Design and Testing of 100 mK High-voltage Electrodes for AEgIS

AbstractThe AEgIS (Antimatter Experiment: Gravity, Interferometry, Spectroscopy) experiment at CERN has as main goal to perform the first direct measurement of the Earth's gravitational acceleration on antihydrogen atoms within 1% precision. To reach this precision, the antihydrogen should be cooled down to about 100 mK to reduce its random vertical velocity. This is obtained by mounting a Penning trap consisting of multiple high-voltage electrodes on the mixing chamber of a dilution refrigerator with cooling capacity of 100μW at 50 mK. A design of the high-voltage electrodes is made and experimentally tested at operating conditions. The high-voltage electrodes are made of sapphire with four gold sputtered electrode sectors on it. The electrodes have a width of 40mm, a height of 18mm and a thickness of 5.8mm and for performance testing are mountedto the mixing chamber of a dilution refrigerator with a 250μm thick indium foil sandwiched inbetween the two to increase the thermal contact. A static heat load of 120nW applied to the top surface of the electrode results in a maximum measured temperature of 100mK while the mixing chamber is kept at a constant temperature of 50mK. The measured totalthermal resistivity lies in the range of 210-260cm2K4W−1, which is much higher than expected from literature. Further research needs to be done to investigate this

Development of a novel method for the exploration of the thermal response of superfluid helium cooled superconducting cables to pulse heat loads

Management of transient heat deposition in superconducting magnets and its extraction from the aforementioned is becoming increasingly important to bring high energy particle accelerator performance to higher beam energies and intensities. Precise knowledge of transient heat deposition phenomena in the magnet cables will permit to push the operation of these magnets as close as possible to their current sharing limit, without unduly provoking magnet quenches. With the prospect of operating the Large Hadron Collider at CERN at higher beam energies and intensities an investigation into the response to transient heat loads of LHC magnets, operating in pressurized superfluid helium, is being performed. The more frequently used approach mimics the cable geometry by resistive wires and uses Joule-heating to deposit energy. Instead, to approximate as closely as possible the real magnet conditions, a novel method for depositing heat in cable stacks made out of superconducting magnet-cables has been developed. The goal is to measure the temperature difference as a function of time between the cable stack and the superfluid helium bath depending on heat load and heat pulse length. The heat generation in the superconducting cable and precise measurement of small temperature differences are major challenges. The functional principle and experimental set-up are presented together with proof of principle measurements

High-sensitivity tool for studying phonon related mechanical losses in low loss materials

Fundamental mechanical loss mechanisms exist even in very pure materials, for instance, due to the interactions of excited acoustic waves with thermal phonons. A reduction of these losses in a certain frequency range is desired in high precision instruments like gravitational wave detectors. Systematic analyses of the mechanical losses in those low loss materials are essential for this aim, performed in a highly sensitive experimental set-up. Our novel method of mechanical spectroscopy, cryogenic resonant acoustic spectroscopy of bulk materials (CRA spectroscopy), is well suited to systematically determine losses at the resonant frequencies of the samples of less than 10^(-9) in the wide temperature range from 5 to 300 K. A high precision set-up in a specially built cryostat allows contactless excitation and readout of the oscillations of the sample. The experimental set-up and measuring procedure are described. Limitations to our experiment due to external loss mechanisms are analysed. The influence of the suspension system as well as the sample preparation is explained.Comment: 4 pages, 3 figures, proceedings of PHONONS07, submitted to Journal of Physics: Conference Serie

Heat transfer at dielectric-metallic interfaces in the ultra-low temperature range

In the framework of the AEgIS project a series of steady state and dynamic heat transfer measurements at ultra-low temperatures was conducted in the Central Cryogenic Laboratory at CERN. Two sandwich setups, simulating the behaviour of ultra-cold AEgIS electrodes, were investigated and compared, namely: a sapphire − indium − copper and a sapphire − titanium − gold − indium − copper sandwich. The total thermal resistivity of both sandwich setups was evaluated as a function of the influence of normal and superconducting thin layers and multiple dielectric − metallic interfaces in terms of Kapitza resistance. The resulting limitations of the electrode’s design are presented

Heavy metal distribution in the eggs of four species of ardeids and in the body tissues of Egretta garzetta in some

本研究采用电感耦合等离子质谱（ICP-MS）对福建岛屿白鹭（Egrettagarzetta）、池鹭（Ardeolabacchus）、黄嘴白鹭（Egrettaeulophotes）和岩鹭（Egrettasacra）卵的不同部位及白鹭雏鸟各组织中的重金属进行检测，测定了铬（Cr）、锰（Mn）、镍（Ni）、铜（Cu）、锌（Zn）、镉（Cd）和铅（Pb）等7种重金属元素的含量。对重金属元素在卵的各部位及雏鸟各组织中的含量差异进行研究，探讨重金属在鹭卵及白鹭雏鸟中的分布规律及积累趋势。为福建鹭鸟栖息地环境评价提供依据，并为今后研究重金属残留对鸟类的影响提供数据。 本研究结果显示，7种重金属元素在各样本...The concentrations of 7 kinds of heavy metals (Cr, Mn, Ni, Cu, Zn, Cd and Pb) in the different parts of eggs of little egrets (Egretta garzetta), Chinese pond herons (Ardeola bacchus), Chinese egret (E. eulophotes) and eastern reef herons (E. sacra) in Fujian province were measured with ICP-MS. The concentrations of these heavy metals in the nestling body tissues of little egrets were also measure...学位：理学硕士院系专业：生命科学学院生物学系_动物学学号：2172006115211

Mechanical losses in low loss materials studied by Cryogenic Resonant Acoustic spectroscopy of bulk materials (CRA spectroscopy)

Mechanical losses of crystalline silicon and calcium fluoride have been analyzed in the temperature range from 5 to 300 K by our novel mechanical spectroscopy method, cryogenic resonant acoustic spectroscopy of bulk materials (CRA spectrocopy). The focus lies on the interpretation of the measured data according to phonon-phonon interactions and defect induced losses in consideration of the excited mode shape.Comment: 4 pages, 4 figures, proceedings of the PHONONS 2007, submitted to Journal of Physics: Conference Serie

Development of light and highly radiation transparent cryostats for FCC detector magnets:First analyses of insulation materials

For both versions of the Future Circular Collider, the electron-positron FCC ee$^+$, requiring a 2 T/4 m bore solenoid for particles spectrometry, and the hadron-hadron FCC hh, CERN is developing an innovative design for the detector solenoids, to enable their positioning inside the calorimeters directly surrounding the inner tracker. For this to happen, the cryostat design has to be optimized to achieve minimum radiation length. The novel design consists of a sandwich of thin inner and outer metallic shells for vacuum tightness, supported by an insulating material with sufficient mechanical resistance paired with lowest thermal conductivity, like Cryogel, a flexible aerogel structure (density 0.16 g/cm$^3$), or glass spheres (e.g. type K1 manufactured by 3M, with 65 μm diameter and density of 0.125 g/cm$^3$). These materials would allow constructing a 4 m bore, 6 m long cryostat with a 250 mm total thickness, a heat load less than 400 W on the cold mass and 10 kW on the thermal shield. In this paper, design options are discussed and methods for qualifying the materials presented

Mechanical Q-factor measurements on a test mass with a structured surface

We present mechanical Q-factors (quality factors) of a crystalline quartz test mass with a nano-structured surface, measured in the temperature regime from 5 to 300 K. The nano-structure was a grating with a period of 2 mu m and a depth of about 0.1 mu m. Comparative measurements were performed on the plain substrate and on the structured test mass with different numbers of SiO2/Ta2O5 coating layers. The measurements at different stages of the test mass fabrication process show that the surface distortion induced by the nanostructure does not severely lower the mechanical Q-factor of the substrate. Damping due to a multi-layer coating stack was found to be orders of magnitude higher. The results provide vital information concerning the potential usage of low-thermal noise nano-structured test masses in future generations of high-precision laser interferometers and in current attempts to measure quantum effects of macroscopic mirror oscillators.DFG/SFB/Transregio

Experimental study of double beta decay modes using a CdZnTe detector array

An array of sixteen 1 cm^3 CdZnTe semiconductor detectors was operated at the Gran Sasso Underground Laboratory (LNGS) to further investigate the feasibility of double-beta decay searches with such devices. As one of the double-beta decay experiments with the highest granularity the 4 x 4 array accumulated an overall exposure of 18 kg days. The setup and performance of the array is described. Half-life limits for various double-beta decay modes of Cd, Zn and Te isotopes are obtained. No signal has been found, but several limits beyond 10^20 years have been performed. They are an order of magnitude better than those obtained with this technology before and comparable to most other experimental approaches for the isotopes under investigation. An improved limit for the beta^+/EC decay of Te 120 is given.Comment: 6 pages, 5 figure

On the mechanical quality factors of cryogenic test masses from fused silica and crystalline quartz

Current interferometric gravitational wave detectors (IGWDs) are operated at room temperature with test masses made from fused silica. Fused silica shows very low absorption at the laser wavelength of 1064 nm. It is also well suited to realize low thermal noise floors in the detector signal band since it offers low mechanical loss, i. e. high quality factors (Q factors) at room temperature. However, for a further reduction of thermal noise, cooling the test masses to cryogenic temperatures may prove an interesting technique. Here we compare the results of Q factor measurements at cryogenic temperatures of acoustic eigenmodes of test masses from fused silica and its crystalline counterpart. Our results show that the mechanical loss of fused silica increases with lower temperature and reaches a maximum at 30 K for frequencies of slightly above 10 kHz. The losses of crystalline quartz generally show lower values and even fall below the room temperature values of fused silica below 10 K. Our results show that in comparison to fused silica, crystalline quartz has a considerably narrower and lower dissipation peak on cooling and thus has more promise as a test mass material for IGDWs operated at cryogenic temperatures. The origin of the different Q factor versus temperature behavior of the two materials is discussed