The Alpha Magnetic Spectrometer (AMS) on the international space station: Part II — Results from the first seven years

The Alpha Magnetic Spectrometer (AMS) is a precision particle physics detector on the International Space Station (ISS) conducting a unique, long-duration mission of fundamental physics research in space. The physics objectives include the precise studies of the origin of dark matter, antimatter, and cosmic rays as well as the exploration of new phenomena. Following a 16-year period of construction and testing, and a precursor flight on the Space Shuttle, AMS was installed on the ISS on May 19, 2011. In this report we present results based on 120 billion charged cosmic ray events up to multi-TeV energies. This includes the fluxes of positrons, electrons, antiprotons, protons, and nuclei. These results provide unexpected information, which cannot be explained by the current theoretical models. The accuracy and characteristics of the data, simultaneously from many different types of cosmic rays, provide unique input to the understanding of origins, acceleration, and propagation of cosmic rays.</p

VACUUM SYSTEM OF HIRFL’S CYCLOTRONS

HIRFL has 2 cyclotrons: a sector focus cyclotron (SFC)<br />and a separate sector cyclotron (SSC). SFC was built in<br />1957. In the past 50 years, the vacuum system of SFC has<br />been upgraded for three times. The vacuum chamber was<br />redesigned to double-deck at the third upgrade. The<br />working pressure in beam chamber was improved from<br />10-6mbar to 10-8mbar. SFC has delivered Pb, Bi and U<br />beams in the past few years since the last upgrading of its<br />vacuum chamber. SSC began to operate in 1987. The<br />vacuum chamber of SSC has a volume of 100m3. 8<br />cryopumps keep the pressure from 5&times;10-7mbar to 8&times;10-<br />8mbar depending on the used pump numbers (2~8). In the<br />past 20 years, because of the contamination of oil vapour<br />and leaks occurred in some components inside the SSC<br />vacuum chamber, the vacuum condition has worsened<br />than the beginning. It is a big problem to accelerate the<br />heavier ions. The upgrade for the SSC vacuum system<br />will be an urgent task for us. The rough pumping systems<br />of both SFC and SSC have been rebuilt recently. As a<br />result, the oil vapour in two cyclotrons will be eliminated<br />and the vacuum condition of them will be improved.<br />A new small cyclotron will be built in HIRFL as an<br />injector of the Heavy Ion Therapy Facility in Lanzhou<br />(HITFiL). The brief introduction of the vacuum system<br />design is given in the paper