Miguel Sofo Haro

Commercial CMOS pixel array for beta and gamma radiation particle counting

We present the response of a Commercial-Off-The-Shelf (COTS) CMOS image sensor to different ionizing particles, with the aim of developing a low cost radiation detector. We first analyze the images obtained by exposing the imagers to X-rays from 55Fe, gamma and beta particles from 137Cs. Then the detector is successfully used to monitor different gamma fluxes produced by the RA6 nuclear research reactor, Argentina, during a startup procedure.

Analysis of SRAM-Based FPGA SEU Sensitivity to Combined EMI and TID-Imprinted Effects

This work proposes a novel methodology to evaluate SRAM-based FPGAs susceptibility with respect to Single-Event Upset (SEU) as a function of noise on VDD power pins, TotalIonizing Dose (TID) and TID-imprinted effect on BlockRAM cells. The proposed procedure is demonstrated for SEU measurements on a Xilinx Spartan 3E FPGA operating in an 8 MV Pelletron accelerator for the SEU test with heavy-ions, whereas TID was deposited by means of a Shimadzu XRD-7000 X-ray diffractometer. In order to observe the TID-induced imprint effect inside the BlockRAM cells, a second SEU test with neutrons was performed with Americium/Beryllium (241AmBe). The noise was injected into the power supply bus according to the IEC 61.000-4-29 standard and consisted of voltage dips with 16.67% and 25% of the FPGAs VDD at frequencies of 10 Hz and 5 kHz, respectively. At the end of the experiment, the combined SEU failure rate, given in error/bit.day, is calculated for the FPGAs BlockRAM cells. The combined failure rate is defined as the average SEU failure rate computed before and after exposition of the FPGA to the TID.

Measurement of the read-out noise of fully depleted thick CCDs

Fully depleted thick CCDs have been designed for infrared astronomy, but their low read-out noise of the order of ≈2e- and their considerable mass of ≈5.2 gr, allows novel uses for them in low energy threshold particle detection applications, such as the CONNIE and DAMIC experiments. For both experiments, a reduction of the CCD read-out noise is vital. In this work we present a method to measure the read-out noise coming from electronic and non-electronic sources. The impact of the external electronics on the noise is discussed and its full characterization is presented.

X-ray micrographic imaging system based on COTS CMOS sensors

This paper presents the use of Commercial Off The Shelf CMOS image sensors for the acquisition of X-ray images with high spatial resolution. The X-ray images, with application in biology, electronic components inspection or paleontology research, are obtained with 8 keV photons from a Cu tube. The quantum efficiency of the detector is estimated using attenuation lengths of photons in the sensor, and compared to traditional scintillator conversion layers.

Aspects on the shape dependence with energy of point-like events in high resistivity CCDs

Fully depleted thick CCDs have been designed for infrared astronomy, but their low read-out noise of the order of approximately 2 e− and their considerable mass of approximately 5.2 gr, allows novel uses for them in low energy threshold particle detection applications, such as the CONNIE and DAMIC experiments. In both experiments, the neutrinos or WIMPS will generate e-h pairs in a volume much less than the pixel size, they will produce events like points in the output image, of less than 10 pixels. Is well understood that one of the factors that define the size of the events is the diffusion process. In this work we will demonstrate with experimental results and through simulation, that there is also a dependence of the size with the amount of charge generated by the event, due to charge repulsion effects.

Taking the CCDs to the ultimate performance for low threshold experiments

Scientific grade CCDs show atractive capabilities for the detection of particles with small energy deposition in matter. Their very low threshold of approximately 40 eV and their good spatial reconstruction of the event are key properties for currently running experiments: CONNIE and DAMIC. Both experiments can benefit from any increase of the detection efficiency of nuclear recoils at low energy. In this work we present two different approaches to increase this efficiency by increasing the SNR of events. The first one is based on the reduction of the readout noise of the device, which is the main contribution of uncertainty to the signal measurement. New studies on the electronic noise from the integrated output amplifier and the readout electronics will be presented together with result of a new configuration showing a lower limit on the readout noise which can be implemented on the current setup of the CCD based experiments. A second approach to increase the SNR of events at low energy that will be presented is the studies of the spatial conformation of nuclear recoil events at different depth in the active volume by studies of new effects that differ from expected models based on not interacting diffusion model of electrons in the semiconductor.