Micro-pattern gas detectors (MPGD) could become suitable devices to carry out time-resolved X-ray diffraction experiments in the sub-millisecond time scale at synchrotron radiation facilities. Nevertheless, these devices are not free of problems. Among other problems are the build-up of ions in the detector components and the susceptibility of the materials in the structure to dielectric breakdown. Here, we present a new MPGD design we have called micro reading mesh chamber (MRMC). Its layout is based on a resistive anode, support pillars and a mesh formed by two planes of pick-up strips. In order to prevent charging up, a common problem with GEMs and MPGD in general, a minimum amount of dielectric material has been used in the design. The aim has been to avoid dielectric near the drift paths of the ions. To prevent dielectric breakdown, a resistive anode with guard rings at the base of the pillars has been designed. Finally, to improve the cathode signals quality, we use a mesh to read the avalanche. In this manner the size of the induced charge is larger than in more conventional geometries.

The design and technology of the silicon strip detector modules for the Semiconductor Tracker (SCT) of the ATLAS experiment have been finalised in the last several years. Integral to this process has been the measurement and verification of the tracking performance of the different module types in test beams at the CERN SPS and the KEK PS. Tests have been performed to explore the module performance under various operating conditions including detector bias voltage, magnetic field, incidence angle, and state of irradiation up to 3×1014 protons per square centimetre. A particular emphasis has been the understanding of the operational consequences of the binary readout scheme.

The ABCD3TA is a 128-channel ASIC with binary architecture for the readout of silicon strip particle detectors in the Semiconductor Tracker of the ATLAS experiment at the Large Hadron Collider (LHC). The chip comprises fast front-end and amplitude discriminator circuits using bipolar devices, a binary pipeline for first level trigger latency, a second level derandomising buffer and data compression circuitry based on CMOS devices. It has been designed and fabricated in a BiCMOS radiation resistant process. Extensive testing of the ABCD3TA chips assembled into detector modules show that the design meets the specifications and maintains the required performance after irradiation up to a total ionising dose of 10Mrad and a 1-MeV neutron equivalent fluence of 2×1014 n/cm2, corresponding to 10 years of operation of the LHC at its design luminosity. Wafer screening and quality assurance procedures have been developed and implemented in large volume production to ensure that the chips assembled into modules meet the rigorous acceptance criteria.

The very high radiation fluence expected at LHC (Large Hadron Collider) at CERN will induce serious changes in the electrical properties of the silicon detectors that will be used in the internal layers of the experiments (ATLAS, CMS, LHCb). To understand the influence of the fabrication technology in the radiation-induced degradation, silicon detectors were fabricated simultaneously with the three different possible technologies, P-in-N, N-in-N, and N-in-P, on standard and oxygenated float-zone silicon wafers. The diodes were irradiated with protons to fluences up to 10/sup 15/ cm/sup -2/. The measurements of the electrical characteristics, current-voltage and capacitance-voltage, are presented for the detectors manufactured with the three technologies. In terms of alpha factor (leakage current) the three technologies behave similarly. In terms of beta factor (effective doping concentration) N-in-P devices show the best performances.

SU-8 photosensitive epoxy resin was developed for the fabrication of high-aspect ratio microstructures in MEMS and microengineering applications, and has potential for use in the construction of novel gaseous micropattern radiation detectors. However, little is known of the behaviour of the cured material under irradiation. Mechanical properties of SU-8 film have been measured as a function of neutron exposure and compared with Kapton® polyimide and Mylar® PET polyester films, materials routinely used in gaseous radiation detectors, to asses the suitability of SU-8 based microstructures for gaseous detector applications. After exposure to a reactor core neutron fluence of 7.5×1018ncm−2, the new material showed a high level of resistance to radiation damage, comparable to Kapton film.

High oxygen concentration in silicon increases the resistance of radiation detectors to high radiation doses. Unfortunately, high-resistivity float zone (FZ) silicon, needed for radiation detectors, has too low an oxygen content. The solution to this is silicon oxygenation. There are different ways of incorporating oxygen into silicon. The most accepted one is by high-temperature diffusion from a thick SiO2 layer. In this paper, we investigate the impact of this silicon oxygenation technique as well as the application of different gettering techniques to improve the minority carrier lifetime of high-resistivity FZ silicon substrates for radiation detectors. The minority carrier lifetimes before and after Surface etching have been measured on samples subjected to different oxygenation and gettering treatments by using a quasi steady-state photoconductance technique. A lifetime improvement efficiency factor is defined for each treatment process. The lifetime efficiency factors behave independently, so that the lifetime efficiency factors associated with different sequential combinations of treatments can be estimated by a multiplicative combination. Different gettering techniques that improve or degrade the minority carrier lifetime are analyzed, and the best options for silicon radiation detector fabrication are determined. Oxygenated silicon with a minority carrier lifetime close to I ins can be obtained. (C) 2004 The Electrochemical Society.

Recent advances in the field of microelectromechanical systems (MEMS) research can be applied to the fabrication of gaseous electron-multiplying microstructures for use in imaging radiation sensors, and show interesting possibilities in addressing problems encountered with the gas micropattern generation of radiation detectors in some applications, for example, gain instability and electrical breakdowns in high photon fluxes. The use of SU8, an epoxy-based photoresist finding increasing use in MEMS and micromachining applications, is briefly discussed with regard to the construction of gas micropattern detectors, and several devices fabricated with the material are presented. Processes using the material can be adapted to a range of detector geometries, and the ability to fabricate higher level multilayer structures may also allow the incorporation of additional features such as guard electrodes to protect detectors and associated readout electronics against damaging spark events.

A investigation into the suitability of gas microstrip detector technology for a high-speed industrial X-ray tomography system is reported. X-ray energies in the region 20–30keV are well suited to the application, which involves imaging two-dimensional slices through gas/liquid multiphase pipeline flows for quantitative component fraction measurement. Stable operation over a period representing several hundred individual tomographic scans at gas gains of 500 is demonstrated using a Penning gas mixture of krypton/propylene.

Optimisation is essential in modern industrial and chemical process industries to increase efficiency and decrease downtime and maintenance costs. X-ray tomography is being developed to address these issues both on the microscopic level to characterise and quantify unit cell parameters and the macroscopic level for real time measurement of multiphase flow. The behaviour of macroscopic flow can be predicted using finite element simulations. Three-dimensional X-ray micro-tomography with 100 micron resolution has been developed and could be used to determine, for example volume fractions, contact surface area and particle size distribution and used as basic data for modelling of macroscopic systems. Additionally, a high speed X-ray tomography instrument is being developed to measure on-line multiphase flow in fast moving systems. This system does not require moving parts and is expected to operate at up to 50 frames per second. In addition to a practical implementation of this system in an industrial environment it can also be used as a cross-validation of the macroscopic models. Details of each system will be described and the suitability of the applications discussed.

High speed X-ray tomography is being developed for on-line measurement of multiphase flow for well management in the oil industry. To reduce motion artefacts to acceptable levels a source is required that can scan about a 100mm diameter pipe in approximately 20 ms, thus rendering a rotating source an impractical solution. In order to achieve a spatial resolution of 2 mm in the reconstructed image a total of 105 individual projections over a 210 degrees are are required. The large number of point sources means individual X-ray tubes are not practicable. Our solution is to use multiple electron beams where the active focal spot can be rapidly scanned across the target in an are about the pipe with the use of electronic grids. This paper describes a prototype of such a tube designed, in the first instance, to cover a 30 degrees are and consisting of 13 individual emitters. Having proved the principle of operation a full system is now in the design stage and shall be briefly discussed.

Monte Carlo calculations have been widely employed to model the interactions of electrons and photons as they travel through and collide with matter. This approach has been applied with some success to the problem of simulating the response of gas-filled proportional counters, mapping out electron transport through the electric field on an interaction-by-interaction basis. These studies focus on the multiplication of electrons as they drift into the high electric field region of the detector and subsequently avalanche. We are using this technique in our new simulation code to depict avalanching in microgap gas-filled proportional counters, in order to investigate the variation of two principle detector properties with the anode pitch used in the detector. Spatial resolution information can be obtained by measuring the lateral diffusion distance of an electron from the point where it is liberated to the point in the detector where it initiates an avalanche. By also modeling the motion of the positive ions that are left behind from the initial avalanche, we are able to gauge the effect of space charge distortion on subsequent avalanches. This effect is particularly important at the high X-ray count rates that we are interested in for our ultimate aim, which is to use the detectors as part of a high-speed tomography system for imaging multiphase oil/water/gas flows.

This paper describes a new system for quantitative measurement of multiphase flow. It is based on the use of high speed (50 frames per second) X-ray tomographic imaging. This requires a new X-ray tube concept to be implemented, together with an annular detector array and data acquisition system. A pressurised krypton microgap detector is being developed to give 90% quantum efficiency for detection of K/sub /spl alpha// radiation from the silver anode X-ray tube. Results from simulation work are presented to justify the overall design strategy selected.

A technique for measuring oil and water concentrations in a bulk liquid using energy-dispersive X-ray scatter will be discussed. It is a requirement of the oil industry to measure accurately on-line the oil/water ratio of fluids extracted from oil fields across a wide range of gas–liquid flow regimes. To this end, a low cost, robust system is being developed using the energy dependence of coherent scatter as a probe to measure oil/water ratios. The scatter profiles are inherently broad and thus the relaxed energy resolution requirements allow the use of CdZnTe detectors suitable for field deployment. Energy-dispersive diffraction spectra of a range of oil–water emulsions have been measured. The ratio of the scattering into two energy windows, where the diffraction spectrum from oil is maximised and minimised with respect to that of water, is shown to be dependent upon the oil/water mixture ratios. The measurement is made independent of gas volume flow rate by normalisation of the scattered data to the transmission data. A relative error of 0.6% in the oil/water ratio measurement at 80% water fraction, and independent of gas fraction, is obtained.