Gaseous photon detectors
WP Leaders:
• Fulvio Tessarotto
• Shuddha Shankar Dasgupta
Contact: DRD1-WP6-leaders@cern.ch
Participating institutes:
Aristotle University of Thessaloniki (AUTh), Thessaloniki, Greece
University of Science and Technology of China (USTC), Hefei, China
National Institute of Science, Education and Research (NISER), Bhubaneshwar, India
European Organisation for Nuclear Research (CERN), Geneva, Switzerland
Weizmann Institute of Science (WIS), Rehovot, Israel
Università degli studi di Padova e Istituto Nazionale di Fisica Nucleare, Sezione di Padova (INFN-PD)
Istituto Nazionale di Fisica Nucleare, Sezione di Trieste (INFN-TS)
Helsinki Institute of Physics (HIP), Helsinki, Finland
Universidade de Aveiro (Aveiro), Aveiro, Portugal
Facility for Rare Isotope Beams (FRIB), Michigan State University, Michigan, USA
Technical University of Munich (TUM), Munich, Germany
DESCRIPTION OF THE WORK PACKAGE
Gaseous photon detectors (PDs) have played an essential role for RICH applications, and they represent a potentially key element for future detector applications in high-energy particle physics, hadron physics, nuclear physics, and other domains.
This technology can provide coverage of very large areas with photosensitive detectors at moderate cost, low material budget and magnetic insensitivity.
The main challenges are the development of detectors with more robust photoconverters, higher photon detector efficiency, sensitivity in a wider wavelength range, possibly including in the visible region, high granularity, very good time resolution and dedicated readout electronics for efficient detection of single photon signals.
Applications aiming for precision detection of Cherenkov photons, in different environments and with various purposes, face specific technological challenges, motivating this R&D Work Package. They are partly common for light detection applications in other research fields, and for medical or environmental purposes.
This project aims at:
• development of robust photoconverters operating in gas;
• optimization of photon detection efficiency;
• suppression of ion backflow (IBF) to the photocathode;
• development of photon detectors with MPGDs operating in special gaseous atmospheres (noble gases, CF4, H2, …);
• improvement of the gaseous photon detector performance in terms of space and time resolution, stability and rate capability;
• technological solutions for large area coverage;
• optimization of front-end electronics and DAQ systems.
Long term goals include the development of ion backflow free detectors, using specific architectures or innovative materials for ion blocking layers; this will allow extending the sensitivity of gaseous photon detectors to the visible range to produce Gas-avalanche photomultipliers (GPMs).
Applications of GPMs include a variety of particle physics and astrophysics experiments; imaging Cherenkov light and recording scintillation information; large-area photon detectors that could be useful in medical imaging and in many other fields.
Gaseous Detectors for UV photons:
Three generations of gaseous photon detectors have been developed and operated: the gaseous PDs with converting vapours included in the gas mixture, MWPC with solid state CsI-photocathodes, and MPGD-based PDs with CsI-photocathodes. This historical development matches the need to provide progressively better solutions to the challenging requirements in this field, namely: to reduce the photon feedback generated in the multiplication process which leads to spurious signals; to reduce the IBF rate because the ion bombardment destroys the photocathode and limits the lifetime of the detector (R&D line in common with TPC needs, DRDT 1.2); to improve the detector performance in term of spatial and time resolution, along with fast response in order to open the way to high-rate capabilities and precision measurements (DRDT 1.1).
The use of MPGD-based PDs is proposed for hadron identification at future colliders (the Super Tau-Charm Facility, for instance). To meet the requirements of these applications, improvements in various aspects of this technology are needed.
Gaseous photon detectors capable of long-time stable operation with minimal or no gas flow would find application in various fields.
Novel robust photoconverters with sensitivity in the VUV and DUV region are of great interest for applications in harsh environments, for H2 TPC optical readout and in general for detecting light from active target gases emitting in the VUV or DUV region.
Gaseous Detectors for visible photons:
The quest for gaseous detectors of visible photons has been present for a long time.
We plan to explore new solutions which are now available thanks to recent technological advancements.
Gas-avalanche photomultipliers (GPMs), capable of single-photon sensitivity, require operation at high multiplication gains with very low ion-back flow to limit ion-induced secondary effects. Photon detectors of this type have several attractive properties:
unlike vacuum PMTs, they can operate at atmospheric pressure, which makes it possible to design large-area detectors with flat geometry (up to a square meter); unlike vacuum detectors, GPMs can withstand high magnetic fields. GPMs are expected to have a slower response (in the ns range), compared to PMTs, but superior localization accuracy (down to 0.1 mm for single photons with standard gas-detector readout). It is possible to extend the implementation of large-area GPMs into the visible spectrum when they are coupled with the appropriate photocathode materials.
The development of GPMs requires a long-term, intense R&D effort to achieve a better understanding of the processes involved in avalanche-ion transport and how these processes affect the photocathodes and to discover an efficient passive avalanche-ion blocking method that will not affect photoelectron collection efficiency.
Relevance in context of ECFA Roadmap
· DRDT 1.1 - Improve time and spatial resolution for gaseous detectors with long-term stability.
· DRDT 1.2 - Achieve tracking in gaseous detectors with dE/dx and dN/dx capability in large volumes with very low material budget and different readout schemes.
· DRDT 1.3 - Develop environmentally friendly gaseous detectors for very large areas with high-rate capability.
TASKS AND DELIVERABLES
T1: New robust UV photoconverters for gaseous photon detectors
Study of the response of novel photoconverting materials. Demonstrate the performance of nanodiamond powder photocathodes in terms of their chemical reactivity and aging. Perform systematic measurements on small-scale gaseous PD prototypes. Define the optimal structure and working point. Produce a prototype using innovative, robust photoconverter. Provide a detailed characterization of QE of new photocathode materials.
T2: Increase photon detection efficiency
Detailed characterization of photoemission & stability vs applied fields of photocathodes on micro-structured surfaces. Optimization of photoemission in pure gases and mixtures.
T3: Suppression of ion feedback to the photocathode, increase of stability and longevity.
Detector studies to reduce intrinsic limiting factors such as space charge (rate capabilities), ion backflow (IBF) leading to the ageing of photocathodes, and discharge probabilities at nominal working conditions. Discharge protection with resistive multipliers (RWELL, RPWELL). Reduction of IBF to the photocathode by multi-mesh structures or other innovative architectures.
T4: Gaseous photon detectors sensitive to visible light
Study of photon detectors equipped with visible light sensitive photocathodes in innovative configurations. Prototyping visible-light sensitive gas detector with Triple MicroMegas (TMM). Preparation of a common facility for Gaseous Photomultipliers studies.
T5: Spatial resolution and readout granularity
Enhance spatial resolution of gaseous photon detectors by optimizing readout granularity and developing readout solutions which can improve spatial resolution by resistive and capacitive charge sharing for applications needing sub-millimeter resolution.
T6: Time resolution
Optimization of the photoconverter, the gas and detector architecture for gaseous photon detectors applications requiring time resolution of the order of few 100 ps or better. Develop specific photocathodes for fast timing tracking using PICOSEC technology.
T7: Modelling and simulation of gaseous photon detectors
Development of modelling tools and techniques to optimize photon detection performance including the simulation of photon conversion, charge transport and amplification, signal induction and the influence of resistive detector elements. Comparison of simulation results to laboratory measurements.
T8: Large area coverage
Identify needs, technological limits, and potential improvement for each proposed technology towards granting precise mechanics (mm) over relatively large active areas (hundreds of cm2). Develop technological solutions to minimize the material budget of precise timing detectors including mechanics, amplification structure optimization and choice of charge conversion elements. Prototype of 30x30 cm2 double Micromegas with reflective CsI photocathode for UV light detection.
T9: Readout electronics for single photon signals
Comparison of performance limits with different existing frontend electronics. Development of optimized interfacing between the gaseous photon detectors and the new frontend and DAQ. Development of a dedicated ASIC chip, sensitive to single photon signals
List of deliverables
- D1: Prototype of medium-size detectors of single photons, based on hybrid THGEM-Micromegas architecture, equipped with H-ND photocathode and fully characterized.
- D2: Report on simulation studies and measurement of IBF suppression techniques.
- D3: Prototype of MPGD-based PD with visible light sensitive photocathode.
- D4: Prototype of photon detector based on PICOSEC technology.
- D5: Report on aging studies of various UV and VIS photocathodes for gaseous photon detectors.
