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DOE OSTI2026

Efficient Optimization of Plasma Radiation Detector Configurations using Imperfect Inference Models

The configurations of instruments fielded on an experiment affect the amount of information captured and the quality of subsequent inference. Here, we investigate the problem of optimizing plasma x-ray radiation detectors in a magneto-inertial fusion experiment at Sandia National Laboratories. It is impossible to directly measure properties such as the temperature of the thermonuclear fusion plasma produced in these experiments because of the extreme environment and destructive nature of the experiment. Among other diagnostics, several detectors are placed with significant standoff from the fusion target to capture the x-rays emitted by the fusion plasma, which can be used to infer some of its properties. To optimize the configuration of these detectors, a high-fidelity model (HFM) is used for simulating outputs and a low-fidelity model (LFM) is used for inference. We develop methods based on A- and L-optimality criteria that are efficient to compute while explicitly accounting for the discrepancy between the HFM and the LFM. The method allows us to find detector configurations that perform similarly to or better than the configuration obtained using an existing sampling-based optimization method while decreasing computational time by a factor of 50. Supplementary materials for this article are available online, including a standardized description of the materials available for reproducing the work.

Bayesian optimization↗

NASA NTRS2002

Cryogenetically Cooled Field Effect Transistors for Low-Noise Systems

Recent tends in the design, fabrication and use of High-Electron-Mobility-Transistors (HEMT) in low noise amplifiers are reviewed. Systems employing these devices have achieved the lowest system noise for wavelengths greater than three millimeters with relatively modest cryogenic cooling requirements in a variety of ground and space based applications. System requirements which arise in employing such devices in imaging applications are contrasted with other leading coherent detector candidates at microwave wavelengths. Fundamental and practical limitations which arise in the context of microwave application of field effect devices at cryogenic temperatures will be discussed from a component and systems point of view.

Wollack, Edward J.↗

NASA NTRS2002

Cryogenically Cooled Field Effect Transistors for Low-Noise Systems

Wollack, Edward J.↗

NASA NTRS2012

Low-Cost, Rugged High-Vacuum System

A need exists for miniaturized, rugged, low-cost high-vacuum systems. Recent advances in sensor technology have led to the development of very small mass spectrometer detectors as well as other analytical instruments such as scanning electron microscopes. However, the vacuum systems to support these sensors remain large, heavy, and power-hungry. To meet this need, a miniaturized vacuum system was developed based on a very small, rugged, and inexpensive-to-manufacture molecular drag pump (MDP). The MDP is enabled by a miniature, very-high-speed (200,000 rpm), rugged, low-power, brushless DC motor optimized for wide temperature operation and long life. The key advantages of the pump are reduced cost and improved ruggedness compared to other mechanical hig-hvacuum pumps. The machining of the rotor and stators is very simple compared to that necessary to fabricate rotor and stator blades for other pump designs. Also, the symmetry of the rotor is such that dynamic balancing of the rotor will likely not be necessary. Finally, the number of parts in the unit is cut by nearly a factor of three over competing designs. The new pump forms the heart of a complete vacuum system optimized to support analytical instruments in terrestrial applications and on spacecraft and planetary landers. The MDP achieves high vacuum coupled to a ruggedized diaphragm rough pump. Instead of the relatively complicated rotor and stator blades used in turbomolecular pumps, the rotor in the MDP consists of a simple, smooth cylinder of aluminum. This will turn at approximately 200,000 rpm inside an outer stator housing. The pump stator comprises a cylindrical aluminum housing with one or more specially designed grooves that serve as flow channels. To minimize the length of the pump, the gas is forced down the flow channels of the outer stator to the base of the pump. The gas is then turned and pulled toward the top through a second set of channels cut into an inner stator housing that surrounds the motor. The compressed gas then flows down channels in the motor housing to the exhaust port of the pump. The exhaust port of the pump is connected to a commercially available diaphragm or scroll pump.

Sorensen, Paul↗

DOE OSTI2023

Deep underground measurement of B 11 ( α , n ) N 14

The primordial elemental abundance composition of the first stars leads to questions about their modes of energy production and nucleosynthesis. The formation of 12 C has been thought to occur primarily through the 3α process, however, alternative reaction chains may contribute significantly, such as 7 Li (α, γ) 11 B (α,n) 14 N. This reaction sequence cannot only bypass the mass A = 8 stability gap, but could also be a source of neutrons in the first star environment. However, the efficiency of this reaction chain depends on the possible enhancement of its low energy cross section by α-cluster resonances near the reaction threshold. A new study of the reaction 11 B(α,n) 14 N has been undertaken at the CASPAR underground facility at beam energies from 300–700 keV. A 4π neutron detector in combination with pulse shape discrimination at low background conditions resulted in the ability to probe energies lower than previously measured. Further, resonance strengths were determined for both the resonance at a laboratory energy of 411 keV, which was measured for the second time, and for a new resonance at 337 keV that has been measured for the first time. This resonance, found to be significantly weaker than previous estimates, dominates the reaction rate at lower temperatures (T < 0.2 KG) and reduces the reaction rate in first star environments.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

NASA NTRS1963

The Explorer XVI Micrometeoroid Satellite: Description and Preliminary Results for the Period December 16, 1962 Through January 13, 1963

Explorer XVI (1962 Beta Chi l) data that have been analyzed for the period between December 16, 1962 (launch date), and January 13, 1963, indicate that the orbit achieved was close to the predicted orbit. Ten punctures of annealed 0.001-inch-thick beryllium-copper have been used to determine a puncture rate of 0.035 per square foot per day in this material. One puncture of a 0.002-inch-thick sample has also occurred in this period. A tentative evaluation of the puncture rate for the 0.001-inch beryllium-copper in terms of the rate for an equivalent thickness of aluminum has been attempted, and the result has been compared with two different puncture rate estimates. The three micrometeoroid impact detecting systems are operating. Counting rates for the high- and low-sensitivity systems were close to anticipated values near the end of one week. Two of the 0.001-inch-steel-covered grid detectors have been punctured, but none of the 0.003- or 0.006-inch-steel-covered grid detectors have indicated punctures. One of the cadmium sulfide cells indicates three punctures of the 0.00025-inch Mylar cover. None of the 0.002- or 0.003-inch-copper-wire cards have indicated a break in the period covered. Telemetry temperatures were initially higher than expected although they remained well within operating limits. Sensor temperatures have remained within the expected bounds.

Micrometeoroid↗

NASA NTRS1986

Progress in the development of integrating JFET amplifiers

A new approach to infrared detector readout has appeared with the development of integrating JFET amplifiers. This brief progress report includes results on the operation of commercially available devices at a temperature of 40 K, on their sensitivity and on an effort to develop a new JFET with properties optimized for cryogenic applications. Even with presently available devices it will be shown that for applications such as the Space Infrared Telescope Facility (SIRTF), the most strigent sensitivity requirements of noise currents as low as 1 electron/sec in less than 100 seconds of integration can be met.

Low, F. J.↗

NASA NTRS1989

An ac bridge readout for bolometric detectors

The authors have developed a bolometer readout circuit which greatly improves the low-frequency stability of bolometric detectors. The circuit uses an ac bias voltage and two matched bolometers and allows stable dc bolometer operation for integration times greater than 10 s. In astronomical applications the readout allows for qualitatively different observation modes (e.g. staring or slow-drift scanning) which are particularly well suited for space observations and for the use of arrays. In many applications the readout can increase sensitivity. The authors present noise spectra for 4He temperature bolometers with no excess noise at frequencies greater than 0.1 Hz. The measured optical responsivity of a bolometer operated with the present readout is the same as that of a bolometer operated with a conventional readout.

Rieke, F. M.↗

NASA NTRS1989

Balloon-borne measurements of aerosol, condensation nuclei, and cloud particles in the stratosphere at McMurdo Station, Antarctica, during the spring of 1987

Measurements of the vertical profile of particles with condensation nuclei counters and eight channel aerosol detectors at McMurdo Station, Antarctica, in 1987 verified observations made in 1986 concerning the absence of upwelling in the polar vortex and the presence of a condensation nuclei layer in conjunction with the ozone hole region. New observations of a bimodal aerosol size distribution, consisting of a large-particle mode mixed in with the small-particle sulfate mode, at temperatures below -79 C are consistent with the presence of nitric acid-water particles at low concentrations. Higher concentrations of large particles were observed in association with nacreous clouds. An unusual particle layer which contained enhanced concentrations of both the small-particle (sulfate) mode and the large-particle (nitric acid) mode was detected at temperatures below -85 C, suggesting simultaneous nucleation and growth phenomena. The vortex condensation nuclei layer was observed to form at the same time as the ozone hole, indicating that formation of the layer is triggered by photochemical processes and may be important in controlling ozone depletion above 22 km.

Hofmann, D. J.↗

NASA NTRS2014

Design, Fabrication, and Testing of Lumped Element Kinetic inductance Detectors for 3 mm CMB Observations

Kinetic inductance detectors (KIDs) are a promising technology for low-noise, highly-multiplexible mm- and submm-wave detection. KIDs have a number of advantages over other detector technologies, which make them an appealing option in the cosmic microwave background B-mode anisotropy search, including passive frequency domain multiplexing and relatively simple fabrication, but have suffered from challenges associated with noise control. Here we describe design and fabrication of a 20-pixel prototype array of lumped element molybdenum KIDs. We show Q, frequency and temperature measurements from the array under dark conditions. We also present evidence for a double superconducting gap in molybdenum.

cosmic microwave background↗

NASA NTRS2013

Large-aperture Wide-bandwidth Antireflection-coated Silicon Lenses for Millimeter Wavelengths

The increasing scale of cryogenic detector arrays for submillimeter and millimeter wavelength astrophysics has led to the need for large aperture, high index of refraction, low loss, cryogenic refracting optics. Silicon with n 3.4, low loss, and high thermal conductivity is a nearly optimal material for these purposes but requires an antireflection (AR) coating with broad bandwidth, low loss, low reflectance, and a matched coefficient of thermal expansion. We present an AR coating for curved silicon optics comprised of subwavelength features cut into the lens surface with a custom three-axis silicon dicing saw. These features constitute a metamaterial that behaves as a simple dielectric coating.We have fabricated silicon lenses as large as 33.4 cm in diameter with micromachined layers optimized for use between 125 and 165 GHz. Our design reduces average reflections to a few tenths of a percent for angles of incidence up to 30deg with low cross polarization.We describe the design, tolerance, manufacture, and measurements of these coatings and present measurements of the optical properties of silicon at millimeter wavelengths at cryogenic and room temperatures. This coating and lens fabrication approach is applicable from centimeter to submillimeter wavelengths and can be used to fabricate coatings with greater than octave bandwidth.

thermal expansion↗

NASA NTRS1990

New screening methodology to select low outgassing materials for cold, spaceborne optical instruments

Standardized techniques for outgassing tests are developed and set forth for use in the screening of materials for aerospace instruments with cooled sensors, optics, and/or detectors. Materials for optical instruments are discussed in terms of molecular outgassing, and material-outgassing test results are presented which relate to several test conditions. The existing outgassing standard is found to be inadequate, and revised outgassing standards related to four application levels are given. The test protocols are designed for the development of materials for optical instruments that operate in environments with temperatures below 20 C. Consideration is also given to potential molecular contamination in the space environment and to outgas screening of instruments with a variety of sensor/optics/detector temperatures. The standards are designed for use with existing outgassing-test data as well as contamination analyses relating to the instrument being tested.

O'Donnell, T.↗

DOE OSTI2021

Gravitational waves from first-order phase transitions in Majoron models of neutrino mass

We show how the generation of right-handed neutrino masses in Majoron models may be associated with a first-order phase transition and accompanied by the production of a stochastic background of gravitational waves (GWs). We explore different energy scales with only renormalizable operators in the effective potential. If the phase transition occurs above the electroweak scale, the signal can be tested by future interferometers. We consider two possible energy scales for phase transitions below the electroweak scale. If the phase transition occurs at a GeV, the signal can be tested at LISA and provide a complementary cosmological probe to right-handed neutrino searches at the FASER detector. If the phase transition occurs below 100 keV, we find that the peak of the GW spectrum is two or more orders of magnitude below the putative NANOGrav GW signal at low frequencies, but well within reach of the SKA and THEIA experiments. We show how searches of very low frequency GWs are motivated by solutions to the Hubble tension in which ordinary neutrinos interact with the dark sector. We also present general calculations of the phase transition temperature and Euclidean action that apply beyond Majoron models.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2020

The impact of the charge barrier height on Germanium (Ge) detectors with amorphous-Ge contacts for light dark matter searches

Germanium (Ge) detectors with ability of measuring a single electron–hole (e–h) pair are needed in searching for light dark matter (LDM) down to the MeV scale. We investigate the feasibility of Ge detectors with amorphous-Ge (a-Ge) contacts to achieve the sensitivity of measuring a single e-h pair, which requires extremely low leakage current. Three Ge detectors with a-Ge contacts are used to study the charge barrier height for blocking electrons and holes. Using the measured bulk leakage current and the Döhler–Brodsky model, we obtain the values for charge barrier height and the density of localized energy states near the Fermi energy level for the top and bottom contacts, respectively. We predict that the bulk leakage current is extremely small and can be neglected at helium temperature ( $$\sim $$ ~ 4 K). Thus, Ge detectors with a-Ge contacts possess the potential to measure a single e–h pair for detecting LDM particles.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2022

Development and construction status of the Mu2e electromagnetic calorimeter mechanical structures

Abstract The Mu2e experiment at Fermilab will search for the CLFV neutrino-less coherent conversion of a muon into an electron in the field of an aluminum nucleus. The observation of this process would be the evidence of physics beyond the Standard Model. Mu2e comprises a straw-tracker, an electromagnetic calorimeter and an external veto for cosmic rays. The calorimeter provides electron identification, a fast trigger and aids track reconstruction. It is a state-of-the-art crystal calorimeter and employs 1340 pure CsI crystals readout by UV-extended SiPM and fast electronics. The design consists of two identical annular disks positioned at the relative distance of 70 cm downstream the target.The hostile Mu2e conditions (total ionizing dose of 12 krad and a neutron fluence of 5 × 10 10 n/cm 2 @ 1 MeVeq (Si)/y, 1 T magnetic field and vacuum level of 10 −4 Torr) posed tight constraints on the mechanical structures and materials choice. The support structure of the two crystal matrices employs two aluminum hollow rings and parts made of open-cell vacuum-compatible carbon fiber. SiPMs and front-end electronics for each crystal are assembled in one mechanical unit inserted in a machined copper holder. The units are supported by a plate made of vacuum-compatible material. The plate integrates the cooling system made of a network of copper lines flowing a low temperature fluid and placed in thermal contact with the copper holders. The DAQ is hosted in aluminum crates positioned on the lateral surface of the disks. The crates also integrate the DAQ electronics cooling system. We review the constraints on the calorimeter structures design, the development of all the structural components, including the simulations that have determined the materials and technological choices and the specifications of the cooling station, components production and quality assurance tests, the procedures for detector assembly, transportation and installation in the experimental area.

Instruments & Instrumentation↗

DOE OSTI2020

Optical Design and Characterization of 40-GHz Detector and Module for the BICEP Array

Families of cosmic inflation models predict a primordial gravitational-wave background that imprints B-mode polarization pattern in the cosmic microwave background (CMB). High-sensitivity instruments with wide frequency coverage and well-controlled systematic errors are needed to constrain the faint B-mode amplitude. We have developed antenna-coupled transition edge sensor arrays for high-sensitivity polarized CMB observations over a wide range of millimeter-wave bands. BICEP array, the latest phase of the BICEP/Keck experiment series, is a multi-receiver experiment designed to search for inflationary B-mode polarization to a precision σ(r) between 0.002 and 0.004 after 3 full years of observations, depending on foreground complexity and the degree of lensing removal. We describe the electromagnetic design and measured performance of BICEP array’s low-frequency 40-GHz detector, their packaging in focal plane modules, and optical characterization including efficiency and beam matching between polarization pairs. We summarize the design and simulated optical performance, including an approach to improve the optical efficiency due to mismatch losses. Here, we report the measured beam maps for a new broadband corrugation design to minimize beam differential ellipticity between polarization pairs caused by interactions with the module housing frame, which helps minimize polarized beam mismatch that converts CMB temperature to polarization (T→P) anisotropy in CMB maps.

47 OTHER INSTRUMENTATION↗

NASA NTRS1986

Development of 30 micrometers extrinsic silicon multiplexed infrared deterctor array

Two hybrid infrared (IR) detector arrays of antimony-doped silicon (Si:Sb) were produced and tested to evaluate their potential for use in low-background IR astronomy applications. The format of the arrays is 58 x 62 elements, with 76 micron-square pixels. A random-access, switched metal-oxide semiconductor field effect transistor (MOSFET) silicon multiplexer is used to read out the array elements. Reduced-background tests of signal, noise, and noise equivalent power were conducted over the temperature range 3.2 to 12 K. The arrays were found to have good sensitivity and good uniformity.

Orias, G.↗

NASA NTRS1990

Space-borne He-3 refrigerator

A space-compatible He-3 refrigerator is being developed for cooling the bolometric detectors of the Far Infrared Photometer (FIRP) in the Infrared Telescope in Space (IRTS). The refrigerator is self-contained and compact, and can be recycled in zero gravity with low power dissipation (20 mW or less). A laboratory prototype that contains 2 STP cu dm of He-3 has been successfully cycled upside-down, i.e., against gravity, thus proving the feasibility of the cycle in zero gravity. Sintered copper confines the He-3 to the evaporator during the low temperature phase. Temperatures as low as 280 mK have been achieved with this configuration. Other types of porous material which have lower mass density are currently under investigation.

Duband, L.↗