A low mass pixel detector upgrade for CMS

The CMS pixel detector has been designed for a peak luminosity of 10^34cm-2s-1 and a total dose corresponding to 2 years of LHC operation at a radius of 4 cm from the interaction region. Parts of the pixel detector will have to be replaced until 2015. The detector performance will be degraded for two reasons: radiation damage of the innermost layers and the planned increase of the LHC peak luminosity by a factor of 2-3. Based on the experience in planning, constructing and commissioning of the present pixel detector, we intend to upgrade the whole pixel detector in 2015. The main focus is on lowering the material budget and adding more tracking points. We will present the design of a new low mass pixel system consisting of 4 barrel layers and 3 end cap disks on each side. The design comprises of thin detector modules and a lightweight mechanical support structure using CO2 cooling. In addition, large efforts have been made to move material from the services out of the tracking region.Comment: 10 pages, 10 figures, Proceeding of RD09 - 9th International Conference on Large Scale Applications and Radiation Hardness of Semiconductor Detectors 30 September - 2 October 2009, Florence, Ital

Radiation hardness of CMS pixel barrel modules

Pixel detectors are used in the innermost part of the multi purpose experiments at LHC and are therefore exposed to the highest fluences of ionising radiation, which in this part of the detectors consists mainly of charged pions. The radiation hardness of all detector components has thoroughly been tested up to the fluences expected at the LHC. In case of an LHC upgrade, the fluence will be much higher and it is not yet clear how long the present pixel modules will stay operative in such a harsh environment. The aim of this study was to establish such a limit as a benchmark for other possible detector concepts considered for the upgrade. As the sensors and the readout chip are the parts most sensitive to radiation damage, samples consisting of a small pixel sensor bump-bonded to a CMS-readout chip (PSI46V2.1) have been irradiated with positive 200 MeV pions at PSI up to 6E14 Neq and with 21 GeV protons at CERN up to 5E15 Neq. After irradiation the response of the system to beta particles from a Sr-90 source was measured to characterise the charge collection efficiency of the sensor. Radiation induced changes in the readout chip were also measured. The results show that the present pixel modules can be expected to be still operational after a fluence of 2.8E15 Neq. Samples irradiated up to 5E15 Neq still see the beta particles. However, further tests are needed to confirm whether a stable operation with high particle detection efficiency is possible after such a high fluence.Comment: Contribution to the 11th European Symposium on Semiconductor Detectors June 7-11, 2009 Wildbad Kreuth, German

"Plasmodium falciparum var" Gene Expression Dynamics and its Relevance in Malaria Disease in Children from Papua New Guinea

Malaria is a tremendous global public health problem. While especially hitting the poorest countries in the world, malaria elicits each year 300 million febrile illnesses and up to 1 million deaths. Widespread drug resistances, climatic changes, but also disintegrated health services and armed conflicts have contributed to a global increase of malaria while a vaccine will not be at hand for many more years to come. Malaria is caused by the protozoan parasite Plasmodium and transmitted by the female Anopheles mosquito. Of 4 Plasmodium species infecting humans, Plasmodium falciparum is by far the most harmful parasite responsible for nearly all mortality. The increased virulency of P. falciparum can be ascribed to special immune evasion strategies inherent of this species. This mainly refers to a process called cytoadherence, the sequestration and adhesion of infected erythrocytes (IE) to endothelial cells of the microcapillary system. To evade spleen dependent killing, cytoadherence is a benefit for the parasite, but detrimental to the host by leading to poorly diffused tissues and hypoxia in the upstream segments and thus, contributing substantially to severe manifestations. Related to sequestration is a process called rosetting, the binding of IE to uninfected erythrocytes. This leads to erythrocyte clusters impeding local blood flow and accordingly, rosette formation was also associated with severe disease. On the surface of IE, the parasite derived protein family Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) is thought to be the key mediator for sequestration and rosetting. However, by exposing a parasite derived antigen on the surface of IE, the parasite gets vulnerable to immune attack. Therefore, P. falciparum evades the immune system by a process called antigenic variation, the switching of the expression between different members of PfEMP1. PfEMP1 is encoded by approximately 60 var genes per haploid genome. The highly diverse and large var genes are structured into several adhesive, semi-conserved domains. Most var genes can be subgrouped into var group A, B and C according to their diverse, but within one group highly conserved untranslated regions. Despite of the substantial contribution of PfEMP1 to malaria pathogenesis and parasite survival, few studies on var genes and PfEMP1 have been carried out in vivo. This is mainly due to their immense diversity interfering with most study designs. We conducted 2 studies on var gene expression in naturally infected children from Papua New Guinea. In a longitudinal study over a 4-month period in older, semi-immune children, we studied antigenic variation of var genes, namely the dynamics and distribution of var transcripts over time. Diversity and patterns of full-length var transcripts were evaluated by magnetic bead-anchored reverse-transcription polymerase chain reaction (RT-PCR), cloning and sequencing. We identified a highly dynamic picture of var expression with mostly new var transcripts at a 2-weeks interval but with some var transcripts recurring for up to 10 weeks. The number of detected var transcripts correlated with the number of infecting P. falciparum strains. On average, 1.7 different var transcripts were detected per child and infecting strain. The analysis of 286 different sequences of selected var gene domains confirmed the recombinogenic nature of var genes. In a malaria case-control study on children from Papua New Guinea, we quantitatively compared the distribution of var transcripts among var groups A, B and C in children with severe malaria, with mild malaria and in asymptomatic children. The sub-division of var genes into these var groups raises questions about the biological or clinical significance of these structural differences. Upon expression, different var groups might have different pathological implications on the host leading to distinct virulences and different clinical outcomes. By using real-time quantitative PCR, we found a major expression difference between parasites causing clinical attack and parasites leading to asymptomatic infections. A significant up-regulation of var group B transcripts was evident in children with clinical malaria (mild and severe) while var group C genes were mainly switched on in asymptomatic children. No change in the distribution of var transcripts was detected between mild and severe disease. Finally, we found a significant up-regulation of var group A genes in parasites conferring the formation of rosettes. Together, these studies on var gene expression are the first of its kind, conducted in naturally infected children in an endemic area. They are a step towards the comprehension of the dynamics and impacts of var gene expression in vivo. Together with previous studies, our data emphasize the substantial implications of PfEMP1 in malaria morbidity

CMS Barrel Pixel Detector Overview

The pixel detector is the innermost tracking device of the CMS experiment at the LHC. It is built from two independent sub devices, the pixel barrel and the end disks. The barrel consists of three concentric layers around the beam pipe with mean radii of 4.4, 7.3 and 10.2 cm. There are two end disks on each side of the interaction point at 34.5 cm and 46.5 cm. This article gives an overview of the pixel barrel detector, its mechanical support structure, electronics components, services and its expected performance.Comment: Proceedings of Vertex06, 15th International Workshop on Vertex Detector

Ground motion and macroseismic intensities of a seismic event related to geothermal reservoir stimulation below the city of Basel—observations and modelling

To stimulate a geothermal reservoir below the city of Basel, Switzerland, fluid was injected in December 2006 at high pressure into a 5 km deep borehole. This stimulation led to an increase in local seismicity with the largest seismic event (ML = 3.4) occurring on 2006 December 8. The event was widely felt by the local population, slight non-structural damage to buildings was reported and ultimately this event was the cause to put the geothermal project on hold. In this study, we present recorded ground motion and determinations of macroseismic intensity of the ML 3.4 event as well as simulations of seismic wave propagation and a model to predict macroseismic intensities. As the two models are based on different simplifying assumptions and different underlying physical processes, the predicted intensity distributions exhibit differences in their details. However, the first-order characteristics of the observed macroseismic intensity distribution are well matched. Based on this result, we compute intensities also for hypothetical scenarios of earthquakes with larger magnitude

Building CMS Pixel Barrel Detectur Modules

For the barrel part of the CMS pixel tracker about 800 silicon pixel detector modules are required. The modules are bump bonded, assembled and tested at the Paul Scherrer Institute. This article describes the experience acquired during the assembly of the first ~200 modules.Comment: 5 pages, 7 figures, Vertex200

The false Basel earthquake of May 12, 1021

The Basel (CH) area is a place with an increased seismic hazard. Consequently, it is essential to scrutinize a famous statement by Stumpf (Gemeiner loblicher Eydgnoschafft Stetten, Landen und Völckeren Chronikwirdiger thaaten beschreybung. Durch Johann Stumpffen beschriben, 1548) that allegedly a large earthquake took place in Basel in 1021. This can be disproved unambiguously by applying historical and philosophical method

Parameterization of historical earthquakes in Switzerland

Macroseismic earthquake parameters of historical events have been reassessed in the framework of the update of the Earthquake Catalogue of Switzerland ECOS-09. The Bakun and Wentworth method (Bakun and Wentworth 1997) has been used to assess location, magnitude, and, when possible, focal depth. We apply a two-step procedure. Intensity attenuation is assessed first by fitting a model with a logarithmic and a linear term, using a set of 111 earthquakes. The magnitude range is 3 and 5.8. Then, intensity to magnitude relation is developed. A subset of the 111 events, all having an instrumental moment magnitude, was used to perform this intensity to magnitude calibration. Five final calibration strategies were developed based on different intensity calibration datasets, regionalized or non-regionalized models, and fixed or variable source depth. The final assessment of the macroseismic earthquake parameters is based on an expert judgment procedure, using the results derived from all five strategies, and taking into consideration the historical knowledge available for the particular earthquake. A bootstrap procedure has been applied to assess the uncertainty of parameters. Indicative lower and upper bounds of uncertainty are derived from distributions of location and magnitude for a number of events, obtained through bootstrap sampling of the intensity field and of the single intensity values. The final uncertainties are given in terms of parameter uncertainty classes already used in previous versions of the earthquake catalogue of Switzerlan

Seismic monitoring and analysis of deep geothermal projects in St Gallen and Basel, Switzerland

Monitoring and understanding induced seismicity is critical in order to estimate and mitigate seismic risk related to numerous existing and emerging techniques for natural resource exploitation in the shallow-crust. State of the art approaches for guiding decision making, such as traffic light systems, rely heavily on data such as earthquake location and magnitude that are provided to them. In this context we document the monitoring of a deep geothermal energy project in St Gallen, Switzerland. We focus on the issues of earthquake magnitude, ground motion and macroseismic intensity which are important components of the seismic hazard associated to the project. We highlight the problems with attenuation corrections for magnitude estimation and site amplification that were observed when trying to apply practices used for monitoring regional seismicity to a small-scale monitoring network. Relying on the almost constant source-station distance for events in the geothermal ‘seismic cloud' we developed a simple procedure, calibrated using several ML > 1.3 events, which allowed the unbiased calculation of ML using only stations of the local monitoring network. The approach determines station specific ML correction terms that account for both the bias of the attenuation correction in the near field and amplification at the site. Since the smallest events (ML < −1) were only observed on a single borehole instrument, a simple relation between the amplitude at the central borehole station of the monitoring network and ML was found. When compared against magnitudes computed over the whole network this single station approach was shown to provide robust estimates (±0.17 units) for the events down to ML = −1. The relation could then be used to estimate the magnitude of even smaller events (ML < −1) only recorded on the central borehole station. Using data from almost 2700 events in Switzerland, we then recalibrated the attenuation correction, extending its range of validity from a minimum source-station distance of 20 km down to 1 km. Based on this we could determine the component of the previously derived station specific ML corrections due to local amplification. We analysed ground-motion and detailed macroseismic reports resulting from the 2013 July 20 St Gallen ML = 3.5 ± 0.1 (Mw = 3.3-3.5 ± 0.1) ‘main shock' and compared it to a similar ML = 3.4 ± 0.1 event (Mw = 3.2 ± 0.1) that occurred in 2006 at another deep geothermal project in Basel, Switzerland. Differences in ground motion amplitudes between the Basel and St Gallen events and to an extent, the associated macroseismic observations, were investigated in terms of the different source terms: Mw for long-period motions and the source-corner frequency (related to the source rupture velocity and stress-drop) for short period