Positron accumulation in the GBAR experiment Blumer, P.; Charlton, M.; Chung, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2022, Volume:
1040
Journal Article
Peer reviewed
Open access
We present a description of the GBAR positron (e+) trapping apparatus, which consists of a three stage Buffer Gas Trap (BGT) followed by a High Field Penning Trap (HFT), and discuss its performance. ...The overall goal of the GBAR experiment is to measure the acceleration of the neutral antihydrogen (H¯) atom in the terrestrial gravitational field by neutralising a positive antihydrogen ion (H¯+), which has been cooled to a low temperature, and observing the subsequent H¯ annihilation following free fall. To produce one H¯+ ion, about 1010 positrons, efficiently converted into positronium (Ps), together with about 107 antiprotons (p¯), are required. The positrons, produced from an electron linac-based system, are accumulated first in the BGT whereafter they are stacked in the ultra-high vacuum HFT, where we have been able to trap 1.4(2) × 109 positrons in 1100 s.
The GBAR (Gravitational Behavior of Antihydrogen at Rest) experiment at CERN requires efficient deceleration of 100 keV antiprotons provided by the new ELENA synchrotron ring to synthesize ...antihydrogen. This is accomplished using electrostatic deceleration optics and a drift tube that is designed to switch from -99 kV to ground when the antiproton bunch is inside – essentially a charged particle “elevator” – producing a 1 keV pulse. We describe the simulation, design, construction and successful testing of the decelerator device at -92 kV on-line with antiprotons from ELENA.
The GBAR project (Gravitational Behaviour of Anti hydrogen at Rest) at CERN, aims to measure the free fall acceleration of ultracold neutral anti hydrogen atoms in the terrestrial gravitational ...field. The experiment consists preparing anti hydrogen ions (one antiproton and two positrons) and sympathetically cooling them with B
e
+
ions to less than 10
μ
K. The ultracold ions will then be photo-ionized just above threshold, and the free fall time over a known distance measured. We will describe the project, the accuracy that can be reached by standard techniques, and discuss a possible improvement to reduce the vertical velocity spread.
The Einstein classical Weak Equivalence Principle states that the trajectory of a particle is independent of its composition and internal structure when it is only submitted to gravitational forces. ...This fundamental principle has never been directly tested with antimatter. However, theoretical models such as supergravity may contain components inducing repulsive gravity, thus violating this principle. The GBAR project (Gravitational Behaviour of Antihydrogen at Rest) proposes to measure the free fall acceleration of ultracold neutral antihydrogen atoms in the terrestrial gravitational field. The experiment consists in preparing antihydrogen ions (one antiproton and two positrons) and sympathetically cool them with Be
+
ions to a few 10
μ
K. The ultracold ions will then be photoionized just above threshold, and the free-fall time over a known distance measured. In this work, the GBAR project is described as well as possible improvements that use quantum reflection of antihydrogen on surfaces to use quantum methods of measurements.
We have studied the properties of a commercially available 4H-SiC epitaxial layer and evaluated its potential application as an efficient positron remoderator. A remoderation efficiency of more than ...65% has been measured for incident positrons with 1 keV energy. We have determined the work function and the energy distribution of the emitted slow positrons, a property which is essential for practical applications. Comparison of the positron moderation properties of the epitaxial layer with results from a n-type 4H-SiC single crystal, indicate that the epitaxially grown layer is a superior secondary moderator than its substrate counterpart.
After a long and fruitful R&D phase to validate its detector concept, the ANTARES collaboration will complete by 2008 the deployment of its 12-string underwater detector at a depth of 2500 m in the ...Mediterranean Sea, 40 km south-east of the French town of Toulon The 3D array of 900 photomultiplier tubes (PMT) will allow high energy neutrino astronomy with a pointing accuracy better than 1 degree. The detector size grew by steps from 1 line in March 2006, to 5 lines in January 2007, sketching a real 3D detector. Data recorded continuously provide a precise calibration of the charge and arrival time of Cerenkov photons coming from muon tracks. The position and orientation of individual detectors are measured frequently by compasses, tiltmeters and external acoustic triangulation. The data from the 3D detector allow the reconstruction of downward going cosmic ray muons and the search for the first upward going neutrino induced muons. Preliminary results of these analysis are presented.
A new slow positron beamline featuring a large acceptance positronium lifetime spectrometer has been constructed and tested at the linac-based slow positron source at IRFU CEA Saclay, France. The new ...instrument will be used in the development of a dense positronium target cloud for the GBAR experiment. The GBAR project aims at precise measurement of the gravitational acceleration of antihydrogen in the gravitational field of the Earth. Beyond application in fundamental science, the positron spectrometer will be used in materials research, for testing thin porous films and layers by means of positronium annihilation. The slow positron beamline is being used as a test bench to develop further instrumentation for positron annihilation spectroscopy (Ps time-of-flight, pulsed positron beam). The positron source is built on a low energy linear electron accelerator (linac). The 4.3 MeV electron energy used is well below the photoneutron threshold, making the source a genuine on-off device, without remaining radioactivity. The spectrometer features large BGO (Bismuth Germanate) scintillator detectors, with sufficiently large acceptance to detect all ortho-positronium annihilation lifetime components (annihilation in vacuum and in nanopores).
The specific antiproton- and positron-beam requirements of the CERN AD-7 experiment, GBAR (Gravitational Behavior of Antimatter at Rest) are presented. GBAR will synthesize antihydrogen
ions
which ...will be sympathetically cooled before performing a free-fall experiment on the atom. Antiprotons delivered by CERN’s ELENA facility in 100-keV, 300-ns pulses will be electrostatically decelerated and transformed to keV energies using a pulsed drift tube. Positrons are created using a linear electron accelerator and collected into a Penning-Malmberg trap. Descriptions of these ion optical systems are given along with the status.
The Gravitational Behaviour of Antihydrogen at Rest experiment - GBAR - is designed to perform a direct measurement of the weak equivalence principle on antimatter by measuring the acceleration ( ) ...of antihydrogen atoms in free fall. Its originality is to produce + ions and use sympathetic cooling to minimize the initial velocity. These ions are produced using charge exchange reactions with a dense positronium cloud, created by an intense pulse of electron-linac-produced positrons that are accumulated in a Penning-Malmberg trap.
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