Heavy ion radiation damage in double-sided silicon strip detectors

A ²⁵²Cf fission fragment source was used to produce heavy-ion radiation damage in a double-sided silicon strip detector. It was found that a good quality fission fragment spectrum (as determined by the peak to valley ration N_L/N_V) could not be achieved for radiation incident on the p⁺ face of the detector. However, for radiation incident on the n⁺ face, the ratio N_L/N_V remained adequate up to an accumulated dose of 4×10⁶ fragments mm⁻². For the measurement of alphas, typical resolution deteriorated from an initial 30 keV FWHM to 50 keV FWHM at a dose of 8×10⁶ fragments mm⁻² for incident on the n⁺ face, and 6×10⁶ for radiation incident on the p⁺ face. The interstrip resistance in one region of the n⁺ face broke down completely after a relatively small radiation doses incident on that face. Further investigation of this is still required.     

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.     

Radiation hardness of cryogenic silicon detectors

We shall review test results which show that silicon detectors can withstand at 130 K temperature a fluence of 2×10¹⁵ cm^–2 of 1 MeV neutrons, which is about 10 times higher than the fluence tolerated by the best detectors operated close to room temperature. The tests were carried out on simple pad devices and on microstrip detectors of different types. The devices were irradiated at room temperature using reactor neutrons, and in situ at low temperatures using high-energy protons and lead ions. No substantial difference was observed between samples irradiated at low temperature and those irradiated at room temperature, after beneficial annealing. The design of low-mass modules for low-temperature trackers is discussed briefly, together with the cooling circuits for small and large systems.     

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.     

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.     

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.     

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.     

Advances in silicon carbide X-ray detectors

The latest advances in SiC X-ray detectors are presented: a pixel detector coupled to a custom ultra low noise CMOS preamplifier has been characterized at room and high temperature. An equivalent noise energy (ENE) of 113 eV FWHM, corresponding to 6.1 electrons r.m.s., has been achieved with the detector/front-end system operating at +30 °C. A Fano factor of F=0.10 has been estimated from the ⁵⁵Fe spectrum. When the system is heated up to +100 °C, the measured ENE is 163 eV FWHM (8.9 electrons r.m.s.). It is determined that both at room and at high temperature the performance are fully limited by the noise of the front-end electronics. It is also presented the capability of SiC detectors to operate in environments under unstable temperature conditions without any apparatus for temperature stabilization; it has been proved that a SiC detector can acquire high resolution X-ray spectra without spectral line degradation while the system temperature changes between +30 and +75 °C.     

Ion-implanted capacitively coupled silicon strip detectors with integrated polysilicon bias resistors processed on a 100 mm wafer

Double-sided silicon strip detectors with integrated coupling capacitors and polysilicon resistors have been processed on a 100 mm wafer. A detector with an active area of 19 × 19 mm² was connected to LSI readout electronics and tested. The strip pitch of the detector is 25 μm on the p-side and 50 μm on the n-side. The readout pitch is 50 μm on both sides. The number of readout strips is 774 and the total number of strips is 1161. On the p-side a signal-to-noise of 35 has been measured using a ⁹⁰Sr β-source. The n-side has been studied using a laser.     

Silicon strip detectors with capacitive charge division

Measurements of the behaviour of various high-resolution silicon strip detectors with capacitive charge division have been made in a high-energy particle beam. The results are compared with an electrostatic model which calculates the charges deposited on the strips after the passage of a minimum ionizing particle. Good agreement is found and the model is used to propose a method of improving the charge-division properties of such detectors.     

Charge collection in partially depleted silicon detectors

The behaviour of partially depleted silicon detectors deserves some attention in the design of large systems such as electromagnetic or hadronic calorimeters in which these detectors are used and conservative operating conditions must be imposed [1–3].We have experimentally investigated charge collection from the undepleted region in silicon detectors manufactured for high energy calorimetry by Ansaldo Semiconductors S.p.A.The observed results are compared with a simple model.     

Evaluation of prototype silicon drift detectors

Silicon drift detectors, of two elementary designs, have been fabricated and tested using β electrons and light pulses. Drift of electrons within the detectors has been observed over distances up to about 8 mm with high efficiency. Results are presented, some of which identify important design parameters of such devices.     

Microwave detectors based on porous silicon

Two types of structures comprising porous silicon (por-Si) layers between metal electrodes were prepared, which possessed nonlinear (A type) and linear (B type) current-voltage characteristics. The exposure to microwave radiation leads to the appearance of an emf between electrodes. The B-type structures exhibit high voltage responsivity and can be used as microwave radiation sensors.     

The delphi silicon strip microvertex detector

The silicon strip microvertex detector for the DELPHI experiment at LEP is presented. It consists of two cylindrical layers with a total of 165 888 strips. The design parameters of the final project are described.The microstrip counters have a pitch of 16.6 μm, and are read out every 50 μm using the capacitive charge division method. The electronics used is the Microplex chip, an NMOS integrated circuit, which provides 128 channels of low noise charge sensitive amplifiers with multiplexed analog output. Results of signal-to-noise ratio from beam tests on prototype detectors are given and discussed.