123023484
Development of a fast proton range radiography system for quality assurance in hadrontherapy
Abstract We describe the development of a Proton Range Radiography system with an imaging area of 30×30 cm 2 for two dimensional mapping of the integrated density in a target. Proton transmission radiographic images are produced by measuring, with a pair of position-sensitive detectors (GEM chambers), the direction of the protons transmitted through the patient and, with a stack of scintillators, the residual range of the protons leaving the patient. To match the data rate requirements of an in-beam diagnostic, a novel data acquisition system for the tracking detectors has been designed to operate at 1 MHz data flow. Laboratory tests exposing the GEM detector with high flux X-rays confirm the fast response of the new data acquisition system. Images of several phantoms have been recorded to demonstrate the GEM position accuracy.
110349136
First results of FGLD gas detector with multi-channel self-triggering readout electronics
Following the successful demonstration of a proof-of-concept FGLD detector, work has been done to find a multi-channel readout electronics capable of obtaining the position information from its 3-axis geometry and suitable for medical imaging applications. The IDEAS GP3 and GP5 chips were selected for testing because they are sensitive to the range of input charge collected on the FGLD and because they are self-triggering. Preliminary tests in which both the GP3 and GP5 were connected to the ground layer of the FGLD has yielded promising results. Signals can be seen in the analysis software and some initial results of the charge sharing between strips is presented. Furthermore, both chips were subjected to forced discharging. Only a few input channels localized about the discharge were destroyed in the GP3 whereas the GP5 continued to function normally after repeated discharges.
108950803
Results of a prototype imaging system using the FGLD technology and self-triggering discharge-protected readout electronics
Previous work on the FGLD (Field Gradient Lattice Detector) involved reading out 50 strips from the detector using the GP5 chip: a 128-channel charge-sensitive preamplifier with integrated individually programmable trigger. The work showed that the GP5 was suitable as a front-end electronics, but demonstrated the need to protect the inputs from discharges. To that end, the 128-channel diode protection chip developed for the TOTEM experiment has been successfully adapted to the GP5 and shown to make the GP5 resilient to destruction upon discharge. Armed with this robust front-end electronics and the FGLD technology, the group is developing a prototype imaging system capable of producing images relevant for medical and industrial applications. A discussion of the system's parameters and performance will be presented along with some images made with a collimated source.
119630665
Fast readout of GEM detectors for medical imaging
Abstract We describe the design and implementation of a fast data acquisition (DAQ) system for Gas Electron Multiplier (GEM) trackers applied to imaging and dosimetry in hadrontherapy. Within the AQUA project of the TERA foundation a prototype of Proton Range Radiography of 30×30 cm 2 active area has been designed and built to provide in-beam integrated density images of the patient before treatment. It makes use of a pair of GEMs to record position and direction of protons emerging from the target. A fast data acquisition rate close to 1 MHz will allow obtaining a good resolution in-beam proton radiography in a few seconds. A dedicated fast front-end circuit for GEM detectors (GEMROC by AGH-Crakow University) is read by the FPGA based DAQ card (GR_DAQ), developed by the AQUA group. The same system is under evaluation (within the ENVISION European project) to realize the in-vivo dosimetry, based on detecting secondary light particles during the treatment of the patient.
120740000
FGLD: a novel and compact micro-pattern gas detector
Abstract A new gas detector which combines in the same structure the gas amplification mechanism and the position sensitive readout, named the field gradient lattice detector (FGLD), is being developed at CERN. The detector, reminiscent in geometry of a multi-wire proportional chamber but with a different field configuration can be fabricated as two or more layers of micro-patterned parallel tracks on a variety of substrate materials. Two preliminary proof-of-concept designs without position sensitivity have been fabricated as copper tracks of 50 μ m width and 150 μ m pitch on polyimide in a 3D geometry and on epoxy in a 2D geometry. They have been shown to detect the 5.9 keV X-rays of an 55 Fe source with a stable gain ranging from 500 to 5000 in a 3 mm drift chamber containing an argon carbon-dioxide gas mixture. The elegance and compactness of the FGLD design make it a very attractive gas detector solution both economically and mechanically. Most interestingly, the 3D FGLD design on flexible polyimide should greatly simplify the mechanical challenges of gas chamber assembly in planar and cylindrical detector designs.
96911852
THE CRYSTAL BALL AT MAMI
121661802
The Crystal Ball programme at MAMI
This contribution will outline the physics programme exploiting the intense energy tagged polarised real photon beam at MAMI-C. The coupling of an intense photon beam and close to complete detector acceptance offers unique opportunities for preci- sion measurements to challenge our understanding of the structure of the nucleon and the nucleus as well as the underlying theory of Quantum Chromo Dynamics (QCD). The experimental facility and the physics programme will be outlined and selected recent pre- liminary analyses will be presented.
119383062
Three-nucleon mechanisms in photoreactions
Abstract The 12 C( γ ,ppn) reaction has been measured for E γ =150–800 MeV in the first study of this reaction in a target heavier than 3 He. The experimental data are compared to a microscopic many body calculation. The model, which predicts that the largest contribution to the reaction arises from final state interactions following an initial pion production process, overestimates the measured cross sections and there are strong indications that the overestimate arises in this two-step process. The selection of suitable kinematic conditions strongly suppresses this two-step contribution leaving cross sections in which up to half the yield is predicted to arise from the absorption of the photon on three interacting nucleons and which agree with the model. The results indicate ( γ ,3N) measurements on nuclei may be a valuable tool for obtaining information on the nuclear three-body interaction.
122031325
PiP — a large solid angle scintillation telescope for detecting protons and pions
Abstract A ∼ 1 sr solid angle scintillation detector hodoscope for protons of up to ∼ 280 MeV and positive pions of up to ∼ 180 MeV energy has been developed for use in (γ,pN), ( γ ,p π ± and ( γ , π + N) experiments with tagged photons. This paper reports the detailed design of the hodoscope and its performance for detecting protons and positive pions.
120639175
Study of N* properties at CLAS
The excitation spectrum of the nucleon provides a stringent constraint on the dynamics and interactions of its internal constituents and therefore probes the mechanism of confinement in the light quark sector. Our detailed knowlege of this excitation spectrum is poor, with many predicted states not yet observed in experiment and many "established" states having poorly known properties. To address these shortcomings a worldwide effort is currently underway exploiting the latest generation of electron and photon beams in detailed studies of meson photoproduction from nucleon targets. A major contribution to this effort will come from the experimental programme at Jefferson Lab exploiting the frozen spin target (FROST) with the CLAS spectrometer. The status of this project will be presented along with preliminary results and analyses.