22-27 September 2019
Hyatt Regency Hotel Vancouver
Canada/Pacific timezone

Mon-Af-Or5-03: The ALPHA-g apparatus - A precision magnet system for antimatter gravity measurement

23 Sep 2019, 17:00
Regency CD

Regency CD

Contributed Oral Presentation Mon-Af-Or5 - Detector Magnets I


Chukman So (TRIUMF (CA))


The ALPHA-g experiment at CERN aims to be the first-ever to precisely weigh antimatter under Earth’s gravity, by “dropping” antihydrogen atoms with a magnet system. The anti-atoms are initially confined inside a vertical octupole and between two end cap coils. The currents in the coils are then gradually decreased to release the anti-atoms. The up -down balance of the escapes depends on gravity and the relative strength of the coils. By observing the escapes at different coil balances, the weight of antihydrogen is determined.
Achieving our first target of 1% precision in weight requires controlling the measurement field to an unprecedented 10 ppm precision. A sophisticated dual-cryostat magnet system is constructed for this purpose. An inner wet cryostat contains five octupoles, 22 coils and two solenoids (2 m overall height, 48 mm I.D.), and an outer dry cryostat contains a human-sized, shielded solenoid (2 m height, 600 mm I.D.). The centre of the system is used for gravity measurement, while other parts are used to confine, manipulate, transfer and cool the anti-atoms and their constituents. The octupoles and mirror coils are made to high precision at BNL by CNC wire-laying with active correction. The location, geometry and wire stock of each winding and its associated leads and splices are carefully designed using simulation to minimise field error. Wire placement inaccuracy and mechanical deformation of the windings are taken into account. Persistence effect is studied and mitigated by minimising the amount of superconductor, constructing an up-down symmetric magnet system, and using a special high-filament count NbTi cable. Higher-order corrector windings are constructed around the measurement region to provide additional field-shaping flexibility. A DCCT-based, bi-polar PID current control system is used to power the windings with < 10 ppm current precision. An environmental field-cancelling system is planned.

Primary authors

Mostafa Ahmadi (University of Liverpool (GB)) Bruno Ximenez Rodrigues Alves (Aarhus University (DK)) Christopher Baker (Swansea University (GB)) William Alan Bertsche (University of Manchester (GB)) Andrea Capra (TRIUMF (CA)) Celeste Carruth (University of California Berkeley (US)) Claudio Lenz Cesar (Federal University of of Rio de Janeiro (BR)) Mike Charlton (Swansea University (GB)) Snir Cohen (At.En. Comm., Nucl. Res. Cen. Negev (IL)) Robert Andrew Collister (TRIUMF (CA)) Stefan Eriksson (Swansea University (GB)) Andrew Evans (University of Calgary Dep. of Phys. and Astronomy (CA)) Nathan Andrew Evetts (TRIUMF (CA)) Joel Fajans (University of California Berkeley (US)) Tim Friesen (University of Calgary Dep. of Phys. and Astronomy (CA)) Makoto Fujiwara (TRIUMF (CA)) David Russell Gill (TRIUMF (CA)) Jeffrey Scott Hangst (Aarhus University (DK)) Walter Hardy (TRIUMF (CA)) Mike Hayden (Simon Fraser University (CA)) Eric David Hunter (University of California Berkeley (US)) Aled Isaac (Swansea University (GB)) Mark Andrew Johnson (University of Manchester (GB)) Jack Mccauley Jones (Swansea University (GB)) Steven Armstrong Jones (Aarhus University (DK)) Svante Jonsell (Stockholm University (SE)) Alexander Khramov (TRIUMF (CA)) Peter Knapp (Swansea University (GB)) Leonid Kurchaninov (TRIUMF (CA)) Niels Madsen (Swansea University (GB)) Daniel Thomas Maxwell (Swansea University (GB)) Joseph Mc Kenna (Aarhus University (DK)) Scott Menary (TRIUMF (CA)) Juan Mario Michan (TRIUMF (CA)) Takamasa Momose (University of British Columbia) Justine Joyce Munich (Simon Fraser University (CA)) Konstantin Olchanski (TRIUMF (CA)) Art Olin (TRIUMF (CA)) Petteri Pusa (University of Liverpool (GB)) Chris Rasmussen (CERN) Francis Robicheaux (Purdue University (US)) Rodrigo Lage Sacramento (Federal University of of Rio de Janeiro (BR)) Muhammed Sameed (University of Manchester (GB)) Elazar Sarid (Soreq Nucl. Research Center (IL)) Daniel De Miranda Silveira (TRIUMF (CA)) Darij Markian Starko (TRIUMF (CA)) Graham Stutter (Aarhus University (DK)) Chukman So (TRIUMF (CA)) Tim Tharp (Aarhus University (DK)) Robert Thompson (University of Calgary Dep. of Phys. and Astronomy (CA)) Prof. Dirk Peter Van Der Werf (Swansea University (GB)) Jonathan Syrkin Wurtele (University of California Berkeley (US))

Presentation Materials