - Investigation of systematic limit for resonance methods Goals: - Beam and spin dynamics studies at COSY - First direct EDM measurement at COSY - R&D work and design study for dedicated EDM storage ring 27

Source(s) for EDMs Multiple experimental input is required … … to disentangle the fundamental source(s) of EDMs

JEDI R&D Program (Jülich Electric Dipole Moment Investigations) 1. Studies of spin coherence time (SCT) Phase space cooling and adjusting sextupole settings at COSY to reach a SCT of 1000 s 2. Investigation of systematic effect Alignment of the ring magnets and closed-orbit correction Opening angle of spin ensemble 3. Development and benchmark precision simulation programs for spin dynamics in storage rings COSY-Infinity, integrating code and COSY experiments for bench marking 4. Development of high-efficiency polarimetry and high-precision BPMs 5. ExB Deflector development

Ultra-High Precision Spin Tune Measurement (a) Polarization phase, or direction, in the plane of the ring as a function of time during an experiment along with a quadratic polynomial fit. (b)The deviation of the spin tune from a reference value of 0.160 975 407 along with an error band based on the statistical precision shown in the upper panel. At about 38 s, the most precise spin tune value is (16 097 540 628.3 ± 9.7) ∙10-11. Courtesy: D. Eversmann

Design of a Novel Waveguide RF Wien Filter Magnetic fields were modelled with an accuracy of 10-6. Design model of the RF Wien filter showing the parallel-plates waveguide and the support structure. 1: BPM; 2: copper electrodes; 3: vacuum vessel; small angle rotor; 4: clamps to hold the ferrite cage; 5: belt drive for 90° rotation, with a precision of 0.01° (0.17 mrad); 6: ferrite cage; 7: CF100 feedthrough; 8: support structure of the electrodes; 9: inner support tube. Courtesy: A. Nass

History of Neutron EDM Limits Smith, Purcell, Ramsey PR 108, 120 (1957) RAL-Sussex-ILL (dn  2.9 10-26 ecm) PRL 97,131801 (2006) 50 years of effort Adopted from K. Kirch

Different shape of the electrodes Electrostatic deflectors: Some results Different shape of the electrodes Material : Stainless steel, Aluminum Mechanical polished and cleaned Stainless steel Two small half-spheres (R = 10mm) 17kV at 1mm distance → 17 MV/m Half-sphere vs. flat surface 12kV at 0.05 mm distance → 240 MV/m Aluminum 3kV at 0.1mm distance → 30 MV/m