Inter-strip Region Research Articles

Evaluation of characteristics of Hamamatsu low-gain avalanche detectors

Low-gain avalanche detectors (LGADs) are attractive because of their fast response to realize a 4-dimensional (4D) tracker in future experiments in high energy physics and other applications. We fabricated LGAD diodes and strip sensors. Their responses before and after irradiation to gamma rays or neutrons were evaluated with light-emitting diodes (LEDs) of various wave lengths and with an infrared laser. The sensors showed a gain of more than 10 before irradiation. Little reduction of gain was observed with gamma irradiation. A substantial reduction of gain was observed after neutron irradiation. A gain increase observed in the interstrip region after neutron irradiation, whereas the gain was equal to one before irradiation.

Charge Collection Efficiency in a segmented semiconductor detector interstrip region

Charged particle semiconductor detectors have been used in Ion Beam Analysis (IBA) for over four decades without great changes in either design or fabrication. However one area where improvement is desirable would be to increase the detector solid angle so as to improve spectrum statistics for a given incident beam fluence. This would allow the use of very low fluences opening the way, for example, to increase the time resolution in real-time RBS or for analysis of materials that are highly sensitive to beam damage. In order to achieve this goal without incurring the costs of degraded resolution due to kinematic broadening or large detector capacitance, a single-chip segmented detector (SEGDET) was designed and built within the SPIRIT EU infrastructure project. In this work we present the Charge Collection Efficiency (CCE) in the vicinity between two adjacent segments focusing on the interstrip zone. Microbeam Ion Beam Induced Charge (IBIC) measurements with different ion masses and energies were used to perform X-Y mapping of (CCE), as a function of detector operating conditions (bias voltage changes, detector housing possibilities and guard ring configuration). We show the (CCE) in the edge region of the active area and have also mapped the charge from the interstrip region, shared between adjacent segments. The results indicate that the electrical extent of the interstrip region is very close to the physical extent of the interstrip and guard ring structure with interstrip impacts contributing very little to the complete spectrum. The interstrip contributions to the spectra that do occur, can be substantially reduced by an offline anti-coincidence criterion applied to list mode data, which should also be easy to implement directly in the data acquisition software.

Effects of the interstrip gap on the efficiency and response of Double Sided Silicon Strip Detectors

In this work the effects of the segmentation of the electrodes of Double Sided Silicon Strip Detectors (DSSSDs) are investigated. In order to characterize the response of the DSSSDs we perform a first experiment by using tandem beams of different energies directly sent on the detector and a second experiment by mean of a proton microbeam. Results show that the effective width of the inter-strip region and the efficiency for full energy detection, varies with both detected energy and bias voltage. The experimental results are qualitatively reproduced by a simplified model based on the Shockley-Ramo-Gunn framework.

Study of interstrip gap effects and efficiency for full energy detection of Double Sided Silicon Strip Detectors

In this work is reported a study on the response of double sided silicon strip detectors. In order to investigate the effect of the electrode segmentation on the detector response, two experiments were performed aimed to measure the efficiency for full energy detection. Results show that the efficiency for full energy detection, that is directly related to effective width of the inter-strip region, varies with both detected ion energy and bias voltage. The experimental results are qualitatively reproduced by a simplified model based on the Shockley-Ramo-Gunn framework.

Laser mapping of the inter-strip response in double sided silicon strip detectors for particle identification

Silicon microstrips are widely used in nuclear physics experiments when high granularity and high resolution is required (e.g. particle-particle correlation). In addition microstrip detectors are used in the field of X-ray detection for position resolved X-ray spectroscopy. In the framework of the construction of a novel Femtoscope ARray for Correlation and Spectroscopy, named FARCOS, we are performing a thorough characterization of the silicon detector layers in terms of the efficiency and charge collection properties as a function of the point of incidence and type of interaction. We have experimental evidence—as previously observed also in the literature for other strip detectors—that inter-strip incidence alters the signal shape not only for the trivial charge division but also affecting the shape of the induced signal on neighbor strips. The phenomenon can be more or less pronounced depending on the energy and ion type but it is always present. In order to surgically probe the response of the inter-strip region we tested the detector both in back and in front injection with an infrared pulsed laser at two different wavelengths (705 nm and 904 nm). Depending on the side of interaction, on the position of incidence and on the absorption length, the shapes of the induced signals are significantly altered and signals of opposite polarity or bipolar signals arise. In order to get a complete picture of the physical phenomena at the basis of the aforementioned behavior we performed detailed 3D device simulations with a custom semi-analytical code and compared the results with the experimental data. The paper focuses on the description of the experimental measurements and their exhaustive description and interpretation.

P-Bulk silicon microstrip sensors and irradiation

Anticipating the requirement for highly radiation-tolerant silicon microstrip sensors suitable for the SLHC application, we have fabricated n-in-p microstrip sensors in p-FZ and p-MCZ industrial wafers which we then irradiated with 70 MeV protons. Studies were made of the leakage current, onset of microdischarge, body capacitance, charge collection efficiency, and n-strip isolation at the fluences of nil, 0.7×10 14, and 7×10 14 1-MeV neutrons equivalent (neq)/cm 2. The bias and edge structure achieved holding the bias voltages up to 1000 V. The full depletion voltages were about 160, 250, and 600 V in the p-FZ and 1190, 500, and 840 V in the p-MCZ at nil, low, and high fluences, respectively. The radiation damage helped to reduce the density of electron accumulation layer. The strip isolation in the p-MCZ sensors was found to be much better than in the p-FZ sensors; even the no-isolation structure isolated the strips at nil fluence at bias voltage above 50 V. The lower density of electron accumulation layer in the p-MCZ could be attributed to an order less interface trap density in the 〈1 0 0〉 surface than that of 〈1 1 1〉, the negative potential in the inter-strip region by the bias voltage, and the possible effect of high oxygen content in the MCZ bulk.

Performance of irradiated [formula omitted]-on- [formula omitted] silicon microstrip sensors

The silicon microstrip detector type with n + readout fabricated on p bulk, n + -on- p , is a candidate to be operational in radiation environments much severer than in LHC. We characterized n + -on- p detectors which were irradiated up to 1.1 × 10 14 protons / cm 2 10 years ago. The noise level and charge collection were evaluated using the ATLAS SCT readout electronics system. Radiation-induced increase in the noise and loss in the charge collection are not significant. The charge collection is not degraded in any particular point in the inter-strip region when the detector is operated under partial depletion.

Silicon sensors for the CMS preshower detector

This paper is a summary of a research and development programme, conducted during the past 3 years on the CMS Preshower silicon sensors to define the specifications. The main purpose was to study the radiation hardness of these devices resulting from the specific design (metal lines wider than the p + implants) and the production technology, a deep n + layer on the ohmic side. An acceptable noise and a uniform charge collection were guaranteed by an appropriate choice of the interstrip region width. About 65 sensors, of different designs and produced by six manufacturers, were irradiated with neutrons and protons and thoroughly tested before and after irradiation. The results of the tests and the final specifications are presented.