Engineering Papers⌕ Search

Engineering topics

Huang, D

Publications and source records attributed to Huang, D.

9 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

SU-E-T-52: Beam Data Comparison for 20 Linear Accelerators in One Network

Purpose: To compare photon beam data for the 20 Varian linear accelerators (TrueBeam, iX, and EX models) in use at five centers in the same network with the intent to model with one set of beam data in Eclipsec. Methods: Varian linear accelerators, TrueBeam (3), 21 EX, iX, and Trilogy (14), and 6 EX (3), installed between 1999 and 2014 have their 6 MV and 15 MV x-ray beams reevaluated. Full commissioning, including output factors (St), percent depth doses (PDD), and off-axis profiles, was recently performed for a TrueBeam with a cc04 ion chamber in an IBA Blue phantom. Similarly, a subset of beam data for each of the other accelerators was measured recently as follows: for 3×3, 10×10, and 30×30 cm{sup 2} field sizes, flatness and penumbra (80–20%) were measured at dmax and 10 cm depths, PDD were measured at 10 and 20 cm depths, and St were measured at 5 cm depth. Measurement results for all machines were compared. Results: For 15 high-energy (6 and 15 MV) and 3 low-energy machines (6MV only): 1) PDD agreed within 1.4% at 10 and 20 cm depths; 2) penumbra agreed within 1.0 mm at dmax and 10 cm depths; 3) flatness was within 1.3% at dmax and 10 cm depths; and 4) with exception of the three low energy machines, output factors were within 1.1% and 0.5% for 3×3 and 30×30 cm{sup 2}, respectively. Measurement uncertainty, not quantified here, accounts for some of these differences. Conclusion: Measured beam data from 15 high-energy Varian linacs are consistent enough that they can be classified using one beam data set in Eclipse. Two additional high-energy machines are removed from this group until their data are further confirmed. Three low-energy machines will be in a separate class based upon differences in output factors (St)

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2012

Toward understanding of differences in current cloud retrievals of ARM ground-based measurements

Accurate observations of cloud microphysical properties are needed for evaluating and improving the representation of cloud processes in climate models and better estimate of the Earth radiative budget. However, large differences are found in current cloud products retrieved from ground-based remote sensing measurements using various retrieval algorithms. Understanding the differences is an important step to address uncertainties in the cloud retrievals. In this study, an in-depth analysis of nine existing ground-based cloud retrievals using ARM remote sensing measurements is carried out. We place emphasis on boundary layer overcast clouds and high level ice clouds, which are the focus of many current retrieval development efforts due to their radiative importance and relatively simple structure. Large systematic discrepancies in cloud microphysical properties are found in these two types of clouds among the nine cloud retrieval products, particularly for the cloud liquid and ice particle effective radius. Note that the differences among some retrieval products are even larger than the prescribed uncertainties reported by the retrieval algorithm developers. It is shown that most of these large differences have their roots in the retrieval theoretical bases, assumptions, as well as input and constraint parameters. This study suggests the need to further validate current retrieval theories and assumptions and even the development of new retrieval algorithms with more observations under different cloud regimes.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2010

Tomographic retrieval of cloud liquid water fields from a single scanning microwave radiometer aboard a moving platform – Part 1: Field trial results from the Wakasa Bay experiment

Tomographic methods offer great potential for retrieving three-dimensional spatial distributions of cloud liquid water from radiometric observations by passive microwave sensors. Fixed tomographic systems require multiple radiometers, while mobile systems can use just a single radiometer. Part 1 (this paper) examines the results from a limited cloud tomography trial with a single-radiometer airborne system carried out as part of the 2003 AMSR-E validation campaign over Wakasa Bay of the Sea of Japan. During this trial, the Polarimetric Scanning Radiometer (PSR) and Microwave Imaging Radiometer (MIR) aboard the NASA P-3 research aircraft provided a useful dataset for testing the cloud tomography method over a system of low-level clouds. We do tomographic retrievals with a constrained inversion algorithm using three configurations: PSR, MIR, and combined PSR and MIR data. The liquid water paths from the PSR retrieval are consistent with those from the MIR retrieval. The retrieved cloud field based on the combined data appears to be physically plausible and consistent with the cloud image obtained by a cloud radar. We find that some vertically-uniform clouds appear at high altitudes in the retrieved field where the radar shows clear sky. This is likely due to the sub-optimal data collection strategy. This sets the stage for Part 2 of this study that aims to define optimal data collection strategies using observation system simulation experiments.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2010

Tomographic retrieval of cloud liquid water fields from a single scanning microwave radiometer aboard a moving platform – Part 2: Observation system simulation experiments

Part 1 of this research concluded that many conditions of the 2003 Wakasa Bay experiment were not optimal for the purpose of tomographic retrieval. Part 2 (this paper) then aims to find possible improvements to the mobile cloud tomography method using observation system simulation experiments. We demonstrate that the incorporation of the L{sub 1} norm total variation regularization in the tomographic retrieval algorithm better reproduces discontinuous structures than the widely used L{sub 2} norm Tikhonov regularization. The simulation experiments reveal that a typical ground-based mobile setup substantially outperforms an airborne one because the ground-based setup usually moves slower and has greater contrast in microwave brightness between clouds and the background. It is shown that, as expected, the error in the cloud tomography retrievals increases monotonically with both the radiometer noise level and the uncertainty in the estimate of background brightness temperature. It is also revealed that a lower speed of platform motion or a faster scanning radiometer results in more scan cycles and more overlap between the swaths of successive scan cycles, both of which help to improve the retrieval accuracy. The last factor examined is aircraft height. It is found that the optimal aircraft height is 0.5 to 1.0 km above the cloud top. To summarize, this research demonstrates the feasibility of tomographically retrieving the spatial structure of cloud liquid water using current microwave radiometric technology and provides several general guidelines to improve future field-based studies of cloud tomography.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2010

The MuCool Test Area and RF Program

The MuCool RF Program focuses on the study of normal conducting RF structures operating in high magnetic field for applications in muon ionization cooling for Neutrino Factories and Muon Colliders. This paper will give an overview of the program, which will include a description of the test facility and its capabilities, the current test program, and the status of a cavity that can be rotated in the magnetic field which allows for a more detailed study of the maximum stable operating gradient vs. magnetic field strength and angle.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

The MuCool Test Area and RF Program

The MuCool RF Program focuses on the study of normal conducting RF structures operating in high magnetic field for applications in muon ionization cooling for Neutrino Factories and Muon Colliders. Here we give an overview of the program, which includes a description of the test facility and its capabilities, the current test program, and the status of a cavity that can be rotated in the magnetic field, which allows for a detailed study of the maximum stable operating gradient vs. magnetic field strength and angle.

43 PARTICLE ACCELERATORS↗
DOE OSTI2010

Rectangular Box Cavity Tests in Magnetic Field for Muon Cooling

Muon cooling requires high-gradient normal conducting cavities operating in multi-Tesla magnetic fields for muon beam focusing in an ionization cooling channel. Recent experience with an 805-MHz pillbox cavity at the Fermilab MuCool Test Area has shown a significant drop in accelerating field performance for the case of parallel electric and magnetic fields. It has been suggested that having the magnetic field perpendicular to the electric field should provide magnetic insulation and suppress breakdown. An 805-MHz Cu rectangular box cavity was built for testing with the fields perpendicular. It was mounted on an adjustable support to vary the angle between the rf electric and external magnetic field. We report on the design and initial operation of the rectangular box cavity.

43 PARTICLE ACCELERATORS↗