Hole misalignment and gain performance of Gaseous Electron Multipliers

It is well known and has been shown that the gain performance of Gaseous Electron Multipliers (GEM) depends on the size of the holes. With an optical scanner it is possible to measure the dimensions of the holes, and to predict the performance of GEMs. However, the gain prediction of GEMs that are manufactured with a double mask etching technique is not straightforward. With the hole size information alone, it is not possible to make precise prediction of the gain. We show that the alignment of the photo-masks between the two sides of the GEM foils plays a crucial role. A misalignment of a few microns can lower the gain substantially. The study is performed by using the Helsinki high definition optical scanner for quality control of GEM foils, and this will show its true potential.Peer reviewe

Twin GEM-TPC prototype (HGB4) beam test at GSI – a tracking detector for the Super-FRS

The GEM-TPC detector will be part of the standard Super-FRS detection system, as tracker detectors at several focal diagnostic stations along the separator and its three branches.Non peer reviewe

Multispectral photon-counting for medical imaging and beam characterization - A project review

Central focus of the MPMIB project – funded via the Academy of Finland’s RADDESS 2018–2021 programme – has been research towards a next-generation radiation detection system operating in a photon-counting (PC) multispectral mode: The extraction of energy spectrum per detector pixel data will lead to better efficacy in medical imaging with ionizing radiation. Therefore, it can be an important asset for diagnostic imaging and radiotherapy, enabling better diagnostic outcome with lower radiation dose as well as more versatile characterization of the radiation beam, leading for example to more accurate patient dosimetry. We present our approach of fabricating direct-conversion detectors based on cadmium telluride (CdTe) semiconductor material hybridized with PC mode capable application-specific integrated circuits (ASICs), and will give a review on our achievements, challenges and lessons learned. The CdTe crystals were processed at Micronova, Finland’s national research infrastructure for micro- and nanotechnology, employing techniques such as surface passivation via atomic layer deposition, and flip chip bonding of processed sensors to ASIC. Although CdTe has excellent photon radiation absorption properties, it is a brittle material that can include large concentrations of defects. We will therefore also emphasize our quality assessment of CdTe crystals and processed detectors, and present experimental data obtained with prototype detectors in X-ray and Co-60 beams at a standards laboratoryPeer reviewe

Twin GEM-TPC prototype (HGB4) beam test at GSI and Jyväskylä : a development for the Super-FRS at FAIR

The FAIR facility is an international accelerator centre for research with ion and antiproton beams. It is being built at Darmstadt, Germany as an extension to the current GSI research institute. One major part of the facility will be the Super-FRS[2] separator, which will be include in phase one of the project construction. The NUSTAR experiments will benefit from the Super-FRS, which will deliver an unprecedented range of radioactive ion beams (RIB). These experiments will use beams of different energies and characteristics in three different branches; the high-energy which utilizes the RIB at relativistic energies 300-1500 MeV/u as created in the production process, the low-energy branch aims to use beams in the range of 0-150 MeV/u whereas the ring branch will cool and store beams in the NESR ring. The main tasks for the Super-FRS beam diagnostics chambers will be for the set up and adjustment of the separator as well as to provide tracking and event-by-event particle identification. The Helsinki Institute of Physics, and the Detector Laboratory and Experimental Electronics at GSI are in a joint R&D of a GEM-TPC detector which could satisfy the requirements of such tracking detectors, in terms of tracking efficiency, space resolution, count rate capability and momenta resolution. The current prototype, which is the generation four of this type, is two GEM-TPCs in twin configuration inside the same vessel. This means that one of the GEM-TPC is flipped on the middle plane w.r.t. the other one. This chamber was tested at Jyväskylä accelerator with protons projectiles and at GSI with Uranium, fragments and Carbon beams during this year 2016.Peer reviewe

Scintillation Tiles Production for the nT2 Telescope Upgrade of the TOTEM Experiment

The measurement of the total proton-proton cross-section using the luminosity independent method and the ρ parameter at the maximal collision energy of 13.6 TeV or more in Run 3 at CERNs Large Hadron Collider (LHC) requires an upgrade of the existing TOTEM T2 telescopes, which is called the new T2 (nT2). The specifications for nT2 is to provide inelastic event counting with maximal efficiency for data taking in special runs. The nT2 telescope consists of four quarters with each of them having 4 planes of plastic scintillators distributed in circular geometrical shape around the beam pipe on both sides of the CMS experiment and, at a distance of 15 m from the interaction point. The development of the concept was done in cooperation with CERN with the mass-production carried out at HIP. The results of its characterization at the PS and SPS at with muons/pions will be shown.Peer reviewe

Pixelated silicon detector for radiation beam profile measurements

A pixelated silicon detector, developed originally for particle physics experiments, was used for a beam profile measurement of a cobalt-60 (Co-60) irradiator in a water phantom. The beam profile was compared to a profile measured with a pinpoint ionization chamber. The differences in the pixel detector and pinpoint chamber relative profiles were within approximately 2% of profile maximum, and after calculating correction factors with Monte Carlo simulations for the pixel detector, the maximum difference was decreased to approximately 1% of profile maximum. The detector's capability to measure pulse-height was used to record an electron pulse-height spectrum in water in the Co-60 beam, and the results agreed well with simulations.Peer reviewe

In-beam test results of the Super-FRS GEM-TPC detector prototype with relativistic uranium ion beam

As an essential part of the Super-FRS particle identification, the GEM-TPC detector in a twin field-cage configuration will provide position information at up to 1 MHz counting rate with a spatial resolution 95%. This detector is designed to provide particle-beam tracking information of projectiles ranging from protons to uranium. The performance of the GEM-TPC detector in a single field-cage configuration and newly integrated AWAGS readout electronics with a differential output was studied at the FRS for the response to the uranium beam at 850 MeV/u with intensity up to 1000 ions/spill. The result shows that a clusterization algorithm developed for this analysis works properly. The spatial resolution of 0.74–0.81 mm, a detection efficiency > 99%, and a tracking efficiency > 96 % were found. This work describes the methodology used to achieve such results in detail.Peer reviewe

New insights into the genetic etiology of Alzheimer’s disease and related dementias

Characterization of the genetic landscape of Alzheimer’s disease (AD) and related dementias (ADD) provides a unique opportunity for a better understanding of the associated pathophysiological processes. We performed a two-stage genome-wide association study totaling 111,326 clinically diagnosed/‘proxy’ AD cases and 677,663 controls. We found 75 risk loci, of which 42 were new at the time of analysis. Pathway enrichment analyses confirmed the involvement of amyloid/tau pathways and highlighted microglia implication. Gene prioritization in the new loci identified 31 genes that were suggestive of new genetically associated processes, including the tumor necrosis factor alpha pathway through the linear ubiquitin chain assembly complex. We also built a new genetic risk score associated with the risk of future AD/dementia or progression from mild cognitive impairment to AD/dementia. The improvement in prediction led to a 1.6- to 1.9-fold increase in AD risk from the lowest to the highest decile, in addition to effects of age and the APOE ε4 allele

New insights into the genetic etiology of Alzheimer’s disease and related dementias

Characterization of the genetic landscape of Alzheimer’s disease (AD) and related dementias (ADD) provides a unique opportunity for a better understanding of the associated pathophysiological processes. We performed a two-stage genome-wide association study totaling 111,326 clinically diagnosed/‘proxy’ AD cases and 677,663 controls. We found 75 risk loci, of which 42 were new at the time of analysis. Pathway enrichment analyses confirmed the involvement of amyloid/tau pathways and highlighted microglia implication. Gene prioritization in the new loci identified 31 genes that were suggestive of new genetically associated processes, including the tumor necrosis factor alpha pathway through the linear ubiquitin chain assembly complex. We also built a new genetic risk score associated with the risk of future AD/dementia or progression from mild cognitive impairment to AD/dementia. The improvement in prediction led to a 1.6- to 1.9-fold increase in AD risk from the lowest to the highest decile, in addition to effects of age and the APOE ε4 allele