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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Characterization of MKIDs for CMB Observation at 220 GHz With the South Pole Telescope

We present an updated design of the 220 GHz microwave kinetic inductance detector (MKID) pixel for SPT-3G+, the next-generation camera for the South Pole Telescope. We show results of the dark testing of a 63-pixel array with mean inductor quality factor $Q_{i} = 4.8 \times 10^{5}$, aluminum inductor transition temperature $T_{c} = 1.19$K, and kinetic inductance fraction $\alpha _{k} = 0.32$. We optically characterize both the microstrip-coupled and CPW-coupled resonators, and find both have a spectral response close to prediction with an optical efficiency of $\eta \sim 70\%$. However, we find slightly lower optical response on the lower edge of the band than predicted, with neighboring dark detectors showing more response in this region, though at level consistent with less than 5% frequency shift relative to the optical detectors. The detectors show polarized response consistent with expectations, with a cross-polar response of $\sim 10\%$for both detector orientations.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2024

MgB$_{2}$ Coating by HPCVD for 1.3-GHz Superconducting RF Cavities

While MgB 2 possesses promising material parameters for SRF cavities with higher Q, higher gradient, and higher operation temperatures than Nb cavities, such cavity properties have not been demonstrated using MgB 2 . As part of a continuing effort to fabricate MgB 2 -coated SRF cavities by hybrid physical chemical vapor deposition (HPCVD), we present here an HPCVD system design for coating the inside wall of 1.3-GHz copper cavities with MgB 2 . The cavity is heated using a pair of clamshell resistive heaters that directly contact the cavity body. Here, the new heater design is more compact and requires less power to reach the deposition temperature (~500°C for MgB 2 deposition on copper.) Preliminary test of MgB 2 films grown on small copper substrates, mounted at different locations on the cavity, shows T c of 28.4 ~ 34.3 K, measured by AC susceptibility.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2026

High-$Q_0$ treatment of CEBAF 1.5 GHz SRF cavities

The Continuous Electron Beam Accelerator Facility (CEBAF) was the first large-scale accelerator to employ superconducting radiofrequency (SRF) cavities for continuous-wave operation. Ongoing research and development efforts continue to focus on increasing the intrinsic quality factor (Q 0 ) of these cavities in order to reduce cryogenic losses while maintaining operational gradients. Here, in this work, we report on the application of high-Q 0 surface treatments to single-cell and multicell C100 and C75 style 1.5 GHz niobium cavities used in the CEBAF accelerator. Nitrogen infusion and oxygen alloying via medium-temperature baking were applied under heat-treatment constraints relevant to existing cavity hardware. Both processes yielded substantial improvements in Q 0 at moderate accelerating gradients, achieving values of approximately 2 × 10 10 at 2.07 K and 20 MV/m. The effectiveness of nitrogen infusion at reduced annealing temperatures and the successful extension of oxygen alloying to multicell cavities are demonstrated. These results establish viable pathways for implementing high-Q 0 treatments in CEBAF-compatible cavities and support future integration into cryomodules for reduced operational cryogenic load.

Dhakal, Pashupati [Thomas Jefferson National Accel↗
DOE OSTI2022

Toward Emittance Measurements at 11.7 GHz Short-Pulse High-Gradient RF Gun

A short pulse high gradient RF gun has been recently tested at Argonne Wakefield Accelerator (AWA) facility. The carried-out test showed that the 1,5-cell gun was able to inject 3 MeV, up to 100 pC bunches at room tem-perature being fed by 9 ns up to 300 MW 11.7 GHz puls-es. The cathode field was as high as about 400 MV/m. So high field is aimed to mitigate repealing Coulomb forces substantially. In accordance with simulations the emit-tance could be as low as less than 0.2 mcm. To obtain so low emittance in the experiment, the gun is assumed to be equipped with a downstream linac to be fed from the same power extractor as the gun itself. Here we report design of the RF power distribution system splitting RF power among the gun and the linac, results of low-power tests, and emittance measurement plans for upcoming new experiment at AWA.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

PRELIMINARY RESULTS OF MAGNETIC AND TEMPERATURE MAP SYSTEM FOR 3 GHz SUPERCONDUCTING RADIO FREQUENCY CAVITIES

Su­per­con­duct­ing radio fre­quency (SRF) cav­i­ties are fun­da­men­tal build­ing blocks of mod­ern par­ti­cle ac­cel­er­a­tors. A sur­face re­sis­tance in the tens of nanoOhm range is achieved when cool­ing these cav­i­ties to liq­uid he­lium tem­per­a­ture, ~2 - 4 K. One of the lead­ing sources of resid­ual losses in SRF cav­i­ties is trapped mag­netic flux. Flux trap­ping mech­a­nism de­pends on dif­fer­ent sur­face prepa­ra­tions and cool-down con­di­tions. We have de­signed, de­vel­oped and com­mis­sioned a com­bined mag­netic and tem­per­a­ture map­ping sys­tem using anisotropic mag­neto-re­sis­tance sen­sors and car­bon re­sis­tors, re­spec­tively, to study the flux trap mech­a­nism in 3 GHz sin­gle-cell nio­bium cav­i­ties. In this con­tri­bu­tion, we will de­scribe the ex­per­i­men­tal ap­pa­ra­tus and pre­sent pre­lim­i­nary test re­sults.

Parajuli, I. P.↗
DOE OSTI2022

MAGNETIC FIELD MAPPING OF 1.3 GHz SUPERCONDUCTING RADIO FREQUENCY NIOBIUM CAVITIES

Niobium is the material of choice to build superconducting radio frequency (SRF) cavities, which are fundamental building blocks of modern particle accelerators. These cavities require a cryogenic cool-down to ~2 - 4 K for optimum performance minimizing RF losses on the inner cavity surface. However, temperature-independent residual losses in SRF cavities cannot be prevented entirely. One of the significant contributor to residual losses is trapped magnetic flux. The flux trapping mechanism depends on different factors, such as surface preparations and cool-down conditions. We have developed a diagnostic magnetic field scanning system (MFSS) using Hall probes and anisotropic magneto-resistance sensors to study the spatial distribution of trapped flux in 1.3 GHz single-cell cavities. The first result from this newly commissioned system revealed that the trapped flux on the cavity surface might redistribute with increasing RF power. The MFSS was also able to capture significant magnetic field enhancement at specific cavity locations after a quench.

Parajuli, I. P.↗
DOE OSTI2022

Design of a 1.3 GHz RF-Dipole Crabbing Cavity for International Linear Collider

The International Liner Collider (ILC) requires crabbing systems to increase the luminosity of the colliding electron and positron bunches. There are several frequency options for the crabbing cavity. We have designed a 1.3 GHz compact 1-cell and 2-cell rf-dipole crabbing cavity to compensate for luminosity degradation due to large crossing angle. This paper presents the 1-cell and 2-cell cavities designed to meet the current specifications including the fundamental power coupler and higher order mode couplers.

De Silva, S.U.↗
DOE OSTI2020

A 100 kW 1.3 GHz Magnetron System with Amplitude and Phase Control

Calabazas Creek Research, Inc., Fermilab, and Communications & Power Industries, LLC, developed a 100 kW peak, 10 kW average, 1.3 GHz, magnetron-based, RF system for driving accelerators. Efficiency varied between 81% and 87%. Phase locking uses a novel approach that provides fast amplitude and phase control when coupled into a superconducting accelerator cavity [1]. The system was successfully tested at Fermilab and produced 100 kW in 1.5 ms pulses at a repetition rate of 2 pps. A locking bandwidth of 0.9 MHz was achieved with a drive signal of 269 W injected through a 4 port circulator. The phase locking signal was 25 dB below the magnetron output power. The spectrum of the phase locked magnetron was suitable for driving accelerator cavities. Phase modulation was demonstrated to 50 kHz (the limit of the available driver source). The average power was limited by available conditioning time. Scaling indicates 42 kW of average power should be achievable. Estimated cost is less than $1/Watt of delivered RF power, exclusive of power supplies or modulators. System design and performance measurements will be presented.

43 PARTICLE ACCELERATORS↗
DOE OSTI2023

MAGNETIC FIELD MAPPING OF A LARGE-GRAIN 1.3 GHz SINGLE-CELL CAVITY

A new magnetic field mapping system for 1.3 GHz single- cell cavities was developed in order to reveal the impact of ambient magnetic field and temperature gradients during cool-down on the flux trapping phenomenon. Measurements were done at 2 K for different cool-down conditions of a large-grain cavity before and after 120 °C bake. The fraction of applied magnetic field trapped in the cavity walls was ? 50% after slow cool-down and ? 20% after fast cool-down. The results showed a weak correlation between between trapped flux locations and hot-spots causing the high-field Q-slope. The results also showed an increase of the trapped flux at the quench location, after quenching, and a local redistribution of trapped flux with increasing RF field.

Ciovati, Gianluigi↗
DOE OSTI2020

Plasma Processing to Mitigate Field Emission in LCLS-II 1.3 GHz SRF Cavities

A collaboration between Fermilab, SLAC and ORNL is working to develop plasma processing for 1.3GHz TESLA shaped SRF cavities. Hydrocarbon (C x H y ) contaminations and adsorbates lower the cavity surface work function (Φ) increasing Field Emission (FE). Plasma processing removes C x H y allowing the cavity to operate at higher E acc .

43 PARTICLE ACCELERATORS↗
DOE OSTI2023

Commissioning of dedicated furnace for Nb3Sn coatings of 2.6GHz single cell cavities

We present the results of commissioning a dedicated fur- nace for Nb3Sn coatings of 2.6 GHz single cell cavities. Nb3Sn is a desired coating due to its high critical temper- ature and smaller surface resistance compared to bulk Nb. Usage of Nb3Sn coated cavities will greatly reduce operat- ing costs due to decreased dependance on cryo cooling. Tin is deposited by use of a tin chloride nucleation agent and tin vapor diffusion. Analysis of the resultant coating was performed using SEM/EDS to verify successful formation of Nb3Sn. Witness samples in line of sight of the source were used in order to understand the coating efficacy.

Kulyavtsev, P. A.↗
DOE OSTI2024

HOM Spectra Measurements in 1.3 GHz Cavities for LCLS-II

Fermilab recently completed production and testing of 1.3 GHz cryomodules for the LCLS-II project. Each cryomodule consists of eight TESLA-shaped super-conducting elliptical cavities equipped with two High Order Mode (HOM) coupler ports. Measurement of the HOM spectrum is part of the incoming quality control of cavities at room temperature and the final qualification cold test of cryomodules at the Cryomodule Test Facility (CMTF). In this paper we describe the procedure for measuring the HOM spectrum along with further data processing. Finally, we present accumulated statistics of individual HOM frequencies and quality factors related to various cavity vendors and dis-cuss the possible contribution of HOMs to heat loads and beam dynamics.

Lunin, A.↗
DOE OSTI2020

The Breakthrough Listen Search for Intelligent Life: A 3.95–8.00 GHz Search for Radio Technosignatures in the Restricted Earth Transit Zone

We report on a search for artificial narrowband signals of 20 stars within the restricted Earth Transit Zone (rETZ) as a part of the ten-year Breakthrough Listen (BL) search for extraterrestrial intelligence (ETI). The rETZ is the region of the sky from which an observer would see Earth transit the Sun with an impact parameter of less than 0.5. This region of the sky is geometrically unique, providing a potential way for an ETI to discover the solar system. The targets were nearby (7–143 pc) and the search covered an electromagnetic frequency range of 3.95–8.00 GHz. We used the Robert C. Byrd Green Bank Telescope to perform these observations with the standard BL data recorder. We searched these data for artificial narrowband (∼Hz) signals with Doppler drift rates of ±20 Hz s{sup −1}. We find no evidence for radio technosignatures from ETI in our observations. The observing campaign would have allowed for detections of emissions that were 10{sup −3} to 0.88 times as powerful as the signaling capability of the Arecibo radar transmitter. We conclude that at least 0.6% of the systems in the rETZ within 150 pc do not possess the type of transmitters searched in this survey. To our knowledge, this is the first targeted search for ETI of the rETZ. All data used in this paper are publicly available via the BL Public Data Archive (http://seti.berkeley.edu/bldr2).

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

A Search for Technosignatures Around 11,680 Stars with the Green Bank Telescope at 1.15–1.73 GHz

We conducted a search for narrowband radio signals over four observing sessions in 2020–2023 with the $L$-band receiver (1.15–1.73 GHz) of the 100 m diameter Green Bank Telescope. We pointed the telescope in the directions of 62 TESS Objects of Interest, capturing radio emissions from a total of ~11,680 stars and planetary systems in the ~9' beam of the telescope. All detections were either automatically rejected or visually inspected and confirmed to be of anthropogenic nature. We also quantified the end-to-end efficiency of radio SETI pipelines with a signal injection and recovery analysis. The UCLA SETI pipeline recovers 94.0% of the injected signals over the usable frequency range of the receiver and 98.7% of the injections when regions of dense radio frequency interference are excluded. In another pipeline that uses incoherent sums of 51 consecutive spectra, the recovery rate is ~15 times smaller at ~6%. The pipeline efficiency affects calculations of transmitter prevalence and SETI search volume. Accordingly, we developed an improved Drake figure of merit and a formalism to place upper limits on transmitter prevalence that take the pipeline efficiency and transmitter duty cycle into account. Based on our observations, we can state at the 95% confidence level that fewer than 6.6% of stars within 100 pc host a transmitter that is continuously transmitting a narrowband signal with an equivalent isotropic radiated power (EIRP) > 10 13 W. For stars within 20,000 ly, the fraction of stars with detectable transmitters (EIRP > 5 × 10 16 W) is at most 3 × 10 -4 . Finally, we showed that the UCLA SETI pipeline natively detects the signals detected with AI techniques by Ma et al.

79 ASTRONOMY AND ASTROPHYSICS↗