Single Silicon Detector Research Articles

Development of high performance PIN-silicon detector and its application in radioactive beam physical experiment

In view of the great demand for large-area silicon detectors in domestic nuclear physics experiments, a type of 300-μm-thick high-performance square silicon detector with a large active area of 50 mm×50 mm by using overprinting technology is developed in the Institute of Modern Physics of the Chinese Academy of Sciences. Based on this technology, SiO<sub>2</sub> contamination caused by the photolithography and corrosion processes is effectively reduced. The detector has an excellent performance with a yield of up to 80%. Under –45 V (depletion voltage) bias, the leakage current of the detector is less than 40 nA. The detector is tested with a three-component α radioactive source. The energy resolution (<i>σ</i>) is about 45 keV for 5-MeV α particles. Used as an energy deposition(Δ<i>E</i>) detector, the detector performance is also tested for measuring reaction products of 250 MeV/u <sup>11</sup>C radioactive beams impinging on a carbon target. The results show that the charge number resolution of a single silicon detector is 0.17 for the carbon isotope, which is similar to that measured with the same type of detectors available from the market. With the average deposition energy of three silicon detectors used, the charge number resolution for carbon isotope reaches a better value of 0.11. With this resolution, C and B isotopes are clearly distinguished, meeting the requirements for particle identification in intermediate- and high-energy radioactive beam experiments.

New semi-automatic method for reaction product charge and mass identification in heavy-ion collisions at Fermi energies

This article presents a new semi-automatic method for charge and mass identification of charged nuclear fragments using either ΔE−E correlations between measured energy losses in two successive detectors or correlations between charge signal amplitude and rise time in a single silicon detector, derived from digital pulse shape analysis techniques. In both cases different nuclear species (defined by their atomic number Z and mass number A) can be visually identified from such correlations if they are presented as a two-dimensional histogram (‘identification matrix’), in which case correlations for different species populate different ridge lines (‘identification lines’) in the matrix. The proposed algorithm is based on the identification matrix's properties and uses as little information as possible on the global form of the identification lines, making it applicable to a large variety of matrices. Particular attention has been paid to the implementation in a suitable graphical environment, so that only two mouse-clicks are required from the user to calculate all initialization parameters. Example applications to recent data from both INDRA and FAZIA telescopes are presented.

Systematic investigation of background sources in neutron flux measurements with a proton-recoil silicon detector

Proton-recoil detectors (PRDs), based on the well known standard H(n,p) elastic scattering cross section, are the preferred instruments to perform precise quasi-absolute neutron flux measurements above 1MeV. The limitations of using a single silicon detector as PRD at a continuous neutron beam facility are investigated, with the aim of extending such measurements to neutron energies below 1MeV. This requires a systematic investigation of the background sources affecting the neutron flux measurement. Experiments have been carried out at the AIFIRA facility to identify these sources. A study on the role of the silicon detector thickness on the background is presented and an energy limit on the use of a single silicon detector to achieve a neutron flux precision better than 1% is given.

The Fly’s Eye Energetic Particle Spectrometer (FEEPS) Sensors for the Magnetospheric Multiscale (MMS) Mission

The Energetic Particle Detector (EPD) Investigation is one of five particles and fields investigations on the Magnetospheric Multiscale (MMS) mission. This mission consists of four satellites operating in close proximity in elliptical, low-inclination orbits, and is focused upon the fundamental physics of magnetic reconnection. The Energetic Particle Detector (EPD) investigation aboard the four MMS spacecraft consists of two instrument designs, the EIS (Energetic Ion Spectrometer) and the FEEPS (Fly’s Eye Electron Proton Spectrometer). This present paper describes FEEPS from an instrument physics and engineering point of view, and provides some test and calibration data to facilitate effective analysis and use of the flight data for scientific purposes. A FEEPS consists of six Heads, each composed of two Eyes. Each eye is a particle telescope with a single silicon detector; there are nine electron eyes and three ion eyes per FEEPS. The energy coverage is from 25 keV to 650 keV for electrons and 45 keV to 650 keV for ions. Each eye has sixteen energy channels, the spacing of which can be modified by command. The fields of view and pointing of each eye are designed to provide a broad, instantaneous field of view for the twelve eyes per FEEPS. There are two FEEPS per MMS spacecraft mounted such that the pair along with the single EIS provide more than $3\pi$ -sr instantaneous solid-angle coverage and complete coverage in the equatorial region. A twenty-second spacecraft rotation period is divided into sixty-four sectors to provide detailed temporal and spatial sampling. Data are acquired in three modes: Burst Mode, the primary science mode; Fast Survey Mode; and Slow Survey Mode.

Status and performances of the FAZIA project

FAZIA is designed for detailed studies of the isospin degree of freedom, extending to the limits the isotopic identification of charged products from nuclear collisions when using silicon detectors and CsI(Tl) scintillators. We show that the FAZIA telescopes give isotopic identification up to Z~25 with a ΔE-E technique. Digital Pulse Shape Analysis makes possible elemental identification up to Z=55 and isotopic identification for Z=1-10 when using the response of a single silicon detector. The project is now in the phase of building a demonstrator comprising about 200 telescopes.

Fully integrated monolithic optoelectronic transducer for real-time protein and DNA detection: The NEMOSLAB approach

The development and testing of a portable bioanalytical device which was capable for real-time monitoring of binding assays was demonstrated. The device was based on arrays of nine optoelectronic transducers monolithically integrated on silicon chips. The optocouplers consisted of nine silicon avalanche diodes self-aligned to nine silicon nitride waveguides all converging to a single silicon detector. The waveguides were biofunctionalized by appropriate recognition molecules. Integrated thick polymer microchannels provided the necessary fluidic functions to the chip. A single sided direct contact scheme through a board-to-board receptacle was developed and combined with a portable customized readout and control instrument. Real-time detection of deleterious mutations in BRCA1 gene related to predisposition to hereditary breast/ovarian cancer was performed with the instrument developed using PCR products. Detection was based on waveguided photons elimination through interaction with fluorescently labeled PCR products. Detection of single biomolecular binding events was also demonstrated using nanoparticles as labels. In addition, label-free monitoring of bioreactions in real time was achieved by exploiting wavelength filtering on photonic crystal engineered waveguides. The proposed miniaturized sensing device with proper packaging and accompanied by a portable instrument can find wide application as a platform for reliable and cost effective point-of-care diagnosis.

Simultaneous observation of the radiation environment inside and outside the ISS

The low-Earth orbit (LEO) radiation environment has been directly observed by the Intra-Vehicular (IV) and Extra-Vehicular (EV) Charged Particle Directional Spectrometers (CPDS) aboard the International Space Station (ISS). The EV instrument is mounted on the S0 truss of the ISS and consists of three separate silicon detector telescopes which are oriented in different directions. The IV instrument is a single silicon detector telescope located inside the US Laboratory module of the ISS. We report on the current state of the data analysis for these instruments, which includes the proton stopping particle spectrum, relative carbon, nitrogen, and oxygen ion (CNO) abundances, and linear energy transfer (LET) spectra.

Individual monitoring in mixed neutron/photon fields using a single silicon detector.

A device based on a single silicon detector of special converter/detector design optimised for the determination of the neutron dose equivalent is also used for the determination of the photon dose equivalent. While the neutron dose is determined on the basis of signals corresponding to energy depositions above 1.5 MeV, depositions between 80 keV and 150 keV are used for the photon dose equivalent. In this way, a photon response is achieved which varies by less than 30% in the energy region from 80 keV to 7 MeV for irradiation at normal incidence and at 60 degrees to the normal. The lower limit of detection is of the order of 1 microSv. Neutrons contribute to the photon reading by less than 2% in mixed fields with a comparable dose equivalent from neutrons and photons.

Response of silicon-based linear energy transfer spectrometers: implication for radiation risk assessment in space flights

There is considerable interest in developing silicon-based telescopes because of their compactness and low power requirements. Three such telescopes have been flown on board the Space Shuttle to measure the linear energy transfer spectra of trapped, galactic cosmic ray, and solar energetic particles. Dosimeters based on single silicon detectors have also been flown on the Mir orbital station. A comparison of the absorbed dose and radiation quality factors calculated from these telescopes with that estimated from measurements made with a tissue equivalent proportional counter show differences which need to be fully understood if these telescopes are to be used for astronaut radiation risk assessments. Instrument performance is complicated by a variety of factors. A Monte Carlo-based technique was developed to model the behavior of both single element detectors in a proton beam, and the performance of a two-element, wide-angle telescope, in the trapped belt proton field inside the Space Shuttle. The technique is based on: (1) radiation transport intranuclear-evaporation model that takes into account the charge and angular distribution of target fragments, (2) Landau–Vavilov distribution of energy deposition allowing for electron escape, (3) true detector geometry of the telescope, (4) coincidence and discriminator settings, (5) spacecraft shielding geometry, and (6) the external space radiation environment, including albedo protons. The value of such detailed modeling and its implications in astronaut risk assessment is addressed.

Development of a real-time hand dose monitor for personnel in interventional radiology.

Medical procedures denoted as interventional radiology require operation near an X ray beam, which brings high dose exposures to the operators' hands. For the effectual control of their extremity doses, a prototype of a real-time wrist dosemeter has been developed, hand dose monitor (HDM), based on a single silicon detector. Experiments were performed to test its response to diagnostic X rays. The HDM was highly sensitive and showed a linear response down to doses of a few tens of microsieverts. Though dose rate, energy and angular dependence of the response were observed in some extreme conditions, the HDM was proved to be of practical use if it was appropriately calibrated. Since an HDM enables personnel to check their hand doses on a real-time basis, it would enable medical staff to control the exposure themselves.

Particle identification in solid-state detectors by means of pulse-shape analysis — results of computer simulations

A simple semi-empirical model has been used to simulate pulse shapes in silicon detectors for heavy-ion spectroscopy. The model describes qualitatively the results of a previous experiment which was performed to study the feasibility of pulse-shape analysis for identifying intermediate-mass fragments in single silicon detectors. The observed limits of the dynamic range for particle identification can be understood within the model. These limitations are predicted to be overcome by injecting the ions into the rear side of a totally depleted detector, and by combining the time-of-flight and the pulse-shape techniques to establish a new scheme of signal processing. With this technique, Z identification should be possible down to 0.5 A MeV for ions with mass numbers A ≤ 30.