The TRAP experiment, also known as PS196, operated at the Proton Synchrotron facility of the Low Energy Antiproton Ring (LEAR) at CERN, Geneva, from 1985 to 1996. Its main goal was to compare the mass of an antiproton and a proton by trapping these particles in the penning traps. [1] The TRAP collaboration also measured and compared the charge-to-mass ratios of antiproton and proton. [2] Although the data-taking period ended in 1996, the analysis of datasets continued until 2006. [3] [4]
| Low Energy Antiproton Ring (1982–1996) | |
|---|---|
| Antiproton Accumulator | Antiproton production |
| Antiproton Collector | Decelerated and stored antiprotons |
| Antimatter Factory (2000–present) | |
| Antiproton Decelerator (AD) | Decelerates antiprotons |
| Extra Low Energy Antiproton ring (ELENA) | Decelerates antiprotons received from AD |
In the first step, the antiprotons obtained from the LEAR entered the TRAP apparatus. They were immediately slowed down using the degrader foils. The first penning trap was used to the accumulate the entering antiprotons. While the second trap, located very close to the first one was used for the precision measurements. The number of antiprotons entering the degrader foils were counted using a scintillating device. A number of antiprotons coming out from the degrader foils were observed using an attached detector. The apparatus was cooled down to the liquid helium temperature for these measurements. [4] [5] [6]
The penning traps used strong magnetic fields to contain charged particles. The issue with storing antiprotons was that they required very stringent vacuum conditions, otherwise they would easily interact with the gas atoms in the medium and annihilate quickly. The TRAP collaboration achieved vacuum pressure as low as , with less than 1 annihilation per day. [4] The special type of trap-geometry and use of superconducting solenoid that would cancel the magnetic fluctuations were the crucial design aspects of the TRAP setup. [7] [8]
The ratio of inertial masses of antiproton () and proton (p) was calculated to be 0.999,999,977 0.000000042. This result had a fractional uncertainty of , which was 1000 thousand times more accurate than the previous measurements, that evidently implied the existence of CPT symmetry for the baryons. This result was obtained by comparing the cyclotron frequencies of the protons and the antiprotons. [5]
The ratio of antiproton to electron inertial mass was determined to be 1836.152660 0.000083, while the proton to electron inertial mass ratio was found to be 1836.152680 0.000088. [5]
The lower limit on the decay lifetime of the antiprotons was established to be 3.4 months. [1]
In modern physics, antimatter is defined as matter composed of the antiparticles of the corresponding particles in "ordinary" matter. Minuscule numbers of antiparticles are generated daily at particle accelerators—total artificial production has been only a few nanograms—and in natural processes like cosmic ray collisions and some types of radioactive decay, but only a tiny fraction of these have successfully been bound together in experiments to form antiatoms. No macroscopic amount of antimatter has ever been assembled due to the extreme cost and difficulty of production and handling.
A proton is a stable subatomic particle, symbol
p
, H+, or 1H+ with a positive electric charge of +1e elementary charge. Its mass is slightly less than that of a neutron and the proton-to-electron mass ratio makes it 1836 times the mass of an electron. Protons and neutrons, each with masses of approximately one atomic mass unit, are jointly referred to as "nucleons" (particles present in atomic nuclei).
The antiproton,
p
, is the antiparticle of the proton. Antiprotons are stable, but they are typically short-lived, since any collision with a proton will cause both particles to be annihilated in a burst of energy.
A Penning trap is a device for the storage of charged particles using a homogeneous axial magnetic field and an inhomogeneous quadrupole electric field. This kind of trap is particularly well suited to precision measurements of properties of ions and stable subatomic particles, like for example mass, fission yields and isomeric yield ratios. Another example are geonium atoms, which have been created and studied this way, to measure the electron magnetic moment. Recently these traps have been used in the physical realization of quantum computation and quantum information processing by trapping qubits. Penning traps are used in many laboratories worldwide, including CERN, to store antimatter such as antiprotons.
The Underground Area 2 (UA2) experiment was a high-energy physics experiment at the Proton-Antiproton Collider — a modification of the Super Proton Synchrotron (SPS) — at CERN. The experiment ran from 1981 until 1990, and its main objective was to discover the W and Z bosons. UA2, together with the UA1 experiment, succeeded in discovering these particles in 1983, leading to the 1984 Nobel Prize in Physics being awarded to Carlo Rubbia and Simon van der Meer. The UA2 experiment also observed the first evidence for jet production in hadron collisions in 1981, and was involved in the searches of the top quark and of supersymmetric particles. Pierre Darriulat was the spokesperson of UA2 from 1981 to 1986, followed by Luigi Di Lella from 1986 to 1990.
The Antihydrogen Trap (ATRAP) collaboration at the Antiproton Decelerator facility at CERN, Geneva, is responsible for the AD-2 experiment. It is a continuation of the TRAP collaboration, which started taking data for the PS196 experiment in 1985. The TRAP experiment (PS196) pioneered cold antiprotons, cold positrons, and first made the ingredients of cold antihydrogen to interact. Later ATRAP members pioneered accurate hydrogen spectroscopy and observed the first hot antihydrogen atoms.
Antiprotonic helium is a three-body atom composed of an antiproton and an electron orbiting around a helium nucleus. It is thus made partly of matter, and partly of antimatter. The atom is electrically neutral, since both electrons and antiprotons each have a charge of −1, whereas helium nuclei have a charge of +2. It has the longest lifetime of any experimentally producible matter-antimatter bound state.
The Proton Synchrotron is a particle accelerator at CERN. It is CERN's first synchrotron, beginning its operation in 1959. For a brief period the PS was the world's highest energy particle accelerator. It has since served as a pre-accelerator for the Intersecting Storage Rings (ISR) and the Super Proton Synchrotron (SPS), and is currently part of the Large Hadron Collider (LHC) accelerator complex. In addition to protons, PS has accelerated alpha particles, oxygen and sulfur nuclei, electrons, positrons, and antiprotons.
Gerald Gabrielse is an American physicist. He is the Board of Trustees Professor of Physics and Director of the Center for Fundamental Physics at Northwestern University, and Emeritus George Vasmer Leverett Professor of Physics at Harvard University. He is primarily known for his experiments trapping and investigating antimatter, measuring the electron g-factor, and measuring the electron electric dipole moment. He has been described as "a leader in super-precise measurements of fundamental particles and the study of anti-matter."
The Antiproton Decelerator (AD) is a storage ring at the CERN laboratory near Geneva. It was built from the Antiproton Collector (AC) to be a successor to the Low Energy Antiproton Ring (LEAR) and started operation in the year 2000. Antiprotons are created by impinging a proton beam from the Proton Synchrotron on a metal target. The AD decelerates the resultant antiprotons to an energy of 5.3 MeV, which are then ejected to one of several connected experiments.
The electron mass is the mass of a stationary electron, also known as the invariant mass of the electron. It is one of the fundamental constants of physics. It has a value of about 9.109×10−31 kilograms or about 5.486×10−4 daltons, which has an energy-equivalent of about 8.187×10−14 joules or about 0.511 MeV.
Alan Astbury (1934–2014) was a Canadian physicist, emeritus professor at the University of Victoria, and director of the Tri-Universities Meson Facility (TRIUMF) laboratory.
High-precision experiments could reveal small previously unseen differences between the behavior of matter and antimatter. This prospect is appealing to physicists because it may show that nature is not Lorentz symmetric.
Tests of relativistic energy and momentum are aimed at measuring the relativistic expressions for energy, momentum, and mass. According to special relativity, the properties of particles moving approximately at the speed of light significantly deviate from the predictions of Newtonian mechanics. For instance, the speed of light cannot be reached by massive particles.
The Antiproton Accumulator (AA) was an infrastructure connected to the Proton–Antiproton Collider – a modification of the Super Proton Synchrotron (SPS) – at CERN. The AA was built in 1979 and 1980, for the production and accumulation of antiprotons. In the SppS the antiprotons were made to collide with protons, achieving collisions at a center of mass energy of app. 540 GeV. Several experiments recorded data from the collisions, most notably the UA1 and UA2 experiment, where the W and Z bosons were discovered in 1983.
BASE, AD-8, is a multinational collaboration at the Antiproton Decelerator facility at CERN, Geneva. The goal of the Japanese and German BASE collaboration are high-precision investigations of the fundamental properties of the antiproton, namely the charge-to-mass ratio and the magnetic moment.
The Super Proton–Antiproton Synchrotron was a particle accelerator that operated at CERN from 1981 to 1991. To operate as a proton-antiproton collider the Super Proton Synchrotron (SPS) underwent substantial modifications, altering it from a one beam synchrotron to a two-beam collider. The main experiments at the accelerator were UA1 and UA2, where the W and Z boson were discovered in 1983. Carlo Rubbia and Simon van der Meer received the 1984 Nobel Prize in Physics for their decisive contribution to the SppS-project, which led to the discovery of the W and Z bosons. Other experiments conducted at the SppS were UA4, UA5 and UA8.
UA4 experiment (COULOMB) was a high-energy physics experiment at the Proton-Antiproton Collider at CERN. The UA4 collaboration consisted of physicists from Amsterdam, Genova, Napoli, Pisa, Roma, California and CERN. UA4 was approved on 18 January 1979, and the first phase of data taking lasted until 17 June 1985. The spokesperson of UA4 was Giorgi Matthiae.
John Holmes Malmberg was an American plasma physicist and a professor at the University of California, San Diego. He was known for making the first experimental measurements of Landau damping of plasma waves in 1964, as well as for his research on non-neutral plasmas and the development of the Penning–Malmberg trap.
Stefan Ulmer is a particle physicist and chief scientist at the Ulmer Fundamental Symmetries Laboratory, RIKEN, Tokyo. He is the founder and the spokesperson of the BASE experiment (AD-8) at the Antiproton Decelerator facility at CERN, Geneva. Stefan Ulmer is well known for his contributions to improving Penning trap techniques and precision measurements on antimatter. He is the first person to observe the single spin transitions with a single trapped antiproton, a significant achievement towards the antiproton magnetic moment measurements.
