Y. Nagata

A source of antihydrogen for in-flight hyperfine spectroscopy

Antihydrogen, a positron bound to an antiproton, is the simplest antiatom. Its counterpart—hydrogen—is one of the most precisely investigated and best understood systems in physics research. High-resolution comparisons of both systems provide sensitive tests of CPT symmetry, which is the most fundamental symmetry in the Standard Model of elementary particle physics. Any measured difference would point to CPT violation and thus to new physics. Here we report the development of an antihydrogen source using a cusp trap for in-flight spectroscopy. A total of 80 antihydrogen atoms are unambiguously detected 2.7 m downstream of the production region, where perturbing residual magnetic fields are small. This is a major step towards precision spectroscopy of the ground-state hyperfine splitting of antihydrogen using Rabi-like beam spectroscopy.

A novel property of anti-Helmholz coils for in-coil syntheses of antihydrogen atoms: formation of a focused spin-polarized beam

We demonstrate here that cold antihydrogen beams formed and extracted from a cusp magnet (anti-Helmholtz coils) are well focused and spin-polarized. A new discovery was the fact that the antihydrogen beam follows the well-known lens formula of optical lenses with its focal length properly scaled with the initial kinetic energy, the magnetic field strength and the magnetic moment. Furthermore, the simulation revealed that for a certain kinetic energy region of antihydrogen atoms, the optimum production position is upstream of the center of the cusp magnet, where a well-known nested potential configuration can be applied.

Production of ultra‐slow antiproton beams

We have recently succeeded in decelerating and confining millions of antiprotons, 50 times more efficiently than conventional methods, in an electromagnetic trap. These antiprotons were cooled by preloaded electron plasma to an energy below an electronvolt. They were then extracted out of the magnetic field of 2.5 T and transported typically at 250 eV along a beamline, designed for efficient transport at 10–1000 eV. This unique beam from our apparatus named MUSASHI opens up a new field of atomic and nuclear physics probed by ultra‐slow antiprotons.In this paper, the whole experimental setup and procedure will be overviewed: deceleration, capture, cooling and extraction of antiprotons will be discussed in detail, including technical description of diagnostic devices.

The ASACUSA Micromegas Tracker: A cylindrical, bulk Micromegas detector for antimatter research

The ASACUSA Micromegas Tracker (AMT; ASACUSA: Atomic Spectroscopy and Collisions Using Slow Antiprotons) was designed to be able to reconstruct antiproton-nucleon annihilation vertices in three dimensions. The goal of this device is to study antihydrogen formation processes in the ASACUSA cusp trap, which was designed to synthesise a spin-polarised antihydrogen beam for precise tests of Charge, Parity, and Time (CPT) symmetry invariance. This paper discusses the structure and technical details of an AMT detector built into such an environment, its data acquisition system and the first performance with cosmic rays.

ASACUSA Gas-Jet Target: Present Status And Future Development

A supersonic gas‐jet target apparatus that have been prepared to study elementary processes of antiprotonic atoms formation using monoenergetic ultra‐slow antiproton beams is described. We investigated an operation of this target with cryogenically cooled nozzle by both gas dynamic simulations and supersonic jet measurements. In result, the helium target density of 2⋅1012 atoms/cm3 has been obtained.For considerable increasing of the target density, a qualitative modification of the present target setup is suggested. The goal can be achieved by the use of pulsed high‐pressure supersonic gas jet that operates in accordance with the pulsed mode of the MUSASHI penning trap. For this purpose an additional stage of differential pumping with a skimmer will be set into the present target setup. To avoid the clusters in the gas‐jet target, a sonic nozzle equipped with a solenoid driven pulsed gas valve will be used at room or higher temperatures. The operation of this future version of the gas‐jet target apparatu...

Control of plasmas for production of ultraslow antiproton beams

To produce ultraslow antiproton beams, decelerated antiprotons were captured in an electro‐magnetic trap and cooled by collisions with preloaded electrons. This electron cooling feature was nondestructively monitored by measurement of electrostatic oscillations of the confined electron plasma. The radial distribution of the plasma was controlled for efficient cooling and extraction by utilizing rotating wall field technique.

Towards measuring the ground state hyperfine splitting of antihydrogen – a progress report

We report the successful commissioning and testing of a dedicated field-ioniser chamber for measuring principal quantum number distributions in antihydrogen as part of the ASACUSA hyperfine spectroscopy apparatus. The new chamber is combined with a beam normalisation detector that consists of plastic scintillators and a retractable passivated implanted planar silicon (PIPS) detector.

The development of the superconducting double cusp magnet for intense antihydrogen beams

We have developed a superconducing double cusp magnet for the production of polarized intense antihydrogen atomic beams which are used to make microwave spectroscopy of a ground state hyperfine transition to test the CPT symmetry. The detail of specification and the focusing performance of the magnet will be presented.

The development of the antihydrogen beam detector and the detection of the antihydrogen atoms for in-flight hyperfine spectroscopy

We have been developing ground-state antihydrogen atomic beams to test CPT symmetry via in-flight hyperfine spectroscopy. A new antihydrogen beam detector has been developed. The overview of the experiment, the detail of the detector and latest results will be presented.

Positron accumulation and manipulation for antihydrogen synthesis

Our group ASACUSA-MUSASHI has established an efficient way for accumulating antiprotons in the cusp trap, a combination of an anti-Helmholz superconducting coil and a multi-ring electrode trap. The last piece for synthesizing antihydrogens in the cusp trap is positron. We have developed a compact system to effectively accumulate positrons based on N2 gas-buffer scheme with a specially designed high precision cylindrical multi-ring electrode trap. Millions of positrons were accumulated in the pre-accumulator just using polycrystalline tungsten moderators. The accumulated positrons were transported as a pulsed beam via three guiding coils and caught in the cusp trap under cryogenic and ultra high vacuum conditions without serious loss. Confinement of two kinds of numerous antiparticles, e.g., 108 positrons and 107 antiprotons, in the cusp trap becomes feasible.