L. Servoli

The L3 silicon microvertex detector

Abstract The design and construction of the silicon strip microvertex detector (SMD) of the L3 experiment at LEP are described. We present the sensors, readout electronics, data acquisition system, mechanical assembly and support, displacement monitoring systems and radiation monitoring system of the recently installed double-sided, double-layered SMD. This detector utilizes novel and sophisticated techniques for its readout.

The CMS remote analysis builder (CRAB)

The CMS experiment will produce several Pbytes of data every year, to be distributed over many computing centers geographically distributed in different countries. Analysis of this data will be also performed in a distributed way, using grid infrastructure. CRAB (CMS Remote Analysis Builder) is a specific tool, designed and developed by the CMS collaboration, that allows a transparent access to distributed data to end physicist. Very limited knowledge of underlying technicalities are required to the user. CRAB interacts with the local user environment, the CMS Data Management services and with the Grid middleware. It is able to use WLCG, gLite and OSG middleware. CRAB has been in production and in routine use by end-users since Spring 2004. It has been extensively used in studies to prepare the Physics Technical Design Report (PTDR) and in the analysis of reconstructed event samples generated during the Computing Software and Analysis Challenge (CSA06). This involved generating thousands of jobs per day at peak rates. In this paper we discuss the current implementation of CRAB, the experience with using it in production and the plans to improve it in the immediate future.

Characterization of standard CMOS pixel imagers as ionizing radiation detectors

Recent developments in the domain of the standard CMOS imagers for visible light, mainly in the reduction of the pixel size, has led us to investigate the suitability of some of these devices as ionizing radiation detectors. A standard 640x480 imager with 5.6x5.6 micrometer pixel size (Aptina product MT9SH06) has been characterized with X-ray (55Fe and 8 keV X-ray tube) and charged particles sources (500 MeV electrons). The main results obtained are: a small average pixel multiplicity (4-5), for the detection of either X-ray or charged particles; a good linearity of the response; a S/N ratio of 29 for a Minimum Ionizing Particle and an estimated sensitivity to X-rays down to 1 keV.

Radiation hardness of three-dimensional polycrystalline diamond detectors

The three-dimensional concept in particle detection is based on the fabrication of columnar electrodes perpendicular to the surface of a solid state radiation sensor. It permits to improve the radiation resistance characteristics of a material by lowering the necessary bias voltage and shortening the charge carrier path inside the material. If applied to a long-recognized exceptionally radiation-hard material like diamond, this concept promises to pave the way to the realization of detectors of unprecedented performances. We fabricated conventional and three-dimensional polycrystalline diamond detectors, and tested them before and after neutron damage up to 1.2 ×1016u2009cm−2, 1u2009MeV-equivalent neutron fluence. We found that the signal collected by the three-dimensional detectors is up to three times higher than that of the conventional planar ones, at the highest neutron damage ever experimented.

The L3 Silicon Microvertex Detector: installation and results on 1993 performance

Abstract The status of the Silicon Microvertex Detector (SMD) and its installation into the LEP-L3 experiment are presented, highlighting novel features and sophisticated techniques. Preliminary results based on 1993 data are given and compared with Monte Carlo predictions, to understand the detector performances and its tracking capabilities.

Use of a CMOS Image Sensor for an Active Personal Dosimeter in Interventional Radiology

Interventional radiologists and staff members, during all their professional activities, are frequently exposed to protracted and fractionated low doses of ionizing radiation. Due to skin tissues and peripheral blood irradiation, these exposures can result in deterministic effects (radiodermatitis, aged skin, and hand depilation) or stochastic ones (skin and non-solid cancer incidence). The authors present a novel approach to perform online monitoring of the staff during their interventions by using a device based on an Active Pixel Sensor. The performance of the sensor as an X-ray radiation detector has been evaluated with a proper experimental setup: the number of photons and the generated charge have been assessed as dosimetric observables from the frames acquired by the sensor using a two-threshold clustering algorithm, the efficiency of which has been evaluated as well. The correlation of these observables with passive dosimeter dose measurements has been analyzed: a good linearity has been demonstrated, and the response difference between pulsed and continuous operational modes is reduced to less than 10%, marking a distinct improvement with respect to commercial Active Personal Dosimeters.

Use of standard CMOS pixel imagers as ionizing radiation detectors

The recent developments in the domain of the standard CMOS imagers for visible light, mainly in the reduction of the pixel size, has led us to investigate the suitability of some of these devices as ionizing radiation detectors. A standard 640x480 imager with 5.6x5.6 micrometer pixel size (Micron product type MT9V011) has been characterized with both photons ( 55Fe and 8 keV X-ray tube) than charged particles sources ( 500 MeV electrons). The main results obtained are: a small pixel multiplicity (4–5), for the detection of either X-ray or charged particles; a good linearity of the response; a S/N ratio ≫ 30 for a Minimum Ionizing Particle and an estimated sensitivity down to about 2 keV.

Experimental Characterization of a Personal Wireless Sensor Network for the Medical X-Ray Dosimetry

Wireless sensor networks are an important technology for large-scale monitoring, providing sensor measurements at high temporal and spatial resolution. In healthcare applications, a variety of system prototypes and commercial products have been designed and manufactured with the aim to provide an alternative and more efficient method for realtime operator monitoring during medical procedures. In the framework of the Real-Time Active Pixel Dosimetry project, the attention has been focused on dose monitoring of interventional radiology (IRad) operators. A sensor network has been developed, which consists of several personal sensor nodes (PSNs), monitoring the absorbed dose in different positions of the operator body (e.g., on the head or arms) and providing a measurement of the absorbed dose for each medical procedure. In this paper, we describe the first characterization of the final version of a system by measuring the radiation diagram and exposing the system to a direct X-ray beam showing a linearity of the response up to 3.3 mGy/s of dose rate. The system has been characterized during several IRad procedures when two PSNs have been simultaneously used in the network. The packet error rate of the network has been measured and the absorbed dose has been evaluated for each medical procedure, showing an uncertainty on the dose measurement lower than 10% with respect to the reference dosimetric devices.

Performance of CMOS imager as sensing element for a Real-time Active Pixel Dosimeter for Interventional Radiology procedures

Staff members applying Interventional Radiology procedures are exposed to ionizing radiation, which can induce detrimental effects to the human body, and requires an improvement of radiation protection. This paper is focused on the study of the sensor element for a wireless real-time dosimeter to be worn by the medical staff during the interventional radiology procedures, in the framework of the Real-Time Active PIxel Dosimetry (RAPID) INFN project. We characterize a CMOS imager to be used as detection element for the photons scattered by the patient body. The CMOS imager has been first characterized in laboratory using fluorescence X-ray sources, then a PMMA phantom has been used to diffuse the X-ray photons from an angiography system. Different operating conditions have been used to test the detector response in realistic situations, by varying the X-ray tube parameters (continuous/pulsed mode, tube voltage and current, pulse parameters), the sensor parameters (gain, integration time) and the relative distance between sensor and phantom. The sensor response has been compared with measurements performed using passive dosimeters (TLD) and also with a certified beam, in an accredited calibration centre, in order to obtain an absolute calibration. The results are very encouraging, with dose and dose rate measurement uncertainties below the 10% level even for the most demanding Interventional Radiology protocols.

Analysis of 3D stacked fully functional CMOS Active Pixel Sensor detectors

The IC technology trend is to move from 3D flexible configurations (package on package, stacked dies) to real 3D ICs. This is mainly due to i) the increased electrical performances and ii) the cost of 3D integration which may be cheaper than to keep shrinking 2D circuits. Perspective advantages for particle tracking and vertex detectors applications in High Energy Physics can be envisaged: in this work, we will focus on the capabilities of the state-of-the-art vertical scale integration technologies, allowing for the fabrication of very compact, fully functional, multiple layers CMOS Active Pixel Sensor (APS) detectors. The main idea is to exploit the features of the 3D technologies for the fabrication of a ``stack of very thin and precisely aligned CMOS APS layers, leading to a single, integrated, multi-layers pixel sensor. The adoption of multiple-layers single detectors can dramatically reduce the mass of conventional, separated detectors (thus reducing multiple scattering issues), at the same time allowing for very precise measurements of particle trajectory and momentum. As a proof of concept, an extensive device and circuit simulation activity has been carried out, aiming at evaluate the suitability of such a kind of CMOS active pixel layers for particle tracking purposes.