Sergio Zimmermann

Data Acquisition and Trigger System of the Gamma Ray Energy Tracking In-Beam Nuclear Array (GRETINA)

The Gamma Ray Energy Tracking In-Beam Nuclear Array (GRETINA), capable of determining the energy and position (within 2 mm) of each gamma-ray interaction point and tracking multiple gamma-ray interactions, has been designed. GRETINA will be composed of seven detector modules, each with four highly pure germanium crystals. Each crystal has 36 segments and one central contact instrumented by charge sensitive amplifiers. Two custom designed modules, the Digitizer/Digital Signal Processing (DSP) and the Trigger Timing and Control, compose the electronics of this system. The digitizer/DSP converts the analog information with 14-bit analog to digital converters operating at 100 MS/s, and digitally processes the data to determine the energy and timing information of the gamma interactions with the crystal. Each Digitizer/DSP is controlled by and sends trigger information to the Trigger Timing & Control system through a bidirectional Gbit link. Presently four different trigger algorithms are planned for the trigger system and can be selected for trigger decision. In this paper the details of the electronics and algorithms of the GRETINA data acquisition and trigger system are presented and the performance is reviewed.

A CPU, GPU, FPGA System for X-Ray Image Processing Using High-Speed Scientific Cameras

Currently, computers can be composed of different Processing Units (PUs) - general-purpose and also programmable and specialist-purpose. One of the goals for such heterogeneity is to improve applications performance. Particularly, scientific applications can highly benefit from this kind of platform. They produce large amounts of data within several types of algorithms, and distinct PUs are an alternative to better execute such tasks. This work presents a new system box - composed of CPU, GPU, and FPGA - to carry on site X-ray image evaluations. It was firstly tested by evaluating the performance of a Linear Integration (LI) algorithm over the PUs. This algorithm is largely used by synchrotron experiments in which high-speed X-ray cameras produce extremely large amounts of data for post-processing analysis, which includes performing LI. In our experiments, LI execution was around 30x faster in FPGA compared to CPU, achieving a similar performance to GPU. Taking the end-to-end application, i.e., image transfer into memory, this rate increases to hundreds. Issues for using FPGAs as a co-processor under our dynamic scheduling framework is also discussed. Synthesizing times for LI when assigned to FPGA are still too long for dynamic scheduling, preventing online synthesizing of functions not designed a priori.

Implementation and performance of the electronics and computing system of the Gamma Ray Energy Tracking In-Beam Nuclear Array (GRETINA)

The Gamma Ray Energy Tracking In-Beam Nuclear Array (GRETINA), a germanium detector system capable of measuring energy and position (within better than 2 mm rms) of gamma-ray interaction points and tracking multiple gamma-ray interactions, has been built. GRETINA is composed of seven detector modules, each with four high purity germanium crystals. Four custom designed electronics support the operation of the detectors: Digitizer/Digital Signal Processing (DSP), Trigger/Timing, Breakout Chassis and the Detector Interface Box. The Digitizer/DSP converts the analog information with 14-bit analog to digital converters operating at 100 MS/s, and digitally processes the data to determine the energy and timing information of the gamma interactions within a crystal. The computing system is composed of VME readout CPUs running VxWorks, which communicate with 62 dual-processor farm (each processor with four cores) through a 10 Gb/s Ethernet switch. The CPUs read out the digitizer/DSPs and send the data to the farm. The processors compute the position and track of the interactions of the gamma-ray inside the crystals. The processor farm is capable of processing in real-time the position of 20 000 gamma-ray/s. In this paper we will present the details of the implementation and performance of the electronics and computing system of GRETINA.

CDF run IIb silicon detector: electrical performance and deadtime-less operation

The main building block and readout unit of the planned CDF Run IIb silicon detector is a stave, a highly integrated mechanical, thermal, and electrical structure. One of its characteristic features is a copper-on-Kapton flexible cable for power, high voltage, data transmission, and control signals that is placed directly below the silicon microstrip sensors. The dense packaging makes deadtime-less operation of the stave a challenge since coupling of bus cable activity into the silicon sensors must be suppressed efficiently. The stave design features relevant for deadtime-less operation are discussed. The electrical performance achieved with stave prototypes is presented.

Shielding and electrical performance of silicon detector supermodules

A large detector structure, called a supermodule, was developed for the CDF Run IIb silicon strip detector. The supermodule is a compact mechanical, thermal, and electrical unit, which is ideally suited for construction and assembly of large volume detector systems. Its dense packaging requires careful suppression of possible electromagnetic interference due to power, clock, control, and data bus activity. We study the coupling of the magnetic fields caused by a clock signal through an aluminum shield into the silicon strips. Analytical and numerical calculations of the resulting interference signal are presented, and its shape and size are estimated. The calculations are in fair agreement with electrical performance measurements taken with final design supermodules. Calculations and measurements show that the interference effect can be effectively suppressed by a thin aluminum shield.

CDF run IIb silicon: design and testing

The various generations of Silicon Vertex Detectors (SVX, SVX, SVXII) for Collider Detector at Fermilab (CDF) at the Fermilab Tevatron have been fundamental tools for heavy-flavor tagging via secondary vertex detection. The CDF Run IIb Silicon Vertex Detector (SVXIIb) has been designed to be a radiation-tolerant replacement for the currently installed SVXII because SVXII was not expected to survive the Tevatron luminosity anticipated for Run IIb. One major change in the new design is the use of a single mechanical and electrical element throughout the array. This element, called a stave, carries six single-sided silicon sensors on each side and is built using carbon fiber skins with a high thermal conductivity on a foam core with a built-in cooling channel. A Kapton bus cable carries power, data and control signals underneath the silicon sensors on each side of the stave. Sensors are read out in pairs via a ceramic hybrid glued on one of the sensors and equipped with four SVX4 readout chips. This new design concept leads to a very compact mechanical and electrical unit, allowing streamlined production and ease of testing and installation. A description of the design and mechanical performance of the stave is given. Results on the electrical performance obtained using prototype staves are also presented.

Data acquisition and trigger system of the Gamma Ray Energy Tracking In-Beam Nuclear Array (GRETINA)

The Gamma Ray Energy Tracking In-Beam Nuclear Array (GRETINA), capable of determining the energy and position (within 2 mm) of each gamma-ray interaction point and tracking multiple gamma-ray interactions, has been designed. GRETINA will be composed of seven detector modules, each with four highly pure germanium crystals. Each crystal has 36 segments and one central contact instrumented by charge sensitive amplifiers. Two custom designed modules, the Digitizer/Digital Signal Processing (DSP) and the Trigger Timing and Control, compose the electronics of this system. The digitizer/DSP converts the analog information with 14-bit analog to digital converters operating at 100 MS/s, and digitally processes the data to determine the energy and timing information of the gamma interactions with the crystal. Each Digitizer/DSP is controlled by and sends trigger information to the Trigger Timing & Control system through a bidirectional Gbit link. Presently four different trigger algorithms are planned for the trigger system and can be selected for trigger decision. In this paper the details of the electronics and algorithms of the GRETINA data acquisition and trigger system are presented and the performance is reviewed.

Modeling and simulation of a readout architecture for pixel detectors

This paper analyzes in detail some theoretical aspects in the modeling of a proposed readout architecture for pixel detectors. The readout architecture is designed for a chip containing about 3000 pixels of 50 /spl mu/m/spl times/400 /spl mu/m. The main objective is to get the maximum pixel hit readout with the minimum probability of hit loss. The readout architecture is modeled as a Markov stochastic process. The pixel front-end and readout are simulated and tested with Monte Carlo data. The simulations allow to optimize the communication channel bandwidths and local buffering. The probability of system overflow of the simulated system is confronted with the one obtained by modeling.

Efficient gamma-ray signal decomposition analysis based on orthonormal transformation and fixed poles

Gamma-ray energy tracking is a new technique for the detection of gamma radiation. In such scheme, the individual interactions of the gamma rays with the germanium detectors are described by the energy, position and interaction time. Signal decomposition is the name of the procedure used to estimate the three-dimensional positions of the interactions based on pulse-shape analysis of the signals on the two-dimensional segments deposited on the faces of the detector. The present signal decomposition algorithm is computational intensive. For GRETINA, a detector being built based on this concept and that covers just a quarter of a sphere, 140 quad-processors are required to decompose 20,000 gamma interactions per second. In order to reduce the computational cost, we have conceptualized that the segments waveforms are generated by amplitude modulated discrete-time unit impulse. Projection of these waveforms into a more suitable basis reduces the computation costs while optimizing the same cost function. In this article we describe the framework for such projection, and we provide an example. For the present example, the computational cost was reduced by a factor of 5 times.

The luminosity monitoring system for the LHC: Modeling and test results

Simulation results of the Beam Rate of Neutrals (BRAN) luminosity detector for the CERN Large Hadron Collider are presented. The detectors are intended to measure the bunch-by-bunch relative luminosity at the ATLAS and CMS experiments. Building up from experimental results from test runs at the SPS, RHIC and ALS we extend the simulated setup to the TAN neutral absorbers located at 140 m at both sides the IP1 and IP5 interaction points. The expected signal amplitudes are calculated for pp-collisions energies between 450 GeV and 7 TeV using the Monte Carlo package FLUKA and its graphical user interface FLAIR.