Algorithms have been studied using Monte Carlo techniques and implemented in a fast Xilinx Virtex II pro field programmable gate array (FPGA), in order to calculate and remove, after pedestal ...subtraction, the common mode of a group of adjacent channels. The implementation of the algorithms has been optimized both for speed and minimal FPGA resources, so as to be used in multi-channel applications. The aim of this work is to define the optimum algorithm for common mode calculation to be implemented for common mode rejection in the CMS Preshower detector.
The CMS preshower is a fine grain detector that comprises 4288 silicon sensors, each containing 32 strips. The raw data are transferred from the detector to the counting room via 1208 optical fibres. ...Each fibre carries a 600-byte data packet per event. The maximum average level-1 trigger rate of 100 kHz results in a total data flow of ~72 GB/s from the preshower. For the readout of the preshower, 56 links to the CMS DAQ have been reserved, each having a bandwidth of 200 MB/s (2 kB/event). The total available downstream bandwidth of GB/s necessitates a reduction in the data volume by a factor of at least 7. A modular VME-based system is currently under development. The main objective of each VME board in this system is to acquire on-detector data from at least 22 optical links, perform on-line data reduction and pass the concentrated data to the CMS DAQ. The principle modules that the system is based on are being developed in collaboration with the TOTEM experiment.
I-ImaS (Intelligent Imaging Sensors) is a European project aiming to produce new, intelligent X-ray imaging systems using novel APS sensors to create optimal diagnostic images. Initial systems have ...been constructed for medical imaging; specifically mammography and dental encephalography. However, the I-ImaS system concept could be applied to all areas of X-ray imaging, including homeland security and industrial QA. The I-ImaS system intelligence is implemented by the use of APS technology and FPGAs, allowing real-time analysis of data during image acquisition. This gives the system the capability to perform as an on-the-fly adaptive imaging system, with the potential to create images with maximum diagnostic information within given dose constraints. The I-ImaS system uses a scanning linear array of scintillator-coupled 1.5-D CMOS Active Pixel Sensors to create a full 2-D X-ray image of an object. This paper describes the parameters considered when choosing the scintillator elements of the detectors. A study of the positioning of the sensors to form a linear detector is also considered, along with a discussion of the potential losses in image quality associated with creating a linear sensor by tiling many smaller sensors. Preliminary results show that the detectors have sufficient performance to be used successfully in the initial mammographic and encephalographic I-ImaS systems that are currently under construction.
2D silicon strip sensors using particle physics readout technology have been evaluated as mammographic detectors. Two different versions of the APV series of front-end electronics were used that ...provided different noise levels. The sensors were evaluated using a typical mammography X-ray spectrum. The spatial resolution was evaluated using line pair test patterns and the modulation transfer function (MTF) was measured using the Edge Response Function. Low contrast performance was measured using the TOR(MAX) test object. Limiting spatial resolution of
52
μm
was obtained and an MTF value of 0.1 at
16
lp/
mm
. The low contrast performance was estimated from 250,
500
μm
and
6
mm
diameter objects and was found to be 11.5%, 7% and better than 3.8%, respectively.
Digital X-ray imaging using silicon microstrip detectors: a design study Speller, R.D; Royle, G.J; Triantis, F.A ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
01/2001, Letnik:
457, Številka:
3
Journal Article
Recenzirano
This paper considers the basic design parameters for using silicon microstrip detectors for 2-D medical imaging. In particular, mammographic and dental imaging are considered. Monte Carlo modeling ...techniques have been used to investigate detector efficiency, strip pitch, image quality, imaging geometry and signal processing requirements. Different phantoms are used for each part of the study. It is shown that signal processing times are a major factor in the operation of a clinical detector system if ambiguities are to be avoided in a double-sided strip detector. However, the use of the models allows conclusions to be made that alleviate the timing requirements. It has been shown that using a strip structure of 50–100
μm provides appropriate image resolution and image quality can be maintained with pixel counts of 50–100 in both dental and mammographic work. Under these conditions current front-end electronics designs can provide the signal processing times with an acceptably small number of multihit events (<5%).
Abstract I-ImaS (Intelligent Imaging Sensors) is a European project aiming to produce real-time adaptive X-ray imaging systems using Monolithic Active Pixel Sensors (MAPS) to create images with ...maximum diagnostic information within given dose constraints. Initial systems concentrate on mammography and cephalography. In our system, the exposure in each image region is optimised and the beam intensity is a function of tissue thickness and attenuation, and also of local physical and statistical parameters in the image. Using a linear array of detectors, the system will perform on-line analysis of the image during the scan, followed by optimisation of the X-ray intensity to obtain the maximum diagnostic information from the region of interest while minimising exposure of diagnostically less important regions. This paper presents preliminary images obtained with a small area CMOS detector developed for this application. Wedge systems were used to modulate the beam intensity during breast and dental imaging using suitable X-ray spectra. The sensitive imaging area of the sensor is 512 × 32 pixels 32 × 32 μm2 in size. The sensors' X-ray sensitivity was increased by coupling to a structured CsI(Tl) scintillator. In order to develop the I-ImaS prototype, the on-line data analysis and data acquisition control are based on custom-developed electronics using multiple FPGAs. Images of both breast tissues and jaw samples were acquired and different exposure optimisation algorithms applied. Results are very promising since the average dose has been reduced to around 60% of the dose delivered by conventional imaging systems without decrease in the visibility of details.
Noise measurements on Si sensors Evangelou, I; Kokkas, P; Manthos, N ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2002, Letnik:
493, Številka:
1
Journal Article
Recenzirano
Developing silicon strip sensors for the CMS Preshower detector we have noticed that some strips have a noise higher than the average and not correlated to a high leakage current. In order to ...investigate this effect we have developed a set-up for noise measurement on wafers and diced sensors that does not require bonding. The set-up is based on the DeltaStream chip coupled to a probe card. We have tested 45 sensors and found that the strips with an above average noise have a higher relative current increase as a function of voltage, Δ
I/(
IΔ
V). We also observed that, on these strips, the breakdown occurs within about
60
V
from the voltage at which the noise is observed. We describe our measurement method and present the results.
Low noise high-speed X-ray readout IC for imaging applications Tsakas, E.F.; Birbas, A.N.; Manthos, N. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2001, Letnik:
469, Številka:
1
Journal Article
Recenzirano
We present a mixed-signal, continuously sensitive, self-triggered IC designed for X-ray imaging applications. Both bipolar and CMOS devices were employed in order to achieve the speed and noise ...requirements associated with the particular application. Phenomena related to the submicron nature of the devices used have been also taken into consideration. The circuit is optimized to operate with a 3
pF Si-microstrip detector and it exhibits an equivalent noise charge of 225e
− rms with a slope of 45e
−/pF. The peaking time of the pulse at the output of the analog part is 28
ns and the circuit recovers to the baseline within 600
ns. Moreover, it has the ability of handling either positive or negative current pulses originating from the detector. The IC power consumption is 4.5
mW per channel and the chip was fabricated using a 0.8
μm BiCMOS technology.
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