6 Search Results

Future measurements of the millimeter-wavelength sky require a low-loss superconducting microstrip, typically made from niobium and silicon-nitride, coupling the antenna to detectors. Here, we propose a simple device for characterizing these low-loss microstrips at 150 GHz. In our device we illuminate an antenna with a thermal source and compare the measured power at 150 GHz transmitted down microstrips of different lengths. The power measurement is made using Microwave Kinetic Inductance Detectors (MKIDs) fabricated directly onto the microstrip dielectric, and comparing the measured response provides a direct measurement of the microstrip loss. Our proposed structure provides a simple device (4 layersmore » and a DRIE etch) for characterizing the dielectric loss of various microstrip materials and substrates. We present initial results using these devices. We demonstrate that the millimeter wavelength loss of microstrip lines, a few tens of millimeters long, can be measured using a practical aluminum MKID with a black body source at a few tens of Kelvin.« less

Here, this work shows how it is possible to reconstruct SuperKEKB’s beam parameters using a Neural Network with beamstrahlung signal from the Large Angle Beamstrahlung Monitor (LABM) as input. We describe the device, the model, and discuss the results.

The cold polycrystalline beryllium reflector-filter concept has been used to enhance the cold neutron emission of cryogenic hydrogen moderators, while suppressing the intermediate wavelength and fast neutron emission at the same time. While suppressing the fast neutron emission is often desired, the suppression of intermediate wavelength neutrons is often unwelcome. It has been hypothesized that replacing the polycrystalline reflector-filter concept with a single-crystal reflector-filter concept would overcome the suppression of intermediate wavelength neutrons and thereby extend the usability of the reflector-filter concept to shorter but still important wavelengths. In this paper we present the first experimental data on a single-crystalmore » reflector-filter and compare experimental results with hypothesized performance. We find that a single-crystal reflector-filter retains the long-wavelength benefit of the polycrystalline reflector-filter, without suffering the same loss of important intermediate wavelength neutrons. Ultimately, this finding extends the applicability of the reflector-filter concept to intermediate wavelengths, and furthermore indicates that the reflector-filter benefits arise from its interaction with fast (background) neutrons, not with intermediate wavelength neutrons of potential interest in many types of neutron scattering.« less

Fabrication of coplanar waveguide resonators with internal quality factors near 10⁶ remains challenging. In this work, high-purity single crystal superconductors are implemented through metamorphic epitaxial aluminum that is grown via molecular beam epitaxy on silicon and sapphire substrates. X- ray diffraction and scanning transmission electron microscopy indicate an abrupt highly ordered interface that results in crystal relaxation within a few monolayers of the substrate interface and no measurable interfacial contamination. Quarter- wave coplanar waveguide resonators are fabricated using optical lithography and measured at temperatures below 100 mK. Post measurement characterization with charge contrast imaging in a scanning electron microscope identifiesmore » processing artifacts at the waveguide sidewalls, on the exposed substrate area and on the exposed aluminum surface. Of primary importance are processing induced corrosion defects on aluminum sidewalls, nanoparticle contamination, and photoresist residue that are difficult to remove without affecting the superconductor material. Likely correlations between these artifacts and the measured quality factor are discussed in context of device to device variations in resonator performance.« less

Here, we review some previous results on electron-cloud dynamics and accumulation and the impact of electron clouds on ion beam dynamics, and assess these in the context of a magnetic-quadrupole-based heavy-ion fusion driver. We present a new analysis which exploits analytic solution of linearized envelope equations between accelerating gaps to derive a set of mapping equations which we use to extrapolate from previously obtained particle-simulation results for a beam transport system to an HIF driver.