Jacques Lecoq

An Optimal Filter Based Algorithm for PET Detectors With Digital Sampling Front-End

With the development of fast sampling electronics, digital pulse processing techniques for PET signals are raising interest. The optimal filter (OF) algorithm reconstructs pulse amplitude and time by two weighted sums, making it compatible with real-time implementation. The filters are usually optimized for stationary noise. We developed and tested a method to optimize the filters for the nonstationary noise of scintillation pulses. It is based on offline statistical analysis of coincident waveforms that could be applied during the system initialization phase. Experimental tests were done on a coincidence setup with two detection blocks composed of a fast inorganic scintillator ( LaBr3 or LYSO) coupled to a photodetector (APD or PMT), preamplifiers and prefilters. The signals were sampled at high rate (250 MHz for APDs, 5 GHz for PMTs) and treated offline. The optimization of the filter coefficients for nonstationary noise yielded a significant improvement compared to those optimized for stationary noise, resp. 368 ps and 632 ps fwhm in coincidence for the LYSO-PMT setup. However, little improvement was achieved compared to leading-edge (DLED) and constant fraction (DCFD) discriminator algorithms (resp. 419 ps, 435 ps fwhm). Indeed, the adjustment of thresholds can be interpreted as an optimization for nonstationary noise. Yet, OF is more robust to white noise than DLED or DCFD. The applicability to PET is discussed.

Photomultiplier pulse Read Out system for the preshower detector of the LHCb experiment

Abstract The second generation experiment for CP violation studies in B decays, LHCb, is a 20-m-long single-arm spectrometer to be installed on the future Large Hadron Collider at CERN. For its precision measurement purpose, it combines precise vertex location and particle identification, in addition to a performance trigger system able to cope with high flux. The first level of trigger is mainly based on the fast response of the calorimetric subsystem. Of major importance is the 6000 channels preshower detector that aims to validate the electromagnetic nature of calorimetric showers. It consists of two-radiation-length lead sheet in front of a scintillator plane. Scintillator signals are extracted from plastic cells using wavelength-shifting fibres coupled to multi-anode photomultiplier tubes. The preshower Read Out system has to cope with fluctuating photomultiplier pulses caused by small amounts of photoelectrons, in addition to strong constraints imposed by the 40 MHz LHC bunch-crossing frequency. A special Read Out electronics including perfect 40 MHz integrators able to shape fluctuating photomultiplier pulses has been designed, and successfully realized. The temporal shape of photomultiplier pulse and the upstream Read Out system for preshower are described in this document.

Toward a Low Cost and Single Chip Holter: SoC-Holter

In spite of the rapid development of medicine, cardiovascular diseases are still the number one killer in the world. In France every year more than 50,000 people die suddenly due cardiac arrhythmias. Identification of high risk sudden death patient is still a challenge. To detect the cardiac arrhythmias, currently Holter is generally used to record 1~3 leads ECG (electrocardiogram) signals during 24h to 72h. However the use of Holter is limited among the population due to its form factor (not user-friendly) and cost. In this paper, we propose an integrated single chip wearable Holter named SoC-Holter, which enables to record 1~4 leads ECG. This single chip SoC-Holter is relied on adequation algorithm architecture design methodology. To minimize energy consumption, CMOS technology (0.35µm) is used to prototype the first implementation and test. The SoC-Holter has the following functions: signal conditioner and preamplifier, amplifier and filters, analog to digital converter, and Nano-controller. The low pass filter is composed of current division, degeneration and common-mode feedback circuits added to fulfill the required performance. The analog circuits are implemented, tested and validated. The digital bloc is simulated, implemented and tested. It seems that an integrated, low cost, and user-friendly single chip Holter is feasible. Consequently large number of high risk populations such as heavy smoker and obese may be monitored. This SoC-Holter consumes less than 10mW while the device is operating.

A Very-Front-End ADC for the Electromagnetic Calorimeter of the International Linear Collider

A 10-bit pipeline analog-to-digital converter is introduced in this paper and the measurements carried out on prototypes produced in a 0.35 m CMOS technology are presented. This ADC is a building block of the very-front-end electronics dedicated to the electromagnetic calorimeter of the International Linear Collider (ILC). Based on a 1.5-bit per stage resolution architecture, it reaches the 10-bit accuracy at a sampling rate of 4 MSamples/s with a consumption of 35 mW. The Integral and Differential Non-Linearity obtained are respectively within LSB and LSB, and the measured noise is 0.47 LSB r.m.s. The performance obtained confirms that the pipeline architecture ADC is suitable to the requirements of the readout electronics of the electromagnetic calorimeter.