Development of a PbWO4 Detector for Single-Shot Positron Annihilation Lifetime Spectroscopy at the GBAR Experiment

We have developed a PbWO4 (PWO) detector with a large dynamic range to measure the intensity of a positron beam and the absolute density of the ortho-positronium (o-Ps) cloud it creates. A simulation study shows that a setup based on such detectors may be used to determine the angular distribution of the emission and reflection of o-Ps to reduce part of the uncertainties of the measurement. These will allow to improve the precision in the measurement of the cross-section for the (anti)hydrogen formation by (anti)proton-positronium charge exchange and to optimize the yield of antihydrogen ion which is an essential parameter in the GBAR experiment

EPICS Java Developments

International audienceThe IRFU*/DIS software control team is involved from feasibility studies to the deployment of equipment covering low level (hardware, PLC) to high level (GUI supervision). For our experiments, we are using two mains frameworks: - MUSCADE, a full Java in-house solution embedded SCADA dedicated to small and compact experiments controlled by PLC (Programmable Logic Controller), only compatible with Windows Operating System (OS) for the server side. - EPICS**, a distributed control systems to operate devices such as particle accelerators, large facilities and major telescopes, mostly deployed on Linux OS environments. EPICS frameworks provides several languages for bindings and server interfaces such as C/C++, Python and Java. However, most of the servers also called IOC*** developed in the community are based on C/C++ and Linux OS System. EPICS also provides extensions developed in Java such as the EPICS Archiver Appliance, Phoebus Control-Studio**** (GUI), and Display Web Runtime (Web Client). All these tools depend on CAJ (a pure Java implementation Channel Access Library). Today, MUSCADE users use to work under Windows, and they need intuitive tools that provide the same features than MUSCADE. Thus, research and development activities mainly focus on EPICS solution adaptation. It aims to explore further CAJ library, especially on the server side aspect. In order to achieve this goal, several developments have been carried out since 2018

EPICS Tools for Small Experiment Based on PLC

International audienceIRFU* software control team is involved from feasibility studies to equipment deployment into many different experiments by their size and running time. For many years, IRFU is using PLC solution for controlling part of the experiment, and two different SCADA: - MUSCADE, in-house SCADA dedicated to small experiments. - EPICS** for big facilities. With MUSCADE, IRFU has developed a set of tools that gives an easy and a fast way for PLC developers to configure the SCADA. As EPICS projects are growing in our department, we are working now on adapting those tools to EPICS: - PLCParser, which generates an EPICS database for PLC communication (S7PLC, Modbus). - CAFEJava (Channel Access For EPICS Java) API, which runs a simulated EPICS IOC to test EPICS synoptic, and provides EPICS process variables access for any Java application. - Dxf2Opi, which converts Autocad DXF files into OPI files for CSS*** software. - MOONARCH (Memory Optimizer ON ARCHiver Appliance), which reduces EPICS Archiver Appliance**** data files storage

vscode-epics, a VSCode Module to Enlighten Your EPICS Code

International audiencevscode-epics is a Visual Studio Code module developed by CEA Irfu that aims to enlight your EPICS code. This module makes developer life easier, improves code quality and helps standardizing EPICS code. It provides syntax highlighting, snippets and header template for EPICS file and provides snippets for WeTest*. This VSCode module is based on Visual Studio Code language Extension and it uses basic JSON files that make feature addition easy. The number of downloads increases version after version and the different feedback motivates us to strongly maintain it for the EPICS community. Since 2019, some laboratories of the EPICS community have participated in the improvement of the module and it seems to have a nice future (linter, snippet improvements, specific language support, etc.). The module is available on Visual Studio Code marketplace** and on EPICS extension GitHub***. CEA Irfu is open to bug notifications, enhancement suggestions and merge requests to continuously improve vscode-epics

Status of the GBAR control project at CERN

International audienceOne yet unanswered questions in physics today concerns the action of gravity upon antimatter. The GBAR experiment proposes to measure the free fall acceleration of neutral antihydrogen atoms. Installation of the project at CERN (ELENA) began in late 2016. This research project is facing new challenges and needs flexibility with hardware and software. EPICS modularity and distributed architecture has been tested for control system and for providing flexibility for future installation improvement. This paper describes the development of the software and the set of software tools that are being used on the project

Motorized Regulation Systems for the SARAF Project

International audienceCEA is in charge of the tuning regulation systems for the SARAF-Linac project. These tuning systems will be used with LLRF to regulate the 3 Rebuncher cavities and the HWR cavities of the 4 cryomodules. These systems were already tested on the Rebuncher and Equipped Cavity Test stands to test respectively the warm and cold tunings. This paper describes the hardware and software architectures. Both tuning systems are based on Siemens PLC and EPICS-PLC communication. Ambiant temperature technology is based on SIEMENS motor controller solution whereas the cold one combines Phytron and PhyMOTION solutions

Antarctic observations at long wavelengths with the IRAIT-ITM Telescope at Dome C

We illustrate the status of the international infra-red telescope IRAIT-ITM, a project developed thanks to an Italian- Spanish-French collaboration and now sited at the Dome C Antarctic base. The telescope and its subsystems were installed at DomeC by a team of Italian and French scientists. The 80 cm telescope is placed on a small snow hill next to a laboratory of astronomy. The operations started in January 2013, with the Nasmyth focal planes equipped with the midinfrared camera AMICA for 1.25 to 25 μm and the sub-millimetre camera CAMISTIC for observation of the sky noise at 200 and 350 μm using a bolometer camera. During 2013 the two winter-overs worked mainly on technological duties, learning how to operate the telescope, while temperatures decreased down to -80°C. The cryogenic systems could be operated respectively at 0.25K and 4K at all times, with satisfactory use of the heat from the compressors of the cryocoolers to the warm-up the laboratory through a closed loop glycol system. The lack of tests and reliability in extreme conditions of some components and difficult access to maintenance hampered regular observations below -50°C. Using the lessons of this first winter, the summer team improves the robustness of the failing systems and ease the access to maintenance. The winter 2014 is the first one with programmed observations. Because of power restrictions, the two instruments are used each one at a time by periods of 2 weeks. The Camistic camera continues to observe the stability of the sky at a fixed altitude in chopping mode and performs skydips. The TCS is being upgraded in order to prepare the next summer season with extensive observations of the sun with Camistic

A pulsed high-voltage decelerator system to deliver low-energy antiprotons

The GBAR (Gravitational Behaviour 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 ELENA

Positron production using a 9 MeV electron linac for the GBAR experiment

International audienceFor the GBAR (Gravitational Behaviour of Antihydrogen at Rest) experiment at CERN’s Antiproton Decelerator (AD) facility we have constructed a source of slow positrons, which uses a low-energy electron linear accelerator (linac). The driver linac produces electrons of 9 MeV kinetic energy that create positrons from bremsstrahlung-induced pair production. Staying below 10 MeV ensures no persistent radioactive activation in the target zone and that the radiation level outside the biological shield is safe for public access. An annealed tungsten-mesh assembly placed directly behind the target acts as a positron moderator. The system produces 5×107 slow positrons per second, a performance demonstrating that a low-energy electron linac is a superior choice over positron-emitting radioactive sources for high positron flux

Positron accumulation in the GBAR experiment

International audienceWe 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