ASACUSA experiment

It compares matter and antimatter using antihydrogen and antiprotonic helium and looks into matter-antimatter collisions.

[1][2][3] It also measures atomic and nuclear cross-sections of antiprotons on various targets at extremely low energies.

[4] In 2020 ASACUSA in collaboration with the Paul Scherrer Institut (PSI) reported spectral measurements of long lived pionic helium.

[5][6][7] In 2022 ASACUSA reported spectral measurements of antiprotonic helium suspended in gaseous and liquid (He-I and He-II) targets.

The narrowness and symmetry of the spectral lines for antiprotonic helium contrasts with other types of atoms suspended in He-I and He-II.

The mixing of antiprotons and positrons forms polarised and cold antihydrogen inside a double-Cusp trap.

[12][13] Anticipating completion of ELENA, with the aim of making spectral measurements of previously undetected atomic resonances in antiprotonic helium, a new 6 m electrostatic beamline was constructed to transport ps to a cryogenic target.

[13] Acrylic and lead fluoride Čerenkov detectors monitor the beamline for p annihilations.

The helium targets are contained in a 35 mm diameter vessel made of titanium (gaseous or supercritical phase with 70% He-I) or OFHC copper (He-I and He-II) mounted on a liquid helium constant-flow cryostat.

A configuration of manometers and temperature sensors provide data used to characterize the state of the helium in the chamber.

[8] Opposite this, a 28-mm diameter, 5-mm thick UV-grade sapphire window transmits laser light, antilinear to an incident particle beam.

[8] Two 35-mm diameter Brewster windows made of fused silica (SiO2) mounted on flanges on opposite sides of the chamber walls perpendicular to the beam axis transmit laser light.

Particles emerging from the cryostat, such as pions from p-p annihilations emit Čerenkov radiation in the detector which is detected by a photomultiplier.