Radiation damage in silicon strip detectors

Silicon strip detectors with 5 μm spatial resolution have been used during 1982–1985 in the ACCMOR spectrometer at CERN. After a local beam flux of about 10¹⁴ minimum ionizing particles per cm² we observe a significant increase in dark current and systematic distortions in the measured coordinates which are explained in terms of a decrease in the effective donor concentration.     

Development of a fabrication technology for double-sided AC-coupled silicon microstrip detectors

We report on the development of a fabrication technology for double-sided, AC-coupled silicon microstrip detectors for tracking applications. Two batches of detectors with good electrical figures and a low defect rate were successfully manufactured at IRST Laboratory. The processing techniques and the experimental results obtained from these detector prototypes are presented and discussed.     

Development of high density readout for silicon strip detectors

A compact readout for silicon strip detectors is being developed. It employs an nMOS circuit with 128 channels of charge sensitive amplifiers and multiplexed output.     

Performance of silicon strip detectors with 50 and 100 μm strip distance

Implanted silicon multistrip detectors with 50 and 100 μ m pitch have been developed, fabricated and tested. Each strip is read out by using charge sensitive preamplifiers. Results of efficiency, noise and resolution are presented and a system for use in an experiment is described.     

Lithium-drifted,silicon radiation detectors for harsh radiation environments

A model describing the passivation by Li atoms of acceptors arising from radiation damage in Si detectors has been developed. Our studies indicate that it is possible to produce a protocol that will allow the in situ recovery of Lithium-drifted Si particle detectors under irradiation by high-energy particles. Our model for particle damage recovery is supported by preliminary results obtained on the recovery of old, degraded detectors.     

Radiation damage test of silicon multistrip detectors

Radiation damage test of silicon multistrip detectors were performed using an 800 GeV proton beam. The local proton fluence was up to 10¹⁴/cm². The observed prominent changes were the proportional increase of the leakage current with the integrated beam intensity and the change of the effective impurity density. The effective impurity density decreases with fluence up to ≈4×10¹³/cm² but for greater fluences, it increases. This may indicate the type conversion of the bulk silicon. We have also observed the change of the carrier collection properties, which may be caused by the synergistic effect of the charge-up of surface SiO₂ and the decrease of the effective impurity density in bulk silicon.     

Energy and spatial response of silicon strip detectors to X-rays

This paper describes an experimental investigation of the energy and spatial response of silicon strip detectors used for X-ray measurements. The measurements of single strip amplitude distributions have been performed for a p⁺–n silicon strip detector irradiated with X-rays for different detector bias voltages and for two measurements geometries (with the detector irradiated from either the strip side or from the ohmic contact side). The measured amplitude distributions have been compared with those obtained from simulations using the developed simulation package. The spatial response of the detector has been measured by scanning an edge across the strips and measuring the corresponding strip count rate. The measured spatial response has been compared with that obtained from simulations.     

The influence of channelling on radiation damage produced in silicon during ion bombardment

The ion bombardment of silicon results in the formation of an amorphous phase in the vicinity of the bombarded regions. This gives rise to a milky appearance which is easily distinguishable from an adjacent unbombarded region. An experiment is described which was specifically designed to study the influence of channelling of incident 80 keV Ne⁺ ions on the formation of this amorphous phase. It is found that channelling significantly reduces the rate at which this phase is produced, and in the particular case of the 110 axial channel this corresponds to a reduction in radiation damage by a factor of about 8. The results are compared with the current theories of channelling and are found to be in reasonable quantitative agreement.     

Fast bipolar front-end for binary readout of silicon strip detectors

A very fast low-noise low-power 64-channel front-end chip for binary readout of silicon microstrip detectors (FABRIC) has been designed and manufactured using the full-custom bipolar process SHPi by Tektronix. The circuit consists of a preamplifier, a shaper and a discriminator. A noise level of 476 e⁻ + 63 e⁻/pF has been obtained for the amplifier peaking time of 15 ns. The walk time of the discriminator is less than 5 ns for input signals ranging from 2 fC to 8 fC at a discriminator threshold of 1 fC. The dead time for two minimum ionizing particle signals is 40 ns. The above parameters have been obtained with a low power consumption of 1.3 mW per channel.     

The physics of radiation damage in particle detectors

Intense high-energy particle beams cause damage to semiconductor detectors and signal-conditioning electronics by displacement and long-term ionization effects. While first-principles prediction of effects are not practical, the magnitude of each effect can be scaled approximately between particle energy and type by using an appropriate scaling parameter.     

The effect of radiation on ion-implanted silicon detectors

Investigations on changes of characteristics of ion-implanted silicon-junction detectors when exposed to various doses of radiation (< 10⁵ and >10⁶ rad) were performed. It was found that the increase of leakage current depends not only on the dose but also on the gradient of irradiation.For doses higher than 10⁶ rad, the fully depleted layer thickness of the detector before irradiation decreases and becomes dependent on temperature. Also the most probable energy loss decreases and the width of the noise distribution broadens.     

A digital X-ray imaging system based on silicon strip detectors working in edge-on configuration

We present the energy resolution and imaging performance of a digital X-ray imaging system based on a 512-strip silicon strip detector (SSD) working in the edge-on configuration. The SSDs tested in the system are 300 μm thick with 1 or 2-cm-long strips and 100 μm pitch. To ensure a very small dead area of the SSD working in edge-on configuration, the detector is cut perpendicular to the strips at a distance of only 20 μm from the end of the strips. The 512-strip silicon detector is read out by eight 64-channel integrated circuits called DEDIX [Grybos et al., IEEE Trans. Nucl. Sci. NS-54 (2007) 1207]. The DEDIX IC operates in a single photon counting mode with two independent amplitude discriminators per channel. The readout electronic channel connected to a detector with effective input capacitance of about 2 pF has an average equivalent noise charge (ENC) of about 163 el. rms and is able to count 1 Mcps of average rate of input pulses. The system consisting of 512 channels has an excellent channel-to-channel uniformity—the effective threshold spread calculated to the charge-sensitive amplifier inputs is 12 el. rms (at one sigma level). With this system a few test images of a phantom have been taken in the 10–30 keV energy range.     

Geometrically-metastable superconducting strip detectors

Geometrical metastability, observed in superconducting type I tin flat strips, has already been proposed as a principle for particle detection. In this paper, we first show that the geometrical metastability is not specific to superconductors that undergo a first order transition in magnetic field. Geometry dependant irreversible flux penetration is also observed in type II niobium strips, submitted to a continuously increasing perpendicular magnetic field. Secondly, the rupture of the geometrical metastability can also be achieved by thermal nucleation. First results on irradiation experiments show that the energy deposition of an incoming -particle induces the penetration of multiquantum flux tubes into a superconducting tin strip.     

Comparative measurements of highly irradiated n-in-p and p-in-n 3D silicon strip detectors

Silicon detectors in 3D technology are a candidate for applications in environments requiring an extreme radiation hardness, as in the innermost layers of the detectors at the proposed High-Luminosity LHC. In 3D detectors, the electrodes are made of columns etched into the silicon perpendicular to the surface. This leads to higher electric fields, a smaller depletion voltage and a reduced trapping probability of the charge carriers compared to standard planar detectors. In this article, the signal and the noise of irradiated n-in-p and p-in-n 3D silicon strip detectors are compared. The devices under test have been irradiated up to a fluence of 2×10¹⁶ 1 MeV neutron equivalent particles per square centimetre (n_eq/cm²), which corresponds to the fluence expected for the inner pixel detector layers at the High-Luminosity LHC. A relative charge collection efficiency of approximately 70% was obtained even after the highest irradiation fluence with both detector types. The influence of different temperatures on the signal and the noise is investigated and results of annealing measurements are reported.     

Hotspot propagation in superconductive strip detectors

Hotspots formed in superconductive strips due to interaction with particles are considered. The superconductive strip detector is considered in terms of a model of one-dimensional superconductor. D.C. electric current flowing through a film leads to Joule heating of the normal phase and causes either expansion or collapse of the hotspot. It is shown that the energy of a particle can be obtained by measuring the length of the expanding hotspot.     

Development of large area silicon detectors: Special properties and radiation stability

Large area totally depleted silicon detectors with a sensitive surface of up to 35 cm² have been developed for applications in high energy physics with emphasis on electromagnetic and hadronic shower calorimeters. Special fabrication processes and related diode properties, including long-term stability, will be discussed. Special attention is given to edge effects which are investigated with a scanning proton microbeam. The radiation sensitivity of such detectors was extensively studied through capacitance-voltage as well as capacitance-frequency measurements.     

Response studies on silicon surface barrier detectors for low energy ion spectrometry in space

Accurate measurements of the three-dimensional directional distribution of low energy ions in space require a careful calibration of the silicon surface barrier detectors mostly employed. This paper describes a systematic search for the pulse-height defects in the detector response to protons in the 25–150 keV energy range. The results ensured a proper pre-flight calibration of the ISEE-3 proton spectrometer and also allow some conclusions on the ratio of the average energies ?_p and ?_e? expended for electron-hole pair generation in silicon.     

Influence of ion radiation damage on surface reactivity

The role of ion irradiation on the reactivity of surfaces is reviewed with special attention to those experiments that make use of ultrahigh vacuum surface techniques. Ion irradiation effects on adsorption, incorporation and catalysis are discussed. The difficulties involved in directly probing surface defects are documented and a discussion of several techniques offering good prospects in this defect characterization is presented. Comparisons are made with related areas such as stepped sufaces and dislocation effects on reactivity but a review of the latter subjects is not attempted. Some examples of theoretical efforts in relation to the role of surface defects in gas-surface interactions are also included.     

Development of radiation hard edgeless detectors with current terminating structure on p-type silicon

The development of edgeless Si detectors was stimulated by the tasks of the total pp cross-section study in the TOTEM experiment at the Large Hadron Collider at CERN. For this, the dead region at the detector diced side should be reduced below 50 μm. This requirement is successfully realized in edgeless Si detectors with current terminating structure (CTS), which are now operating at LHC. The development of the experiment and future LHC upgrade need the elaboration of radiation hard version of edgeless Si detectors. The current investigation represents an extension in understanding on edgeless detectors operation and development of a new issue - edgeless detectors with CTS on p-type Si.