The features of the 180nm TowerJazz 1 CMOS technology allow for the first time the use of CMOS Monolithic Active Pixel Sensors (MAPS) under the harsh operational conditions of the LHC experiments. ...The stringent requirements of the ALICE Inner Tracking System (ITS) in terms of material budget, radiation hardness, readout speed and a low power consumption have thus lead to the choice of MAPS as baseline technology option for the recently approved upgrade of the ITS and are the key drivers for R&D efforts on basic transistor and Explorer and MIMOSA pixel sensor prototypes produced in TowerJazz technology. Though the radiation loads expected for the ITS are below those of ATLAS and CMS, it is however necessary to assess the radiation hardness for ITS MAPS prototypes. Total Ionizing Dose (TID) radiation hardness has been established for basic transistor structures using a 60keV X-ray machine. The main operational characteristics and detection properties such as noise, charge collection efficiency and signal over noise ratio of Explorer-0 and MIMOSA32 and MIMOSA34 pixel sensor prototypes have been studied using X-rays ( 55 Fe) and test beams at CERN and DESY before and after Non Ionizing Energy Loss (NIEL) and TID irradiation. In this paper the results of these R&D activities will be presented and discussed.
This paper presents the design of a front-end circuit for monolithic active pixel sensors. The circuit operates with a sensor featuring a small, low-capacitance (< 2 fF) collection electrode and is ...integrated in the DPTS chip, a proof-of-principle prototype of 1.5 mm × 1.5 mm including a matrix of 32 × 32 pixels with a pitch of 15 μm. The chip is implemented in the 65 nm imaging technology from the Tower Partners Semiconductor Co. foundry and was developed in the framework of the EP-R&D program at CERN to explore this technology for particle detection. The front-end circuit has an area of 42 μm 2 and can operate with a power consumption as low as 12 nW. Measurements on the prototype relevant to the front-end will be shown to support its design.
This paper contains a compilation of parameters influencing the charge collection process extracted from a comprehensive study of partially depleted Monolithic Active Pixel Sensors with small ...(<25µm2) collection electrodes fabricated in the TowerJazz 180nm CMOS process. These results gave guidance for the optimization of the diode implemented in ALPIDE, the chip used in the second generation Inner Tracking System of ALICE, and serve as reference for future simulation studies of similar devices. The studied parameters include: reverse substrate bias, epitaxial layer thickness, charge collection electrode size and the spacing of the electrode to surrounding in-pixel electronics. The results from pixels of 28µm pitch confirm that even in partially depleted circuits, charge collection can be fast (<10ns), and quantify the influence of the parameters onto the signal sharing and amplitudes, highlighting the importance of a correct spacing between wells and of the impact of the reverse substrate bias.
Progress on photonic crystals Lecoq, P; Auffray, E; Gundacker, S ...
IEEE Nuclear Science Symposuim & Medical Imaging Conference,
2010-Oct.
Conference Proceeding
The renewal of interest for Time of Flight Positron Emission Tomography (TOF PET) has highlighted the need for increasing the light output of scintillating crystals and in particular for improving ...the light extraction from materials with a high index of refraction. One possible solution to overcome the problem of total internal reflection and light losses resulting from multiple bouncing within the crystal is to improve the light extraction efficiency at the crystal/photodetector interface by means of photonic crystals, i.e. media with a periodic modulation of the dielectric constant at the wavelength scale. After a short reminder of the underlying principles this contribution proposes to present the very encouraging results we have recently obtained on LYSO pixels and the perspectives on other crystals such as BGO, LuYAP and LuAG. These results confirm the impressive predictions from our previously published Monte Carlo simulations. A detailed description of the sample preparation procedure is given as well as the methodology and different characterization steps to control the process and evaluate the results. Pictures and quantitative results are shown, which confirm that significant light output gain factors (50% and more) can be obtained with this approach. Finally an interesting feature of photonic crystals to collimate light in some privileged directions is highlighted.
Over the last years, interest in using time-of-flight-based Positron Emission Tomography (TOF-PET) systems has significantly increased. High time resolution in such PET systems is a powerful tool to ...improve signal to noise ratio and therefore to allow smaller exposure rates for patients as well as faster image acquisition. Improvement in coincidence time resolution (CTR) in PET systems to the level of 200 ps FWHM requires the optimization of all parameters in the photon detection chain influencing the time resolution: crystal, photodetector and readout electronics. After reviewing the factors affecting the time resolution of scintillators, we will present in this paper the light yield and CTR obtained for different scintillator types (LSO:Ce, LYSO:Ce, LGSO:Ce, LSO:Ce:0.4Ca, LuAG:Ce, LuAG:Pr) with different cross-sections, lengths and reflectors. Whereas light yield measurements were made with a classical PMT, all CTR tests were performed with Hamamatsu-MPPCs S10931-050P. The CTR measurements were based on the time-over-threshold method in a coincidence setup using the ultra fast amplifier-discriminator chip NINO and a fast oscilloscope. Strong correlations between light yield and CTR were found. Excellent results have been obtained for LYSO crystals of 2 × 2 × 10 mm 3 and LYSO pixels of 0.75 × 0.75 × 10 mm 3 with a CTR of 175 ps and 188 ps FWHM, respectively.
During the LHC Long Shutdown in 2019/20, the ALICE collaboration will upgrade various detector sub-systems including the Inner Tracking System (ITS) based on Monolithic Active Pixel Sensor (MAPS) ...technology. The part of the upgraded ITS readout system installed in the experimental hall consists of 192 custom FPGA-based readout units that control and monitor the sensors and their power supply modules, receive the trigger and detector control information, and deliver the sensor data to the counting room. In this article, we will describe the requirements, the readout concept, the developed prototype boards, and the testing efforts to determine the system susceptibility to the expected radiation levels. In various beam tests with the readout prototypes it was determined that a readout system based on an SRAM FPGA with appropriate protection measures in both hardware and firmware can be successfully operated in the radiation environment expected.
This contribution describes the design of a semi-custom serialiser in 180nm CMOS technology. The design is verified for SEU immunity and BER with 30MeV protons.
A 27-year-old woman suffering from panmyelopathy for six years presented with a cervical low grade squamous intraepithelial lesion (SIL), vulvar high grade SIL and perianal squamous cell carcinoma ...with an inguinal metastasis. Southern blot hybridization with 32P-labeled human papillomavirus (HPV) DNA revealed HPV 16 DNA in varying copy numbers in material from the four locations. HPV 16 genomes persisting after surgery on the perianal tumor area were no longer detectable after betatron radiotherapy.
Time of flight (TOF) measurements in positron emission tomography (PET) are very challenging in terms of timing performance, and should achieve ideally less than 100 ps FWHM precision. We present a ...time-based differential technique to read out SiPMs that has less than 25 ps rms electronic jitter. The novel readout is a fast front end circuit (NINO) based on a first stage differential current mode amplifier with 20 ¿ input resistance. Therefore the amplifier inputs are connected differentially to the SiPM's anode and cathode ports. The leading edge of the output signal provides the time information, while the trailing edge provides the energy information. Based on a Monte Carlo photon-generation model, SPICE simulations were run with a 3 × 3 mm 2 SiPM-model, read out with a differential current amplifier. The results of these simulations are presented here and compared with experimental data obtained with a 3 × 3 × 15 mm 3 LSO crystal coupled to a SiPM. The measured time coincidence precision is interpreted by the combined Monte Carlo/SPICE simulation, as well as by Poisson statistics.
A cerium fluoride matrix composed of nine longitudinally segmented towers, approximately 25
X
0 long, has been tested in electron, muon and pion beams of momenta ranging from 10 to 150 GeV/
c. The ...results are discussed in terms of light yield, electronic noise, energy and position resolution. In spite of serious imperfections in geometry and quality of some of the crystals, an electron energy resolution of ∼0.5% has been obtained with a silicon photodiode readout, for energies above 50 GeV. The performance of cerium fluoride in a beam, its high density, high light yield and fast response, radiation resistance and ruggedness make it a very good candidate for high-resolution calorimetry at future colliders. The best conditions for production of large high-quality crystals are being studied in several firms over the world. Many CeF
3 crystals, 2 × 2 cm
2 or 3 × 3 cm
2 in cross section and up to 28 cm long, were received in 1994 from four companies, some of them with excellent light yield and radiation hardness.
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