Table of contents

Monolithic Active Pixel Sensors (MAPS) have been developed since the late 1990s based on silicon substrates with a thin epitaxial layer (thickness of 10–15 μm) in which charge is collected on an electrode, albeit by disordered and slow diffusion rather than by drift in a directed electric field. As a consequence, the signal of these conventional MAPS is small (≈1000 e⁻) and the radiation tolerance is limited. In this paper, the development of a fully Depleted Monolithic Active Pixel Sensors (DMAPS) based on a high resistivity substrate allowing the creation of a fully depleted detection volume is presented. This concept overcomes the inherent limitations of charge collection by diffusion in the standard MAPS designs. We present results from a prototype chip EPCB01 designed in a commercial 150 nm CMOS technology. The technology provides a thin (≈50 μm) high resistivity n-type silicon substrate as well as an additional deep p-well which allows to integrate full CMOS circuitry inside the pixel. Different matrix types with several variants of collection electrodes and pixel electronics have been implemented. Measurements of the analog performance of this first implementation of DMAPS pixels are presented.

In view of a possible application as a charge-particle track readout for an Active Target Time Projection Chamber (AT-TPC), the operating properties of THick Gaseous Electron Multipliers (THGEM) in pure low-pressure Helium were investigated. This paper includes the effective gain dependence on pressure for different detector configurations (single-, double-, triple-cascade setup), long-term gain stability and energy resolution from tracks of 5.5 MeV alpha particles. Stable operational conditions and maximum detector gains of 10⁴–10⁷ have been achieved in pure Helium at pressure ranging from 100 torr up to 760 torr. Energy resolution of 6.65% (FWHM) for 690 keV of energy deposited by 5.5 MeV alpha particles at 350 torr was measured. The expected energy resolution for the full track is around 2.4% (FWHM). These results, together with the robustness of THGEM electrodes against spark damage, make THGEM structures highly competitive compared to other technologies considered for TPC applications in an active target operating with pure noble gases, requiring a high dynamic range and a wide operating pressure range down to few hundred torr.

Kernel density estimation is a convenient way to estimate the probability density of a distribution given the sample of data points. However, it has certain drawbacks: proper description of the density using narrow kernels needs large data samples, whereas if the kernel width is large, boundaries and narrow structures tend to be smeared. Here, an approach to correct for such effects, is proposed that uses an approximate density to describe narrow structures and boundaries. The approach is shown to be well suited for the description of the efficiency shape over a multidimensional phase space in a typical particle physics analysis. An example is given for the five-dimensional phase space of the Λ⁰_b → D⁰pπ⁻ decay.

An out-of-yoke irradiation setup using the proton beam from a cyclotron that ordinary produces radioisotopes for positron emission tomography (PET) has been developed, characterized, calibrated and validated. The current from a 20 μm thick aluminum transmission foil is readout by home-made transimpedance electronics, providing online dose information. The main monitoring variables, delivered in real-time, include beam current, integrated charge and dose rate. Hence the dose and integrated current delivered at a given instant to an experimental setup can be computer-controlled with a shutter. In this work, we report on experimental results and Geant4 simulations of a setup which exploits for the first time the 18 MeV proton beam from a PET cyclotron to irradiate a selected region of a target using the developed irradiation system. By using this system, we are able to deliver a homogeneous beam on targets with 18 mm diameter, allowing to achieve the controlled irradiation of cell cultures located in biological multi-well dishes of 16 mm diameter. We found that the magnetic field applied inside the cyclotron plays a major role for achieving the referred to homogeneity. The quasi-Gaussian curve obtained by scanning the magnet current and measuring the corresponding dose rate must be measured before any irradiation procedure, with the shutter closed. At the optimum magnet current, which corresponds to the center of the Gaussian, a homogenous dose is observed over the whole target area. Making use of a rotating disk with a slit of 0.5 mm at a radius of 150 mm, we could measure dose rates on target ranging from 500 mGy/s down to 5 mGy/s. For validating the developed irradiation setup, several Gafchromic® EBT2 films were exposed to different values of dose. The absolute dose in the irradiated films were assessed in the 2D film dosimetry system of the Department of Radiotherapy of Coimbra University Hospital Center with a precision better than 2%. In the future, we plan to irradiate small animals, cell cultures, or other materials or samples.

In this work, we report a new technique of measuring the leakage current in Silicon Drift Detectors (SDD) and propose to use this technique as a tool for on-board estimation of the radiation damage to the SDD employed in space-borne X-ray spectrometers. The leakage current of a silicon based detector varies with the detector operating temperature and increases with the radiation dose encountered by the detector in the space environment. The proposed technique to measure detector leakage current involves measurement of the reset frequency of the reset type charge sensitive pre-amplifier when the feedback capacitor is charged only due to the detector leakage current. Using this technique, the leakage current is measured for large samples of SDDs having two different active areas of 40 mm² and 109 mm² with 450 micron thick silicon. These measurements are carried out in the temperature range of -50°C to 20°C. At each step energy resolution is measured for all SDDs using Fe-55 X-ray source and shown that the energy resolution varies systematically with the leakage current irrespective of the difference among the detectors of the same as well as different sizes. Thus by measuring the leakage current on-board, it would be possible to estimate the time dependent performance degradation of the SDD based X-ray spectrometer. This can be particularly useful in case where large numbers of SDD are used.

In this work we present a novel idea for a compact spark-protected single amplification stage Micro-Pattern Gas Detector (MPGD). The detector amplification stage, realized with a structure very similar to a GEM foil, is embedded through a resistive layer in the readout board. A cathode electrode, defining the gas conversion/drift gap, completes the detector mechanics. The new structure, that we call micro-Resistive WELL (μ-RWELL), has some characteristics in common with previous MPGDs, such as C.A.T. and WELL, developed more than ten years ago. The prototype object of the present study has been realized in the 2009 by TE-MPE-EM Workshop at CERN. The new architecture is a very compact MPGD, robust against discharges and exhibiting a large gain (∼ 6 × 10³), simple to construct and easy for engineering and then suitable for large area tracking devices as well as huge calorimetric apparata.

The determination of track reconstruction efficiencies at LHCb using J/ψ→μ⁺μ^- decays is presented. Efficiencies above 95% are found for the data taking periods in 2010, 2011, and 2012. The ratio of the track reconstruction efficiency of muons in data and simulation is compatible with unity and measured with an uncertainty of 0.8 % for data taking in 2010, and at a precision of 0.4 % for data taking in 2011 and 2012. For hadrons an additional 1.4 % uncertainty due to material interactions is assumed. This result is crucial for accurate cross section and branching fraction measurements in LHCb.

The performance of missing transverse energy reconstruction algorithms is presented using √s=8 TeV proton-proton (pp) data collected with the CMS detector. Events with anomalous missing transverse energy are studied, and the performance of algorithms used to identify and remove these events is presented. The scale and resolution for missing transverse energy, including the effects of multiple pp interactions (pileup), are measured using events with an identified Z boson or isolated photon, and are found to be well described by the simulation. Novel missing transverse energy reconstruction algorithms developed specifically to mitigate the effects of large numbers of pileup interactions on the missing transverse energy resolution are presented. These algorithms significantly reduce the dependence of the missing transverse energy resolution on pileup interactions. Finally, an algorithm that provides an estimate of the significance of the missing transverse energy is presented, which is used to estimate the compatibility of the reconstructed missing transverse energy with a zero nominal value.

We consider beam dynamics in azimuthally-symmetric accelerating cavities, using the EMMA FFAG cavity as an example. By fitting a vector potential to the field map, we represent the linear and non-linear dynamics using truncated power series and mixed-variable generating functions. The analysis provides an accurate model for particle trajectories in the cavity, reveals potentially significant and measurable effects on the dynamics, and shows differences between cavity focusing models. The approach provides a unified treatment of transverse and longitudinal motion, and facilitates detailed map-based studies of motion in complex machines like FFAGs.

In axially-symmetric magnets for particle accelerators, the magnetic field is usually surveyed by expensive and time-consuming 3D Hall-probe mappers. Problems arise for a coherent treatment among beam physics requirements, magnet design and manufacturing, and magnetic measurements. For example, when the longitudinal direction of the mapper is misaligned with respect to the magnet, the measured fringe fields will show spurious components. In this paper, an alternative measurement method, exploiting the inherent axial symmetry of the magnetic field, is proposed. The magnetic flux linked with a pair of sensing coils is measured as a function of the longitudinal position. An induction transducer, sensitive to the longitudinal and radial components of the magnetic field, and a measurement system have been designed and prototyped. The experimental proof-of-principle demonstration of the method in comparison with a Hall-probe mapper is presented for a solenoid magnet.

Muon absorption radiography is an imaging technique based on the analysis of the attenuation of the cosmic-ray muon flux after traversing an object under examination. While this technique is now reaching maturity in the field of volcanology for the imaging of the innermost parts of the volcanic cones, its applicability to other fields of research has not yet been proved. In this paper we present a study concerning the application of the muon absorption radiography technique to the field of archaeology, and we propose a method for the search of underground cavities and structures hidden a few metres deep in the soil (patent [1]). An original geometric treatment of the reconstructed muon tracks, based on the comparison of the measured flux with a reference simulated flux, and the preliminary results of specific simulations are discussed in details.

Fast neutron radiography (FNR) is an important non-destructive technique for the imaging of thick bulk material. We are designing a FNR system using a laboratory based 14 MeV D-T neutron generator [1]. Simulation studies have been carried using Monte Carlo based GEANT4 code to understand the response of the FNR system for various objects. Different samples ranging from low Z, metallic and high Z materials were simulated for their radiographic images. The quality of constructed neutron radiography images in terms of relative contrast ratio and the contrast to noise ratio were investigated for their dependence on various parameters such as thickness, voids inside high/low Z material and also for low Z material hidden behind high Z material. We report here the potential and limitations of FNR for imaging different materials and a few configurations and also the possible areas where FNR can be implemented.

A 20 MeV, 30 mA CW proton linac is being developed at BARC, Mumbai. This linac will consist of an ECR ion source followed by a Radio Frequency Quadrupole (RFQ) and Drift tube Linac (DTL). The low energy beam transport (LEBT) line is used to match the beam from the ion source to the RFQ with minimum beam loss and increase in emittance. The LEBT is also used to eliminate the unwanted ions like H₂⁺ and H₃⁺ from entering the RFQ. In addition, space charge compensation is required for transportation of such high beam currents. All this requires careful design and optimization. Detailed beam dynamics simulations have been done to optimize the design of the LEBT using the Particle-in-cell code TRACEWIN. We find that with careful optimization it is possible to transport a 30 mA CW proton beam through the LEBT with 100% transmission and minimal emittance blow up, while at the same time suppressing unwanted species H₂⁺ and H₃⁺ to less than 3.3% of the total beam current.

The Silicon Drift Detectors (SDDs) have replaced simple diodes in demanding X-ray fluorescence applications like in element analysers capable of detecting light elements. The reason for this is that with similar collection area the SDDs have a much smaller output capacitance than diodes due to a much smaller anode size. Thus the SDDs provide much better Signal to Noise Ratio (SNR) at smaller signal levels than diodes. The small capacitance in SDDs is achieved by placing concentric rings around a miniature sized anode. These rings are biased such that inside the SDD's fully depleted bulk a radial electric field component is established guiding signal charges towards the anode.

Problems complicating the design of SDDs are positive oxide charge and interface dark noise. The latter is caused when leakage current generated at depleted interfaces mixes with the signal charge. It has been shown previously that by utilizing a chain of resistors connected to SDD's p+ drift rings and intermediate n+ rings both of these problems can be solved but the resistor chain arrangement requires an additional process step, which may not be standardly available. The interface generated dark noise and the requirement for a resistor chain can be removed by implementing suitable gaps in the p+ rings or with a resistive spiral as well as by implementing an additional anode for the collection of interface leakage current. Such SDDs are, however, vulnerable to accumulation of positive oxide charge complicating the manufacturing and likely reducing the effective lifetime of the detector.We present an SDD design comprising a novel ring arrangement preventing the formation of interface dark noise, being resistant to positive oxide charge, and removing the need for a resistor chain. In this work the design and operation principle of the proposed SDD is presented. The operation of the proposed SDD has been evaluated on TCAD with cylindrically symmetric 3D process and device simulations.

The aim of the present work is to assess the operational characteristics of the PIXIRAD Imaging Counter for use in high-definition energy resolved X-ray imaging for different applications. The PIXIRAD imager was developed by an INFN-Pisa Spin-off. It works in photon counting mode in a wide energy range, soft and hard X-rays (2–100 keV), with pulse discrimination defined by two thresholds. The 650 μ m thick CdTe X-ray sensor is interfaced with a CMOS VLSI chip organized on a 512× 476 matrix of 55 μ m exagonal pixels (total active area of 30.7× 24.8 mm²). The experimental characterization was carried out in the range 3.7–80 keV, to assess the energy discrimination capability and detection efficiency of the PIXIRAD. Energy discrimination in bands was investigated using calibrated monochromatic X-ray sources (fluorescence of Ca, Fe, Cu, Br, Mo, Ag, I, Ta) and a BaCs radioactive source. In addition, two absolutely calibrated X-ray sources (Moxtek 50 kV Bullet and Oxford Instruments SB-80-1M) were utilized. The experimental data show that the PIXIRAD energy response is linear up to about 15 keV, beyond which the cluster size becomes larger than the pixel dimension. It produces multiple counts resulting in a tail at lower energy. Energy resolution was estimated to be about 30%. The effects in term of energy discrimination and a ``smooth energy discrimination'' in bands has been investigated by studying the separation between different energy lines, acquiring combined images with different energy ranges and setting properly the PIXIRAD threshold.

The position sensitive detectors operate in high intensity radiation field of the collider experiment [1]. Important task is to estimate the influence of different radiation effects on properties of the detector. We focus on the laboratory studies to estimate the reliability of different types of silicon detectors. We use the simple test structures produced by standard technology for the silicon detectors. We give the primary attention to the case when the depth of active detector region varies from 10 to 20 μ m because it leads to the most significant influence of SiO₂-Si interface on processes in silicon bulk. We present the experimental results of long term irradiation test with Am²⁴¹ (one year). Influence of the environmental conditions on the fixed charge states in silicon dioxide was investigated using developed simple model.

The applications of active matrix flat-panel imagers (AMFPIs) in large-area x-ray imaging systems have increased over time but are still severely limited owing to its pixel resolution, complex fabrication processes, and high cost. As a solution, x-ray light valve (XLV) technology was introduced and expected to have a better resolution and contrast ratio than those of AMFPI, owing to its micrometer level of the LC cells and signal amplification by an external light source. The twisting angle of the LC cells was changed by charge carrier signals created in a photoconductor layer against x-rays, and the diagnostic images from XLV were acquired from the transmittance of the external light source. However, there was a possibility that the photoconductor layer may be crystallized or degenerated due to the application of high temperatures for sealing the LC layer during the fabrication process. To solve such problems, polymer-dispersed liquid crystals (PDLCs), which do not need high temperature for the sealing process of the LC layer, are used in this study instead of typical LC cells. A photoconductor and PDLC are combined to develop an x-ray detector. An external light source and optical sensor are used to investigate the light transmission of the PDLC . The PDLCs used in this paper do not need polarizers and are self-adhesive. Hence, the transmittance is very high in the transparent state, which allows for a linear x-ray response and sufficient dynamic range in digital radiography.

Very recently we have shown that CUBE-preamplifiers developed by XGLab s.r.l. can be used for the readout of single elements of thick structured planar HPGe- and Si(Li)-detectors produced by SEMIKON [1]. In this paper we will present the results of a simultaneous multi-element readout of structured detectors using the same preamplifiers for measuring high-energy x-rays (more than 100 keV) with a comparable energy resolution as for the single-element readout. Several high-purity germanium detectors (HPGe-detectors) with different position sensitive structures on one detector contact have been used for the first tests. In addition to that we have modified an existing 16-pixel HPGe-polarimeter from GSI-Darmstadt with the new readout. The detector elements (7 mm × 7 mm each, arranged in a 4 × 4 matrix) are connected to CUBE-preamplifiers used in pulse-reset mode. The technological progress achieved with this detector system resulting in a significant improved energy resolution will contribute a lot to much more precise polarization measurements of x-rays emitted from atom-ion collisions which are part of the physics program of the SPARC collaboration (Stored Particles Atomic Physics Research Collaboration) at GSI and the future FAIR accelerator facility (Facility for Antiproton and Ion Research).

The Global Trigger (GT) is the final step of the CMS Level-1 Trigger and implements the ``menu'' of triggers, which is a set of selection requirements applied to the final list of objects (such as muons, electrons or jets) to trigger the readout of the detector and serve as basis for further calculations by the High Level Trigger. Operational experience in developing trigger menus from the first LHC run has shown that the requirements increased as the luminosity and pile-up increased. The new GT (μGT) is designed based on Xilinx Virtex-7 FPGAs, which combine unsurpassed flexibility with regard to scalability and high robustness. Furthermore, a custom board which receives signals from legacy electronics and basic binary inputs from less complex trigger sources is presented. Additionally, this paper describes the architecture of a distributed testing framework and the Trigger Menu Editor.

Results of gamma-ray measurements taken with Lutetium Fine Silicate (LFS) scintillators and Micro-Pixel Avalanche Photodiodes (MAPD) are presented in the energy range of 59.6 keV to 834.8 keV . Dependences of energy resolution on gamma-ray energy are studied. Results of several measurements are discussed to assess the performance of gamma ray source identification of the developed detector. The alpha particle and neutron detection performance of LFS and stilbene scintillators coupled to micro-pixel avalanche photodiode are discussed as well.

The high-luminosity upgrade of the Large Hadron Collider foreseen for 2023 resulted on the decision to replace the tracker system of the CMS experiment. The innermost layer of the new pixel detector will experience fluences in the order of ϕ_eq ≈ 10¹⁶ cm⁻² and a dose of ≈ 5 MGy after an integrated luminosity of 3000 fb⁻¹. Several materials and designs are under investigation in order to build a detector that can withstand such high fluences. Thin planar silicon sensors are good candidates to achieve this goal since the degradation of the signal produced by traversing particles is less severe than for thicker devices. A study has been carried out in order to characterize highly irradiated planar epitaxial silicon sensors with an active thickness of 100 μm. The investigation includes pad diodes and strip detectors irradiated up to a fluence of ϕ_eq = 1.3 × 10¹⁶ cm⁻², and 3 × 10¹⁵ cm⁻², respectively.

The electrical properties of diodes have been characterized using laboratory measurements, while measurements have been carried out at the DESY II test beam facility to characterize the charge collection of the strip detectors. A beam telescope has been used to determine precisely the impact position of beam particles on the sensor. This allows the unbiased extraction of the charge deposited in the strip sensor and good identification of the noise. In this paper, the results obtained for p-bulk sensors are shown. The charge collection efficiency of the strip sensors is 90% at 1000 V after a fluence of ϕ_eq = 3 × 10¹⁵ cm⁻². The irradiated diodes show charge multiplication effects. The impact of the threshold applied to a detector on its efficiency is also discussed.

We have studied the calibration of PMTs in scintillation detectors, inducing single electron response on the PMT from primary scintillation produced by x-ray interaction. The results agree with those obtained by the commonly used single electron response (SER) method, which uses LED light pulses to induce the PMT SER. The use of the primary scintillation for PMT calibration will be convenient in situations where the PMT is already in situ, when it becomes difficult or even impossible to apply the SER method, e.g. in commercial sealed scintillator/PMT devices. Furthermore, we have experimentally investigated the possibility of fitting the high-charge tail of the PMT SER pulse-height distribution to an exponential function, inferring the PMT gain from the inverse of the exponent. The results of the exponential fit method agree with those obtained by the SER method for pulse-height distributions resulting from an average number of around 1.0 photoelectrons reaching the first dynode per light/scintillation pulse. The SER method has higher precision and, therefore, is used in a larger number of applications. Nevertheless, the exponential fit method will be useful in situations where the single photoelectron peak is under the background or noise peak and it may present an alternative, simple way, for relative gain calibration of PMT arrays as well as for monitoring the PMT gain variations.

The LHC accelerator's first long shutdown period (LS1), in 2013–2014, has given the experiments the opportunity to perform planned upgrade and maintenance activities on systems and equipment. It has also been the right time to conduct a preventive maintenance campaign on crate and power supply equipment which is foreseen to operate smoothly for another 4 to 8 years. This paper presents the lessons learned during the LS1 power supply preventive maintenance activities as well as an in-depth analysis of the most common failure modes and weaknesses encountered on the power supplies in the LHC experiments over the past years of operation.

The Belle II experiment, an upgrade of the existing Belle detector at the e⁺e⁻ SuperKEKB collider at KEK, has chosen a pixel detector built with the DEPFET technology for the two innermost layers. The physics goals of the experiment impose challenging requirements to the design of the pixel detector in terms of performance, material budget and power consumption. This paper evaluates the DEPFET pixel detector for Belle II and the various system aspects behind its final design.

The GigaBit Laser Driver (GBLD) is a key on-detector component of the GigaBit Transceiver (GBT) system at the transmitter side. As part of the design efforts towards the upgrade of the electrical components of the LHC experiments, a 10 Gb/s GBLD (GBLD10) has been developed in a 130 nm CMOS technology. The GBLD10 is based on the distributed-amplifier (DA) architecture and achieves data rates up to 10 Gb/s. It is capable of driving VCSELs with modulation currents up to 12 mA. Moreover, a pre-emphasis function has been included in the proposed laser driver in order to compensate for the capacitive load and channel losses.

ATLAS is one of the four big LHC experiments and recently its Pixel Detector was upgraded with a new innermost 4th layer: the Insertable B-Layer (IBL) . The upgrade will result in better tracking efficiency, improved precision of measurements and, in the future, compensation for radiation damage of the Pixel-Detector. Newly developed front-end electronics and the higher than originally planned LHC luminosity required a complete re-design of the Off Detector Electronics consisting of the Back Of Crate card (BOC) and the Read Out Driver (ROD) . The main purposes of the BOC card are the distribution of the LHC clock to all Pixel Detector components as well as interfacing the detector and the higher level readout optically. The data-path to the detector runs a 40 MHz bi phase mark (BPM) encoded stream. The 160 MHz 8b10b encoded data path from the detector is phase and word aligned in the firmware and then forwarded to the ROD after decoding. The ROD will send out the processed data that is then forwarded to the higher level readout by the BOC card. An overview of the newly developed firmware will be presented together with the results from production tests and the system test at CERN . Focus is put on the partial reconfiguration and results of the fine delay measurements.

A prototype composed of four resistive plate chamber layers has been exposed to quasi-monoenergetic neutrons produced from a deuteron beam of varying energy (300 to 1500 AMeV) in experiment S406 at GSI, Darmstad, Germany. Each layer, with an active area of about 2000 × 500 mm², is made of modules containing the active gaps, all in multigap construction. Each gap is defined by 0.3 mm nylon mono-filaments positioned between 2.85 mm thick float glass electrodes. The modules are operated in avalanche mode with a non-flammable gas mixture composed of 90% C₂H₂F₄ and 10% SF₆. The signals are readout by a pick-up electrode formed by 15 copper strips (per layer), spaced at a pitch of 30 mm, connected at both sides to timing front end electronics. Measurements of the time of flight jitter of neutrons, in the mentioned energy range, point to a contribution of the resistive plate chamber in the order of 150 ps, independent of the neutron energy.

The LHCb experiment is upgrading part of its detector and the entire readout system towards a full 40 MHz readout system in order to run between five and ten times its initial design luminosity and increase its trigger efficiency. In this paper, the new timing, trigger and control distribution system for such an upgrade is reviewed with particular attention given to the distribution of the clock and timing information across the entire readout system, up to the FE and the on-detector electronics. Current ideas are here presented in terms of reliability, jitter, complexity and implementation.

Particle Therapy (PT) is an emerging technique, which makes use of charged particles to efficiently cure different kinds of solid tumors. The high precision in the hadrons dose deposition requires an accurate monitoring to prevent the risk of under-dosage of the cancer region or of over-dosage of healthy tissues. Monitoring techniques are currently being developed and are based on the detection of particles produced by the beam interaction into the target, in particular: charged particles, result of target and/or projectile fragmentation, prompt photons coming from nucleus de-excitation and back-to-back γ s, produced in the positron annihilation from β + emitters created in the beam interaction with the target. It has been showed that the hadron beam dose release peak can be spatially correlated with the emission pattern of these secondary particles. Here we report about secondary particles production (charged fragments and prompt γ s) performed at different beam and energies that have a particular relevance for PT applications: ¹²C beam of 80 MeV/u at LNS, ¹²C beam 220 MeV/u at GSI, and ¹²C, ⁴He, ¹⁶O beams with energy in the 50–300 MeV/u range at HIT. Finally, a project for a multimodal dose-monitor device exploiting the prompt photons and charged particles emission will be presented.

The luminosity of the Large Hadron Collider (LHC) will be increased during the Long Shutdown of 2022 and 2023 (LS3) in order to increase the sensitivity of its experiments. A completely new inner detector for the ATLAS experiment needs to be developed to withstand the extremely harsh environment of the upgraded, so-called High-Luminosity LHC (HL-LHC). High radiation hardness as well as granularity is mandatory to cope with the requirements in terms of radiation damage as well as particle occupancy.

A new silicon detector concept that uses commercial high voltage and/or high resistivity full complementary metal-oxide-semiconductor (CMOS) processes as active sensor for pixel and/or strip layers has risen high attention, because it potentially provides high radiation hardness and granularity and at the same time reduced price due to the commercial processing and possibly relaxed requirements for the hybridization technique. Results on the first prototypes characterized in a variety of laboratory as well as test beam environments are presented.

The increased energy and luminosity of the LHC in the run-2 data taking period requires a more selective trigger menu in order to satisfy the physics goals of ATLAS. Therefore the electronics of the central trigger system is upgraded to allow for a larger variety and more sophisticated trigger criteria. In addition, the software controlling the central trigger processor (CTP) has been redesigned to allow the CTP to accommodate three freely configurable and separately operating sets of sub detectors, each independently using the almost full functionality of the trigger hardware. This new approach and its operational advantages are discussed as well as the hardware upgrades.

An associative memory-based track finding approach has been proposed for a Level 1 tracking trigger to cope with increasing luminosities at the LHC. The associative memory uses a massively parallel architecture to tackle the intrinsically complex combinatorics of track finding algorithms, thus avoiding the typical power law dependence of execution time on occupancy and solving the pattern recognition in times roughly proportional to the number of hits. This is of crucial importance given the large occupancies typical of hadronic collisions. The design of an associative memory system capable of dealing with the complexity of HL-LHC collisions and with the short latency required by Level 1 triggering poses significant, as yet unsolved, technical challenges. For this reason, an aggressive R&D program has been launched at Fermilab to advance state of-the-art associative memory technology, the so called VIPRAM (Vertically Integrated Pattern Recognition Associative Memory) project. The VIPRAM leverages emerging 3D vertical integration technology to build faster and denser Associative Memory devices. The first step is to implement in conventional VLSI the associative memory building blocks that can be used in 3D stacking; in other words, the building blocks are laid out as if it is a 3D design. In this paper, we report on the first successful implementation of a 2D VIPRAM demonstrator chip (protoVIPRAM00). The results show that these building blocks are ready for 3D stacking.

The TORCH detector is proposed for the low-momentum particle identification upgrade of the LHCb experiment. It combines Time-Of-Flight and Cherenkov techniques to achieve charged particle separation up to 10 GeV/c. This requires a time resolution of 70 ps for single photons. Existing electronics has already demonstrated a 26 ps intrinsic time resolution; however the channel count and density need improvements for future micro-channel plate devices. This paper will report on a scalable design using custom ASICs (NINO-32 and HPTDC). The system provides up to 8 × 64 channels for a single micro-channel plate device. It is also designed to read out micro-channel plate tubes with charge-sharing technique.

For the next run of the LHC, the ATLAS Level-1 trigger system will include topological information on trigger objects from the calorimeters and muon detectors. In order to supply coarse grained muon topological information, the existing MUCTPI (Muon-to-Central-Trigger-Processor Interface) system has been upgraded. The MIOCT (Muon Octant) module firmware has been then modified to extract, encode and send topological information through the existing MUCTPI electrical trigger outputs. The topological information from the muon detectors will be sent to the Level-1 Topological Trigger Processor (L1Topo) through the MUCTPI-to-Level-1-Topological-Processor (MuCTPiToTopo) interface. Examples of physics searches involving muons are: search for Lepton Flavour Violation, Bs-physics, Beyond the Standard Model (BSM) physics and others. This paper describes the modifications to the MUCTPI and its integration with the full trigger chain.

Through the years the Micromegas (MICRO MEsh GAseous Structure) devices have proven to be reliable detectors with excellent space resolution and high rate capability. Large area Micromegas will be employed for the first time in high-energy physics for the Muon Spectrometer upgrade of the ATLAS experiment at the CERN LHC. A total surface of about 150 m² of the forward regions of the Muon Spectrometer will be equipped with 8 layers of Micromegas modules. Each module covers a surface from 2 to 3 m² for a total active area of 1200 m². Together with the small-strips Thin Gap Chambers, they will compose the two New Small Wheels, which will replace the innermost stations of the ATLAS Endcap Muon tracking system in the 2018/19 shutdown. The breakthroughs and developments of this type of Micro Pattern Gas Detector will be reviewed, along with the path towards the construction of the modules, which will take place in several production sites starting in 2015. An overview of the detector performance obtained in the test beam campaigns in recent years at CERN will be also presented.

The ALICE/PHOS detector is carrying out a major upgrade of its readout electronics for the RUN 2 of LHC (2015-2017). A new architecture based on the point to point link is developed. The event readout rate can achieve 30 kHz by replacing the old parallel GTL bus with DTC links. The communication stability of the interface between front-end electronic boards and readout concentrators is significantly improved. A new FPGA firmware is designed to be compatible with the upgraded ALICE trigger system and DATE software.

The PixFEL project aims to develop an advanced X-ray camera for imaging suited for the demanding requirements of next generation free electron laser (FEL) facilities. New technologies can be deployed to boost the performance of imaging detectors as well as future pixel devices for tracking. In the first phase of the PixFEL project, approved by the INFN, the focus will be on the development of the microelectronic building blocks, carried out with a 65 nm CMOS technology, implementing a low noise analog front-end channel with high dynamic range and compression features, a low power ADC and high density memory. At the same time PixFEL will investigate and implement some of the enabling technologies to assembly a seamless large area X-ray camera composed by a matrix of multilayer four-side buttable tiles. A pixel matrix with active edge will be developed to minimize the dead area of the sensor layer. Vertical interconnection of two CMOS tiers will be explored to build a four-side buttable readout chip with small pixel pitch and all the on-board required functionalities. The ambitious target requirements of the new pixel device are: single photon resolution, 1 to 10⁴ photons @ 1 keV to 10 keV input dynamic range, 10-bit analog to digital conversion up to 5 MHz, 1 kevent in-pixel memory and 100 μm pixel pitch. The long term goal of PixFEL will be the development of a versatile X-ray camera to be operated either in burst mode (European XFEL), or in continuous mode to cope with the high frame rates foreseen for the upgrade phase of the LCLS-II at SLAC.

The AEgIS experiment is an interdisciplinary collaboration between atomic, plasma and particle physicists, with the scientific goal of performing the first precision measurement of the Earth's gravitational acceleration on antimatter. The principle of the experiment is as follows: cold antihydrogen atoms are synthesized in a Penning-Malmberg trap and are Stark accelerated towards a moiré deflectometer, the classical counterpart of an atom interferometer, and annihilate on a position sensitive detector. Crucial to the success of the experiment is an antihydrogen detector that will be used to demonstrate the production of antihydrogen and also to measure the temperature of the anti-atoms and the creation of a beam. The operating requirements for the detector are very challenging: it must operate at close to 4 K inside a 1 T solenoid magnetic field and identify the annihilation of the antihydrogen atoms that are produced during the 1 μs period of antihydrogen production. Our solution—called the FACT detector—is based on a novel multi-layer scintillating fiber tracker with SiPM readout and off the shelf FPGA based readout system. This talk will present the design of the FACT detector and detail the operation of the detector in the context of the AEgIS experiment.

The ALICE and ATLAS DAQ systems read out detector data via point-to-point serial links into custom hardware modules, the ALICE RORC and ATLAS ROBIN. To meet the increase in operational requirements both experiments are replacing their respective modules with a new common module, the C-RORC. This card, developed by ALICE, implements a PCIe Gen 2 x8 interface and interfaces to twelve optical links via three QSFP transceivers. This paper presents the design of the C-RORC, its performance and its application in the ALICE and ATLAS experiments.

For the High-Luminosity upgrade of the LHC (HL-LHC), phase I, the CMS pixel detector needs to be replaced. In order to improve the tracking resolution even at high luminosity the pixel detector is upgraded by a fourth barrel layer.

This paper describes the production process and results for the fourth barrel layer for the CMS silicon pixel detector, upgrade phase I. The additional barrel layer will be produced by KIT and DESY. Both research centers have commonly developed and investigated new production processes, including SAC solder bump jetting, gold stud bumping and "Precoat by Powder Processes" (PPS) to bump the sensor tiles and prepare them for the flip-chip process. First bare modules have been produced with the new digital ROC.

The Beam Radiation Instrumentation and Luminosity Project of the CMS experiment consists of several beam monitoring systems and luminometers. The upgraded Fast Beam Conditions Monitor is based on 24 single crystal diamond sensors with a two-pad metallization and a custom designed readout. Signals for real time monitoring are transmitted to the counting room, where they are received and processed by new back-end electronics designed to measure count rates on LHC collision, beam induced background and activation products to be used to determine the luminosity and the machine induced background. The system architecture and the signal processing algorithms will be presented.

The ATCA and μTCA standards include industry-standard data pathway technologies such as Gigabit Ethernet which can be used for control communication, but no specific hardware control protocol is defined. The IPbus suite of software and firmware implements a reliable high-performance control link for particle physics electronics, and has successfully replaced VME control in several large projects. In this paper, we outline the IPbus control system architecture, and describe recent developments in the reliability, scalability and performance of IPbus systems, carried out in preparation for deployment of μTCA-based CMS upgrades before the LHC 2015 run. We also discuss plans for future development of the IPbus suite.

New fiber optical transceivers, opto-boards, were designed and produced to replace the first generation opto-boards installed in the ATLAS pixel detector and for the new pixel layer, the insertable barrel layer (IBL). Each opto-board contains one 12-channel PIN array and two 12-channel VCSEL arrays along with associated receiver and driver ASICs. The new opto-board design benefits from the production and operational experience of the first generation opto-boards and contains several improvements. The new opto-boards have been successfully installed. Additionally, a set of the new opto-boards have been subjected to an accelerated lifetime experiment at 85 C and 85% relative humidity for over 1,000 hours. No failures were observed. We are cautiously optimistic that the new opto-boards will survive until the shutdown for the detector upgrade for the high-luminosity Large Hadron Collider (HL-LHC).

We present ASIC designs of VCSEL drivers for a single VCSEL (LOCld1), two individual VCSELs (LOCld2) and a four-channel VCSEL array (LOCld4). This work is for new detector readout systems needed in the Large Hadron Collider upgrade program. All ASICs are fabricated in a commercial 0.25-μ m Silicon-on-Sapphire CMOS technology. LOCld1 and LOCld2 have passed the 8-Gbps and 10-Gbps eye mask tests. Operating at 8 Gbps data rate, the measured total jitter of LOCld1 and LOCld2 is less than 30 ps, and the power comsuption is about 200 mW per channel with 6-mA bias current and 6.4-mA modulation current. The radiation tolerance of LOCld1 has been qualified with x-ray and high-energy neutron beam test.

The Cherenkov Telescope Array (CTA) project [1] aims to build the largest ground-based gamma-ray observatory based on an array of Imaging Atmospheric Cherenkov Telescopes (IACTs). The CTA will implement a multi-level trigger system to distinguish between gamma ray-like induced showers and background images induced by night sky background (NSB) light [2]. The trigger system is based on coincident detections among pixels (level 0 trigger), clusters of pixels (level 1) or telescopes. In this article, the first version of the application specific integrated circuit (ASIC) for Level 1 trigger system is presented, capable of working with different Level 0 strategies and different trigger region sizes. In addition, it complies with all the requirements specified by the CTA project, specially the most critical ones as regards noise, bandwidth, dynamic range and power consumption. All these features make the presented system very suitable for use in the CTA cameras and improve the features of discrete components prototypes of the L1 trigger circuit in terms of compactness, noise, performance and power consumption.

For many years, silicon micro-strip detectors have been successfully used as tracking detectors for particle and nuclear physics experiments. A new application of this technology is to the field of particle therapy, where radiotherapy is carried out by use of charged particles such as protons or carbon ions. Such a treatment has been shown to have advantages over standard x-ray radiotherapy and as a result of this, many new centres offering particle therapy are currently under construction—including two in the U.K.. The characteristics of a new silicon micro-strip detector based system for this application will be presented. The array uses specifically designed large area sensors in several stations in an x-u-v co-ordinate configuration suitable for very fast proton tracking with minimal ambiguities. The sensors will form a tracker capable of giving information on the path of high energy protons entering and exiting a patient. This will allow proton computed tomography (pCT) to aid the accurate delivery of treatment dose with tuned beam profile and energy. The tracker will also be capable of proton counting and position measurement at the higher fluences and full range of energies used during treatment allowing monitoring of the beam profile and total dose. Results and initial characterisation of sensors will be presented along with details of the proposed readout electronics. Radiation tests and studies with different electronics at the Clatterbridge Cancer Centre and the higher energy proton therapy facility of iThemba LABS in South Africa will also be shown.

Thermal neutron absorber gadolinium (Gd) with a large reaction cross section is applied to resistive plate chamber detectors, so a gaseous detector RPC-Gd is developed to discriminate thermal neutrons. Through analyzing the operation principle of RPC-Gd detectors and testing n/γ spectrum, a method by supplying different operation high voltage of RPC module is used for discriminating thermal neutrons and γ . In the end, based on the production technology and operation principle of RPC, two prototypes of single/double RPC modules are designed for producing large area and low cost detector to monitor thermal neutron.

The LHCb experiment has proposed an upgrade towards a full 40 MHz readout system in order to run between five and ten times its initial design luminosity. The entire Front-End electronics will be upgraded in order to cope with higher sub-detector occupancy, higher data rate and to work in a complete trigger-less fashion. In this paper, we describe a novel way to transmit slow control information to the Front-End electronics, by profiting from bidirectional optical connections and the GBT and GBT-SCA chipset capabilities. The implementation and preliminary validation tests are shown as well.

The Jovian system is the subject of study for the Jupiter Icy Moon Explorer (JUICE), an ESA mission which is planned to launch in 2022. The scientific payload is designed for both characterisation of the magnetosphere and radiation environment local to the spacecraft, as well as remote characterisation of Jupiter and its satellites. A key instrument on JUICE is the high resolution and wide angle camera, JANUS, whose main science goals include detailed characterisation and study phases of three of the Galilean satellites, Ganymede, Callisto and Europa, as well as studies of other moons, the ring system, and irregular satellites.

The CIS115 is a CMOS Active Pixel Sensor from e2v technologies selected for the JANUS camera. It is fabricated using 0.18 μ m CMOS imaging sensor process, with an imaging area of 2000 × 1504 pixels, each 7 μ m square. A 4T pixel architecture allows for efficient correlated double sampling, improving the readout noise to better than 8 electrons rms, whilst the sensor is operated in a rolling shutter mode, sampling at up to 10 Mpixel/s at each of the four parallel outputs.A primary parameter to characterise for an imaging device is the relationship that converts the sensor's voltage output back to the corresponding number of electrons that were detected in a pixel, known as the Charge to Voltage Factor (CVF). In modern CMOS sensors with small feature sizes, the CVF is known to be non-linear with signal level, therefore a signal-dependent measurement of the CIS115's CVF has been undertaken and is presented here. The CVF is well modelled as a quadratic function leading to a measurement of the maximum charge handling capacity of the CIS115 to be 3.4 × 10⁴ electrons. If the CIS115's response is assumed linear, its CVF is 21.1 electrons per mV (1/47.5 μ V per electron).

The Spectrometer/Telescope for Imaging X-rays (STIX) is a remote sensing instrument on-board the ESA Solar Orbiter spacecraft. STIX is designated to the study of energetic phenomena in solar flares. A Fourier-imaging technique using tungsten grid collimators in front of CdTe pixel detectors is employed, covering the 4 to 150 keV energy range with a full-width-half maximum resolution around 1 keV at low energies.

Acrorad CdTe detectors of 1 mm thickness with a planar aluminum Schottky contact are used as basis for a subsequent patterning process into eight large pixels, four small pixels, and a guard ring. The patterning is done by means of microfabrication technologies. The area of the patterned sensor is 10×10 mm².

Test equipment has been developed for selecting the detectors with best performance prior to integration with the read-out system, and for qualification purposes. The set-up allows pixel-based dark current measurements at low temperatures. Pixel dark currents below 60 pA are needed to avoid excess noise in the read-out ASIC. The best pixels show dark currents below 10 pA at 300 V bias and −20 °C. Spectroscopic measurements with ¹³³Ba sources confirm the good performance.

This paper briefly explains the mission context of the CdTe detectors and then gives details of the production and testing procedures. Typical results are shown, with emphasis on performance degradation studies from displacement damage by proton irradiation. This is expected to be the dominant degradation mechanism for this application.

In the last decade, the Detector Development Group at the Technology Department of the Science and Technology Facilities Council (STFC), U.K., established a variety of fabrication and bonding techniques to build pixelated X-ray and γ-ray detector systems such as the spectroscopic X-ray imaging detector HEXITEC [1]. The fabrication and bonding of such devices comprises a range of processes including material surface preparation, photolithography, stencil printing, flip-chip and wire bonding of detectors to application-specific integrated circuits (ASIC). This paper presents interconnect and bonding techniques used in the fabrication chain for pixelated detectors assembled at STFC. For this purpose, detector dies (∼ 20× 20 mm²) of high quality, single crystal semiconductors, such as cadmium zinc telluride (CZT) are cut to the required thickness (up to 5mm). The die surfaces are lapped and polished to a mirror-finish and then individually processed by electroless gold deposition combined with photolithography to form 74× 74 arrays of 200 μ m ×  200 μ m pixels with 250 μ m pitch. Owing to a lack of availability of CZT wafers, lithography is commonly carried out on individual detector dies which represents a significant technical challenge as the edge of the pixel array and the surrounding guard band lies close to the physical edge of the crystal. Further, such detector dies are flip-chip bonded to readout ASIC using low-temperature curing silver-loaded epoxy so that the stress between the bonded detector die and the ASIC is minimized. In addition, this reduces crystalline modifications of the detector die that occur at temperature greater than 150\r{ }C and have adverse effects on the detector performance. To allow smaller pitch detectors to be bonded, STFC has also developed a compression cold-weld indium bump bonding technique utilising bumps formed by a photolithographic lift-off technique.

The Phase 1 upgrade of the Hadron Calorimeter (HCAL) in the Compact Muon Solenoid (CMS) detector at the Large Hadron Collider (LHC) will include two new generations (named QIE10 and QIE11) of the radiation-tolerant flash ADC chip known as the Charge Integrator and Encoder or QIE. The QIE integrates charge from a photo sensor over a 25 ns time period and encodes the result in a non-linear digital output while having a good sensitivity in both the higher and the lower energy values. The charge integrator has the advantage of analyzing fast signals coming from the calorimeters as long as the timing and pulse information is available. The calorimeters send fast, negative polarity signals, which the QIE integrates in its non-inverting input amplifier. The input analog signal enters the QIE chip through two points: signal and reference. The chip integrates the difference between these two values. This helps in getting rid of the incoming noise, which is effectively cancelled out in the difference. Over a period of about six months between September, 2013 and April, 2014 about 320 QIE10 and about 20 QIE11 chips were tested in Fermilab using a single-chip test stand where every individual chip was tested for its characteristic features using a clam-shell. The results of those tests performed on the QIE10 and QIE11 are summarized in this document.

With the increased brilliance of state-of-the-art Synchrotron radiation sources and the advent of Free Electron Lasers enabling revolutionary science on atomic length and time scales with EUV to X-ray photons comes an urgent need for suitable photon imaging detectors. Requirements include high frame rates, very large dynamic range, single-photon counting capability with low probability of false positives, and (multi)-megapixels.

PERCIVAL (``Pixelated Energy Resolving CMOS Imager, Versatile And Large'') is currently being developed by a collaboration of DESY, RAL, Elettra, DLS and Pohang to address this need for the soft X-ray regime. PERCIVAL is a monolithic active pixel sensor (MAPS), i.e. based on CMOS technology. It will be back-thinned to access its primary energy range of 250 eV to 1 keV with target efficiencies above 90%. According to its preliminary specifications, the roughly 10 × 10 cm<sup>2</sup>, 3.5k × 3.7k monolithic ``PERCIVAL13M'' sensor will operate at frame rates up to 120 Hz (commensurate with most FELs) and use multiple gains within its 27 μm pixels to measure 1 to ∼ 10⁵ (500 eV) simultaneously-arriving photons. A smaller ``PERCIVAL2M'' with ∼ 1.4k × 1.5k pixels is also planned. Currently, small-scale back-illuminated prototype systems (160 × 210 pixels of 25 μm pitch) are undergoing detailed testing with X-rays and optical photons. In March 2014, a prototype sensor was tested at 350 eV–2 keV at Elettra's TwinMic beamline. The data recorded include diffraction patterns at 350 eV and 400 eV, knife edge and sub-pixel pinhole illuminations, and comparisons of different pixel types. Another prototype chip will be submitted in fall 2014, first larger sensors could be in hand in late 2015.

This work has been done in order to study a new technology provided by X-FAB named xt018. It is an SOI (Silicon On Insulator) technology with a minimal gate length of 180 nm. Building blocks have been done to test the advantages and drawbacks of this technology compared to the one currently used (AMS SiGe 0.35 μm). These building blocks have been designed to fit in an existing experience housed by the CALICE collaboration: the read-out chip for the Electromagnetic CALorimeter (ECAL) of the foreseen International Linear Collider (ILC). Performances will be compared to those of the SKIROC2 chip designed by the OMEGA laboratory, trying to fit the same requirements. The chip is being manufactured and will be back for measurements in December, the displayed results are only simulation results and thus the conclusions concerning the performances of these building blocks are subject to change.

Advances in semiconductor technologies, enable the design of hybrid pixel detectors with ever smaller pixel sizes while maintaining good performance of analogue circuits. Along with the decrease in the size of pixels new, previously unaddressed phenomena are beginning to play an important role. One such phenomenon is the charge sharing effect, where the charge generated by a particle in the vicinity of the pixel's border is collected by two or more different detector electrodes and processed in part by two or more independent pixels. In systems operating in the single photon counting (SPC) mode which compares the amplitude of the recorded signal with a predetermined threshold, this may reduce or increase the number of photons counted. In systems which measure the amplitude of the signal recorded, this phenomenon can lead to incorrect results of the amplitude measurements. In order to investigate the effect of charge sharing, measurements were conducted using silicon pixel detectors with the thickness of 300 μ m and 1 mm, 100 μ m ×  100 μ m pixel size, connected to the PXD18k ASIC. The pixel array was scanned with 16 keV narrow pencil beam. The measurement setup and the results of the measurements are presented in the article.

The APEnet+ board delivers a point-to-point, low-latency, 3D torus network interface card. In this paper we describe the latest generation of APEnet NIC, APEnet v5, integrated in a PCIe Gen3 board based on a state-of-the-art, 28 nm Altera Stratix V FPGA. The NIC features a network architecture designed following the Remote DMA paradigm and tailored to tightly bind the computing power of modern GPUs to the communication fabric. For the APEnet v5 board we show characterizing figures as achieved bandwidth and BER obtained by exploiting new high performance ALTERA transceivers and PCIe Gen3 compliancy.

This work is concerned with the design and characterization of bandgap reference circuits capable of operating with a power supply of 1.2 V in view of applications to HL-LHC experiments. Due to the harsh environment foreseen for these devices, different solutions have been considered and implemented in a 65 nm CMOS technology. Together with a conventional structure which exploits bipolar devices, a smaller solution based on pn diodes and a version with MOS transistors biased in weak inversion region are included. This paper intends to describe and compare the features of the different circuits designed.

The ANDA (antiProton ANnihilation at DArmstadt) experiment will study the strong interaction in annihilation reactions between an antiproton beam and a stationary gas jet target. The detector will comprise different sub-detectors for tracking, particle identification and calorimetry. The Micro-Vertex Detector (MVD) as the innermost part of the tracking system will allow precise tracking and detection of secondary vertices.

For the readout of the double-sided silicon strip sensors a custom-made ASIC is being developed, employing the Time-over-Threshold (ToT) technique for digitization and utilize time-to-digital converters (TDC) to provide a high-precision time stamp of the hit. A custom-made Module Data Concentrator ASIC (MDC) will multiplex the data of all front-ends of one sensor towards the CERN-developed GBT chip set (GigaBit Transceiver). The MicroTCA-based MVD Multiplexer Board (MMB) at the off-detector site will receive and concentrate the data from the GBT links and transfer it to FPGA-based compute nodes for global event building.

Correlated charge collection phenomena in CCD sensors are presently of interest due to their potentially major implications in space and ground based astronomy missions. These effects may manifest as a signal dependent Point Spread Function (PSF), or as a nonlinearity in the Photon Transfer Curve (PTC). We present the theoretical background to a simple analytical model based on previously published solutions of Poisson's equation which aims to aid conceptual understanding of how various device parameters relate to the magnitude of correlated charge collection. We separate correlated charge collection into two components - firstly excess diffusion caused by increasing drift time as the electric field in the device decreases, which is isotropic, and secondly anisotropic pixel boundary shifting as the fringing field in the parallel transfer direction collapses. Equations are presented which can be solved numerically to give reasonable detail, or solved analytically using simplifying approximations.

The Pixel Detector of the ATLAS experiment has shown excellent performance during the whole Run-1 of LHC. Taking advantage of the long shutdown, the detector was extracted from the experiment and brought to surface, to equip it with new service quarter panels, to repair the modules and to ease installation of the Insertable B-Layer (IBL). The IBL is a fourth layer of pixel detectors, and has been installed in May 2014 between the existing Pixel Detector and a new smaller radius beam-pipe at a radius of 3.3 cm. To cope with the high radiation and pixel occupancy due to the proximity to the interaction point, a new read-out chip and two different silicon sensor technologies (planar and 3D) have been developed. Furthermore, the physics performance will be improved through the reduction of pixel size while, targeting for a low material budget, a new mechanical support using light weight staves and CO₂ based cooling system have been adopted. An overview of the refurbishing of the Pixel Detector and the IBL project as well as the experience in its construction will be presented, focusing on adopted technologies, module and stave production, qualification of assembly procedure, integration of staves around the beam pipe and commissioning of the detector.