Presenter: Dr. Thomas PAPAEVANGELOU - EP / UGC
MicroMegas detector applications for beam diagnostics
Abstract:
Micromegas detectors are Micro-Pattern Gaseous Detector (MPGD), which have been used in many particle physics experiments since their invention in 1996. MPGDs provide high gain, fast signals, high rate capabilities, better aging properties, lower cost and simplified manufacturing processes compared to other gaseous detectors. Appropriately designed Micromegas detectors can be used for beam diagnostics.
Superconductive accelerators emit X-rays and photons mainly due to high electric fields applied on the superconductive cavity surfaces. Such photons may present a real problem for Beam Loss Monitors (BLM) since no discrimination can be made from cavity contributions and beam loss contributions. A new BLM is proposed based onMicromegas detectors, which is highly sensitive only to fast neutrons while being insensitive to X-rays and photons. It is using Polyethylene for neutron moderation and the detection is achieved using a converter with a micromegas gaseous amplification. For neutrons with energies between 1 eV and 10 MeV, detection efficiencies 5-8 % are achievable. This detector will soon be part of the BLM system for the European Spallation source (ESS).
The use of fast timing detectors (~10 ps) is crucial for the exploitation of the full potential of the future LHC operation at the highest luminosity. We demonstrate that a Micromegas based solution may reach this level of time resolution even at high particle fluxes and high radiation. The Micromegas acts as a photomultiplier coupled to a Cerenkov-radiator, to provide a timing resolution of about 10-20 ps per incident particle. A prototype has been built in order to demonstrate this performance. The first laboratory tests with a pico-second laser have shown a time resolution of 27 ps for ~40 photoelectrons, or ~180 ps per photoelectron. A medium scale prototype is in the R&D phase to demonstrate the performance of the proposed system in realistic conditions. In order to improve the aging properties of the photocathode, diamond based secondary emitters will be developed as an alternative to the radiator-photocathode setup, while the option of using photocathodes with a graphene protection layer will be also studied.
The presentation will be given in English.
