Status report of the CERN microwave axion experiment

"Light Shining Through the Wall" experiments can probe the existence of "axion like particles" through their weak coupling to photons. We have adapted such an experiment to the microwave regime and constructed the table top apparatus. This work presents an overview of the experimental setup and then focuses on our latest measurement run and its results. By operating the apparatus within a superconducting MRI magnet, competitive exclusion limits for axion like particles to the first generation optical light shining through the wall experiments have been achieved.Comment: Contributed to the 9th Patras Workshop on Axions, WIMPs and WISPs, Mainz, June 24-28, 201

Status report of the CERN light shining through the wall experiment with microwave axions and related aspects

One way to proof or exclude the existence of axion like particles is a microwave light shining through the wall experiment. In this publication we will emphasize on the engineering aspects of such a setup, currently under development at CERN. One critical point, to achieve meaningful results, is the electromagnetic shielding between axion-emitter and -receiver cavity, which needs to be in the order of 300 dB to improve over existing experimental bounds. The RF leakage or electromagnetic crosstalk between both cavities must be well controlled and quantified during the complete duration of the experiment. A very narrow band (in the 10^-6 Hz range) homodyne detection method is used to reveal the axion signal from background thermal noise. The current status of the experiment is presented.Comment: Contributed to the "7th Patras Workshop on Axions, WIMPs and WISPs", Mykonos June 26 - July 1 201

First-Principles Calculation of the Cu-Li Phase Diagram

We present first-principles calculations of the solid-state portion of the Cu-Li phase diagram based on the cluster expansion formalism coupled with the use of (i) bond length-dependent transferable force constants and lattice dynamics calculations to model of vibrational disorder and (ii) lattice gas Monte Carlo simulations to model configurational disorder. These calculations help settle the existence of additional phases in the Cu-Li phase diagram that have been postulated, but not yet clearly established. Our calculations predict the presence of at least one additional phase and the associated predicted phase transitions are consistent with our electrochemical measurements, which exhibit clear plateaus in the electromotive force-composition curve

Status report and first results of the microwave LSW experiment at CERN

To detect or exclude the existence of hidden sector photons or axion like particles, a table-top "microwaves shining through the wall" experiment has been set up at CERN. An overview of the experimental layout is given, the technical challenges involved are reviewed and the measurement procedure including data-evaluation and its results to date are shown.Comment: Contributed to the 8th Patras Workshop on Axions, WIMPs and WISPs, Chicago, July 18-22, 201

Analog to digital conversion in beam instrumentation systems

Analog to digital conversion is a very important part of almost all beam instrumentation systems. Ideally, in a properly designed system, the used analog to digital converter (ADC) should not limit the system performance. However, despite recent improvements in ADC technology, quite often this is not possible and the choice of the ADC influences significantly or even restricts the system performance. It is therefore very important to estimate the requirements for the analog to digital conversion at an early stage of the system design and evaluate whether one can find an adequate ADC fulfilling the system specification. In case of beam instrumentation systems requiring both, high time and amplitude resolution, it often happens that the system specification cannot be met with the available ADCs without applying special processing to the analog signals prior to their digitisation. In such cases the requirements for the ADC even influence the system architecture. This paper aims at helping the designer of a beam instrumentation system in the process of selecting an ADC, which in many cases is iterative, requiring a trade off between system performance, complexity and cost. Analog to digital conversion is widely and well described in the literature, therefore this paper focusses mostly on aspects related to beam instrumentation. The ADC fundamentals are limited to the content presented as an introduction during the CAS one-hour lecture corresponding to this paper.Comment: 36 pages, contribution to the CAS - CERN Accelerator School: Beam Instrumentation, 2-15 June 2018, Tuusula, Finlan

Youth Homelessness: The Impact of Supportive Relationships on Recovery

Abstract AIM: To test a model based on Peplau’s theory of Interpersonal Relations, which examines the influence of a network of service providers, perceptions of social supports and perceptions of family relations on a homeless youth’s perceptions of recovery. BACKGROUND: Homeless youth comprise an extremely disenfranchised group and have been recognized as one of the fastest growing sub-groups within the homeless population. Homeless youth face impaired access to health and social services. They are often left unsupported and lack social and familial support or relationships with service providers. Homeless youth left unsupported frequently sink into a cycle of homelessness that extends into adulthood. METHODS: This study is a secondary analysis and used a subsample of the original Youth Matters study. A predictive, non-experimental design was used to test the relationship of a network of service providers, perceived social support and perceived family relations on perceptions of recovery in the homeless youth population. A sample of homeless youth (n= 187) in Ontario, Canada were interviewed at six month intervals over a 2.5 year period. Hierarchical multiple regression analysis was used. RESULTS: Network of service providers, perceived social supports and perceived family relations explained 21.8% of the variance in homeless youth perceptions of recovery. Perceived social support and family relations were significantly, positively correlated to perceptions of recovery. Network of service providers was not significantly correlated to perceptions of recovery. CONCLUSIONS: The findings suggest that stronger social supports and family relations may contribute to increased perceptions of recovery among homeless youth. IMPLICATIONS FOR FUTURE PRACTICE: Health and social service providers must understand the importance of implementing interventions that foster supportive relationships and networks of support in the homeless youth population. KEYWORDS: homeless; youth; recovery; social support; family; service provide

Tid1/Rdh54 Promotes Colocalization of Rad51 and Dmc1 During Meiotic Recombination

Two RecA homologs, Rad51 and Dmc1, assemble as cytologically visible complexes (foci) at the same sites on meiotic chromosomes. Time course analysis confirms that co-foci appear and disappear as the single predominant form. A large fraction of co-foci are eliminated in a red1 mutant, which is expected as a characteristic of the interhomolog-specific recombination pathway. Previous studies suggested that normal Dmc1 loading depends on Rad51. We show here that a mutation in TID1/RDH54, encoding a RAD54 homolog, reduces Rad51-Dmc1 colocalization relative to WT. A rad54 mutation, in contrast, has relatively little effect on RecA homolog foci except when strains also contain a tid1/rdh54 mutation. The role of Tid1/Rdh54 in coordinating RecA homolog assembly may be very direct, because Tid1/Rdh54 is known to physically bind both Dmc1 and Rad51. Also, Dmc1 foci appear early in a tid1/rdh54 mutant. Thus, Tid1 may normally act with Rad51 to promote ordered RecA homolog assembly by blocking Dmc1 until Rad51 is present. Finally, whereas double-staining foci predominate in WT nuclei, a subset of nuclei with expanded chromatin exhibit individual Rad51 and Dmc1 foci side-by-side, suggesting that a Rad51 homo-oligomer and a Dmc1 homo-oligomer assemble next to one another at the site of a single double-strand break (DSB) recombination intermediate

Rad52 Associates with RPA and Functions with Rad55 and Rad57 to Assemble Meiotic Recombination Complexes

We show that the Saccharomyces cerevisiae recombination protein Rad52 and the single-strand DNA-binding protein RPA assemble into cytologically detectable subnuclear complexes (foci) during meiotic recombination. Immunostaining shows extensive colocalization of Rad52 and RPA and more limited colocalization of Rad52 with the strand exchange protein Rad51. Rad52 and RPA foci are distinct from those formed by Rad51, and its meiosis-specific relative Dmc1, in that they are also detected in meiosis during replication. In addition, RPA foci are observed during mitotic S phase. Double-strand breaks (DSBs) promote formation of RPA, Rad52, and Rad51 foci. Mutants that lack Spo11, a protein required for DSB formation, are defective in focus formation, and this defect is suppressed by ionizing radiation in a dose-dependent manner. DSBs are not sufficient for the appearance of Rad51 foci; Rad52, Rad55, and Rad57 are also required supporting a model in which these three proteins promote meiotic recombination by promoting the assembly of strand exchange complexes

First results of the CERN Resonant WISP Search (CROWS)

The CERN Resonant WISP Search (CROWS) probes the existence of Weakly Interacting Sub-eV Particles (WISPs) like axions or hidden sector photons. It is based on the principle of an optical light shining through the wall experiment, adapted to microwaves. Critical aspects of the experiment are electromagnetic shielding, design and operation of low loss cavity resonators and the detection of weak sinusoidal microwave signals. Lower bounds were set on the coupling constant $g = 4.5 \cdot 10^{-8}$GeV$^{-1}$ for axion like particles with a mass of $m_a = 7.2 \mu$eV. For hidden sector photons, lower bounds were set for the coupling constant $\chi = 4.1 \cdot 10^{-9}$ at a mass of $m_{\gamma'} = 10.8 \mu$eV. For the latter we were probing a previously unexplored region in the parameter space