The influence of the strip width on the performance of a strip detector

In high energy physics experiments strip detectors are used for vertex determination. The strip geometry of such detectors has up to now been symmetrical, with the strip width and interspacing equalling each other. However, nothing is known about the exact importance of this geometry. Therefore, a theoretical and an experimental study was made of the influence of the strip width on a strip detector's performance. Firstly, the potential and electric field distributions in the neighbourhood of the strips were calculated, which enabled the influence of parameters such as detector geometry, bias voltage and surface charge to be investigated. Secondly, test devices were designed and fabricated. These devices, in which both the pitch and the strip width were varied, were tested on their electrical behaviour as well as on their interaction with radiation.The main conclusion to be drawn from this research is that the position precision is independent of the strip width, while the electrical characteristics are not. Small strips are preferable, with the minimum determined by the technological possibilities.     

Optical/UV and X-Ray Microwave Kinetic Inductance Strip Detectors

Microwave Kinetic Inductance Detectors (MKIDs) are superconducting detectors that sense the change in the surface impedance of a thin superconducting film when Cooper Pairs are broken by using a high quality factor resonant circuit. We are developing strip detectors that have aluminum MKID sensors on both ends of a rectangular tantalum strip. These devices can provide one dimensional spatial imaging with high quantum efficiency, energy resolution, and microsecond time resolution for single photons from the IR to the X-ray. We have demonstrated X-ray strip detectors with an energy resolution of 62 eV at 6 keV, and hope to improve this substantially. We will also report on our progress towards optical arrays for a planned camera for the Palomar 200″ telescope.     

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.     

The effect of cathode bias (field effect) on the surface leakage current of CdZnTe detectors

Surface resistivity is an important parameter of multi-electrode CZT detectors such as coplanar-grid, strip, or pixel detectors. Low surface resistivity results in a high leakage current and affects the charge collection efficiency in the areas near contacts. Thus, it is always desirable to have the surface resistivity of the detector as high as possible. In the past the most significant efforts were concentrated to develop passivation techniques for CZT detectors. However, as we found, the field-effect caused by a bias applied on the cathode can significantly reduce the surface resistivity even though the detector surface was carefully passivated. In this paper we illustrate that the field-effect is a common feature of the CZT multi-electrode detectors, and discuss how to take advantage of this effect to improve the surface resistivity of CZT detectors.     

Position Resolution in DROIDs

Since the very beginning, Distributed Read-Out Imaging Devices (DROIDs) were proposed to achieve both good position and energy resolutions. In DROIDs, the absorption of primary particle energy occurs in a long superconductive strip. Quasiparticles produced in the absorber diffuse along the strip and counted by the superconductive tunnel junctions positioned at the two ends of the strip. In this paper the formula for estimation DROID’s position resolution from experimental data was derived. This formula takes into account correlation between fluctuations of signals of DROID’s detectors.      

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.     

Position-Sensitive Spectrometric Module for Detecting Ionizing Radiation by Semiconductor Strip Detectors

Technical Physics Letters - A position-sensitive module for detecting ionizing radiation based on semiconductor strip detectors and a multichannel spectrometric route has been developed and...     

Fragment detection system for studies of exotic neutron-rich nuclei

We have developed a fragment detection system for use in studies of exotic, neutron-rich nuclei. Using a C-shaped dipole magnet, the system sweeps charged fragments and un-reacted beam particles through an angle before stopping them in an array of plastic scintillator detectors, recording time-of-flight and total energy. The system also includes a pair of silicon strip detectors to measure fragment angle of emergence from the target and energy loss for particle identification.     

The charge collection in single side silicon microstrip detectors

The transient current technique has been used to investigate signal formation in unirradiated silicon microstrip detectors, which are similar in geometry to those developed for the ATLAS experiment at LHC. Nanosecond pulsed infrared and red lasers were used to induce the signals under study. Two peculiarities in the detector performance were observed: an unexpectedly slow rise to the signal induced in a given strip when signals are injected opposite to the strip, and a long duration of the induced signal in comparison with the calculated drift time of charge carriers through the detector thickness—with a significant fraction of the charge being induced after charge carrier arrival. These major effects and details of the detector response for different positions of charge injection are discussed in the context of Ramo's theorem and compared with predictions arising from the more commonly studied phenomenon of signal formation in planar pad detectors.     

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.     

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.     

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.     

Functional properties of microstrip Si detector structures with implanted p-n junctions

The basic properties of microstrip Si detector structures with p-n junctions and the technological procedures for their production are described. Some results of manufacturing strip detectors with 200 μm and 20 μm strips are presented.     

Compton imager using room temperature silicon detectors

We have been developing a multi-layer Compton Gamma Ray Imager using position-sensitive, intrinsic silicon detectors. Advantages of this approach include room temperature operation, reduced Doppler broadening, and use of conventional silicon fabrication technologies. We have obtained results on the imaging performance of a multi-layer instrument where each layer consists of a 2×2 array of double-sided strip detectors. Each detector is 63 mm×63 mm×2 mm thick and has 64 strips providing a strip pitch of approximately 0.9 mm. The detectors were fabricated by SINTEF ICT (Oslo Norway) from 100 mm diameter wafers. The use of large arrays of silicon detectors appears especially advantageous for applications that require excellent sensitivity, spectral resolution and imaging such as gamma ray astrophysics, detection of special nuclear materials, and medical imaging. The multiple Compton interactions (three or more) in the low-Z silicon enable the energy and direction of the incident gamma ray to be determined without full deposition of the incident gamma-ray energy in the detector. The performance of large volume instruments for various applications are presented, including an instrument under consideration for NASA's Advanced Compton Telescope (ACT) mission and applications to Homeland Security. Technology developments that could further extend the sensitivity and performance of silicon Compton Imagers are presented, including the use of low-energy (few hundred keV) electron tracking within novel silicon detectors and the potential for a wafer-bonding approach to produce thicker, position-sensitive silicon detectors with an associated reduction of required electronics and instrument cost.     

A comparison of the performance of irradiated p-in-n and n-in-n silicon microstrip detectors read out with fast binary electronics

Both n-strip on n-bulk and p-strip on n-bulk silicon microstrip detectors have been irradiated at the CERN PS to a fluence of 3×10¹⁴ pcm⁻² and their post-irradiation performance compared using fast binary readout electronics. Results are presented for test beam measurements of the efficiency and resolution as a function of bias voltage made at the CERN SPS, and for noise measurements giving detector strip quality. The detectors come from four different manufacturers and were made as prototypes for the SemiConductor Tracker of the ATLAS experiment at the CERN LHC.     

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.     

A WIMP Dark Matter Detector Using MKIDs

We are pursuing the development of a phonon- and ionization-mediated WIMP dark matter detector employing microwave kinetic inductance detectors (MKIDs) in the phonon-sensing channel. Prospective advantages over existing detectors include: improved reconstruction of the phonon signal and event position; simplified readout wiring and cold electronics; and simplified and more reliable fabrication. We have modeled a simple design using available MKID sensitivity data and anticipate energy resolution as good as existing phonon-mediated detectors and improved position reconstruction. We are doing preparatory experimental work by fabricating strip absorber architectures. Measurements of diffusion length, trapping efficiency, and MKID sensitivity with these devices will enable us to design a 1 cm²×2 mm prototype device to demonstrate phonon energy resolution and position reconstruction.      

Development of readout electronics for monolithic integration with diode strip detectors

Parallel in-serial out analog readout electronics integrated with silicon strip detectors will bring a reduction of two orders of magnitude in external electronics. The readout concept and the chosen CMOS technology solve the basic problem of low noise and low power requirements. A hybrid solution is an intermediate step towards the final goal of monolithic integration of detector and electronics.     

A Si strip detector with integrated coupling capacitors

A silicon microstrip detector with capacitive coupling of the diode strips to the metallization and with individual polysilicon resistors to each diode has been developed. The detector was tested in a minimum ionizing particle beam showing a performance similar to conventional strip detectors and a spatial resolution of 3.5 μm. Capacitive coupling allows the decoupling of the leakage current from the input to the charge sensitive preamplifier especially in the case of LSI electronics.     

Rohacell foam as a silicon support structure material for the PHENIX multiplicity vertex detector

Rohacell [1], a low-density rigid foam, has been investigated as a support structure material for silicon strip detectors in the Multiplicity Vertex Detector (MVD) in the PHENIX experiment. Although Rohacell is susceptible to changes in humidity, tests have shown that it is an acceptable material for the MVD silicon support structure. The advantage of using Rohacell is that it offers a mechanically robust structure in which secondary interactions are minimized.