Dynamic PID loop control

The Horizontal Test Stand (HTS) SRF Cavity and Cryomodule 1 (CM1) of eight 9-cell, 1.3GHz SRF cavities are operating at Fermilab. For the cryogenic control system, how to hold liquid level constant in the cryostat by regulation of its Joule-Thompson JT-valve is very important after cryostat cool down to 2.0 K. The 72-cell cryostat liquid level response generally takes a long time delay after regulating its JT-valve; therefore, typical PID control loop should result in some cryostat parameter oscillations. This paper presents a type of PID parameter self-optimal and Time-Delay control method used to reduce cryogenic system parameters' oscillation.Comment: 7 pp. Cryogenic Engineering Conference and International Cryogenic Materials Conference CEC-ICMC 2011, 13-17 June 2011. Spokane, Washingto

Baseline Configuration of the Cryogenic System for the International Linear Collider

The paper discusses the main constraints and boundary conditions and describes the baseline configuration of the International Linear Collider (ILC) cryogenic system. The cryogenic layout, architecture and the cooling principle are presented. The paper addresses a plan for study and development required to demonstrate and improve the performance, to reduce cost and to attain the desired reliability

Diffusion of gases in air and its affect on oxygen deficiency hazard abatement

Density differences between air and released gases of cryogenic systems have been used to either require special oxygen deficiency hazard (ODH) control measures, or as a means of abatement. For example, it is not uncommon to assume that helium spills will quickly collect at the ceiling of a building or enclosure and will efficiently exit at the nearest vertical penetration or vent. Oxygen concentration reduction was found to be detectable during a localized helium spill throughout the entire 6.3 km Tevatron tunnel. This prompted us to perform diffusion tests in air with common gases used at Fermilab. The tests showed that gases, more readily than expected, diffused through an air column in the direction opposing buoyancy. Test results for helium and sulfur hexafluoride are presented. A system of tests were performed to better understand how easily released gases would fully mix with air and whether they remained fully mixed. The test results have been applied to a new system at Fermilab for ODH abatement

Cryogenics for the superconducting module test facility

A group of laboratories and universities, with Fermilab taking the lead, are constructing a superconducting cryomodule test facility (SMTF) in the Meson Detector Building (MDB) area at Fermilab. The facility will be used for testing and validating designs for both pulsed and CW systems. A multi phase approach is taken to construct the facility. For the initial phase of the project, cryogens for a single cavity cryomodule will be supplied from the existing Cryogenic Test Facility (CTF) that houses three Tevatron satellite refrigerators. The cooling capacity available for cryomodule testing at MDB results from the liquefaction capacity of the CTF cryogenic system. A cryogenic distribution system to supply cryogens from CTF to MDB is under construction. This paper describes plans, status and challenges of the initial phase of the SMTF cryogenic system

Fermilab SRF cryomodule operational experience

Fermi National Accelerator Laboratory is constructing an Advanced Accelerator Research and Development facility at New Muon Lab. The cryogenic infrastructure in support of the initial phase of the facility consists of two Tevatron style standalone refrigerators, cryogenic distribution system as well as an ambient temperature pumping system to achieve 2 K operations with supporting purification systems. During this phase of the project a single Type III plus 1.3 GHz cryomodule was installed, cooled and tested. Design constraints of the cryomodule required that the cryomodule individual circuits be cooled at predetermined rates. These constraints required special design solutions to achieve. This paper describes the initial cooldown and operational experience of a 1.3 GHz cryomodule using the New Muon Lab cryogenic system.Comment: 7 pp. Cryogenic Engineering Conference and International Cryogenic Materials Conference CEC-ICMC 2011 13-17 June 2011, Spokane, Washingto

Impact of environmental and genetic factors on the scale shape of zebrafish, Danio rerio (Hamilton 1822): A geometric morphometric study

Intraspecific morphological variability may reflect either genetic divergence among groups of individuals or response of individuals to environmental circumstances within the frame of phenotypic plasticity. Several studies were able to discriminate wild fish populations based on their scale shape. Here we examine whether the variations in the scale shape in fish populations could be related to genetic or environmental factors, or to both of them. In the first experiment, two inbred lines of zebrafish Danio rerio (Hamilton 1822) reared under identical environmental conditions were compared. Secondly, to find out what effect environmental factors might have, offsprings were divided into two groups and reared on different diets for 12 weeks. Potential recovery of scales from an environmental effect was also assessed. Experimental groups could successfully be distinguished according to the shape of scales in both experiments, and the results showed that both genetic and environmental factors may notably influence scale shape. It was concluded that scale shape analysis might be used as an explanatory tool to detect potential variability of environmental influences impacting genetically homogeneous groups of fish. However, due to its sensitivity to environmental heterogeneity, the applicability of this technique in identifying intraspecific stock membership of fish could be limited

Surge recovery techniques for the Tevatron cold compressors

The Fermilab Tevatron cryogenic system utilizes high-speed centrifugal cold compressors, made by Ishikawajima-Harima Heavy Industries Co. Ltd. (IHI), for high-energy operations [1]. The compressor is designed to pump 60 g/s of 3.6 K saturated helium vapor at a pressure ratio of 2.8, with an off-design range of 40 to 70 g/s and operating speeds between 40 and 95 krpm. Since initial commissioning in 1993, Tevatron transient conditions such as quench recovery have led to multiple-location machine trips as a result of the cold compressors entering the surge regime. Historically, compressors operating at lower inlet pressures and higher speeds have been especially susceptible to these machine trips and it was not uncommon to have multiple compressor trips during large multiple-house quenches. In order to cope with these events and limit accelerator down time, surge recovery techniques have been implemented in an attempt to prevent the compressors from tripping once the machine entered this surge regime. This paper discusses the different methods of surge recovery that have been employed. Data from tests performed at the Cryogenic Test Facility at Fermilab as well as actual Tevatron operational data were utilized. In order to aid in the determination of the surge region, a full mapping study was undertaken to characterize the entire pressure field of the cold compressor. These techniques were then implemented and tested at several locations in the Tevatron with some success

Serological and Genetic Diversity of Capsular Polysaccharides in Enterococcus faecalis

Enterococci possess capsular carbohydrate antigens that are targets of opsonic antibodies. These antigens may be used to develop alternative options for the treatment and prevention of enterococcal infections. The present study was done to analyze the diversity of capsular polysaccharides in Enterococcus faecalis. Four type-specific sera were used in an enzyme-linked immunosorbent assay format to detect polysaccharide antigen extracted from bacterial cell walls. A total of 55% of a collection of 29 E. faecalis strains could be grouped into one of four serogroups. Additional analysis of the strains by opsonophagocytic assays revealed agreement between the results of the two methods for 72% of the isolates. An additional four strains could be assigned to a serogroup on the basis of opsonic killing by sera with antibodies against the four prototypes strains, provisionally named CPS-A to CPS-D. The results of the two methods disagreed for one strain (4%). When the results of both methods were combined, 66% of the strains could be classified. One strain had to be assigned to two serogroups. The assignments to the four serogroups were confirmed by analysis of the genetic organization of the biosynthetic capsular polysaccharide (cps) locus. All strains grouped into serotypes CPS-A and CPS-B possessed only the cpsA and cpsB genes, while all strains grouped into serogroups CPS-C and CPS-D possessed an additional eight or nine genes. Our results suggest the existence of a limited number of E. faecalis capsule serotypes, and we provisionally propose four serotypes, named CPS-A to CPS-D, and the respective prototype strains for these families