A large-scale Scintillating Fibre Tracker has been developed and constructed for the current LHCb Upgrade 1. The high radiation by fast neutrons reduces the light yield of the detector in the course ...of LHC Run 3, and is challenging the tracker’s hit detection efficiency. To mitigate radiation-induced ageing effects, the central fibre mats and photodetectors will be replaced during the next long shutdown (2026–2028). For this purpose, microlens-enhanced silicon photomultipliers with an improved photon detection efficiency are being developed. The first prototypes have been produced based on the outcome of dedicated simulation studies, and the results of the first light yield measurements are presented.
Purpose
For determining small‐field profile and output factor during stereotactic radiotherapy quality assurance (QA) procedures, we propose a novel system based on the scintillating fiber (SciFi) ...detector with output image acquisition and processing to allow real‐time monitoring of profile and output factor.
Materials and methods
The employed detector is a SciFi detector made of tissue‐equivalent scintillating plastic fibers arranged in 6‐layer fiber ribbons with a fiber pitch of 275 μm in each layer. The scintillating signal at the detector output is acquired by a sCMOS (scientific complementary metal–oxide–semiconductor) camera and represents the projected field profile along the fibers axis. An iterative reconstruction method of the field from its projected profile based on a priori knowledge of some features of the radiation field defined by the stereotactic cones is suggested. The detector with implemented data processing has been tested in clinical conditions, for determining beam profiles and output factors, using cone collimators of different sizes from 4 to 15 mm diameter. The detector under test was placed at 1.4 cm depth and 98.6 cm source to surface distance (SSD) in a water‐equivalent phantom and irradiated by a 6 MV photon beam.
Results
The reconstructed field profiles obtained from the detector are coherent with data from EBT3 radiochromic films, with differences within ±0.32 mm for both the FWHM and the penumbra region. For real‐time determination of the field output factor, the measured data are also in good agreement with data independently determined by the French Institute for Radiological Protection and Nuclear Safety (IRSN) based on radiochromic films and thermoluminescent 1 × 1 mm2 micro‐cubes dosimeters (TLD). The differences are within ±1.6% for all the tested cone sizes.
Conclusions
We propose and have tested a SciFi plastic scintillating detector with an optimized signal processing method to characterize small fields defined by cone collimators. It allows the determination of key field parameters such as full width at half maximum (FWHM) and field output factors. The results are consistent with those independently measured using TLD and radiochromic films. As the SciFi detector does not require a correction factor, it is in line with the International Atomic Energy Agency (IAEA) and the American Association of Physicists in Medicine (AAPM) TRS‐483 recommendations, and can be suitable for online QA of small radiation fields used in photon beam radiotherapy, and is compatible with MRI‐LINAC.
The CERN Super Proton Synchrotron (SPS) delivers a wide spectrum of particle beams (hadrons, leptons and heavy ions) that can vary greatly in momentum and intensity. The profile and position of these ...beams are measured using particle detectors. However, the current systems show several problems that limit the quality of such monitoring. We have researched a new monitor made of scintillating fibres read-out with Silicon Photomultipliers (SiPM), which has the potential to perform better in terms of material budget, range of intensities measured and available detector size. In addition, it also has particle counting capabilities, extending its use to spectrometry or Time-Of-Flight measurements. Its radiation hardness is good to guarantee years of functioning. We have successfully tested a first prototype of this detector with different particle beams at CERN, giving accurate profile measurements over a wide range of energies and intensities. It only showed problems during operation with lead ion beams, believed to come from crosstalk between the fibres. Investigations are ongoing on alternative photodetectors, the electronics readout and solutions to the fibre crosstalk.
The LHCb DAQ interface board TELL1 Haefeli, G.; Bay, A.; Gong, A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2006, Volume:
560, Issue:
2
Journal Article
Peer reviewed
We have developed an electronic board (TELL1) to interface the DAQ system of the LHCb experiment at CERN. 289 TELL1 boards are needed to read out the different subdetectors. Each board can handle ...either 64 analog or 24 digital optical links. The TELL1 mother board provides common mode correction, zero suppression, data formatting, and a large network interface buffer. To satisfy the different requirements we have adopted a flexible FPGA design and made use of mezzanine cards. Mezzanines are used for data input from digital optical and analog copper links as well as for the Gigabit Ethernet interface to DAQ. The LHCb timing and trigger control signals are transported by a dedicated optical link, while the board slow-control is provided by an embedded PC running a Linux kernel.
We propose a novel field-monitoring system for Stereotactic Radiation Therapy (SRT) based on scintillating waveguides ribbons with output image acquisition. Waveguides ribbons are realized in two ...ways: micro-structuring a scintillating sheet and using the SciFi detector technology. Both technologies provide sub-millimeter waveguide pitches suitable for SRT-field monitoring. The proposed system implemented in three different prototypes has been tested in clinical conditions. The obtained results from both ribbon technologies confirm suitable sensitivity and spatial resolution for SRT QA procedures.
The beam-gas vertex (BGV) detector is an innovative instrument measuring noninvasively the transverse beam size in the Large Hadron Collider (LHC) using reconstructed tracks from beam-gas ...interactions. The BGV detector was installed in 2016 as part of the R&D for the High-Luminosity LHC project. It allows beam size measurements throughout the LHC acceleration cycle with high-intensity physics beams. A precision better than 2% with an integration time of less than 30 s is obtained on the average beam size measured, while the transverse size of individual proton bunches is measured with a resolution of 5% within 5 min. Particles emerging from beam-gas interactions in a specially developed gas volume along the beam direction are recorded by two tracking stations made of scintillating fibers. A scintillator trigger system selects, on-line, events with tracks originating from the interaction region. All the detector elements are located outside the beam vacuum pipe to simplify the design and minimize interference with the accelerated particle beam. The beam size measurement results presented here are based on the correlation between tracks originating from the same beam-gas interaction vertex.
In the framework of the EMPIR project MetroBeta, the development and optimization of a double focalizing magnetic spectrometer have been realized in order to measure the beta spectra shape. The ...acquisition is designed to perform,after focalization by the magnetic field, an energy selection using a window on the deposited energy in the Si detector. The energy calibration is performed using conversion electrons from 109Cd, 137Cs, 133Ba and 207Bi and the measured energy resolution is 1.3% at 1 MeV. The efficiency is measured experimentally using a 204Tl source and is used to reconstruct the spectrum shape for beta emitters with end-point energy up to 750 keV. Two beta emitters with allowed transitions, 134Cs and 60Co, are used to validate the measurement and the reconstruction method. Finally the measurement of the beta shape of 36Cl, a non-unique 2nd forbidden transition is presented.
•Magnetic spectrometer development for beta shape measurement from 60 keV to 700 keV•New acquisition system recording the energy deposited in a 1 mm thick Si detector.•Data analysis performed offline using an energy window on the deposited energy.•Validation is performed using known spectra of 60Co and 134Cs.•Measurement of the spectrum shape of 36Cl.
PDF
