Vaclav Kraus

FITPix — fast interface for Timepix pixel detectors

The semiconductor pixel detector Timepix contains an array of 256 × 256 square pixels with pitch 55 μm. In addition to high spatial granularity the single quantum counting detector Timepix can provide also energy or time information in each pixel. This device is a powerful tool for radiation and particle detection, imaging and tracking. A new readout interface for silicon pixel detectors of the Medipix family has been developed in our group in order to provide a higher frame rate and enhanced flexibility of operation. The interface consists of a field programmable gate array, a USB 2.0 interface chip, DAC, ADC and a circuit which generates bias voltage for the sensor. The main control system is placed in the FPGA circuit which fully controls the Timepix device. This approach offers an easy way how to include new functionality and extended operation. The interface for Timepix supports all operation modes of the detector (counting, TOT, timing). The FITPix is a successor of the USB 1.22 Interface and the electronic readout is built with the latest available components, which allows achieving up to 90 frames per second with a single detector. The frame rate is about 20 times faster compared to the previous system while it maintains all same capabilities supported. In addition FITPix newly enables an adjustable clock frequency and hardware triggering which is a useful tool when there is the need for synchronized operation of multiple devices. Three modes of hardware trigger have been implemented: hardware trigger which starts the measurement, hardware trigger which terminates the measurement and hardware trigger which controls measurement fully. The entire system is fully powered through the USB bus. FITPix supports also readout from several detectors in chain in which case just an external power source is required. FITPix is a fully flexible device and the user needs no other equipment. FITPix combines high performance and mobility and it opens new fields of applications. The current version of the FITPix interface has dimension 45 mm × 60 mm.

Spatially correlated and coincidence detection of fission fragments with the pixel detector Timepix

Charged-particle coincidence correlated measurements such as angular correlations between rare and main fission fragments measured with conventional detectors provide only partial and limited information (energy cutoff, narrow range of studied ion Z numbers). Many of these drawbacks arise from the standard solid state detectors used so far which can be solved simultaneously by usage of highly segmented single-quantum counting pixel detectors. The Timepix pixel device, which is equipped with energy and time sensitivity capability per pixel, provides high granularity, wide dynamic range and per pixel threshold. This detector operated with integrated USB-readout interfaces such as the USB 1.0 and FITPix devices and the data acquisition software tool Pixelman, both developed for the pixel detectors of the Medipix-family, enables a variety of instrumental configurations, visualization, real-time event-by-event selection as well as vacuum and portability of operation for flexible measurements on different targets and setups. These features combined with event track analysis provide enhanced signal to noise ratio with a high suppression of background and unwanted events. The detector provides multi-parameter information (position, energy and time) for basically all types of ionizing particles in a wide dynamic range of energy (pixel energy threshold ≈ 4 keV), interaction/arrival time (timepix clock step ≥ 100 ns) and position (pixel size = 55 μm). High selectivity is achieved by spatial and time correlation in the same sensor. In addition, several detectors can be run in coincidence. The open and close exposition (shutter) time as well as the readout DAQ can be fully synchronized. For this purpose, we have assembled a modular multi-parameter, tunable and extendable coincidence detector array system based on two and more Timepix devices which can be coupled with supplementary detectors (solid state ΔE detectors and/or ionization chambers) for enhanced ion selectivity. We describe the individual configurations and techniques together with the experiments carried out at several neutron beam/source facilities. We summarize the results and capabilities of application.

Modular pixelated detector system with the spectroscopic capability and fast parallel read-out

A modular pixelated detector system was developed for imaging applications, where spectroscopic analysis of detected particles is advantageous e.g. for energy sensitive X-ray radiography, fluorescent and high resolution neutron imaging etc. The presented system consists of an arbitrary number of independent versatile modules. Each module is equipped with pixelated edgeless detector with spectroscopic ability and has its own fast read-out electronics. Design of the modules allows assembly of various planar and stacked detector configurations, to enlarge active area or/and to improve detection efficiency, while each detector is read-out separately. Consequently read-out speed is almost the same as that for a single module (up to 850 fps). The system performance and application examples are presented.

FITPix data preprocessing pipeline for the Timepix single particle pixel detector

The semiconductor pixel detector Timepix contains an array of 256 ? 256 square pixels with a pitch of 55 ?m. The single quantum counting detector Timepix can also provide information about the energy or arrival time of a particle from every single pixel. This device is a powerful tool for radiation imaging and ionizing particle tracking. The Timepix device can be read-out via a serial or parallel interface enabling speeds of 100 fps or 3200 fps, respectively. The device can be connected to a PC via the USB 2.0 based interface FITPix, which currently supports the serial output of Timepix reaching a speed of 90 fps. FITPix supports adjustable clock frequency and hardware triggering which is a useful tool for the synchronized operation of multiple devices. The FITPix interface can handle up to 16 detectors in daisy chain. The complete system including the FITPix interface and Timepix detector is controlled from the PC by the Pixelman software package. A pipeline structure is now implemented in the new version of the readout interface of FITPix. This version also supports parallel Timepix readout. The pipeline architecture brings the possibility of data preprocessing directly in the hardware. The first pipeline stage converts the raw Timepix data into the form of a matrix or stream of pixel values. Another stage performs further data processing such as event thresholding and data compression. Complex data processing currently performed by Pixelman in the PC is significantly reduced in this way. The described architecture together with the parallel readout increases data throughput reaching a higher frame-rate and reducing the dead time. Significant data compression is performed directly in the hardware especially for sparse data sets from particle tracking applications. The data frame size is typically compressed by factor of 10-100.

Influence of electromagnetic interference on the analog part of hybrid Pixel detectors

The analog signal from the sensor of hybrid semiconductor pixel detectors is prone to electro-magnetic interference. The study and diagnosis of induced and common electro-magnetic coupling between the analog part and digital part of these devices is required. The influence of electro-magnetic interference was tested on the setup with a pixel detector Timepix or Medipix and a FITPix read-out interface. Measurements were carried out of external as well as internal interference. We evaluated the influence of both sources of electro-magnetic interference to the noise recorded by pixels. We measured the local spatial intensity distribution and frequency spectrum of the electro-magnetic field originating inside the readout chip during its own operation. In context of this test we exposed the detector chip to a locally generated artificial electro-magnetic field evaluating its sensitivity to induced interference. Consequently, the whole setup of the detector and read-out interface was exposed to a distant source of electro-magnetic radiation, during which we tested efficiency of the electro-magnetic shielding of various arrangements. Further, tests measured the coupling over power supply lines. In particular, the noise generated by the operation of the detector itself was determined. In addition, the detector sensitivity to deliberately induced noise was evaluated. By means of these tests weak points of the setup sensitive to the intrusion of electro-magnetic interference are revealed. When locations of susceptible places are identified proper methods can be applied to increase immunity of the detector setup against the electro-magnetic interference. Experiences gained are planned to be used in development of the EMI shielded version of the FITPIX interface shielded to electro-magnetic interference.

SPECTRIG — Device for triggering and spectroscopy with the pixelated particle detector

The Article deals with the precise timed measurement using the advanced pixelated particle detector. There is described a design of the extra device Spectrig that is dedicated to generate the additional trigger signal which enables utilization of detector capabilities in the single particle tracking and spectroscopy applications. The article also describes how the Spectrig device performs signal processing and how it is implemented.

Compact device for detecting single event effects in semiconductor components

The paper describes a compact system for detecting Single Event Effects (SEE) in semiconductor components. The SEE is caused by a hit into a electronic chip with an energetic particle. The hit can cause unexpected behaviour of the system. The tested component is called Device Under Test (DUT). The structure of the system is shown and used components are described with their main tasks. Some of results of the running system are shown.

Fast spectroscopic imaging with pixel semiconductor detector Timepix and parallel data reading

Non-invasive techniques utilizing X-ray radiation offer a powerful tool for the inspection of the inner composition of a wide variety of objects. The highly sensitive hybrid semiconductor pixel detector Timepix is capable of detecting and resolving subtle and low-contrast differences in radiography measurements. Moreover the Timepix detector offers 65536 individual pixels with spectrometric capabilities. With proper per-pixel energy calibration this feature enables the application of various energy based imaging techniques - from basic energy windowing to fully spectroscopic imaging. The main limitations of these methods are the detector energy resolution and data acquisition speed of 100 frames per second - the necessity of taking frames with low occupancy for event by event cluster analysis leads to several hours long measurements. The latter nuisance can be overcome by the utilization of the newly developed modular read-out FITPix3 with the adapter chipboard designed for parallel data reading. This read-out version can acquire over 850 compressed frames per second which reduces the measurement time of many spectroscopic measurements by factor of ten (spectra with high enough statistics are taken in tens of minutes). The short description of the new FITPix3 parallel read-out together with the progression in spectroscopic multi-channel energy imaging demonstrated on model samples are presented in this contribution.

The interface for the pixelated particle detector with the capability of the spectroscopy function and the coincidence measurement operation

An article describes design of the advanced interface primarily dedicated for the silicon pixelated particle detector of the Medipix family. The interface allows to gain information from the pixelated matrix and also to gain spectroscopy information from the common electrode of the pixelated detector. There is also described an implemented functionality enabling applications of the device in the coincidence measurement.

Overview of recent advances in hardware implementation of mathematical morphology

This paper surveys the state of the art of mathematical morphology from a perspective of algorithmic advances of the low-level morphological operators dilation and erosion as well as implementation of these algorithms in the dedicated hardware, such as FPGAs. The existing architectures are categorized in three groups: neighborhood processors, partial-result reuse, and efficient algorithm implementation. The performance of recent proposals was compared on an ASF filter application.