Session DJ: Instrumentation - Software and Simulation

Data Acquisition Software for Experiments at the MAMI-C Tagged Photon Facility

Tagged-photon experiments at Mainz use the electron beam of the MAMI (Mainzer MIcrotron) accelerator, in combination with the Glasgow Tagged Photon Spectrometer. The AcquDAQ DAQ system is implemented in the C$++$ language and makes use of CERN ROOT software libraries and tools. Electronic hardware is characterized in C$++$ classes, based on a general purpose class TDAQmodule and implementation in an object-oriented framework makes the system very flexible. The DAQ system provides slow control and event-by-event readout of the Photon Tagger, the Crystal Ball 4-pi electromagnetic calorimeter, central MWPC tracker and plastic-scintillator, particle-ID systems and the TAPS forward-angle calorimeter. A variety of front-end controllers running Linux are supported, reading data from VMEbus, FASTBUS and CAMAC systems. More specialist hardware, based on optical communication systems and developed for the COMPASS experiment at CERN, is also supported. AcquDAQ also provides an interface to configure and control the Mainz programmable trigger system, which uses FPGA-based hardware developed at GSI. Currently the DAQ system runs at data rates of up to 3MB/s and, with upgrades to both hardware and software later this year, we anticipate a doubling of that rate.   

Optimization of the NSCL Digital Data Acquisition System For Use With Fast Scintillator Detectors

The Digital Data Acquisition System (DDAS) at the National Superconducting Cyclotron Laboratory is composed of several XIA Pixie-16 modules utilizing 12-bit digitizers sampling at 100 Mega-Samples-Per-Second. DDAS has been applied to fast organic and inorganic scintillator detectors intended for level lifetime and neutron time-of-flight studies, for which the time resolution is critical. Simultaneous high-resolution time and energy determination using online digital CFD and trapezoidal filtering algorithms is non-intuitive due to the short characteristic rise and decay times of the signals with respect to the sampling time of the digitizers. A new technique has been developed to identify the optimum filter parameters to maximize the time and energy resolution of each detector signal in an offline analysis. The parameters were subsequently verified online and have resulted in a 30{\%} improvement in the measured time resolution between two LaBr3 detectors. Additional results and applications of the technique will be presented.   

Feasibility Study of NI's FlexRIO Platform for High-Throughput Data Acquisition

The Nab neutron decay correlation experiment requires high energy and time resolution, and a multipixel low threshold trigger to efficiently detect 30 keV protons. Digital waveforms must be read out for offline pulse-shape analysis from all neighboring channels of hits in the two 128-pixel ion implanted silicon detectors. National Instrument's FlexRIO system has a unique data acquisition architecture based on a single 500 ms ring buffer which continuously records data. Custom discriminators can be programmed by the user on the FPGA with LabVIEW graphical programming language, and multichannel trigger logic can be implemented on the CPU using the bidirectional, high bandwidth, low latency PCI bus. We developed a low-threshold trigger using a trapezoid energy filter to test the feasibility of this system. We will present our experience programming the trigger and the resulting performance, including detection efficiency and background noise rejection.   

Jefferson Laboratory Hall A SuperBigBite Spectrometer Data Acquisition System

The SuperBigBite detector is a large acceptance spectrometer which is being built for Hall A at Jefferson Laboratory and planned for completion in 2017. Several experiments are approved for this detector ranging from form factors to nucleon structure. The detector consists mainly of a large dipole magnet and several plane of Gas Electron Multiplier trackers associated with calorimeters. In order to reduce the cost of the project the electronics used will be a mix of older Fastbus and newly developed electronics. I will present the layout of the system and how we plan to handle the high background rates seen by the different detectors for the different experiments.   

Simulation of Properties of COMPASS Drift-Chamber Prototypes

For a future detector upgrade at COMPASS, two drift chamber prototypes A and B have been developed and built at the University of Illinois at Urbana-Champaign. The prototypes constitute small versions of the actual size drift chamber and host either one (prototype A) or two (prototype B) layers of each 8 (A) or 16 (B) sense wires, alternating with field wires and with a potential difference of about 2kV between sense and field wires.The wires are embedded into a gas volume of a mix of 5\% CF4, 50\% C2H6 and 45\% Argonne. With the CERN GARFIELD computer program, the key properties of the drift chambers have been simulated: drift velocity, arrival time distributions and induced signal on the sense wires, and position resolutions. The results of the simulations are compared to measurements employing cosmic muons and to the DESY 5-GeV-electron test beam measurement of 2013.   

Progress in Offline Software for the GlueX Experiment at Jefferson Lab

The GlueX Experiment will begin taking data next year at CEBAF at Jefferson Lab. CEBAF is being upgraded to deliver 12 GeV electrons and GlueX will receive a secondary, tagged photon beam with linear polarization in a new experimental hall, Hall D. Over the past few years the collaboration has worked preparing offline software to do event simulation, event reconstruction, and data analysis in preparation for the beginning of operations. Progress in these areas will be presented along with a description of data challenges completed to test scaling of computing infrastructure.   

Geant4 Simulation of A Multi-layered target for the Study of Neutron-Unbound Nuclei

The MoNA/LISA setup at the National Superconducting Cyclotron Laboratory at Michigan State University has provided an avenue to study the nuclear structure of unbound states/nuclei at and beyond the neutron dripline for the past decade using secondary beams from the Coupled Cyclotron Facility. A new multi-layered Si/Be active target is being designed to specifically study neutron-unbound nuclei. In these experiments the decay energy is reconstructed from fragment-neutron coincidence measurements that are typically low in count rate. The multi-layered target will allow the use of thicker targets to increase the reaction rates, thus enabling to study currently out of reach nuclei such as 21C, 23C and 24N. The Geant4 Monte Carlo toolkit is currently used to model these physics processes within the multi-layered target and expected invariant mass distributions. A description of the experimental setup and simulation work will be discussed.   

Monte Carlo Simulation of Detector Response in the Nab Experiment

The Nab experiment aims at a precise measurement of $a$, the electron neutrino correlation parameter, and $b$, the Fierz interference term, in neutron decay. The measurement is to be performed at the Spallation Neutron Source (SNS) in Oak Ridge, TN, using an asymmetric magneto-electrostatic spectrometer. The spectrometer uses two hexagonally segmented large silicon detectors, one located at each end of the spectrometer. Two systematics of the spectrometer are of particular relevance. To correlate proton and electron hits, it is necessary to study the pixel correlation of the two decay products. Furthermore it is necessary to analyze the timing offset due to the greater stopping depth of the electrons, especially those of higher energies. Different timing offsets caused by differences in propagation time in the detector affect the reconstructed proton momentum. Both have been studied using Monte Carlo Simulation of the spectrometer in GEANT4; results for both effects will be presented.   

Simulation of a Novel Active Target for Neutron-Unbound State Measurements

Measurement of nuclei at extreme ratios of protons to neutrons is challenging due to the low production rate. New facilities will increase the production of neutron-rich isotopes, but still not reach the neutron dripline for heavier nuclei. We simulated a carbon-based active target system that could be constructed to both increase statistics while preserving the experimental resolution. This simulation is an adaptation of the in-house MoNA Collaboration C$++$ based simulation tool to extract the decay energy of neutron-unbound states. A number of experiments of this type have been carried out at the National Superconducting Cyclotron Laboratory (NSCL). In most experiments, we produce neutron-unbound nuclei by bombarding a Beryllium target with a radioactive beam. The nucleus of interest immediately decays into a charged particle and one or more neutrons. In this simulation, we have constructed a carbon-based active target that provides a measurement of energy loss, which is used to calculate the nuclear interaction point within the target. This additional information is used to improve the resolution or preserve the resolution of a thinner target while increasing statistics. This presentation will cover some aspects of the simulation process as well as show a resolution improvement of up to about 4 with a $\sim$700 mg/cm$^{2}$ active target compared to a Be-target. The simulation utilized experimental settings from published work.