66 research outputs found
Separation of atomic and molecular ions by ion mobility with an RF carpet
Gas-filled stopping cells are used at accelerator laboratories for the
thermalization of high-energy radioactive ion beams. Common challenges of many
stopping cells are a high molecular background of extracted ions and
limitations of extraction efficiency due to space-charge effects. At the FRS
Ion Catcher at GSI, a new technique for removal of ionized molecules prior to
their extraction out of the stopping cell has been developed. This technique
utilizes the RF carpet for the separation of atomic ions from molecular
contaminant ions through their difference in ion mobility. Results from the
successful implementation and test during an experiment with a 600~MeV/u
Xe primary beam are presented. Suppression of molecular contaminants by
three orders of magnitude has been demonstrated. Essentially background-free
measurement conditions with less than of background events within a
mass-to-charge range of 25 u/e have been achieved. The technique can also be
used to reduce the space-charge effects at the extraction nozzle and in the
downstream beamline, thus ensuring high efficiency of ion transport and
highly-accurate measurements under space-charge-free conditions.Comment: 8 pages, 4 figure
Performance of the MALTA Telescope
MALTA is part of the Depleted Monolithic Active Pixel sensors designed in
Tower 180nm CMOS imaging technology. A custom telescope with six MALTA planes
has been developed for test beam campaigns at SPS, CERN, with the ability to
host several devices under test. The telescope system has a dedicated custom
readout, online monitoring integrated into DAQ with realtime hit map, time
distribution and event hit multiplicity. It hosts a dedicated fully
configurable trigger system enabling to trigger on coincidence between
telescope planes and timing reference from a scintillator. The excellent time
resolution performance allows for fast track reconstruction, due to the
possibility to retain a low hit multiplicity per event which reduces the
combinatorics. This paper reviews the architecture of the system and its
performance during the 2021 and 2022 test beam campaign at the SPS North Area
Recent results with radiation-tolerant TowerJazz 180 nm MALTA sensors
To achieve the physics goals of future colliders, it is necessary to develop novel, radiation-hard silicon sensors for their tracking detectors. We target the replacement of hybrid pixel detectors with Depleted Monolithic Active Pixel Sensors (DMAPS) that are radiation-hard, monolithic CMOS sensors. We have designed, manufactured and tested the MALTA series of sensors, which are DMAPS in the 180 nm TowerJazz CMOS imaging technology. MALTA have a pixel pitch well below current hybrid pixel detectors, high time resolution (<2 ns) and excellent charge collection efficiency across pixel geometries. These sensors have a total silicon thickness of between 50â300 m, implying reduced material budgets and multiple scattering rates for future detectors which utilize such technology. Furthermore, their monolithic design bypasses the costly stage of bump-bonding in hybrid sensors and can substantially reduce detector costs. This contribution presents the latest results from characterization studies of the MALTA2 sensors, including results demonstrating the radiation tolerance of these sensors
Performance of the MALTA telescope
MALTA is part of the Depleted Monolithic Active Pixel sensors designed in Tower 180 nm CMOS imaging technology. A custom telescope with six MALTA planes has been developed for test beam campaigns at SPS, CERN, with the ability to host several devices under test. The telescope system has a dedicated custom readout, online monitoring integrated into DAQ with realtime hit map, time distribution and event hit multiplicity. It hosts a dedicated fully configurable trigger system enabling to trigger on coincidence between telescope planes and timing reference from a scintillator. The excellent time resolution performance allows for fast track reconstruction, due to the possibility to retain a low hit multiplicity per event which reduces the combinatorics. This paper reviews the architecture of the system and its performance during the 2021 and 2022 test beam campaign at the SPS North Area
Radiation hardness of MALTA2 monolithic CMOS imaging sensors on Czochralski substrates
MALTA2 is the latest full-scale prototype of the MALTA family of Depleted Monolithic Active Pixel Sensors (DMAPS) produced in Tower Semiconductor 180 nm CMOS sensor imaging technology. In order to comply with the requirements of high energy physics (HEP) experiments, various process modifications and front-end changes have been implemented to achieve low power consumption, reduce random telegraph signal (RTS) noise, and optimise the charge collection geometry. Compared to its predecessors, MALTA2 targets the use of a high-resistivity, thick Czochralski (Cz) substrates in order to demonstrate radiation hardness in terms of detection efficiency and timing resolution up to 3 Ă 1015 1 MeV neq/cm2 with backside metallisation to achieve good propagation of the bias voltage. This manuscript shows the results that were obtained with non-irradiated and irradiated MALTA2 samples on Cz substrates from the CERN SPS test beam campaign from 2021 to 2023 using the MALTA telescope
The science case of the FRS Ion Catcher for FAIR Phase-0
The FRS Ion Catcher at GSI enables precision experiments with thermalized projectile and fission fragments. At the same time it serves as a test facility for the Low-Energy Branch of the Super-FRS at FAIR. The FRS Ion Catcher has been commissioned and its performance has been characterized in five experiments with 238U and 124Xe projectile and fission fragments produced at energies in the range from 300 to 1000 MeV/u. High and almost element-independent efficiencies for the thermalization of short-lived nuclides produced at relativistic energies have been obtained. High-accuracy mass measurements of more than 30 projectile and fission fragments have been performed with a multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS) at mass resolving powers of up to 410,000, with production cross sections down to the microbarn-level, and at rates down to a few ions per hour. The versatility of the MR-TOF-MS for isomer research has been demonstrated by the measurement of various isomers, determination of excitation energies and the production of a pure isomeric beam. Recently, several instrumental upgrades have been implemented at the FRS Ion Catcher. New experiments will be carried out during FAIR Phase-0 at GSI, including direct mass measurements of neutron-deficient nuclides below 100Sn and neutron-rich nuclides below 208Pb, measurement of ÎČ-delayed neutron emission probabilities and reaction studies with multi-nucleon transfer.Peer reviewe
Freeâbreathing selfâgated 4D lung MRI using waveâCAIPI
Purpose
The aim of this study was to compare the waveâCAIPI (controlled aliasing in parallel imaging) trajectory to the Cartesian sampling for accelerated freeâbreathing 4D lung MRI.
Methods
The waveâCAIPI kâspace trajectory was implemented in a respiratory selfâgated 3D spoiled gradient echo pulse sequence. Trajectory correction applying the gradient system transfer function was used, and images were reconstructed using an iterative conjugate gradient SENSE (CG SENSE) algorithm. Five healthy volunteers and one patient with squamous cell carcinoma in the lung were examined on a clinical 3T scanner, using both sampling schemes. For quantitative comparison of waveâCAIPI and standard Cartesian imaging, the normalized mutual information and the RMS error between retrospectively accelerated acquisitions and their respective references were calculated. The SNR ratios were investigated in a phantom study.
Results
The obtained normalized mutual information values indicate a lower information loss due to acceleration for the waveâCAIPI approach. Average normalized mutual information values of the waveâCAIPI acquisitions were 10% higher, compared with Cartesian sampling. Furthermore, the RMS error of the waveâCAIPI technique was lower by 19% and the SNR was higher by 14%. Especially for short acquisition times (down to 1 minute), the undersampled Cartesian images showed an increased artifact level, compared with waveâCAIPI.
Conclusion
The application of the waveâCAIPI technique to 4D lung MRI reduces undersampling artifacts, in comparison to a Cartesian acquisition of the same scan time. The benefit of waveâCAIPI sampling can therefore be traded for shorter examinations, or enhancing image quality of undersampled 4D lung acquisitions, keeping the scan time constant
Freeâbreathing selfâgated 4D lung MRI using waveâCAIPI
Purpose
The aim of this study was to compare the waveâCAIPI (controlled aliasing in parallel imaging) trajectory to the Cartesian sampling for accelerated freeâbreathing 4D lung MRI.
Methods
The waveâCAIPI kâspace trajectory was implemented in a respiratory selfâgated 3D spoiled gradient echo pulse sequence. Trajectory correction applying the gradient system transfer function was used, and images were reconstructed using an iterative conjugate gradient SENSE (CG SENSE) algorithm. Five healthy volunteers and one patient with squamous cell carcinoma in the lung were examined on a clinical 3T scanner, using both sampling schemes. For quantitative comparison of waveâCAIPI and standard Cartesian imaging, the normalized mutual information and the RMS error between retrospectively accelerated acquisitions and their respective references were calculated. The SNR ratios were investigated in a phantom study.
Results
The obtained normalized mutual information values indicate a lower information loss due to acceleration for the waveâCAIPI approach. Average normalized mutual information values of the waveâCAIPI acquisitions were 10% higher, compared with Cartesian sampling. Furthermore, the RMS error of the waveâCAIPI technique was lower by 19% and the SNR was higher by 14%. Especially for short acquisition times (down to 1 minute), the undersampled Cartesian images showed an increased artifact level, compared with waveâCAIPI.
Conclusion
The application of the waveâCAIPI technique to 4D lung MRI reduces undersampling artifacts, in comparison to a Cartesian acquisition of the same scan time. The benefit of waveâCAIPI sampling can therefore be traded for shorter examinations, or enhancing image quality of undersampled 4D lung acquisitions, keeping the scan time constant
Mean range bunching of exotic nuclei produced by in-flight fragmentation and fission â Stopped-beam experiments with increased efficiency
The novel technique of mean range bunching has been developed and applied at the projectile fragment separator FRS at GSI in four experiments of the FAIR phase-0 experimental program. Using a variable degrader system at the final focal plane of the FRS, the ranges of the different nuclides can be aligned, allowing to efficiently implant a large number of different nuclides simultaneously in a gas-filled stopping cell or an implantation detector. Stopping and studying a cocktail beam overcomes the present limitations of stopped-beam experiments. The conceptual idea of mean range bunching is described and illustrated using simulations. In a single setting of the FRS, 37 different nuclides were stopped in the cryogenic stopping cell and were measured in a single setting broadband mass measurement with the multiple-reflection time-of-flight mass spectrometer of the FRS Ion Catcher.</p
- âŠ