Table of contents

We review the current status of liquid noble gas radiation detectors with energy threshold in the keV range, which are of interest for direct dark matter searches, measurement of coherent neutrino scattering and other low energy particle physics experiments. Emphasis is given to the operation principles and the most important instrumentation aspects of these detectors, principally of those operated in the double-phase mode. Recent technological advances and relevant developments in photon detection and charge readout are discussed in the context of their applicability to those experiments.

The Voxel Imaging PET (VIP) Pathfinder project intends to show the advantages of using pixelated solid-state technology for nuclear medicine applications. It proposes designs for Positron Emission Tomography (PET), Positron Emission Mammography (PEM) and Compton gamma camera detectors with a large number of signal channels (of the order of 10⁶). For PET scanners, conventional algorithms like Filtered Back-Projection (FBP) and Ordered Subset Expectation Maximization (OSEM) are straightforward to use and give good results. However, FBP presents difficulties for detectors with limited angular coverage like PEM and Compton gamma cameras, whereas OSEM has an impractically large time and memory consumption for a Compton gamma camera with a large number of channels. In this article, the Origin Ensemble (OE) algorithm is evaluated as an alternative algorithm for image reconstruction. Monte Carlo simulations of the PET design are used to compare the performance of OE, FBP and OSEM in terms of the bias, variance and average mean squared error (MSE) image quality metrics. For the PEM and Compton camera designs, results obtained with OE are presented.

We present the results of afterpulse measurements performed as qualification test for 473 inner detector photomultipliers of the Double Chooz experiment. The measurements include the determination of a total afterpulse occurrence probability as well as an average time distribution of these pulses. Additionally, more detailed measurements with different light sources and simultaneous charge and timing measurements were performed with a few photomultipliers to allow a more detailed understanding of the effect. The results of all measurements are presented and discussed.

Resistive-anode micromegas detectors have been in development for several years, in an effort to solve the problem of sparks when working at high flux and high ionizing radiation like in the HL-LHC (up to ten times the luminosity of the LHC). They have been chosen as one of the technologies that will be used in the ATLAS New Small Wheel project (forward muon system). An ageing study is mandatory to assess their capabilities to handle the HL-LHC environment on a long-term period. A prototype has been exposed to several types of irradiation (X-rays, cold neutrons, ⁶⁰Co gammas and alphas) above the equivalent charge produced in the detector in five HL-LHC running years without showing any degradation of the performance in terms of gain and energy resolution, and with the characterization of the tracking performance in terms of efficiency and spatial resolution, verifying non degradation on the exposed resistive micromegas.

The simple two-point theory cannot explain the results of known experimental data of the multipactor (MP) discharge for two-parallel plate. Here the concept of accurate phase stability for resonance and regions not satisfying the resonance condition are presented. In this order the results of numerical simulation and improved theoretical calculation are stated. The results show that the most important thing that can result in a MP discharge is the behaviour of stability factor of the electron during its flights. It seems that introduction of ``main condition'' of phase stability can help to understand the experimental results. In numerical simulation a fixed value for the initial velocity of secondary electron is considered while the random initial rf phase is assumed.

The Hamamatsu R11410 photomultiplier, a tube of 3'' diameter and with a very low intrinsic radioactivity, is an interesting light sensor candidate for future experiments using liquid xenon (LXe) as target for direct dark matter searches. We have performed several experiments with the R11410 with the goal of testing its performance in environments similar to a dark matter detector setup. In particular, we examined its long-term behavior and stability in LXe and its response in various electric field configurations.

Tagging with β-particles at the focal plane of a recoil separator has been shown to be an effective technique for the study of exotic proton-rich nuclei. This article describes three new pieces of apparatus used to greatly improve the sensitivity of the recoil-beta tagging technique. These include a highly-pixelated double-sided silicon strip detector, a plastic phoswich detector for discriminating high-energy β-particles, and a charged-particle veto box. The performance of these new detectors is described and characterised, and the resulting improvements are discussed.

We study the effect of deuteration and annealing on the fluorescence spectrum shape and VUV to visible conversion efficiency of TPB films in a polystyrene matrix with input light from 120 to 220 nm. We observed no discernible difference in the fluorescence spectrum shape between any of the films. The deuterated film performed equally well compared to the standard one in terms of conversion efficiency, but annealing seems to degrade this efficiency to roughly 75% of its non annealed value at all wavelengths studied.

The purpose of the present paper is to propose basic ideas for new types of RPCs to be used in the next generation super-collider experiments as well as in the Cosmic Ray Astrophysics of the next future. The relevant parameters to be improved in view of the first application are the rate capability as well as the timing and tracking accuracy. For the Cosmic Ray (CR) physics a calorimeter approach to the detection of Extensive Air Showers is proposed.

This paper presents the design of the LHCb trigger and its performance on data taken at the LHC in 2011. A principal goal of LHCb is to perform flavour physics measurements, and the trigger is designed to distinguish charm and beauty decays from the light quark background. Using a combination of lepton identification and measurements of the particles' transverse momenta the trigger selects particles originating from charm and beauty hadrons, which typically fly a finite distance before decaying. The trigger reduces the roughly 11 MHz of bunch-bunch crossings that contain at least one inelastic pp interaction to 3 kHz. This reduction takes place in two stages; the first stage is implemented in hardware and the second stage is a software application that runs on a large computer farm. A data-driven method is used to evaluate the performance of the trigger on several charm and beauty decay modes.

The Vacuum Silicon PhotoMultiplier Tube (VSiPMT) is an innovative design we propose for a modern hybrid photodetector based on the combination of a Silicon PhotoMultiplier (SiPM) with a hemispherical vacuum glass PMT standard envelope. The basic idea is to replace the classical dynode chain of a PMT with a SiPM, which acts as an electron multiplying detector. Such a solution will match the goal of a large photocathode sensitive area with the performances of a SiPM. This will lead to many advantages such as lower power consumption, mild sensitivity to magnetic fields and high quantum efficiency. The feasibility of this idea has been throughly studied both from a theoretical and experimental point of view. As a first step we performed the full characterization of a special non-windowed Hamamatsu MPPC with a laser source. The response of the SiPM to an electron beam was studied as a function of the energy and of the incident angle by means of a Geant4-based simulation. In this paper we present the preliminary results of the characterization of the SiPM with an electron source and we discuss how the development of next generation SiPMs will overcome the main weaknesses of VSiPMT, such as relatively low PDE and high photocathode voltage.

A simple model is explored mainly analytically to calculate and understand the PHS of single and multi-layer thermal neutron detectors and to help optimize the design in different circumstances. Several theorems are deduced that can help guide the design.

Silicon detectors are used in High Energy Physics (HEP) experiments as tracking and vertexing devices. The damage caused by radiation is of special interest for sensors to be used at the HL-LHC. The doping profiles of highly irradiated sensors can neither be measured with common capacitance voltage methods nor with methods of chemical analysis. Nevertheless, they need to be known for damage modelling or for simulations of the sensor performance. In this paper it is shown that highly neutron irradiated doping profiles can be measured by using a spreading resistance probe technique. It turned out that the implantation depth of the profiles of active dopants decreases with increasing fluences.

The GERDA experiment searches for the neutrinoless double beta (0νββ) decay of ⁷⁶Ge using high-purity germanium detectors made of material enriched in ⁷⁶Ge. For Phase II of the experiment a sensitivity for the half life T_1/2^0ν   ∼ 2·10²⁶ yr is envisioned. Modified Broad Energy Germanium detectors (BEGe) with thick n⁺electrodes provide the capability to efficiently identify and reject background events, while keeping a large acceptance for the 0νββ-decay signal through novel pulse-shape discrimination (PSD) techniques. The viability of producing thick-window BEGe-type detectors for the GERDA experiment is demonstrated by testing all the production steps from the procurement of isotopically modified germanium up to working BEGe detectors. Comprehensive testing of the spectroscopic as well as PSD performance of the GERDA Phase II prototype BEGe detectors proved that the properties of these detectors are identical to those produced previously from natural germanium material following the standard production line of the manufacturer. Furthermore, the production of BEGe detectors from a limited amount of isotopically modified germanium served to optimize the production, in order to maximize the overall detector mass yield. The results of this test campaign provided direct input for the subsequent production of the enriched germanium detectors.

In this article it is shown analytically that the charge spectrum generated by ionizing particles in Resistive Plate Chambers under Townsend avalanche conditions, that is, for sufficiently small avalanches not affected by space-charge and considering single-electron ionization clusters follows closely the statistical gamma distribution. This distribution describes well comparable simulation data taken from the literature, but seems to describe as well experimental data measured beyond these assumptions, rising some interpretation issues.

Electrical signals induced by pulses of a focused IR (λ = 1064 nm) laser beam in strip detectors were measured using a wide bandwidth current amplifier. The laser beam was focused to a spot with a diameter of about 8 μm and directed to the detector surface. The detector was mounted on a high precision moving stage allowing measurements of signals induced by a laser beam directed to different locations on the detector surface. Measurements were performed with miniature micro-strip detectors made by implanting n⁺ type readout strips on p-type silicon bulk (n⁺-p). Special type of detectors, with implants not fully covered by metal, allowed TCT measurements with a laser beam directed on the implant. The detectors were irradiated with reactor neutrons up to fluences of 5·10¹⁵ n_eq/cm². The signals were measured at reverse bias voltages up to 1000 V. The measurements were repeated after several annealing steps at 60°C. Strong dependence of charge collection on distance of laser beam from the implant was observed in heavily irradiated detectors indicating that charge multiplication is increased at implant edges.

The prototype of the OFFSET (Optical Fiber Folded Scintillating Extended Tracker) tracker is presented. It exploits a novel system for particle tracking, designed to achieve real-time imaging, large detection areas, and a high spatial resolution especially suitable for use in medical diagnostics. The main results regarding the system architecture have been used as a demonstration of the technique which has been patented by the Istituto Nazionale di Fisica Nucleare (INFN). The prototype of this tracker, presented in this paper, has a 20 × 20 cm² sensitive area, consisting of two crossed ribbons of 500 micron square scintillating fibers. The track position information is extracted in real time in an innovative way, using a reduced number of read-out channels to obtain very large detection area with moderate enough costs and complexity. The performance of the tracker was investigated using beta sources, cosmic rays, and a 62 MeV proton beam.

We report on a method to detect an electron cloud in proton accelerators through the measurement of the phase shift of microwaves undergoing controlled reflections with an accelerator vacuum vessel. Previous phase shift measurement suffered from interference signals due to uncontrolled reflections from beamline components, leading to an unlocalized region of measurement and indeterminate normalization. The method in this paper introduces controlled reflectors about the area of interest to localize the measurement and allow normalization. This paper describes analyses of the method via theoretical calculations, electromagnetic modeling, and experimental measurements with a bench-top prototype. Dielectric thickness, location and spatial profile were varied and the effect on phase shift is described. The effect of end cap aperture length on phase shift measurement is also reported. A factor of ten enhancement in phase shift is observed at certain frequencies.

At the Large Hadron Collider, the identification of jets originating from b quarks is important for searches for new physics and for measurements of standard model processes. A variety of algorithms has been developed by CMS to select b-quark jets based on variables such as the impact parameters of charged-particle tracks, the properties of reconstructed decay vertices, and the presence or absence of a lepton, or combinations thereof. The performance of these algorithms has been measured using data from proton-proton collisions at the LHC and compared with expectations based on simulation. The data used in this study were recorded in 2011 at √s = 7 TeV for a total integrated luminosity of 5.0 fb^-1. The efficiency for tagging b-quark jets has been measured in events from multijet and t-quark pair production. CMS has achieved a b-jet tagging efficiency of 85% for a light-parton misidentification probability of 10% in multijet events. For analyses requiring higher purity, a misidentification probability of only 1.5% has been achieved, for a 70% b-jet tagging efficiency.

In this paper we describe the design, construction, and operation of a first large area double-phase liquid argon Large Electron Multiplier Time Projection Chamber (LAr LEM-TPC). The detector has a maximum drift length of 60 cm and the readout consists of a 40 × 76 cm² LEM and 2D projective anode to multiply and collect drifting charges. Scintillation light is detected by means of cryogenic PMTs positioned below the cathode. To record both charge and light signals, we have developed a compact acquisition system, which is scalable up to ton-scale detectors with thousands of charge readout channels. The acquisition system, as well as the design and the performance of custom-made charge sensitive preamplifiers, are described. The complete experimental setup has been operated for a first time during a period of four weeks at CERN in the cryostat of the ArDM experiment, which was equipped with liquid and gas argon purification systems. The detector, exposed to cosmic rays, recorded events with a single-channel signal-to-noise ratio in excess of 30 for minimum ionising particles. Cosmic muon tracks and their δ-rays were used to assess the performance of the detector, and to estimate the liquid argon purity and the gain at different amplification fields.

We have developed an S-band cavity Beam Position Monitor (BPM) in order to measure the position of an electron beam in the final focus area at ATF2, which is the test facility for the final focus design for the International Linear Collider (ILC). The lattice of the ILC Beam Delivery System (BDS) has been modified, requiring a larger physical aperture of 40 mm in the final focus area. The beam orbit measurement in this area is now covered with high resolution S-Band cavity BPMs. In this paper we summarize the design of the cavity BPM and the first experimental results. The calibration slopes were measured as 0.87 counts/μm in the x-coordinate direction and 1.16 counts/μm in the y-coordinate direction.

A Gamma-Ray Spectrometer (GRS) had been developed as a part of the science payload for the first Japanese lunar explorer, Kaguya. The Kaguya was successfully launched from Tanegashima Space Center on September 14, 2007 and was injected into an orbit around the Moon and the mission ended on June 11, 2009. The Kaguya GRS (hereafter KGRS) has a large-volume Ge semiconductor detector of 252 cc as the main detector and bismuth-germanate and plastic scintillators as an active shielding. The Ge detector achieved an energy resolution of 3.0 keV (FWHM) for 1332 keV gamma ray in ground test despite the use of a mechanical cryocooler and observed gamma rays in energies ranging 0.2 to 12 MeV in lunar orbit. It was the first use of a Ge detector for lunar exploration. During the mission, KGRS participated in geochemical survey and investigated the elemental compositions of subsurface materials of the Moon. In this paper, we summarize the overview of the KGRS describing the design and in-flight performance of the instrument. This paper provides basic information required for reading science articles regarding the KGRS's observation data.

The Pierre Auger Observatory in Malargüe, Argentina, is designed to study the properties of ultra-high energy cosmic rays with energies above 10¹⁸eV. It is a hybrid facility that employs a Fluorescence Detector to perform nearly calorimetric measurements of Extensive Air Shower energies. To obtain reliable calorimetric information from the FD, the atmospheric conditions at the observatory need to be continuously monitored during data acquisition. In particular, light attenuation due to aerosols is an important atmospheric correction. The aerosol concentration is highly variable, so that the aerosol attenuation needs to be evaluated hourly. We use light from the Central Laser Facility, located near the center of the observatory site, having an optical signature comparable to that of the highest energy showers detected by the FD. This paper presents two procedures developed to retrieve the aerosol attenuation of fluorescence light from CLF laser shots. Cross checks between the two methods demonstrate that results from both analyses are compatible, and that the uncertainties are well understood. The measurements of the aerosol attenuation provided by the two procedures are currently used at the Pierre Auger Observatory to reconstruct air shower data.

The autonomous control system of PoGOLite is presented. PoGOLite is a balloon borne X-ray polarimeter designed to observe point sources. To obtain scientific data with optimal efficiency, independent of the ground connection, the payload control system has been made autonomous in most functions. The overall system architecture and the interconnections between components, as well as the automation philosophy and software, are described. Results of performance tests are given.

For vertical cryogenic tests of Superconducting Radio Frequency (SRF) cavities for particle accelerators, typically many hundreds of liters of liquid helium are required. The location of the superfluid-helium to vapour interphase undergoes significant change during the test. We describe a new technique based on commercially available quartz tuning forks for measuring the ambient conditions of the helium bath and for precisely determining the liquid to vapour interface during a vertical cavity test. It is shown that transition from the superfluid phase to vapour as well as to the normal-fluid phase can be unambiguously determined. The experimental results are analysed with existing theories of superfluidity, using an approach for the hydrodynamics of oscillating objects immersed into a viscous medium.

Gas Electron Multiplier based detectors have been recently used for neutron measurement at spallation sources and for fusion relevant applications. The present work is meant to characterize the detector sensitivity to γ-ray background which often can represent the main background source associated to neutron measurements. The γ-ray sensitivity has been measured as a function of detector gain and it has been found to be lower than 10⁻⁷at the typical gain used for neutrons detection. Coincidence measurements, giving the possibility to select mono-energetic photons and to suppress background events, allowed to measure the absolute sensitivity at a well defined γ-ray energy and at low interaction rates. The mechanism of interaction and energy deposition of γ-rays in the detector has been studied using MCNPX Monte Carlo simulations.

Resistive Plate Chambers have been chosen as dedicated trigger muon detector for the Compact Muon Solenoid experiment [1] at the Large Hadron Collider [2] at CERN. The system consists of about 3000 m² of double gap RPC chambers placed in both the barrel and endcap muon regions.

About 5.6 fb⁻¹ (2010–2011) of proton-proton collision data have been used to study the performance of the RPC detector and trigger.

A full high voltage scan of all the RPC chambers has been done at beginning of 2011 data taking to evaluate the working point chamber by chamber and to eventually spot aging effects.

The excellent behaviour of the RPC detector can be summarized with an average detector efficiency of about 97%, an average cluster size of 1.8 and an intrinsic noise rate of 0.1 Hz/cm². This is a clear fulfilment of all the requirements decided 18 years ago in the CMS TDR document [3].

The extreme radiation dose received by vertex detectors at the Large Hadron Collider dictates stringent requirements on their cooling systems. To be robust against radiation damage, sensors should be maintained below -20°C and at the same time, the considerable heat load generated in the readout chips and the sensors must be removed. Evaporative CO₂ cooling using microchannels etched in a silicon plane in thermal contact with the readout chips is an attractive option. In this paper, we present the first results of microchannel prototypes with circulating, two-phase CO₂ and compare them to simulations. We also discuss a practical design of upgraded VELO detector for the LHCb experiment employing this approach.

Most luggage inspection systems are based on X-ray transmission technologies, such as radiography and computed tomography. These techniques have limitations, especially with large or dense objects or objects which are placed close to a wall not allowing access to the rear side for radiography (for instance with abandoned luggage). Portable systems using backscattered X-rays could be an alternative solution when analyzing a suspicious object from one side only, without contact, particularly for homeland security applications. However, portable systems are not currently available. X-ray backscatter imaging, unlike X-ray radiography, reveals low Z materials such as explosives, which may be hidden inside luggage or behind a screen. Specific analysis of backscattered spectra can provide further information about the suspect material in the backscatter image. This can help discriminate between explosive and inert materials. In this article, we detail this discrimination process and the associated developed laboratory prototype. Experimental results are presented, demonstrating the system's performance.

NEXT-DEMO is a large-scale prototype of the NEXT-100 detector, an electroluminescent time projection chamber that will search for the neutrinoless double beta decay of \XE using 100–150 kg of enriched xenon gas. NEXT-DEMO was built to prove the expected performance of NEXT-100, namely, energy resolution better than 1% FWHM at 2.5 MeV and event topological reconstruction. In this paper we describe the prototype and its initial results. A resolution of 1.75% FWHM at 511 keV (which extrapolates to 0.8% FWHM at 2.5 MeV) was obtained at 10 bar pressure using a gamma-ray calibration source. Also, a basic study of the event topology along the longitudinal coordinate is presented, proving that it is possible to identify the distinct dE/dx of electron tracks in high-pressure xenon using an electroluminescence TPC.

Due to its unique structure, parallel panel configuration may lead to novel applications for positron emission tomography (PET). The major challenge of panel PET imaging is the limited angle problem, to which the time-of-flight (TOF) information seems to be a promising solution. This work investigated the required TOF capability of a panel PET design, which has a feasible size of field of view (FOV) for human torso. Such a system's corresponding angular coverage can vary from 70 to 102 degrees. The recovery ability of small lesions was assessed, and the contrast recovery coefficient (CRC) and signal-to-noise ratio (SNR) were analyzed, with a full ring PET as the benchmark system. We also varied the timing resolution and the distance between panels, to evaluate their impacts on image quality. Encouraging results were obtained in simulation study. Distortions and artifacts caused by the limited angular coverage were greatly reduced with timing resolutions better than 300 ps. The recovery ability of small lesions in most part of FOV was desirable. Meanwhile, varying panel distance in the range of 25 to 45 cm seemed to have trivial influence, when timing resolution was fixed at 300 ps. That means that such changes of panel distance might not affect the requirement on TOF capability, allowing more flexibility in panel PET's design and applications.

Damage of gradually loaded ductile materials involves a number of physical processes which are highly nonlinear and have different intensity and extent. Dynamic defectoscopy (i.e. defectoscopy of time changing damage processes) combining an X-ray/optical imaging system is proposed for online visualization and analysis of the complex behaviour of such materials. A large area flat panel detector with rather long read out time is used for overall observation of slow damage processes. On the other hand, a semiconductor CdTe Timepix detector with small active area allows following the rapid damage processes occurring in the final phase of specimen failure. Optical imaging of the specimen surface was utilized for analysing the specimen deformations.

Monolithic Active Matrix with Binary Counters (MAMBO) V ASIC has been designed for detecting and measuring low energy X-rays. A nested well structure with a buried n-well (BNW) and a deeper buried p-well (BPW) is used to electrically isolate the detector from the electronics. BNW acts as an AC ground to electrical signals and behaves as a shield. BPW allows for a homogenous electric field in the entire detector volume. The ASIC consists of a matrix of 50 × 52 pixels, each of 105x105μm². Each pixel contains analog functionality accomplished by a charge preamplifier, CR-RC² shaper and a baseline restorer. It also contains a window comparator with Upper and Lower thresholds which can be individually trimmed by 4 bit DACs to remove systematic offsets. The hits are registered by a 12 bit counter which is reconfigured as a shift register to serially output the data from the entire ASIC.

Radiation hard analog to digital converter (ADC) has been designed for future high energy physics experiments. The ADC has been designed in a commercial 130 nm CMOS process and it achieves 12-bit resolution, 25 MS/s sampling speed, 15 mW power consumption and hardness to at least 1.8 Megarad(Si) of total ionizing dose (TID). 16 ADC channels will be placed on one packaged silicon chip. The readout of the Liquid Argon Calorimeter of the ATLAS detector in the planned High-Luminosity Large Hadron Collider is one possible application for this ADC.

The Korea Atomic Energy Research Institute (KAERI) has developed an industrial SPECT to investigate the fluid flow and mixing patterns in columns. It has been found that the industrial SPECT is indeed a very powerful tool to study the hydrodynamics in multiphase reactors. One of the practical issues in the development of industrial SPECTs is to achieve a required imaging resolution of an industrial SPECT with a minimum number of component detectors, the number of which is frequently limited by both the size of the detectors and the total cost of the imaging system. In the present study, a set of different geometries of industrial SPECTs were evaluated by Monte Carlo simulation using MCNPX to determine the minimum number of detectors that will provide a spatial resolution that corresponds to 10% of the cylindrical column diameter. Our results show that 11 and 12 detectors will satisfy the 10% resolution requirement for the 40 cm and 60 cm diameter columns, respectively, for the industrial SPECT and radioisotopes considered in the present study. The conclusion of this result is valid only for the case considered in the present study, but we believe that the same procedure can be applied to other industrial SPECTs for this kind of optimization.

In this study, we have investigated a 2-dimensional gas detector based on plasma display technology as a candidate for the flat-panel radiation detector. Using the Geant4 and Garfield codes, that simulate the passage of particles through matter, we examined the dependence of X-ray absorption and multiplication factors on the Xe-He gas mixture. Prototype detectors, with four different gas mixtures, were designed and fabricated based on the results from the simulations. The performance of four detectors was evaluated by measuring the collected charge density, dark current density and sensitivity. The maximum collected charge occurred when the Xe 80%-He 20% gas mixture was 1.216 μC/cm² at -1800 V. The dark current of this detector varied between 0.124 and 0.321 nA/cm² in the bias range of -300 to -1800 V, which is approximately one-third of the dark current density of an a-Se based detector, in this range. The sensitivity of Xe 80%-He 20% detector was 0.246 nC/mRcm² at 0.61 V/μm. It is about a tenth lower than that of an a-Se based detector at 10 V/μm.

A newly constructed solid state silicon dose profile detector is characterized concerning its sensitive profile. The use of the MEDIPIX2 sensor system displays an excellent method to align an image of an X-ray slit to a sample under test. The scanning from front to reverse side of the detector, show a decrease in sensitivity of 20%, which indicates a minority charge carrier lifetime of 0.18 ms and a diffusion length of 460 μm. The influence of diced edges results in a volumetric efficiency of 59%, an active volume of 1.2 mm² of total 2.1 mm².

The hit signals read out from pixels on planar semi-conductor sensors are grouped into clusters, to reconstruct the location where a charged particle passed through. The spatial resolution of the pixel detector can be improved significantly using the information from the cluster of adjacent pixels. Such analogue cluster creation techniques have been used by the ATLAS experiment for many years giving an excellent performance. However, in dense environments, such as those inside high-energy jets, it is likely that the charge deposited by two or more close-by tracks merges into one single cluster. A clusterization algorithm based on neural network methods has been developed for the ATLAS Pixel Detector. This can identify the shared clusters, split them if necessary, and estimate the positions of all particles traversing the cluster. The algorithm significantly reduces ambiguities in the assignment of pixel detector measurements to tracks within jets, and improves the positional accuracy with respect to standard interpolation techniques, by the use of the 2-dimensional charge distribution information. The reconstruction using the neural network reduces strongly the number of hits shared by more than one track and improves the resolution of the impact parameter by about 15%.

The EndoTOFPET-US project aims to develop a multimodal detector to foster the development of new biomarkers for prostate and pancreatic tumors. The detector will consist of two main components: an external plate, and a PET extension to an endoscopic ultrasound probe. The external plate is an array of LYSO crystals read out by silicon photomultipliers (SiPM) coupled to an Application Specific Integrated Circuit (ASIC). The internal probe will be an highly integrated and miniaturized detector made of LYSO crystals read out by a fully digital SiPM featuring photosensor elements and digital readout in the same chip. The position and orientation of the two detectors will be tracked with respect to the patient to allow the fusion of the metabolic image from the PET and the anatomic image from the ultrasound probe in the time frame of the medical procedure. The fused information can guide further interventions of the organ, such as biopsy or in vivo confocal microscopy.

Studies of radiation hardness of silicon sensors are standardly performed with single-pad detectors evaluating their global electrical properties. In this work we introduce a technique to visualize and determine the spatial distribution of radiation damage across the area of a semiconductor sensor. The sensor properties such as charge collection efficiency and charge diffusion were evaluated locally at many points of the sensor creating 2D maps. For this purpose we used a silicon sensor bump bonded to the pixelated Timepix read-out chip. This device, operated in Time-over-threshold (TOT) mode, allows for the direct energy measurement in each pixel. Selected regions of the sensor were intentionally damaged by defined doses (up to 10¹² particles/cm²) of energetic protons (of 2.5 and 4 MeV). The extent of the damage was measured in terms of the detector response to the same ions. This procedure was performed either on-line during irradiation or off-line after it. The response of the detector to each single particle was analyzed determining the charge collection efficiency and lateral charge diffusion. We evaluated the changes of these parameters as a function of radiation dose. These features are related to the local properties such as the spatial homogeneity of the sensor. The effect of radiation damage was also independently investigated measuring local changes of signal response to γ, and X rays and alpha particles.

A new front-end data acquisition (DAQ) system has been conceived for the data collection of the new detectors which will be installed by the KLOE2 collaboration. This system consists of a general purpose FPGA based DAQ module and a VME board hosting up to 16 optical links. The DAQ module has been built around a Virtex-4 FPGA and it is able to acquire up to 1024 different channels distributed over 16 front-end slave cards. Each module is a general interface board (GIB) which performs also first level data concentration tasks. The GIB has an optical interface, a RS-232, an USB and a Gigabit Ethernet Interface. The optical interface will be used for DAQ purposes while the Gigabit Ethernet interface for monitoring tasks and debug. Two new detectors exploit this strategy to collect data. Optical links are used to deliver data to the VME board which performs data concentration tasks. The return optical link from the board to the GIB is used to initialize the front-end cards. The VME interface of the module implements the VME 2eSST protocol in order to sustain a peak data rate of up to 320 MB/s. At the moment the system is working at the Frascati National Laboratory (LNF).

This study analyzes in detail the defects in bakelite observed in Resistive Plate Counters (RPC) after exposure to high-radiation environment and fluxed with humidified gas mixture at 9 kV voltage. Objective of this study was to identify the nature of defects and their formation mechanism. The defects were observed firstly on the whole RPC inner surface, and their localization mapped. The defected areas have been analyzed with optical and electron microscopy (SEM), and chemically by EDS (Energy Dispersion Spectroscopy) techniques. An area particularly defect-rich also analysed by x-ray diffraction (XRD). Samples of new and fluxed bakelite have been chemically analyzed by ICP-Plasma (via sample total digestion) in order to determine trace elements variations in composition. model is proposed to explain the chemistry of the formation process.

This report delves into the concept of the SIDRA instrument designed for the measurement of energetic fluxes of charged particles in space. It also presents the preliminary laboratory tests results of the breadboard model electronic units. The SIDRA instrument consists of a detector head made of high purity silicon and high performance scintillation detectors, analog and digital signal processing units, and it also includes a secondary power supply module. Preliminary results of Monte Carlo instrument simulation using the CERN GEANT4 tool are presented and the measured key specifications of charge-to-voltage converters, shapers and peak detectors are discussed. Finally, the performance of the digital processing unit with its software and the parameters of the instrument breadboard model, in particular mass, dimensions and power consumption are also presented.

The Daya Bay experiment measures sin ²2θ₁₃ using functionally identical antineutrino detectors located at distances of 300 to 2000 meters from the Daya Bay nuclear power complex. Each detector consists of three nested fluid volumes surrounded by photomultiplier tubes. These volumes are coupled to overflow tanks on top of the detector to allow for thermal expansion of the liquid. Antineutrinos are detected through the inverse beta decay reaction on the proton-rich scintillator target. A precise and continuous measurement of the detector's central target mass is achieved by monitoring the the fluid level in the overflow tanks with cameras and ultrasonic and capacitive sensors. In addition, the monitoring system records detector temperature and levelness at multiple positions. This monitoring information allows the precise determination of the detectors' effective number of target protons during data taking. We present the design, calibration, installation and in-situ tests of the Daya Bay real-time antineutrino detector monitoring sensors and readout electronics.