Collector Failures on 350 MHz, 1.2 MW CW Klystrons at the Low Energy Demonstration Accelerator (LEDA)

We are currently operating the front end of the accelerator production of tritium (APT) accelerator, a 7 MeV radio frequency quadrapole (RFQ) using three, 1.2 MW CW klystrons. These klystrons are required and designed to dissipate the full beam power in the collector. The klystrons have less than 1500 operational hours. One collector has failed and all collectors are damaged. This paper will discuss the damage and the difficulties in diagnosing the cause. The collector did not critically fail. Tube operation was still possible and the klystron operated up to 70% of full beam power with excellent vacuum. The indication that finally led us to the collector failure was variable emission. This information will be discussed. A hydrophonic system was implemented to diagnose collector heating. The collectors are designed to allow for mixed-phase cooling and with the hydrophonic test equipment we are able to observe: normal, single-phase cooling, mixed-phase cooling, and a hard boil. These data will be presented. The worst case beam profile from a collector heating standpoint is presented. The paper will also discuss the steps taken to halt the collector damage on the remaining 350 MHz klystrons and design changes that are being implemented to correct the problem.Comment: LINAC2000 conference paper THE1

Becoming phonemically aware: A study on the role of assistance in language learning

This was a Sociocultural study of second language learning involving Vygotsky\u27s Zone of Proximal Development (Vygotsky, 1978; & Newman and Holzman, 1993), phonemic awareness (Adams, 1990, Lieberman & Shankweiler, 1985), and dynamic assessment (Campione and Brown, 1987; Feuerstein, 1979; and Budoff, 1987). This inquiry was aimed at understanding how assistance functions in second language learning, uncovering student abilities in collaboration through an L2 dynamic assessment of phonemic awareness, and determining what information is available with an L2 dynamic assessment of phonemic awareness. This investigation illuminated teacher-to-student and student-to-student assistance in assessing/learning a second language during a Dynamic Assessment of L2 Phonemic Segmentation and subsequent intervention lessons. This study was guided by the following research questions: (1) How does assistance function in the language and literacy development of primary-aged ELLS? (2) What information does a dynamic assessment of L2 phonemic awareness provide that a static assessment does not?;This study involved the researcher and 5 first grade English Language Learner (ELL) students working in collaboration in L2 dynamic phonemic awareness assessment and intervention lessons. (Abstract shortened by UMI.)

Development of integrated thermionic circuits for high-temperature applications

Integrated thermionic circuits (ITC) capable of extended operation in ambient temperatures up to 500 C are studied. A set of practical design and performance equations is demonstrated. Experimental results are discussed in which both devices and simple circuits were successfully operated in 5000 C environments for extended periods. It is suggested that ITC's may become an important technology for high temperature instrumentation and control systems in geothermal and other high temperature environments

In situ RF/microwave remediation of soil benchtop experiment overview and results

The authors have developed an in-situ process that combines RF/microwave energy application with soil vapor extraction to help mobilize and efficiently remove soil contaminants. They have conducted a number of benchtop experiments involving RF/microwave energy deposition and vapor extraction on controlled contaminated soil samples with successful removal of the DNAPL contaminants. This paper will describe the experiments performed and present results

In situ RF/microwave remediation of soil experiment overview

Contaminant plumes are significant waste problems that require remediation in both the government and private sectors. The authors have developed an in situ process that uses RF/microwave stimulation to remove pollutants from contaminated soils. This process is more efficient than existing technologies, creates less secondary pollution, and is applicable to situations that are not amenable to treatment by existing technologies. Currently the most commonly used process is soil vapor extraction. However, even when it is successful, this technology is energy inefficient. The objective is to combine RF/microwave energy application with soil vapor extraction to help mobilize and efficiently remove the soil contaminants, specifically demonstrating the viability of RF/microwave induced, in situ, soil remediation of light and dense non-aqueous phase liquids (LNAPL, DNAPL) contaminants. The authors have conducted a number of benchtop experiments involving RF/microwave energy deposition and vapor extraction on controlled contaminated soil samples with successful removal of the contaminants. This paper will describe the experimental hardware utilized, the experiments performed, the chemical analysis performed pre- and post-energy application, and results. In the experiments, two different halogenated liquids were used to contaminate the soil: carbon tetrachloride and 1,1,1-trichloroethane

Social Determinants of Health and Parenting Self-Efficacy Among Mothers of Preterm Infants

Objective: To explore the relationships between social and environmental factors and parenting self-efficacy (PSE) among mothers of preterm infants hospitalized in neonatal intensive care units (NICUs) using a social determinants of health (SDoH) framework. Method: We analyzed data from a prospective cohort study that included 187 mother-infant dyads admitted to four NICUs in the Mountain West region between June 2017 and December 2019. We used multivariable linear regression models to assess the independent associations between maternal and infant characteristics and PSE. Results: Our final multiple linear regression model predicting the efficacy score including maternal race/ethnicity, age, insurance, employment status before giving birth, gestational age, depression, and having other children was significant (F(12,160) = 3.17, p = .0004, adjusted R¬2 = .131). Significant predictors of PSE were race/ethnicity (β= 3.3, p = .022), having another child/children (β= 4.2, p = .005), and depression (β= -4.2, p = .004). Conclusions: Findings suggest that social workers and medical practitioners should consider SDoH, such as insurance type, household income, and employment, along with traditional clinical indicators when assessing families’ infant care needs. Social workers, medical practitioners, and researchers should be mindful of how implicit bias may influence the allocation of care and parental supports

Design and test results of the Low Energy Demonstration Accelerator (LEDA) RF systems

The Low Energy Demonstration Accelerator (LEDA) being constructed at Los Alamos will serve as the prototype for the low energy section of the Accelerator Production of Tritium (APT) accelerator. The APT accelerator requires over 200 RF systems each with a continuous wave output power of 1 MW. The reliability and availability of these RF systems is critical to the successful operation of the APT plant and prototypes of these systems are being developed and demonstrated on LEDA. The RF system design for LEDA includes three, 1.2 MW, 350 MHz continuous wave (CW), RF systems driving a radio frequency quadrupole (RFQ) and one, 1.0 MW, CW, RF system driving a coupled-cavity drift tube linac (CCDTL). This paper presents the design and test results for these RF systems including the klystrons, cathode power supply, circulators, RF vacuum windows, accelerator field and resonance control system, and RF transmission components. The three RF systems driving the RFQ use the accelerating structure as a power combiner, and this places some unique requirements on the RF system. These requirements and corresponding operational implications will be discussed