Table of contents

An adjustment of the electron and photon beams angular and transverse phase-space characteristics along the undulator line and the resonant interaction of the electron beam with co-propagating radiation are of basic conditions to drive the SASE-FEL process. In the real facility the SASE-FEL process can degrade due to electron beam orbit distortion caused by quadrupole misalignments in undulator section. Both those issues are in dependence of the focusing lattice arrangement in undulator section. In this paper the comparative study of the SASE-FEL process for conventional FODO focusing lattices, the undulator section arrangement with central focusing lattice and the FEL performance without external focusing system are presented. The impact of the quadrupole misalignments on the radiation saturation length and power for different focusing systems is analyzed. The numerical simulations for European XFEL project are given.

Charge collection measurements with silicon detectors with implanted n-type readout strips in p-type silicon bulk (n⁺-p) are presented. Detectors were irradiated with 191 MeV pions at the Paul Scherrer Institute (PSI) in Villigen in Switzerland. Signals induced by electrons from ⁹⁰Sr source were measured with SCT128 chip. Collected charge and detector current were measured after several annealing steps summing up to over 10000 minutes at 60°C. It was observed that irradiation of these detectors with pions results in only ∼ 30% of the increase of V_fd seen after irradiation with neutrons to the same NIEL equivalent fluence. Charge multiplication effects in pion irradiated detectors were seen only after long accelerated annealing time. Both effects are consistent with smaller space-charge introduction rates after irradiation with charged hadrons, characteristic for oxygenated detector material. It was confirmed that, at sufficient bias voltage, reverse annealing after pion irradiation does not represent a problem for application of these detectors in trackers at upgraded LHC.

Since several years, the irradiation facility for beta radiation, the Beta Secondary Standard BSS 2 developed at PTB, has been in worldwide use for the performance of irradiations with calibrated beta sources. Due to recent developments in eye tumor therapy, in eye lens dosimetry, and in soft- and hardware technology, several extensions have been added to the BSS 2.

These extensions are described in this paper: 1. The possibility of using a ¹⁰⁶Ru/¹⁰⁶Rh beta source was added as this radionuclide is often used in tumor therapy. 2. The (small) contribution due to photon radiation was included in the dose (rate) reported by the BSS 2, as this was missing in the past. 3. The quantity personal dose equivalent at a depth of 3 mm, H_p(3), was implemented due to recent findings on the radio sensitivity of the eye lens regarding cataract induction and the subsequent lowering of the dose limit from 150 mSv down to 20 mSv per year; 4. The correction for ambient conditions (air temperature, pressure, and relative humidity) was improved in order to adequately handle the quantity H_p(3) and in order to extend the range of use beyond 25°C. 5. A checksum test was added to the software to secure the calibration data against (un)intended changes. 6. The connection of the PC and the BSS 2 has been changed to a network interface (TCP/IP) in order to be able to use up-to-date computers not containing a parallel and a serial port. 7. A rod phantom was added in order to make sure the mechanical set-up is of high quality.

All these extensions have been implemented in the PTB's BSS 2 model. The routine implementation of extension 1 is still under investigation by the manufacturer. The commercially available BSS 2 will contain extensions 2 to 6 starting approximately in 2012, while extension 7 has already been incorporated since 2011. Extensions 2 to 4 will also be available for old BSS 2 versions via a software update, starting approximately at the beginning of 2012. Extension 6 will be available via hardware change by the manufacturer.

The energy dependent light output of liquid scintillators used in the Double Chooz experiment was measured for electrons up to 140 keV energy. A new Compton scattering coincidence apparatus was built for this purpose. A detailed study on possible systematic errors was made. We report the experimental results of our investigations and tested them for concordance with the predictions of various models. All models reasonably fit the experimental data after adjusting the respective free parameters. The results were also used to tune the Geant4-based Monte Carlo simulation software which is used in Double Chooz. The experimental data can be described by the simulation choosing an effective value for the Birks parameter.

The European XFEL, currently under construction, will produce a coherent X-ray pulse every 222 ns in pulse trains of up to 2700 pulses. In conjunction with the fast 2D area detectors currently under development, it will be possible to perform X-ray Photon Correlation Spectroscopy (XPCS) experiments on sub-microsecond timescales with non-ergodic systems. A case study for the Adaptive Gain Integrating Pixel Detector (AGIPD) at the European XFEL employing the intensity autocorrelation technique was performed using the detector simulation tool HORUS. As optimum results from XPCS experiments are obtained when the pixel size approximates the (small) speckle size, the presented study compares the AGIPD (pixel size of (200 μm)²) to a possible apertured version of the detector and to a hypothetical system with (100 μm)² pixel size and investigates the influence of intensity fluctuations and incoherent noise on the quality of the acquired data. The intuitive conclusion that aperturing is not beneficial as data is 'thrown away' was proven to be correct for low intensities. For intensities larger than approximately 1 photon per (100 μm)² aperturing was found to be beneficial, as charge sharing effects were excluded by it. It was shown that for the investigated case (100 μm)² pixels produced significantly better results than (200 μm)² pixels when the average intensity exceeded approximately 0.05 photons per (100 μm)². Although the systems were quite different in design they varied in the signal to noise ratio only by a factor of 2–3, and even less in the relative error of the extracted correlation constants. However the dependence on intensity showed distinctively different features for the different systems.

ZE3RA is the software package responsible for processing the raw data from the ZEPLIN-III dark matter experiment and its reduction into a set of parameters used in all subsequent analyses. The detector is a liquid xenon time projection chamber with scintillation and electroluminescence signals read out by an array of 31 photomultipliers. The dual range 62-channel data stream is optimised for the detection of scintillation pulses down to a single photoelectron and of ionisation signals as small as those produced by single electrons. We discuss in particular several strategies related to data filtering, pulse finding and pulse clustering which are tuned using calibration data to recover the best electron/nuclear recoil discrimination near the detection threshold, where most dark matter elastic scattering signatures are expected. The software was designed assuming only minimal knowledge of the physics underlying the detection principle, allowing an unbiased analysis of the experimental results and easy extension to other detectors with similar requirements.

This paper reports on a 6 kV modulator built and installed at Fermilab to drive the electron gun anode for the Tevatron Electron Lens (TEL). The TEL was built with the intention of shifting the individual (anti)proton bunch tunes to even out the tune spread among all 36 bunches with the desire of improving Tevatron integrated luminosity. This modulator is essentially a 6 kV arbitrary waveform generator that enables the TEL to define the electron beam intensity on a bunch-by-bunch basis. A voltage waveform is constructed having a 7 μs duration that corresponds to the tune shift requirements of a 12-bunch (anti)proton beam pulse train. This waveform is played out for any one or all three bunch trains in the Tevatron. The programmed waveform voltages transition to different levels at time intervals corresponding to the 395 ns bunch spacing. Thus, complex voltage waveforms can be played out at a sustained rate of 143 kHz over the full 6 kV output range. This paper describes the novel design of the inductive adder topology employing five transformers. It describes the design aspects that minimize switching losses for this multi-kilovolt, high repetition rate and high duty factor application.

Measurements of the jet energy calibration and transverse momentum resolution in CMS are presented, performed with a data sample collected in proton-proton collisions at a centre-of-mass energy of 7TeV, corresponding to an integrated luminosity of 36pb⁻¹. The transverse momentum balance in dijet and γ/Z+jets events is used to measure the jet energy response in the CMS detector, as well as the transverse momentum resolution. The results are presented for three different methods to reconstruct jets: a calorimeter-based approach, the ``Jet-Plus-Track'' approach, which improves the measurement of calorimeter jets by exploiting the associated tracks, and the ``Particle Flow'' approach, which attempts to reconstruct individually each particle in the event, prior to the jet clustering, based on information from all relevant subdetectors.

We present a new design of a slow neutron detector, based on silicon detectors with innovative materials acting as conversion layers, plus preliminary results that will be the basis for a more complete study in the near future. The sensitive element of this detector is a Schottky barrier silicon diode covered with o-carborane, a novel boron-based converter material that detects neutrons by means of the ¹⁰B(n,α)⁷Li reaction. This sensor has been simulated with the MCNPX Monte-Carlo software in order to find the optimal converter layer thickness that maximizes the neutron detection efficiency. The simulated maximum efficiency is 2.7% for a 20 μm converter layer of the o-carborane fabricated with pure ¹⁰B and of 0.5% for the same compound but made with natural boron material. Moreover, the performance of test devices has been investigated by means of an ²⁴¹AmBe neutron source and the results have been analyzed with the help of GEANT4 simulations.

The development at CERN of low noise DC-DC converters for the powering of front-end systems enables the implementation of efficient powering schemes for the physics experiments at the HL-LHC. Recent tests made on the ATLAS short strip tracker modules confirm the full electromagnetic compatibility of the DC-DC converter prototypes with front-end detectors. The integration of the converters in the trackers front-ends needs to address also the material budget constraints. The impact of the DC-DC converters onto the material budget of the ATLAS tracker modules is discussed and mass reduction techniques are explored, leading to a compromise between electromagnetic compatibility and mass. Low mass shield implementations and Aluminum core inductors are proposed. Also, the impact on emitted noise due to a size reduction of critical components is discussed. Finally, material reduction techniques are discussed at the board layout and manufacturing levels.

X-ray transmission radiograms of Aluminum alloy contain relatively low contrast features induced by variations of the material chemical composition. Generally, these variations are strongly connected with grains of the metal, where these differ from each to other. Although grains of the studied material have typically dimensions of tens of micrometers only, the material variations can enable the observation of geometry and orientations of grains in the specimen volume employing advanced X-ray micro tomographic method. Analysis of such tiny structures requires high dynamic range of acquired radiograms with high signal to noise ratio and appropriate geometrical magnification. These requirements can be fully satisfied by using the pixelated single photon counting device Medipix, a precise micro-tomographic setup and appropriate data processing. Results will be demonstrated with an Aluminum alloy bar specimen.

The feasibility of using PILATUS single-X-ray-photon counting detectors for long-wavelength macromolecular crystallography was investigated by carrying out a series of experiments at Diamond Light Source. A water-cooled PILATUS 100k detector was tested in vacuum with monochromatic 3 keV X-rays on the Diamond test beamline B16. Effects of detector cooling on noise performance, energy calibration and threshold trimming were investigated. When detecting 3 keV X-rays, the electronic noise of the analogue output of pixel preamplifiers forces the threshold to be set at a higher level than the 50% energy level recommended to minimize charge-sharing effects. The influence of threshold settings at low X-ray energy was studied by characterizing the detector response to a collimated beam of 3 keV X-rays scanned across several pixels. The relationship between maximum count rate and minimum energy threshold was investigated separately for various detector gain settings.

The new method to correct a parallax error and the loss of coincidence counts caused by the gap between modules was developed for a small animal PET scanner. We proposed the TraPET scanner composed of 6 dual-layer phoswich detector modules. Each detector module consists of a 5.0 mm-thick trapezoidal-shaped monolithic LSO crystal and a 23 x 23 array of GSO crystal. The layer of interaction is identified by the pulse shape discrimination method. One detector module was built and the algorithm for layer identification was optimized. The dual-layer crystals were optically coupled to a Hamamatsu H8500 position-sensitive PMT and a resistive charge divider was used to multiplex 64-channel anode outputs into 4-channel position signals. The 4 signals have been sampled continuously by 14-bit ADC at a sampling rate of 105 MHz and the pulse shape discrimination algorithm was achieved through FPGA programming. The detector module was irradiated with a Na-22 point source from the side of the crystals to obtain flood images of each layer and two layers were clearly identified, thus verifying the DOI capability. The TraPET detector proved to be a reliable design for correcting the parallax error and improving the sensitivity simultaneously in the small animal PET.

Around 2016, the pixel detector of the CMS experiment will be upgraded. The amount of current that has to be provided to the front-end electronics is expected to increase by a factor of two. Since the space available for cables is limited, this would imply unacceptable power losses in the currently installed supply cables. Therefore it is foreseen to place DC-DC converters close to the front-end electronics, allowing the provision of power at higher voltages, thereby facilitating the supply of the required currents with the present cable plant. This conference report introduces the foreseen powering scheme of the pixel upgrade. For the first time, system tests have been conducted with pixel barrel sensor modules, radiation tolerant DC-DC converters and the full power supply chain of the pixel detector. In addition, studies of the stability of different powering schemes under various conditions are summarized. In particular the impact of large and fast load variations, which are related to the bunch structure of the LHC beam, has been studied.

The double beta decay (ββ) is very challenging subject of today's physics. It can be used as a powerful tool to test neutrino properties (e.g. Dirac or Majorana type of neutrino) and lepton number conservation. However, these experiments demand very high sensitivity and very strong background reduction. We have been performing intensive R&D towards the use of pixel detector Timepix in the ββ decay experiments. The Timepix device, operated in Time Over Threshold (TOT) mode, provides spectroscopic capabilities in each individual pixel. The main advantage of such detector is its ability to identify and reject background signals (e.g. tracks made by electrons, alpha particles, muons). It would efficiently recognize the signal of ββ decay processes. Two pixel detectors, Si (pixel size 55 × 55 μm²) and CdTe (pixel size 110 × 110 μm²), were tested in the surface laboratory as well as in the underground laboratories, from the point of view of intrinsic background and the results are presented. Low background materials for construction of the setup were also identified. The first prototype of Silicon Pixel Telescope (SPT) has been tested and future improvements are also presented.

The Train Builder is an Advanced Telecom ATCA based custom data acquisition system designed to provide a common readout system for the large 2D Mega-pixel detectors presently under construction for the European-XFEL facility in Hamburg. Each detector outputs 10 GBytes/sec of raw data over multiple 10 Gbps SFP+ optical links. The Train Builder DAQ system will merge detector link image fragments from up to 512 X-ray pulses in each pulse train and send the complete detector ``movies'' of images to a farm of PCs. The image building will be carried out using FPGAs with analogue Crosspoint switches operating in a barrel shift mode. The Train Builder data links will operate with 10G UDP&TCP/IP based protocols implemented in FPGA logic.

Conventional readout systems exist in many variants since the usual approach is to build readout electronics for one given type of detector. The Scalable Readout System (SRS) developed within the RD51 collaboration relaxes this situation considerably by providing a choice of frontends which are connected over a customizable interface to a common SRS DAQ architecture. This allows sharing development and production costs among a large base of users as well as support from a wide base of developers. The Front-end Concentrator card (FEC), a RD51 common project between CERN and the NEXT Collaboration, is a reconfigurable interface between the SRS online system and a wide range of frontends. This is accomplished by using application-specific adapter cards between the FEC and the frontends. The ensemble (FEC and adapter card are edge mounted) forms a 6U × 220 mm Eurocard combo that fits on a 19'' subchassis. Adapter cards exist already for the first applications and more are in development.

Group 2–6 compounds (e.g., CdTe, CdS, CdSe) are utilized as photoconductors at the bulk level but manufactured as phosphors at the nano-level. Each of these uses has strengths and weaknesses. Here we attempted to fuse the two uses to maximize the strengths of each by using only one compound. We invented an X-ray detector that could function at two different levels -as a photoconductor in the bulk state and as a phosphor at the nano-scale- by hybridizing two different kinds of layer from one compound. This system operates as follows. First, an X-ray is converted to light on the luminescence layer, after which the light is received on the photoconductor layer. This light has the exact wavelength range required on the photoconductor. The quantum size effect refers to the impact of changes in the electronic energy level density according to the size of the crystal in a nano-particle on its optical and electrical characteristics. On account of this effect, two different kinds of layer from one compound can be used by regulating its size. Thus, by controlling the particle size and changing the emission wavelength, the most appropriate absorption wavelength for a photoconductor in the bulk state can be emitted from the nano-phosphor. The conversion efficiency in the hybrid structure is apparently superior to that in the bulk-state single layer. In conclusion, the electrical and optical characteristics of the proposed hybrid structure are superior to those of a conventional structure. These findings confirm the feasibility of a hybrid structure based on the quantum size effect.

The Versatile Transceiver (VTRx) will be deployed on detectors that will be operated at the upgraded HL-LHC where the instantaneous luminosity will be increased by a factor of 5–10 with respect to the nominal LHC. All components housed at the front-ends must thus be immune to single-event-upsets (SEUs) to a level compatible with the correct operation of the detector systems. We report the results of SEU testing of the full VTRx in a proton beam-line.

The architecture and characterisation of the NA62 GigaTracker End of Column Demonstrator Hybrid Pixel Detector (HPD) are presented. This detector must perform time stamping to 200 ps (RMS) or better, provide 300 μm pitch position information and operate with a dead time of 1% or less for 800 MHz−1 GHz beam rate. The demonstrator HPD Assembly comprises a readout chip with a test column of 45 pixels, alongside other test structures, bump bonded to a p-in-n detector 200 μm in thickness. Validation of the performance of the HPD and the time-over-threshold timewalk compensation mechanism with both beam particles and a high precision laser system was performed and is presented. Confirmation of better than the required time stamping precision has been demonstrated and subsequent work on the design of the full-scale ASIC, dubbed TDCPix, is underway. An overview of the TDCPix architecure is given.

A prototype of a position sensitive photo-detector with 5.6 × 5.6 cm² detection area readout with 64 Hamamatsu MPPCs (S10931-100P) with 3 × 3 mm² active area each has been built and tested. The photo-sensors are arranged in a 8 × 8 array with a quadratic mirror light guide on top. The module is currently readout by in-house developed preamplifier boards but employing existing ASIC chips optimized for SiPM readout is also planned. Such a device is one of the candidates to be used for photon detection in the PANDA DIRC detectors.

A significant advantage of high granularity and highly sensitive semiconductor pixel detectors is the possibility to directly observe single tracks of charged particles. In many cases, however, these particles are accompanied with unwanted background radiation overlapping traces of interest. The detection selectivity can be increased using a triggering approach usually provided by an external trigger from other detecting devices such as ionization chambers, scintillating or semiconductor detectors. A self-trigger from the same sensor would be highly desirable. Unfortunately the Medipix/Timepix devices are not equipped with such self-trigger feature. A solution which is presented in this contribution makes use of the analog signal taken from the common electrode of the pixelated sensor. This signal, called back-side-pulse, is amplified by a custom made charge sensitive preamplifier which, after shaping, can be used as fast trigger and as independent spectroscopic signal. The stability and energy resolution of this analog signal is, however, strongly affected by electromagnetic noise interference from the digital read-out chip and its interface. In this article we present the solution based on the construction of a hardware galvanic shielded extender which isolates and effectively suppresses such noise interference. The result enables selective self-triggering according to the deposited energy of the detected particle. The technique and operation of the prototype are demonstrated on measurements with heavy charged particles from radioactive α-sources ²⁴¹Am and ²³⁹Pu.

The electrical properties of hadron irradiated silicon detectors change over several years after irradiation. This annealing process has a strong dependence on temperature and it can be accelerated or decelerated by lowering or elevating the temperature at which the sensors are kept. This is exploited to investigate the long term behaviours of irradiated silicon detectors that are, or will be, installed in the experiment at the current and upgraded LHC at CERN. Elevated temperatures (up to 80°C) are used to accelerate the effect of annealing to study the expected changes of the sensor performances over several years of room temperature equivalent time. Low temperatures are applied to the sensors also when not operated to suppress undesired effects of annealing. The acceleration factors with respect to nominal room temperature (RT = 20°C) have been established monitoring the changes of the capacitance-voltage characteristics (CV) with time at various temperatures. In the experiments, the maximum high temperature envisaged out of operation cannot exceed much 20°C. It is important to measure the changes of the relevant parameters (charge collection reverse current, noise) at this temperature to verify the annealing behaviours in realistic conditions for planning the operation scenario (i.e. bias voltage and temperature during and outside operation) of the silicon sensors. We show here the study of room temperature annealing of the charge collection, reverse current and noise of silicon microstrip detectors after two doses of hadron irradiation (2 and 10 × 10¹⁵ n_eq cm⁻²) . These doses are chosen to represent the expected levels in the future upgrade of the LHC at CERN (High Luminosity LHC, HL-LHC) for the microstrip and pixel layers. The measurements show that a suitable choice of annealing time at 20°C can partially recover the degraded charge collection and reduce the reverse current after a given dose of hadron irradiation.

The Super Advanced X-ray Emission Spectrometer (SAXES) at the Advanced Resonant Scattering (ADRESS) beamline of the Swiss Light Source is a high-resolution X-ray spectrometer used as an end station for Resonant Inelastic X-ray Scattering from 400 eV to 1600 eV. Through the dispersion of photons across a CCD, the energy of scattered photons may be determined by their detected spatial position. The limiting factor of the energy resolution is currently the spatial resolution achieved with the CCD, reported at 24 μm FWHM. For this energy range the electron clouds are formed by interactions in the `field free' region of the back-illuminated CCD. These clouds diffuse in all directions whilst being attracted to the electrodes, leading to events that are made up of signals in multiple pixels. The spreading of the charge allows centroiding techniques to be used to improve the CCD spatial resolution and therefore improve the energy resolution of SAXES. The PolLux microscopy beamline at the SLS produces an X-ray beam with a diameter of 20 nm. The images produced from scanning the narrow beam across CCD pixels (13.5 × 13.5 μm²) can aid in the production of event recognition algorithms, allowing the matching of event profiles to photon interactions in a specific region of a pixel. Through the use of this information software analysis can be refined with the aim of improving the energy resolution.

In radiology, image quality excellence is a balance between system performance and patient dose, hence x-ray systems must be designed to ensure the maximum image quality is obtained for the lowest consistent dose. The concept of detective quantum efficiency (DQE) is widely used to quantify, understand, measure, and predict the performance of x-ray detectors and imaging systems. Cascaded linear-systems theory can be used to estimate DQE based on the system design parameters and this theoretical DQE can be utilized for determining the impact of various physical processes, such as secondary quantum sinks, noise aliasing, reabsorption noise, and others. However, the prediction of DQE usually requires tremendous efforts to determine each parameter consisting of the cascaded linear-systems model. In this paper, practical DQE formalisms assessing both the photoconductor- and scintillator-based flat-panel detectors under quantum-noise-limited operation are described. The developed formalisms are experimentally validated and discussed for their limits. The formalisms described in this paper would be helpful for the rapid prediction of the DQE performances of developing systems as well as the optimal design of systems.

We study the influence of active edges on the response of edge pixels by comparing simulations of the electrostatic-potential distribution to position-defined measurements on the energy deposition. A laser setup was used to measure the edge-pixel response function and shows the sensitive edge is only about 2 μm from the physical edge. 3D reconstruction of tracks from high-energy pions and muons, produced at the SPS H6 test beam facility at CERN, enabled to relate the energy deposition at edge pixels to the particle's interaction depth. A clear correlation is observed between the simulated electric-field distortion and the reconstructed interaction-depth dependent effective size.

The next generation of hybrid pixel detectors in particle physics experiments require reduced material budget, increased interconnection density and, ideally, they should be tileable to cover large areas seamlessly. These criteria cannot be fulfilled with present day interconnection techniques. As a result the particle physics community has recently put in a lot of effort to investigate and evaluate a variety of novel interconnection technologies. This paper focuses on describing a recently launched Through Silicon Via process development project with CEA-LETI. The project aims to use Medipix3 wafers and an existing ``via last'' TSV process made available by CEA-LETI to demonstrate the feasibility of TSVs on functional detector chips. The status of the project, TSV design and future plans are presented.

In this paper we describe the optimization of transmission X-ray targets by Monte-Carlo simulation for a laboratory X-ray microscopy setup. We identified two optimal target layer thicknesses (0.1 μm and 0.7 μm) for a high-resolution target and a high-flux target. Measurements show a decrease in focal spot size by one third or an increase in X-ray flux by a factor of three compared to those of a standard micro-focus target. Focal spot sizes down to 154 nm and 260 nm are achievable with the optimized targets. Simulation results for the X-ray flux match well to the experimental results, whereas the results for the focal spot sizes still show discrepancies attributed to the simplified simulation setup.

A front end ASIC has been designed to equip the \textmu TPC prototype developed for the MIMAC project, which requires 3D reconstruction of low energy particle tracks in order to perform directional detection of galactic Dark Matter. Each ASIC is able to monitor 64 strips of pixels and provides the "Time Over Threshold" information for each of those. These 64 digital informations, sampled at a rate of 50 MHz, can be transferred at 400 MHz by eight LVDS serial links. Eight ASIC were validated on a 2 × 256 strips of pixels prototype.

The PANDA experiment at the future Facility for Antiproton and Ion Research (FAIR) at GSI, Darmstadt, aims at studying the strong interacting matter by precision spectroscopy. A detector system with excellent particle identification over a large range of solid angle and momentum is therefore mandatory. Charged hadron identification in the barrel region will be performed by a compact ring imaging Cherenkov detector based on the DIRC principle (Detection of Internally Reflected Cherenkov light), designed to separate pions from kaons with at least 3 standard deviations in the momentum range from 0.5 GeV/c to 3.5 GeV/c. We present details of the simulation of the PANDA Barrel DIRC and a study of the detector performance using a fast reconstruction algorithm to determine the single photon Cherenkov angle resolution and photon yield for several design options.

In ion beam therapy the finite range of the ion beams in tissue and the presence of the Bragg-peak are exploited. Unpredictable changes in the patient`s condition can alter the range of the ion beam in the body. Therefore it is desired to verify the actual ion range during the treatment, preferably in a non-invasive way. Positron emission tomography (PET) has been used successfully to monitor the applied dose distributions. This method however suffers from limited applicability and low detection efficiency. In order to increase the detection efficiency and to decrease the uncertainties, in this study we investigate the possibility to measure secondary charged particles emerging from the patient during irradiation.

An initial experimental study to register the particle radiation coming out of a patient phantom during the therapy was performed at the Heidelberg Ion Beam Therapy Center (HIT) in Germany. A static narrowly-focused beam of carbon ions was directed into a head phantom. The emerging secondary radiation was measured with the position-sensitive Timepix detector outside of the phantom. The detector, developed by the Medipix Collaboration, consists of a silicon sensor bump bonded to a pixelated readout chip (256 × 256 pixels with 55 μm pitch). Together with the USB-based readout interface, Timepix can operate as an active nuclear emulsion registering single particles online with 2D-track visualization.

In this contribution we measured the signal behind the head phantom and investigated its dependence on the beam energy (corresponding to beam range in water 2–30 cm). Furthermore, the response was measured at four angles between 0 and 90 degrees. At all investigated energies some signal was registered. Its pattern corresponds to ions. Differences in the total amount of signal for different beam energies were observed. The time-structure of the signal is correlated with that of the incoming beam, showing that we register products of prompt processes. Such measurements are less likely to be influenced by biological washout processes than the signal registered by the PET technique, coming from decays of beam-induced radioactive nuclei.

This work demonstrates that the Timepix detector is able to register ions emerging from the patient during the treatment by carbon ion beams. In future work it will be investigated which information about the incoming beam can be gained from the analysis of the measured data.

The European X-ray Free Electron Laser (XFEL) will deliver 30,000 fully coherent, high brilliance X-ray pulses per second each with a duration below 100 fs. This will allow the recording of diffraction patterns of single complex molecules and the study of ultra-fast processes. Silicon pixel sensors will be used to record the diffraction images. In 3 years of operation the sensors will be exposed to doses of up to 1 GGy of 12 keV X-rays. At this X-ray energy no bulk damage in silicon is expected. However fixed oxide charges in the insulating layer covering the silicon and interface traps at the Si-SiO₂ interface will be introduced by the irradiation and build up over time.

We have investigated the microscopic defects in test structures and the macroscopic electrical properties of segmented detectors as a function of the X-ray dose. From the test structures we determine the oxide charge density and the densities of interface traps as a function of dose. We find that both saturate (and even decrease) for doses between 10 and 100 MGy. For segmented sensors the defects introduced by the X-rays increase the full depletion voltage, the surface leakage current and the inter-pixel capacitance. We observe that an electron accumulation layer forms at the Si-SiO₂ interface. Its width increases with dose and decreases with applied bias voltage. Using TCAD simulations with the dose dependent parameters obtained from the test structures, we are able to reproduce the observed results. This allows us to optimize the sensor design for the XFEL requirements.

In addition the Si-SiO₂ interface region has been studied with time resolved signals induced by sub-nanosecond 660 nm laser light, which has a penetration of about 3 μm in silicon. Depending on the biasing history, humidity and irradiation dose, losses of either electrons or holes or no charge losses are observed. The relevance of these results for the sensor stability and performance is under investigation.

The single photon counting pixel detector Medipix2 is a powerful tool for energy resolved X-ray imaging. It allows the energies of incoming X-rays to be discriminated by setting an energy threshold common to all pixels. As the parameters of individual pixels vary, each pixel further contains a 3-bit digital-to-analogue converter (DAC) adjustment. Values of these DACs are traditionally determined by finding the noise floor in each pixel. Our approach is based on a polychromatic X-ray beam attenuation measurement. An attenuation curve is measured using varying thickness of aluminium foil. The attenuation curve is fitted in each pixel with a function calculating the detected signal. Free parameters of the fit are the beam intensity and the energy threshold. The measurement is done twice, with the threshold adjustment set to minimum resp. maximum value in all pixels. The result is a calibration of the adjustment DACs, allowing the value of the adjustment DAC in each pixel to be found such that the dispersion of energy thresholds between pixels is minimized. It is a fast and simple to use method that does not require modification of the imaging setup. It will be shown that it reduces the dispersion of threshold values by up to 40% compared to the noise-floor based technique of equalization.

Over the last decades the traditional photographic films used in radiology are being replaced by digital X-ray imaging sensors in many applications. The main advantages of these systems are their detection efficiency of image acquisition and the ability to directly digitally transfer and enhance obtained images. In this paper we characterize and evaluate the X-ray imaging performance of a YAG:Ce single crystal scintillator. The scintillator converts X-rays into visible light that is collected by an optical camera. The camera uses a CCD sensor with the size of 36x24 mm² and with 4050 x 2630 pixels of 9x9 μm² pitch, and is equipped with a macro objective. The semiconductor pixel detector Medipix2 was used for the evaluation of the imaging capabilities of this imaging system. The imaging capability is evaluated in terms of several basic characteristics: spatial resolution, edge response function, signal to noise ratio and contrast to noise ratio. A microfocus X-ray tube was used for high spatial resolution measurements in order to minimize the influence of the X-ray tube spot size. Measurements were done using an edge phantom, step wedge phantom and low contrast fibres. The corresponding measurements for all phantoms were done under identical conditions in order to assure comparability. The results measured by the CCD camera demonstrate the possibilities of sensitive X-ray radiography imaging with high spatial resolution.

The possibility to increase the radiation hardness of Cd_0.9Zn_0.1Te crystal using pulsed Nd:YAG laser radiation was shown. Estimation of the crystalline lattice defects before and after irradiation by γ-ray using photoluminescence method in the experiments was applied. Experimental results showed the increase of the radiation hardness of CdZnTe crystal after irradiation by the laser at intensity 1.20–1.80 MW/cm².

The Medipix3 photon counting readout chip has a range of features — small pixel size, high readout rate and inter-pixel communication — which make it attractive for X-ray scattering and imaging at synchrotrons. DESY have produced a prototype large-area detector module that can carry a 6 by 2 array of Medipix3 chips (1536 by 512 pixels), which can be used with a single large silicon sensor (85mm by 28mm) or two ``hexa'' high-Z sensors. The detector head is designed to be tilable and compatible with low temperatures, and will allow high speed parallel readout of the Medipix3 chips. It consists of a ceramic board, on which the sensor assembly is mounted, and a secondary board for signal routing and voltage regulators. A prototype DAQ board using USB2 readout has also been produced. A ``quad'' Medipix3 sensor assembly has been mounted on the detector head, and successfully configured and read out by the DAQ board. Development has begun on a high-speed readout board, and large-area silicon assemblies are in production.

The basic rationale for radiation therapy using ion-beams is its high local precision of dose deposition. Therefore accurate patient positioning prior to and during beam application is a crucial part of the therapy. The current standard position verification procedure uses X-ray based imaging before each beam application. The patient is assumed to remain in his position throughout irradiation. Currently there is no monitoring of the patient position or organ movement during treatment. The aim of this study is to investigate the possibility of verifying the position of a fiducial marker during therapy using ion radiography. Some modern ion therapy facilities like the Heidelberg Ion-Beam Therapy Center (HIT), where our measurements were carried out, use scanning pencil beams to apply dose. Exploiting them for imaging allows to solely irradiate regions of interest in the patient's body, e.g. tissue containing medical markers. The advantage of this technique is that it can be performed quickly in turn with therapeutic beam application and irradiates only very little tissue. For our measurements we used conventional medical metal markers embedded in phantom material mimicking body tissue. To image the residual beam we use a Perkin Elmer RID256-L flat panel detector. In an idealized setup the marker contrast was measured to be as high as 60%, which was reduced by a factor of 2–2.5 when the marker was placed at distances to the detector in the phantom material larger than 10 cm. It was shown that applying 2⋅10⁵ carbon ions suffices to make the markers' position visible in a setup of realistic material thickness and marker depth. While the dose is comparable to X-ray imaging, the irradiated volume and, consequently, also the integral dose is considerably reduced. However, in realistic geometries there are large particle range differences in lateral direction yielding steep signal gradients in the radiography. Thus, the useful image area with unambiguous signal information is largely reduced.

X-ray microradiography was employed to quantify the strains in loaded human trabecula. Samples of isolated trabeculae from human proximal femur were extracted and glued in a loading machine specially designed and manufactured for testing small specimens. The samples were then tested in tension and three-point bending until complete fracture of the specimen occured. To assess the deformation in the very small samples (thickness 100μm, length 1—2mm) a real-time microradiography in conjunction with digital image correlation (DIC) has been employed. Loaded samples were irradiated continuously by X-rays (Hamamatsu L8601-01 with 5μm spot) during the test. Radiographs were acquired using 0.25s exposure time with hybrid single-photon counting silicon pixel detector Medipix2. The distance between the source and detector was kept small to ensure radiographs of good quality for such a short exposure time. Design of the experimental loading device enables for precise control of the applied displacement which is important for the post-yield behavior assessment of trabeculae. Large dynamic range, high sensitivity and high contrast of the Medipix2 enables measuring even very small strains with DIC. Tested experimental setup enables to combine micromechanical testing of the basic building block of trabecular bone with time-lapse X-ray radiography to measure the strains and to assess the mechanical properties of single human trabecula as well as to capture the softening curve with sufficient precision.

Next generation light sources are revolutionizing x-ray science by delivering ultra-intense, hard x-ray pulses many orders of magnitude brighter and shorter in duration than previously achievable. Maximizing the scientific potential of these light sources requires the development of suitable detectors. Experiments such as coherent x-ray imaging of single particles require detectors that can record extremely high instantaneous flux rates produced by femtosecond x-ray pulses (i.e. thousands of photons incident on a single pixel of an area detector in a few femtoseconds) while also being able to accurately distinguish single photon events so that many thousands of frames of data can be used to reconstruct extremely low flux information (e.g. less than 1/1000 photons per pixel per frame). This paper presents data from an integrating pixel array detector (PAD) possessing the ability to record high- and low-flux x-ray data at an X-ray Free Electron Laser (XFEL). Methods are presented to process extremely low-flux data (less than 1/10000 8-keV x-rays per pixel per frame) to accurately recover diffraction patterns from thousands of frames. The data were collected using a detector developed by Cornell for the Linac Coherent Light Source (LCLS) at SLAC National Lab. A copy of this detector was delivered to SLAC in the middle of 2008. The ASIC developed for this detector was used by SLAC as the basis for the CS-PAD (Cornell SLAC-PAD) being used on the Coherent X-ray Imaging beamline at the LCLS. These methods extend beyond XFEL applications because they allow for the suppression of dark accumulation noise which typically limits the low-flux capability of integrating detectors on conventional x-ray sources.

Microradiography is an imaging technique using X-rays in the study of internal structures of objects. This rapid and convenient imaging tool is based on differential X-ray attenuation by various tissues and structures within the biological sample. The non-absorbed radiation is detected with a suitable detector and creates a radiographic image. In order to detect the differential properties of X-rays passing through structures sample with different compositions, an adequate high-quality imaging detector is needed. We describe the recently developed radiographic apparatus, equipped with Timepix semiconductor pixel detector. The detector is used as an imager that counts individual photons of ionizing radiation, emitted by an X-ray tube FeinFocus with tungsten, copper or molybdenum anode. Thanks to the wide dynamic range, time over threshold mode — counter is used as Wilkinson type ADC allowing direct energy measurement in each pixel of Timepix detector and its high spatial resolution better than 1μm, the setup is particularly suitable for radiographic imaging of small biological samples. We are able to visualize some internal biological processes and also to resolve the details of insects (morphology) using different anodes. These anodes generate different energy spectra. These spectra depend on the anode material. The resulting radiographic images varies according to the selected anode. Tiny live insects are an ideal object for our studies.

We are developing a silicon microstrip-array detector, which is operated in photon-counting mode, for line-scanned digital mammography. To enhance the x-ray interaction efficiency, the x-ray beam is oriented toward the edge of microstrips, known as the edge-on geometry. To predict the fundamental signal and noise performances induced by x-ray interactions, we performed Monte Carlo simulations. Absorbed energy distribtuions were obtained for various tilting angles (5 to 85 degrees) in the edge-on detector geometry for a wide range of incident energies from 1 to 50 keV. Based on the energy-moments theory with the obtained absorbed energy distributions, we estimated various physical performance parameters such as the quantum absorption efficiency, the average energy deposition per interaction, and the Swank noise factor. In addition, relative accuracy and imprecision in photon-energy measurements were estimated. These analyses were extended to the typical poly-energetic mammography x-ray spectra from various target materials such as molybdenium, rhodium and tungsten. Among performance parameters, the quantum absorption efficiency was gradually decreased as the tilting angle increases because of the reduction in pathlength where x-ray photons travel, while others were almost insensitive to the tilting angle. The best signal and noise performances in the edge-on silicon microstrip detector were obtained for the rhodium spectrum.

Directional detection of non-baryonic Dark Matter requires 3D reconstruction of low energy nuclear recoils tracks. A gaseous micro-TPC matrix, filled with either ³He, CF₄ or C₄H₁₀ has been developed within the MIMAC project. A dedicated acquisition electronics and a real time track reconstruction software have been developed to monitor a 512 channel prototype. This auto-triggered electronic uses embedded processing to reduce the data transfer to its useful part only, i.e. decoded coordinates of hit tracks and corresponding energy measurements. An acquisition software with on-line monitoring and 3D track reconstruction is also presented.

The Large Hadron Collider (LHC) will be upgraded in ∼ 2022 to enable peak luminosities of ∼ 5 × 10³⁴ cm⁻² s⁻¹. In the period until ∼ 2030, an integrated luminosity of ∼ 3000 fb⁻¹ is targeted, an order of magnitude increase. For ATLAS, an upgrade scenario will imply the complete replacement of its internal tracker. An all-silicon based tracker (pixels in the innermost layers, strips at outer radii) is currently being designed. The super-module is an integration concept for the barrel short and long-strip region of the future ATLAS tracker in which double-sided silicon micro-strip modules are assembled into a local support structure. A super-module prototype for eight strip modules has been built. The main components of the current prototype are described. First electrical results with DC-DC power converters are presented.

The electronic system serving 468 Cathode Strip Chambers (CSC) in the endcap regions of the CMS experiment at CERN comprises more than 3600 boards with Xilinx programmable devices. Approximately 2500 boards are mounted directly on CSC chambers; 1116 boards are housed in the 9U VME crates on the periphery of the CMS iron disks in the experimental hall, and 60 boards are located in five 9U VME crates in the underground counting room. Most of the programmable devices are mature Virtex, Virtex-E, and Virtex-2 FPGAs and XC18V02/04 PROMs. In order to improve the trigger and reconstruction efficiency at the largest values of pseudorapidity, approximately 15% of the programmable boards will be modified or replaced with the new ones based on more advanced Xilinx families. Fast and reliable remote access to all programmable devices is indispensable for periodical firmware upgrades, modifications and monitoring. Currently files produced by the Xilinx development system are converted into the VME code that subsequently provide serial JTAG access to the FPGA and PROM devices. The on-chamber mounted devices are accessed via the VME boards in the peripheral crates. We present here the status of hardware and software tools for remote access; provide estimates on times required to download a fraction or the whole system; and outline our plans for future upgrades.

A VME-based data acquisition system for beam-loss monitors has been developed and is in use in the Tevatron and Main Injector accelerators at the Fermilab complex. The need for enhanced beam-loss protection when the Tevatron is operating in collider-mode was the main driving force for the new design. Prior to the implementation of the present system, the beam-loss monitor system was disabled during collider operation and protection of the Tevatron magnets relied on the quench protection system. The new Beam-Loss Monitor system allows appropriate abort logic and thresholds to be set over the full set of collider operating conditions. The system also records a history of beam-loss data prior to a beam-abort event for post-abort analysis. Installation of the Main Injector system occurred in the fall of 2006 and the Tevatron system in the summer of 2007. Both systems were fully operation by the summer of 2008. In this paper we report on the overall system design, provide a description of its normal operation, and show a number of examples of its use in both the Main Injector and Tevatron.

This paper describes the development of a digital-based Beam Position System which was designed, developed, and adapted for the Tevatron during Collider Run II.

The optimization of an accelerator relies on the ability to monitor the behavior of the beam in an intelligent and timely fashion. The use of processor-driven front-ends allowed for the deployment of smart systems in the field for improved data collection and analysis during Run II. This paper describes the implementation of the two main systems used: National Instruments LabVIEW running on PCs, and WindRiver's VxWorks real-time operating system running in a VME crate processor.

BARC is developing a technology for the accelerator driven subcritical system (ADSS) that will be mainly utilized for the transmutation of nuclear waste and enrichment of U233. Design and prototyping of a superconducting medium velocity cavity has been taken up as a part of the ADSS project. The cavity design for β = 0.49, f = 1050 MHz has been optimized to minimize the peak electric and magnetic fields, with a goal of 5 MV/m of accelerating gradient at a Q > 5 × 10⁹ at 2 K. After the design optimization, two single cell cavities were fabricated from polycrystalline (RRR > 200) and large grain (RRR > 96) Niobium material. The cavities have been tested at 2 K in a vertical cryostat at Jefferson Lab and both achieved the performance specifications.

Calibration source with monoenergetic gamma-ray lines in wide energy range designed for gamma-ray detector energetic calibration and testing has been built. Gamma-rays are obtained from thermal neutron capture, which is a suitable and cost efficient way how to provide discrete gamma-ray lines with energies above 3 MeV with reasonable intensity. With appropriate and interchangeable targets the source can generate different gamma-ray spectra with energy up to 10 MeV. We present the data obtained with neutron capture on chlorine, but other elements with high thermal neutron capture cross-section such as chrome, iron, nickel and titanium can be used as well. As neutron source we employ radionuclide sources (²⁵²Cf or ²⁴¹Am-Be) with emission rate about 10⁶ neutrons/s. The emitted fast neutrons are moderated by a moderator made of light materials such as graphite, standard water or heavy water. Performance of the source is demonstrated by calibration spectra measured by HPGe and scintillation detectors (LaBr₃, NaI(Tl)).

Resistive Wall Current Monitors (RWCM) were designed and built for the Fermilab Tevatron (Tev) project. These devices measure longitudinal beam current from 3 KHz to 6 GHz with 1.34 ohm gap impedance. There are two RWCM's installed a few feet apart in the Tevatron, upstream RWCM is used for general purpose use, downstream RWCM is dedicated for longitudinal parameters of coalesced beam bunches and bunch intensities. The design provides a calibration or test port for injecting test signals. Microwave absorber material is used to reduce interference from spurious electromagnetic waves traveling inside the beam pipe. This paper will do an overview how the RWCM was designed and its test results.