A high resolution silicon beam telescope

We describe the design and present the performances of a charged particle telescope used for high resolution silicon pixel developments. A telescope made of four x and four y single-sided silicon microstrip layers was built, providing an r.m.s. position resolution of 1 μm for high energy charged particles. A signal over noise ratio of 130 was achieved with minimum ionizing particles.     

Applications of silicon detectors in high energy physics and astrophysics

Silicon detectors are being increasingly used in high energy physics and in astronomy. In the former case they are used for precisely locating the trajectories of particles which traverse the detectors, while in the latter case they are used for very low level light imaging. In both applications, the use of silicon is preferred because of the low energy needed to liberate an electron-hole pair in the medium and because of the highly developed planar technology which allows sophisticated devices with excellent spatial precision to be fabricated.The specific devices discussed are microstrip detectors and 2-dimensional imaging CCDs, including a summary of radiation damage since this is of importance in both the astronomical and particle physics applications.     

Displacement sensing resolution of position-sensitive detectors inatmospheric turbulence using retroreflected beam

The position sensing resolution of a lateral-effect photodiode (LEP) and a four-quadrant (4Q) photodetector used as the position sensitive detector (PSD) in a sensor which measures the lateral displacement of a corner cube reflector (CCR) by illuminating it and detecting the position of the reflected light spot with the PSD is studied. An LEP is much noisier than a 4Q detector, but in an outdoor environment the sensitivity of the 4Q detector to atmospheric turbulence due to defocusing makes its resolution worse than that of an LEP. Submillimeter resolutions at the target distances of several hundreds of meters are electrically achievable with an LEP. Outdoors, however, its resolution is also bounded by the atmospheric turbulence. In turbulent measurement conditions, standard deviations of better than 1 cm were typically achievable up to the distance of 300 m and about 10 cm up to half a kilometer     

The electron-proton colliding beam facility HERA

The HERA electron-proton storage ring now under construction at DESY will collide 30 GeV electrons with 820 GeV protons. The physics programme, the layout of the machine and the development of superconducting accelerator magnets are described.     

A prototype of very high resolution small animal PET scanner using silicon pad detectors

A very high-resolution small animal positron emission tomograph (PET), which can achieve sub-millimeter spatial resolution, is being developed using silicon pad detectors. The prototype PET for a single slice instrument consists of two 1 mm thick silicon pad detectors, each containing a 32×16 array of 1.4×1.4 mm pads readout with four VATAGP3 chips which have 128 channels low-noise self-triggering ASIC in each chip, coincidence units, a source turntable and tungsten slice collimator. The silicon detectors were located edgewise on opposite sides of a 4 cm field-of-view to maximize efficiency. Energy resolution is dominated by electronic noise, which is 0.98% (1.38 keV) FWHM at 140.5 keV. Coincidence timing resolution is 82.1 ns FWHM and coincidence efficiency was measured to be 1.04×10⁻³% from two silicon detectors with annihilation photons of ¹⁸F source. Image data were acquired and reconstructed using conventional 2-D filtered-back projection (FBP) and a maximum likelihood expectation maximization (ML-EM) method. Image resolution of approximately 1.45 mm FWHM is obtained from 1-D profile of 1.1 mm diameter ¹⁸F line source image. Even better resolution can be obtained with smaller detector element sizes. While many challenges remain in scaling up the instrument to useful efficiency including densely packed detectors and significantly improved timing resolution, performance of the test setup in terms of easily achieving sub-millimeter resolution is compelling.     

Tests on large diameter superconducting solenoids designed for colliding beam accelerators

Two prototype large diameter thin coil solenoids which use the mechanical structure to moderate quenches, have been built and systematically tested. The solenoids are cooled by two phase helium flowing in tubes which form a part of the coil structure. The coils have been tested by inducing a series of quenches at various currents. The results of these tests are given in this paper.     

High speed scanning electron beam annealing of ion-implanted silicon layers

Sawtooth scanning with a 40 keV electron probe at frequencies of 10⁵–10⁶ Hz can be used for generating in a silicon surface a quasi-line-shaped temperature field. With a power of 70–80 W and a spot diameter of 50 μm this yields a surface temperature of about 1500 K. The procedure was tentatively used for solid state annealing of ⁷⁵As-ion-implanted silicon layers to a depth of 1000 Å. These beam parameters permit an areal throughput of 10 cm² s^-1 without back side cooling since the substrate temperatures at the back side can be kept below 800 K.     

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.     

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.     

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.     

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 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.     

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.     

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.