BEAMLINE MAGNETS FOR ALPHA-G MARK JOHNSON Cockcroft Presentations (17-12-2015)

OUTLINE A Brief Introduction to ALPHA Summary of the ALPHA-II Beamline The ALPHA-G Beamline Proposed layout Modelling in OPERA 18 Particle Tracking Simulations Current and Future Challenges Cockcroft Presentations (17-12-2015)

THE ALPHA EXPERIMENT Based at CERN’s Antiproton Decelerator facility ALPHA-II aims to perform low-energy tests of CPT symmetry using stable trapped antihydrogen: Measurements of the H spectrum [1] Tests of charge neutrality [2] Antimatter gravitation experiments [3] ALPHA-G is a proposed extension to ALPHA-II for greatly improved gravitational experiments Current design aims for a precision ± 1% measurement of 𝑔 Cockcroft Presentations (17-12-2015)

TRAPPED ANTIHYDROGEN [4] Three Penning-Malmberg traps in series: Catching Trap for p capture Atom Trap for autoresonant mixing of charged plasmas Accumulator for e + Magnetic minimum superimposed over the central Atom Trap Annihilation vertex detector enclosing the Atom Trap Cockcroft Presentations (17-12-2015)

ALPHA @ CERN Cockcroft Presentations (17-12-2015)

THE ALPHA-II BEAMLINE 𝐵 Catching Trap CT T2 T3 Atom Trap AT T4 B Gauss s [cm] Upstream Downstream Catching Trap CT T2 T3 Atom Trap AT T4 Accumulator 𝐵 Cockcroft Presentations (17-12-2015)

THE ALPHA-G CONCEPT A highly simplified sketch of the proposed upstream beamline: Vertical Solenoid (2.6 m) ~ 4 m Catching Trap CT T2 T3 Atom Trap AT Interconnect Beamline Modules × 3 Cockcroft Presentations (17-12-2015)

AN UNCONVENTIONAL BEAMLINE The ALPHA-II ‘beamline’ has several unusual features: Low energy plasmas can be held in place by a static potential (temporarily) Techniques for the cooling and manipulation of p and e + Plasmas are confined radially using solenoids, not quadrupole magnets! Cyclotron motion causes radial expansion in low fields The proposed ALPHA-G beamline includes a sharp 90° bend into a new vertical trapping region Cockcroft Presentations (17-12-2015)

FULL BEAMLINE MODEL Small-bore solenoid: Stray field reduction without full FEA field analysis Beamline Modules × 3 Accumulator Cockcroft Presentations (17-12-2015)

THE INTERCONNECT SECTION Crossed Solenoids generate a dipole component - without obstructing the p or e + beamlines Steering coils allow adjustment of transverse p trajectories Additional magnet pairs compensate for vertical solenoid fringe fields Cockcroft Presentations (17-12-2015)

FIELDS ALONG THE BEAMLINE Beamline Modules Interconnect External Solenoid Cockcroft Presentations (17-12-2015)

EARLY PARTICLE TRACKING Modelled the ALPHA-G beamline, in full, from the beamline modules onwards Used the OPERA 18 postprocessor for: An electromagnetic field solver (TOSCA 3D) A simple Lorentz solver Higher-order effects on the internal plasma structure are currently neglected Several thousand p can independently be propagated through the beamline forming a distribution in the vertical trap Cockcroft Presentations (17-12-2015)

EARLY PARTICLE TRACKING Initial Final Cockcroft Presentations (17-12-2015)

OFFSET CORRECTION Crossed Solenoids 𝐽 0 =650 A cm 2 Offset in 𝑥 ′ Cockcroft Presentations (17-12-2015)

PARTICLE TRACKING Final Initial Cockcroft Presentations (17-12-2015)

INTERCONNECT STEERING Before 𝑦 ′ offset correction Outline shows DNCF100 cross IR Cockcroft Presentations (17-12-2015)

INTERCONNECT STEERING After 𝑦 ′ offset correction Outline shows DNCF100 cross IR Cockcroft Presentations (17-12-2015)

FUTURE WORK Evidently, the magnets in the interconnect region need to be re-optimised to avoid beam losses The cause of the strange 𝑥 ′ offset within the vertical trap remains unknown Stray fields could nudge particles off-axis early in their trajectories Leads to runaway growth of transverse displacements Tracking of a more realistic plasma including higher-order collective effects Full characterization of stray field gradients within the vertical trap Cockcroft Presentations (17-12-2015)

THANKS FOR LISTENING! References: [1] Resonant Quantum Transitions In Trapped Antihydrogen Atoms C. Amole et al. (ALPHA Collaboration), Nature 483, 439 (2012) [2] An Experimental Limit On The Charge Of Antihydrogen C. Amole et al. (ALPHA Collaboration), Nature Communications 5, 3955 (2014) [3] Description And First Application Of A New Technique To Measure The Gravitational Mass Of Antihydrogen C. Amole et al. (ALPHA Collaboration), Nature Communications 4, 1785 (2013)