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Register a new userDemonstration of wideband metal mesh filters for submillimeter astrophysics using flexible printed circuits
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We developed a wideband quasi-optical band-pass filter covering 170-520 GHz by exploiting the recent advancements in commercially available flexible printed circuit (FPC) fabrication technologies. We designed and fabricated a three-layered stack of loaded hexagonal grid metal meshes using a copper pattern with a narrowest linewidth of $50~mumathrm{m}$ on a polyimide substrate. The measured frequency pass-band shape was successfully reproduced through a numerical simulation using a set of parameters consistent with the dimensions of the fabricated metal meshes. FPC-based metal mesh filters will provide a new pathway toward the on-demand development of millimeter/submillimeter-wave quasi-optical filters at low cost and with a short turnaround time.
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ALMA has been operating since 2011, but has not yet been populated with the full suite of intended frequency bands. In particular, ALMA Band 2 (67-90 GHz) is the final band in the original ALMA band definition to be approved for production. We aim to produce a wideband, tuneable, sideband-separating receiver with 28 GHz of instantaneous bandwidth per polarisation operating in the sky frequency range 67-116 GHz. Our design anticipates new ALMA requirements following the recommendations in the 2030 ALMA Development Roadmap. The cryogenic cartridge is designed to be compatible with the ALMA Band 2 cartridge slot, where the coldest components -- the feedhorns, orthomode transducers, and cryogenic low noise amplifiers -- operate at a temperature of 15 K. We use multiple simulation methods and tools to optimise our designs for both the passive optics and the active components. The cryogenic cartridge interfaces with a room temperature cartridge hosting the local oscillator (LO) and the downconverter module. This warm cartridge is largely based on GaAs semiconductor technology and is optimised to match the cryogenic receiver bandwidth with the required instantaneous LO tuning range. Our collaboration has designed, fabricated, and tested multiple technical solutions for each of the components, producing a state-of-the-art receiver covering the full ALMA Band 2 & 3 atmospheric window. The receiver is suitable for deployment on ALMA in the coming years, and is capable of dual-polarisation, sideband-separating observations in intermediate frequency bands spanning 4-18 GHz, for a total of 28 GHz on-sky bandwidth per polarisation channel. We conclude that the 67-116 GHz wideband implementation for ALMA Band 2 is now feasible, and this receiver is a compelling instrumental upgrade that will enhance observational capabilities and scientific reach.
The Large Observatory for X-ray Timing (LOFT) was one of the M3 missions selected for the phase A study in the ESAs Cosmic Vision program. LOFT is designed to perform high-time-resolution X-ray observations of black holes and neutron stars. The main instrument on the LOFT payload is the Large Area Detector (LAD), a collimated experiment with a nominal effective area of ~10 m 2 @ 8 keV, and a spectral resolution of ~240 eV in the energy band 2-30 keV. These performances are achieved covering a large collecting area with more than 2000 large-area Silicon Drift Detectors (SDDs) each one coupled to a collimator based on lead-glass micro-channel plates. In order to reduce the thermal load onto the detectors, which are open to Sky, and to protect them from out of band radiation, optical-thermal filter will be mounted in front of the SDDs. Different options have been considered for the LAD filters for best compromise between high quantum efficiency and high mechanical robustness. We present the baseline design of the optical-thermal filters, show the nominal performances, and present preliminary test results performed during the phase A study.
Future far-infrared astronomy missions will need large arrays of detectors with exceptionally low noise-equivalent power (NEP), with some mission concepts calling for thousands of detectors with NEPs below a few $times 10^{-20}$ W/$sqrt{mathrm{Hz}}$. Though much progress has been made toward meeting this goal, such detector systems do not exist today. In this work, we present a device that offers a compelling path forward: the longitudinal proximity effect (LoPE) transition-edge sensor (TES). With a chemically-stable and mechanically-robust architecture, the LoPE TES we designed, fabricated, and characterized also exhibits unprecedented sensitivity, with a measured electrical NEP of $8 times 10^{-22}$ W/$sqrt{mathrm{Hz}}$. This represents a >100x advancement of the state-of-the-art, pushing TES detectors into the regime where they may be employed the achieve to goals of even the most ambitious large and cold future space instruments.
We report the characterisation of printed circuit boards (PCB) metal powder filters and their influence on the effective electron temperature which is as low as 22 mK for a quantum dot in a silicon MOSFET structure in a dilution refrigerator. We investigate the attenuation behaviour (10 MHz- 20 GHz) of filter made of four metal powders with a grain size below 50 um. The room-temperature attenuation of a stainless steel powder filter is more than 80 dB at frequencies above 1.5 GHz. In all metal powder filters the attenuation increases with temperature. Compared to classical powder filters, the design presented here is much less laborious to fabricate and specifically the copper powder PCB-filters deliver an equal or even better performance than their classical counterparts.
This paper describes the open-source code Enzo, which uses block-structured adaptive mesh refinement to provide high spatial and temporal resolution for modeling astrophysical fluid flows. The code is Cartesian, can be run in 1, 2, and 3 dimensions, and supports a wide variety of physics including hydrodynamics, ideal and non-ideal magnetohydrodynamics, N-body dynamics (and, more broadly, self-gravity of fluids and particles), primordial gas chemistry, optically-thin radiative cooling of primordial and metal-enriched plasmas (as well as some optically-thick cooling models), radiation transport, cosmological expansion, and models for star formation and feedback in a cosmological context. In addition to explaining the algorithms implemented, we present solutions for a wide range of test problems, demonstrate the codes parallel performance, and discuss the Enzo collaborations code development methodology.
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