A hall for assembly and cryogenic tests

International Nuclear Information System (INIS)

Beaunier, J.; Buhler, S.; Caruette, A.; Chevrollier, R.; Junquera, T.; Le Scornet, J.C.

1999-01-01

Cryodrome, an assembly hall and the testing ground for cryogenic equipment and R and D experiments for the superconducting cavities is going to be transformed for its future missions. The cryogenic utilities, especially the He low pressure pumping capacity, was rearranged and extended to a new area. Space was provided to install CRYHOLAB, a new horizontal cryostat for cavity testing. Automatic control and supervision of the utilities and the experimental area are rebuilt and updated. (authors)

Cryogenic infrastructure for Fermilab's ILC vertical cavity test facility

International Nuclear Information System (INIS)

Carcagno, R.; Ginsburg, C.; Huang, Y.; Norris, B.; Ozelis, J.; Peterson, T.; Poloubotko, V.; Rabehl, R.; Sylvester, C.; Wong, M.; Fermilab

2006-01-01

Fermilab is building a Vertical Cavity Test Facility (VCTF) to provide for R and D and pre-production testing of bare 9-cell, 1.3-GHz superconducting RF (SRF) cavities for the International Linear Collider (ILC) program. This facility is located in the existing Industrial Building 1 (IB1) where the Magnet Test Facility (MTF) also resides. Helium and nitrogen cryogenics are shared between the VCTF and MTF including the existing 1500-W at 4.5-K helium refrigerator with vacuum pumping for super-fluid operation (125-W capacity at 2-K). The VCTF is being constructed in multiple phases. The first phase is scheduled for completion in mid 2007, and includes modifications to the IB1 cryogenic infrastructure to allow helium cooling to be directed to either the VCTF or MTF as scheduling demands require. At this stage, the VCTF consists of one Vertical Test Stand (VTS) cryostat for the testing of one cavity in a 2-K helium bath. Planning is underway to provide a total of three Vertical Test Stands at VCTF, each capable of accommodating two cavities. Cryogenic infrastructure improvements necessary to support these additional VCTF test stands include a dedicated ambient temperature vacuum pump, a new helium purification skid, and the addition of helium gas storage. This paper describes the system design and initial cryogenic operation results for the first VCTF phase, and outlines future cryogenic infrastructure upgrade plans for expanding to three Vertical Test Stands

CRYOGENIC INFRASTRUCTURE FOR FERMILAB'S ILC VERTICAL CAVITY TEST FACILITY

International Nuclear Information System (INIS)

Carcagno, R.; Ginsburg, C.; Huang, Y.; Norris, B.; Ozelis, J.; Peterson, T.; Poloubotko, V.; Rabehl, R.; Sylvester, C.; Wong, M.

2008-01-01

Fermilab is building a Vertical Cavity Test Facility (VCTF) to provide for R and D and pre-production testing of bare 9-cell, 1.3-GHz superconducting RF (SRF) cavities for the International Linear Collider (ILC) program. This facility is located in the existing Industrial Building 1 (IB1) where the Magnet Test Facility (MTF) also resides. Helium and nitrogen cryogenics are shared between the VCTF and MTF including the existing 1500-W at 4.5-K helium refrigerator with vacuum pumping for super-fluid operation (125-W capacity at 2-K). The VCTF is being constructed in multiple phases. The first phase is scheduled for completion in mid 2007, and includes modifications to the IB1 cryogenic infrastructure to allow helium cooling to be directed to either the VCTF or MTF as scheduling demands require. At this stage, the VCTF consists of one Vertical Test Stand (VTS) cryostat for the testing of one cavity in a 2-K helium bath. Planning is underway to provide a total of three Vertical Test Stands at VCTF, each capable of accommodating two cavities. Cryogenic infrastructure improvements necessary to support these additional VCTF test stands include a dedicated ambient temperature vacuum pump, a new helium purification skid, and the addition of helium gas storage. This paper describes the system design and initial cryogenic operation results for the first VCTF phase, and outlines future cryogenic infrastructure upgrade plans for expanding to three Vertical Test Stands

Radiation Requirements and Testing of Cryogenic Thermometers for the Ilc

Science.gov (United States)

Barnett, T.; Filippov, Yu. P.; Filippova, E. Yu.; Mokhov, N. V.; Nakao, N.; Klebaner, A. L.; Korenev, S. A.; Theilacker, J. C.; Trenikhina, J.; Vaziri, K.

2008-03-01

Large quantity of cryogenic temperature sensors will be used for operation of the International Linear Collider (ILC). Most of them will be subject to high radiation doses during the accelerator lifetime. Understanding of particle energy spectra, accumulated radiation dose in thermometers and its impact on performance are vital in establishing technical specification of cryogenic thermometry for the ILC. Realistic MARS15 computer simulations were performed to understand the ILC radiation environment. Simulation results were used to establish radiation dose requirements for commercially available cryogenic thermometers. Two types of thermometers, Cernox® and TVO, were calibrated prior to irradiation using different technique. The sensors were subjected then to up to 200 kGy electron beam irradiation with kinetic energy of 5 MeV, a representative of the situation at the ILC operation. A post-irradiation behavior of the sensors was studied. The paper describes the MARS15 model, simulation results, cryogenic test set-up, irradiation tests, and cryogenic test results.

Radiation requirements and testing of cryogenic thermometers for the ILC

International Nuclear Information System (INIS)

Barnett, T.; Filippov, Yu.P.; Mokhov, N.V.; Nakao, N.; Klebaner, A.L.; Korenev, S.A.; Theilacker, J.C.; Trenikhina, J.; Vaziri, K.

2007-01-01

Large quantity of cryogenic temperature sensors will be used for operation of the International Linear Collider (ILC). Most of them will be subject to high radiation doses during the accelerator lifetime. Understanding of particle energy spectra, accumulated radiation dose in thermometers and its impact on performance are vital in establishing technical specification of cryogenic thermometry for the ILC. Realistic MARS15 computer simulations were performed to understand the ILC radiation environment. Simulation results were used to establish radiation dose requirements for commercially available cryogenic thermometers. Two types of thermometers, Cernox(reg s ign) and TVO, were calibrated prior to irradiation using different technique. The sensors were subjected then to up to 200 kGy electron beam irradiation with kinetic energy of 5 MeV, a representative of the situation at the ILC operation. A post-irradiation behavior of the sensors was studied. The paper describes the MARS15 model, simulation results, cryogenic test set-up, irradiation tests, and cryogenic test results

Electrical performance characteristics of the SSC Accelerator System String Test

International Nuclear Information System (INIS)

Robinson, W.; Burgett, W.; Dombeck, T.; Gannon, J.; Kraushaar, P.; McInturff, A.; Savord, T.; Tool, G.

1993-01-01

The string test facility was constructed to provide a development test bed for the arc regions of the Superconducting Super Collider (SSC). Significant effort has been devoted to the development and testing of superconducting magnets, spools, and accelerator control systems required for the SSC. The string test facility provides the necessary environment required to evaluate the operational performance of these components as they are configured as an accelerator lens in the collider. This discussion will review the results of high current testing of the string conducted to evaluate magnet element uniformity and compatibility, the splice resistance used to connect the magnets, and system response to various quench conditions. Performance results of the spools, energy bypass systems, energy dump, and the power supply system are also discussed

Electrical performance characteristics of the SSC Accelerator System String Test

International Nuclear Information System (INIS)

Robinson, W.; Burgett, W.; Dombeck, T.; Gannon, J.; Kraushaar, P.; McInturff, A.; Savord, T.; Tool, G.

1993-05-01

The string test facility was constructed to provide a development test bed for the arc regions of the Superconducting Super Collider (SSC). Significant effort has been devoted to the development and testing of superconducting magnets, spools, and accelerator control systems required for the SSC. The string test facility provides the necessary environment required to evaluate the operational performance of these components as they are configured as an accelerator lens in the collider. This discussion will review the results of high current testing of the string conducted to evaluate magnet element uniformity and compatibility, the splice resistance used to connect the magnets, and system response to various quench conditions. Performance results of the spools, energy bypass systems, energy dump, and the power supply system are also discussed

Test of a cryogenic helium pump

International Nuclear Information System (INIS)

Lue, J.W.; Miller, J.R.; Walstrom, P.L.; Herz, W.

1981-01-01

The design of a cryogenic helium pump for circulating liquid helium in a magnet and the design of a test loop for measuring the pump performance in terms of mass flow vs pump head at various pump speeds are described. A commercial cryogenic helium pump was tested successfully. Despite flaws in the demountable connections, the piston pump itself has performed satisfactorily. A helium pump of this type is suitable for the use of flowing supercritical helium through Internally Cooled Superconductor (ICS) magnets. It has pumped supercritical helium up to 7.5 atm with a pump head up to 2.8 atm. The maximum mass flow rate obtained was about 16 g/s. Performance of the pump was degraded at lower pumping speeds

The Cryogenic Test Bed experiments: Cryogenic heat pipe flight experiment CRYOHP (STS-53). Cryogenic two phase flight experiment CRYOTP (STS-62). Cryogenic flexible diode flight experiment CRYOFD

Science.gov (United States)

Thienel, Lee; Stouffer, Chuck

1995-09-01

This paper presents an overview of the Cryogenic Test Bed (CTB) experiments including experiment results, integration techniques used, and lessons learned during integration, test and flight phases of the Cryogenic Heat Pipe Flight Experiment (STS-53) and the Cryogenic Two Phase Flight Experiment (OAST-2, STS-62). We will also discuss the Cryogenic Flexible Diode Heat Pipe (CRYOFD) experiment which will fly in the 1996/97 time frame and the fourth flight of the CTB which will fly in the 1997/98 time frame. The two missions tested two oxygen axially grooved heat pipes, a nitrogen fibrous wick heat pipe and a 2-methylpentane phase change material thermal storage unit. Techniques were found for solving problems with vibration from the cryo-collers transmitted through the compressors and the cold heads, and mounting the heat pipe without introducing parasitic heat leaks. A thermally conductive interface material was selected that would meet the requirements and perform over the temperature range of 55 to 300 K. Problems are discussed with the bi-metallic thermostats used for heater circuit protection and the S-Glass suspension straps originally used to secure the BETSU PCM in the CRYOTP mission. Flight results will be compared to 1-g test results and differences will be discussed.

Testing string theory at LHC?

CERN Multimedia

CERN. Geneva

2002-01-01

A theory with such mathematical beauty cannot be wrong: this is one of the main arguments in favour of string theory, which unifies all known physical theories of fundamental interactions in a single coherent description of the universe. But no one has ever observed strings, not even indirectly, nor the space of extra dimensions where they live. However there are good reasons to believe that the 'hidden' dimensions of string theory may be much larger than what we thought in the past and that they may be within experimental reach in the near future - together with the strings themselves. In my talk, I will give an elementary introduction of string theory and describe the main experimental predictions.Organiser(s): Jasper Kirkby / EP DivisionNote: Tea & coffee will be served at 16.00 hrs.

Cryogenics for a vertical test stand facility for testing superconducting radio frequency cavities at RRCAT

International Nuclear Information System (INIS)

Gupta, Prabhat Kumar; Kumar, Manoj; Kush, P.K.

2015-01-01

Vertical Test Stand (VTS) Facility is located in a newly constructed building of Cryo-Engineering and Cryo-Module Development Division (CCDD). This test facility is one of the important facilities to develop SCRF technologies for superconducting accelerators like Indian Spallation Neutron Source. VTS has to be used for regular testing of the Superconducting Radio Frequency (SRF) Niobium cavities at nominal frequency of 1.3 GHz/ 650 MHz at 4 K / 2 K liquid helium (LHe) bath temperatures. Testing of these cavities at 2 K evaluates cavity processing methods, procedures and would also serve as a pre-qualification test for cavity to test it in horizontal cryostat, called horizontal test stand, with other cavity components such as tuner and helium vessel. Cryogenic technologies play a major role in these cavity testing facilities. Achieving and maintaining a stable temperature of 2 K in these test stands on regular and reliable basis is a challenging task and require broad range of cryogenic expertise, large scale system level understanding and many in-house technological and process developments. Furthermore this test stand will handle large amount of liquid helium. Therefore, an appropriately designed infrastructure is required to handle such large amount of helium gas generated during the operation of VTS .This paper describes the different cryogenic design aspects, initial cryogenic operation results and different cryogenic safety aspects. (author)

Cryogenics for the MuCool Test Area (MTA)

International Nuclear Information System (INIS)

Darve, Christine; Norris, Barry; Pei, Liujin

2006-01-01

MuCool Test Area (MTA) is a complex of buildings at Fermi National Accelerator Laboratory, which are dedicated to operate components of a cooling cell to be used for Muon Collider and Neutrino Factory R and D. The long-term goal of this facility is to test ionization cooling principles by operating a 25-liter liquid hydrogen (LH2) absorber embedded in a 5 Tesla superconducting solenoid magnet. The MTA solenoid magnet will be used with RF cavities exposed to a high intensity beam. Cryogens used at the MTA include LHe, LN2 and LH2. The latter dictates stringent system design for hazardous locations. The cryogenic plant is a modified Tevatron refrigerator based on the Claude cycle. The implementation of an in-house refrigerator system and two 300 kilowatt screw compressors is under development. The helium refrigeration capacity is 500 W at 14 K. In addition the MTA solenoid magnet will be batch-filled with LHe every 2 days using the same cryo-plant. This paper reviews cryogenic systems used to support the Muon Collider and Neutrino Factory R and D programs and emphasizes the feasibility of handling cryogenic equipment at MTA in a safe manner

A Cryogenic Test Set-Up for the Qualification of Pre-Series Test Cells for the LHC Cryogenic Distribution Line

CERN Document Server

Livran, J; Parente, C; Riddone, G; Rybkowski, D; Veillet, N

2000-01-01

Three pre-series Test Cells of the LHC Cryogenic Distribution Line (QRL) [1], manufactured by three European industrial companies, will be tested in the year 2000 to qualify the design chosen and verify the thermal and mechanical performances. A dedicated test stand (170 m x 13 m) has been built for extensive testing and performance assessment of the pre-series units in parallel. They will be fed with saturated liquid helium at 4.2 K supplied by a mobile helium dewar. In addition, LN2 cooled helium will be used for cool-down and thermal shielding. For each of the three pre-series units, a set of end boxes has been designed and manufactured at CERN. This paper presents the layout of the cryogenic system for the pre-series units, the calorimetric methods as well as the results of the thermal calculation of the end box test.

Cryogenic infrastructure for Fermilab's ILC vertical cavity test facility

Energy Technology Data Exchange (ETDEWEB)

Carcagno, R.; Ginsburg, C.; Huang, Y.; Norris, B.; Ozelis, J.; Peterson, T.; Poloubotko, V.; Rabehl, R.; Sylvester, C.; Wong, M.; /Fermilab

2006-06-01

Fermilab is building a Vertical Cavity Test Facility (VCTF) to provide for R&D and pre-production testing of bare 9-cell, 1.3-GHz superconducting RF (SRF) cavities for the International Linear Collider (ILC) program. This facility is located in the existing Industrial Building 1 (IB1) where the Magnet Test Facility (MTF) also resides. Helium and nitrogen cryogenics are shared between the VCTF and MTF including the existing 1500-W at 4.5-K helium refrigerator with vacuum pumping for super-fluid operation (125-W capacity at 2-K). The VCTF is being constructed in multiple phases. The first phase is scheduled for completion in mid 2007, and includes modifications to the IB1 cryogenic infrastructure to allow helium cooling to be directed to either the VCTF or MTF as scheduling demands require. At this stage, the VCTF consists of one Vertical Test Stand (VTS) cryostat for the testing of one cavity in a 2-K helium bath. Planning is underway to provide a total of three Vertical Test Stands at VCTF, each capable of accommodating two cavities. Cryogenic infrastructure improvements necessary to support these additional VCTF test stands include a dedicated ambient temperature vacuum pump, a new helium purification skid, and the addition of helium gas storage. This paper describes the system design and initial cryogenic operation results for the first VCTF phase, and outlines future cryogenic infrastructure upgrade plans for expanding to three Vertical Test Stands.

Cryogenic in situ microcompression testing of Sn

International Nuclear Information System (INIS)

Lupinacci, A.; Kacher, J.; Eilenberg, A.; Shapiro, A.A.; Hosemann, P.; Minor, A.M.

2014-01-01

Characterizing plasticity mechanisms below the ductile-to-brittle transition temperature is traditionally difficult to accomplish in a systematic fashion. Here, we use a new experimental setup to perform in situ cryogenic mechanical testing of pure Sn micropillars at room temperature and at −142 °C. Subsequent electron microscopy characterization of the micropillars shows a clear difference in the deformation mechanisms at room temperature and at cryogenic temperatures. At room temperature, the Sn micropillars deformed through dislocation plasticity, while at −142 °C they exhibited both higher strength and deformation twinning. Two different orientations were tested, a symmetric (1 0 0) orientation and a non-symmetric (4 5 ¯ 1) orientation. The deformation mechanisms were found to be the same for both orientations

SLAC physicists develop test for string theory

CERN Multimedia

Yajnik, Juhi

2006-01-01

"Under certain conditions, string theory solves many of the questions wracking the minds of physicists, but until recently it had one major flaw - it could not be tested. SLAC (Stanford Linear Accelerator Center) scientists have found a way to test this revolutionary theory, which posits that there are 10 or 11 dimensions in our universe" (1 page)

Test particle trajectories near cosmic strings

Indian Academy of Sciences (India)

Gauge strings have their energy concentrated in a very thin tube, the radius of which is of the order of the symmetry- breaking scale whereas the global strings are such that their energy extends to regions far beyond the central core. Strings have an important astrophysical consequence, namely, the double quasar problem ...

New Cryogenic Optical Test Capability at Marshall Space Flight Center's Space Optics Manufacturing Technology Center

Science.gov (United States)

Kegley, Jeff; Burdine, Robert V. (Technical Monitor)

2002-01-01

A new cryogenic optical testing capability exists at Marshall Space Flight Center's Space Optics Manufacturing Technology Center (SOMTC). SOMTC has been performing optical wavefront testing at cryogenic temperatures since 1999 in the X-ray Cryogenic Test Facility's (XRCF's) large vacuum chamber. Recently the cryogenic optical testing capability has been extended to a smaller vacuum chamber. This smaller horizontal cylindrical vacuum chamber has been outfitted with a helium-cooled liner that can be connected to the facility's helium refrigeration system bringing the existing kilowatt of refrigeration capacity to bear on a 1 meter diameter x 2 meter long test envelope. Cryogenic environments to less than 20 Kelvin are now possible in only a few hours. SOMTC's existing instruments (the Instantaneous Phase-shifting Interferometer (IPI) from ADE Phase-Shift Technologies and the PhaseCam from 4D Vision Technologies) view the optic under test through a 150 mm clear aperture BK-7 window. Since activation and chamber characterization tests in September 2001, the new chamber has been used to perform a cryogenic (less than 30 Kelvin) optical test of a 22.5 cm diameter x 127 cm radius of curvature Si02 mirror, a cryogenic survival (less than 30 Kelvin) test of an adhesive, and a cryogenic cycle (less than 20 Kelvin) test of a ULE mirror. A vibration survey has also been performed on the test chamber. Chamber specifications and performance data, vibration environment data, and limited test results will be presented.

Problem solving capabilities of Peach-fronted Conures (Eupsittula aurea) studied by the string-pulling test

DEFF Research Database (Denmark)

Ortiz, Sara Torres; Larsen, Ole Næsbye; Wahlberg, Magnus

Many studies have indicated advanced cognitive abilities in different species of parrots and ravens. Here we investigated basic cognitive skills of Peach-fronted Conures (Eupsittula aurea) using the string-pulling test. These small Middle-American parrots are often compared to dolphins due...... not be obtained by flying or reached from the ground. By varying different spatial configurations of strings and rewards, different cognitive skills could be investigated. Four conures (two females and two males) were tested. All four individuals solved three out of four tested string configurations (four...... straight strings, two slant strings, two contact-no contact strings) within 14 seconds on average, but all failed in a crossed two-string test. Subsequently we tested the birds with a vertical pulley that required the birds to pull the string down to get the food reward within reach from below...

Formation of a high intensity low energy positron string

Science.gov (United States)

Donets, E. D.; Donets, E. E.; Syresin, E. M.; Itahashi, T.; Dubinov, A. E.

2004-05-01

The possibility of a high intensity low energy positron beam production is discussed. The proposed Positron String Trap (PST) is based on the principles and technology of the Electron String Ion Source (ESIS) developed in JINR during the last decade. A linear version of ESIS has been used successfully for the production of intense highly charged ion beams of various elements. Now the Tubular Electron String Ion Source (TESIS) concept is under study and this opens really new promising possibilities in physics and technology. In this report, we discuss the application of the tubular-type trap for the storage of positrons cooled to the cryogenic temperatures of 0.05 meV. It is intended that the positron flux at the energy of 1-5 eV, produced by the external source, is injected into the Tubular Positron Trap which has a similar construction as the TESIS. Then the low energy positrons are captured in the PST Penning trap and are cooled down because of their synchrotron radiation in the strong (5-10 T) applied magnetic field. It is expected that the proposed PST should permit storing and cooling to cryogenic temperature of up to 5×109 positrons. The accumulated cooled positrons can be used further for various physics applications, for example, antihydrogen production.

Formation of a high intensity low energy positron string

International Nuclear Information System (INIS)

Donets, E.D.; Donets, E.E.; Syresin, E.M.; Itahashi, T.; Dubinov, A.E.

2004-01-01

The possibility of a high intensity low energy positron beam production is discussed. The proposed Positron String Trap (PST) is based on the principles and technology of the Electron String Ion Source (ESIS) developed in JINR during the last decade. A linear version of ESIS has been used successfully for the production of intense highly charged ion beams of various elements. Now the Tubular Electron String Ion Source (TESIS) concept is under study and this opens really new promising possibilities in physics and technology. In this report, we discuss the application of the tubular-type trap for the storage of positrons cooled to the cryogenic temperatures of 0.05 meV. It is intended that the positron flux at the energy of 1-5 eV, produced by the external source, is injected into the Tubular Positron Trap which has a similar construction as the TESIS. Then the low energy positrons are captured in the PST Penning trap and are cooled down because of their synchrotron radiation in the strong (5-10 T) applied magnetic field. It is expected that the proposed PST should permit storing and cooling to cryogenic temperature of up to 5x10 9 positrons. The accumulated cooled positrons can be used further for various physics applications, for example, antihydrogen production

Cryogenic System for the Cryomodule Test Stand at Fermilab

Energy Technology Data Exchange (ETDEWEB)

White, Michael J. [Fermilab; Hansen, Benjamin [Fermilab; Klebaner, Arkadiy [Fermilab

2017-10-09

This paper describes the cryogenic system for the Cryomodule Test Stand (CMTS) at the new Cryomodule Test Facility (CMTF) located at Fermilab. CMTS is designed for production testing of the 1.3 GHz and 3.9GHz cryomodules to be used in the Linac Coherent Light Source II (LCLSII), which is an upgrade to an existing accelerator at Stanford Linear Accelerator Laboratory (SLAC). This paper will focus on the cryogenic system that extends from the helium refrigeration plant to the CMTS cave. Topics covered will include component design, installation and commissioning progress, and operational plans. The paper will conclude with a description of the heat load measurement plan.

Investigation of Thermal and Vacuum Transients on the LHC Prototype Magnet String

CERN Document Server

Cruikshank, P; Riddone, G; Tavian, L

1996-01-01

The prototype magnet string, described in a companion paper, is a full-scale working model of a 50-m length of the future Large Hadron Collider (LHC), CERN's new accelerator project, which will use high-field superconducting magnets operating below 2 K in superfluid helium. As such, it provides an excellent test bed for practising standard operating modes of LHC insulation vacuum and cryogenics, as well as for experimentally assessing accidental behaviour and failure modes, and thus verifying design calculations. We present experimental investigation of insulation vacuum pumpdown, magnet forced-flow cooldown and warmup, and evolution of residual vacuum pressures and temperatures in natural warmup, as well as catastrophic loss of insulation vacuum. In all these transient modes, experimental results are compared with simulated behaviour, using a non-linear, one-dimensional thermal model of the magnet string.

A new cryogenic test facility for large superconducting devices at CERN

CERN Document Server

Perin, A; Serio, L; Stewart, L; Benda, V; Bremer, J; Pirotte, O

2015-01-01

To expand CERN testing capability to superconducting devices that cannot be installed in existing test facilities because of their size and/or mass, CERN is building a new cryogenic test facility for large and heavy devices. The first devices to be tested in the facility will be the S-FRS superconducting magnets for the FAIR project that is currently under construction at the GSI Research Center in Darmstadt, Germany. The facility will include a renovated cold box with 1.2 kW at 4.5 K equivalent power with its compression system, two independent 15 kW liquid nitrogen precooling and warm-up units, as well as a dedicated cryogenic distribution system providing cooling power to three independent test benches. The article presents the main input parameters and constraints used to define the cryogenic system and its infrastructure. The chosen layout and configuration of the facility is presented and the characteristics of the main components are described.

A cryogenic test stand for full length SSC magnets with superfluid capability

International Nuclear Information System (INIS)

Peterson, T.J.; Mazur, P.O.

1989-02-01

The Fermilab Magnet Test Facility performs testing of the full scale SSC magnets on test stands capable of simulating the cryogenic environment of the SSC main ring. One of these test stands, Stand 5, also has the ability to operate the magnet under test at temperatures from 1.8K to 4.5K with either supercritical helium or subcooled liquid, providing at least 25 Watts of refrigeration. At least 50 g/s flow is available from 2.3K to 4.5K, whereas superfluid operation occurs with zero flow. Cooldown time from 4.5K to 1.8K is 1.5 hours. A maximum current capability of 10,000 amps is provided, as is instrumentation to monitor and control the cryogenic conditions. This paper describes the cryogenic design of this test stand. 8 refs., 6 figs

Cryogenic actuator testing for the SAFARI ground calibration setup

Science.gov (United States)

de Jonge, C.; Eggens, M.; Nieuwenhuizen, A. C. T.; Detrain, A.; Smit, H.; Dieleman, P.

2012-09-01

For the on-ground calibration setup of the SAFARI instrument cryogenic mechanisms are being developed at SRON Netherlands Institute for Space Research, including a filter wheel, XYZ-scanner and a flipmirror mechanism. Due to the extremely low background radiation requirement of the SAFARI instrument, all of these mechanisms will have to perform their work at 4.5 Kelvin and low-dissipative cryogenic actuators are required to drive these mechanisms. In this paper, the performance of stepper motors, piezoelectric actuators and brushless DC-motors as cryogenic actuators are compared. We tested stepper motor mechanical performance and electrical dissipation at 4K. The actuator requirements, test setup and test results are presented. Furthermore, design considerations and early performance tests of the flipmirror mechanism are discussed. This flipmirror features a 102 x 72 mm aluminum mirror that can be rotated 45°. A Phytron stepper motor with reduction gearbox has been chosen to drive the flipmirror. Testing showed that this motor has a dissipation of 49mW at 4K with a torque of 60Nmm at 100rpm. Thermal modeling of the flipmirror mechanism predicts that with proper thermal strapping the peak temperature of the flipmirror after a single action will be within the background level requirements of the SAFARI instrument. Early tests confirm this result. For low-duty cycle operations commercial stepper motors appear suitable as actuators for test equipment in the SAFARI on ground calibration setup.

Why string theory?

CERN Document Server

Conlon, Joseph

2016-01-01

Is string theory a fraud or one of the great scientific advances? Why do so many physicists work on string theory if it cannot be tested? This book provides insight into why such a theory, with little direct experimental support, plays such a prominent role in theoretical physics. The book gives a modern and accurate account of string theory and science, explaining what string theory is, why it is regarded as so promising, and why it is hard to test.

Vent System Analysis for the Cryogenic Propellant Storage Transfer Ground Test Article

Science.gov (United States)

Hedayat, A

2013-01-01

To test and validate key capabilities and technologies required for future exploration elements such as large cryogenic propulsion stages and propellant depots, NASA is leading the efforts to develop and design the Cryogenic Propellant Storage and Transfer (CPST) Cryogenic Fluid Management (CFM) payload. The primary objectives of CPST payload are to demonstrate: 1) in-space storage of cryogenic propellants for long duration applications; and 2) in-space transfer of cryogenic propellants. The Ground Test Article (GTA) is a technology development version of the CPST payload. The GTA consists of flight-sized and flight-like storage and transfer tanks, liquid acquisition devices, transfer, and pressurization systems with all of the CPST functionality. The GTA is designed to perform integrated passive and active thermal storage and transfer performance testing with liquid hydrogen (LH2) in a vacuum environment. The GTA storage tank is designed to store liquid hydrogen and the transfer tank is designed to be 5% of the storage tank volume. The LH2 transfer subsystem is designed to transfer propellant from one tank to the other utilizing pressure or a pump. The LH2 vent subsystem is designed to prevent over-pressurization of the storage and transfer tanks. An in-house general-purpose computer program was utilized to model and simulate the vent subsystem operation. The modeling, analysis, and the results will be presented in the final paper.

Use of thermal sieve to allow optical testing of cryogenic optical systems.

Science.gov (United States)

Kim, Dae Wook; Cai, Wenrui; Burge, James H

2012-05-21

Full aperture testing of large cryogenic optical systems has been impractical due to the difficulty of operating a large collimator at cryogenic temperatures. The Thermal Sieve solves this problem by acting as a thermal barrier between an ambient temperature collimator and the cryogenic system under test. The Thermal Sieve uses a set of thermally controlled baffles with array of holes that are lined up to pass the light from the collimator without degrading the wavefront, while attenuating the thermal background by nearly 4 orders of magnitude. This paper provides the theory behind the Thermal Sieve system, evaluates the optimization for its optical and thermal performance, and presents the design and analysis for a specific system.

Field Testing of Cryogenic Carbon Capture

Energy Technology Data Exchange (ETDEWEB)

Sayre, Aaron [Sustainable Energy Solutions, LLC; Frankman, Dave [Sustainable Energy Solutions, LLC; Baxter, Andrew [Sustainable Energy Solutions, LLC; Stitt, Kyler [Sustainable Energy Solutions, LLC; Baxter, Larry [Sustainable Energy Solutions, LLC; Brigham Young Univ., Provo, UT (United States)

2017-07-17

Sustainable Energy Solutions has been developing Cryogenic Carbon Capture™ (CCC) since 2008. In that time two processes have been developed, the External Cooling Loop and Compressed Flue Gas Cryogenic Carbon Capture processes (CCC ECL™ and CCC CFG™ respectively). The CCC ECL™ process has been scaled up to a 1TPD CO2 system. In this process the flue gas is cooled by an external refrigerant loop. SES has tested CCC ECL™ on real flue gas slip streams from subbituminous coal, bituminous coal, biomass, natural gas, shredded tires, and municipal waste fuels at field sites that include utility power stations, heating plants, cement kilns, and pilot-scale research reactors. The CO2 concentrations from these tests ranged from 5 to 22% on a dry basis. CO2 capture ranged from 95-99+% during these tests. Several other condensable species were also captured including NO2, SO2 and PMxx at 95+%. NO was also captured at a modest rate. The CCC CFG™ process has been scaled up to a .25 ton per day system. This system has been tested on real flue gas streams including subbituminous coal, bituminous coal and natural gas at field sites that include utility power stations, heating plants, and pilot-scale research reactors. CO2 concentrations for these tests ranged from 5 to 15% on a dry basis. CO2 capture ranged from 95-99+% during these tests. Several other condensable species were also captured including NO2, SO2 and PMxx at 95+%. NO was also captured at 90+%. Hg capture was also verified and the resulting effluent from CCC CFG™ was below a 1ppt concentration. This paper will focus on discussion of the capabilities of CCC, the results of field testing and the future steps surrounding the development of this technology.

Cryogenic system for production testing and measurement of Fermilab energy saver superconducting magnets

International Nuclear Information System (INIS)

Cooper, W.E.; Barger, R.K.; Bianchi, A.J.; Cooper, W.E.; Johnson, F.B.; McGuire, K.J.; Pinyan, K.D.; Wilson, F.R.

1983-01-01

The cryogenic system of the Fermilab Magnet Test Facility has been used to provide cooling for the testing of approximately 1200 Energy Saver superconducting magnets. The system provides liquid helium, liquid nitrogen, gas purification, and vacuum support for six magnet test stands. It provides for simultaneous high current testing of two superconducting magnets and nonhigh current cold testing of two additional magnets. The cryogenic system has been in operation for about 32000 hours. The 1200 magnets have taken slightly more than three years to test

Cryogenic system for production testing and measurement of Fermilab energy saver superconducting magnets

International Nuclear Information System (INIS)

Cooper, W.E.; Bianchi, A.J.; Barger, R.K.; Johnson, F.B.; McGuire, K.J.; Pinyan, K.D.; Wilson, F.R.

1983-03-01

The cryogenic system of the Fermilab Magnet Test Facility has been used to provide cooling for the testing of approximately 1200 Energy Saver superconducting magnets. The system provides liquid helium, liquid nitrogen, gas purification, and vacuum support for six magnet test stands. It provides for simultaneous high current testing of two superconducting magnets and non-high current cold testing of two additional magnets. The cryogenic system has been in operation for about 32000 hours. The 1200 magnets have taken slightly more than three years to test

Cryogenic systems for the Mirror Fusion Test Facility

International Nuclear Information System (INIS)

Slack, D.S.; Chronis, W.C.; Nelson, R.L.

1986-01-01

This paper will include an in-depth discussion of the design, fabrication, and operation of the Mirror Fusion Test Facility (MFTF) cryogenic system located at Lawrence Livermore National Laboratory (LLNL). Each subsystem will be discussed to present a basic composite of the entire facility

Cryogenic system for the Energy Recovery Linac and vertical test facility at BNL

International Nuclear Information System (INIS)

Than, R.; Soria, V.; Lederle, D.; Orfin, P.; Porqueddu, R.; Talty, P.; Zhang, Y.; Tallerico, T.; Masi, L.

2011-01-01

A small cryogenic system and warm helium vacuum pumping system provides cooling to either the Energy Recovery Linac's (ERL) cryomodules that consist of a 5-cell cavity and an SRF gun or a large Vertical Test Dewar (VTD) at any given time. The cryogenic system consists of a model 1660S PSI piston plant, a 3800 liter storage dewar, subcooler, a wet expander, a 50 g/s main helium compressor, and a 170 m 3 storage tank. A system description and operating plan of the cryogenic plant and cryomodules is given. The cryogenic system for ERL and the Vertical Test Dewar has a plant that can produce the equivalent of 300W at 4.5K with the addition of a wet expander 350 W at 4.5K. Along with this system, a sub-atmospheric, warm compression system provides pumping to produce 2K at the ERL cryomodules or the Vertical Test Dewar. The cryogenic system for ERL and the Vertical Test Dewar makes use of existing equipment for putting a system together. It can supply either the ERL side or the Vertical Test Dewar side, but not both at the same time. Double valve isolation on the liquid helium supply line allows one side to be warmed to room temperature and worked on while the other side is being held at operating temperature. The cryogenic system maintain the end loads from 4.4K to 2K or colder depending on capacity. Liquid helium storage dewar capacity allows ERL or the VTD to operate above the plant's capacity when required and ERL cryomodules ballast reservoirs and VTD reservoir allows the end loads to operate on full vacuum pump capacity when required.

Cryogenic test facility instrumentation with fiber optic and fiber optic sensors for testing superconducting accelerator magnets

Science.gov (United States)

Chiuchiolo, A.; Bajas, H.; Bajko, M.; Castaldo, B.; Consales, M.; Cusano, A.; Giordano, M.; Giloux, C.; Perez, J. C.; Sansone, L.; Viret, P.

2017-12-01

The magnets for the next steps in accelerator physics, such as the High Luminosity upgrade of the LHC (HL- LHC) and the Future Circular Collider (FCC), require the development of new technologies for manufacturing and monitoring. To meet the HL-LHC new requirements, a large upgrade of the CERN SM18 cryogenic test facilities is ongoing with the implementation of new cryostats and cryogenic instrumentation. The paper deals with the advances in the development and the calibration of fiber optic sensors in the range 300 - 4 K using a dedicated closed-cycle refrigerator system composed of a pulse tube and a cryogen-free cryostat. The calibrated fiber optic sensors (FOS) have been installed in three vertical cryostats used for testing superconducting magnets down to 1.9 K or 4.2 K and in the variable temperature test bench (100 - 4.2 K). Some examples of FOS measurements of cryostat temperature evolution are presented as well as measurements of strain performed on a subscale of High Temperature Superconducting magnet during its powering tests.

Quantum string test of nonconformal holography

Energy Technology Data Exchange (ETDEWEB)

Chen-Lin, Xinyi; Medina-Rincon, Daniel; Zarembo, Konstantin [Nordita, Stockholm University and KTH Royal Institute of Technology,Roslagstullsbacken 23, SE-106 91 Stockholm (Sweden); Department of Physics and Astronomy, Uppsala University,SE-751 08 Uppsala (Sweden)

2017-04-18

We compute Lüscher corrections to the effective string tension in the Pilch-Warner background, holographically dual to N=2{sup ∗} supersymmetric Yang-Mills theory. The same quantity can be calculated directly from field theory by solving the localization matrix model at large-N. We find complete agreement between the field-theory predictions and explicit string-theory calculation at strong coupling.

Development and flight test of metal-lined CFRP cryogenic tank for reusable rocket

Science.gov (United States)

Higuchi, Ken; Takeuchi, Shinsuke; Sato, Eiichi; Naruo, Yoshihiro; Inatani, Yoshifumi; Namiki, Fumiharu; Tanaka, Kohtaro; Watabe, Yoko

2005-07-01

A cryogenic tank made of carbon fiber reinforced plastic (CFRP) shell with aluminum thin liner has been designed as a liquid hydrogen (LH2) tank for an ISAS reusable launch vehicle, and the function of it has been proven by repeated flights onboard the test vehicle called reusable vehicle testing (RVT) in October 2003. The liquid hydrogen tank has to be a pressure vessel, because the fuel of the engine of the test vehicle is supplied by fuel pressure. The pressure vessel of a combination of the outer shell of CFRP for strength element at a cryogenic temperature and the inner liner of aluminum for gas barrier has shown excellent weight merit for this purpose. Interfaces such as tank outline shape, bulk capacity, maximum expected operating pressure (MEOP), thermal insulation, pipe arrangement, and measurement of data are also designed to be ready onboard. This research has many aims, not only development of reusable cryogenic composite tank but also the demonstration of repeated operation including thermal cycle and stress cycle, familiarization with test techniques of operation of cryogenic composite tanks, and the accumulation of data for future design of tanks, vehicle structures, safety evaluation, and total operation systems.

Results of KEPCO HTS cable system tests and design of hybrid cryogenic system

International Nuclear Information System (INIS)

Lim, J.H.; Sohn, S.H.; Yang, H.S.; Hwang, S.D.; Kim, D.L.; Ryoo, H.S.; Choi, H.O.

2010-01-01

In order to investigate the compatibility as a power utility facility, Korea Electric Power Corporation (KEPCO) had installed a 22.9 kV, 1250 A, 100 m long high temperature superconducting (HTS) power cable system. Using the HTS cable, various tests have been performed to investigate electrical and thermo-mechanical properties. Since 2005, a series of thermal cycle tests between liquid nitrogen (LN 2 ) and ambient temperatures have been conducted using a vacuum-pump driven open-loop cryogenic system with a capacity of 3 kW. In the tests, although the open-loop cryogenic system was reliable to operate the HTS cable system, it was not effective in economic view point because LN 2 consumption was larger than expected. In order to secure against unexpected emergencies and solve the problem of LN 2 consumption, a hybrid cryogenic system was designed and installed. A stirling cryocooler was employed and combined with the open-loop cryogenic system. Considering the average heat load at rated condition, the cooling capacity of the cryocooler was determined to 4 kW at 77 K. In this paper, results of performance tests and the design of the hybrid cooling system are presented.

Cryogenic distribution system for ITER proto-type cryoline test

International Nuclear Information System (INIS)

Bhattacharya, R.; Shah, N.; Badgujar, S.; Sarkar, B.

2012-01-01

Design validation for ITER cryoline will be carried out by proto-type test on cryoline. The major objectives of the test will be to ensure the mechanical integrity, reliability, thermal stress and heat load as well as checking of assembly and fabrication procedures. The cryogenics system has to satisfy the functional operating scenario of the cryoline. Cryoplant, distribution box (DB) including liquid helium (LHe) tank constitute the cryogenic system for the test. Conceptual system architecture is proposed with a commercially available refrigerator/liquefier and custom designed DB housing cold compressor, cold circulator as well as phase separator with sub-merged heat exchanger. System level optimization, mainly with DB and LHe tank with options, has been studied to minimize the cold power required for the system. Aspen HYSYS is used for the purpose of process simulation. The paper describes the system architecture and the optimized design as well as process simulation with associated results. (author)

ITER Task T332a (1995): Low-inventory cryogenic distillation tests

International Nuclear Information System (INIS)

Woodall, K.; Robins, J.; Bellamy, D.

1996-01-01

Previous work at Ontario Hydro Technologies (OHT) had shown that small hydrogen cryogenic columns could be stably controlled and designed to much lower inventories than had been previously thought possible. Among the results were measurements of height equivalent to a theoretical plate (HETP) versus holdup for Helipak A and B packings in columns up to 20 mm diameter. ITER cryogenic distillation column designs suggest that the final high-tritium column could be 30-70 mm diameter. The objective of this ITER task was to test scale-up of OHT low inventory columns to ITER dimensions. In 1994 OHT built a suitable test facility. In 1995, two low-inventory packings were tested. (author) 4 refs., 6 figs

Mechanical Tensile Testing of Titanium 15-3-3-3 and Kevlar 49 at Cryogenic Temperatures

Science.gov (United States)

James, Bryan L.; Martinez, Raul M.; Shirron, Peter; Tuttle, Jim; Galassi, Nicholas M.; Mcguinness, Daniel S.; Puckett, David; Francis, John J.; Flom, Yury

2011-01-01

Titanium 15-3-3-3 and Kevlar 49 are highly desired materials for structural components in cryogenic applications due to their low thennal conductivity at low temperatures. Previous tests have indicated that titanium 15-3-3-3 becomes increasingly brittle as the temperature decreases. Furthermore, little is known regarding the mechanical properties of Kevlar 49 at low temperatures, most specifically its Young's modulus. This testing investigates the mechanical properties of both materials at cryogenic temperatures through cryogenic mechanical tensile testing to failure. The elongation, ultimate tensile strength, yield strength, and break strength of both materials are provided and analyzed here.

Automatic Management Systems for the Operation of the Cryogenic Test Facilities for LHC Series Superconducting Magnets

CERN Document Server

Tovar-Gonzalez, A; Herblin, L; Lamboy, J P; Vullierme, B

2006-01-01

Prior to their final preparation before installation in the tunnel, the ~1800 series superconducting magnets of the LHC machine shall be entirely tested at reception on modular test facilities. The operation 24 hours per day of the cryogenic test facilities is conducted in turn by 3-operator teams, assisted in real time by the use of the Test Bench Priorities Handling System, a process control application enforcing the optimum use of cryogenic utilities and of the "Tasks Tracking System", a web-based e-traveller application handling 12 parallel 38-task test sequences. This paper describes how such computer-based management systems can be used to optimize operation of concurrent test benches within technical boundary conditions given by the cryogenic capacity, and how they can be used to study the efficiency of the automatic steering of all individual cryogenic sub-systems. Finally, this paper presents the overall performance of the cryomagnet test station for the first complete year of operation at high produ...

The Preparation of the Cryomagnets and the Assembly of the LHC Test String 2

CERN Document Server

Andujar, O; Calzas-Rodriguez, C; Cruikshank, P; Desebe, O; Dobers, T; Jacquemod, A; Kos, N; Lepeule, P; Maan, W; Missiaen, D; Parma, Vittorio; Riddone, G; Rodríguez-Mateos, F; Rohmig, P; Saban, R I; Schneider, G; Serio, L; Skoczen, Blazej; Tock, J P; Veness, R J M; Vuitton, C

2001-01-01

The numerous complex activities required to prepare the cryomagnets for the installation in String 2 are described. These include the configuration of the mechanical interfaces, thee conditioning of the beam tubes, the installation of beam screens and the instrumentation as well as the final checks. The preparation of the cryomagnets for String 2 has been a dress rehearsal for the preparation that the cryomagnets will undergo before their installation in the tunnel. After a description of the interconnection procedures of the components for String 2, the tests carried-out to release the String for operation are described. A brief account of the lessons learnt is also given.

Automatic control of NASA Langley's 0.3-meter cryogenic test facility

Science.gov (United States)

Thibodeaux, J. J.; Balakrishna, S.

1980-01-01

Experience during the past 6 years of operation of the 0.3-meter transonic cryogenic tunnel at the NASA Langley Research Center has shown that there are problems associated with efficient operation and control of cryogenic tunnels using manual control schemes. This is due to the high degree of process crosscoupling between the independent control variables (temperature, pressure, and fan drive speed) and the desired test condition (Mach number and Reynolds number). One problem has been the inability to maintain long-term accurate control of the test parameters. Additionally, the time required to change from one test condition to another has proven to be excessively long and much less efficient than desirable in terms of liquid nitrogen and electrical power usage. For these reasons, studies have been undertaken to: (1) develop and validate a mathematical model of the 0.3-meter cryogenic tunnel process, (2) utilize this model in a hybrid computer simulation to design temperature and pressure feedback control laws, and (3) evaluate the adequacy of these control schemes by analysis of closed-loop experimental data. This paper will present the results of these studies.

New Technique for Cryogenically Cooling Small Test Articles

Science.gov (United States)

Rodriquez, Karen M.; Henderson, Donald J.

2011-01-01

Convective heat removal techniques to rapidly cool small test articles to Earth-Moon L2 temperatures of 77 K were accomplished through the use of liquid nitrogen (LN2). By maintaining a selected pressure range on the saturation curve, test articles were cooled below the LN2 boiling point at ambient pressure in less than 30 min. Difficulties in achieving test pressures while maintaining the temperature tolerance necessitated a modification to the original system to include a closed loop conductive cold plate and cryogenic shroud

Autonomous Cryogenic Load Operations: KSC Autonomous Test Engineer

Science.gov (United States)

Shrading, Nicholas J.

2012-01-01

The KSC Autonomous Test Engineer (KATE) program has a long history at KSC. Now a part of the Autonomous Cryogenic Load Operations (ACLO) mission, this software system has been sporadically developed over the past 20+ years. Originally designed to provide health and status monitoring for a simple water-based fluid system, it was proven to be a capable autonomous test engineer for determining sources of failure in. the system, As part.of a new goal to provide this same anomaly-detection capability for a complicated cryogenic fluid system, software engineers, physicists, interns and KATE experts are working to upgrade the software capabilities and graphical user interface. Much progress was made during this effort to improve KATE. A display ofthe entire cryogenic system's graph, with nodes for components and edges for their connections, was added to the KATE software. A searching functionality was added to the new graph display, so that users could easily center their screen on specific components. The GUI was also modified so that it displayed information relevant to the new project goals. In addition, work began on adding new pneumatic and electronic subsystems into the KATE knowledgebase, so that it could provide health and status monitoring for those systems. Finally, many fixes for bugs, memory leaks, and memory errors were implemented and the system was moved into a state in which it could be presented to stakeholders. Overall, the KATE system was improved and necessary additional features were added so that a presentation of the program and its functionality in the next few months would be a success.

ITER task T48 (1994); low-inventory cryogenic distillation tests

Energy Technology Data Exchange (ETDEWEB)

Woodall, K; Robins, J; Bellamy, D [Ontario Hydro, Toronto, ON (Canada). Research Div.; Sood, S; Fong, C [Ontario Hydro, Toronto, ON (Canada)

1995-01-01

Previous work at Ontario Hydro Technologies (OHT) had shown that small cryogenic columns could be stably controlled and designed to much lower inventories than had been previously thought possible. Among the results were measurements of Height-of-Equivalent-Theoretical-Plate (HETP) versus holdup for Heli-Pak A and B in columns up to 20 mm diameter. ITER cryogenic distillation column designs suggest that the final high-tritium columns could be 30-70 mm diameter. The objective of this ITER task was to design and construct a column section for demonstration of scale-up of low inventory cryogenic distillation. The experiments were to be carried out in an upgraded Cryogenics Distillation Laboratory at OHT, in the facility used for previous low-inventory column tests. The ITER scaled-up test system as the following characteristics: 55 W condenser capacity; 30 mm diameter column loaded with Helipak B; 1500 mm packed height. The first task was to design and build the scaled-up test facility. In order to reduce costs, it was necessary to use existing 30-35 W helium refrigerators. Therefore, to provide 60-W duty to the scaled-up column, the two refrigerators had to be well coupled thermally, but not mechanically, since the refrigerator cold heads have very thin shells. The solution was to attach the column firmly to one cold head and indirectly to an adjacent cold head through flexible copper braid. Several iterations were required to obtain the desired good heat transfer with flexible mechanical connection. This facility is now operational and ready to begin measurements on the 30 mm column. Also during 1994, the Princeton Tritium Processing System (TPS) was installed and commissioned. The results from this experience are relevant to the ITER distillation system. 2 refs., 10 figs.

ITER task T48 (1994); low-inventory cryogenic distillation tests

International Nuclear Information System (INIS)

Woodall, K.; Robins, J.; Bellamy, D.

1995-01-01

Previous work at Ontario Hydro Technologies (OHT) had shown that small cryogenic columns could be stably controlled and designed to much lower inventories than had been previously thought possible. Among the results were measurements of Height-of-Equivalent-Theoretical-Plate (HETP) versus holdup for Heli-Pak A and B in columns up to 20 mm diameter. ITER cryogenic distillation column designs suggest that the final high-tritium columns could be 30-70 mm diameter. The objective of this ITER task was to design and construct a column section for demonstration of scale-up of low inventory cryogenic distillation. The experiments were to be carried out in an upgraded Cryogenics Distillation Laboratory at OHT, in the facility used for previous low-inventory column tests. The ITER scaled-up test system as the following characteristics: 55 W condenser capacity; 30 mm diameter column loaded with Helipak B; 1500 mm packed height. The first task was to design and build the scaled-up test facility. In order to reduce costs, it was necessary to use existing 30-35 W helium refrigerators. Therefore, to provide 60-W duty to the scaled-up column, the two refrigerators had to be well coupled thermally, but not mechanically, since the refrigerator cold heads have very thin shells. The solution was to attach the column firmly to one cold head and indirectly to an adjacent cold head through flexible copper braid. Several iterations were required to obtain the desired good heat transfer with flexible mechanical connection. This facility is now operational and ready to begin measurements on the 30 mm column. Also during 1994, the Princeton Tritium Processing System (TPS) was installed and commissioned. The results from this experience are relevant to the ITER distillation system. 2 refs., 10 figs

Instrumentation, Field Network And Process Automation for the LHC Cryogenic Line Tests

CERN Document Server

Bager, T; Bertrand, G; Casas-Cubillos, J; Gomes, P; Parente, C; Riddone, G; Suraci, A

2000-01-01

This paper describes the cryogenic control system and associated instrumentation of the test facility for 3 pre-series units of the LHC Cryogenic Distribution Line. For each unit, the process automation is based on a Programmable Logic Con-troller implementing more than 30 closed control loops and handling alarms, in-terlocks and overall process management. More than 160 sensors and actuators are distributed over 150 m on a Profibus DP/PA network. Parameterization, cali-bration and diagnosis are remotely available through the bus. Considering the diversity, amount and geographical distribution of the instru-mentation involved, this is a representative approach to the cryogenic control system for CERN's next accelerator.

Observational tests of open strings in braneworld scenarios

International Nuclear Information System (INIS)

Freese, Katherine; Lewis, Matthew J.; Schaar, Jan Pieter van der

2003-01-01

We consider some consequences of describing the gauge and matter degrees of freedom in our universe by open strings, as suggested by the braneworld scenario. We focus on changes in causal structure described by the open string metric and investigate their observational implications. The causal structure is described not by the usual metric g μν , but instead by the open string metric, that incorporates the electromagnetic background and the NS-NS two-form, G μν = g μν -(2 π α') 2 (F 2 ) μν. The speed of light on the brane is now slower when propagating along directions transverse to electromagnetic fields or NS-NS two-forms, so that Lorentz invariance is explicitly broken. We describe experiments designed to detect the predicted variations in the open string causal structure on the brane: interferometric laboratory based experiments, experiments exploiting astrophysical electromagnetic fields, and experiments that rely on modification to special relativity. We show that current technology cannot probe beyond open string lengths of 10 -13 cm, corresponding to MeV string scales. We also point out that in a braneworld scenario, constraints on large scale electromagnetic fields together with a modest phenomenological bound on the NS-NS two-form naturally lead to a bound on the scale of canonical noncommutativity that is two orders of magnitude below the string length. We show that theoretical constraints on the NS-NS two-form bound the scale of noncommutativity to be well below the Planck length, (vertical barθvertical bar max )(1/2) -35 cm x (TeV/stringscale) 2 . (author)

Full Cryogenic Test of 600 A HTS Hybrid Current Leads for the LHC

CERN Document Server

Al-Mosawi, MK; Beduz, C; Ballarino, A; Yang, Y

2007-01-01

For full cryogenic test of CERN 600 A High Temperature Superconducting (HTS) current leads prior to integration into the Large Hadron Collider (LHC), a ded. facility has been designed, constructed and operated at the University of Southampton. The facility consists of purpose-built test cryostats, 20 K helium gas supply, helium gas flow and temperature control systems and quench protection system. Over 400 such leads have already been successfully tested and qualified for installation at CERN. This paper describes various design and operation aspects of the test facility and presents the detailed cryogenic test results of the CERN 600 A current leads, including steady state 20 K flow rates.

Linear Model-Based Predictive Control of the LHC 1.8 K Cryogenic Loop

CERN Document Server

Blanco-Viñuela, E; De Prada-Moraga, C

1999-01-01

The LHC accelerator will employ 1800 superconducting magnets (for guidance and focusing of the particle beams) in a pressurized superfluid helium bath at 1.9 K. This temperature is a severely constrained control parameter in order to avoid the transition from the superconducting to the normal state. Cryogenic processes are difficult to regulate due to their highly non-linear physical parameters (heat capacity, thermal conductance, etc.) and undesirable peculiarities like non self-regulating process, inverse response and variable dead time. To reduce the requirements on either temperature sensor or cryogenic system performance, various control strategies have been investigated on a reduced-scale LHC prototype built at CERN (String Test). Model Based Predictive Control (MBPC) is a regulation algorithm based on the explicit use of a process model to forecast the plant output over a certain prediction horizon. This predicted controlled variable is used in an on-line optimization procedure that minimizes an approp...

Thermal stratification in LH2 tank of cryogenic propulsion stage tested in ISRO facility

Science.gov (United States)

Xavier, M.; Raj, R. Edwin; Narayanan, V.

2017-02-01

Liquid oxygen and hydrogen are used as oxidizer and fuel respectively in cryogenic propulsion system. These liquids are stored in foam insulated tanks of cryogenic propulsion system and are pressurized using warm pressurant gas supplied for tank pressure maintenance during cryogenic engine operation. Heat leak to cryogenic propellant tank causes buoyancy driven liquid stratification resulting in formation of warm liquid stratum at liquid free surface. This warm stratum is further heated by the admission of warm pressurant gas for tank pressurization during engine operation. Since stratified layer temperature has direct bearing on the cavitation free operation of turbo pumps integrated in cryogenic engine, it is necessary to model the thermal stratification for predicting stratified layer temperature and mass of stratified liquid in tank at the end of engine operation. These inputs are required for estimating the minimum pressure to be maintained by tank pressurization system. This paper describes configuration of cryogenic stage for ground qualification test, stage hot test sequence, a thermal model and its results for a foam insulated LH2 tank subjected to heat leak and pressurization with hydrogen gas at 200 K during liquid outflow at 38 lps for engine operation. The above model considers buoyancy flow in free convection boundary layer caused by heat flux from tank wall and energy transfer from warm pressurant gas etc. to predict temperature of liquid stratum and mass of stratified liquid in tank at the end of engine operation in stage qualification tests carried out in ISRO facility.

A cryogenic tensile testing apparatus for micro-samples cooled by miniature pulse tube cryocooler

International Nuclear Information System (INIS)

Chen, L B; Liu, S X; Gu, K X; Zhou, Y; Wang, J J

2015-01-01

This paper introduces a cryogenic tensile testing apparatus for micro-samples cooled by a miniature pulse tube cryocooler. At present, tensile tests are widely applied to measure the mechanical properties of materials; most of the cryogenic tensile testing apparatus are designed for samples with standard sizes, while for non-standard size samples, especially for microsamples, the tensile testing cannot be conducted. The general approach to cool down the specimens for tensile testing is by using of liquid nitrogen or liquid helium, which is not convenient: it is difficult to keep the temperature of the specimens at an arbitrary set point precisely, besides, in some occasions, liquid nitrogen, especially liquid helium, is not easily available. To overcome these limitations, a cryogenic tensile testing apparatus cooled by a high frequency pulse tube cryocooler has been designed, built and tested. The operating temperatures of the developed tensile testing apparatus cover from 20 K to room temperature with a controlling precision of ±10 mK. The apparatus configurations, the methods of operation and some cooling performance will be described in this paper. (paper)

New Scanning Electron Microscope Used for Cryogenic Tensile Testing

CERN Multimedia

Maximilien Brice

2013-01-01

At CERN engineering department's installation for cryogenic tensile testing, the new scanning electron microscope (SEM) allows for detailed optical observations to be carried out. Using the SEM, surface coatings and tensile properties of materials can investigated in order to better understand how they behave under different conditions.

Cryogenic Design of the New High Field Magnet Test Facility at CERN

Science.gov (United States)

Benda, V.; Pirotte, O.; De Rijk, G.; Bajko, M.; Craen, A. Vande; Perret, Ph.; Hanzelka, P.

In the framework of the R&D program related to the Large Hadron Collider (LHC) upgrades, a new High Field Magnet (HFM) vertical test bench is required. This facility located in the SM18 cryogenic test hall shall allow testing of up to 15 tons superconducting magnets with energy up to 10 MJ in a temperature range between 1.9 K and 4.5 K. The article describes the cryogenic architecture to be inserted in the general infrastructure of SM18 including the process and instrumentation diagram, the different operating phases including strategy for magnet cool down and warm up at controlled speed and quench management as well as the design of the main components.

Testing string dynamics in lepton nucleus reactions

International Nuclear Information System (INIS)

Gyulassy, M.; Pluemer, M.

1989-10-01

The sensitivity of nuclear attenuation of 10-100 GeV lepton nucleus (ell A) reactions to space-time aspects of hadronization is investigated within the context of the Lund string model. We consider two mechanisms for attenuation in a nucleus: final state cascading and string flip excitations. Implications for the evolution of the energy density in nuclear collisions are discussed. 16 refs., 10 figs

Cryogenic magnet tests for the LHC process operation using web-based tools and facilities

CERN Document Server

Hemelsoet, G H; Chohan, V; Veyrunes, E

2005-01-01

For the Large Hadron Collider under construction at CERN, an essential requirement is the acceptance test of its 1706 Cryo-magnets in cryogenic conditions in a purpose-built facility at CERN. Several teams ensure the proper operation of the infrastructure on a round the clock basis. The cold test part is one of the key elements amongst many other essential activities requiring magnet transport and connections/disconnections, cryogenic preparation and pumping, cooling down to 1.9 K as well warm up before disconnection & removal. All these operations involve multi-tasking and usage of 12 test benches with nominal turn-round time per dipole magnet of 120 hours. It also involves multiple teams of industrial contractors, a support contract for cryogenics operation, CERN staff in magnet testing Operation, aided by a large external collaboration of visiting staff for round the clock operation. This paper gives a flavour of the operation and exposes the software tools that were necessary, designed and developed t...

A Cryogenic Test Stand for LHC Quadrupole Magnets

International Nuclear Information System (INIS)

Carcagno, R.H.; Huang, Y.; Orris, D.F.; Peterson, T.J.; Rabehl, R.J.

2004-01-01

A new test stand for testing LHC interaction region (IR) quadrupole magnets at the Fermilab Magnet Test Facility has been designed and operated. The test stand uses a double bath system with a lambda plate to provide the magnet with a stagnant bath of pressurized He II at 1.9 K and 0.13 MPa. A cryostated magnet 0.91 m in diameter and up to 13 m in length can be accommodated. This paper describes the system design and operation. Issues related to both 4.5 K and 1.9 K operations and magnet quenching are highlighted. An overview of the data acquisition and cryogenics controls systems is also included

Testing the Foundations of Relativity Using Cryogenic Optical Resonators

Science.gov (United States)

Müller, H.; Braxmaier, C.; Herrmann, S.; Pradl, O.; Lämmerzahl, C.; Mlynek, J.; Schiller, S.; Peters, A.

We present a new generation of experiments using cryogenic optical resonators(COREs) to test the foundations of relativity. The experiments test the isotropy of the speed of light (Michelson-Morley experiment), the independece of the speed of light from the velocity of the laboratory (Kennedy-Thorndike experiments), and the gravitational redshift for clocks based on an electronic transition. Compared with the best previous results, our tests have already yielded improvements up to a factor of three. Future versions promise significant improvements.

Cryogenic systems for the SSC and the status of their development

International Nuclear Information System (INIS)

Fietz, W.A.; Ganni, V.; Abramovich, S.; Niehaus, T.

1993-07-01

The Superconducting Super Collider (SSC) consists of two parallel magnet rings, each 87,120 m in circumference, constructed in a tunnel 25 to 74 m underground. Protons are injected into these ring from the high energy booster (HEB), which contains a separate magnet ring 10,800 m in circumference constructed in a tunnel 14 m above the collider tunnel. The magnets will be operated at a controlled low temperature in order to maintain the windings in the superconducting state. Therefore the magnet cryostat is designed with a high vacuum insulating chamber, multilayer insulation (MLI), and thermal shields at 84 K and 20 K nominal temperatures. The major portion of the heat load is from thermal radiation and conduction through the supports, and is intercepted and absorbed by the shields. The cryogenic system for the machine is divided into sectors of nominally equal length: ten for the collider and two for the HEB. Each sector has a dedicated cryogenic system (SCS) as well as some level of redundancy from the neighboring SCS. The helium refrigeration plants will be installed at the midpoint of each sector. Each cryogenic sector in the collider is divided into four strings, two upper and two lower, about 4000 m long. Each string is subdivided into sections of about 1080 m, the smallest modules that can be isolated for maintenance, or for warmup and cooldown. Each section is subdivided into cells and half cells. The half cell, containing six main magnets and a spool piece is 90 m long. The SSC cryogenic system for each sector consists of a sector refrigerator surface system (SRS) and a sector refrigerator tunnel system (SRT). Proposals for the SRS systems' are presently in review for vendor selection. In this paper the SRT subsystems requirements and their status will be reviewed

Test method for measuring insulation values of cryogenic pipes

NARCIS (Netherlands)

Velthuis, J.F.M.; Blokland, H.; Klaver, B.W.; Beld, C. van de

2010-01-01

In this paper a large-area heat flux and temperature sensor (HFT) is used for the evaluation of the insulation value of cryogenic pipes. The HFT is flexible and clamp-on. The test method is relatively simple and can be used in-situ. The HFT makes it possible to monitor insulation performance over

Test plan for air monitoring during the Cryogenic Retrieval Demonstration

International Nuclear Information System (INIS)

Yokuda, E.

1992-06-01

This report presents a test plan for air monitoring during the Cryogenic Retrieval Demonstration (CRD). Air monitors will be used to sample for the tracer elements neodymium, terbium, and ytterbium, and dysprosium. The results from this air monitoring will be used to determine if the CRD is successful in controlling dust and minimizing contamination. Procedures and equipment specifications for the test are included

Construction of cryogenic testing system and tensile deformation behavior of AISI 300 series stainless steels at cryogenic temperatures

International Nuclear Information System (INIS)

Lee, H.M.; Nahm, S.H.; Huh, Y.H.; Lee, J.J.; Bahng, G.W.

1990-01-01

For practical application of cryogenic engineering, development and characterization of structural materials for use at low temperatures are essential. For these purposes, a system for mechanical testing at liquid helium temperatures was developed and it was shown that the precision and accuracy of the system met the requirements of standards for materials testing machines. Using this system, tensile deformation behavior of AISI 304,316 and 310S austenitic stainless steels at cryogenic temperatures was investigated. Tests were conducted on round, tensile specimens having a 6.25mm diameter at 4,77, and 295 K and loading rate was 0.5mm/min. Serrations were observed in all alloys at 4 K. The stress-displacement curves at 77 and 4 K showed different tendency from those at 298 K. As the testing temperature decreased, ultimate strengths of 304 and 316 were largely increased compared to the increase of yield strengths, but the increase of ultimate strength of 310S was almost the same to that of yield strength. Type 310S had the highest yield strength and the lowest tensile strength at all temperatutes. These tensile characteristics were considered to be strongly affected by austenite stability.(Author)

The SSC full cell prototype string test

International Nuclear Information System (INIS)

Kraushaar, P.; Burgett, W.; Cromer, L.

1994-11-01

At the conclusion of the SSC half cell magnet string testing program. In February, 1993, the preliminary data analysis revealed that several substantive technical questions remained unresolved. These questions were: (1) could the high voltages to ground (>2 kV) measured during fault (quench) conditions be substantially reduced, (2) could the number of magnetic elements that became resistive (quenched) be controlled and (3) did the cryostats of the magnetic elements provide adequate insulation and isolation to meet designed refrigeration loads. To address these and other existing question a prototypical full cell of collider magnets (ten dipoles and two quadrupoles) was assembled and tested. At the conclusion of this testing there were definitive answers to most of the questions with numerical substantiation, the notable exception being the beat leak question. These answers and other results and issues are presented in this paper

The SSC full cell prototype string test

International Nuclear Information System (INIS)

McInturff, A.D.; Kraushaar, P.; Burgett, W.; Cromer, L.

1994-01-01

At the conclusion of the SSC half cell magnet string testing program in February, 1993, the preliminary data analysis revealed that several substantive technical questions remained unresolved. These questions were: (1) could the high voltages to ground (>2 kV) measured during fault (quench) conditions be substantially reduced, (2) could the number of magnetic elements that became resistive (quenched) be controlled and 3) did the cryostats of the magnetic elements provide adequate insulation and isolation to meet designed refrigeration loads. To address these and other existing questions, a prototypical fall cell of collider magnets (ten dipoles and two quadrupoles) was assembled and tested. At the conclusion of this testing there were definitive answers to most of the questions with numerical substantiation, the notable exception being the beat leak question. These answers and other results and issues are presented in this paper

Energy Efficient Cryogenics

Science.gov (United States)

Meneghelli, Barry J.; Notardonato, William; Fesmire, James E.

2016-01-01

The Cryogenics Test Laboratory, NASA Kennedy Space Center, works to provide practical solutions to low-temperature problems while focusing on long-term technology targets for the energy-efficient use of cryogenics on Earth and in space.

Upgrade of the cryogenic infrastructure of SM18, CERN main test facility for superconducting magnets and RF cavities

Science.gov (United States)

Perin, A.; Dhalla, F.; Gayet, P.; Serio, L.

2017-12-01

SM18 is CERN main facility for testing superconducting accelerator magnets and superconducting RF cavities. Its cryogenic infrastructure will have to be significantly upgraded in the coming years, starting in 2019, to meet the testing requirements for the LHC High Luminosity project and for the R&D program for superconducting magnets and RF equipment until 2023 and beyond. This article presents the assessment of the cryogenic needs based on the foreseen test program and on past testing experience. The current configuration of the cryogenic infrastructure is presented and several possible upgrade scenarios are discussed. The chosen upgrade configuration is then described and the characteristics of the main newly required cryogenic equipment, in particular a new 35 g/s helium liquefier, are presented. The upgrade implementation strategy and plan to meet the required schedule are then described.

Cryogenic systems for the Mirror Fusion Test Facility

International Nuclear Information System (INIS)

Slack, D.S.; Nelson, R.L.; Chronis, W.C.

1985-08-01

This paper includes an in-depth discussion of the design, fabrication, and operation of the Mirror Fusion Test Facility (MFTF) cryogenic system located at Lawrence Livermore National Laboratory (LLNL). Each subsystem discussed to present a basic composite of the entire facility. The following subsystems are included: 500kW nitrogen reliquefier, subcoolers, and distribution system; 15kW helium refrigerator/liquefier and distribution system; helium recovery and storage system; rough vacuum and high vacuum systems

Collisions of cosmic F- and D-strings

International Nuclear Information System (INIS)

Jones, N.

2004-01-01

Recent theoretical advances and upcoming experimental measurements make the testing of generic predictions of string theory models of cosmology feasible. Brane anti-brane models of inflation within superstring theory are promising as string theory descriptions of the physics of the early universe. While varied in their construction, these models can have the generic and observable consequence that cosmic strings will be abundant in the early universe. This leads to possible detectable effects in the cosmic microwave background, gravitational wave physics and gravitational lensing. Detailed calculations of cosmic string interactions within string theory are presented, in order to distinguish these cosmic strings from those in more conventional theories; these interaction probabilities can be very different from conventional 4-dimension strings, providing the possibility of experimental tests of string theory. (authors)

Upgrade of the Cryogenic CERN RF Test Facility

CERN Document Server

Pirotte, O; Brunner, O; Inglese, V; Koettig, T; Maesen, P; Vullierme, B

2014-01-01

With the large number of superconducting radiofrequency (RF) cryomodules to be tested for the former LEP and the present LHC accelerator a RF test facility was erected early in the 1990’s in the largest cryogenic test facility at CERN located at Point 18. This facility consisted of four vertical test stands for single cavities and originally one and then two horizontal test benches for RF cryomodules operating at 4.5 K in saturated helium. CERN is presently working on the upgrade of its accelerator infrastructure, which requires new superconducting cavities operating below 2 K in saturated superfluid helium. Consequently, the RF test facility has been renewed in order to allow efficient cavity and cryomodule tests in superfluid helium and to improve its thermal performances. The new RF test facility is described and its performances are presented.

Upgrade of the cryogenic CERN RF test facility

International Nuclear Information System (INIS)

Pirotte, O.; Benda, V.; Brunner, O.; Inglese, V.; Maesen, P.; Vullierme, B.; Koettig, T.

2014-01-01

With the large number of superconducting radiofrequency (RF) cryomodules to be tested for the former LEP and the present LHC accelerator a RF test facility was erected early in the 1990’s in the largest cryogenic test facility at CERN located at Point 18. This facility consisted of four vertical test stands for single cavities and originally one and then two horizontal test benches for RF cryomodules operating at 4.5 K in saturated helium. CERN is presently working on the upgrade of its accelerator infrastructure, which requires new superconducting cavities operating below 2 K in saturated superfluid helium. Consequently, the RF test facility has been renewed in order to allow efficient cavity and cryomodule tests in superfluid helium and to improve its thermal performances. The new RF test facility is described and its performances are presented

Autonomous Cryogenic Load Operations: Knowledge-Based Autonomous Test Engineer

Science.gov (United States)

Schrading, J. Nicolas

2013-01-01

The Knowledge-Based Autonomous Test Engineer (KATE) program has a long history at KSC. Now a part of the Autonomous Cryogenic Load Operations (ACLO) mission, this software system has been sporadically developed over the past 20 years. Originally designed to provide health and status monitoring for a simple water-based fluid system, it was proven to be a capable autonomous test engineer for determining sources of failure in the system. As part of a new goal to provide this same anomaly-detection capability for a complicated cryogenic fluid system, software engineers, physicists, interns and KATE experts are working to upgrade the software capabilities and graphical user interface. Much progress was made during this effort to improve KATE. A display of the entire cryogenic system's graph, with nodes for components and edges for their connections, was added to the KATE software. A searching functionality was added to the new graph display, so that users could easily center their screen on specific components. The GUI was also modified so that it displayed information relevant to the new project goals. In addition, work began on adding new pneumatic and electronic subsystems into the KATE knowledge base, so that it could provide health and status monitoring for those systems. Finally, many fixes for bugs, memory leaks, and memory errors were implemented and the system was moved into a state in which it could be presented to stakeholders. Overall, the KATE system was improved and necessary additional features were added so that a presentation of the program and its functionality in the next few months would be a success.

Test results and operational characteristics of prototype SSCL half cell

International Nuclear Information System (INIS)

McInturff, A.D.; Burgett, W.; Carter, H.

1994-01-01

The SSCL Accelerator System's String Test (ASST) has had several cool down, subsequent operational test series, and warm up cycles. The first cycle of these was rather limited in scope as mandated by Congress. The subsequent tests have been performed to obtain more complete information about parameters of, or operating experience with, the ensemble of magnets and spools when operating serially as in accelerator operations. The tests and procedures performed to date have emphasized cryogenic, mechanical, and electrical operations. These have included running, as well as upset conditions, i.e., superconducting to normal transition of the string (quench). This paper represents a summary of the operational test results and characteristics seen to date. A limited discussion will be included as to their implications with respect to a successful accelerator operation

Are Stopped Strings Preferred in Sad Music?

OpenAIRE

David Huron; Caitlyn Trevor

2017-01-01

String instruments may be played either with open strings (where the string vibrates between the bridge and a hard wooden nut) or with stopped strings (where the string vibrates between the bridge and a performer's finger pressed against the fingerboard). Compared with open strings, stopped strings permit the use of vibrato and exhibit a darker timbre. Inspired by research on the timbre of sad speech, we test whether there is a tendency to use stopped strings in nominally sad music. Specifica...

Operation of the cryogenic system for the Mirror Fusion Test Facility

International Nuclear Information System (INIS)

Chronis, W.C.; Slack, D.S.

1987-01-01

The cryogenic system for the Mirror Fusion Test Facility (MFTF) at Lawrence Livermore National Laboratory (LLNL) was designed to cool the entire MFTF-B system from ambient to operating temperature in less than 10 days. The system was successfully operated in the recent plant and capital equipment (PACE) acceptance tests, and results from these tests helped us correct problem areas and improve the system

Some General Principles in Cryogenic Design, Implementation, and Testing

Science.gov (United States)

Dipirro, Michael James

2015-01-01

Brief Course Description: In 2 hours only the most basic principles of cryogenics can be presented. I will concentrate on the differences between a room temperature thermal analysis and cryogenic thermal analysis, namely temperature dependent properties. I will talk about practical materials for thermal contact and isolation. I will finish by describing the verification process and instrumentation used that is unique to cryogenic (in general less than 100K) systems.

Comparison of different cryogenic control strategies via simulation applied to a superconducting magnet test bench at CERN

Science.gov (United States)

Arpaia, P.; Coppier, H.; De Paola, D.; di Bernardo, M.; Guarino, A.; Pedemonte, B. Luz; Pezzetti, M.

2017-12-01

Industrial process controllers for cryogenic systems used in test facilities for superconducting magnets are typically PIDs, tuned by operational expertise according to users’ requirements (covering cryogenic transients and associated thermo-mechanical constraints). In this paper, an alternative fully-automatic solution, equally based on PID controllers, is proposed. Following the comparison of the operational expertise and alternative fully-automatic approaches, a new process control configuration, based on an estimated multiple-input/multiple-output (MIMO) model is proposed. The new MIMO model-based approach fulfils the required operational constraints while improving performance compared to existing solutions. The analysis and design work is carried out using both theoretical and numerical tools and is validated on the case study of the High Field Magnet (HFM) cryogenic test bench running at the SM18 test facility located at CERN. The proposed solution have been validated by simulation using the CERN ECOSIMPRO software tools using the cryogenic library (CRYOLIB [1]) developed at CERN.

String theory and quark confinement

International Nuclear Information System (INIS)

Polyakov, A.M.

1998-01-01

This article is based on a talk given at the ''Strings '97'' conference. It discusses the search for the universality class of confining strings. The key ingredients include the loop equations, the zigzag symmetry, the non-linear renormalization group. Some new tests for the equivalence between gauge fields and strings are proposed. (orig.)

Cryogenics in CEBAF HMS dipole

International Nuclear Information System (INIS)

Bogensberger, P.; Ramsauer, F.; Brindza, P.; Wines, R.; Koefler, H.

1994-01-01

The paper will report upon the final design, manufacturing and tests of CEBAF's HMS Dipole cryogenic equipment. The liquid nitrogen circuits, the helium circuits and thermal insulation of the magnet will be addressed. The cryogenic reservoir and control module as an integral part of the HMS Dipole magnet will be presented. The construction, manufacturing, tests and final performance of the HMS Dipole cryogenic system will be reported. The LN 2 circuit and the He circuit are tied together by the control system for cool down, normal operation and standby. This system monitors proper temperature differences between both circuits and controls the cryogenic supply to meet the constraints. Implementation of the control features for the cryogenic system into the control system will be reported

Spin chains and string theory.

Science.gov (United States)

Kruczenski, Martin

2004-10-15

Recently, an important test of the anti de Sitter/conformal field theory correspondence has been done using rotating strings with two angular momenta. We show that such a test can be described more generally as the agreement between two actions: one a low energy description of a spin chain appearing in the field theory side, and the other a limit of the string action in AdS5xS5. This gives a map between the mean value of the spin in the boundary theory and the position of the string in the bulk, and shows how a string action can emerge from a gauge theory in the large-N limit.

Performance of the JT-60SA cryogenic system under pulsed heat loads during acceptance tests

Science.gov (United States)

Hoa, C.; Bonne, F.; Roussel, P.; Lamaison, V.; Girard, S.; Fejoz, P.; Goncalves, R.; Vallet, J. C.; Legrand, J.; Fabre, Y.; Pudys, V.; Wanner, M.; Cardella, A.; Di Pietro, E.; Kamiya, K.; Natsume, K.; Ohtsu, K.; Oishi, M.; Honda, A.; Kashiwa, Y.; Kizu, K.

2017-12-01

The JT-60SA cryogenic system a superconducting tokamak currently under assembly at Naka, Japan. After one year of commissioning, the acceptance tests were successfully completed in October 2016 in close collaboration with Air Liquide Advanced Technologies (ALaT), the French atomic and alternative energies commission (CEA), Fusion for Energy (F4E) and the Quantum Radiological Science and Technology (QST). The cryogenic system has several cryogenic users at various temperatures: the superconducting magnets at 4.4 K, the current leads at 50 K, the thermal shields at 80 K and the divertor cryo-pumps at 3.7 K. The cryogenic system has an equivalent refrigeration power of about 9.5 kW at 4.5 K, with peak loads caused by the nuclear heating, the eddy currents in the structures and the AC losses in the magnets during cyclic plasma operation. The main results of the acceptance tests will be reported, with emphasis on the management of the challenging pulsed load operation using a liquid helium volume of 7 m3 as a thermal damper.

Cryogenic Infrastructure for Testing of LHC Series Superconducting Magnets

CERN Document Server

Axensalva, J; Herblin, L; Lamboy, J P; Tovar-Gonzalez, A; Vuillerme, B

2005-01-01

The ~1800 superconducting magnets for the LHC machine shall be entirely tested at reception before their installation in the tunnel. For this purpose and in order to reach the reliability and efficiency at the nominal load required for an industrial operation for several years, we have gradually upgraded and retrofitted the cryogenic facilities installed in the early nineties for the testing at CERN of prototypes and preseries magnets. The final infrastructure of the test station, dedicated to check industrially the quality of the series magnets, is now nearly complete. We present the general layout and describe the overall performance of the system.

Mechanical Properties of Nylon Harp Strings

Science.gov (United States)

Lynch-Aird, Nicolas; Woodhouse, Jim

2017-01-01

Monofilament nylon strings with a range of diameters, commercially marketed as harp strings, have been tested to establish their long-term mechanical properties. Once a string had settled into a desired stress state, the Young’s modulus was measured by a variety of methods that probe different time-scales. The modulus was found to be a strong function of testing frequency and also a strong function of stress. Strings were also subjected to cyclical variations of temperature, allowing various thermal properties to be measured: the coefficient of linear thermal expansion and the thermal sensitivities of tuning, Young’s modulus and density. The results revealed that the particular strings tested are divided into two groups with very different properties: stress-strain behaviour differing by a factor of two and some parametric sensitivities even having the opposite sign. Within each group, correlation studies allowed simple functional fits to be found to the key properties, which have the potential to be used in automated tuning systems for harp strings. PMID:28772858

Mechanical Properties of Nylon Harp Strings

Directory of Open Access Journals (Sweden)

Nicolas Lynch-Aird

2017-05-01

Full Text Available Monofilament nylon strings with a range of diameters, commercially marketed as harp strings, have been tested to establish their long-term mechanical properties. Once a string had settled into a desired stress state, the Young’s modulus was measured by a variety of methods that probe different time-scales. The modulus was found to be a strong function of testing frequency and also a strong function of stress. Strings were also subjected to cyclical variations of temperature, allowing various thermal properties to be measured: the coefficient of linear thermal expansion and the thermal sensitivities of tuning, Young’s modulus and density. The results revealed that the particular strings tested are divided into two groups with very different properties: stress-strain behaviour differing by a factor of two and some parametric sensitivities even having the opposite sign. Within each group, correlation studies allowed simple functional fits to be found to the key properties, which have the potential to be used in automated tuning systems for harp strings.

Interacting-string picture of the fermionic string

International Nuclear Information System (INIS)

Mandelstam, S.

1986-01-01

This report gives a review of the interacting-string picture of the Bose string. In the present lecture, the author outlines a similar treatment of the Fermionic string. The quantization of the free Fermionic string is carried out to the degrees of freedom x, representing the displacement of the string. Also presented are Grassman degrees of freedom S distributed along the string. The report pictures the fermionic string as a string of dipoles. The general picture of the interaction of such strings by joining and splitting is the same as for the Bose string. The author does not at present have the simplest formula for fermion string scattering amplitudes. A less detailed treatment is given than for the Bose string. The report sets up the functional-integration formalism, derives the analog mode, and indicates in general, terms how the conformal transformation to the z-plane may be performed. The paper concludes by stating without proof the formula for the N-article tree amplitude in the manifestly supersymmetric formalism

Electron string ion sources for carbon ion cancer therapy accelerators

Science.gov (United States)

Boytsov, A. Yu.; Donets, D. E.; Donets, E. D.; Donets, E. E.; Katagiri, K.; Noda, K.; Ponkin, D. O.; Ramzdorf, A. Yu.; Salnikov, V. V.; Shutov, V. B.

2015-08-01

The type of the Electron String Ion Sources (ESIS) is considered to be the appropriate one to produce pulsed C4+ and C6+ ion beams for cancer therapy accelerators. In fact, the new test ESIS Krion-6T already now provides more than 1010 C4+ ions per pulse and about 5 × 109 C6+ ions per pulse. Such ion sources could be suitable to apply at synchrotrons. It has also been found that Krion-6T can provide more than 1011 C6+ ions per second at the 100 Hz repetition rate, and the repetition rate can be increased at the same or larger ion output per second. This makes ESIS applicable at cyclotrons as well. ESIS can be also a suitable type of ion source to produce the 11C radioactive ion beams. A specialized cryogenic cell was experimentally tested at the Krion-2M ESIS for pulse injection of gaseous species into the electron string. It has been shown in experiments with stable methane that the total conversion efficiency of methane molecules to C4+ ions reached 5%÷10%. For cancer therapy with simultaneous irradiation and precise dose control (positron emission tomography) by means of 11C, transporting to the tumor with the primary accelerated 11C4+ beam, this efficiency is preliminarily considered to be large enough to produce the 11C4+ beam from radioactive methane and to inject this beam into synchrotrons.

Structure Formation in Complex Plasma - Quantum Effects in Cryogenic Complex Plasmas

Science.gov (United States)

2014-09-26

strings. Analytical perturbation study supports the findings of numerical simulations. (Paper #2) Theory In a cryogenic plasma Debye length becomes...the Debye length , while ions are trapped at a certain distance around a dust particle without hitting the surface. Negatively charged dust particles...glass tube of 100cm in length and 15cm in inner diameter. The tube is connected to the bellows at the left end. A stainless steel plate of 2mm in

The cryogenic pumping section of KATRIN and the test experiment TRAP

CERN Document Server

Eichelhardt, F

2011-01-01

The Karlsruhe Tritium Neutrino experiment (KATRIN) employs a Cryogenic Pumping Section (CPS) at ~ 4.5 K to suppress the tritium penetration into the spectrometers. A test experiment (TRAP - Tritium Argon frost Pump) has been set up to investigate the tritium pumping performance of the CPS.

James Webb Space Telescope Core 2 Test - Cryogenic Thermal Balance Test of the Observatorys Core Area Thermal Control Hardware

Science.gov (United States)

Cleveland, Paul; Parrish, Keith; Thomson, Shaun; Marsh, James; Comber, Brian

2016-01-01

The James Webb Space Telescope (JWST), successor to the Hubble Space Telescope, will be the largest astronomical telescope ever sent into space. To observe the very first light of the early universe, JWST requires a large deployed 6.5-meter primary mirror cryogenically cooled to less than 50 Kelvin. Three scientific instruments are further cooled via a large radiator system to less than 40 Kelvin. A fourth scientific instrument is cooled to less than 7 Kelvin using a combination pulse-tube Joule-Thomson mechanical cooler. Passive cryogenic cooling enables the large scale of the telescope which must be highly folded for launch on an Ariane 5 launch vehicle and deployed once on orbit during its journey to the second Earth-Sun Lagrange point. Passive cooling of the observatory is enabled by the deployment of a large tennis court sized five layer Sunshield combined with the use of a network of high efficiency radiators. A high purity aluminum heat strap system connects the three instrument's detector systems to the radiator systems to dissipate less than a single watt of parasitic and instrument dissipated heat. JWST's large scale features, while enabling passive cooling, also prevent the typical flight configuration fully-deployed thermal balance test that is the keystone of most space missions' thermal verification plans. This paper describes the JWST Core 2 Test, which is a cryogenic thermal balance test of a full size, high fidelity engineering model of the Observatory's 'Core' area thermal control hardware. The 'Core' area is the key mechanical and cryogenic interface area between all Observatory elements. The 'Core' area thermal control hardware allows for temperature transition of 300K to approximately 50 K by attenuating heat from the room temperature IEC (instrument electronics) and the Spacecraft Bus. Since the flight hardware is not available for test, the Core 2 test uses high fidelity and flight-like reproductions.

Super-light-weighted HB-Cesic® mirror cryogenic test

Science.gov (United States)

Devilliers, Christophe; Krödel, Matthias R.; Sodnik, Zoran; Robert, Patrick

2017-11-01

Future scientific space missions require ever more demanding large optics that work at cryogenic temperatures. In the frame of a Darwin assessment study conducted under ESA contract by TAS, the need of future very lightweight cryogenic mirrors with superior optical quality has been identified. Such mirrors need to be of size up to 3.5 m in diameter, with a mass of less than 250 kg (i.e. 25 kg/m2) and possess excellent optical quality at cryogenic temperature down to 40 K.

Lessons Learned During Cryogenic Optical Testing of the Advanced Mirror System Demonstrators (AMSDs)

Science.gov (United States)

Hadaway, James; Reardon, Patrick; Geary, Joseph; Robinson, Brian; Stahl, Philip; Eng, Ron; Kegley, Jeff

2004-01-01

Optical testing in a cryogenic environment presents a host of challenges above and beyond those encountered during room temperature testing. The Advanced Mirror System Demonstrators (AMSDs) are 1.4 m diameter, ultra light-weight (mA2), off-axis parabolic segments. They are required to have 250 nm PV & 50 nm RMS surface figure error or less at 35 K. An optical testing system, consisting of an Instantaneous Phase Interferometer (PI), a diffractive null corrector (DNC), and an Absolute Distance Meter (ADM), was used to measure the surface figure & radius-of-curvature of these mirrors at the operational temperature within the X-Ray Calibration Facility (XRCF) at Marshall Space Flight Center (MSFC). The Ah4SD program was designed to improve the technology related to the design, fabrication, & testing of such mirrors in support of NASA s James Webb Space Telescope (JWST). This paper will describe the lessons learned during preparation & cryogenic testing of the AMSDs.

A 6 kW at 4.5 K helium refrigerator for CERN's Cryogenic Test Station

International Nuclear Information System (INIS)

Gistau, G.M.; Bonneton, M.

1994-01-01

For purposes of testing the present LEP superconducting resonant cavities and the future LHC magnets, CERN built a test station the cryogenic power of which is presently supplied by a dedicated 6 kW at 4.5 K helium refrigerator. The thermodynamic cycle is discussed and special emphasis is put on a new cryogenic expansion turbine operating in the liquid phase. Information is given about: the cycle screw compressors' performances, the general performance of the refrigerator, the expected efficiency enhancement due to the liquid turbine, an off-design turn down operation

Results of radiation tests at cryogenic temperature on some selected organic materials for the LHC

International Nuclear Information System (INIS)

Tavlet, M.; Schoenbacher, H.

1999-01-01

In the near future, particle accelerators and detectors as well as fusion reactors will operate at cryogenic temperatures. At temperatures as low as 2 K, the organic materials used for the insulation of the superconducting magnets and cables will be exposed to high radiation levels. In this work, a representative selection of organic materials comprising insulating films, cable insulations and epoxy-type-impregnated resins were exposed to neutron and gamma radiation of nuclear reactors, both at ambient and cryogenic temperatures, and were subsequently mechanically tested. The results show that the radiation degradation is never worse in a cryogenic fluid than it is in usual ambient conditions. (author)

Cryogenic test of the 4 K / 2 K insert for the ARIEL e-Linac cryomodule

International Nuclear Information System (INIS)

Laxdal, R. E.; Ma, Y.; Harmer, P.; Kishi, D.; Koveshnikov, A.; Muller, N.; Vrielink, A.; O'Brien, M.; Ahammed, M.

2014-01-01

The ARIEL project at TRIUMF requires a 50 MeV superconducting electron linac consisting of five nine cell 1.3 GHz cavities divided into three cryomodules with one, two and two cavities in each module respectively. LHe is distributed in parallel to each module at 4 K and at ∼1.2 bar. Each module has a cryogenic insert on board that receives the 4 K liquid and produces 2 K into a cavity phase separator. The module combines a 4 K phase separator, a plate and fin heat exchanger from DATE and a J-T valve expanding into the 2 K phase separator. The unit also supplies 4 K liquid to thermal intercepts in the module in siphon loops that return the vaporized liquid to the 4 K reservoir. For testing purposes the unit is outfitted with a dummy 2 K phase separator and thermal intercepts with variable heaters that mimic the final heat loads in order to test the cryogenic performance. The design of the 4 K / 2 K insert, the results of the cold tests and a summary of the test infrastructure including cryogenics services will be presented

Cryogenic test of the 4 K / 2 K insert for the ARIEL e-Linac cryomodule

Energy Technology Data Exchange (ETDEWEB)

Laxdal, R. E.; Ma, Y.; Harmer, P.; Kishi, D.; Koveshnikov, A.; Muller, N.; Vrielink, A. [TRIUMF, 4004 Wesbrook Mall, Vancouver, BC (Canada); O' Brien, M. [University of British Columbia, Vancouver (Canada); Ahammed, M. [Variable Energy Cyclotron Center, Kolkata (India)

2014-01-29

The ARIEL project at TRIUMF requires a 50 MeV superconducting electron linac consisting of five nine cell 1.3 GHz cavities divided into three cryomodules with one, two and two cavities in each module respectively. LHe is distributed in parallel to each module at 4 K and at ∼1.2 bar. Each module has a cryogenic insert on board that receives the 4 K liquid and produces 2 K into a cavity phase separator. The module combines a 4 K phase separator, a plate and fin heat exchanger from DATE and a J-T valve expanding into the 2 K phase separator. The unit also supplies 4 K liquid to thermal intercepts in the module in siphon loops that return the vaporized liquid to the 4 K reservoir. For testing purposes the unit is outfitted with a dummy 2 K phase separator and thermal intercepts with variable heaters that mimic the final heat loads in order to test the cryogenic performance. The design of the 4 K / 2 K insert, the results of the cold tests and a summary of the test infrastructure including cryogenics services will be presented.

Novel device to sample the esophageal microbiome--the esophageal string test.

Directory of Open Access Journals (Sweden)

Sophie A Fillon

Full Text Available A growing number of studies implicate the microbiome in the pathogenesis of intestinal inflammation. Previous work has shown that adults with esophagitis related to gastroesophageal reflux disease have altered esophageal microbiota compared to those who do not have esophagitis. In these studies, sampling of the esophageal microbiome was accomplished by isolating DNA from esophageal biopsies obtained at the time of upper endoscopy. The aim of the current study was to identify the esophageal microbiome in pediatric individuals with normal esophageal mucosa using a minimally invasive, capsule-based string technology, the Enterotest™. We used the proximal segment of the Enterotest string to sample the esophagus, and term this the "Esophageal String Test" (EST. We hypothesized that the less invasive EST would capture mucosal adherent bacteria present in the esophagus in a similar fashion as mucosal biopsy. EST samples and mucosal biopsies were collected from children with no esophageal inflammation (n = 15 and their microbiome composition determined by 16S rRNA gene sequencing. Microbiota from esophageal biopsies and ESTs produced nearly identical profiles of bacterial genera and were different from the bacterial contents of samples collected from the nasal and oral cavity. We conclude that the minimally invasive EST can serve as a useful device for study of the esophageal microbiome.

Deriving the four-string and open-closed string interactions from geometric string field theory

International Nuclear Information System (INIS)

Kaku, M.

1990-01-01

One of the questions concerning the covariant open string field theory is why there are two distinct BRST theories and why the four-string interaction appears in one version but not the other. The authors solve this mystery by showing that both theories are gauge-fixed versions of a higher gauge theory, called the geometric string field theory, with a new field, a string verbein e μσ νρ , which allows us to gauge the string length and σ parametrization. By fixing the gauge, the authors can derive the endpoint gauge (the covariantized light cone gauge), the midpoint gauge of Witten, or the interpolating gauge with arbitrary string length. The authors show explicitly that the four-string interaction is a gauge artifact of the geometric theory (the counterpart of the four-fermion instantaneous Coulomb term of QED). By choosing the interpolating gauge, they produce a new class of four-string interactions which smoothly interpolate between the endpoint gauge and the midpoint gauge (where it vanishes). Similarly, they can extract the closed string as a bound state of the open string, which appears in the endpoint gauge but vanishes in the midpoint gauge. Thus, the four-string and open-closed string interactions do not have to be added to the action as long as the string vierbein is included

A Low Heat Inleak Cryogenic Station for Testing HTS Current Leads for the Large Hadron Collider

CERN Document Server

Ballarino, A; Gomes, P; Métral, L; Serio, L; Suraci, A

1999-01-01

The LHC will be equipped with about 8000 superconducting magnets of all types. The total current to be transported into the cryogenic enclosure amounts to some 3360 kA. In order to reduce the heat load into the liquid helium, CERN intends to use High Temperature Superconducting (HTS) material for leads having current ratings up to 13 kA. The resistive part of the leads is cooled by forced flow of gaseous helium between 20 K and 300 K. The HTS part of the lead is immersed in a 4.5 K liquid helium bath, operates in self cooling conditions and is hydraulically separated from the resistive part. A cryogenic test station has been designed and built in order to assess the thermal and electrical performances of 13 kA prototype current leads. We report on the design, commissioning and operation of the cryogenic test station and illustrate its performance by typical test results of HTS current leads.

Development and testing of immersed-Bz diodes with cryogenic anodes

International Nuclear Information System (INIS)

Bruner, Nichelle Lee; Cordova, Steve Ray; Oliver, Bryan Velten; Portillo, Salvador; Cooper, Graham; Puetz, Elizabeth A.; Johnston, Mark D.; Hahn, Kelly Denise; McLean, John; Molina, Isidro; Droemer, Darryl W.; Welch, Dale R.; Rovang, Dean Curtis; Van De Valde, David M.; Gregerson, Darryl; Maenchen, John Eric; O'Malley, John

2005-01-01

Sandia National Laboratories is investigating and developing high-dose, high-brightness flash radiographic sources. The immersed-B z diode employs large-bore, high-field solenoid magnets to help guide and confine an intense electron beam from a needle-like cathode 'immersed' in the axial field of the magnet. The electron beam is focused onto a high-atomic-number target/anode to generate an intense source of bremsstrahlung X-rays. Historically, these diodes have been unable to achieve high dose (> 500 rad (at) m) from a small spot (< 3 mm diameter). It is believed that this limitation is due in part to undesirable effects associated with the interaction of the electron beam with plasmas formed at either the anode or the cathode. Previous research concentrated on characterizing the behavior of diodes, which used untreated, room temperature (RT) anodes. Research is now focused on improving the diode performance by modifying the diode behavior by using cryogenic anodes that are coated in-situ with frozen gases. The objective of these cryogenically treated anodes is to control and limit the ion species of the anode plasma formed and hence the species of the counter-streaming ions that can interact with the electron beam. Recent progress in the development, testing and fielding of the cryogenically cooled immersed diodes at Sandia is described.

Electron string ion sources for carbon ion cancer therapy accelerators

Energy Technology Data Exchange (ETDEWEB)

Boytsov, A. Yu.; Donets, D. E.; Donets, E. D.; Donets, E. E.; Ponkin, D. O.; Ramzdorf, A. Yu.; Salnikov, V. V.; Shutov, V. B. [Joint Institute for Nuclear Research, Dubna 141980 (Russian Federation); Katagiri, K.; Noda, K. [National Institute of Radiological Science, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555 (Japan)

2015-08-15

The type of the Electron String Ion Sources (ESIS) is considered to be the appropriate one to produce pulsed C{sup 4+} and C{sup 6+} ion beams for cancer therapy accelerators. In fact, the new test ESIS Krion-6T already now provides more than 10{sup 10} C{sup 4+} ions per pulse and about 5 × 10{sup 9} C{sup 6+} ions per pulse. Such ion sources could be suitable to apply at synchrotrons. It has also been found that Krion-6T can provide more than 10{sup 11} C{sup 6+} ions per second at the 100 Hz repetition rate, and the repetition rate can be increased at the same or larger ion output per second. This makes ESIS applicable at cyclotrons as well. ESIS can be also a suitable type of ion source to produce the {sup 11}C radioactive ion beams. A specialized cryogenic cell was experimentally tested at the Krion-2M ESIS for pulse injection of gaseous species into the electron string. It has been shown in experiments with stable methane that the total conversion efficiency of methane molecules to C{sup 4+} ions reached 5%÷10%. For cancer therapy with simultaneous irradiation and precise dose control (positron emission tomography) by means of {sup 11}C, transporting to the tumor with the primary accelerated {sup 11}C{sup 4+} beam, this efficiency is preliminarily considered to be large enough to produce the {sup 11}C{sup 4+} beam from radioactive methane and to inject this beam into synchrotrons.

The Mirror Fusion Test Facility cryogenic system: Performance, management approach, and present equipment status

International Nuclear Information System (INIS)

Slack, D.S.; Chronis, W.C.

1987-01-01

The cryogenic system for the Mirror Fusion Test Facility (MFTF) is a 14-kW, 4.35-K helium refrigeration system that proved to be highly successful and cost-effective. All operating objectives were met, while remaining within a few percent of initial cost and schedule plans. The management approach used in MFTF allowed decisions to be made quickly and effectively, and it helped keep costs down. Manpower levels, extent and type of industrial participation, key aspects of subcontractor specifications, and subcontractor interactions are reviewed, as well as highlights of the system tests, operation, and present equipment status. Organizations planning large, high-technology systems may benefit from this experience with the MFTF cryogenic system

Radiation tests at cryogenic temperature on selected organic materials for LHC

International Nuclear Information System (INIS)

Humer, K.; Weber, H.W.; Szeless, B.; Tavlet, M.

1997-01-01

Future multi-TeV particle accelerators like the CERN Large Hadron Collider (LHC) will use superconducting magnets in which organic materials will be exposed to high radiation levels at temperatures as low as 2 K. A representative selection of organic materials comprising insulating films, cable insulations, epoxy resins and composites were exposed to neutron and gamma radiation of a nuclear reactor. Depending on the type of materials, the integrated radiation doses varied between 180 kGy and 155 MGy. During irradiation, the samples were kept close to the boiling temperature of liquid nitrogen, i.e. at 80 K, and thereafter stored in liquid nitrogen and transferred at the same temperature into the testing device for measurement of tensile and flexural strength. Tests were carried out on the same materials at similar dose rates at room temperature, and the results are compared with the ones obtained at cryogenic temperature. They show that within the selected dose range, a number of organic materials are suitable for use in radiation fields of the LHC at cryogenic temperature

Are Stopped Strings Preferred in Sad Music?

Directory of Open Access Journals (Sweden)

David Huron

2017-01-01

Full Text Available String instruments may be played either with open strings (where the string vibrates between the bridge and a hard wooden nut or with stopped strings (where the string vibrates between the bridge and a performer's finger pressed against the fingerboard. Compared with open strings, stopped strings permit the use of vibrato and exhibit a darker timbre. Inspired by research on the timbre of sad speech, we test whether there is a tendency to use stopped strings in nominally sad music. Specifically, we compare the proportion of potentially open-to-stopped strings in a sample of slow, minor-mode movements with matched major-mode movements. By way of illustration, a preliminary analysis of Samuel Barber's famous Adagio from his Opus 11 string quartet shows that the selected key (B-flat minor provides the optimum key for minimizing open string tones. However, examination of a broader controlled sample of quartet movements by Haydn, Mozart and Beethoven failed to exhibit the conjectured relationship. Instead, major-mode movements were found to avoid possible open strings more than slow minor-mode movements.

Analysis and test of a breadboard cryogenic hydrogen/Freon heat exchanger

Science.gov (United States)

Desjardins, L. F.; Hooper, J.

1973-01-01

System studies required to verify a tube-in-tube cryogenic heat exchanger as optimum for the space shuttle mission are described. Design of the optimum configuration, which could be fabricated from commercially available hardware, is discussed. Finally, testing of the proposed configuration with supercritical hydrogen and Freon 21 is discussed and results are compared with thermal and dynamic analysis.

Cryogenics will cool LHC

International Nuclear Information System (INIS)

Anon.

2001-01-01

Results of the investigation into the cryogenic regulating line (QRL) performed by the LHC laboratory are presented. It is projected that eight cryogenic units located in five places around the LHC ring will provide superconducting magnets by liquid helium through eight cryogenic regulating lines of 3.2 km each. All QRL zones remain to be independent. CERN uses three test units with the aim of the certification of chosen constructions and verification of their thermal and mechanical efficiency before starting full-scale production [ru

Manufacturing and Installation of the Compound Cryogenic Distribution Line for the Large Hadron Collider

CERN Document Server

Riddone,, G; Bouillot, A; Brodzinski, K; Dupont, M; Fathallah, M; Fournel, JL; Gitton, E; Junker, S; Moussavi, H; Parente, C; Riddone, G

2007-01-01

The Large Hadron Collider (LHC) [1] currently under construction at CERN will make use of superconducting magnets operating in superfluid helium below 2 K. A compound cryogenic distribution line (QRL) will feed with helium at different temperatures and pressures the local elementary cooling loops in the cryomagnet strings. Low heat inleak to all temperature levels is essential for the overall LHC cryogenic performance. Following a competitive tendering, CERN adjudicated in 2001 the contract for the series line to Air Liquide (France). This paper recalls the main features of the technical specification and shows the project status. The basic choices and achievements for the industrialization phase of the series production are also presented, as well as the installation issues and status.

Exactly soluble dynamics of (p,q) string near macroscopic fundamental strings

International Nuclear Information System (INIS)

Bak, Dongsu; Rey, Soojong; Yee, Houng

2004-01-01

We study dynamics of type-IIB bound-state of a Dirichlet string and n fundamental strings in the background of N fundamental strings. Because of supergravity potential, the bound-state string is pulled to the background fundamental strings, whose motion is described by open string rolling radion field. The string coupling can be made controllably weak and, in the limit 1 2 st n 2 st N, the bound-state energy involved is small compared to the string scale. We thus propose rolling dynamics of open string radion in this system as an exactly solvable analog for rolling dynamics of open string tachyon in decaying D-brane. The dynamics bears a novel feature that the worldsheet electric field increases monotonically to the critical value as the bound-state string falls into the background string. Close to the background string, D string constituent inside the bound-state string decouples from fundamental string constituents. (author)

Thermal Performance Testing of Cryogenic Multilayer Insulation with Silk Net Spacers

International Nuclear Information System (INIS)

Johnson, W L; Frank, D J; Nast, T C; Fesmire, J E

2015-01-01

Early comprehensive testing of cryogenic multilayer insulation focused on the use of silk netting as a spacer material. Silk netting was used for multiple test campaigns that were designed to provide baseline thermal performance estimates for cryogenic insulation systems. As more focus was put on larger systems, the cost of silk netting became a deterrent and most aerospace insulation firms were using Dacron (or polyester) netting spacers by the early 1970s. In the midst of the switch away from silk netting there was no attempt to understand the difference between silk and polyester netting, though it was widely believed that the silk netting provided slightly better performance. Without any better reference for thermal performance data, the silk netting performance correlations continued to be used. In order to attempt to quantify the difference between the silk netting and polyester netting, a brief test program was developed. The silk netting material was obtained from Lockheed Martin and was tested on the Cryostat-100 instrument in three different configurations, 20 layers with both single and double netting and 10 layers with single netting only. The data show agreement within 15 - 30% with the historical silk netting based correlations and show a substantial performance improvement when compared to previous testing performed using polyester netting and aluminum foil/fiberglass paper multilayer insulation. Additionally, the data further reinforce a recently observed trend that the heat flux is not directly proportional to the number of layers installed on a system. (paper)

BRST invariant mixed string vertex for the bosonic string

International Nuclear Information System (INIS)

Clarizia, A.; Pezzella, F.

1987-09-01

We construct a BRST invariant (N+M)-string vertex including both open and closed string states. When we saturate it with N open string and M closed string physical states it reproduces their corresponding scattering amplitude. As a particular case we obtain BRST invariant vertex for the open-closed string transition. (orig.)

Introduction to string theory and string compactifications

International Nuclear Information System (INIS)

GarcIa-Compean, Hugo

2005-01-01

Basics of some topics on perturbative and non-perturbative string theory are reviewed. After a mathematical survey of the Standard Model of particle physics and GUTs, the bosonic string kinematics for the free case and with interaction is described. The effective action of the bosonic string and the spectrum is also discussed. T-duality in closed and open strings and the definition of D-brane are surveyed. Five perturbative superstring theories and their spectra is briefly outlined. Calabi-Yau three-fold compactifications of heterotic strings and their relation to some four-dimensional physics are given. Finally, non-perturbative issues like S-duality, M-theory and F-theory are also reviewed

Commissioning the cryogenic system of the first LHC sector

International Nuclear Information System (INIS)

Millet, F.; Claudet, S.; Ferlin, G.; Perin, A.; Riddone, G.; Serio, L.; Soubiran, M.; Tavian, L.; CERN; Ronayette, L.; GHMFL, Grenoble; Rabehl, R.; Fermilab

2007-01-01

The LHC machine, composed of eight sectors with superconducting magnets and accelerating cavities, requires a complex cryogenic system providing high cooling capacities (18 kW equivalent at 4.5 K and 2.4 W at 1.8 K per sector produced in large cold boxes and distributed via 3.3-km cryogenic transfer lines). After individual reception tests of the cryogenic subsystems (cryogen storages, refrigerators, cryogenic transfer lines and distribution boxes) performed since 2000, the commissioning of the cryogenic system of the first LHC sector has been under way since November 2006. After a brief introduction to the LHC cryogenic system and its specificities, the commissioning is reported detailing the preparation phase (pressure and leak tests, circuit conditioning and flushing), the cool-down sequences including the handling of cryogenic fluids, the magnet powering phase and finally the warm-up. Preliminary conclusions on the commissioning of the first LHC sector will be drawn with the review of the critical points already solved or still pending. The last part of the paper reports on the first operational experience of the LHC cryogenic system in the perspective of the commissioning of the remaining LHC sectors and the beam injection test

Open-closed string correspondence in open string field theory

International Nuclear Information System (INIS)

Baumgartl, M.; Sachs, I.

2008-01-01

We address the problem of describing different closed string backgrounds in background independent open string field theory: A shift in the closed string background corresponds to a collective excitation of open strings. As an illustration we apply the formalism to the case where the closed string background is a group manifold. (Abstract Copyright [2008], Wiley Periodicals, Inc.)

Cryogenic Fluid Management Facility

Science.gov (United States)

Eberhardt, R. N.; Bailey, W. J.

1985-01-01

The Cryogenic Fluid Management Facility is a reusable test bed which is designed to be carried within the Shuttle cargo bay to investigate the systems and technologies associated with the efficient management of cryogens in space. Cryogenic fluid management consists of the systems and technologies for: (1) liquid storage and supply, including capillary acquisition/expulsion systems which provide single-phase liquid to the user system, (2) both passive and active thermal control systems, and (3) fluid transfer/resupply systems, including transfer lines and receiver tanks. The facility contains a storage and supply tank, a transfer line and a receiver tank, configured to provide low-g verification of fluid and thermal models of cryogenic storage and transfer processes. The facility will provide design data and criteria for future subcritical cryogenic storage and transfer system applications, such as Space Station life support, attitude control, power and fuel depot supply, resupply tankers, external tank (ET) propellant scavenging, and ground-based and space-based orbit transfer vehicles (OTV).

Test Results of Selected Commercial DC/DC Converters under Cryogenic Temperatures - A Digest

Science.gov (United States)

Patterson, Richard; Hammoud, Ahmad

2010-01-01

DC/DC converters are widely used in space power systems in the areas of power management and distribution, signal conditioning, and motor control. Design of DC/DC converters to survive cryogenic temperatures will improve the power system performance, simplify design, and reduce development and launch costs. In this work, the performance of nine COTS modular, low-tomedium power DC/DC converters was investigated under cryogenic temperatures. The converters were evaluated in terms of their output regulation, efficiency, and input and output currents. At a given temperature, these properties were obtained at various input voltages and at different load levels. A summary on the performance of the tested converters was given. More comprehensive testing and in-depth analysis of performance under long-term exposure to extreme temperatures are deemed necessary to establish the suitability of these and other devices for use in the harsh environment of space exploration missions.

Cryogenics bringing the temperature down, underground

CERN Multimedia

2005-01-01

The first 600m of the LHC cryogenic distribution line (QRL), which will feed the accelerator's superconducting magnets, has passed initial validating tests of its mechanical design at room and cryogenic temperatures.

Testing of a cryogenic recooler heat exchanger at Brookhaven National Laboratory

International Nuclear Information System (INIS)

Nicoletti, A.; Wu, K.C.

1993-01-01

Brookhaven National Laboratory has tested a recooler heat exchanger intended to be used in the cryogenic system of the Relativistic Heavy Ion Collider. The unit is required to transfer 225 Watts from a supercritical helium stream flowing at 100 g/s to a helium bath boiling at 4.25 K. Measurements made with heat loads of 50 to over 450 Watts on the unit indicate its cooling capacity is greater than 400 Watts, as expected, and it will be suitable for use in the RHIC ring. Presented are the modifications made to BNL's MAGCOOL test facility that were necessary for testing, test procedure, and recooler performance

Neutron Irradiation Tests of Calibrated Cryogenic Sensors at Low Temperatures

CERN Document Server

Junquera, T; Thermeau, J P; Casas-Cubillos, J

1998-01-01

This paper presents the advancement of a program being carried out in view of selecting the cryogenic temperature sensors to be used in the LHC accelerator. About 10,000 sensors will be installed around the 26.6 km LHC ring, and most of them will be exposed to high radiation doses during the accelerator lifetime. The following thermometric sensors : carbon resistors, thin films, and platinum resistors, have been exposed to high neutron fluences (>10$^15$ n/cm$^2$) at the ISN (Grenoble, France) Cryogenic Irradiation Test Facility. A cryostat is placed in a shielded irradiation vault where a 20 MeV deuteron beam hits a Be target, resulting in a well collimated and intense neutron beam. The cryostat, the on-line acquisition system, the temperature references and the main characteristics of the irradiation facility are described. The main interest of this set-up is its ability to monitor online the evolution of the sensors by comparing its readout with temperature references that are in principle insensitive to t...

Quench propagation tests on the LHC superconducting magnet string

CERN Document Server

Coull, L; Krainz, G; Rodríguez-Mateos, F; Schmidt, R

1996-01-01

The installation and testing of a series connection of superconducting magnets (three 10 m long dipoles and one 3 m long quadrupole) has been a necessary step in the verification of the viability of the Large Hadron Collider at CERN. In the LHC machine, if one of the lattice dipoles or quadrupoles quenches, the current will be by-passed through cold diodes and the whole magnet chain will be de-excited by opening dump switches. In such a scenario it is very important to know whether the quench propagates from the initially quenching magnet to adjacent ones. A series of experiments have been performed with the LHC Test String powered at different current levels and at different de-excitation rates in order to understand possible mechanisms for such a propagation, and the time delays involved. Results of the tests and implications regarding the LHC machine operation are described in this paper.

Cooldown of superconducting magnet strings

International Nuclear Information System (INIS)

Yuecel, A.; Carcagno, R.H.

1995-01-01

A numerical model for the cooldown of the superconducting magnet strings in the Accelerator System String Test (ASST) Facility at the Superconducting Super Collider (SSC) Laboratory is presented. Numerical results are compared with experimental data from the ASST test runs. Agreement between the numerical predictions and experiments is very good over the entire range from room temperature to liquid helium temperatures. The model can be readily adapted to predict the cooldown and warmup behavior of other superconducting magnets or cold masses

CEBAF cryogenic system

International Nuclear Information System (INIS)

1995-01-01

The CEBAF cryogenic system consists of 3 refrigeration systems: Cryogenic Test Facility (CTF), Central Helium Liquefier (CHL), and End Station Refrigerator (ESR). CHL is the main cryogenic system for CEBAF, consisting of a 4.8 kW, 2.0 K refrigerator and transfer line system to supply 2.0 K and 12 kW of 50 K shield refrigeration for the Linac cavity cryostats and 10 g/s of liquid for the end stations. This paper describes the 9-year effort to commission these systems, concentrating on CHL with the cold compressors. The cold compressors are a cold vacuum pump with an inlet temperature of 3 K which use magnetic bearings, thereby eliminating the possibility of air leaks into the subatmospheric He

Cryogenic tests of the first two LHC quadrupole prototypes

International Nuclear Information System (INIS)

Genevey, P.; Deregel, J.; Perot, J.; Rifflet, J.M.; Vedrine, P.; Cortella, J.; Le Coroller, A.

1994-01-01

Two LHC (Large Hadron Collider) twin aperture quadrupole prototypes were constructed at CEA Saclay (a CERN-CEA collaboration agreement). Their main characteristics are: 3.05 m length, 56 mm coil aperture, 180 mm between the two apertures, 252 T/m nominal gradient at 15060 A. They have been tested and measured in the 1.8 K Saclay test facility in an horizontal cryostat. The magnets are instrumented in order to investigate their behaviour during cool-down, stand-by, powering and current ramping, quenching and warming-up. A summary of the cryogenic, mechanical, pressure and electrical measurements is presented. The quench protection heaters are efficient down to 3000 A. Losses during ramping up and down are reported. (from authors) 5 fig., 11 ref

ITER task T332a (1996) low-inventory cryogenic distillation tests

International Nuclear Information System (INIS)

Woodall, K.; Bellamy, D.

1997-02-01

The overall objective of this ITER task was to perform tests which would improve the accuracy of the ITER Isotope Separation System (ISS) tritium inventory estimates and to allow designers to lower the tritium and hydrogen inventory estimates. The work program was also designed to give a better understanding of cryogenic distillation hydraulics and provide information which would improve process control. The work program this year addressed the following specific task objectives. Measure the detailed hydraulics for deuterium/deuterium hydride mixtures in a cryogenic distillation column using Helipak C packing. Determine maximum vapour velocity, HETP and tritium and deuterium inventory data for a column that can be operated right up to flooding conditions. Determine if a proprietary surface treatment improves the wetting characteristics for hydrogen on stainless steel packing. Measure the isotope separation and inventory performance of a Helipak C column large enough to handle up to 45 mm. Investigate additional hydraulic effects in the reboiler and column. 7 refs., 7 figs

Testing effective string models of black holes with fixed scalars

International Nuclear Information System (INIS)

Krasnitz, M.; Klebanov, I.R.

1997-01-01

We solve the problem of mixing between the fixed scalar and metric fluctuations. First, we derive the decoupled fixed scalar equation for the four-dimensional black hole with two different charges. We proceed to the five-dimensional black hole with different electric (one-brane) and magnetic (five-brane) charges, and derive two decoupled equations satisfied by appropriate mixtures of the original fixed scalar fields. The resulting greybody factors are proportional to those that follow from coupling to dimension (2,2) operators on the effective string. In general, however, the string action also contains couplings to chiral operators of dimension (1,3) and (3,1), which cause disagreements with the semiclassical absorption cross sections. Implications of this for the effective string models are discussed. copyright 1997 The American Physical Society

Status of the Cryogenic Storage Ring (CSR)

Energy Technology Data Exchange (ETDEWEB)

Menk, Sebastian; Becker, Arno; Berg, Felix; Blaum, Klaus; Fellenberger, Florian; Froese, Michael; Goullon, Johannes; Grieser, Manfred; Krantz, Claude; Lange, Michael; Laux, Felix; Repnow, Roland; Schornikov, Andrey; Hahn, Robert von; Wolf, Andreas [Max-Planck-Institut fuer Kernphysik (MPIK), 69117 Heidelberg (Germany); Spruck, Kaija [Institut fuer Atom- und Molekuelphysik Justus-Liebig-Universitaet, 35392 Giessen (Germany)

2012-07-01

A novel cryogenic storage ring is currently under construction at the MPIK. By electrostatic ion optical elements, the 35 m circumference Cryogenic Storage Ring will be able to store ions at energies of up to 300 keV per charge unit without any mass limitations. The CSR consists of a cryogenic ({proportional_to}5 K) beam pipe surrounded by two radiation shields (40 and 80 K) in a large outer, thermal insulation vacuum. Extreme vacuum (density {proportional_to}10{sup 3} cm{sup -3}) will be achieved by 2 K cryopumping as demonstrated in a prototype ion beam trap. The ion optics was completely assembled within the precision cryogenic mounting and shielding structure of the first corner. There, cooldown tests to {proportional_to}40 K were performed which confirmed the required sub-millimeter accuracy of the specially designed electrode positioning under large temperature changes. The high-voltage connections to the cryogenic electrodes were installed and breakdown tests will be reported. Based on the test results the beam pipe, electrode mounting and shielding structures are under final construction for mounting during 2012.

CRYogenic Orbital TEstbed Ground Test Article Thermal Analysis

Science.gov (United States)

Piryk, David; Schallhorn, Paul; Walls, Laurie; Stopnitzky, Benny; Rhys, Noah; Wollen, Mark

2012-01-01

The purpose of this study was to anchor thermal and fluid system models to CRYOTE ground test data. The CRYOTE ground test artide was jointly developed by Innovative Engineering Solutions, United Launch Alliance and NASA KSC. The test article was constructed out of a titanium alloy tank, Sapphire 77 composite skin (similar to G10), an external secondary payload adapter ring, thermal vent system, multi layer insulation and various data acquisition instrumentation. In efforts to understand heat loads throughout this system, the GTA (filled with liquid nitrogen for safety purposes) was subjected to a series of tests in a vacuum chamber at Marshall Space Flight Center. By anchoring analytical models against test data, higher fidelity thermal environment predictions can be made for future flight articles which would eventually demonstrate critical cryogenic fluid management technologies such as system chilldown, transfer, pressure control and long term storage. Significant factors that influenced heat loads included radiative environments, multi-layer insulation performance, tank fill levels and pressures and even contact conductance coefficients. This report demonstrates how analytical thermal/fluid networks were established and includes supporting rationale for specific thermal responses.

CRYOGENIC AND VACUUM TECHNOLOGICAL ASPECTS OF THE LOW-ENERGY ELECTROSTATIC CRYOGENIC STORAGE RING

International Nuclear Information System (INIS)

Orlov, D. A.; Lange, M.; Froese, M.; Hahn, R. von; Grieser, M.; Mallinger, V.; Sieber, T.; Weber, T.; Wolf, A.; Rappaport, M.

2008-01-01

The cryogenic and vacuum concepts for the electrostatic Cryogenic ion Storage Ring (CSR), under construction at the Max-Planck-Institut fuer Kernphysik in Heidelberg, is presented. The ring will operate in a broad temperature range from 2 to 300 K and is required to be bakeable up to 600 K. Extremely high vacuum and low temperatures are necessary to achieve long lifetimes of the molecular ions stored in the ring so that the ions will have enough time to cool by radiation to their vibrational and rotational ground states. To test cryogenic and vacuum technological aspects of the CSR, a prototype is being built and will be connected to the commercial cryogenic refrigerator recently installed, including a specialized 2-K connection system. The first results and the status of current work with the prototype are also presented

StructUre and test results of the Tokamak-7 device cryogenic system

International Nuclear Information System (INIS)

Babaev, I.V.; VolobUev, A.N.; Zhul'kin, V.F.

1982-01-01

A cryogenic system (CS) of the Tokamak-7 (T-7) installation with the longitudinal field superconducting magnetic system (SMS) is described. The CS is designed for cool-down, cryostatic cooling and heating of the T-7 cryogenic objects and consists of a helium system (HS) and a nitrogen cryogenic system (NCS). The HS consists of:a a heliUm delivery system intended for distributing and controlling the helium flows in the SMS; cryogenic helium units; a 1.25 m 3 volume for storing liquid helium; a compressor compartment using piston compressors at the 3 MPa operating pressure and 140 g/s total capacity; gaseous helium storages (3600 m 3 under normal conditions); helium cleaning and drying systems; a gas holder of 20 m 3 operating volume; cryogenic pipelines and pipe fittings. The NCS operates on delivered nitrogen and includes a 120 m 3 liquid nitrogen storage, evaporators and electric heaters producing up to 230 g/s of gaseous nitrogen at 300 K, a separator, cryogenic pipelines and fittings. It is found that the CS has the necessary cold production reserve, ensures reliable operation of the Tokamak-7 device and permits to carry out practically continuous plasma experiments

Hyperbolic strings

International Nuclear Information System (INIS)

Popov, A.D.

1991-01-01

We introduce hyperbolic strings as closed bosonic strings with the target space R d-1,1 xT q+1,1 which has an additional time-like dimension in the internal space. The Fock spaces of the q-parametric family of standard bosonic, fermionic and heterotic strings with the target spaces of dimension n≤d+q are shown to be embedded into the Fock space of hyperbolic strings. The condition of the absence of anomaly fixes d and q for all three types of strings written in a bosonized form. (orig.)

String phenomenology

CERN Document Server

Ibáñez, Luis E

2015-01-01

This chapter reviews a number of topics in the field of string phenomenology, focusing on orientifold/F-theory models yielding semirealistic low-energy physics. The emphasis is on the extraction of the low-energy effective action and possible tests of specific models at the LHC.

String theory

International Nuclear Information System (INIS)

Chan Hongmo.

1987-10-01

The paper traces the development of the String Theory, and was presented at Professor Sir Rudolf Peierls' 80sup(th) Birthday Symposium. The String theory is discussed with respect to the interaction of strings, the inclusion of both gauge theory and gravitation, inconsistencies in the theory, and the role of space-time. The physical principles underlying string theory are also outlined. (U.K.)

Duality relation between charged elastic strings and superconducting cosmic strings

International Nuclear Information System (INIS)

Carter, B.

1989-01-01

The mechanical properties of macroscopic electromagnetically coupled string models in a flat or curved background are treated using a covariant formalism allowing the construction of a duality transformation that relates the category of uniform ''electric'' string models, constructed as the (nonconducting) charged generalisation of ordinary uncoupled (violin type) elastic strings, to a category of ''magnetic'' string models comprising recently discussed varieties of ''superconducting cosmic strings''. (orig.)

Liquid Transfer Cryogenic Test Facility: Initial hydrogen and nitrogen no-vent fill data

Science.gov (United States)

Moran, Matthew E.; Nyland, Ted W.; Papell, S. Stephen

1990-01-01

The Liquid Transfer Cryogenic Test Facility is a versatile testbed for ground-based cryogenic fluid storage, handling, and transfer experimentation. The test rig contains two well instrumented tanks, and a third interchangeable tank, designed to accommodate liquid nitrogen or liquid hydrogen testing. The internal tank volumes are approx. 18, 5, and 1.2 cu. ft. Tank pressures can be varied from 2 to 30 psia. Preliminary no vent fill tests with nitrogen and hydrogen were successfully completed with the test rig. Initial results indicate that no vent fills of nitrogen above 90 percent full are achievable using this test configuration, in a 1-g environment, and with inlet liquid temperatures as high as 143 R, and an average tank wall temperature of nearly 300 R. This inlet temperature corresponds to a saturation pressure of 19 psia for nitrogen. Hydrogen proved considerably more difficult to transfer between tanks without venting. The highest temperature conditions resulting in a fill level greater than 90 percent were with an inlet liquid temperature of 34 R, and an estimated tank wall temperature of slightly more than 100 R. Saturation pressure for hydrogen at this inlet temperature is 10 psia. All preliminary no vent fill tests were performed with a top mounted full cone nozzle for liquid injection. The nozzle produces a 120 degree conical droplet spray at a differential pressure of 10 psi. Pressure in the receiving tank was held to less than 30 psia for all tests.

A reduced covariant string model for the extrinsic string

International Nuclear Information System (INIS)

Botelho, L.C.L.

1989-01-01

It is studied a reduced covariant string model for the extrinsic string by using Polyakov's path integral formalism. On the basis of this reduced model it is suggested that the extrinsic string has its critical dimension given by 13. Additionally, it is calculated in a simple way Poliakov's renormalization group law for the string rigidity coupling constants. (A.C.A.S.) [pt

Spiral 2 cryogenic system overview: Design, construction and performance test

Energy Technology Data Exchange (ETDEWEB)

Deschildre, C.; Bernhardt, J.; Flavien, G.; Crispel, S. [Air Liquide Advanced Technologies, Sassenage (France); Souli, M. [GANIL, Caen (France); Commeaux, C. [IPN, Orsay (France)

2014-01-29

The new particle accelerator project Spiral 2 at GANIL (“Grand Accélérateur d’Ions Lourds, i.e. National Large Heavy Ion Accelerator) in Caen (France) is a very large installation, intended to serve fundamental research in nuclear physics. The heart of the future machine features a superconductor linear accelerator, delivering a beam until 20Mev/A, which are then used to bombard a matter target. The resulting reactions, such as fission, transfer, fusion, etc. will generate billions of exotic nuclei. To achieve acceleration of the beam, 26 cavities which are placed inside cryomodules at helium cryogenic temperature will be used. AL-AT (Air Liquide Advanced Technologies) takes part to the project by supplying cryogenic plant. The plant includes the liquefier associated to its compressor station, a large dewar, a storage tank for helium gas and transfer lines. In addition, a helium recovery system composed of recovery compressor, high pressure storage and external purifier has been supplied. Customized HELIAL LF has been designed, manufactured and tested by AL-AT to match the refrigeration power need for the Spiral 2 project which is around 1300 W equivalent at 4.5 K.

Cryogenic test of the equivalence principle

International Nuclear Information System (INIS)

Worden, P.W. Jr.

1976-01-01

The weak equivalence principle is the hypothesis that the ratio of internal and passive gravitational mass is the same for all bodies. A greatly improved test of this principle is possible in an orbiting satellite. The most promising experiments for an orbital test are adaptations of the Galilean free-fall experiment and the Eotvos balance. Sensitivity to gravity gradient noise, both from the earth and from the spacecraft, defines a limit to the sensitivity in each case. This limit is generally much worse for an Eotvos balance than for a properly designed free-fall experiment. The difference is related to the difficulty of making a balance sufficiently isoinertial. Cryogenic technology is desirable to take full advantage of the potential sensitivity, but tides in the liquid helium refrigerant may produce a gravity gradient that seriously degrades the ultimate sensitivity. The Eotvos balance appears to have a limiting sensitivity to relative difference of rate of fall of about 2 x 10 -14 in orbit. The free-fall experiment is limited by helium tide to about 10 -15 ; if the tide can be controlled or eliminated the limit may approach 10 -18 . Other limitations to equivalence principle experiments are discussed. An experimental test of some of the concepts involved in the orbital free-fall experiment is continuing. The experiment consists in comparing the motions of test masses levitated in a superconducting magnetic bearing, and is itself a sensitive test of the equivalence principle. At present the levitation magnets, position monitors and control coils have been tested and major noise sources identified. A measurement of the equivalence principle is postponed pending development of a system for digitizing data. The experiment and preliminary results are described

The heterotic string

International Nuclear Information System (INIS)

Gross, D.J.

1986-01-01

Traditional string theories, either bosonic or supersymmetric, came in two varieties, closed string theories and open string theories. Closed string are neutral objects which describe at low energies gravity or supergravity. Open strings have geometrically invariant ends to which charge can be attached, thereby obtaining, in addition to gravity, Yang-Mills gauge interactions. Recently a new kind of string theory was discovered--the heterotic string, which is a chiral hybrid of the closed superstring and the closed bosonic string, and which produces by an internal dynamical mechanism gauge interactions of a totally specified kind. Although this theory is found in an attempt to produce a superstring theory which would yield a low energy E/sub 8/xE/sub 8/ supersymmetric, anomaly free, gauge theory, as suggested by the anomaly cancellation mechanism of Green and Schwarz, it fits naturally into the general framework of consistent string theories

A coil test facility for the cryogenic tests of the JT-60SA TF coils

International Nuclear Information System (INIS)

Chantant, M.; Genini, L.; Bayetti, P.; Millet, F.; Wanner, M.; Massaut, V.; Corte, A. Della; Ardelier-Desage, F.; Catherine-Dumont, V.; Dael, A.; Decool, P.; Donati, A.; Duchateau, J.L.; Garibaldi, P.; Girard, S.; Hatchressian, J.C.; Fejoz, P.; Jamotton, P.; Jourdheuil, L.; Juster, F.P.

2011-01-01

In the framework of the Broader Approach Activities, the EU will deliver to Japan the 18 superconducting coils, which constitute the JT-60SA Toroidal field magnet. These 18 coils, manufactured by France and Italy, will be cold tested before shipping to Japan. For this purpose, the European Joint Undertaking for ITER, the Development of Fusion Energy ('Fusion for Energy', F4E) and the European Voluntary Contributors are collaborating to design and set-up a coil test facility (CTF) and to perform the acceptance test of the 18 JT-60SA Toroidal Field (TF) coils. The test facility is designed to test one coil at a time at nominal current and cryogenic temperature. The test of the first coil of each manufacturer includes a quench triggered by increasing the temperature. The project is presently in the detailed design phase.

Cylindrical cryogenic calorimeter testing of six types of multilayer insulation systems

Science.gov (United States)

Fesmire, J. E.; Johnson, W. L.

2018-01-01

Extensive cryogenic thermal testing of more than 100 different multilayer insulation (MLI) specimens was performed over the last 20 years for the research and development of evacuated reflective thermal insulation systems. From this data library, 26 MLI systems plus several vacuum-only systems are selected for analysis and comparison. The test apparatus, methods, and results enabled the adoption of two new technical consensus standards under ASTM International. Materials tested include reflectors of aluminum foil or double-aluminized Mylar and spacers of fiberglass paper, polyester netting, silk netting, polyester fabric, or discrete polymer standoffs. The six types of MLI systems tested are listed as follows: Mylar/Paper, Foil/Paper, Mylar/Net, Mylar/Blanket, Mylar/Fabric, Mylar/Discrete. Also tested are vacuum-only systems with different cold surface materials/finishes including stainless steel, black, copper, and aluminum. Testing was performed between the boundary temperatures of 78 K and 293 K (and up to 350 K) using a thermally guarded one-meter-long cylindrical calorimeter (Cryostat-100) for absolute heat flow measurement. Cold vacuum pressures include the full range from 1 × 10-6 torr to 760 torr with nitrogen as the residual gas. System variations include number of layers from one to 80 layers, layer densities from 0.5 to 5 layers per millimeter, and installation techniques such layer-by-layer, blankets (multi-layer assemblies), sub-blankets, seaming, butt-joining, spiral wrapping, and roll-wrapping. Experimental thermal performance data for the different MLI systems are presented in terms of heat flux and effective thermal conductivity. Benchmark cryogenic-vacuum thermal performance curves for MLI are given for comparison with different insulation approaches for storage and transfer equipment, cryostats, launch vehicles, spacecraft, or science instruments.

String Gas Cosmology

OpenAIRE

Brandenberger, Robert H.

2008-01-01

String gas cosmology is a string theory-based approach to early universe cosmology which is based on making use of robust features of string theory such as the existence of new states and new symmetries. A first goal of string gas cosmology is to understand how string theory can effect the earliest moments of cosmology before the effective field theory approach which underlies standard and inflationary cosmology becomes valid. String gas cosmology may also provide an alternative to the curren...

Development of bonding techniques for cryogenic components. 1. HIP bonding tests between Ti and cryogenic stainless steels

International Nuclear Information System (INIS)

Saito, Shigeru; Ouchi, Nobuo; Ishiyama, Shintaro; Tsuchiya, Yoshinori; Nakajima, Hideo

2002-05-01

Around the super conducting (SC) coils of SC linear accelerator or fusion reactor, several kinds of dissimilar material joints will be needed. In case of fusion reactor, pure titanium has been proposed as jacket material of SC coil. Pure titanium has many advantages, for instance, almost same thermal expansion with Nb 3 Sn SC coil, non-magnetivity and good workability. However, it is difficult to bond Ti and cryogenic stainless steels by welding. Therefore, it is necessary to develop new bonding techniques and we started the development of the bonding technology by hot isostatic press (HIP) method to bond titanium with stainless steels. In this experiments, optimization of HIP bonding condition and evaluation of bonding strength were performed by metallurgical observation, mechanical property tests and heat cycle test. (author)

Chern-Simons couplings for dielectric F-strings in matrix string theory

International Nuclear Information System (INIS)

Brecher, Dominic; Janssen, Bert; Lozano, Yolanda

2002-01-01

We compute the non-abelian couplings in the Chern-Simons action for a set of coinciding fundamental strings in both the type IIA and type IIB Matrix string theories. Starting from Matrix theory in a weakly curved background, we construct the linear couplings of closed string fields to type IIA Matrix strings. Further dualities give a type IIB Matrix string theory and a type IIA theory of Matrix strings with winding. (Abstract Copyright[2002], Wiley Periodicals, Inc.)

Innovative Ultra-High Efficiency Cryogenic Actuators for Rocket Test Facilities, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — The SBIR Phase I project will develop advanced ultra-high efficiency cryogenic actuators for NASA cryogenic fluid transfer application. The actuator will have low...

A string theory which isn't about strings

Science.gov (United States)

Lee, Kanghoon; Rey, Soo-Jong; Rosabal, J. A.

2017-11-01

Quantization of closed string proceeds with a suitable choice of worldsheet vacuum. A priori, the vacuum may be chosen independently for left-moving and right-moving sectors. We construct ab initio quantized bosonic string theory with left-right asymmetric worldsheet vacuum and explore its consequences and implications. We critically examine the validity of new vacuum and carry out first-quantization using standard operator formalism. Remarkably, the string spectrum consists only of a finite number of degrees of freedom: string gravity (massless spin-two, Kalb-Ramond and dilaton fields) and two massive spin-two Fierz-Pauli fields. The massive spin-two fields have negative norm, opposite mass-squared, and provides a Lee-Wick type extension of string gravity. We compute two physical observables: tree-level scattering amplitudes and one-loop cosmological constant. Scattering amplitude of four dilatons is shown to be a rational function of kinematic invariants, and in D = 26 factorizes into contributions of massless spin-two and a pair of massive spin-two fields. The string one loop partition function is shown to perfectly agree with one loop Feynman diagram of string gravity and two massive spin-two fields. In particular, it does not exhibit modular invariance. We critically compare our construction with recent studies and contrast differences.

Cryogenic Insulation Standard Data and Methodologies Project

Science.gov (United States)

Summerfield, Burton; Thompson, Karen; Zeitlin, Nancy; Mullenix, Pamela; Fesmire, James; Swanger, Adam

2015-01-01

Extending some recent developments in the area of technical consensus standards for cryogenic thermal insulation systems, a preliminary Inter-Laboratory Study of foam insulation materials was performed by NASA Kennedy Space Center and LeTourneau University. The initial focus was ambient pressure cryogenic boil off testing using the Cryostat-400 flat-plate instrument. Completion of a test facility at LETU has enabled direct, comparative testing, using identical cryostat instruments and methods, and the production of standard thermal data sets for a number of materials under sub-ambient conditions. The two sets of measurements were analyzed and indicate there is reasonable agreement between the two laboratories. Based on cryogenic boiloff calorimetry, new equipment and methods for testing thermal insulation systems have been successfully developed. These boiloff instruments (or cryostats) include both flat plate and cylindrical models and are applicable to a wide range of different materials under a wide range of test conditions. Test measurements are generally made at large temperature difference (boundary temperatures of 293 K and 78 K are typical) and include the full vacuum pressure range. Results are generally reported in effective thermal conductivity (ke) and mean heat flux (q) through the insulation system. The new cryostat instruments provide an effective and reliable way to characterize the thermal performance of materials under subambient conditions. Proven in through thousands of tests of hundreds of material systems, they have supported a wide range of aerospace, industry, and research projects. Boiloff testing technology is not just for cryogenic testing but is a cost effective, field-representative methodology to test any material or system for applications at sub-ambient temperatures. This technology, when adequately coupled with a technical standards basis, can provide a cost-effective, field-representative methodology to test any material or system

Cryogenics for LHC experiments

CERN Multimedia

2001-01-01

Cryogenic systems will be used by LHC experiments to maximize their performance. Institutes around the world are collaborating with CERN in the construction of these very low temperature systems. The cryogenic test facility in hall 180 for ATLAS magnets. High Energy Physics experiments have frequently adopted cryogenic versions of their apparatus to achieve optimal performance, and those for the LHC will be no exception. The two largest experiments for CERN's new flagship accelerator, ATLAS and CMS, will both use large superconducting magnets operated at 4.5 Kelvin - almost 270 degrees below the freezing point of water. ATLAS also includes calorimeters filled with liquid argon at 87 Kelvin. For the magnets, the choice of a cryogenic version was dictated by a combination economy and transparency to emerging particles. For the calorimeters, liquid argon was selected as the fluid best suited to the experiment's physics requirements. High Energy Physics experiments are the result of worldwide collaborations and...

Commissioning of cryogenic system for China Spallation Neutron Source

Science.gov (United States)

Ye, Bin; He, Chongchao; Li, Na; Ding, Meiying; Wang, Yaqiong; Yu, Zhang; He, Kun

2017-12-01

China Spallation Neutron Source(CSNS) cryogenic system provides supercritical cryogenic hydrogen to neutron moderators, including a helium refrigerator, hydrogen loop and hydrogen safety equipment. The helium refrigerator is provided by Linde with cooling capacity of 2200 W at 20 K. Hydrogen loop system mainly includes cryogenic hydrogen pipes, hydrogen circulator cold-box and accumulator cold-box. Cryogenic hydrogen pump, ortho-para convertor, helium-hydrogen heat-exchanger, hydrogen heater and accumulator are integrated in hydrogen circulation cold-box, and accumulator cold-box. Hydrogen safety equipment includes safety valves, rupture disk, hydrogen sensor, flame detector and other equipment to ensure that cryogenic system in dangerous situations will go down, vents, or takes other measures. The cryogenic system commissioning work includes four steps. First, in order to test the refrigerating capacity of refrigerator, when acceptance testing, refrigerator internal heater was used as thermal load. Second, using simulation load as heat load of moderator, hydrogen loop use helium instead of hydrogen, and cooled down to 20 K, then re-warming and test the leak detection of hydrogen loop system. Third, base on the step 2, using hydrogen as working medium, and optimized the control logic. Forth, cryogenic system with the moderators joint commissioning. Now, cryogenic system is connected with the moderators, and the forth step will be carried out in the near future.

Design of a cryogenic test facility for evaluating the performance of interferometric components of the SPICA/SAFARI instrument

Science.gov (United States)

Veenendaal, Ian T.; Naylor, David A.; Gom, Brad G.

2014-08-01

The Japanese SPace Infrared telescope for Cosmology and Astrophysics (SPICA), a 3 m class telescope cooled to ~ 6 K, will provide extremely low thermal background far-infrared observations. An imaging Fourier transform spectrometer (SAFARI) is being developed to exploit the low background provided by SPICA. Evaluating the performance of the interferometer translation stage and key optical components requires a cryogenic test facility. In this paper we discuss the design challenges of a pulse tube cooled cryogenic test facility that is under development for this purpose. We present the design of the cryostat and preliminary results from component characterization and external optical metrology.

Cryogenics Testbed Laboratory Flange Baseline Configuration

Science.gov (United States)

Acuna, Marie Lei Ysabel D.

2013-01-01

As an intern at Kennedy Space Center (KSC), I was involved in research for the Fluids and Propulsion Division of the NASA Engineering (NE) Directorate. I was immersed in the Integrated Ground Operations Demonstration Units (IGODU) project for the majority of my time at KSC, primarily with the Ground Operations Demonstration Unit Liquid Oxygen (GODU L02) branch of IGODU. This project was established to develop advancements in cryogenic systems as a part of KSC's Advanced Exploration Systems (AES) program. The vision of AES is to develop new approaches for human exploration, and operations in and beyond low Earth orbit. Advanced cryogenic systems are crucial to minimize the consumable losses of cryogenic propellants, develop higher performance launch vehicles, and decrease operations cost for future launch programs. During my internship, I conducted a flange torque tracking study that established a baseline configuration for the flanges in the Simulated Propellant Loading System (SPLS) at the KSC Cryogenics Test Laboratory (CTL) - the testing environment for GODU L02.

Unified model for vortex-string network evolution

International Nuclear Information System (INIS)

Martins, C.J.A.P.; Moore, J.N.; Shellard, E.P.S.

2004-01-01

We describe and numerically test the velocity-dependent one-scale string evolution model, a simple analytic approach describing a string network with the averaged correlation length and velocity. We show that it accurately reproduces the large-scale behavior (in particular the scaling laws) of numerical simulations of both Goto-Nambu and field theory string networks. We explicitly demonstrate the relation between the high-energy physics approach and the damped and nonrelativistic limits which are relevant for condensed matter physics. We also reproduce experimental results in this context and show that the vortex-string density is significantly reduced by loop production, an effect not included in the usual 'coarse-grained' approach

Vortex-strings in N=2 SQCD and bulk-string decoupling

Science.gov (United States)

Gerchkovitz, Efrat; Karasik, Avner

2018-02-01

We study vortex-strings in four-dimensional N=2 supersymmetric SU( N c ) × U(1) gauge theories with N f hypermultiplets in the fundamental representation of SU( N c ) and general U(1) charges. If N f > N c , the vacuum is not gapped and the low-energy theory contains both the vacuum massless excitations and the string zero-modes. The question we address in this work is whether the vacuum and the string moduli decouple at low energies, allowing a description of the low-energy dynamics in terms of a two-dimensional theory on the string worldsheet. We find a simple condition controlling the bulk-string coupling: if there exist two flavors such that the product of their U(1) charge difference with the magnetic flux carried by the string configuration is not an integer multiple of 2 π, the string has zero-modes that decay slower than 1 /r, where r is the radial distance from the string core. These modes are coupled to the vacuum massless excitations even at low energies. If, however, all such products are integer multiples of 2 π, long-range modes of this type do not exist and the string moduli decouple from the bulk at low energies. This condition turns out to coincide with the condition of trivial Aharonov-Bohm phases for the particles in the spectrum. In addition to a derivation of the bulk-string decoupling criterion using classical analysis of the string zero-modes, we provide a non-perturbative derivation of the criterion, which uses supersymmetric localization techniques.

StringForce

DEFF Research Database (Denmark)

Barendregt, Wolmet; Börjesson, Peter; Eriksson, Eva

2017-01-01

In this paper, we present the forced collaborative interaction game StringForce. StringForce is developed for a special education context to support training of collaboration skills, using readily available technologies and avoiding the creation of a "mobile bubble". In order to play String......Force two or four physically collocated tablets are required. These tablets are connected to form one large shared game area. The game can only be played by collaborating. StringForce extends previous work, both technologically and regarding social-emotional training. We believe String......Force to be an interesting demo for the IDC community, as it intertwines several relevant research fields, such as mobile interaction and collaborative gaming in the special education context....

Bosonic strings

CERN Document Server

Jost, Jürgen

2007-01-01

This book presents a mathematical treatment of Bosonic string theory from the point of view of global geometry. As motivation, Jost presents the theory of point particles and Feynman path integrals. He provides detailed background material, including the geometry of Teichmüller space, the conformal and complex geometry of Riemann surfaces, and the subtleties of boundary regularity questions. The high point is the description of the partition function for Bosonic strings as a finite-dimensional integral over a moduli space of Riemann surfaces. Jost concludes with some topics related to open and closed strings and D-branes. Bosonic Strings is suitable for graduate students and researchers interested in the mathematics underlying string theory.

String cosmology. Large-field inflation in string theory

International Nuclear Information System (INIS)

Westphal, Alexander

2014-09-01

This is a short review of string cosmology. We wish to connect string-scale physics as closely as possible to observables accessible to current or near-future experiments. Our possible best hope to do so is a description of inflation in string theory. The energy scale of inflation can be as high as that of Grand Unification (GUT). If this is the case, this is the closest we can possibly get in energy scales to string-scale physics. Hence, GUT-scale inflation may be our best candidate phenomenon to preserve traces of string-scale dynamics. Our chance to look for such traces is the primordial gravitational wave, or tensor mode signal produced during inflation. For GUT-scale inflation this is strong enough to be potentially visible as a B-mode polarization of the cosmic microwave background (CMB). Moreover, a GUT-scale inflation model has a trans-Planckian excursion of the inflaton scalar field during the observable amount of inflation. Such large-field models of inflation have a clear need for symmetry protection against quantum corrections. This makes them ideal candidates for a description in a candidate fundamental theory like string theory. At the same time the need of large-field inflation models for UV completion makes them particularly susceptible to preserve imprints of their string-scale dynamics in the inflationary observables, the spectral index n s and the fractional tensor mode power r. Hence, we focus this review on axion monodromy inflation as a mechanism of large-field inflation in string theory.

Boundary string field theory and an open string one-loop

International Nuclear Information System (INIS)

Lee, Tae Jin; Viswanathan, K. S.; Yang, Yi

2003-01-01

We discuss the open string one-loop partition function in the tachyon condensation background of an unstable D-brane system. We evaluate the partition function by using the boundary-state formulation and find that it is in complete agreement with the result obtained in the boundary string field theory. This suggests that the open string higher loop diagrams may be produced consistently by using a closed string field theory, where the D-brane plays the role of a source for the closed string field

Tests of industrial ethylene-propylene rubber high voltage cable for cryogenic use

CERN Document Server

Balhan, B; Goddard, B; Muratori, G; Otwinowski, S; Rieubland, Jean Michel; Wang, H; CERN. Geneva. SPS and LEP Division

1999-01-01

At the beginning of 1999 UCLA has received a prototype High Voltage Cryogenic Cable supplied fee of charge by Pirelli. The cable is intended for more than ten years of service at 100 kV D.C. and liquid argon temperature. Thecable uses an all welded construction, whichi is axially tight and free of ionizable voids. The cable was submitted to a number of mechanical and electrical tests as described below.

Hot String Soup

OpenAIRE

Lowe, D. A.; Thorlacius, L.

1994-01-01

Above the Hagedorn energy density closed fundamental strings form a long string phase. The dynamics of weakly interacting long strings is described by a simple Boltzmann equation which can be solved explicitly for equilibrium distributions. The average total number of long strings grows logarithmically with total energy in the microcanonical ensemble. This is consistent with calculations of the free single string density of states provided the thermodynamic limit is carefully defined. If the ...

String-driven inflation

International Nuclear Information System (INIS)

Turok, N.

1988-01-01

It is argued that, in fundamental string theories, as one traces the universe back in time a point is reached when the expansion rate is so fast that the rate of string creation due to quantum effects balances the dilution of the string density due to the expansion. One is therefore led into a phase of constant string density and an exponentially expanding universe. Fundamental strings therefore seem to lead naturally to inflation

Cosmic global strings

International Nuclear Information System (INIS)

Sikivie, P.

1991-01-01

The topics are: global strings; the gravitational field of a straight global string; how do global strings behave?; the axion cosmological energy density; computer simulations of the motion and decay of global strings; electromagnetic radiation from the conversion of Nambu-Goldstone bosons in astrophysical magnetic fields. (orig.)

Long-term cryogenic space storage system

Science.gov (United States)

Hopkins, R. A.; Chronic, W. L.

1973-01-01

Discussion of the design, fabrication and testing of a 225-cu ft spherical cryogenic storage system for long-term subcritical applications under zero-g conditions in storing subcritical cryogens for space vehicle propulsion systems. The insulation system design, the analytical methods used, and the correlation between the performance test results and analytical predictions are described. The best available multilayer insulation materials and state-of-the-art thermal protection concepts were applied in the design, providing a boiloff rate of 0.152 lb/hr, or 0.032% per day, and an overall heat flux of 0.066 Btu/sq ft hr based on a 200 sq ft surface area. A six to eighteen month cryogenic storage is provided by this system for space applications.

String driven inflation

International Nuclear Information System (INIS)

Turok, N.

1987-11-01

It is argued that, in fundamental string theories, as one traces the universe back in time a point is reached when the expansion rate is so fast that the rate of string creation due to quantum effects balances the dilution of the string density due to the expansion. One is therefore led into a phase of constant string density and an exponentially expanding universe. Fundamental strings therefore seem to lead naturally to inflation. 17 refs., 1 fig

Cryogenic rf test of the first SRF cavity etched in an rf Ar/Cl2 plasma

Science.gov (United States)

Upadhyay, J.; Palczewski, A.; Popović, S.; Valente-Feliciano, A.-M.; Im, Do; Phillips, H. L.; Vušković, L.

2017-12-01

An apparatus and a method for etching of the inner surfaces of superconducting radio frequency (SRF) accelerator cavities are described. The apparatus is based on the reactive ion etching performed in an Ar/Cl2 cylindrical capacitive discharge with reversed asymmetry. To test the effect of the plasma etching on the cavity rf performance, a 1497 MHz single cell SRF cavity was used. The single cell cavity was mechanically polished and buffer chemically etched and then rf tested at cryogenic temperatures to provide a baseline characterization. The cavity's inner wall was then exposed to the capacitive discharge in a mixture of Argon and Chlorine. The inner wall acted as the grounded electrode, while kept at elevated temperature. The processing was accomplished by axially moving the dc-biased, corrugated inner electrode and the gas flow inlet in a step-wise manner to establish a sequence of longitudinally segmented discharges. The cavity was then tested in a standard vertical test stand at cryogenic temperatures. The rf tests and surface condition results, including the electron field emission elimination, are presented.

Cryogenic rf test of the first SRF cavity etched in an rf Ar/Cl2 plasma

Directory of Open Access Journals (Sweden)

J. Upadhyay

2017-12-01

Full Text Available An apparatus and a method for etching of the inner surfaces of superconducting radio frequency (SRF accelerator cavities are described. The apparatus is based on the reactive ion etching performed in an Ar/Cl2 cylindrical capacitive discharge with reversed asymmetry. To test the effect of the plasma etching on the cavity rf performance, a 1497 MHz single cell SRF cavity was used. The single cell cavity was mechanically polished and buffer chemically etched and then rf tested at cryogenic temperatures to provide a baseline characterization. The cavity’s inner wall was then exposed to the capacitive discharge in a mixture of Argon and Chlorine. The inner wall acted as the grounded electrode, while kept at elevated temperature. The processing was accomplished by axially moving the dc-biased, corrugated inner electrode and the gas flow inlet in a step-wise manner to establish a sequence of longitudinally segmented discharges. The cavity was then tested in a standard vertical test stand at cryogenic temperatures. The rf tests and surface condition results, including the electron field emission elimination, are presented.

Cryogenics

International Nuclear Information System (INIS)

Fradkov, A.B.

1991-01-01

The application of cryogenics in various areas of science and technology is related in a popular way. Utilization of cryogenics in the following production processes is described: separation of air, gas mixtures; production of helium; separation of hydrogen isotopes; production of deuterium. Applications of cryogenics in refrigerating engineering, superconductivity and high-energy physics, controlled thermonuclear fusion, superconducting electric motors and electric energy storages are considered

FaceSheet Push-off Tests to Determine Composite Sandwich Toughness at Cryogenic Temperatures

Science.gov (United States)

Gates, Thomas S.; Herring, Helen M.

2001-01-01

A new novel test method, associated analysis, and experimental procedures are developed to investigate the toughness of the facesheet-to-core interface of a sandwich material at cryogenic temperatures. The test method is designed to simulate the failure mode associated with facesheet debonding from high levels of gas pressure in the sandwich core. The effects of specimen orientation are considered, and the results of toughness measurements are presented. Comparisons are made between room and liquid nitrogen (-196 C) test temperatures. It was determined that the test method is insensitive to specimen facesheet orientation and strain energy release rate increases with a decrease in the test temperature.

In-Space Cryogenic VOST Connect/Disconnect, Phase II

Data.gov (United States)

National Aeronautics and Space Administration — Two novel cryogenic couplings will be designed, fabricated and tested. Intended for in-space use at cryogenic propellant depots, the couplings are based on patented...

Cryogenics a textbook

CERN Document Server

Thipse, S S

2013-01-01

A Textbook covers lucidly various cryogenic applications including cryogenic engines and space and electronic applications. Importance of cryogenic engines in space propulsion, complete thermodynamic analysis of cryogenic systems with special emphasis on cryogenic cycles, Dewar vessels used to store cryogenic fluids and their applications in various industries have also been discussed in detail. Explanation of Superconductivity and its applications with a description of various Cryocoolers used in industry has also been provided with extensive details. Further technical information on cryogens has been specified alongwith the vacuum technology which has been sufficiently described with examples. Science of Cryonics has been elaborated and all aspects of technology related to functioning of cryogenic plants and their construction including valves, pipes has been incorporated in this book.

String field theory solution for any open string background

Czech Academy of Sciences Publication Activity Database

Erler, T.; Maccaferri, Carlo

2014-01-01

Roč. 10, Oct (2014), 1-37 ISSN 1029-8479 R&D Projects: GA ČR GBP201/12/G028 Institutional support: RVO:68378271 Keywords : tachyon condensation * string field theory * conformal field models in string theory * bosonic strings Subject RIV: BE - Theoretical Physics Impact factor: 6.111, year: 2014

Lattice strings

International Nuclear Information System (INIS)

Thorn, C.B.

1988-01-01

The possibility of studying non-perturbative effects in string theory using a world sheet lattice is discussed. The light-cone lattice string model of Giles and Thorn is studied numerically to assess the accuracy of ''coarse lattice'' approximations. For free strings a 5 by 15 lattice seems sufficient to obtain better than 10% accuracy for the bosonic string tachyon mass squared. In addition a crude lattice model simulating string like interactions is studied to find out how easily a coarse lattice calculation can pick out effects such as bound states which would qualitatively alter the spectrum of the free theory. The role of the critical dimension in obtaining a finite continuum limit is discussed. Instead of the ''gaussian'' lattice model one could use one of the vertex models, whose continuum limit is the same as a gaussian model on a torus of any radius. Indeed, any critical 2 dimensional statistical system will have a stringy continuum limit in the absence of string interactions. 8 refs., 1 fig. , 9 tabs

String-coupling constant and dilaton vacuum expectation value in string field theory

International Nuclear Information System (INIS)

Yoneya, Tamiaki

1987-01-01

In the first quantized approaches to strings, it is well known that the string-coupling constant is determined by the vacuum expectation value of the dilaton field. This property, however, has never been demonstrated within the framework of string field theory. An explicit reparametrization of the string field associated with the shifts of the dilaton vacuum expectation value and the string-coupling constant is constructed exhibiting the above property in the light-cone field theory of the closed bosonic string. (orig.)

Closed string field theory

International Nuclear Information System (INIS)

Strominger, A.

1987-01-01

A gauge invariant cubic action describing bosonic closed string field theory is constructed. The gauge symmetries include local spacetime diffeomorphisms. The conventional closed string spectrum and trilinear couplings are reproduced after spontaneous symmetry breaking. The action S is constructed from the usual ''open string'' field of ghost number minus one half. It is given by the associator of the string field product which is non-vanishing because of associativity anomalies. S does not describe open string propagation because open string states associate and can thereby be shifted away. A field theory of closed and open strings can be obtained by adding to S the cubic open string action. (orig.)

Conformal techniques in string theory and string field theory

International Nuclear Information System (INIS)

Giddings, S.B.

1987-01-01

The application of some conformal and Riemann surface techniques to string theory and string field theory is described. First a brief review of Riemann surface techniques and of the Polyakov approach to string theory is presented. This is followed by a discussion of some features of string field theory and of its Feynman rules. Specifically, it is shown that the Feynman diagrams for Witten's string field theory respect modular invariance, and in particular give a triangulation of moduli space. The Polyakov formalism is then used to derive the Feynman rules that should follow from this theory upon gauge-fixing. It should also be possible to apply this derivation to deduce the Feynman rules for other gauge-fixed string field theories. Following this, Riemann surface techniques are turned to the problem of proving the equivalence of the Polyakov and light-cone formalisms. It is first shown that the light-cone diagrams triangulate moduli space. Then the Polyakov measure is worked out for these diagrams, and shown to equal that deduced from the light-cone gauge fixed formalism. Also presented is a short description of the comparison of physical states in the two formalisms. The equivalence of the two formalisms in particular constitutes a proof of the unitarity of the Polyakov framework for the closed bosonic string

On the elliptic genus of three E-strings and heterotic strings

International Nuclear Information System (INIS)

Cai, Wenhe; Huang, Min-xin; Sun, Kaiwen

2015-01-01

A precise formula for the elliptic genus of three E-strings is presented. The related refined free energy coincides with the result calculated from topological string on local half K3 Calabi-Yau threefold up to genus twelve. The elliptic genus of three heterotic strings computed from M9 domain walls matches with the result from orbifold formula to high orders. This confirms the n=3 case of the recent conjecture that n pairs of E-strings can recombine into n heterotic strings.

Cryogenic aspects of the mirror fusion test facility

International Nuclear Information System (INIS)

Sterbentz, W.H.; Nelson, R.L.

1979-01-01

This paper covers the design and construction of the MFTF cryogenic system and a description of the operating procedures throughout the many functional modes. The coils and the cryopanels for maintaining the high vacuum environment weigh 417,000 kg (920,000 lb) and must be cooled from room temperature to 4.5 k. The cryogenic system for MFTF consists of a closed-loop helium system with a 3000-W helium refrigerator that uses gas-bearing expansion turbines and oil-flooded screw compressors. In addition, liquid helium storage facilities have adequate capacity for standby operation, and a complete helium-purification plant is capable of processing 17 m 3 /min (600 scfm). An open-loop liquid nitrogen system (with provision for later addition of a nitrogen recondenser) provides the required refrigeration for the radiation shields that must be maintained at 85 K

Minimal open strings

International Nuclear Information System (INIS)

Hosomichi, Kazuo

2008-01-01

We study FZZT-branes and open string amplitudes in (p, q) minimal string theory. We focus on the simplest boundary changing operators in two-matrix models, and identify the corresponding operators in worldsheet theory through the comparison of amplitudes. Along the way, we find a novel linear relation among FZZT boundary states in minimal string theory. We also show that the boundary ground ring is realized on physical open string operators in a very simple manner, and discuss its use for perturbative computation of higher open string amplitudes.

Cryogenics safety

International Nuclear Information System (INIS)

Reider, R.

1977-01-01

The safety hazards associated with handling cryogenic fluids are discussed in detail. These hazards include pressure buildup when a cryogenic fluid is heated and becomes a gas, potential damage to body tissues due to surface contact, toxic risk from breathing air altered by cryogenic fluids, dangers of air solidification, and hazards of combustible cryogens such as liquified oxygen, hydrogen, or natural gas or of combustible mixtures. Safe operating procedures and emergency planning are described

Cryogenic systems for inertial fusion energy

International Nuclear Information System (INIS)

Chatain, D.; Perin, J.P.; Bonnay, P.; Bouleau, E.; Chichoux, M.; Communal, D.; Manzagol, J.; Viargues, F.; Brisset, D.; Lamaison, V.; Paquignon, G.

2008-01-01

The Low Temperatures Laboratory of CEA/Grenoble (France) is involved in the development of cryogenic systems for inertial fusion since a ten of years. A conceptual design for the cryogenic infrastructure of the Laser MegaJoule (LMJ) facility has been proposed. Several prototypes have been designed, built and tested like for example the 1500 bars cryo-compressor for the targets filling, the target positioner and the thermal shroud remover. The HIPER project will necessitate the development of such equipments. The main difference is that this time, the cryogenic targets are direct drive targets. The first phase of HIPER experiments is a single shot period. Based oil the experience gained the last years, not only by our laboratory but also by Omega and G.A teams, we could design the new HIPER equipments for this phase. Some experimental results obtained with the prototypes of the LMJ cryogenic system are given and a first conceptual design for the HIPER single shot cryogenic system is shown. (authors)

Cryogenic refrigeration. (Latest citations from the Aerospace database). Published Search

International Nuclear Information System (INIS)

1993-09-01

The bibliography contains citations concerning cryogenic refrigeration or cryocooling. Design, development, testing, and evaluation of cryogenic cooling systems are discussed. Design applications in spacecraft, magnet cooling, superconductors, liquid fuel storage, radioastronomy, and medicine are presented. Material properties at cryogenic temperatures and cryogenic rocket propellants are considered in separate bibliographies. (Contains 250 citations and includes a subject term index and title list.)

First Cryogenic Testing of the ATLAS Superconducting Prototype Magnets

CERN Document Server

Delruelle, N; Haug, F; Mayri, C; Orlic, J P; Passardi, Giorgio; Pirotte, O; ten Kate, H H J

2002-01-01

The superconducting magnet system of the ATLAS detector will consist of a central solenoid, two end-cap toroids and the barrel toroid made of eight coils (BT) symmetrically placed around the central axis of the detector. All these magnets will be individually tested in an experimental area prior to their final installation in the underground cavern of the LHC collider. A dedicated cryogenic test facility has been designed and built for this purpose. It mainly consists of a 1'200 W at 4.5 K refrigerator, a 10 kW liquid nitrogen pre-cooling unit, a cryostat housing liquid helium centrifugal pumps, a distribution valve box and transfer lines. Prior to the start of the series tests of the BT magnets, two model coils are used at this facility. The first one, the so-called B00 of comparatively small size, contains the three different types of superconductors used for the ATLAS magnets which are wound on a cylindrical mandrel. The second magnet, the B0, is a reduced model of basically identical design concept as the...

String necklaces and primordial black holes from type IIB strings

International Nuclear Information System (INIS)

Lake, Matthew; Thomas, Steve; Ward, John

2009-01-01

We consider a model of static cosmic string loops in type IIB string theory, where the strings wrap cycles within the internal space. The strings are not topologically stabilised, however the presence of a lifting potential traps the windings giving rise to kinky cycloops. We find that PBH formation occurs at early times in a small window, whilst at late times we observe the formation of dark matter relics in the scaling regime. This is in stark contrast to previous predictions based on field theoretic models. We also consider the PBH contribution to the mass density of the universe, and use the experimental data to impose bounds on the string theory parameters.

SEU tests performed on the digital communication system for LHC cryogenic instrumentation

International Nuclear Information System (INIS)

Casas-Cubillos, J.; Faccio, F.; Gomes, P.; Martin, M.A.; Rodriguez-Ruiz, M.A.

2002-01-01

The future LHC particle accelerator will use a large number of cryogenic sensors and actuators, most of which are located inside the machine tunnel and therefore in a radiation environment. These elements will communicate through a fieldbus. This paper reports the irradiation study carried out on WorldFIP fieldbus communication system. A digital communication system based on WorldFIP fieldbus protocol has been implemented and single event effects and total ionizing dose radiation tests have been performed on it

Coulomb string tension, asymptotic string tension, and the gluon chain

OpenAIRE

Greensite, Jeff; Szczepaniak, Adam P.

2014-01-01

We compute, via numerical simulations, the non-perturbative Coulomb potential of pure SU(3) gauge theory in Coulomb gauge. We find that that the Coulomb potential scales nicely in accordance with asymptotic freedom, that the Coulomb potential is linear in the infrared, and that the Coulomb string tension is about four times larger than the asymptotic string tension. We explain how it is possible that the asymptotic string tension can be lower than the Coulomb string tension by a factor of four.

Cryogenics

International Nuclear Information System (INIS)

Shukla, R.K.

1990-01-01

Cryogenics refers to the coldest area known in nature. This temperature range has an upper limit arbitrarily defined as -100 degrees C (-250 degrees C by some) and a lower limit of absolute zero. These limits separate it from the temperature range generally used in refrigerating engineering. One important application of cryogenics is the separation ad purification of air into its various components (oxygen, nitrogen, argon, and the rare gases). Other important developments have been the large-scale production of liquid hydrogen; helium extraction from natural gas; storage and transport of liquefied gases such as oxygen, argon, nitrogen, helium, neon, xenon, and hydrogen; liquefaction of natural gas for ocean transport and peak shaving; and many new types of cryogenic refrigeration devices. This paper introduces the topic of cryogenic engineering. Cryogenic processes generally range from ambient conditions to the boiling point of the cryogenic fluid. Cryogenic cycles also incorporate two or more pressure levels. These properties must also cover the vapor, vapor-liquid, and sometimes the solid regions. Therefore, the physical properties of fluids over a great range of temperatures and pressures must be known. Solubility of contaminants must be known in order to design for their removal. The main physical properties for design purposes are those usually used in unit operations, such as fluid flow, heat transfer, and the like, in addition to those directly related to the Joule-Thomson effect and expansion work. Properties such as density, viscosity, thermal conductivity, heat capacity, enthalpy, entropy, vapor pressure, and vapor-liquid equilibriums are generally obtained in graphical, tabular, or equation form, as a function of temperature and pressure

Helium cryogenics

CERN Document Server

Van Sciver, Steven W

2012-01-01

Twenty five years have elapsed since the original publication of Helium Cryogenics. During this time, a considerable amount of research and development involving helium fluids has been carried out culminating in several large-scale projects. Furthermore, the field has matured through these efforts so that there is now a broad engineering base to assist the development of future projects. Helium Cryogenics, 2nd edition brings these advances in helium cryogenics together in an updated form. As in the original edition, the author's approach is to survey the field of cryogenics with emphasis on helium fluids. This approach is more specialized and fundamental than that contained in other cryogenics books, which treat the associated range of cryogenic fluids. As a result, the level of treatment is more advanced and assumes a certain knowledge of fundamental engineering and physics principles, including some quantum mechanics. The goal throughout the work is to bridge the gap between the physics and engineering aspe...

On Field Theory of Open Strings, Tachyon Condensation and Closed Strings

OpenAIRE

Shatashvili, Samson L.

2001-01-01

I review the physical properties of different vacua in the background independent open string field theory. Talk presented at Strings 2001, Mumbai, India, http://theory.theory.tifr.res.in/strings/Proceedings/#sha-s.

Determining Mechanical Parameters for Spin in Tennis Strings

DEFF Research Database (Denmark)

Bendtsen, Kaare; Rasmussen, Kasper; Hansen, Martin B.

2015-01-01

The ability to generate spin is a key element for any tennis player. However, the mechanical parameters of tennis strings which contribute to producing spin are poorly understood. This study attempted to determine some of these parameters through a spin test and a tensile test. Nine different...... string types with different gauges, geometry, price and user ratings were tested. The main finding of the study was that the three gauges of MSV Co Focus were able to generate significantly (p

Closed Strings From Nothing

Energy Technology Data Exchange (ETDEWEB)

Lawrence, Albion

2001-07-25

We study the physics of open strings in bosonic and type II string theories in the presence of unstable D-branes. When the potential energy of the open string tachyon is at its minimum, Sen has argued that only closed strings remain in the perturbative spectrum. We explore the scenario of Yi and of Bergman, Hori and Yi, who argue that the open string degrees of freedom are strongly coupled and disappear through confinement. We discuss arguments using open string field theory and worldsheet boundary RG flows, which seem to indicate otherwise. We then describe a solitonic excitation of the open string tachyon and gauge field with the charge and tension of a fundamental closed string. This requires a double scaling limit where the tachyon is taken to its minimal value and the electric field is taken to its maximum value. The resulting flux tube has an unconstrained spatial profile; and for large fundamental string charge, it appears to have light, weakly coupled open strings living in the core. We argue that the flux tube acquires a size or order {alpha}' through sigma model and string coupling effects; and we argue that confinement effects make the light degrees of freedom heavy and strongly interacting.

Closed Strings From Nothing

International Nuclear Information System (INIS)

Lawrence, Albion

2001-01-01

We study the physics of open strings in bosonic and type II string theories in the presence of unstable D-branes. When the potential energy of the open string tachyon is at its minimum, Sen has argued that only closed strings remain in the perturbative spectrum. We explore the scenario of Yi and of Bergman, Hori and Yi, who argue that the open string degrees of freedom are strongly coupled and disappear through confinement. We discuss arguments using open string field theory and worldsheet boundary RG flows, which seem to indicate otherwise. We then describe a solitonic excitation of the open string tachyon and gauge field with the charge and tension of a fundamental closed string. This requires a double scaling limit where the tachyon is taken to its minimal value and the electric field is taken to its maximum value. The resulting flux tube has an unconstrained spatial profile; and for large fundamental string charge, it appears to have light, weakly coupled open strings living in the core. We argue that the flux tube acquires a size or order α' through sigma model and string coupling effects; and we argue that confinement effects make the light degrees of freedom heavy and strongly interacting

How to simulate global cosmic strings with large string tension

Energy Technology Data Exchange (ETDEWEB)

Klaer, Vincent B.; Moore, Guy D., E-mail: vklaer@theorie.ikp.physik.tu-darmstadt.de, E-mail: guy.moore@physik.tu-darmstadt.de [Institut für Kernphysik, Technische Universität Darmstadt, Schlossgartenstraße 2, Darmstadt, D-64289 Germany (Germany)

2017-10-01

Global string networks may be relevant in axion production in the early Universe, as well as other cosmological scenarios. Such networks contain a large hierarchy of scales between the string core scale and the Hubble scale, ln( f {sub a} / H ) ∼ 70, which influences the network dynamics by giving the strings large tensions T ≅ π f {sub a} {sup 2} ln( f {sub a} / H ). We present a new numerical approach to simulate such global string networks, capturing the tension without an exponentially large lattice.

String field theory

International Nuclear Information System (INIS)

Kaku, M.

1987-01-01

In this article, the authors summarize the rapid progress in constructing string field theory actions, such as the development of the covariant BRST theory. They also present the newer geometric formulation of string field theory, from which the BRST theory and the older light cone theory can be derived from first principles. This geometric formulation allows us to derive the complete field theory of strings from two geometric principles, in the same way that general relativity and Yang-Mills theory can be derived from two principles based on global and local symmetry. The geometric formalism therefore reduces string field theory to a problem of finding an invariant under a new local gauge group they call the universal string group (USG). Thus, string field theory is the gauge theory of the universal string group in much the same way that Yang-Mills theory is the gauge theory of SU(N). The geometric formulation places superstring theory on the same rigorous group theoretical level as general relativity and gauge theory

Vacuum degeneracy in four-dimensional string theories

International Nuclear Information System (INIS)

Nilles, H.P.

1988-01-01

I present results obtained in collaboration with A. Font, L. Ibanez and F. Quevedo using a method that links explicit string constructions with the techniques of supergravity field theories. We make use of the fact that the supersymmetric vacua of the field theory limit of d=4 N=1 superstring theories are all degenerate. Given a particular string theory we can then test for new 'nearby' string theories by an examination of flat directions in the scalar potential of the underlying field theory. As input from string theory we need the knowledge of the Yukawa couplings (i.e., the superpotential) for any number of fields. In the language of conformal field theory, this amounts to a search for exactly marginal operators and the classification of multicritical points. (orig./HSI)

BPS limit of multi- D- and DF-strings in boundary string field theory

International Nuclear Information System (INIS)

Go, Gyungchoon; Ishida, Akira; Kim, Yoonbai

2007-01-01

A BPS limit is systematically derived for straight multi- D- and DF-strings from the D3D-bar3 system in the context of boundary superstring field theory. The BPS limit is obtained in the limit of thin D(F)-strings, where the Bogomolny equation supports singular static multi-D(F)-string solutions. For the BPS multi-string configurations with arbitrary separations, BPS sum rule is fulfilled under a Gaussian type tachyon potential and reproduces exactly the descent relation. For the DF-strings ((p,q)-strings), the distribution of fundamental string charge density coincides with its energy density and the Hamiltonian density takes the BPS formula of square-root form

Cryogenic system for the HERA magnet measurement facility

International Nuclear Information System (INIS)

Barton, H.R. Jr.; Clausen, M.; Kebler, G.

1986-01-01

This paper describes the design for a helium, cryogenic distribution system that allows independent operation and testing of superconducting magnets of the HERA project before they are installed in the 6-km ring tunnel. The 820-GeV proton storage ring of HERA will contain approximately 650 magnets having superconducting coils which are clamped by aluminum/stainless-steel collars and surrounded by a yoke of magnetic iron at liquid helium temperature. When the magnets arive at DESY from the manufacture, each magnet will be individually tested at helium operating conditions in the magnet measurement facility to insure the quality of the magnetic characteristics and the cryogenic performance. The capabilities of the cryogenic system and the schedule for magnet testing are discussed

The arithmetic of strings

International Nuclear Information System (INIS)

Freund, P.G.O.

1988-01-01

According to the author nobody has succeeded as yet in extracting any new numbers from string theory. This paper discusses how if one cannot get new numbers from string theory, maybe one can get new strings out of number theory. Number theory is generally regarded as the purest form of mathematics. So how can it conceivably make contact with physics which aims at describing nature? The author discusses how the connecting link of these two disciplines is provided by the compact Riemann surfaces. These appear as world sheets of interacting strings. For instance, string-string scattering at the three-loop level involves the four external strings attaching themselves to a genus three compact surface

Mirror fusion test facility cryogenic system - performance, management approach, and present equipment status

International Nuclear Information System (INIS)

Slack, D.S.; Chronis, W.C.

1988-01-01

The cryogenic system for the MFTF is a helium refrigeration system that proved to be successful and cost effective. All operating objectives were met while remaining within a few percent of the initial cost and schedule plans. The management approach used at MFTF is assessed. Manpower levels, extent and type of industrial participation, and subcontractor specifications and interactions are reviewed along with highlights of system testing, documentation, and operation

Cryogenic exciter

Science.gov (United States)

Bray, James William [Niskayuna, NY; Garces, Luis Jose [Niskayuna, NY

2012-03-13

The disclosed technology is a cryogenic static exciter. The cryogenic static exciter is connected to a synchronous electric machine that has a field winding. The synchronous electric machine is cooled via a refrigerator or cryogen like liquid nitrogen. The static exciter is in communication with the field winding and is operating at ambient temperature. The static exciter receives cooling from a refrigerator or cryogen source, which may also service the synchronous machine, to selected areas of the static exciter and the cooling selectively reduces the operating temperature of the selected areas of the static exciter.

Bowed Strings

Science.gov (United States)

Rossing, Thomas D.; Hanson, Roger J.

In the next eight chapters, we consider some aspects of the science of bowed string instruments, old and new. In this chapter, we present a brief discussion of bowed strings, a subject that will be developed much more thoroughly in Chap. 16. Chapters 13-15 discuss the violin, the cello, and the double bass. Chapter 17 discusses viols and other historic string instruments, and Chap. 18 discusses the Hutchins-Schelleng violin octet.

The theta-structure in string theories - 1: bosonic strings

International Nuclear Information System (INIS)

Li Miao.

1985-09-01

We explored the theta-structures in bosonic string theories which are similar to those in gauge field theories. The theta-structure of string is due to the multiply connected spatial compact subspace of space-time. The work of this paper shows that there is an energy band E(theta) in the string theory and one may move the tachyon out in theory by choosing some proper theta parameters. (author)

Stringing physics along

Energy Technology Data Exchange (ETDEWEB)

Riordan, M. [Stanford University and the University of California, Santa Cruz (United States)]. E-mail: mriordan@ucsc.edu

2007-02-15

In the last few decades, however, physical theory has drifted away from the professional norms advocated by Newton and other enlightenment philosophers. A vast outpouring of hypotheses has occurred under the umbrella of what is widely called string theory. But string theory is not really a 'theory' at all - at least not in the strict sense that scientists generally use the term. It is instead a dense, weedy thicket of hypotheses and conjectures badly in need of pruning. That pruning, however, can come only from observation and experiment, to which string theory (a phrase I will grudgingly continue using) is largely inaccessible. String theory was invented in the 1970s in the wake of the Standard Model of particle physics. Encouraged by the success of gauge theories of the strong, weak and electromagnetic forces, theorists tried to extend similar ideas to energy and distance scales that are orders of magnitude beyond what can be readily observed or measured. The normal, healthy intercourse between theory and experiment - which had led to the Standard Model - has broken down, and fundamental physics now finds itself in a state of crisis. So it is refreshing to hear from a theorist - one who was deeply involved with string theory and championed it in his previous book, Three Roads to Quantum Gravity - that all is not well in this closeted realm. Smolin argues from the outset that viable hypotheses must lead to observable consequences by which they can be tested and judged. String theory by its very nature does not allow for such probing, according to Smolin, and therefore it must be considered as an unprovable conjecture. Towards the end of his book, Smolin suggests other directions fundamental physics can take, particularly in the realm of quantum gravity, to resolve its crisis and reconnect with the observable world. From my perspective, he leans a bit too heavily towards highly speculative ideas such as doubly special relativity, modified Newtonian

Proceedings of strings, 89

International Nuclear Information System (INIS)

Arnowitt, R.; Bryan, R.; Duff, M.J.; Nanopoulos, D.; Pope, C.N.

1990-01-01

Does string theory provide us with a consistent quantum theory of gravity? Is it that Holy Grail of elementary particle physics, a Theory of Everything with embraces all the forces and particles of Nature? Even if it is, can we extract concrete predictions about our low-energy world that can be tested experimentally at the SSC and other particle accelerators? What does it have to say about the origin of the Universe and the thorny problem of the cosmological constant? Are superstring theories unique, or might the eleven-dimensional supermembrane prove equally consistent? These are just some of the question posed and debated at Strings '89

Cosmic strings

International Nuclear Information System (INIS)

Bennett, D.P.

1988-07-01

Cosmic strings are linear topological defects that are predicted by some grand unified theories to form during a spontaneous symmetry breaking phase transition in the early universe. They are the basis for the only theories of galaxy formation aside from quantum fluctuations from inflation that are based on fundamental physics. In contrast to inflation, they can also be observed directly through gravitational lensing and their characteristic microwave background anistropy. It has recently been discovered by F. Bouchet and myself that details of cosmic string evolution are very different from the so-called ''standard model'' that has been assumed in most of the string induced galaxy formation calculations. Therefore, the details of galaxy formation in the cosmic string models are currently very uncertain. 29 refs., 9 figs

Multiflavor string-net models

Science.gov (United States)

Lin, Chien-Hung

2017-05-01

We generalize the string-net construction to multiple flavors of strings, each of which is labeled by the elements of an Abelian group Gi. The same flavor of strings can branch, while different flavors of strings can cross one another and thus they form intersecting string nets. We systematically construct the exactly soluble lattice Hamiltonians and the ground-state wave functions for the intersecting string-net condensed phases. We analyze the braiding statistics of the low-energy quasiparticle excitations and find that our model can realize all the topological phases as the string-net model with group G =∏iGi . In this respect, our construction provides various ways of building lattice models which realize topological order G , corresponding to different partitions of G and thus different flavors of string nets. In fact, our construction concretely demonstrates the Künneth formula by constructing various lattice models with the same topological order. As an example, we construct the G =Z2×Z2×Z2 string-net model which realizes a non-Abelian topological phase by properly intersecting three copies of toric codes.

Heterotic cosmic strings

International Nuclear Information System (INIS)

Becker, Katrin; Becker, Melanie; Krause, Axel

2006-01-01

We show that all three conditions for the cosmological relevance of heterotic cosmic strings, the right tension, stability and a production mechanism at the end of inflation, can be met in the strongly coupled M-theory regime. Whereas cosmic strings generated from weakly coupled heterotic strings have the well-known problems posed by Witten in 1985, we show that strings arising from M5-branes wrapped around 4-cycles (divisors) of a Calabi-Yau in heterotic M-theory compactifications solve these problems in an elegant fashion

Leak testing of cryogenic components — problems and solutions

Science.gov (United States)

Srivastava, S. P.; Pandarkar, S. P.; Unni, T. G.; Sinha, A. K.; Mahajan, K.; Suthar, R. L.

2008-05-01

A prototype of Cold Neutron Source (CNS) for Dhruva Reactor is being manufactured at Centre for Design and Manufacture (CDM), BARC, Mumbai for validating the mechanical and thermal engineering design aspects, besides checking the integrity of all joints and components at low temperature, 77K. Task of a Cold Neutron Source is to generate cold neutrons by cooling down the thermal neutrons, which are originally produced in a nuclear research reactor. The complete Cold Neutron Source system comprises a complex arrangement of moderator pot, transfer line (piping), pumps, refrigerators, storage tanks, a heat exchanger and associated controls and instrumentation. The heart of the system is moderator pot in which water (moderator) is cooled down by Liquid Nitrogen (LN2) being circulated through an annular cavity machined on the walls of the pot. Transfer lines for LN2 basically consist of two concentric Stainless Steel flexible pipes, which are joined to the inlet and outlet Aluminium tubes of the moderator pot through transition joints. Leak in any component may result in loss of liquid Nitrogen, degradation of vacuum, which in turn may affect the heat removal efficiency of the source. Hence, leak testing was considered a very important quality control tool and all joints and components were subjected to helium leak test using mass spectrometer leak detector (MSLD) at cryogenic temperature. During one of the earlier experiments, flow of LN2 through inner flexible pipe of the transfer line resulted in rise of pressure in the vacuum annulus and sweating on the outer flexible pipe. After investigations it was found that large thermal stress compounded with mechanical stress resulted in cracks in the inner pipe. Accordingly design was modified to get leak proof transfer line assembly. Further, during leak testing of thin wall moderator pot, gross leak was observed on the outer jacket welded joint. Leak was so large that even a small amount of Helium gas in the vicinity of the

A novel string field theory solving string theory by liberating left and right movers

International Nuclear Information System (INIS)

Nielsen, Holger B.; Ninomiya, Masao

2014-01-01

We put forward ideas to a novel string field theory based on making some “objects” that essentially describe “liberated” left- and right- mover fields X L μ (τ+σ) and X R μ (τ−σ) on the string. Our novel string field theory is completely definitely different from any other string theory in as far as a “null set” of information in the string field theory Fock space has been removed relatively, to the usual string field theories. So our theory is definitely new. The main progress is that we manage to make our novel string field theory provide the correct mass square spectrum for the string. We finally suggest how to obtain the Veneziano amplitude in our model

SNS Cryogenic Test Facility Kinney Vacuum Pump Commissioning and Operation at 2 K

Energy Technology Data Exchange (ETDEWEB)

Degraff, Brian D. [ORNL; Howell, Matthew P. [ORNL; Kim, Sang-Ho [ORNL; Neustadt, Thomas S. [ORNL

2017-07-01

The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL) has built and commissioned an independent Cryogenic Test Facility (CTF) in support of testing in the Radio-frequency Test Facility (RFTF). Superconducting Radio-frequency Cavity (SRF) testing was initially conducted with the CTF cold box at 4.5 K. A Kinney vacuum pump skid consisting of a roots blower with a liquid ring backing pump was recently added to the CTF system to provide testing capabilities at 2 K. System design, pump refurbishment and installation of the Kinney pump will be presented. During the commissioning and initial testing period with the Kinney pump, several barriers to achieve reliable operation were experienced. Details of these lessons learned and improvements to skid operations will be presented. Pump capacity data will also be presented.

SNS Cryogenic Test Facility Kinney Vacuum Pump Commissioning and Operation at 2 K

Science.gov (United States)

DeGraff, B.; Howell, M.; Kim, S.; Neustadt, T.

2017-12-01

The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL) has built and commissioned an independent Cryogenic Test Facility (CTF) in support of testing in the Radio-frequency Test Facility (RFTF). Superconducting Radio-frequency Cavity (SRF) testing was initially conducted with the CTF cold box at 4.5 K. A Kinney vacuum pump skid consisting of a roots blower with a liquid ring backing pump was recently added to the CTF system to provide testing capabilities at 2 K. System design, pump refurbishment and installation of the Kinney pump will be presented. During the commissioning and initial testing period with the Kinney pump, several barriers to achieve reliable operation were experienced. Details of these lessons learned and improvements to skid operations will be presented. Pump capacity data will also be presented.

Cryogenic testing and analysis associated with Tevatron lower temperature operation

International Nuclear Information System (INIS)

Theilacker, J.C.

1996-09-01

An upgrade of the Tevatron cryogenic system was installed and commissioned in 1993 to allow lower temperature operation. As a result, higher energy operation is possible. Following the installation and initial commissioning, it was decided to continue the current colliding beam physics at the previous energy of 900 GeV. This has allowed us to perform parasitic lower temperature tests in the Tevatron over the last year and a half. This paper presents the results of operational experiences and thermal and hydraulic testing which has taken place. The primary goal of the testing is to better understand the operation of the cold compressor system, associated instrumentation, and the performance of the existing magnet system during lower temperature operation. This will lead to a tentatively scheduled higher energy test run in the fall of 1995. The test results have shown that more elaborate controlling methods are necessary in order to achieve reliable system operation. Fortunately, our new satellite refrigerator controls system is capable of the expansion necessary to reach our goal. New features are being added to the control system which will allow for more intelligent control and better diagnostics for component monitoring and trending

StarDB: a large-scale DBMS for strings

KAUST Repository

Sahli, Majed

2015-08-01

Strings and applications using them are proliferating in science and business. Currently, strings are stored in file systems and processed using ad-hoc procedural code. Existing techniques are not flexible and cannot efficiently handle complex queries or large datasets. In this paper, we demonstrate StarDB, a distributed database system for analytics on strings. StarDB hides data and system complexities and allows users to focus on analytics. It uses a comprehensive set of parallel string operations and provides a declarative query language to solve complex queries. StarDB automatically tunes itself and runs with over 90% efficiency on supercomputers, public clouds, clusters, and workstations. We test StarDB using real datasets that are 2 orders of magnitude larger than the datasets reported by previous works.

Polynomial invariants for torus knots and topological strings

International Nuclear Information System (INIS)

Labastida, J.M.F.

2001-01-01

We make a precision test of a recently proposed conjecture relating Chern-Simons gauge theory to topological string theory on the resolution of the conifold. First, we develop a systematic procedure to extract string amplitudes from vacuum expectation values (vevs) of Wilson loops in Chern-Simons gauge theory, and then we evaluate these vevs in arbitrary irreducible representations of SU(N) for torus knots. We find complete agreement with the predictions derived from the target space interpretation of the string amplitudes. We also show that the structure of the free energy of topological open string theory gives further constraints on the Chern-Simons vevs. Our work provides strong evidence towards an interpretation of knot polynomial invariants as generating functions associated to enumerative problems. (orig.)

Practical-scale tests of cryogenic molecular sieve for separating low-concentration hydrogen isotopes from helium

International Nuclear Information System (INIS)

Willms, R.S.; Taylor, D.J.; Enoeda, Mikio; Okuno, Kenji

1994-01-01

Earlier bench-scale work at the Tritium Systems Test Assembly (TSTA) at Los Alamos National Laboratory examined a number of adsorbents for their suitability for separating low-concentration hydrogen (no tritium) from helium. One of the effective adsorbents was Linde 5A molecular sieve. Recently, experiments including tritium were conducted using practical-scale adsorbers. These tests used existing cryogenic molecular sieve beds (CMSB's) which each contain about 1.6 kg of Linde 5A molecular sieve. They are part of the TSTA integrated tritium processing system. Gas was fed to each CMSB at about 13 SLPM with a nominal composition of 99% He, 0.98% H 2 and 0.02% HT. In all cases, for an extended period of time, the beds allowed no detectable (via Raman spectroscopy) hydrogen isotopes to escape in the bed effluent. Thereafter, the hydrogen isotopes appeared in the bed exit with a relatively sharp breakthrough curve. This work concludes that cryogenic molecular sieve adsorption is an practical and effective means of separating low-concentration hydrogen isotopes from a helium carrier

Results of radiation tests at cryogenic temperature on some selected organic materials for the LHC

International Nuclear Information System (INIS)

Schoenbacher, H.; Szeless, B.; Tavlet, M.; Humer, K.; Weber, H.W.

1996-01-01

Future multi-TeV particle accelerators like the CERN Large Hadron Collider (LHC) will use superconducting magnets where organic materials will be exposed to high radiation levels at temperatures as low as 2 K. A representative selection of organic materials comprising insulating films, cable insulations, and epoxy-type impregnated resins were exposed to neutron and gamma radiation of a nuclear reactor. Depending on the type of materials, the integrated radiation doses varied between 180 kGy and 155 MGy. During irradiation, the samples were kept close to the boiling temperature of liquid nitrogen i.e. ∼ 80 K and thereafter stored in liquid nitrogen and transferred at the same temperature into the testing device for measurement of tensile and flexural strength. Tests were carried out on the same materials at similar dose rates at room temperature, and the results were compared with those obtained at cryogenic temperature. They show that, within the selected dose range, a number of organic materials are suitable for use in the radiation field of the LHC at cryogenic temperature. (orig.)

String model for the dynamics of glass-forming liquids.

Science.gov (United States)

Pazmiño Betancourt, Beatriz A; Douglas, Jack F; Starr, Francis W

2014-05-28

We test the applicability of a living polymerization theory to describe cooperative string-like particle rearrangement clusters (strings) observed in simulations of a coarse-grained polymer melt. The theory quantitatively describes the interrelation between the average string length L, configurational entropy Sconf, and the order parameter for string assembly Φ without free parameters. Combining this theory with the Adam-Gibbs model allows us to predict the relaxation time τ in a lower temperature T range than accessible by current simulations. In particular, the combined theories suggest a return to Arrhenius behavior near Tg and a low T residual entropy, thus avoiding a Kauzmann "entropy crisis."

Exceptional groups from open strings

International Nuclear Information System (INIS)

Gaberdiel, M.R.; Zwiebach, B.

1998-01-01

We consider type IIB theory compactified on a two-sphere in the presence of mutually non-local 7-branes. The BPS states associated with the gauge vectors of exceptional groups are seen to arise from open strings connecting the 7-branes, and multi-pronged open strings capable of ending on more than two 7-branes. These multi-pronged strings are built from open string junctions that arise naturally when strings cross 7-branes. The different string configurations can be multiplied as traditional open strings, and are shown to generate the structure of exceptional groups. (orig.)

Evidence for string substructure

International Nuclear Information System (INIS)

Bergman, O.

1996-06-01

The author argues that the behavior of string theory at high temperature and high longitudinal boosts, combined with the emergence of p-branes as necessary ingredients in various string dualities, point to a possible reformulation of strings, as well as p-branes, as composites of bits. He reviews the string-bit models, and suggests generalizations to incorporate p-branes

Strings, texture, and inflation

International Nuclear Information System (INIS)

Hodges, H.M.; Primack, J.R.

1991-01-01

We examine mechanisms, several of which are proposed here, to generate structure formation, or to just add large-scale features, through either gauged or global cosmic strings or global texture, within the framework of inflation. We first explore the possibility that strings or texture form if there is no coupling between the topological theory and the inflaton or spacetime curvature, via (1) quantum creation, and (2) a sufficiently high reheat temperature. In addition, we examine the prospects for the inflaton field itself to generate strings or texture. Then, models with the string/texture field coupled to the curvature, and an equivalent model with coupling to the inflaton field, are considered in detail. The requirement that inflationary density fluctuations are not so large as to conflict with observations leads to a number of constraints on model parameters. We find that strings of relevance for structure formation can form in the absence of coupling to the inflaton or curvature through the process of quantum creation, but only if the strings are strongly type I, or if they are global strings. If formed after reheating, naturalness suggests that gauged cosmic strings correspond to a type-I superconductor. Similarly, gauged strings formed during inflation via conformal coupling ξ=1/6 to the spacetime curvature (in a model suggested by Yokoyama in order to evade the millisecond pulsar constraint on cosmic strings) are expected to be strongly type I

String Theory - The Physics of String-Bending and Other Electric Guitar Techniques

Science.gov (United States)

Grimes, David Robert

2014-01-01

Electric guitar playing is ubiquitous in practically all modern music genres. In the hands of an experienced player, electric guitars can sound as expressive and distinct as a human voice. Unlike other more quantised instruments where pitch is a discrete function, guitarists can incorporate micro-tonality and, as a result, vibrato and sting-bending are idiosyncratic hallmarks of a player. Similarly, a wide variety of techniques unique to the electric guitar have emerged. While the mechano-acoustics of stringed instruments and vibrating strings are well studied, there has been comparatively little work dedicated to the underlying physics of unique electric guitar techniques and strings, nor the mechanical factors influencing vibrato, string-bending, fretting force and whammy-bar dynamics. In this work, models for these processes are derived and the implications for guitar and string design discussed. The string-bending model is experimentally validated using a variety of strings and vibrato dynamics are simulated. The implications of these findings on the configuration and design of guitars is also discussed. PMID:25054880

String theory--the physics of string-bending and other electric guitar techniques.

Directory of Open Access Journals (Sweden)

David Robert Grimes

Full Text Available Electric guitar playing is ubiquitous in practically all modern music genres. In the hands of an experienced player, electric guitars can sound as expressive and distinct as a human voice. Unlike other more quantised instruments where pitch is a discrete function, guitarists can incorporate micro-tonality and, as a result, vibrato and sting-bending are idiosyncratic hallmarks of a player. Similarly, a wide variety of techniques unique to the electric guitar have emerged. While the mechano-acoustics of stringed instruments and vibrating strings are well studied, there has been comparatively little work dedicated to the underlying physics of unique electric guitar techniques and strings, nor the mechanical factors influencing vibrato, string-bending, fretting force and whammy-bar dynamics. In this work, models for these processes are derived and the implications for guitar and string design discussed. The string-bending model is experimentally validated using a variety of strings and vibrato dynamics are simulated. The implications of these findings on the configuration and design of guitars is also discussed.

String theory--the physics of string-bending and other electric guitar techniques.

Science.gov (United States)

Grimes, David Robert

2014-01-01

Electric guitar playing is ubiquitous in practically all modern music genres. In the hands of an experienced player, electric guitars can sound as expressive and distinct as a human voice. Unlike other more quantised instruments where pitch is a discrete function, guitarists can incorporate micro-tonality and, as a result, vibrato and sting-bending are idiosyncratic hallmarks of a player. Similarly, a wide variety of techniques unique to the electric guitar have emerged. While the mechano-acoustics of stringed instruments and vibrating strings are well studied, there has been comparatively little work dedicated to the underlying physics of unique electric guitar techniques and strings, nor the mechanical factors influencing vibrato, string-bending, fretting force and whammy-bar dynamics. In this work, models for these processes are derived and the implications for guitar and string design discussed. The string-bending model is experimentally validated using a variety of strings and vibrato dynamics are simulated. The implications of these findings on the configuration and design of guitars is also discussed.

Cryogenic system for TRISTAN superconducting RF cavity

International Nuclear Information System (INIS)

Hosoyama, K.; Hara, K.; Kabe, A.; Kojima, Yuuji; Ogitsu, T.; Sakamoto, Y.; Kawamura, S.; Ishimaru, Y.

1990-01-01

A cryogenic system consisting of a helium refrigerator (4 kW at 4.4 K) and a liquid helium distribution transfer system for TRISTAN 508 MHz 32 x 5-cell superconducting RF cavities was designed and constructed. After the performance test of the cryogenic system, 16 x 5-cell superconducting RF cavities in 8 cryostats were installed in underground TRISTAN electron-positron collider and connected to the helium refrigerator on the ground level through the transfer line (total length about 330 m) and cooled by liquid helium pool boiling in parallel. The cryogenic system and its operation experience are described. (author)

Maximum margin classifier working in a set of strings.

Science.gov (United States)

Koyano, Hitoshi; Hayashida, Morihiro; Akutsu, Tatsuya

2016-03-01

Numbers and numerical vectors account for a large portion of data. However, recently, the amount of string data generated has increased dramatically. Consequently, classifying string data is a common problem in many fields. The most widely used approach to this problem is to convert strings into numerical vectors using string kernels and subsequently apply a support vector machine that works in a numerical vector space. However, this non-one-to-one conversion involves a loss of information and makes it impossible to evaluate, using probability theory, the generalization error of a learning machine, considering that the given data to train and test the machine are strings generated according to probability laws. In this study, we approach this classification problem by constructing a classifier that works in a set of strings. To evaluate the generalization error of such a classifier theoretically, probability theory for strings is required. Therefore, we first extend a limit theorem for a consensus sequence of strings demonstrated by one of the authors and co-workers in a previous study. Using the obtained result, we then demonstrate that our learning machine classifies strings in an asymptotically optimal manner. Furthermore, we demonstrate the usefulness of our machine in practical data analysis by applying it to predicting protein-protein interactions using amino acid sequences and classifying RNAs by the secondary structure using nucleotide sequences.

String Theory and M-Theory

Science.gov (United States)

Becker, Katrin; Becker, Melanie; Schwarz, John H.

String theory is one of the most exciting and challenging areas of modern theoretical physics. This book guides the reader from the basics of string theory to recent developments. It introduces the basics of perturbative string theory, world-sheet supersymmetry, space-time supersymmetry, conformal field theory and the heterotic string, before describing modern developments, including D-branes, string dualities and M-theory. It then covers string geometry and flux compactifications, applications to cosmology and particle physics, black holes in string theory and M-theory, and the microscopic origin of black-hole entropy. It concludes with Matrix theory, the AdS/CFT duality and its generalizations. This book is ideal for graduate students and researchers in modern string theory, and will make an excellent textbook for a one-year course on string theory. It contains over 120 exercises with solutions, and over 200 homework problems with solutions available on a password protected website for lecturers at www.cambridge.org/9780521860697. Comprehensive coverage of topics from basics of string theory to recent developments Ideal textbook for a one-year course in string theory Includes over 100 exercises with solutions Contains over 200 homework problems with solutions available to lecturers on-line

New expressions for string loop amplitudes leading to an ultra-simple conception of string dynamics

International Nuclear Information System (INIS)

Chan Hongmo; Tsou Sheungtsun; Bordes, J.; Nellen, L.

1990-11-01

New expressions are derived for string loop amplitudes as overlap integrals of string wave functionals. They are shown to take the form of exchange terms coming from the Bose-Einstein symmetrisation between string segments. One is thus led to the ultra-simple conception that string theory is basically free, and that 'string interactions' are due merely to the fact that strings are composite objects with Bose-Einstein segments as constituents. (author)

Cryogen free low temperature sample environment for neutron scattering experiments

International Nuclear Information System (INIS)

Kirichek, O; Evans, B E; Down, R B E; Bowden, Z A

2009-01-01

Recent increase in liquid helium cost caused by global helium supply problems rose significant concern about affordability of conventional cryogenic equipment. Luckily the progress in cryo-cooler technology offers a new generation of cryogenic systems with significantly reduced consumption and in some cases nearly complete elimination of cryogens. These cryogen-free systems also offer the advantage of operational simplicity and require less space than conventional cryogen-cooled systems. The ISIS facility carries on an internal development program intended to substitute gradually all conventional cryogenic systems with cryogen free systems preferably based on pulse tube refrigerators. A unique feature of this cryo-cooler is the absence of cold moving parts. This considerably reduces vibrations and increases the reliability of the cold head. The program includes few development projects which are aiming to deliver range of cryogen free equipment including top-loading cryostat, superconducting magnets and dilution refrigerators. Here we are going to describe the design of these systems and discuss the results of prototypes testing.

Stretching cosmic strings

International Nuclear Information System (INIS)

Turok, N.; Bhattacharjee, P.

1984-01-01

The evolution of a network of strings produced at a grand-unification phase transition in an expanding universe is discussed, with particular reference to the processes of energy exchange between the strings and the rest of the universe. This is supported by numerical calculations simulating the behavior of strings in an expanding universe. It is found that in order that the energy density of the strings does not come to dominate the total energy density there must be an efficient mechanism for energy loss: the only plausible one being the production of closed loops and their subsequent decay via gravitational radiation

Cryogenic heat transfer

CERN Document Server

Barron, Randall F

2016-01-01

Cryogenic Heat Transfer, Second Edition continues to address specific heat transfer problems that occur in the cryogenic temperature range where there are distinct differences from conventional heat transfer problems. This updated version examines the use of computer-aided design in cryogenic engineering and emphasizes commonly used computer programs to address modern cryogenic heat transfer problems. It introduces additional topics in cryogenic heat transfer that include latent heat expressions; lumped-capacity transient heat transfer; thermal stresses; Laplace transform solutions; oscillating flow heat transfer, and computer-aided heat exchanger design. It also includes new examples and homework problems throughout the book, and provides ample references for further study.

Cryogenic Testing of Different Seam Concepts for Multilayer Insulation Systems

Science.gov (United States)

Johnson, Wesley L.; Fesmire, J. E.

2009-01-01

Recent testing in a cylindrical, comparative cryostat at the Cryogenics Test Laboratory has focused on various seam concepts for multilayer insulation systems. Three main types of seams were investigated: straight overlap, fold-over, and roll wrapped. Each blanket was comprised of 40 layer pairs of reflector and spacer materials. The total thickness was approximately 12.5-mm, giving an average layer density of 32 layers per centimeter. The blankets were tested at high vacuum, soft vacuum, and no vacuum using liquid nitrogen to maintain the cold boundary temperature at 77 K. Test results show that all three seam concepts are all close in thermal performance; however the fold-over method provides the lowest heat flux. For the first series of tests, seams were located 120 degrees around the circumference of the cryostat from the previous seam. This technique appears to have lessened the degradation of the blanket due to the seams. In a follow-on test, a 20 layer blanket was tested in a roll wrapped configuration and then cut down the side of the cylinder, taped together, and re-tested. This test result shows the thermal performance impact of having the seams all in one location versus having the seams clocked around the vessel. This experimental investigation indicates that the method of joining the seams in multilayer insulation systems is not as critical as the quality of the installation process.

Design, implementation, and testing of a cryogenic loading capability on an engineering neutron diffractometer

Energy Technology Data Exchange (ETDEWEB)

Woodruff, T. R.; Krishnan, V. B.; Vaidyanathan, R. [Department of Mechanical, Materials, and Aerospace Engineering, Advanced Materials Processing and Analysis Center (AMPAC), University of Central Florida, Orlando, Florida 32816 (United States); Clausen, B.; Sisneros, T.; Livescu, V.; Brown, D. W.; Bourke, M. A. M. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2010-06-15

A novel capability was designed, implemented, and tested for in situ neutron diffraction measurements during loading at cryogenic temperatures on the spectrometer for materials research at temperature and stress at Los Alamos National Laboratory. This capability allowed for the application of dynamic compressive forces of up to 250 kN on standard samples controlled at temperatures between 300 and 90 K. The approach comprised of cooling thermally isolated compression platens that in turn conductively cooled the sample in an aluminum vacuum chamber which was nominally transparent to the incident and diffracted neutrons. The cooling/heat rate and final temperature were controlled by regulating the flow of liquid nitrogen in channels inside the platens that were connected through bellows to the mechanical actuator of the load frame and by heaters placed on the platens. Various performance parameters of this system are reported here. The system was used to investigate deformation in Ni-Ti-Fe shape memory alloys at cryogenic temperatures and preliminary results are presented.

M-strings, Elliptic Genera and N=4 String Amplitudes

CERN Document Server

Hohenegger, Stefan

2014-01-01

We study mass-deformed N=2 gauge theories from various points of view. Their partition functions can be computed via three dual approaches: firstly, (p,q)-brane webs in type II string theory using Nekrasov's instanton calculus, secondly, the (refined) topological string using the topological vertex formalism and thirdly, M theory via the elliptic genus of certain M-strings configurations. We argue for a large class of theories that these approaches yield the same gauge theory partition function which we study in detail. To make their modular properties more tangible, we consider a fourth approach by connecting the partition function to the equivariant elliptic genus of R^4 through a (singular) theta-transform. This form appears naturally as a specific class of one-loop scattering amplitudes in type II string theory on T^2, which we calculate explicitly.

String Math 2017

CERN Document Server

The series of String-Math conferences has developed into a central event on the interface between mathematics and physics related to string theory, quantum field theory and neighboring subjects. The conference will take place from July 24-28 in the main building of Hamburg university. The String-Math conference is organised by the University of Hamburg jointly with DESY Hamburg.

Cryogenic immersion microscope

Science.gov (United States)

Le Gros, Mark; Larabell, Carolyn A.

2010-12-14

A cryogenic immersion microscope whose objective lens is at least partially in contact with a liquid reservoir of a cryogenic liquid, in which reservoir a sample of interest is immersed is disclosed. When the cryogenic liquid has an index of refraction that reduces refraction at interfaces between the lens and the sample, overall resolution and image quality are improved. A combination of an immersion microscope and x-ray microscope, suitable for imaging at cryogenic temperatures is also disclosed.

Cryogenic and Gas System Piping Pressure Tests (A Collection of PT Permits)

International Nuclear Information System (INIS)

Rucinski, Russell A.

2002-01-01

This engineering note is a collection of pipe pressure testing documents for various sections of piping for the D-Zero cryogenic and gas systems. High pressure piping must conform with FESHM chapter 5031.1. Piping lines with ratings greater than 150 psig have a pressure test done before the line is put into service. These tests require the use of pressure testing permits. It is my intent that all pressure piping over which my group has responsibility conforms to the chapter. This includes the liquid argon and liquid helium and liquid nitrogen cryogenic systems. It also includes the high pressure air system, and the high pressure gas piping of the WAMUS and MDT gas systems. This is not an all inclusive compilation of test documentation. Some piping tests have their own engineering note. Other piping section test permits are included in separate safety review documents. So if it isn't here, that doesn't mean that it wasn't tested. D-Zero has a back up air supply system to add reliability to air compressor systems. The system includes high pressure piping which requires a review per FESHM 5031.1. The core system consists of a pressurized tube trailer, supply piping into the building and a pressure reducing regulator tied into the air compressor system discharge piping. Air flows from the trailer if the air compressor discharge pressure drops below the regulator setting. The tube trailer is periodically pumped back up to approximately 2000 psig. A high pressure compressor housed in one of the exterior buildings is used for that purpose. The system was previously documented, tested and reviewed for Run I, except for the recent addition of piping to and from the high pressure compressor. The following documents are provided for review of the system: (1) Instrument air flow schematic, drg. 3740.000-ME-273995 rev. H; (2) Component list for air system; (3) Pressure testing permit for high pressure piping; (4) Documentation from Run I contained in D-Zero Engineering note

Cryogenic Propellant Storage and Transfer

Data.gov (United States)

National Aeronautics and Space Administration — Space Flight Demonstration development has been canceled in favor of a ground test bed development for of passive/active cryogenic propellant storage, transfer, and...

Automatic Attraction of Visual Attention by Supraletter Features of Former Target Strings

Directory of Open Access Journals (Sweden)

Søren eKyllingsbæk

2014-11-01

Full Text Available Observers were trained to search for a particular horizontal string of 3 capital letters presented among similar strings consisting of exactly the same letters in different orders. The training was followed by a test in which the observers searched for a new target that was identical to one of the former distractors. The new distractor set consisted of the remaining former distractors plus the former target. On each trial, three letter-strings were displayed, which included the target string with a probability of .5. In Experiment 1, the strings were centered at different locations on the circumference of an imaginary circle around the fixation point. The training phase of Experiment 2 was similar, but in the test phase of the experiment, the strings were located in a vertical array centered on fixation, and in target-present arrays, the target always appeared at fixation. In both experiments, performance (d’ degraded on trials in which former targets were present, suggesting that the former targets automatically drew processing resources away from the current targets. Apparently, the two experiments showed automatic attraction of visual attention by supraletter features of former target strings.

Patterned-string tasks: relation between fine motor skills and visual-spatial abilities in parrots.

Directory of Open Access Journals (Sweden)

Anastasia Krasheninnikova

Full Text Available String-pulling and patterned-string tasks are often used to analyse perceptual and cognitive abilities in animals. In addition, the paradigm can be used to test the interrelation between visual-spatial and motor performance. Two Australian parrot species, the galah (Eolophus roseicapilla and the cockatiel (Nymphicus hollandicus, forage on the ground, but only the galah uses its feet to manipulate food. I used a set of string pulling and patterned-string tasks to test whether usage of the feet during foraging is a prerequisite for solving the vertical string pulling problem. Indeed, the two species used techniques that clearly differed in the extent of beak-foot coordination but did not differ in terms of their success in solving the string pulling task. However, when the visual-spatial skills of the subjects were tested, the galahs outperformed the cockatiels. This supports the hypothesis that the fine motor skills needed for advanced beak-foot coordination may be interrelated with certain visual-spatial abilities needed for solving patterned-string tasks. This pattern was also found within each of the two species on the individual level: higher motor abilities positively correlated with performance in patterned-string tasks. This is the first evidence of an interrelation between visual-spatial and motor abilities in non-mammalian animals.

Nanotribological behavior of deep cryogenically treated martensitic stainless steel

Directory of Open Access Journals (Sweden)

Germán Prieto

2017-08-01

Full Text Available Cryogenic treatments are increasingly used to improve the wear resistance of various steel alloys by means of transformation of retained austenite, deformation of virgin martensite and carbide refinement. In this work the nanotribological behavior and mechanical properties at the nano-scale of cryogenically and conventionally treated AISI 420 martensitic stainless steel were evaluated. Conventionally treated specimens were subjected to quenching and annealing, while the deep cryogenically treated samples were quenched, soaked in liquid nitrogen for 2 h and annealed. The elastic–plastic parameters of the materials were assessed by nanoindentation tests under displacement control, while the friction behavior and wear rate were evaluated by a nanoscratch testing methodology that it is used for the first time in steels. It was found that cryogenic treatments increased both hardness and elastic limit of a low-carbon martensitic stainless steel, while its tribological performance was enhanced marginally.

Nanotribological behavior of deep cryogenically treated martensitic stainless steel.

Science.gov (United States)

Prieto, Germán; Bakoglidis, Konstantinos D; Tuckart, Walter R; Broitman, Esteban

2017-01-01

Cryogenic treatments are increasingly used to improve the wear resistance of various steel alloys by means of transformation of retained austenite, deformation of virgin martensite and carbide refinement. In this work the nanotribological behavior and mechanical properties at the nano-scale of cryogenically and conventionally treated AISI 420 martensitic stainless steel were evaluated. Conventionally treated specimens were subjected to quenching and annealing, while the deep cryogenically treated samples were quenched, soaked in liquid nitrogen for 2 h and annealed. The elastic-plastic parameters of the materials were assessed by nanoindentation tests under displacement control, while the friction behavior and wear rate were evaluated by a nanoscratch testing methodology that it is used for the first time in steels. It was found that cryogenic treatments increased both hardness and elastic limit of a low-carbon martensitic stainless steel, while its tribological performance was enhanced marginally.

Insulation design of cryogenic bushing for superconducting electric power applications

Energy Technology Data Exchange (ETDEWEB)

Koo, J.Y., E-mail: koojy@hanyang.ac.kr [Department of Electronics, Electrical, Control and Instrumentation Engineering, Hanyang University, Ansan 426-791 (Korea, Republic of); Lee, Y.J.; Shin, W.J.; Kim, Y.H. [Department of Electronics, Electrical, Control and Instrumentation Engineering, Hanyang University, Ansan 426-791 (Korea, Republic of); Kim, J.T. [Department of Electrical Engineering, Daejin University, Pocheon 487-711 (Korea, Republic of); Lee, B.W. [Department of Electronics, Electrical, Control and Instrumentation Engineering, Hanyang University, Ansan 426-791 (Korea, Republic of); Lee, S.H., E-mail: k720lsh@kins.re.kr [Expert Group Electric and Control Department, Korea Institute of Nuclear Safety, Daejeon 305-600 (Korea, Republic of)

2013-01-15

Highlights: ► In this paper, design factors of cryogenic bushings were discussed and test results of specimen were introduced in detail. ► We focused on the comparative study of breakdown characteristics of different electrode materials. ► Puncture and creepage breakdown characteristics were analyzed based on the withstand voltage. ► We obtained the basic design factors of extra high voltage condenser bushing. ► We obtained the basic design factors of extra high voltage condenser bushing, which could be used in cryogenic environment. -- Abstract: Recently, the superconductivity projects to develop commercial superconducting devices for extra high voltage transmission lines have been undergoing in many countries. One of the critical components to be developed for high voltage superconducting devices, including superconducting transformers, cables, and fault current limiters, is a high voltage bushing, to supply high current to devices without insulating difficulties, that is designed for cryogenic environments. Unfortunately, suitable bushings for HTS equipment were not fully developed for some cryogenic insulation issues. Such high voltage bushings would need to provide electrical insulation capabilities from room temperature to cryogenic temperatures. In this paper, design factors of cryogenic bushings were discussed and test results of specimen were introduced in detail. First, the dielectric strength of three kinds of metals has been measured with uniform and non-uniform electrodes by withstand voltage of impulse and AC breakdown test in LN{sub 2}. Second, puncture breakdown voltage of glass fiber reinforced plastics (GFRPs) plates has been analyzed with non-uniform electrodes. Finally, creepage discharge voltages were measured according to the configuration of non-uniform and uniform electrode on the FRP plate. From the test results, we obtained the basic design factors of extra high voltage condenser bushing, which could be used in cryogenic

Cryogenic Pupil Alignment Test Architecture for Aberrated Pupil Images

Science.gov (United States)

Bos, Brent; Kubalak, David A.; Antonille, Scott; Ohl, Raymond; Hagopian, John G.

2009-01-01

A document describes cryogenic test architecture for the James Webb Space Telescope (JWST) integrated science instrument module (ISIM). The ISIM element primarily consists of a mechanical metering structure, three science instruments, and a fine guidance sensor. One of the critical optomechanical alignments is the co-registration of the optical telescope element (OTE) exit pupil with the entrance pupils of the ISIM instruments. The test architecture has been developed to verify that the ISIM element will be properly aligned with the nominal OTE exit pupil when the two elements come together. The architecture measures three of the most critical pupil degrees-of-freedom during optical testing of the ISIM element. The pupil measurement scheme makes use of specularly reflective pupil alignment references located inside the JWST instruments, ground support equipment that contains a pupil imaging module, an OTE simulator, and pupil viewing channels in two of the JWST flight instruments. Pupil alignment references (PARs) are introduced into the instrument, and their reflections are checked using the instrument's mirrors. After the pupil imaging module (PIM) captures a reflected PAR image, the image will be analyzed to determine the relative alignment offset. The instrument pupil alignment preferences are specularly reflective mirrors with non-reflective fiducials, which makes the test architecture feasible. The instrument channels have fairly large fields of view, allowing PAR tip/tilt tolerances on the order of 0.5deg.

Gravitational effects of global strings

International Nuclear Information System (INIS)

Aryal, M.; Everett, A.E.

1986-01-01

We have obtained the gravitational field, in the weak-field approximation, of cosmic strings formed in a phase transition in which a global symmetry is broken (global strings). The effect of this field on light rays passing a global string is found, and the resulting formation of double images and production of discontinuities in the microwave background temperature compared with the corresponding results for gauge strings. There are some differences in the case of global strings, reflecting the fact that the space surrounding such strings is not purely conical. However, the differences between gauge and global strings with masses suitable to explain galaxy formation are small, and the task of distinguishing them observationally appears difficult at best

International conference on string theory

CERN Document Server

2017-01-01

The Strings 2017 conference is part of the "Strings" series of annual conferences, that bring the entire string theory community together. It will include reviews of major developments in the field, and specialized talks on specific topics. There will also be several public lectures given by conference participants, a pre-Strings school at the Technion, and a post-Strings workshop at the Weizmann Institute.

Cryogenic testing and analysis associated with Tevatron lower temperature operation

International Nuclear Information System (INIS)

Theilacker, J.C.

1996-01-01

An upgrade of the Tevatron cryogenic system was installed and commissioned in 1993 to allow lower temperature operation. As a result, higher energy operation of the Fermilab superconducting Tevatron accelerator is possible. Following the installation and initial commissioning, it was decided to continue the current colliding beam physics run at the previous energy of 900 GeV. This has allowed the author to perform parasitic lower temperature tests in the Tevatron over the last year and a half. This paper presents the results of operational experiences and thermal and hydraulic testing which have taken place. The primary goal of the testing is to better understand the operation of the cold compressor system, associated instrumentation, and the performance of the existing magnet system during lower temperature operation. This will lead to a tentatively scheduled higher energy test run in the fall of 1995. The test results have shown that more elaborate controlling methods are necessary in order to achieve reliable system operation. Fortunately, the new satellite refrigerator controls system is capable of the expansion necessary to reach this goal. New features are being added to the controls systems which will allow for more intelligent control and better diagnostics for component monitoring and trending

Cosmic strings and inflation

International Nuclear Information System (INIS)

Vishniac, E.T.

1987-01-01

We examine the compatibility of inflation with the cosmic string theory for galaxy formation. There is a general conflict between having sufficient string tension to effect galaxy formation, and reheating after inflation to a high enough temperature that strings may form in a thermal phase transition. To escape this conflict, we propose a class of models where the inflation is coupled to the string-producing field. The strings are formed late in inflation as the inflaton rolls towards its zero-temperature value. A large subset of these models have a novel large-scale distribution of galaxies that is fractal, displays biasing without dynamics or feedback mechanisms, and contains voids. (orig.)

Increasing stringiness of low-fat mozzarella string cheese using polysaccharides.

Science.gov (United States)

Oberg, E N; Oberg, C J; Motawee, M M; Martini, S; McMahon, D J

2015-07-01

When fat content of pasta filata cheese is lowered, a loss of fibrous texture occurs and low-fat (LF) mozzarella cheese loses stringiness, making it unsuitable for the manufacture of string cheese. We investigated the use of various polysaccharides that could act as fat mimetics during the stretching and extruding process to aid in protein strand formation and increase stringiness. Low-fat mozzarella cheese curd was made, salted, and then 3.6-kg batches were heated in hot (80°) 5% brine, stretched, and formed into a homogeneous mass. Hot (80°C) slurries of various polysaccharides were then mixed with the hot cheese and formed into LF string cheese using a small piston-driven extruder. Polysaccharides used included waxy corn starch, waxy rice starch, instant tapioca starch, polydextrose, xanthan gum, and guar gum. Adding starch slurries increased cheese moisture content by up to 1.6% but was not effective at increasing stringiness. Xanthan gum functioned best as a fat mimetic and produced LF string cheese that most closely visually resembled commercial string cheese made using low-moisture part skim (LMPS) mozzarella cheese without any increase in moisture content. Extent of stringiness was determined by pulling apart the cheese longitudinally and observing size, length, and appearance of individual cheese strings. Hardness was determined using a modified Warner-Bratzler shear test. When LF string cheese was made using a 10% xanthan gum slurry added at ~1%, increased consumer flavor liking was observed, with scores after 2wk of storage of 6.44 and 6.24 compared with 5.89 for the LF control cheese; although this was lower than an LMPS string cheese that scored 7.27. The 2-wk-old LF string cheeses containing xanthan gum were considered still slightly too firm using a just-about-right (JAR) test, whereas the LMPS string cheese was considered as JAR for texture. With further storage up to 8wk, all of the LF string cheeses softened (JAR score was closer to 3

String-Math 2015

CERN Document Server

2015-01-01

Welcome to String-Math 2015 at Sanya. The conference will be opened in December 31, 2015- January 4, 2016. String theory plays a central role in theoretical physics as a candidate for the quantum theory unifying gravity with other interactions. It has profound connections with broad branches of modern mathematics ever since the birth. In the last decades, the prosperous interaction, built upon the joint efforts from both mathematicians and physicists, has given rise to marvelous deep results in supersymmetric gauge theory, topological string, M-theory and duality on the physics side as well as in algebraic geometry, differential geometry, algebraic topology, representation theory and number theory on the mathematics side. The interplay is two-fold. The mathematics has provided powerful tools to fulfill the physical interconnection of ideas and clarify physical structures to understand the nature of string theory. On the other hand, ideas from string theory and quantum field theory have been a source of sign...

The application of cryogenics to high Reynolds number testing in wind tunnels. I - Evolution, theory, and advantages

Science.gov (United States)

Kilgore, R. A.; Dress, D. A.

1984-01-01

During the time which has passed since the construction of the first wind tunnel in 1870, wind tunnels have been developed to a high degree of sophistication. However, their development has consistently failed to keep pace with the demands placed on them. One of the more serious problems to be found with existing transonic wind tunnels is their inability to test subscale aircraft models at Reynolds numbers sufficiently near full-scale values to ensure the validity of using the wind tunnel data to predict flight characteristics. The Reynolds number capability of a wind tunnel may be increased by a number of different approaches. However, the best solution in terms of model, balance, and model support loads, as well as in terms of capital and operating cost appears to be related to the reduction of the temperature of the test gas to cryogenic temperatures. The present paper has the objective to review the evolution of the cryogenic wind tunnel concept and to describe its more important advantages.

A highly reliable cryogenic mixing pump with no mechanical moving parts

Science.gov (United States)

Chen, W.; Niblick, A. L.

2017-12-01

This paper presents the design and preliminary test results of a novel cryogenic mixing pump based on magnetocaloric effect. The mixing pump is developed to enable long-term cryogenic propellant storage in space by preventing thermal stratification of cryogens in storage tanks. The mixing pump uses an innovative thermodynamic process to generate fluid jets to promote fluid mixing, eliminating the need for mechanical pumps. Its innovative mechanism uses a solid magnetocaloric material to alternately vaporize and condense the cryogen in the pumping chamber, and thus control the volume of the fluid inside the pumping chamber to produce pumping action. The pump is capable of self-priming and can generate a high-pressure rise. This paper discusses operating mechanism and design consideration of the pump, introduces the configuration of a brassboard cryogenic pump, and presents the preliminary test results of the pump with liquid nitrogen.

Deterministic indexing for packed strings

DEFF Research Database (Denmark)

Bille, Philip; Gørtz, Inge Li; Skjoldjensen, Frederik Rye

2017-01-01

Given a string S of length n, the classic string indexing problem is to preprocess S into a compact data structure that supports efficient subsequent pattern queries. In the deterministic variant the goal is to solve the string indexing problem without any randomization (at preprocessing time...... or query time). In the packed variant the strings are stored with several character in a single word, giving us the opportunity to read multiple characters simultaneously. Our main result is a new string index in the deterministic and packed setting. Given a packed string S of length n over an alphabet σ...

Topics in string theory

International Nuclear Information System (INIS)

Neveu, A.

1986-01-01

There exist several string models. In the first lecture, the simplest one, the open bosonic string, which turns out to live most naturally in 26 dimensions will be described in some detail. In the second lecture, the closed bosonic strings, and the open and closed 10-dimensional strings (superstrings) are reviewed. In the third lecture, various compactification schemes which have been proposed to deal with the extra space dimensions, from 4 to 10 or 26 are dealt with; in particular, the Frenkel-Kac construction which builds non-Abelian internal symmetry groups out of the compactified dimensions, and the resulting heterotic string are described. Finally, in the fourth lecture, the important problem of the second quantization of string theories, and of the underlying gauge invariance which is responsible for the possibility of dealing, in a consistent fashion, with interacting high-spin states without negative metric is addressed. 41 references, 8 figures

Recent Advances and Applications in Cryogenic Propellant Densification Technology

Science.gov (United States)

Tomsik, Thomas M.

2000-01-01

This purpose of this paper is to review several historical cryogenic test programs that were conducted at the NASA Glenn Research Center (GRC), Cleveland, Ohio over the past fifty years. More recently these technology programs were intended to study new and improved denser forms of liquid hydrogen (LH2) and liquid oxygen (LO2) cryogenic rocket fuels. Of particular interest are subcooled cryogenic propellants. This is due to the fact that they have a significantly higher density (eg. triple-point hydrogen, slush etc.), a lower vapor pressure and improved cooling capacity over the normal boiling point cryogen. This paper, which is intended to be a historical technology overview, will trace the past and recent development and testing of small and large-scale propellant densification production systems. Densifier units in the current GRC fuels program, were designed and are capable of processing subcooled LH2 and L02 propellant at the X33 Reusable Launch Vehicle (RLV) scale. One final objective of this technical briefing is to discuss some of the potential benefits and application which propellant densification technology may offer the industrial cryogenics production and end-user community. Density enhancements to cryogenic propellants (LH2, LO2, CH4) in rocket propulsion and aerospace application have provided the opportunity to either increase performance of existing launch vehicles or to reduce the overall size, mass and cost of a new vehicle system.

Oriented open-closed string theory revisited

International Nuclear Information System (INIS)

Zwiebach, B.

1998-01-01

String theory on D-brane backgrounds is open-closed string theory. Given the relevance of this fact, we give details and elaborate upon our earlier construction of oriented open-closed string field theory. In order to incorporate explicitly closed strings, the classical sector of this theory is open strings with a homotopy associative A ∞ algebraic structure. We build a suitable Batalin-Vilkovisky algebra on moduli spaces of bordered Ricmann surfaces, the construction of which involves a few subtleties arising from the open string punctures and cyclicity conditions. All vertices coupling open and closed strings through disks are described explicitly. Subalgebras of the algebra of surfaces with boundaries are used to discuss symmetries of classical open string theory induced by the closed string sector, and to write classical open string field theory on general closed string backgrounds. We give a preliminary analysis of the ghost-dilaton theorem. copyright 1998 Academic Press, Inc

Multiquark strings

International Nuclear Information System (INIS)

Wang, F.; Chun, W.

1985-01-01

The use of basis states described as hadronic (or hadron-hadron) or hidden-colour (or colour-colour) for a system of quarks does not necessarily imply that connected exotic multiquark hadrons do exist. Antisymmetrization of quark wave functions tends to make these descriptions ill defined. It appears necessary to have stable collective structures called strings or bags to provide the physical connections required by quark confinement. The masses of multiquark hadrons can then be estimated by using semplified string, bag and NR potential models. The results turn out to be qualitatively similar in all these models. The stability problem for multiquark strings is briefly discussed

Open string model building

International Nuclear Information System (INIS)

Ishibashi, Nobuyuki; Onogi, Tetsuya

1989-01-01

Consistency conditions of open string theories, which can be a powerful tool in open string model building, are proposed. By making use of these conditions and assuming a simple prescription for the Chan-Paton factors, open string theories in several backgrounds are studied. We show that 1. there exist a large number of consistent bosonic open string theories on Z 2 orbifolds, 2. SO(32) type I superstring is the unique consistent model among fermionic string theories on the ten-dimensional flat Minkowski space, and 3. with our prescription for the Chan-Paton factors, there exist no consistent open superstring theories on (six-dimensional Minkowski space-time) x (Z 2 orbifold). (orig.)

Progress in string theory research

CERN Document Server

2016-01-01

At the first look, the String Theory seems just an interesting and non-trivial application of the quantum mechanics and the special relativity to vibrating strings. By itself, the quantization of relativistic strings does not call the attention of the particle physicist as a significant paradigm shift. However, when the string quantization is performed by applying the standard rules of the perturbative Quantum Field Theory, one discovers that the strings in certain states have the same physical properties as the gravity in the flat space-time. Chapter one of this book reviews the construction of the thermal bosonic string and D-brane in the framework of the Thermo Field Dynamics (TFD). It briefly recalls the wellknown light-cone quantization of the bosonic string in the conformal gauge in flat space-time, and gives a bird’s eye view of the fundamental concepts of the TFD. Chapter two examines a visual model inspired by string theory, on the system of interacting anyons. Chapter three investigate the late-ti...

Cosmic strings and galaxy formation

International Nuclear Information System (INIS)

Bertschinger, E.

1989-01-01

Cosmic strings have become increasingly popular candidates as seeds for the formation of structure in the universe. This scenario, remains a serious cosmogonical model despite close scrutiny. In constrast, magnetic monopoles and domain walls - relic topological defects as are cosmic strings - are disastrous for cosmology if they are left over from the early universe. The production of heavy cosmic strings is speculative, as it depends on the details of ultrahigh energy physics. Fortunately, speculation about cosmic strings is not entirely idle because, if they exist and are heavy enough to seed galaxy formation, cosmic strings can be detected astronomically. Failure to detect cosmic strings would impose some constraints on grand unified theories (GUTs); their discovery would have exciting consequences for high energy physics and cosmology. This article reviews the basic physics of nonsuperconducting cosmic strings, highlighting the field theory aspects, and provides a progress report on calculations of structure formation with cosmic strings

String-localized quantum fields

International Nuclear Information System (INIS)

Mund, Jens; Santos, Jose Amancio dos; Silva, Cristhiano Duarte; Oliveira, Erichardson de

2009-01-01

Full text. The principles of physics admit (unobservable) quantum fields which are localized not on points, but on strings in the sense of Mandelstam: a string emanates from a point in Minkowski space and extends to infinity in some space-like direction. This type of localization might permit the construction of new models, for various reasons: (a) in general, weaker localization implies better UV behaviour. Therefore, the class of renormalizable interactions in the string-localized has a chance to be larger than in the point-localized case; (b) for certain particle types, there are no point-localized (free) quantum fields - for example Anyons in d = 2 + 1, and Wigner's massless 'infinite spin' particles. For the latter, free string-localized quantum fields have been constructed; (c) in contrast to the point-localized case, string-localization admits covariant vector/tensor potentials for fotons and gravitons in a Hilbert space representation with positive energy. We shall present free string-localized quantum fields for various particle types, and some ideas about the perturbative construction of interacting string-localized fields. A central point will be an analogue of gauge theories, completely within a Hilbert space and without ghosts, trading gauge dependence with dependence on the direction of the localization string. In order to discuss renormalizability (item (a)), methods from microlocal analysis (wave front set and scaling degree) are needed. (author)

Cryogen Safety Course 8876

Energy Technology Data Exchange (ETDEWEB)

Glass, George [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2017-06-13

Cryogenics (from the Greek word κρvoζ, meaning frost or icy cold) is the study of the behavior of matter at very cold temperatures. The purpose of this course is to provide trainees with an introduction to cryogen use, the hazards and potential accidents related to cryogen systems, cryogen safety components, and the requirements that govern the design and use of cryogen systems at Los Alamos National Laboratory (LANL). The knowledge you gain will help you keep your workplace safe for yourself and your coworkers.

Device for balancing parallel strings

Science.gov (United States)

Mashikian, Matthew S.

1985-01-01

A battery plant is described which features magnetic circuit means in association with each of the battery strings in the battery plant for balancing the electrical current flow through the battery strings by equalizing the voltage across each of the battery strings. Each of the magnetic circuit means generally comprises means for sensing the electrical current flow through one of the battery strings, and a saturable reactor having a main winding connected electrically in series with the battery string, a bias winding connected to a source of alternating current and a control winding connected to a variable source of direct current controlled by the sensing means. Each of the battery strings is formed by a plurality of batteries connected electrically in series, and these battery strings are connected electrically in parallel across common bus conductors.

Strings in the Sun?

International Nuclear Information System (INIS)

Chudnovsky, E.; Vilenkin, A.

1988-01-01

If light superconducting strings were formed in the early Universe, then it is very likely that now they exist in abundance in the interstellar plasma and in stars. The dynamics of such strings can be dominated by friction, so that they are ''frozen'' into the plasma. Turbulence of the plasma twists and stretches the strings, forming a stochastic string network. Such networks must generate particles and magnetic fields, and may play an important role in the physics of stars and of the Galaxy

Thermodynamics of quantum strings

CERN Document Server

Morgan, M J

1994-01-01

A statistical mechanical analysis of an ideal gas of non-relativistic quantum strings is presented, in which the thermodynamic properties of the string gas are calculated from a canonical partition function. This toy model enables students to gain insight into the thermodynamics of a simple 'quantum field' theory, and provides a useful pedagogical introduction to the more complicated relativistic string theories. A review is also given of the thermodynamics of the open bosonic string gas and the type I (open) superstring gas. (author)

Dynamics of Carroll strings

Energy Technology Data Exchange (ETDEWEB)

Cardona, Biel [Departament d’Estructura i Constituents de la Matèriaand Institut de Ciències del Cosmos (ICCUB) Facultat de Física, Universitat de Barcelona,Diagonal 647, E-08028 Barcelona, Catalonia (Spain); Gomis, Joaquim [Departament d’Estructura i Constituents de la Matèriaand Institut de Ciències del Cosmos (ICCUB) Facultat de Física, Universitat de Barcelona,Diagonal 647, E-08028 Barcelona, Catalonia (Spain); Department of Physics, Faculty of Science, Chulalongkorn University,Bangkok 10330 (Thailand); Pons, Josep M. [Departament d’Estructura i Constituents de la Matèriaand Institut de Ciències del Cosmos (ICCUB) Facultat de Física, Universitat de Barcelona,Diagonal 647, E-08028 Barcelona, Catalonia (Spain)

2016-07-11

We construct the canonical action of a Carroll string doing the Carroll limit of a canonical relativistic string. We also study the Killing symmetries of the Carroll string, which close under an infinite dimensional algebra. The tensionless limit and the Carroll p-brane action are also discussed.

Cosmic strings and cosmic structure

International Nuclear Information System (INIS)

Albrecht, A.; Brandenberger, R.; Turok, N.

1987-01-01

The paper concerns the application of the theory of cosmic strings to explain the structure of the Universe. The formation of cosmic strings in the early Universe is outlined, along with the Big Bang theory, Grand Unified theories, and the first three minutes after the Big Bang. A description is given of the shaping of the Universe by cosmic strings, including the evolution of the string. The possibility for direct observation of cosmic strings is discussed. (U.K.)

Cryogenic Moisture Uptake in Foam Insulation for Space Launch Vehicles

Science.gov (United States)

Fesmire, James E.; ScholtensCoffman, Brekke E.; Sass, Jared P.; Williams, Martha K.; Smith, Trent M.; Meneghelli, Barrry J.

2008-01-01

Rigid polyurethane foams and rigid polyisocyanurate foams (spray-on foam insulation), like those flown on Shuttle, Delta IV, and will be flown on Ares-I and Ares-V, can gain an extraordinary amount of water when under cryogenic conditions for several hours. These foams, when exposed for eight hours to launch pad environments on one side and cryogenic temperature on the other, increase their weight from 35 to 80 percent depending on the duration of weathering or aging. This effect translates into several thousand pounds of additional weight for space vehicles at lift-off. A new cryogenic moisture uptake apparatus was designed to determine the amount of water/ice taken into the specimen under actual-use propellant loading conditions. This experimental study included the measurement of the amount of moisture uptake within different foam materials. Results of testing using both aged specimens and weathered specimens are presented. To better understand cryogenic foam insulation performance, cryogenic moisture testing is shown to be essential. The implications for future launch vehicle thermal protection system design and flight performance are discussed.

Commissioning of the LHC Cryogenic System Subsystems Cold Commissioning in Preparation of Full Sector Tests

CERN Document Server

Serio, L; Ferlin, G; Gilbert, N; Gruehagen, Henning; Knoops, S; Parente, C; Sanmartí, M

2006-01-01

The cryogenic system for the Large Hadron Collider accelerator is presently in its final phase of installation and commissioning at nominal operating temperatures. The refrigeration capacity for the LHC will be produced using eight large cryogenic plants installed on five technical sites and distributed around the 26.7-km circumference ring located in a deep underground tunnel. The status of the cryogenic system commissioning is presented together with the experience gained in operating and commissioning it.

The string-pulling paradigm in comparative psychology.

Science.gov (United States)

Jacobs, Ivo F; Osvath, Mathias

2015-05-01

String pulling is one of the most widely used paradigms in comparative psychology. First documented 2 millennia ago, it has been a well-established scientific paradigm for a century. More than 160 bird and mammal species have been tested in over 200 studies with countless methodological variations. The paradigm can be used to address a wide variety of issues on animal cognition; for example, what animals understand about contact and connection as well as whether they rely on perceptual feedback, grasp the functionality of strings, generalize across conditions, apply their knowledge flexibly, and possess insight. Mammals are typically tested on a horizontal configuration, birds on a vertical one, making the studies difficult to compare; in particular, pulling a string vertically requires better coordination and attention. A species' performance on the paradigm is often influenced by its ecology, especially concerning whether limbs are used for foraging. Many other factors can be of importance and should be considered. The string-pulling paradigm is easy to administer, vary, and apply to investigate a wide array of cognitive abilities. Although it can be and has been used to compare species, divergent methods and unclear reporting have limited its comparative utility. With increasing research standards, the paradigm is expected to become an even more fundamental tool in comparative psychology. (c) 2015 APA, all rights reserved).

Use of the TACL [Thaumaturgic Automated Control Logic] system at CEBAF [Continuous Electron Beam Accelerator Facility] for control of the Cryogenic Test Facility

International Nuclear Information System (INIS)

Navarro, E.; Keesee, M.; Bork, R.; Grubb, C.; Lahti, G.; Sage, J.

1989-01-01

A logic-based control software system, called Thaumaturgic Automated Control Logic (TACL), is under development at the Continuous Electron Beam Accelerator Facility in Newport News, VA. The first version of the software was placed in service in November, 1987 for control of cryogenics during the first superconducting RF cavity tests at CEBAF. In August, 1988 the control system was installed at the Cryogenic Test Facility (CTF) at CEBAF. CTF generated liquid helium in September, 1988 and is now in full operation for the current round of cavity tests. TACL is providing a powerful and flexible controls environment for the operation of CTF. 3 refs

Thermal and Fluid Modeling of the CRYogenic Orbital TEstbed (CRYOTE) Ground Test Article (GTA)

Science.gov (United States)

Piryk, David; Schallhorn, Paul; Walls, Laurie; Stopnitzky, Benny; Rhys, Noah; Wollen, Mark

2012-01-01

The purpose of this study was to anchor thermal and fluid system models to data acquired from a ground test article (GTA) for the CRYogenic Orbital TEstbed - CRYOTE. To accomplish this analysis, it was broken into four primary tasks. These included model development, pre-test predictions, testing support at Marshall Space Flight Center (MSFC} and post-test correlations. Information from MSFC facilitated the task of refining and correlating the initial models. The primary goal of the modeling/testing/correlating efforts was to characterize heat loads throughout the ground test article. Significant factors impacting the heat loads included radiative environments, multi-layer insulation (MLI) performance, tank fill levels, tank pressures, and even contact conductance coefficients. This paper demonstrates how analytical thermal/fluid networks were established, and it includes supporting rationale for specific thermal responses seen during testing.

Random surfaces and strings

International Nuclear Information System (INIS)

Ambjoern, J.

1987-08-01

The theory of strings is the theory of random surfaces. I review the present attempts to regularize the world sheet of the string by triangulation. The corresponding statistical theory of triangulated random surfaces has a surprising rich structure, but the connection to conventional string theory seems non-trivial. (orig.)

Hagedorn Behavior of Little String Theories from string corrections to NS5-branes

DEFF Research Database (Denmark)

Harmark, Troels; Obers, N. A.

2000-01-01

We examine the Hagedorn behavior of little string theory using its conjectured duality with near-horizon NS5-branes. In particular, by studying the string-corrected NS5-brane supergravity solution, it is shown that tree-level corrections to the temperature vanish, while the leading one-loop string...... correction generates the correct temperature dependence of the entropy near the Hagedorn temperature. Finally, the Hagedorn behavior of ODp-brane theories, which are deformed versions of little string theory, is considered via their supergravity duals....

Lectures on strings and dualities

International Nuclear Information System (INIS)

Vafa, C.

1997-01-01

In this set of lectures I review recent developments in string theory emphasizing their non-perturbative aspects and their recently discovered duality symmetries. The goal of the lectures is to make the recent exciting developments in string theory accessible to those with no previous background in string theory who wish to join the research effort in this area. Topics covered include a brief review of string theory, its compactifications, solitons and D-branes, black hole entropy and wed of string dualities. (author)

String GUTs

International Nuclear Information System (INIS)

Aldazabal, G.; Ibanez, L.E.; Uranga, A.M.

1995-01-01

Standard SUSY-GUTs such as those based on SU(5) or SO(10) lead to predictions for the values of α s and sin 2 θ W in amazing agreement with experiment. In this article we investigate how these models may be obtained from string theory, thus bringing them into the only known consistent framework for quantum gravity. String models with matter in standard GUT representations require the realization of affine Lie algebras at higher levels. We start by describing some methods to build level k=2 symmetric orbifold string models with gauge groups SU(5) or SO(10). We present several examples and identify generic features of the type of models constructed. Chiral fields appropriate to break the symmetry down to the standard model generically appear in the massless spectrum. However, unlike in standard SUSY-GUTs, they often behave as string moduli, i.e., they do not have self-couplings. We also discuss briefly the doublet-triplet Higgs splitting. We find that, in some models, built-in sliding-singlet type of couplings exist. (orig.)

String theory and water waves

International Nuclear Information System (INIS)

Iyer, Ramakrishnan; Johnson, Clifford V; Pennington, Jeffrey S

2011-01-01

We uncover a remarkable role that an infinite hierarchy of nonlinear differential equations plays in organizing and connecting certain c-hat <1 string theories non-perturbatively. We are able to embed the type 0A and 0B (A, A) minimal string theories into this single framework. The string theories arise as special limits of a rich system of equations underpinned by an integrable system known as the dispersive water wave hierarchy. We observe that there are several other string-like limits of the system, and conjecture that some of them are type IIA and IIB (A, D) minimal string backgrounds. We explain how these and several string-like special points arise and are connected. In some cases, the framework endows the theories with a non-perturbative definition for the first time. Notably, we discover that the Painleve IV equation plays a key role in organizing the string theory physics, joining its siblings, Painleve I and II, whose roles have previously been identified in this minimal string context.

Macroscopic fundamental strings in cosmology

Energy Technology Data Exchange (ETDEWEB)

Aharonov, Y; Englert, F; Orloff, J

1987-12-24

We show that, when D greater than or equal to 4, theories of closed strings of closed strings in D, non-compact space-time dimensions exhibit a phase transition. The high-temperature phase is characterized by a condensate of arbitrarily long strings with Hausdorff dimension two (area filling curves). We suggest that this stringy phase is the ancestor of the adiabatic era. Fundamental strings could then both drive the inflation and seed, in a way reminiscent of the cosmic string mechanism, the large structures in the universe.

Interpolating string field theories

International Nuclear Information System (INIS)

Zwiebach, B.

1992-01-01

This paper reports that a minimal area problem imposing different length conditions on open and closed curves is shown to define a one-parameter family of covariant open-closed quantum string field theories. These interpolate from a recently proposed factorizable open-closed theory up to an extended version of Witten's open string field theory capable of incorporating on shell closed strings. The string diagrams of the latter define a new decomposition of the moduli spaces of Riemann surfaces with punctures and boundaries based on quadratic differentials with both first order and second order poles

Baryon string model

International Nuclear Information System (INIS)

Klimenko, S.V.; Kochin, V.N.; Plyushchaj, M.S.; Pron'ko, G.P.; Razumov, A.V.; Samarin, A.V.

1985-01-01

Partial solutions to classical equations of three-string motion are considered. Simplest solutions, when three-string center moving with high velocity, are co nsidered. Single-mode solutions are studied. Explicit form of their parametrization is obtained and three-string dynamics visualization is made. Means of graphic packet ''Atom'' were used for visualization. A set of processes for graphic representation of multiparametric functions is developed. Peculiarity of these processes is a wide class of functions, which are represented by parametric, coordinate and functional isolines

String theory compactifications

CERN Document Server

Graña, Mariana

2017-01-01

The lectures in this book provide graduate students and non-specialist researchers with a concise introduction to the concepts and formalism required to reduce the ten-dimensional string theories to the observable four-dimensional space-time - a procedure called string compactification. The text starts with a very brief introduction to string theory, first working out its massless spectrum and showing how the condition on the number of dimensions arises. It then dwells on the different possible internal manifolds, from the simplest to the most relevant phenomenologically, thereby showing that the most elegant description is through an extension of ordinary Riemannian geometry termed generalized geometry, which was first introduced by Hitchin. Last but not least, the authors review open problems in string phenomenology, such as the embedding of the Standard Model and obtaining de Sitter solutions.

Observation of Motion of Bowed Strings and Resonant Strings in Violin Performances

Science.gov (United States)

Matsutani, Akihiro

2013-10-01

The motion of a bowed string and a resonant string of a violin were simultaneously observed for the first time. The results of the direct observation of string motion in double stops and harmonics are also presented. The importance of the resonance was experimentally demonstrated from these observations. It is suggested that players should take account of the resonance and ideal Helmholtz motion in violin performances.

Maximal unbordered factors of random strings

DEFF Research Database (Denmark)

Cording, Patrick Hagge; Knudsen, Mathias Bæk Tejs

2016-01-01

A border of a string is a non-empty prefix of the string that is also a suffix of the string, and a string is unbordered if it has no border. Loptev, Kucherov, and Starikovskaya [CPM 2015] conjectured the following: If we pick a string of length n from a fixed alphabet uniformly at random...

Non-critical Poincare invariant bosonic string backgrounds and closed string tachyons

International Nuclear Information System (INIS)

Alvarez, Enrique; Gomez, Cesar; Hernandez, Lorenzo

2001-01-01

A new family of non critical bosonic string backgrounds in arbitrary space-time dimension D and with ISO(1,D-2) Poincare invariance are presented. The metric warping factor and dilaton agree asymptotically with the linear dilaton background. The closed string tachyon equation of motion enjoys, in the linear approximation, an exact solution of 'kink' type interpolating between different expectation values. A renormalization group flow interpretation, based on a closed string tachyon potential of type -T 2 e -T , is suggested

Quantum backreaction in string theory

International Nuclear Information System (INIS)

Evnin, O.

2012-01-01

There are situations in string theory when a finite number of string quanta induce a significant backreaction upon the background and render the perturbation theory infrared-divergent. The simplest example is D0-brane recoil under an impact by closed strings. A more physically interesting case is backreaction on the evolution of a totally compact universe due to closed string gas. Such situations necessitate qualitative amendments to the traditional formulation of string theory in a fixed classical background. In this contribution to the proceedings of the XVII European Workshop on String Theory in Padua, I review solved problems and current investigations in relation to this kind of quantum backreaction effects. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Laboratory facility for production of cryogenic targets for hot plasma experiments

International Nuclear Information System (INIS)

Sadowski, M.; Szydlowski, A.; Jakubowski, L.; Cwiek, E.

1990-10-01

Results of preliminary operational tests of the cryogenic stand designed for the production of small droplets of liquid hydrogen or deuterium are presented. Such cryogenic micro-targets are needed for nuclear and thermonuclear experiments. (author)

String model of elementary particles

International Nuclear Information System (INIS)

Kikkawa, Keiji

1975-01-01

Recent development of the models of elementary particles is described. The principal features of elementary particle physics can be expressed by quark model, mass spectrum, the Regge behavior of scattering amplitude, and duality. Venezians showed in 1968 that the B function can express these features. From the analysis of mass spectrum, the string model was introduced. The quantization of the string is performed with the same procedure as the ordinary quantum mechanics. The motion of the string is determined by the Nambu-Goto action integral, and the Schroedinger equation is obtained. Mass spectrum from the string model was same as that from the duality model such as Veneziano model. The interaction between strings can be introduced, and the Lagrangian can be formulated. The relation between the string model and the duality model has been studied. The string model is the first theory of non-local field, and the further development is attractive. The relation between this model and the quark model is still not clear. (Kato, T.)

Inflationary string theory?

Indian Academy of Sciences (India)

strongly motivate a detailed search for inflation within string theory, although it has ... between string theory and observations provides a strong incentive for ..... sonably be expected to arise for any system having very many degrees of freedom.

Cryogenic mechanical properties of Al-Cu-Li-Zr alloy 2090

International Nuclear Information System (INIS)

Glazer, J.; Dalder, E.N.C.; Emigh, R.A.; Verzasconi, S.L.; Yu, W.

1986-01-01

The mechanical properties of aluminum-lithium alloy 2090-T8E41 were evaluated at 298 K, 77 K, and 4 K. Previously reported tensile and fracture toughness properties at room temperature were confirmed. This alloy exhibits substantially improved properties at cryogenic temperatures; the strength, elongation, fracture toughness and fatigue crack growth resistance all improve simultaneously as the testing temperature decreases. This alloy has cryogenic properties superior to those of aluminum alloys currently used for cryogenic applications

Open strings on AdS2 branes

International Nuclear Information System (INIS)

Lee, Peter; Ooguri, Hirosi.; Park, Jongwon; Tannenhauser, Jonathan

2001-01-01

We study the spectrum of open strings on AdS 2 branes in AdS 3 in an NS-NS background, using the SL(2,R) WZW model. When the brane carries no fundamental string charge, the open string spectrum is the holomorphic square root of the spectrum of closed strings in AdS 3 . It contains short and long strings, and is invariant under spectral flow. When the brane carries fundamental string charge, the open string spectrum again contains short and long strings in all winding sectors. However, branes with fundamental string charge break half the spectral flow symmetry. This has different implications for short and long strings. As the fundamental string charge increases, the brane approaches the boundary of AdS 3 . In this limit, the induced electric field on the worldvolume reaches its critical value, producing noncommutative open string theory on AdS 2

String Theory for Pedestrians (1/3)

CERN Multimedia

CERN. Geneva

2009-01-01

This is a non-technical rapid course on string theory. Lecture 1 is an introduction to the basics of the subject: classical and quantum strings, D(irichlet) branes and string-string dualities. In lecture 2 I will discuss string unification of the fundamental forces, covering both its successes and failures. Finally in lecture 3 I will review string models of black hole microstates, the holographic gauge/gravity duality and, if time permits, potential applications to the physics of the strong interactions.

String Theory for Pedestrians (2/3)

CERN Multimedia

CERN. Geneva

2009-01-01

This is a non-technical rapid course on string theory. Lecture 1 is an introduction to the basics of the subject: classical and quantum strings, D(irichlet) branes and string-string dualities. In lecture 2 I will discuss string unification of the fundamental forces, covering both its successes and failures. Finally in lecture 3 I will review string models of black hole microstates, the holographic gauge/gravity duality and, if time permits, potential applications to the physics of the strong interactions.

String Theory for Pedestrians (3/3)

CERN Multimedia

CERN. Geneva

2009-01-01

This is a non-technical rapid course on string theory. Lecture 1 is an introduction to the basics of the subject: classical and quantum strings, D(irichlet) branes and string-string dualities. In lecture 2 I will discuss string unification of the fundamental forces, covering both its successes and failures. Finally in lecture 3 I will review string models of black hole microstates, the holographic gauge/gravity duality and, if time permits, potential applications to the physics of the strong interactions.

Testing string vacua in the lab. From a hidden CMB to dark forces in flux compactifications

Energy Technology Data Exchange (ETDEWEB)

Cicoli, Michele; Goodsell, Mark; Ringwald, Andreas [Deutsches Elektronen-Synchrotron DESY, Hamburg (Germany). Theory Group; Jaeckel, Joerg [Durham Univ. (United Kingdom). Inst. for Particle Physics Phenomenolgy

2011-03-15

We perform a detailed analysis of the phenomenological properties of hidden Abelian gauge bosons with a kinetic mixing with the ordinary photon within type IIB flux compactifications. We study the interplay between moduli stabilisation and the Green-Schwarz mechanism that gives mass to the hidden photon paying particular attention to the role of D-terms. We present two generic classes of explicit Calabi-Yau examples with an isotropic and an anisotropic shape of the extra dimensions showing how the last case turns out to be very promising to make contact with current experiments. In fact, anisotropic compactifications lead naturally to a GeV-scale hidden photon (''dark forces'' that can be searched for in beam dump experiments) for an intermediate string scale; or even to an meV-scale hidden photon (which could lead to a ''hidden CMB'' and can be tested by light-shining-through-a-wall experiments) in the case of TeV-scale strings. (orig.)

6d string chains

Science.gov (United States)

Gadde, Abhijit; Haghighat, Babak; Kim, Joonho; Kim, Seok; Lockhart, Guglielmo; Vafa, Cumrun

2018-02-01

We consider bound states of strings which arise in 6d (1,0) SCFTs that are realized in F-theory in terms of linear chains of spheres with negative self-intersections 1,2, and 4. These include the strings associated to N small E 8 instantons, as well as the ones associated to M5 branes probing A and D type singularities in M-theory or D5 branes probing ADE singularities in Type IIB string theory. We find that these bound states of strings admit (0,4) supersymmetric quiver descriptions and show how one can compute their elliptic genera.

Autonomous Cryogenics Loading Operations Simulation Software: Knowledgebase Autonomous Test Engineer

Science.gov (United States)

Wehner, Walter S., Jr.

2013-01-01

Working on the ACLO (Autonomous Cryogenics Loading Operations) project I have had the opportunity to add functionality to the physics simulation software known as KATE (Knowledgebase Autonomous Test Engineer), create a new application allowing WYSIWYG (what-you-see-is-what-you-get) creation of KATE schematic files and begin a preliminary design and implementation of a new subsystem that will provide vision services on the IHM (Integrated Health Management) bus. The functionality I added to KATE over the past few months includes a dynamic visual representation of the fluid height in a pipe based on number of gallons of fluid in the pipe and implementing the IHM bus connection within KATE. I also fixed a broken feature in the system called the Browser Display, implemented many bug fixes and made changes to the GUI (Graphical User Interface).

Dynamics of toroidal spiral strings around five-dimensional black holes

International Nuclear Information System (INIS)

Igata, Takahisa; Ishihara, Hideki

2010-01-01

We examine the separability of the Nambu-Goto equation for test strings in a shape of toroidal spiral in a five-dimensional Kerr-AdS black hole. In particular, for a 'Hopf loop' string which is a special class of the toroidal spiral strings, we show the complete separation of variables occurs in two cases, Kerr background and Kerr-AdS background with equal angular momenta. We also obtain the dynamical solution for the Hopf loop around a black hole and for the general toroidal spiral in Minkowski background.

Instability of colliding metastable strings

International Nuclear Information System (INIS)

Hiramatsu, Takashi; Kobayashi, Tatsuo; Ookouchi, Yutaka; Kyoto Univ.

2013-04-01

We investigate the collision dynamics of two metastable strings which can be viewed as tube-like domain walls with winding numbers interpolating a false vacuum and a true vacuum. We find that depending on the relative angle and speed of two strings, instability of strings increases and the false vacuum is filled out by rapid expansion of the strings or of a remnant of the collision.

String theory in four dimensions

International Nuclear Information System (INIS)

Dine, M.

1988-01-01

A representative sample of current ideas about how one might develop a string phenomenology is presented. Some of the obstacles which lie in between string theory and contact with experiment are described. It is hoped that this volume will provide the reader with ways of thinking about string theory in four dimensions and provide tools for asking questions about string theory and ordinary physics. 102 refs

Instability of colliding metastable strings

Energy Technology Data Exchange (ETDEWEB)

Hiramatsu, Takashi [Kyoto Univ. (Japan). Yukawa Inst. for Theoretical Physics; Eto, Minoru [Yamagata Univ. (Japan). Dept. of Physics; Kamada, Kohei [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Kobayashi, Tatsuo [Kyoto Univ. (Japan). Dept. of Physics; Ookouchi, Yutaka [Kyoto Univ. (Japan). Dept. of Physics; Kyoto Univ. (Japan). The Hakubi Center for Advanced Research

2013-04-15

We investigate the collision dynamics of two metastable strings which can be viewed as tube-like domain walls with winding numbers interpolating a false vacuum and a true vacuum. We find that depending on the relative angle and speed of two strings, instability of strings increases and the false vacuum is filled out by rapid expansion of the strings or of a remnant of the collision.

Superconducting cosmic strings

International Nuclear Information System (INIS)

Chudnovsky, E.M.; Field, G.B.; Spergel, D.N.; Vilenkin, A.

1986-01-01

Superconducting loops of string formed in the early Universe, if they are relatively light, can be an important source of relativistic particles in the Galaxy. They can be observed as sources of synchrotron radiation at centimeter wavelengths. We propose a string model for two recently discovered radio sources, the ''thread'' in the galactic center and the source G357.7-0.1, and predict that the filaments in these sources should move at relativistic speeds. We also consider superheavy superconducting strings, and the possibility that they be observed as extragalactic radio sources

Cryogenic Fluid Management Technology for Moon and Mars Missions

Science.gov (United States)

Doherty, Michael P.; Gaby, Joseph D.; Salerno, Louis J.; Sutherlin, Steven G.

2010-01-01

In support of the U.S. Space Exploration Policy, focused cryogenic fluid management technology efforts are underway within the National Aeronautics and Space Administration. Under the auspices of the Exploration Technology Development Program, cryogenic fluid management technology efforts are being conducted by the Cryogenic Fluid Management Project. Cryogenic Fluid Management Project objectives are to develop storage, transfer, and handling technologies for cryogens to support high performance demands of lunar, and ultimately, Mars missions in the application areas of propulsion, surface systems, and Earth-based ground operations. The targeted use of cryogens and cryogenic technologies for these application areas is anticipated to significantly reduce propellant launch mass and required on-orbit margins, to reduce and even eliminate storage tank boil-off losses for long term missions, to economize ground pad storage and transfer operations, and to expand operational and architectural operations at destination. This paper organizes Cryogenic Fluid Management Project technology efforts according to Exploration Architecture target areas, and discusses the scope of trade studies, analytical modeling, and test efforts presently underway, as well as future plans, to address those target areas. The target areas are: liquid methane/liquid oxygen for propelling the Altair Lander Ascent Stage, liquid hydrogen/liquid oxygen for propelling the Altair Lander Descent Stage and Ares V Earth Departure Stage, liquefaction, zero boil-off, and propellant scavenging for Lunar Surface Systems, cold helium and zero boil-off technologies for Earth-Based Ground Operations, and architecture definition studies for long term storage and on-orbit transfer and pressurization of LH2, cryogenic Mars landing and ascent vehicles, and cryogenic production via in situ resource utilization on Mars.

Cryogenic Electric Motor Tested

Science.gov (United States)

Brown, Gerald V.

2004-01-01

Technology for pollution-free "electric flight" is being evaluated in a number of NASA Glenn Research Center programs. One approach is to drive propulsive fans or propellers with electric motors powered by fuel cells running on hydrogen. For large transport aircraft, conventional electric motors are far too heavy to be feasible. However, since hydrogen fuel would almost surely be carried as liquid, a propulsive electric motor could be cooled to near liquid hydrogen temperature (-423 F) by using the fuel for cooling before it goes to the fuel cells. Motor windings could be either superconducting or high purity normal copper or aluminum. The electrical resistance of pure metals can drop to 1/100th or less of their room-temperature resistance at liquid hydrogen temperature. In either case, super or normal, much higher current density is possible in motor windings. This leads to more compact motors that are projected to produce 20 hp/lb or more in large sizes, in comparison to on the order of 2 hp/lb for large conventional motors. High power density is the major goal. To support cryogenic motor development, we have designed and built in-house a small motor (7-in. outside diameter) for operation in liquid nitrogen.

Transverse structure of the QCD string

International Nuclear Information System (INIS)

Meyer, Harvey B.

2010-01-01

The characterization of the transverse structure of the QCD string is discussed. We formulate a conjecture as to how the stress-energy tensor of the underlying gauge theory couples to the string degrees of freedom. A consequence of the conjecture is that the energy density and the longitudinal-stress operators measure the distribution of the transverse position of the string, to leading order in the string fluctuations, whereas the transverse-stress operator does not. We interpret recent numerical measurements of the transverse size of the confining string and show that the difference of the energy and longitudinal-stress operators is a particularly natural probe at next-to-leading order. Second, we derive the constraints imposed by open-closed string duality on the transverse structure of the string. We show that a total of three independent ''gravitational'' form factors characterize the transverse profile of the closed string, and obtain the interpretation of recent effective string theory calculations: the square radius of a closed string of length β defined from the slope of its gravitational form factor, is given by (d-1/2πσ)log(β/4r 0 ) in d space dimensions. This is to be compared with the well-known result that the width of the open string at midpoint grows as (d-1/2πσ)log(r/r 0 ). We also obtain predictions for transition form factors among closed-string states.

Simulation and experimental research of heat leakage of cryogenic transfer lines

Science.gov (United States)

Deng, B. C.; Xie, X. J.; Pan, W.; Jiang, R. X.; Li, J.; Yang, S. Q.; Li, Q.

2017-12-01

The heat leakage of cryogenic transfer lines directly influences the performance of large-scale helium refrigerator. In this paper, a thermal model of cryogenic transfer line considering numerical simulation of support coupled with MLI was established. To validate the model, test platform of cryogenic transfer lines with the merits of disassembly outer pipe and changeable easily multi-layer insulation has been built. The experimental results of heat leakage through overall length of cryogenic transfer lines, support and multi-layer insulation were obtained. The heat leakages of multi-layer insulation, a support and the overall leakage are 1.02 W/m, 0.44 W and 1.46 W/m from experimental data, respectively. The difference of heat leakage of MLI between experiment and simulation were less than 5%. The temperature distribution of support and MLI obtained in presented model in good agreement with experimental data. It is expected to reduce the overall heat leakage of cryogenic transfer lines further by optimizing structure of support based on the above thermal model and test platform in this paper.

Disordered chaotic strings

DEFF Research Database (Denmark)

Schäfer, Mirko; Greiner, Martin

2011-01-01

to chaotic strings. Inhomogeneous coupling weights as well as small-world perturbations of the ring-network structure are discussed. It is found that certain combinations of coupling and network disorder preserve the empirical relationship between chaotic strings and the weak and strong sector...

QCD and string theories

International Nuclear Information System (INIS)

Cohen-Tannoudji, G.

1990-01-01

This paper is devoted to a review of the connections between quantumchromodynamics (QCD) and string theories. One reviews the phenomenological models leading to string pictures in non perturbative QCD and the string effects, related to soft gluon coherence, which arise in perturbative QCD. One tries to build a string theory which goes to QCD at the zero slope limit. A specific model, based on superstring theories is shown to agree with QCD four point amplitudes at the Born approximation and with one loop corrections. One shows how this approach can provide a theoretical framework to account for the phenomenological property of parton-hadron duality

QCD and hadronic strings

International Nuclear Information System (INIS)

Cohen-Tannoudji, G.

1989-01-01

This series of lectures is devoted to review ot he connections between QCD and string theories. One reviews the phenomenological models leading to string pictures in non perturbative QCD and the string effects, related to soft gluon coherence, which arise in perturbative QCD. One tries to build a string theory which goes to QCD at the zero slope limit. A specific model, based on superstring theories is shown to agree with QCD four point amplitudes at the Born approximation and with one loop corrections. One shows how this approach can provide a theoretical framework to account for the phenomenological property of parton-hadron duality.(author)

Tadpole resummations in string theory

International Nuclear Information System (INIS)

Kitazawa, Noriaki

2008-01-01

While R-R tadpoles should be canceled for consistency, string models with broken supersymmetry generally have uncanceled NS-NS tadpoles. Their presence signals that the background does not solve the field equations, so that these models are in 'wrong' vacua. In this Letter we investigate, with reference to some prototype examples, whether the true values of physical quantities can be recovered resumming the NS-NS tadpoles, hence by an approach that is related to the analysis based on String Field Theory by open-closed duality. We show that, indeed, the positive classical vacuum energy of a Dp-brane of the bosonic string is exactly canceled by the negative contribution arising from tree-level tadpole resummation, in complete agreement with Sen's conjecture on open-string tachyon condensation and with the consequent analysis based on String Field Theory. We also show that the vanishing classical vacuum energy of the SO(8192) unoriented bosonic open-string theory does not receive any tree-level corrections from the tadpole resummation. This result is consistent with the fact that this (unstable) configuration is free from tadpoles of massless closed-string modes, although there is a tadpole of the closed string tachyon. The application of this method to superstring models with broken supersymmetry is also discussed

String bit models for superstring

International Nuclear Information System (INIS)

Bergman, O.; Thorn, C.B.

1995-01-01

The authors extend the model of string as a polymer of string bits to the case of superstring. They mainly concentrate on type II-B superstring, with some discussion of the obstacles presented by not II-B superstring, together with possible strategies for surmounting them. As with previous work on bosonic string work within the light-cone gauge. The bit model possesses a good deal less symmetry than the continuous string theory. For one thing, the bit model is formulated as a Galilei invariant theory in (D - 2) + 1 dimensional space-time. This means that Poincare invariance is reduced to the Galilei subgroup in D - 2 space dimensions. Naturally the supersymmetry present in the bit model is likewise dramatically reduced. Continuous string can arise in the bit models with the formation of infinitely long polymers of string bits. Under the right circumstances (at the critical dimension) these polymers can behave as string moving in D dimensional space-time enjoying the full N = 2 Poincare supersymmetric dynamics of type II-B superstring

String bit models for superstring

Energy Technology Data Exchange (ETDEWEB)

Bergman, O.; Thorn, C.B.

1995-12-31

The authors extend the model of string as a polymer of string bits to the case of superstring. They mainly concentrate on type II-B superstring, with some discussion of the obstacles presented by not II-B superstring, together with possible strategies for surmounting them. As with previous work on bosonic string work within the light-cone gauge. The bit model possesses a good deal less symmetry than the continuous string theory. For one thing, the bit model is formulated as a Galilei invariant theory in (D {minus} 2) + 1 dimensional space-time. This means that Poincare invariance is reduced to the Galilei subgroup in D {minus} 2 space dimensions. Naturally the supersymmetry present in the bit model is likewise dramatically reduced. Continuous string can arise in the bit models with the formation of infinitely long polymers of string bits. Under the right circumstances (at the critical dimension) these polymers can behave as string moving in D dimensional space-time enjoying the full N = 2 Poincare supersymmetric dynamics of type II-B superstring.

String-math 2012

CERN Document Server

Katz, Sheldon; Klemm, Albrecht; Morrison, David R

2015-01-01

This volume contains the proceedings of the conference String-Math 2012, which was held July 16-21, 2012, at the Hausdorff Center for Mathematics, Universitat Bonn. This was the second in a series of annual large meetings devoted to the interface of mathematics and string theory. These meetings have rapidly become the flagship conferences in the field. Topics include super Riemann surfaces and their super moduli, generalized moonshine and K3 surfaces, the latest developments in supersymmetric and topological field theory, localization techniques, applications to knot theory, and many more. The contributors include many leaders in the field, such as Sergio Cecotti, Matthias Gaberdiel, Rahul Pandharipande, Albert Schwarz, Anne Taormina, Johannes Walcher, Katrin Wendland, and Edward Witten. This book will be essential reading for researchers and students in this area and for all mathematicians and string theorists who want to update themselves on developments in the math-string interface.

Fast Searching in Packed Strings

DEFF Research Database (Denmark)

Bille, Philip

2009-01-01

Given strings P and Q the (exact) string matching problem is to find all positions of substrings in Q matching P. The classical Knuth-Morris-Pratt algorithm [SIAM J. Comput., 1977] solves the string matching problem in linear time which is optimal if we can only read one character at the time....... However, most strings are stored in a computer in a packed representation with several characters in a single word, giving us the opportunity to read multiple characters simultaneously. In this paper we study the worst-case complexity of string matching on strings given in packed representation. Let m...... word-RAM with logarithmic word size we present an algorithm using time O(n/log(sigma) n + m + occ) Here occ is the number of occurrences of P in Q. For m = o(n) this improves the O(n) bound...

Comparing double string theory actions

International Nuclear Information System (INIS)

De Angelis, L.; Gionti, S.J.G.; Marotta, R.; Pezzella, F.

2014-01-01

Aimed to a deeper comprehension of a manifestly T-dual invariant formulation of string theory, in this paper a detailed comparison between the non-covariant action proposed by Tseytlin and the covariant one proposed by Hull is done. These are obtained by making both the string coordinates and their duals explicitly appear, on the same footing, in the world-sheet action, so “doubling” the string coordinates along the compact dimensions. After a discussion on the nature of the constraints in both the models and the relative quantization, it results that the string coordinates and their duals behave like “non-commuting” phase space coordinates but their expressions in terms of Fourier modes generate the oscillator algebra of the standard bosonic string. A proof of the equivalence of the two formulations is given. Furthermore, open-string solutions are also discussed

Comparing double string theory actions

Energy Technology Data Exchange (ETDEWEB)

De Angelis, L. [Dipartimento di Fisica, Università degli Studi “Federico II” di Napoli,Complesso Universitario Monte S. Angelo ed. 6, via Cintia, 80126 Napoli (Italy); Gionti, S.J.G. [Specola Vaticana, Vatican City, V-00120, Vatican City State and Vatican Observatory Research Group, Steward Observatory, The University Of Arizona, 933 North Cherry Avenue, Tucson, Arizona 85721 (United States); Marotta, R.; Pezzella, F. [Istituto Nazionale di Fisica Nucleare, Sezione di Napoli,Complesso Universitario di Monte S. Angelo ed. 6, via Cintia, 80126 Napoli (Italy)

2014-04-28

Aimed to a deeper comprehension of a manifestly T-dual invariant formulation of string theory, in this paper a detailed comparison between the non-covariant action proposed by Tseytlin and the covariant one proposed by Hull is done. These are obtained by making both the string coordinates and their duals explicitly appear, on the same footing, in the world-sheet action, so “doubling” the string coordinates along the compact dimensions. After a discussion on the nature of the constraints in both the models and the relative quantization, it results that the string coordinates and their duals behave like “non-commuting” phase space coordinates but their expressions in terms of Fourier modes generate the oscillator algebra of the standard bosonic string. A proof of the equivalence of the two formulations is given. Furthermore, open-string solutions are also discussed.

Metastable cosmic strings in realistic models

International Nuclear Information System (INIS)

Holman, R.

1992-01-01

The stability of the electroweak Z-string is investigated at high temperatures. The results show that, while finite temperature corrections can improve the stability of the Z-string, their effect is not strong enough to stabilize the Z-string in the standard electroweak model. Consequently, the Z-string will be unstable even under the conditions present during the electroweak phase transition. Phenomenologically viable models based on the gauge group SU(2) L x SU(2) R x U(1) B-L are then considered, and it is shown that metastable strings exist and are stable to small perturbations for a large region of the parameter space for these models. It is also shown that these strings are superconducting with bosonic charge carriers. The string superconductivity may be able to stabilize segments and loops against dynamical contraction. Possible implications of these strings for cosmology are discussed

Simulation of ideal-gas flow by nitrogen and other selected gases at cryogenic temperatures. [transonic flow in cryogenic wind tunnels

Science.gov (United States)

Hall, R. M.; Adcock, J. B.

1981-01-01

The real gas behavior of nitrogen, the gas normally used in transonic cryogenic tunnels, is reported for the following flow processes: isentropic expansion, normal shocks, boundary layers, and interactions between shock waves and boundary layers. The only difference in predicted pressure ratio between nitrogen and an ideal gas which may limit the minimum operating temperature of transonic cryogenic wind tunnels occur at total pressures approaching 9 atm and total temperatures 10 K below the corresponding saturation temperature. These pressure differences approach 1 percent for both isentropic expansions and normal shocks. Alternative cryogenic test gases were also analyzed. Differences between air and an ideal diatomic gas are similar in magnitude to those for nitrogen and should present no difficulty. However, differences for helium and hydrogen are over an order of magnitude greater than those for nitrogen or air. It is concluded that helium and cryogenic hydrogen would not approximate the compressible flow of an ideal diatomic gas.

Constraints on cosmic strings due to black holes formed from collapsed cosmic string loops

International Nuclear Information System (INIS)

Caldwell, R.R.; Gates, E.

1993-05-01

The cosmological features of primordial black holes formed from collapsed cosmic string loops are studied. Observational restrictions on a population of primordial black holes are used to restrict f, the fraction of cosmic string loops which collapse to form black holes, and μ, the cosmic string mass-per-unit-length. Using a realistic model of cosmic strings, we find the strongest restriction on the parameters f and μ is due to the energy density in 100MeV photons radiated by the black holes. We also find that inert black hole remnants cannot serve as the dark matter. If earlier, crude estimates of f are reliable, our results severely restrict μ, and therefore limit the viability of the cosmic string large-scale structure scenario

String Chopping and Time-ordered Products of Linear String-localized Quantum Fields

Science.gov (United States)

Cardoso, Lucas T.; Mund, Jens; Várilly, Joseph C.

2018-03-01

For a renormalizability proof of perturbative models in the Epstein-Glaser scheme with string-localized quantum fields, one needs to know what freedom one has in the definition of time-ordered products of the interaction Lagrangian. This paper provides a first step in that direction. The basic issue is the presence of an open set of n-tuples of strings which cannot be chronologically ordered. We resolve it by showing that almost all such string configurations can be dissected into finitely many pieces which can indeed be chronologically ordered. This fixes the time-ordered products of linear field factors outside a nullset of string configurations. (The extension across the nullset, as well as the definition of time-ordered products of Wick monomials, will be discussed elsewhere).

Testing of a Spray-Bar Zero Gravity Cryogenic Vent System for Upper Stages

Science.gov (United States)

Lak, Tibor; Flachbart, Robin; Nguyen, Han; Martin, James

1999-01-01

The capability to vent in zero gravity without resettling is a fundamental technology need that involves practically all uses of subcritical cryogenics in space. Venting without resettling would extend cryogenic orbital transfer vehicle capabilities. However, the lack of definition regarding liquid/ullage orientation coupled with the somewhat random nature of the thermal stratification and resulting pressure rise rates, lead to significant technical challenges. Typically a zero gravity vent concept, termed a thermodynamic vent system (TVS), consists of a tank mixer to destratify the propellant, combined with a Joule- Thomson (J-T) valve to extract then-nal energy from the propellant. In a cooperative effort, Marshall Space Flight Center's (MSFC's) Multipurpose Hydrogen Test Bed (N4HTB) was used to test a unique "spray bar" TVS system developed by Boeing. A schematic of this system is included in Figure 1. The system consists of a recirculation pump, a parallel flow concentric tube, heat exchanger, and a spray bar positioned close to the longitudinal axis of the tank. In the mixing mode, the recirculation pump withdraws liquid from the tank and sprays it radially into the tank liquid, ullage, and exposed tank surfaces. When energy extraction is required, a small portion of the recirculated liquid is passed sequentially through the J-T expansion valve, the spray bar heat exchanger element, and is vented overboard. The vented vapor cools the circulated bulk fluid, thereby removing thermal energy and reducing tank pressure. Figure 2 is a plot of ullage pressure (P4) and liquid vapor pressure (PSAI) versus time. The pump operates alone, cycling on and off, to destratify the tank liquid and ullage until the liquid vapor pressure reaches the lower set point. At that point, the J-T valve begins to cycle on and off with the pump. Thus, for short duration missions, only the mixer may operate, thus minimizing or even eliminating boil-off losses. The primary advantage of the

Cryogenics theory, processes and applications

CERN Document Server

Hayes, Allyson E

2011-01-01

Cryogenics is the study of the production of very low temperature (below -150 -C, -238 -F or 123 K) and the behaviour of materials at those temperatures. This book presents current research from across the globe in the study of cryogenics, including the effect of cryogenic treatment on microstructure and mechanical properties of light weight alloys; the application of Fiber Bragg grating sensors at cryogenic temperatures; cryogenic grinding; liquid oxygen magnetohydrodynamics; and, genetic engineering techniques used to improve tolerance to cryopreservation.

Experimental investigation of the piano hammer-string interaction.

Science.gov (United States)

Birkett, Stephen

2013-04-01

Experimental techniques for investigating the piano hammer-string interaction are described. It is argued that the accuracy, consistency, and scope of conclusions of previous studies can be compromised by limitations of the conventional methods relating to key inputs; physical distortion; numerical distortion, particularly when differentiation or integration of measured signals is used to derive primary response variables; contact identification; and synchronization issues. These problems are discussed, and experimental methods that have been devised to avoid them are described and illustrated by detailed results from a study of the hammer-string interaction in a vertical piano. High resolution displacements are obtained directly by non-contact high-speed imaging and quantitative motion tracking. The attention focused on achieving very accurate and consistent temporal and spatial alignment, including the objective procedure used for contact identification, allows meaningful comparisons of responses from separate tests. String motion at the strike point and on each side of it, as well as hammer motion, is obtained for eight dynamic levels from 1.06 to 2.98 m/s impact velocity. Detailed observations of the force-compression behavior of the hammer interacting with real strings are presented. The direct effects of hammer shank deflection and agraffe string pulses on the interaction are also highlighted.

Perspectives on string phenomenology

CERN Document Server

Kane, Gordon; Kumar, Piyush

2015-01-01

The remarkable recent discovery of the Higgs boson at the CERN Large Hadron Collider completed the Standard Model of particle physics and has paved the way for understanding the physics which may lie beyond it. String/M theory has emerged as a broad framework for describing a plethora of diverse physical systems, which includes condensed matter systems, gravitational systems as well as elementary particle physics interactions. If string/M theory is to be considered as a candidate theory of Nature, it must contain an effectively four-dimensional universe among its solutions that is indistinguishable from our own. In these solutions, the extra dimensions of string/M Theory are “compactified” on tiny scales which are often comparable to the Planck length. String phenomenology is the branch of string/M theory that studies such solutions, relates their properties to data, and aims to answer many of the outstanding questions of particle physics beyond the Standard Model. This book contains perspectives on stri...

Cosmic strings and galaxy formation

Science.gov (United States)

Bertschinger, Edmund

1989-01-01

The cosmogonical model proposed by Zel'dovich and Vilenkin (1981), in which superconducting cosmic strings act as seeds for the origin of structure in the universe, is discussed, summarizing the results of recent theoretical investigations. Consideration is given to the formation of cosmic strings, the microscopic structure of strings, gravitational effects, cosmic string evolution, and the formation of galaxies and large-scale structure. Simulation results are presented in graphs, and several outstanding issues are listed and briefly characterized.

On the null origin of the ambitwistor string

Energy Technology Data Exchange (ETDEWEB)

Casali, Eduardo [Mathematical Institute, University of Oxford,Woodstock Road, Oxford, OX2 6GG (United Kingdom); Tourkine, Piotr [Department of Applied Mathematics and Theoretical Physics,Wilberforce Road, Cambridge, CB3 0WA (United Kingdom)

2016-11-07

In this paper we present the null string origin of the ambitwistor string. Classically, the null string is the tensionless limit of string theory, and so too is the ambitwistor string. Both have as constraint algebra the Galilean Conformal Algebra in two dimensions. But something interesting happens in the quantum theory since there is an ambiguity in quantizing the null string. We show that, given a particular choice of quantization scheme and a particular gauge, the null string coincides with the ambitwistor string both classically and quantum mechanically. We also show that the same holds for the spinning versions of the null string and ambitwistor string. With these results we clarify the relationship between the ambitwistor string, the null string, the usual string and the Hohm-Siegel-Zwiebach theory.

High field conditioning of cryogenic RF cavities

International Nuclear Information System (INIS)

Cole, M.; Debiak, T.; Lom, C.; Shephard, W.; Sredniawski, J.

1993-01-01

Space-based and other related accelerators have conditioning and operation requirements that are not found in most machines. The use of cryogenic copper, relatively poor vacuum, and limited power storage and operating time put unusual demands on the high-field conditioning process and present some concerns. Two CW cryogenic engineering model open-quotes sparkerclose quotes cavities have been fabricated and tested to fairly high field levels. Tests included initial and repeated conditioning as well as sustained RF operations. The two cavities were an engineering model TDL and an engineering model RFQ. Both cavities operated at 425 MHz. The DTL was conditioned to 46 MV/m at 100% duty factor (CW) at cryogenic temperature. This corresponds to a gap voltage of 433 kV and a real estate accelerating gradient (energy gain/total cavity length) of 6.97 MV/m. The authors believe this to be record performance for cryo CW operation. During cryo pulsed operation, the same cavity reached 48 MV/m with 200 μsec pulses at 0.5% DF. The RFQ was conditioned to 30 MV/m CW at cryo, 85 kV gap voltage. During a brief period of cryo pulsed operation, the RFQ operated at 46 MV/m, or 125 kV gap voltage. Reconditioning experiments were performed on both cavities and no problems were encountered. It should be noted that the vacuum levels were not very stringent during these tests and no special cleanliness or handling procedures were followed. The results of these tests indicate that cavities can run CW without difficulty at cryogenic temperatures at normal conservative field levels. Higher field operation may well be possible, and if better vacuums are used and more attention is paid to cleanliness, much higher fields may be attainable

The QCD Effective String

International Nuclear Information System (INIS)

Espriu, D.

2003-01-01

QCD can be described in a certain kinematical regime by an effective string theory. This string must couple to background chiral fields in a chirally invariant manner, thus taking into account the true chirally non-invariant QCD vacuum. By requiring conformal symmetry of the string and the unitarity constraint on chiral fields we reconstruct the equations of motion for the latter ones. These provide a consistent background for the propagation of the string. By further requiring locality of the effective action we recover the Lagrangian of non-linear sigma model of pion interactions. The prediction is unambiguous and parameter-free. The estimated chiral structural constants of Gasser and Leutwyler fit very well the phenomenological values. (author)

Design, production, and testing of field effect transistors. [cryogenic MOSFETS

Science.gov (United States)

Sclar, N.

1982-01-01

Cryogenic MOSFETS (CRYOFETS), specifically designed for low temperature preamplifier application with infrared extrinsic detectors were produced and comparatively tested with p-channel MOSFETs under matched conditions. The CRYOFETs exhibit lower voltage thresholds, high source-follower gains at lower bias voltage, and lower dc offset source voltage. The noise of the CRYOFET is found to be 2 to 4 times greater than the MOSFET with a correspondingly lower figure of merit (which is established for source-follower amplifiers). The device power dissipation at a gain of 0.98 is some two orders of magnitude lower than for the MOSFET. Further, CRYOFETs are free of low temperature I vs V character hysteresis and balky conduction turn-on effects and operate effectively in the 2.4 to 20 K range. These devices have promise for use on long term duration sensor missions and for on-focal-plane signal processing at low temperatures.

Minimal string theories and integrable hierarchies

Science.gov (United States)

Iyer, Ramakrishnan

Well-defined, non-perturbative formulations of the physics of string theories in specific minimal or superminimal model backgrounds can be obtained by solving matrix models in the double scaling limit. They provide us with the first examples of completely solvable string theories. Despite being relatively simple compared to higher dimensional critical string theories, they furnish non-perturbative descriptions of interesting physical phenomena such as geometrical transitions between D-branes and fluxes, tachyon condensation and holography. The physics of these theories in the minimal model backgrounds is succinctly encoded in a non-linear differential equation known as the string equation, along with an associated hierarchy of integrable partial differential equations (PDEs). The bosonic string in (2,2m-1) conformal minimal model backgrounds and the type 0A string in (2,4 m) superconformal minimal model backgrounds have the Korteweg-de Vries system, while type 0B in (2,4m) backgrounds has the Zakharov-Shabat system. The integrable PDE hierarchy governs flows between backgrounds with different m. In this thesis, we explore this interesting connection between minimal string theories and integrable hierarchies further. We uncover the remarkable role that an infinite hierarchy of non-linear differential equations plays in organizing and connecting certain minimal string theories non-perturbatively. We are able to embed the type 0A and 0B (A,A) minimal string theories into this single framework. The string theories arise as special limits of a rich system of equations underpinned by an integrable system known as the dispersive water wave hierarchy. We find that there are several other string-like limits of the system, and conjecture that some of them are type IIA and IIB (A,D) minimal string backgrounds. We explain how these and several other string-like special points arise and are connected. In some cases, the framework endows the theories with a non

Worldsheet factorization for twistor-strings

Energy Technology Data Exchange (ETDEWEB)

Adamo, Tim [Department of Applied Mathematics & Theoretical Physics, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA (United Kingdom)

2014-04-10

We study the multiparticle factorization properties of two worldsheet theories which — at tree-level — describe the scattering of massless particles in four dimensions: the Berkovits-Witten twistor-string for N=4 super-Yang-Mills coupled to N=4 conformal supergravity, and the Skinner twistor-string for N=8 supergravity. By considering these string-like theories, we can study factorization at the level of the worldsheet before any Wick contractions or integrals have been performed; this is much simpler than considering the factorization properties of the amplitudes themselves. In Skinner’s twistor-string this entails the addition of worldsheet gravity as well as a formalism that represents all external states in a manifestly symmetric way, which we develop explicitly at genus zero. We confirm that the scattering amplitudes of Skinner’s theory, as well as the gauge theory amplitudes for the planar sector of the Berkovits-Witten theory, factorize appropriately at genus zero. In the non-planar sector, we find behavior indicative of conformal gravity in the Berkovits-Witten twistor-string. We contrast factorization in twistor-strings with the story in ordinary string theory, and also make some remarks on higher genus factorization and disconnected prescriptions.

Worldsheet factorization for twistor-strings

International Nuclear Information System (INIS)

Adamo, Tim

2014-01-01

We study the multiparticle factorization properties of two worldsheet theories which — at tree-level — describe the scattering of massless particles in four dimensions: the Berkovits-Witten twistor-string for N=4 super-Yang-Mills coupled to N=4 conformal supergravity, and the Skinner twistor-string for N=8 supergravity. By considering these string-like theories, we can study factorization at the level of the worldsheet before any Wick contractions or integrals have been performed; this is much simpler than considering the factorization properties of the amplitudes themselves. In Skinner’s twistor-string this entails the addition of worldsheet gravity as well as a formalism that represents all external states in a manifestly symmetric way, which we develop explicitly at genus zero. We confirm that the scattering amplitudes of Skinner’s theory, as well as the gauge theory amplitudes for the planar sector of the Berkovits-Witten theory, factorize appropriately at genus zero. In the non-planar sector, we find behavior indicative of conformal gravity in the Berkovits-Witten twistor-string. We contrast factorization in twistor-strings with the story in ordinary string theory, and also make some remarks on higher genus factorization and disconnected prescriptions

Fermions on the electroweak string

CERN Document Server

Moreno, J M; Quirós, Mariano; Moreno, J M; Oaknin, D H; Quiros, M

1995-01-01

We construct a simple class of exact solutions of the electroweak theory including the naked Z--string and fermion fields. It consists in the Z--string configuration (\\phi,Z_\\theta), the {\\it time} and z components of the neutral gauge bosons (Z_{0,3},A_{0,3}) and a fermion condensate (lepton or quark) zero mode. The Z--string is not altered (no feed back from the rest of fields on the Z--string) while fermion condensates are zero modes of the Dirac equation in the presence of the Z--string background (no feed back from the {\\it time} and z components of the neutral gauge bosons on the fermion fields). For the case of the n--vortex Z--string the number of zero modes found for charged leptons and quarks is (according to previous results by Jackiw and Rossi) equal to |n|, while for (massless) neutrinos is |n|-1. The presence of fermion fields in its core make the obtained configuration a superconducting string, but their presence (as well as that of Z_{0,3},A_{0,3}) does not enhance the stability of the Z--stri...

The STRING database in 2011

DEFF Research Database (Denmark)

Szklarczyk, Damian; Franceschini, Andrea; Kuhn, Michael

2011-01-01

present an update on the online database resource Search Tool for the Retrieval of Interacting Genes (STRING); it provides uniquely comprehensive coverage and ease of access to both experimental as well as predicted interaction information. Interactions in STRING are provided with a confidence score...... models, extensive data updates and strongly improved connectivity and integration with third-party resources. Version 9.0 of STRING covers more than 1100 completely sequenced organisms; the resource can be reached at http://string-db.org....

Racetrack inflation and cosmic strings

Energy Technology Data Exchange (ETDEWEB)

Brax, P. [CEA-Saclay, Gif sur Yvette (France). CEA/DSM/SPhT, Unite de Recherche Associee au CNRS, Service de Physique Theorique; Bruck, C. van de [Sheffield Univ. (United Kingdom). Dept. of Applied Mathematics; Davis, A.C.; Davis, S.C. [Cambridge Univ. (United Kingdom). DAMTP, Centre for Mathematical Sciences; Jeannerot, R. [Instituut-Lorentz for Theoretical Physics, Leiden (Netherlands); Postma, M. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)]|[Nationaal Inst. voor Kernfysica en Hoge-Energiefysica (NIKHEF), Amsterdam (Netherlands)

2008-05-15

We consider the coupling of racetrack inflation to matter fields as realised in the D3/D7 brane system. In particular, we investigate the possibility of cosmic string formation in this system. We find that string formation before or at the onset of racetrack inflation is possible, but they are then inflated away. Furthermore, string formation at the end of inflation is prevented by the presence of the moduli sector. As a consequence, no strings survive racetrack inflation. (orig.)

Racetrack inflation and cosmic strings

International Nuclear Information System (INIS)

Brax, P.; Postma, M.

2008-05-01

We consider the coupling of racetrack inflation to matter fields as realised in the D3/D7 brane system. In particular, we investigate the possibility of cosmic string formation in this system. We find that string formation before or at the onset of racetrack inflation is possible, but they are then inflated away. Furthermore, string formation at the end of inflation is prevented by the presence of the moduli sector. As a consequence, no strings survive racetrack inflation. (orig.)

Geometric derivation of string field theory from first principles: Closed strings and modular invariance

International Nuclear Information System (INIS)

Kaku, M.

1988-01-01

We present an entirely new approach to closed-string field theory, called Igeometric string field theory R, which avoids the complications found in Becchi-Rouet-Stora-Tyutin string field theory (e.g., ghost counting, infinite overcounting of diagrams, midpoints, lack of modular invariance). Following the analogy with general relativity and Yang-Mills theory, we define a new infinite-dimensional local gauge group, called the unified string group, which uniquely specifies the connection fields, the curvature tensor, the measure and tensor calculus, and finally the action itself. Geometric field theory, when gauge fixed, yields an entirely new class of gauges called the interpolating gauge which allows us to smoothly interpolate between the midpoint gauge and the end-point gauge (''covariantized light-cone gauge''). We can show that geometric string field theory reproduces one copy of the Shapiro-Virasoro model. Surprisingly, after the gauge is broken, a new Iclosed four-string interactionR emerges as the counterpart of the instantaneous four-fermion Coulomb term in QED. This term restores modular invariance and precisely fills the missing region of the complex plane

The Rise and Fall of the Cosmic String Theory for Cosmological Perturbations

International Nuclear Information System (INIS)

Perivolaropoulos, L.

2005-01-01

The cosmic string theory for cosmological fluctuations is a good example of healthy scientific progress in cosmology. It is a well defined physically motivated model that has been tested by cosmological observations and has been ruled out as a primary source of primordial fluctuations. Until about fifteen years ago, the cosmic string theory of cosmological perturbations provided one of the two physically motivated candidate theories for the generation of primordial perturbations. The cosmological data that appeared during the last decade have been compared with the well defined predictions of the theory and have ruled out cosmic strings as a primary source of primordial cosmological perturbations. Since cosmic strings are predicted to form after inflation in a wide range of microphysical theories (including supersymmetric and fundamental string theories) their observational bounds may serve a source of serious constraints for these theories. This is a pedagogical review of the historical development, the main predictions of the cosmic string theory and the constraints that have been imposed on it by cosmological observations. Recent lensing events that could be attributed to lighter cosmic strings are also discussed

String theory as a Lilliputian world

International Nuclear Information System (INIS)

Ambjørn, J.; Makeenko, Y.

2016-01-01

Lattice regularizations of the bosonic string do not allow us to probe the tachyon. This has often been viewed as the reason why these theories have never managed to make any contact to standard continuum string theories when the dimension of spacetime is larger than two. We study the continuum string theory in large spacetime dimensions where simple mean field theory is reliable. By keeping carefully the cutoff we show that precisely the existence of a tachyon makes it possible to take a scaling limit which reproduces the lattice-string results. We compare this scaling limit with another scaling limit which reproduces standard continuum-string results. If the people working with lattice regularizations of string theories are akin to Gulliver they will view the standard string-world as a Lilliputian world no larger than a few lattice spacings.

String theory as a Lilliputian world

Energy Technology Data Exchange (ETDEWEB)

Ambjørn, J., E-mail: ambjorn@nbi.dk [The Niels Bohr Institute, Copenhagen University, Blegdamsvej 17, DK-2100 Copenhagen (Denmark); IMAPP, Radboud University, Heyendaalseweg 135, 6525 AJ, Nijmegen (Netherlands); Makeenko, Y., E-mail: makeenko@nbi.dk [The Niels Bohr Institute, Copenhagen University, Blegdamsvej 17, DK-2100 Copenhagen (Denmark); Institute of Theoretical and Experimental Physics, B. Cheremushkinskaya 25, 117218 Moscow (Russian Federation)

2016-05-10

Lattice regularizations of the bosonic string do not allow us to probe the tachyon. This has often been viewed as the reason why these theories have never managed to make any contact to standard continuum string theories when the dimension of spacetime is larger than two. We study the continuum string theory in large spacetime dimensions where simple mean field theory is reliable. By keeping carefully the cutoff we show that precisely the existence of a tachyon makes it possible to take a scaling limit which reproduces the lattice-string results. We compare this scaling limit with another scaling limit which reproduces standard continuum-string results. If the people working with lattice regularizations of string theories are akin to Gulliver they will view the standard string-world as a Lilliputian world no larger than a few lattice spacings.

Relativistic classical strings. II

International Nuclear Information System (INIS)

Galvao, C.A.P.

1985-01-01

The interactions of strings with electromagnetic and gravitational fields are extensively discussed. Some concepts of differential geometry are reviewed. Strings in Kaluza-Klein manifolds are studied. (L.C.) [pt

Cryogenic testing of the 2.1 GHz five-cell superconducting RF cavity with a photonic band gap coupler cell

Science.gov (United States)

Arsenyev, Sergey A.; Temkin, Richard J.; Haynes, W. Brian; Shchegolkov, Dmitry Yu.; Simakov, Evgenya I.; Tajima, Tsuyoshi; Boulware, Chase H.; Grimm, Terrence L.; Rogacki, Adam R.

2016-05-01

We present results from cryogenic tests of the multi-cell superconducting radio frequency (SRF) cavity with a photonic band gap (PBG) coupler cell. Achieving high average beam currents is particularly desirable for future light sources and particle colliders based on SRF energy-recovery-linacs (ERLs). Beam current in ERLs is limited by the beam break-up instability, caused by parasitic higher order modes (HOMs) interacting with the beam in accelerating cavities. A PBG cell incorporated in an accelerating cavity can reduce the negative effect of HOMs by providing a frequency selective damping mechanism, thus allowing significantly higher beam currents. The multi-cell cavity was designed and fabricated of niobium. Two cryogenic (vertical) tests were conducted. The high unloaded Q-factor was demonstrated at a temperature of 4.2 K at accelerating gradients up to 3 MV/m. The measured value of the unloaded Q-factor was 1.55 × 108, in agreement with prediction.

Cylindrically symmetric, static strings with a cosmological constant in Brans-Dicke theory

International Nuclear Information System (INIS)

Delice, Oezguer

2006-01-01

The static cylindrically symmetric vacuum solutions with a cosmological constant in the framework of the Brans-Dicke theory are investigated. Some of these solutions admitting Lorentz boost invariance along the symmetry axis correspond to local, straight cosmic strings with a cosmological constant. Some physical properties of such solutions are studied. These strings apply attractive or repulsive forces on the test particles. A smooth matching is also performed with a recently introduced interior thick string solution with a cosmological constant

A rotating string

International Nuclear Information System (INIS)

Jensen, B.

1993-06-01

The author presents a global solution of Einstein's equations which represents a rotating cosmic string with a finite coreradius. The importance of pressure for the generation of closed timelike curves outside the coreregion of such strings is clearly displayed in this model due to the simplicity of the source. 10 refs

Performance Testing of Hydrodesulfurization Catalysts Using a Single-Pellet-String Reactor

NARCIS (Netherlands)

Moonen, Roel; Ras, Erik Jan; Harvey, Clare; Alles, Jeroen; Moulijn, J.A.

2017-01-01

Small-scale parallel trickle-bed reactors were used to evaluate the performance of a commercial hydrodesulfurization catalyst under industrially relevant conditions. Catalyst extrudates were loaded as a single string in reactor tubes. It is demonstrated that product sulfur levels and densities

The ABCDEFG of Little Strings

OpenAIRE

Haouzi, Nathan; Kozçaz, Can

2017-01-01

Starting from type IIB string theory on an $ADE$ singularity, the (2,0) little string arises when one takes the string coupling $g_s$ to 0. In this setup, we give a unified description of the codimension-two defects of the little string, for any simple Lie algebra ${\\mathfrak{g}}$. Geometrically, these are D5 branes wrapping 2-cycles of the singularity. Equivalently, the defects are specified by a certain set of weights of $^L {\\mathfrak{g}}$, the Langlands dual of ${\\mathfrak{g}}$. As a firs...

Open problems in string cosmology

International Nuclear Information System (INIS)

Toumbas, N.

2010-01-01

Some of the open problems in string cosmology are highlighted within the context of the recently constructed thermal and quantum superstring cosmological solutions. Emphasis is given on the high temperature cosmological regime, where it is argued that thermal string vacua in the presence of gravito-magnetic fluxes can be used to bypass the Hagedorn instabilities of string gas cosmology. This article is based on a talk given at the workshop on ''Cosmology and Strings'', Corfu, September 6-13, 2009. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

Strings, conformal fields and topology

International Nuclear Information System (INIS)

Kaku, Michio

1991-01-01

String Theory has advanced at an astonishing pace in the last few years, and this book aims to acquaint the reader with the most active topics of research in the field. Building on the foundations laid in his Introduction to Superstrings, Professor Kaku discusses such topics as the classification of conformal string theories, knot theory, the Yang-Baxter relation, quantum groups, the non-polynominal closed string field theory, matrix models, and topological field theory. Several chapters review the fundamentals of string theory, making the presentation of the material self-contained while keeping overlap with the earlier book to a minimum. The book conveys the vitality of current research in string theory and places readers at its forefront. (orig.) With 40 figs. in 50 parts

Basic concepts of string theory

International Nuclear Information System (INIS)

Blumenhagen, Ralph

2013-01-01

The purpose of this book is to thoroughly prepare the reader for research in string theory. It is intended as a textbook in the sense that, starting from the basics, the material is presented in a pedagogical and self-contained fashion. The emphasis is on the world-sheet perspective of closed strings and of open strings ending on D-branes, where two-dimensional conformal field theory is the main tool. Compactifications of string theory, with and without fluxes, and string dualities are also discussed from the space-time point of view, i.e. in geometric language. End-of-chapter references have been added to guide the reader intending to pursue further studies or to start research in the topics covered by this book.

String fragmentation; La fragmentation des cordes

Energy Technology Data Exchange (ETDEWEB)

Drescher, H.J.; Werner, K. [Laboratoire de Physique Subatomique et des Technologies Associees - SUBATECH, Centre National de la Recherche Scientifique, 44 - Nantes (France)

1997-10-01

The classical string model is used in VENUS as a fragmentation model. For the soft domain simple 2-parton strings were sufficient, whereas for higher energies up to LHC, the perturbative regime of the QCD gives additional soft gluons, which are mapped on the string as so called kinks, energy singularities between the leading partons. The kinky string model is chosen to handle fragmentation of these strings by application of the Lorentz invariant area law. The `kinky strings` model, corresponding to the perturbative gluons coming from pQCD, takes into consideration this effect by treating the partons and gluons on the same footing. The decay law is always the Artru-Menessier area law which is the most realistic since it is invariant to the Lorentz and gauge transformations. For low mass strings a manipulation of the rupture point is necessary if the string corresponds already to an elementary particle determined by the mass and the flavor content. By means of the fragmentation model it will be possible to simulate the data from future experiments at LHC and RHIC 3 refs.

Querying and Mining Strings Made Easy

KAUST Repository

Sahli, Majed

2017-10-13

With the advent of large string datasets in several scientific and business applications, there is a growing need to perform ad-hoc analysis on strings. Currently, strings are stored, managed, and queried using procedural codes. This limits users to certain operations supported by existing procedural applications and requires manual query planning with limited tuning opportunities. This paper presents StarQL, a generic and declarative query language for strings. StarQL is based on a native string data model that allows StarQL to support a large variety of string operations and provide semantic-based query optimization. String analytic queries are too intricate to be solved on one machine. Therefore, we propose a scalable and efficient data structure that allows StarQL implementations to handle large sets of strings and utilize large computing infrastructures. Our evaluation shows that StarQL is able to express workloads of application-specific tools, such as BLAST and KAT in bioinformatics, and to mine Wikipedia text for interesting patterns using declarative queries. Furthermore, the StarQL query optimizer shows an order of magnitude reduction in query execution time.

First quantized noncritical relativistic Polyakov string

International Nuclear Information System (INIS)

Jaskolski, Z.; Meissner, K.A.

1994-01-01

The first quantization of the relativistic Brink-DiVecchia-Howe-Polyakov (BDHP) string in the range 1 < d 25 is considered. It is shown that using the Polyakov sum over bordered surfaces in the Feynman path integral quantization scheme one gets a consistent quantum mechanics of relativistic 1-dim extended objects in the range 1 < d < 25. In particular, the BDHP string propagator is exactly calculated for arbitrary initial and final string configurations and the Hilbert space of physical states of noncritical BDHP string is explicitly constructed. The resulting theory is equivalent to the Fairlie-Chodos-Thorn massive string model. In contrast to the conventional conformal field theory approach to noncritical string and random surfaces in the Euclidean target space the path integral formulation of the Fairlie-Chodos-Thorn string obtained in this paper does not rely on the principle of conformal invariance. Some consequences of this feature for constructing a consistent relativistic string theory based on the ''splitting-joining'' interaction are discussed. (author). 42 refs, 1 fig

The Management of Cryogens at CERN

CERN Document Server

Delikaris, D; Passardi, Giorgio; Serio, L; Tavian, L

2005-01-01

CERN is a large user of industrially procured cryogens essentially liquid helium and nitrogen. Recent contracts have been placed by the Organization for the delivery of quantities up to 280 tons of liquid helium over four years and up to 50000 tons of liquid nitrogen over three years. Main users are the very large cryogenic system of the LHC accelerator complex, the physics experiments using superconducting magnets and liquefied gases and all the related test facilities whether industrial or laboratory scale. With the commissioning of LHC, the need of cryogens at CERN will considerably increase and the procurement policy must be adapted accordingly. In this paper, we discuss procurement strategy for liquid helium and nitrogen, including delivery rates, distribution methods and adopted safety standards. Global turnover, on site re-liquefaction capacity, operational consumption, accidental losses, purification means and storage capacity will be described. Finally, the short to medium term evolution of the Orga...

Technical presentation: BGM Cryogenic Engineering Limited

CERN Multimedia

Caroline Laignel - FI Department

2006-01-01

13 - 14 June 2006 TECHNICAL PRESENTATION BGM Cryogenic Engineering Limited 09:00 - 18:00, 60-2-016, Main Building. Presentation on BGM: 11:00 - 12:00, 60-2-016, Main Building. BGM Cryogenic Engineering Limited manufactures assemblies, sub-assemblies and machined components for the cryogenic technology sector. The primary markets served include superconducting magnets used in the healthcare sector (eg MRI body scanners), spectroscopy and NMR equipment for numerous R & D and technology applications, high vacuum applications and particle physics research. BGM has specialist assembly capability including stainless steel and aluminium welding, vacuum testing, electromechanical assembly and metal finishing. BGM offers a ‘one stop shop'facility to satisfy any customer requirement. Through our design partner we can offer a full design and modelling service, including 3D modelling and production of 2D drawings on your own borders. We can conduct heat load and force calculations and advise on the best...

Functional integral approach to string theories

International Nuclear Information System (INIS)

Sakita, B.

1987-01-01

Fermionic string theory can be made supersymmetric: the superstring. It contains among others mass zero gauge fields of spin 1 and 2. The recent revival of interests in string field theories is due to the recognition of the compactified superstring theory as a viable theory of grandunification of all interactions, especially after Green and Schwarz's discovery of the gauge and gravitational anomaly cancellation in 0(32) superstring theory. New developments include string phenomenology, general discussions of compactification, new models, especially the heterotic string. These are either applications or extensions of string field theories. Although these are very exciting developments, the author limits his attention to the basics of the bosonic string theory

Proposal to negotiate, without competitive tendering, a contract for the manufacture, testing and delivery of 320 cryogenic helium mass flowmeters for the LHC

CERN Document Server

2001-01-01

This document concerns the manufacture, testing and delivery of 320 cryogenic helium mass flowmeters for the LHC. Following a market survey (MS-2602/LHC/LHC) carried out amoung 37 firms in twelve Member States and six firms in two non-Member States, a price enquiry for qualifying prototypes was sent on 20 November 1998 to nine selected firms and the received prototypes were evaluated. As a result of this process a request for quotation was sent to one firm The Finance Committee is invited to agree to the negotiation of a contract with the firm EMERSON PROCESS MANAGEMENT/FISHER-ROSEMOUNT (CH), without competitive tendering, for the manufacture, testing and delivery of 320 cryogenic helium mass flowmeters for an amount of 1 804 840 Swiss francs, not subject to revision, with options for up to 10 additional cryogenic helium mass flowmeters and an extension of the guarantee period to five years for all units for an amount of 219 090 Swiss francs, not subject to revision, bringing the total amount to 2 023 930 Swi...

Black string in dRGT massive gravity

Energy Technology Data Exchange (ETDEWEB)

Tannukij, Lunchakorn [Mahidol University, Department of Physics, Faculty of Science, Bangkok (Thailand); Hanyang University, Department of Physics, Seoul (Korea, Republic of); Naresuan University, The Institute for Fundamental Study, Phitsanulok (Thailand); Wongjun, Pitayuth [Naresuan University, The Institute for Fundamental Study, Phitsanulok (Thailand); Ministry of Education, Thailand Center of Excellence in Physics, Bangkok (Thailand); Ghosh, Suchant G. [Jamia Millia Islamia, Centre of Theoretical Physics, New Delhi (India); University of Kwazulu-Natal, Astrophysics and Cosmology Research Unit, School of Mathematical Sciences, Durban (South Africa)

2017-12-15

We present a cylindrically symmetric solution, both charged and uncharged, which is known as a black string solution to the nonlinear ghost-free massive gravity found by de Rham, Gabadadze, and Tolley (dRGT). This ''dRGT black string'' can be thought of as a generalization of the black string solution found by Lemos. Moreover, the dRGT black string solution includes other classes of black string solution such as the monopole-black string ones since the graviton mass contributes to the global monopole term as well as the cosmological-constant term. To investigate the solution, we compute mass, temperature, and entropy of the dRGT black string. We found that the existence of the graviton mass drastically affects the thermodynamics of the black string. Furthermore, the Hawking-Page phase transition is found to be possible for the dRGT black string as well as the charged dRGT black string. The dRGT black string solution is thermodynamically stable for r > r{sub c} with negative thermodynamical potential and positive heat capacity while it is unstable for r < r{sub c} where the potential is positive. (orig.)

Strings and quantum gravity

International Nuclear Information System (INIS)

Vega, H.J. de

1990-01-01

One of the main challenges in theoretical physics today is the unification of all interactions including gravity. At present, string theories appear as the most promising candidates to achieve such a unification. However, gravity has not completely been incorporated in string theory, many technical and conceptual problems remain and a full quantum theory of gravity is still non-existent. Our aim is to properly understand strings in the context of quantum gravity. Attempts towards this are reviewed. (author)

Introduction to cryogenic engineering

CERN Multimedia

CERN. Geneva; Vandoni, Giovanna; Niinikoski, Tapio O

2005-01-01

Cryogenic engineering is one of the key technologies at CERN. It is widely used in research and has many applications in industry and last but not least in medicine. In research cryogenic engineering and its applications are omnipresent from the smallest laboratories to fusion reactors, hughe detectors and accelerators. With the termination of the LHC, CERN will in fact become the world's largest cryogenic installation. This series of talks intends to introduce the non-cryogenist to the basic principles and challenges of cryogenic engineering and its applications. The course will also provide a basis for practical application as well as for further learning.

Magnetic strings

International Nuclear Information System (INIS)

Chaves, Max

2006-01-01

The conception of the magnetic string is presented as an infinitely thin bundle of magnetic flux lines. The magnetic strings are surrounded by a film of current that rotates around them, and are a solution of Maxwell's equations. The magnetic potential contains a line singularity, and its stability can be established topologically. A few comments are added on the possibility that they may exist at a cosmological scale as relics of the Big Bang. (author) [es

String Theory in a Nutshell

CERN Document Server

Kiritsis, Elias

2007-01-01

This book is the essential new introduction to modern string theory, by one of the world's authorities on the subject. Concise, clearly presented, and up-to-date, String Theory in a Nutshell brings together the best understood and most important aspects of a theory that has been evolving since the early 1980s. A core model of physics that substitutes one-dimensional extended ""strings"" for zero-dimensional point-like particles (as in quantum field theory), string theory has been the leading candidate for a theory that would successfully unify all fundamental forces of nature, includin

Open bosonic string in background electromagnetic field

International Nuclear Information System (INIS)

Nesterenko, V.V.

1987-01-01

The classical and quantum dynamics of an open string propagating in the D-dimensional space-time in the presence of a background electromagnetic field is investigated. An important point in this consideration is the use of the generalized light-like gauge. There are considered the strings of two types; the neutral strings with charges at their ends obeying the condition q 1 +q 2 =0 and the charged strings having a net charge q 1 +q 2 ≠ 0. The consistency of theory demands that the background electric field does not exceed its critical value. The distance between the mass levels of the neutral open string decreases (1-e 2 ) times in comparison with the free string, where e is the dimensionless strength of the electric field. The magnetic field does not affect this distance. It is shown that at a classical level the squared mass of the neutral open string has a tachyonic contribution due to the motion of the string as a whole in transverse directions. The tachyonic term disappears if one considers, instead of M 2 , the string energy in a special reference frame where the projection of the total canonical momentum of the string onto the electric field vanishes. The contributions due to zero point fluctuations to the energy spectrum of the neutral string and to the Virasoro operators in the theory of charged string are found

A high field and cryogenic test facility for neutron irradiated superconducting wire

Science.gov (United States)

Nishimura, A.; Miyata, H.; Yoshida, M.; Iio, M.; Suzuki, K.; Nakamoto, T.; Yamazaki, M.; Toyama, T.

2017-12-01

A 15.5 T superconducting magnet and a variable temperature insert (VTI) system were installed at a radiation control area in Oarai center in Tohoku University to investigate the superconducting properties of activated superconducting materials by fast neutron. The superconductivity was measured at cryogenic temperature and high magnetic field. During these tests, some inconvenient problems were observed and the additional investigation was carried out. The variable temperature insert was designed and assembled to perform the superconducting property tests. without the liquid helium. To remove the heat induced by radiation and joule heating, high purity aluminum rod was used in VTI. The thermal contact was checked by FEM analysis and an additional support was added to confirm the decreasing the stress concentration and the good thermal contact. After the work for improvement, it was affirmed that the test system works well and all troubles were resolved. In this report, the improved technical solution is described and the first data set on the irradiation effect on Nb3Sn wire is presented.

Compressive fatigue tests on a unidirectional glass/polyester composite at cryogenic temperatures

International Nuclear Information System (INIS)

Stone, E.L.; El-Marazki, L.O.; Young, W.C.

1979-01-01

The fatigue testing of a unidirectional glass-reinforced polyester composite at cryogenic temperatures to simulate the cyclic compressive loads of the magnet support struts in a superconductive magnetic energy storage unit is reported. Right circular cylindrical specimens were tested at 77, 4.2 K and room temperature at different stress levels using a 1-Hz haversine waveform imposed upon a constant baseload in a load-controlled closed-loop electrohydraulic test machine. Two failure modes, uniform mushrooming near one end and a 45 deg fracture line through the middle of the specimen, are observed, with no systematic difference in fatigue life between the modes. Fatigue lives obtained at 77 and 4.2 K are found to be similar, with fatigue failure at 100,000 cycles occurring at stress levels of 70 and 75% of the ultimate compressive strengths of specimens at room temperature and 77 K, respectively. The room temperature fatigue lives of the glass/polyester specimens are found to be intermediate between those reported for glass/epoxy composites with different glass contents costing over twice as much

Casimir energy of a nonuniform string

Science.gov (United States)

Hadasz, L.; Lambiase, G.; Nesterenko, V. V.

2000-07-01

The Casimir energy of a nonuniform string built up from two pieces with different speeds of sound is calculated. A standard procedure of subtracting the energy of an infinite uniform string is applied, the subtraction being interpreted as the renormalization of the string tension. It is shown that in the case of a homogeneous string this method is completely equivalent to zeta renormalization.

From the currency rate quotations onto strings and brane world scenarios

Science.gov (United States)

Horváth, D.; Pincak, R.

2012-11-01

In the paper, we study the projections of the real exchange rate dynamics onto the string-like topology. Our approach is inspired by the contemporary movements in the string theory. The string map of data is defined here by the boundary conditions, characteristic length, real valued and the method of redistribution of information. As a practical matter, this map represents the detrending and data standardization procedure. We introduced maps onto 1-end-point and 2-end-point open strings that satisfy the Dirichlet and Neumann boundary conditions. The questions of the choice of extra-dimensions, symmetries, duality and ways to the partial compactification are discussed. Subsequently, we pass to higher dimensional and more complex objects. The 2D-Brane was suggested which incorporated bid-ask spreads. Polarization by the spread was considered which admitted analyzing arbitrage opportunities on the market where transaction costs are taken into account. The model of the rotating string which naturally yields calculation of angular momentum is suitable for tracking of several currency pairs. The systematic way which allows one suggest more structured maps suitable for a simultaneous study of several currency pairs was analyzed by means of the Gâteaux generalized differential calculus. The effect of the string and brane maps on test data was studied by comparing their mean statistical characteristics. The study revealed notable differences between topologies. We review the dependence on the characteristic string length, mean fluctuations and properties of the intra-string statistics. The study explores the coupling of the string amplitude and volatility. The possible utilizations of the string theory approach in financial markets are slight.

Cryogenic and radiation hard ASIC design for large format NIR/SWIR detector

Science.gov (United States)

Gao, Peng; Dupont, Benoit; Dierickx, Bart; Müller, Eric; Verbruggen, Geert; Gielis, Stijn; Valvekens, Ramses

2014-10-01

An ASIC is developed to control and data quantization for large format NIR/SWIR detector arrays. Both cryogenic and space radiation environment issue are considered during the design. Therefore it can be integrated in the cryogenic chamber, which reduces significantly the vast amount of long wires going in and out the cryogenic chamber, i.e. benefits EMI and noise concerns, as well as the power consumption of cooling system and interfacing circuits. In this paper, we will describe the development of this prototype ASIC for image sensor driving and signal processing as well as the testing in both room and cryogenic temperature.

A Note on Tensionless Strings in M-Theory

OpenAIRE

Davis, K.

1996-01-01

In this article we examine the appearance of tensionless strings in M-Theory. We subsequently interpret these tensionless strings in a String Theory context. In particular, we examine tensionless strings appearing in M-Theory on $S^{1}$, M-Theory on $S^{1} / {\\bf Z}_{2}$, and M-Theory on $T^{2}$; we then interpret the appearance of such strings in a String Theory context. Then we reverse this process and examine the appearance of some tensionless strings in String Theory. Subsequently we inte...

Open strings in the SL(2, R) WZWN model with solution for a rigidly rotating string

DEFF Research Database (Denmark)

Lomholt, Michael Andersen; Larsen, A.L.

2003-01-01

Boundary conditions and gluing conditions for open strings and D-branes in the SL(2, R) WZWN model, corresponding to AdS , are discussed. Some boundary conditions and gluing conditions previously considered in the literature are shown to be incompatible with the variation principle. We then consi......Boundary conditions and gluing conditions for open strings and D-branes in the SL(2, R) WZWN model, corresponding to AdS , are discussed. Some boundary conditions and gluing conditions previously considered in the literature are shown to be incompatible with the variation principle. We...... then consider open string boundary conditions corresponding to a certain field-dependent gluing condition. This allows us to consider open strings with constant energy and angular momentum. Classically, these open strings naturally generalize the open strings in flat Minkowski space. For rigidly rotating open...

Poisson hierarchy of discrete strings

International Nuclear Information System (INIS)

Ioannidou, Theodora; Niemi, Antti J.

2016-01-01

The Poisson geometry of a discrete string in three dimensional Euclidean space is investigated. For this the Frenet frames are converted into a spinorial representation, the discrete spinor Frenet equation is interpreted in terms of a transfer matrix formalism, and Poisson brackets are introduced in terms of the spinor components. The construction is then generalised, in a self-similar manner, into an infinite hierarchy of Poisson algebras. As an example, the classical Virasoro (Witt) algebra that determines reparametrisation diffeomorphism along a continuous string, is identified as a particular sub-algebra, in the hierarchy of the discrete string Poisson algebra. - Highlights: • Witt (classical Virasoro) algebra is derived in the case of discrete string. • Infinite dimensional hierarchy of Poisson bracket algebras is constructed for discrete strings. • Spinor representation of discrete Frenet equations is developed.

Basic Concepts of String Theory

CERN Document Server

Blumenhagen, Ralph; Theisen, Stefan

2013-01-01

The purpose of this book is to thoroughly prepare the reader for research in string theory. It is intended as a textbook in the sense that, starting from the basics, the material is presented in a pedagogical and self-contained fashion. The emphasis is on the world-sheet perspective of closed strings and of open strings ending on D-branes, where two-dimensional conformal field theory is the main tool. Compactifications of string theory, with and without fluxes, and string dualities are also discussed from the space-time point of view, i.e. in geometric language. End-of-chapter references have been added to guide the reader intending to pursue further studies or to start research in the topics covered by this book.

Poisson hierarchy of discrete strings

Energy Technology Data Exchange (ETDEWEB)

Ioannidou, Theodora, E-mail: ti3@auth.gr [Faculty of Civil Engineering, School of Engineering, Aristotle University of Thessaloniki, 54249, Thessaloniki (Greece); Niemi, Antti J., E-mail: Antti.Niemi@physics.uu.se [Department of Physics and Astronomy, Uppsala University, P.O. Box 803, S-75108, Uppsala (Sweden); Laboratoire de Mathematiques et Physique Theorique CNRS UMR 6083, Fédération Denis Poisson, Université de Tours, Parc de Grandmont, F37200, Tours (France); Department of Physics, Beijing Institute of Technology, Haidian District, Beijing 100081 (China)

2016-01-28

The Poisson geometry of a discrete string in three dimensional Euclidean space is investigated. For this the Frenet frames are converted into a spinorial representation, the discrete spinor Frenet equation is interpreted in terms of a transfer matrix formalism, and Poisson brackets are introduced in terms of the spinor components. The construction is then generalised, in a self-similar manner, into an infinite hierarchy of Poisson algebras. As an example, the classical Virasoro (Witt) algebra that determines reparametrisation diffeomorphism along a continuous string, is identified as a particular sub-algebra, in the hierarchy of the discrete string Poisson algebra. - Highlights: • Witt (classical Virasoro) algebra is derived in the case of discrete string. • Infinite dimensional hierarchy of Poisson bracket algebras is constructed for discrete strings. • Spinor representation of discrete Frenet equations is developed.

String theory and quantum gravity '92

International Nuclear Information System (INIS)

Harvey, J.; Iengo, R.; Narain, K.S.; Randjbar Daemi, S.; Verlinde, H.

1993-01-01

These proceedings of the 1992 Trieste Spring School and Workshop on String Theory and Quantum Gravity contains introductions and overviews of recent work on the use of two-dimensional string inspired models in the study of black holes, a lecture on gravitational scattering at planckian energies, another on the physical properties of higher-dimensional black holes and black strings in string theory, a discussion on N=2 superconformal field theories, a lecture about the application of matrix model techniques to the study of string theory in two dimensions, and an overview of the current status and developments in string field theory. Connections with models in statistical mechanics are also discussed. These proceedings contain seven lectures and ten contributions. Refs and figs

MFTF magnet cryogenics

International Nuclear Information System (INIS)

VanSant, J.H.

1981-07-01

The prime requirement of the cryogenics of the magnets is to assure a superconducting state for the magnet coils, a large task considering their enormous size. The following presentation addresses the principal topics that have been considered in this cryogenic design

Introduction to conformal field theory. With applications to string theory

International Nuclear Information System (INIS)

Blumenhagen, Ralph; Plauschinn, Erik

2009-01-01

Based on class-tested notes, this text offers an introduction to Conformal Field Theory with a special emphasis on computational techniques of relevance for String Theory. It introduces Conformal Field Theory at a basic level, Kac-Moody algebras, one-loop partition functions, Superconformal Field Theories, Gepner Models and Boundary Conformal Field Theory. Eventually, the concept of orientifold constructions is explained in detail for the example of the bosonic string. In providing many detailed CFT calculations, this book is ideal for students and scientists intending to become acquainted with CFT techniques relevant for string theory but also for students and non-specialists from related fields. (orig.)

Strings and superstrings. Electron linear colliders

International Nuclear Information System (INIS)

Alessandrini, V.; Bambade, P.; Binetruy, P.; Kounnas, C.; Le Duff, J.; Schwimmer, A.

1989-01-01

Basic string theory; strings in interaction; construction of strings and superstrings in arbitrary space-time dimensions; compactification and phenomenology; linear e+e- colliders; and the Stanford linear collider were discussed [fr

Dynamical evolution of cosmic strings

International Nuclear Information System (INIS)

Bouchet, F.R.

1988-01-01

The author have studied by means of numerical simulations the dynamical evolution of a network of cosmic strings, both in the radiation and matter era. Our basic conclusion is that a scaling solution exists, i.e., the string energy density evolves as t -2 . This means that the process by which long strings dump their energy into closed loops (which can gravitationally radiate away) is efficient enough to prevent the string domination over other forms of energy. This conclusion does not depend on the initial string energy density, nor on the various numerical parameters. On the other hand, the generated spectrum of loop sizes does depend on the value of our numerical lower cutoff (i.e., the minimum length of loop we allow to be chopped off the network). Furthermore, the network evolution is very different from what was assumed before), namely the creation of a few horizon sized loops per horizon volume and per hubble time, which subsequently fragment into about 10 smaller daughter loops. Rather, many tiny loops are directly cut from the network of infinite strings, and it appears that the only fundamental scale (the horizon) has been lost. This is probably because a fundamental ingredient had been overlooked, namely the kinks. These kinks are created in pairs at each intercommutation, and very rapidly, the long strings appear to be very kinky. Thus the number of long strings per horizon is still of the order of a few, but their total length is fairly large. Furthermore, a large number of kinks favors the formation of small loops, and their sizes might well be governed by the kink density along the long strings. Finally, we computed the two-point correlation function of the loops and found significant differences from the work of Turok

Fast searching in packed strings

DEFF Research Database (Denmark)

Bille, Philip

2011-01-01

Given strings P and Q the (exact) string matching problem is to find all positions of substrings in Q matching P. The classical Knuth–Morris–Pratt algorithm [SIAM J. Comput. 6 (2) (1977) 323–350] solves the string matching problem in linear time which is optimal if we can only read one character...... at the time. However, most strings are stored in a computer in a packed representation with several characters in a single word, giving us the opportunity to read multiple characters simultaneously. In this paper we study the worst-case complexity of string matching on strings given in packed representation....... Let m⩽n be the lengths P and Q, respectively, and let σ denote the size of the alphabet. On a standard unit-cost word-RAM with logarithmic word size we present an algorithm using timeO(nlogσn+m+occ). Here occ is the number of occurrences of P in Q. For m=o(n) this improves the O(n) bound of the Knuth...

Dynamics of strings between walls

International Nuclear Information System (INIS)

Eto, Minoru; Fujimori, Toshiaki; Nagashima, Takayuki; Nitta, Muneto; Ohashi, Keisuke; Sakai, Norisuke

2009-01-01

Configurations of vortex strings stretched between or ending on domain walls were previously found to be 1/4 Bogomol'nyi-Prasad-Sommerfield (BPS) states in N=2 supersymmetric gauge theories in 3+1 dimensions. Among zero modes of string positions, the center of mass of strings in each region between two adjacent domain walls is shown to be non-normalizable whereas the rests are normalizable. We study dynamics of vortex strings stretched between separated domain walls by using two methods, the moduli space (geodesic) approximation of full 1/4 BPS states and the charged particle approximation for string end points in the wall effective action. In the first method we explicitly obtain the effective Lagrangian in the strong coupling limit, which is written in terms of hypergeometric functions, and find the 90 deg. scattering for head-on collision. In the second method the domain wall effective action is assumed to be U(1) N gauge theory, and we find a good agreement between two methods for well-separated strings.

Experimental observation of Bethe strings

Science.gov (United States)

Wang, Zhe; Wu, Jianda; Yang, Wang; Bera, Anup Kumar; Kamenskyi, Dmytro; Islam, A. T. M. Nazmul; Xu, Shenglong; Law, Joseph Matthew; Lake, Bella; Wu, Congjun; Loidl, Alois

2018-02-01

Almost a century ago, string states—complex bound states of magnetic excitations—were predicted to exist in one-dimensional quantum magnets. However, despite many theoretical studies, the experimental realization and identification of string states in a condensed-matter system have yet to be achieved. Here we use high-resolution terahertz spectroscopy to resolve string states in the antiferromagnetic Heisenberg-Ising chain SrCo2V2O8 in strong longitudinal magnetic fields. In the field-induced quantum-critical regime, we identify strings and fractional magnetic excitations that are accurately described by the Bethe ansatz. Close to quantum criticality, the string excitations govern the quantum spin dynamics, whereas the fractional excitations, which are dominant at low energies, reflect the antiferromagnetic quantum fluctuations. Today, Bethe’s result is important not only in the field of quantum magnetism but also more broadly, including in the study of cold atoms and in string theory; hence, we anticipate that our work will shed light on the study of complex many-body systems in general.

A new approach to strings and superstrings

International Nuclear Information System (INIS)

Sparano, G.

1988-01-01

The subject of this thesis is a new, more general, action principle for strings, superstrings, and extended objects in any number of dimensions. The origin and motivations for this approach can be found in the context of the study of the symmetries of string theories and, more specifically, are related to the application of K.S.K. (Kirillov, Souriau, Kostant) construction to strings. The main results we find are: (A) A classification of string theories analogous to the classification of relativistic point particles as massive, massless and tachionic with or without spin. Nambu-Goto string and Schild null string emerge as special cases of a more general classification of strings. (B) A new method to introduce spin in strings by using a Wess-Zumino term in the action. (C) Several results are obtained through the study of the configuration space which shows a rich topological structure: for the Nambu-Goto string in any number of dimensions it is found the existence of theta states analogous to the theta-vacua of nonabelian gauge theories. For the closed Schild Null string, in four dimensions, this analysis shows Z2 solitons and the possibility of quantizing the system so that the states are spinorial (have half odd integral spin) even though the Lagrangian consists only of bosonic variables. (D) Unlike Nambu-Goto string, the quantization of Schild Null string is consistent in any number of space-time dimensions. Besides these concrete results, the formalism we introduce will hopefully give also new insights in the problem of the hidden symmetries of the string

Hydroball string sensing system

International Nuclear Information System (INIS)

Hurwitz, M.J.; Ekeroth, D.E.; Squarer, D.

1991-01-01

This patent describes a hydroball string sensing system for a nuclear reactor having a core containing a fluid at a fluid pressure. It comprises a tube connectable to the nuclear reactor so that the fluid can flow within the tube at a fluid pressure that is substantially the same as the fluid pressure of the nuclear reactor core; a hydroball string including - a string member having objects positioned therealong with a specified spacing, the object including a plurality of hydroballs, and bullet members positioned at opposing ends of the string member; first sensor means, positioned outside a first segment of the tube, for sensing one of the objects being positioned within the first segment, and for providing a sensing signal responsive to the sensing of the first sensing means

Field theory of strings

International Nuclear Information System (INIS)

Ramond, P.

1987-01-01

We review the construction of the free equations of motion for open and closed strings in 26 dimensions, using the methods of the Florida Group. Differing from previous treatments, we argue that the constraint L 0 -anti L 0 =0 should not be imposed on all the fields of the closed string in the gauge invariant formalism; we show that it can be incorporated in the gauge invariant formalism at the price of being unable to extract the equations of motion from a Langrangian. We then describe our purely algebraic method to introduce interactions, which works equally well for open and closed strings. Quartic interactions are absent except in the Physical Gauge. Finally, we speculate on the role of the measure of the open string path functional. (orig.)

The cryogenic control system of EAST

International Nuclear Information System (INIS)

Zhuang, M.; Hu, L.B.; Zhow, Z.W.; Xia, G.H.

2012-01-01

Highlights: ► A reliable and flexible duplex control system is required for cryogenic system. ► The cryogenic control system is based on Delta-V DCS. ► It has been proved to be an effective way to control cryogenic process. ► It will provide useful experience and inspiration for the development in the cryogenic control engineering. - Abstract: A large scale helium cryogenic system is one of the key components for the EAST tokamak device for the cooling of PF and TF coils, structures, thermal shields, buslines, current leads and cryopumps. Since the cooling scheme of the EAST cryogenic system is fairly complicated, a reliable and flexible control system is required for cryogenic system. The cryogenic control system is based on DeltaV DCS which is the process control software developed by Emerson Company. The EAST cryogenic system has been in operation for four years and has been proved to be safe, stable and energy saving by the past 7 experiments. This paper describes the redundant control network, hardware configuration, software structure, auxiliary system and the new development in the future.

Cryogenic Preamplifiers for Magnetic Resonance Imaging

DEFF Research Database (Denmark)

Johansen, Daniel H.; Sanchez-Heredia, Juan D.; Petersen, Jan R.

2018-01-01

Pursuing the ultimate limit of detection in magnetic resonance imaging (MRI) requires cryogenics to decrease the thermal noise of the electronic circuits. As cryogenic coils for MRI are slowly emerging cryogenic preamplifiers are required to fully exploit their potential. A cryogenic preamplifier...

String theory in four dimensions

CERN Document Server

1988-01-01

``String Theory in Four Dimensions'' contains a representative collection of papers dealing with various aspects of string phenomenology, including compactifications on smooth manifolds and more general conformal field theories. Together with the lucid introduction by M. Dine, this material gives the reader a good working knowledge of our present ideas for connecting string theory to nature.

A water blown urethane insulation for use in cryogenic environments

Science.gov (United States)

Blevins, Elana; Sharpe, Jon

1995-01-01

Thermal Protection Systems (TPS) of NASA's Space Shuttle External Tank include polyurethane and polyisocyanurate modified polyurethane foam insulations. These insulations, currently foamed with CFC 11 blowing agent, serve to maintain cryogenic propellant quality, maintain the external tank structural temperature limits, and minimize the formation of ice and frost that could potentially damage the ceramic insulation on the space shuttle orbiter. During flight the external tank insulations are exposed to mechanical, thermal and acoustical stresses. TPS must pass cryogenic flexure and substrate adhesion tests at -253 C, aerothermal and radiant heating tests at fluxes up to approximately 14 kilowatts per square meter, and thermal conductivity tests at cryogenic and elevated temperatures. Due to environmental concerns, the polyurethane insulation industry and the External Tank Project are tasked with replacing CFC 11. The flight qualification of foam insulations employing HCFC 141b as a foaming agent is currently in progress; HCFC 141b blown insulations are scheduled for production implementation in 1995. Realizing that the second generation HCFC blowing agents are an interim solution, the evaluation of third generation blowing agents with zero ozone depletion potential is underway. NASA's TPS Materials Research Laboratory is evaluating third generation blowing agents in cryogenic insulations for the External Tank; one option being investigated is the use of water as a foaming agent. A dimensionally stable insulation with low friability, good adhesion to cryogenic substrates, and acceptable thermal conductivity has been developed with low viscosity materials that are easily processed in molding applications. The development criteria, statistical experimental approach, and resulting foam properties will be presented.

Evolution, calibration, and operational characteristics of the two-dimensional test section of the Langley 0.3-meter transonic cryogenic tunnel

Science.gov (United States)

Ladson, Charles L.; Ray, Edward J.

1987-01-01

Presented is a review of the development of the world's first cryogenic pressure tunnel, the Langley 0.3-Meter Transonic Cryogenic Tunnel (0.3-m TCT). Descriptions of the instrumentation, data acquisition systems, and physical features of the two-dimensional 8- by 24-in, (20.32 by 60.96 cm) and advanced 13- by 13-in (33.02 by 33.02 cm) adaptive-wall test-section inserts of the 0.3-m TCT are included. Basic tunnel-empty Mach number distributions, stagnation temperature distributions, and power requirements are included. The Mach number capability of the facility is from about 0.20 to 0.90. Stagnation pressure can be varied from about 80 to 327 K.

One-loop masses of open-string scalar fields in string theory

International Nuclear Information System (INIS)

Kitazawa, Noriaki

2008-01-01

In phenomenological models with D-branes, there are in general open-string massless scalar fields, in addition to closed-string massless moduli fields corresponding to the compactification. It is interesting to focus on the fate of such scalar fields in models with broken supersymmetry, because no symmetry forbids their masses. The one-loop effect may give non-zero masses to them, and in some cases mass squared may become negative, which means the radiative gauge symmetry breaking. In this article we investigate and propose a simple method for calculating the one-loop corrections using the boundary state formalism. There are two categories of massless open-string scalar fields. One consists the gauge potential fields corresponding to compactified directions, which can be understood as scalar fields in uncompactified space-time (related with Wilson line degrees of freedom). The other consists 'gauge potential fields' corresponding to transverse directions of D-brane, which emerge as scalar fields in D-brane world-volume (related with brane moduli fields). The D-brane boundary states with constant backgrounds of these scalar fields are constructed, and one-loop scalar masses are calculated in the closed string picture. Explicit calculations are given in the following four concrete models: one D25-brane with a circle compactification in bosonic string theory, one D9-brane with a circle compactification in superstring theory, D3-branes at a supersymmetric C 3 /Z 3 orbifold singularity, and a model of brane supersymmetry breaking with D3-branes and anti-D7-branes at a supersymmetric C 3 /Z 3 orbifold singularity. We show that the sign of the mass squared has a strong correlation with the sign of the related open-string one-loop vacuum amplitude.

Interacting bosonic strings in subcritical dimensions

International Nuclear Information System (INIS)

Hwang, S.; Marnelius, R.

1988-01-01

Interaction theory for relativistic bosonic string in spacetime dimensions below the critical value 26 is formulated using BRST techniques with an extra scalar field. One-loop zero-point amplitudes for closed strings are modular invariant. For a free scalar field, vertex operators are constructed leading to, e.g., the old dual N-tachyon tree amplitudes in D < 26. The N-tachyon one-loop expressions contain closed string poles for open strings, and are modular invariant for closed strings. However, the threshold cuts are wrong in D < 25. Only for D=25 to the considered vertex operators lead to consistency. (orig.)

Micro string resonators as temperature sensors

DEFF Research Database (Denmark)

Larsen, T.; Schmid, S.; Boisen, A.

2013-01-01

The resonance frequency of strings is highly sensitive to temperature. In this work we have investigated the applicability of micro string resonators as temperature sensors. The resonance frequency of strings is a function of the tensile stress which is coupled to temperature by the thermal...... to the low thermal mass of the strings. A temperature resolution of 2.5×10-4 °C has been achieved with silicon nitride strings. The theoretical limit for the temperature resolution of 8×10-8 °C has not been reached yet and requires further improvement of the sensor....

A primer on string theory

CERN Document Server

Schomerus, Volker

2017-01-01

Since its conception in the 1960s, string theory has been hailed as one of the most promising routes we have to unify quantum mechanics and general relativity. This book provides a concise introduction to string theory explaining central concepts, mathematical tools and covering recent developments in physics including compactifications and gauge/string dualities. With string theory being a multidisciplinary field interfacing with high energy physics, mathematics and quantum field theory, this book is ideal for both students with no previous knowledge of the field and scholars from other disciplines who are looking for an introduction to basic concepts.

Splitting strings on integrable backgrounds

Energy Technology Data Exchange (ETDEWEB)

Vicedo, Benoit

2011-05-15

We use integrability to construct the general classical splitting string solution on R x S{sup 3}. Namely, given any incoming string solution satisfying a necessary self-intersection property at some given instant in time, we use the integrability of the worldsheet {sigma}-model to construct the pair of outgoing strings resulting from a split. The solution for each outgoing string is expressed recursively through a sequence of dressing transformations, the parameters of which are determined by the solutions to Birkhoff factorization problems in an appropriate real form of the loop group of SL{sub 2}(C). (orig.)

T-Duality Group for Open String Theory

OpenAIRE

Kajiura, Hiroshige

2001-01-01

We study T-duality for open strings on tori $\\T^d$. The general boundary conditions for the open strings are constructed, and it is shown that T-duality group, which preserves the mass spectrum of closed strings, preserves also the mass spectrum of the open strings. The open strings are transformed to those with different boundary conditions by T-duality. We also discuss the T-duality for D-brane mass spectrum, and show that the D-branes and the open strings with both ends on them are transfo...

POLOCAM: a millimeter wavelength cryogenic polarimeter prototype for MUSIC-POL

Science.gov (United States)

Laurent, Glenn T.; Vaillancourt, John E.; Savini, Giorgio; Ade, Peter A. R.; Beland, Stephane; Glenn, Jason; Hollister, Matthew I.; Maloney, Philip R.; Sayers, Jack

2012-09-01

As a proof-of-concept, we have constructed and tested a cryogenic polarimeter in the laboratory as a prototype for the MUSIC instrument (Multiwavelength Sub/millimeter Kinetic Inductance Camera). The POLOCAM instrument consists of a rotating cryogenic polarization modulator (sapphire half-waveplate) and polarization analyzer (lithographed copper polarizers deposited on a thin film) placed into the optical path at the Lyot stop (4K cold pupil stop) in a cryogenic dewar. We present an overview of the project, design and performance results of the POLOCAM instrument (including polarization efficiencies and instrumental polarization), as well as future application to the MUSIC-POL instrument.

Integrated hydraulic booster/tool string technology for unfreezing of stuck downhole strings in horizontal wells

Science.gov (United States)

Tian, Q. Z.

2017-12-01

It is common to use a jarring tool to unfreeze stuck downhole string. However, in a horizontal well, influenced by the friction caused by the deviated section, jarring effect is poor; on the other hand, the forcing point can be located in the horizontal section by a hydraulic booster and the friction can be reduced, but it is time-consuming and easy to break downhole string using a large-tonnage and constant pull force. A hydraulic booster - jar tool string has been developed for unfreezing operation in horizontal wells. The technical solution involves three elements: a two-stage parallel spring cylinder structure for increasing the energy storage capacity of spring accelerators; multiple groups of spring accelerators connected in series to increase the working stroke; a hydraulic booster intensifying jarring force. The integrated unfreezing tool string based on these three elements can effectively overcome the friction caused by a deviated borehole, and thus unfreeze a stuck string with the interaction of the hydraulic booster and the mechanical jar which form an alternatively dynamic load. Experimental results show that the jarring performance parameters of the hydraulic booster-jar unfreezing tool string for the horizontal wells are in accordance with original design requirements. Then field technical parameters were developed based on numerical simulation and experimental data. Field application shows that the hydraulic booster-jar unfreezing tool string is effective to free stuck downhole tools in a horizontal well, and it reduces hook load by 80% and lessens the requirement of workover equipment. This provides a new technology to unfreeze stuck downhole string in a horizontal well.

Integrated cryogenic sensors

International Nuclear Information System (INIS)

Juanarena, D.B.; Rao, M.G.

1991-01-01

Integrated cryogenic pressure-temperature, level-temperature, and flow-temperature sensors have several advantages over the conventional single parameter sensors. Such integrated sensors were not available until recently. Pressure Systems, Inc. (PSI) of Hampton, Virginia, has introduced precalibrated precision cryogenic pressure sensors at the Los Angeles Cryogenic Engineering Conference in 1989. Recently, PSI has successfully completed the development of integrated pressure-temperature and level-temperature sensors for use in the temperature range 1.5-375K. In this paper, performance characteristics of these integrated sensors are presented. Further, the effects of irradiation and magnetic fields on these integrated sensors are also reviewed

Introduction to field theory of strings

International Nuclear Information System (INIS)

Kikkawa, K.

1987-01-01

The field theory of bosonic string is reviewed. First, theory is treated in a light-cone gauge. After a brief survey of the first quantized theory of free string, the second quantization is discussed. All possible interactions of strings are introduced based on a smoothness condition of work sheets swept out by strings. Perturbation theory is developed. Finally a possible way to the manifest covariant formalism is discussed

Windings of twisted strings

Science.gov (United States)

Casali, Eduardo; Tourkine, Piotr

2018-03-01

Twistor string models have been known for more than a decade now but have come back under the spotlight recently with the advent of the scattering equation formalism which has greatly generalized the scope of these models. A striking ubiquitous feature of these models has always been that, contrary to usual string theory, they do not admit vibrational modes and thus describe only conventional field theory. In this paper we report on the surprising discovery of a whole new sector of one of these theories which we call "twisted strings," when spacetime has compact directions. We find that the spectrum is enhanced from a finite number of states to an infinite number of interacting higher spin massive states. We describe both bosonic and world sheet supersymmetric models, their spectra and scattering amplitudes. These models have distinctive features of both string and field theory, for example they are invariant under stringy T-duality but have the high energy behavior typical of field theory. Therefore they describe a new kind of field theories in target space, sitting on their own halfway between string and field theory.

Online helium inventory monitoring of JLab cryogenic systems

Science.gov (United States)

Hasan, N.; Knudsen, P.; Wright, M.

2017-12-01

There are five cryogenic plants at Jefferson Lab which support the LINAC, experiment hall end-stations and test facility. The majority of JLab’s helium inventory, which is around 15 tons, is allocated in the LINAC cryo-modules, with the majority of the balance of helium distributed at the cryogenic-plant level mainly as stored gas and liquid for stable operation. Due to the organic evolution of the five plants and independent actions within the experiment halls, the traditional inventory management strategy suffers from rapid identification of potential leaks. This can easily result in losses many times higher than the normally accepted (average) loss rate. A real-time program to quickly identify potential excessive leakage was developed and tested. This program was written in MATLAB© for portability, easy diagnostics and modification. It interfaces directly with EPICS to access the cryogenic system state, and with and NIST REFPROP© for real fluid properties. This program was validated against the actual helium offloaded into the system. The present paper outlines the details of the inventory monitoring program, its validation and a sample of the achieved results.

Modeling the Rapid Boil-Off of a Cryogenic Liquid When Injected into a Low Pressure Cavity

Science.gov (United States)

Lira, Eric

2016-01-01

Many launch vehicle cryogenic applications require the modeling of injecting a cryogenic liquid into a low pressure cavity. The difficulty of such analyses lies in accurately predicting the heat transfer coefficient between the cold liquid and a warm wall in a low pressure environment. The heat transfer coefficient and the behavior of the liquid is highly dependent on the mass flow rate into the cavity, the cavity wall temperature and the cavity volume. Testing was performed to correlate the modeling performed using Thermal Desktop and Sinda Fluint Thermal and Fluids Analysis Software. This presentation shall describe a methodology to model the cryogenic process using Sinda Fluint, a description of the cryogenic test set up, a description of the test procedure and how the model was correlated to match the test results.

Properties of strain gages at cryogenic temperature

International Nuclear Information System (INIS)

Shibata, Nobuo; Fujiyoshi, Toshimitsu.

1978-01-01

At the time of developing superconduction generators, the stress measurement for rotor parts is required to grasp the safety and performance of the rotor at cryogenic temperature, which is cooled with liquid helium. In case of carrying out the stress measurement with strain gages, the problems are as follows. The strain gages and lead wires are exposed to cryogenic temperature from 4 to 10 K and strong magnetic field of about 3T, and subjected to high centrifugal acceleration of about 500G. In order to establish the techniques of the stress measurement under such conditions, the adhesives and damp-proof coatings for strain gages and strain gages themselves in Japan and foreign countries were examined on the properties at cryogenic temperature. As for the properties of strain gages, mainly the apparent strain owing to temperature change was investigated, and the change of the gage factors was studies only at liquid nitrogen temperature. The stress measurement with strain gages at low temperature had been studied in detail down to liquid nitrogen temperature concerning LNG tanks. The experimental apparatus, the samples, the testing methods and the test results of cooling tests on adhesives and damp-proof coatings, and the temperature characteristics of strain gages are reported. The usable adhesives and coatings were found, and correction by accurate temperature measurement is required for apparent strain. (Kako, I.)

Covariant N-string amplitude

International Nuclear Information System (INIS)

Di Vecchia, P.; Sciuto, S.; Nakayama, R.; Petersen, J.L.; Sidenius, J.R.

1986-11-01

The BRST-invariant N-Reggeon vertex (for the bosonic string) previously given by us in the operator formulation is considered in more detail. In particular we present a direct derivation from the string path integral. Several crucial symmetry properties found a posteriori before, become a priori clearer in this formulation. A number of delicate points related to zero modes, cut off procedures and normal ordering prescriptions are treated in some detail. The old technique of letting the string field acquire a small dimension ε/2 → 0 + is found especially elegant. (orig.)

A disintegrating cosmic string

International Nuclear Information System (INIS)

Griffiths, J B; Docherty, P

2002-01-01

We present a simple sandwich gravitational wave of the Robinson-Trautman family. This is interpreted as representing a shock wave with a spherical wavefront which propagates into a Minkowski background minus a wedge (i.e. the background contains a cosmic string). The deficit angle (the tension) of the string decreases through the gravitational wave, which then ceases. This leaves an expanding spherical region of Minkowski space behind it. The decay of the cosmic string over a finite interval of retarded time may be considered to generate the gravitational wave. (letter to the editor)

Strings for quantumchromodynamics

International Nuclear Information System (INIS)

Schomerus, V.

2007-04-01

During the last decade, intriguing dualities between gauge and string theory have been found and explored. they provide a novel window on strongly couplde gauge physics, including QCD-like models. Based on a short historical review of modern string theory, we explain how so-called AdS/CFT dualities emerged at the end of the 1990s. Some of their concrete implications and remarkable recent progress are then illustrated for the simplest example, namely the multicolor limit of N=4 SYM theory in four dimensions. We end with a few comments on existing extensions to more realistic models and applications, in particular to the sQGP. This text is meant as a non-technical introduction to gauge/string dualities for (particle) physicists. (orig.)

Strings for quantumchromodynamics

Energy Technology Data Exchange (ETDEWEB)

Schomerus, V.

2007-04-15

During the last decade, intriguing dualities between gauge and string theory have been found and explored. they provide a novel window on strongly couplde gauge physics, including QCD-like models. Based on a short historical review of modern string theory, we explain how so-called AdS/CFT dualities emerged at the end of the 1990s. Some of their concrete implications and remarkable recent progress are then illustrated for the simplest example, namely the multicolor limit of N=4 SYM theory in four dimensions. We end with a few comments on existing extensions to more realistic models and applications, in particular to the sQGP. This text is meant as a non-technical introduction to gauge/string dualities for (particle) physicists. (orig.)

Cryogenic forced convection refrigerating system

International Nuclear Information System (INIS)

Klee, D.J.

1988-01-01

This patent describes the method of refrigerating products by contact with a refrigerating gas which comprises introducing product into a refrigeration zone, contacting the product with the refrigerating gas for a sufficient time to refrigerate it to the appropriate extent and removing the refrigerated product. The improvement for producing the refrigeration gas from a liquid cryogen such that essentially all of the liquid cryogen is fully vaporized before contacting the product comprises: (a) introducing the liquid cryogen, selected from the group consisting of liquid air and liquid nitrogen, at elevated pressure into an ejector as the motive fluid to accelerate a portion of a warm refrigerating gas through the ejector while mixing the cryogen and gas to effect complete vaporization of the liquid cryogen and substantial cooling of the portion of the refrigerating gas resulting in a cold discharge gas which is above the liquefaction temperature of the cryogen; (b) introducing the cold discharge gas into a forced circulation pathway of refrigerating gas and producing a cold refrigerating gas which contacts and refrigerates product and is then at least partially recirculated; (c) sensing the temperature of the refrigerating gas in the forced circulation pathway and controlling the introduction of liquid cryogen with regard to the sensed temperature to maintain the temperature of the discharge gas above the liquefacton temperature of the cryogen utilized

The cryogenic cooling program at the Advanced Photon Source

International Nuclear Information System (INIS)

Rogers, C.S.; Mills, D.M.; Assoufid, L.

1994-06-01

This paper describes the experimental and analytical program in cryogenic cooling of high-heat-load optics at the Advanced-Photon Source. A prototype liquid nitrogen pumping system has been procured. This pump provides a variable flow rate of 1 to 10 gpm of pressurized liquid nitrogen and is sized to handle up to 5 kW of optic heat load. Also, a high-vacuum, double-crystal monochromator testing tank has been fabricated. This system will be used to test cryogenic crystals at existing synchrotron sources. A finite element analysis has been performed for a cryogenically cooled Si crystal in the inclined geometry for Undulator A at 100 mA. The inclination angle was 80 degrees. It was set to diffract from the (111) planes at the first harmonic energy of 4.2 keV. The maximum slope error in the diffraction plane was calculated to be about 1 μrad with a peak temperature of 94 K. An analysis has also been performed for a cryogenically-cooled ''thin'' crystal oriented in the Bragg geometry which accepts 87% of the lst harmonic photons at 3.866 keV. The total absorbed power was 131 W at 100 mA current and the peak temperature was 124 K

Remarks on entanglement entropy in string theory

Science.gov (United States)

Balasubramanian, Vijay; Parrikar, Onkar

2018-03-01

Entanglement entropy for spatial subregions is difficult to define in string theory because of the extended nature of strings. Here we propose a definition for bosonic open strings using the framework of string field theory. The key difference (compared to ordinary quantum field theory) is that the subregion is chosen inside a Cauchy surface in the "space of open string configurations." We first present a simple calculation of this entanglement entropy in free light-cone string field theory, ignoring subtleties related to the factorization of the Hilbert space. We reproduce the answer expected from an effective field theory point of view, namely a sum over the one-loop entanglement entropies corresponding to all the particle-excitations of the string, and further show that the full string theory regulates ultraviolet divergences in the entanglement entropy. We then revisit the question of factorization of the Hilbert space by analyzing the covariant phase-space associated with a subregion in Witten's covariant string field theory. We show that the pure gauge (i.e., BRST exact) modes in the string field become dynamical at the entanglement cut. Thus, a proper definition of the entropy must involve an extended Hilbert space, with new stringy edge modes localized at the entanglement cut.

Is the string theory doomed?

International Nuclear Information System (INIS)

Le Meur, H.; Daninos, F.; Bachas, C.

2007-01-01

Since its beginning, in the sixties, the string theory has succeeded in overcoming a lot of theoretical difficulties but now the complete absence of experimental validation entertains doubts about its ability to represent the real world and questions its hegemony in today's theoretical physics. Other space-time theories like the twistors, or the non-commutative geometry, or the loop quantum gravity, or the causal dynamics triangulation might begin receiving more attention. Despite all that, the string theory can be given credit for 4 achievements. First, the string theory has provided a consistent quantum description of gravity. Secondly, the string theory has built a theoretical frame that has allowed the unification of the 4 basic interactions. Thirdly, the string theory applied to astrophysics issues has demonstrated that the evaporation of a black hole does not necessarily lead to a loss of information which comforts the universality of the conservation of the quantity of information in any system and as a consequence put a fatal blow to the so-called paradox observed in black holes. Fourthly, the string theory has given a new and original meaning on the true nature of space-time. (A.C.)

Introduction to string theory

CERN Multimedia

CERN. Geneva. Audiovisual Unit

2002-01-01

I will present a simple and non-technical overview of string theory, aimed for non-experts who like to get some idea what string theory is about. Besides introductory material, I intend to cover also some of the more recent developments.

Unification of string dualities

International Nuclear Information System (INIS)

Sen, A.

1997-01-01

We argue that all conjectured dualities involving various string, M- and F-theory compactifications can be 'derived' from the conjectured duality between type I and SO(32) heterotic string theory, T-dualities and the definition of M-and F-theories. (orig.)

Hosotani model in closed string theory

International Nuclear Information System (INIS)

Shiraishi, Kiyoshi.

1988-11-01

Hosotani mechanism in the closed string theory with current algebra symmetry is described by the (old covariant) operator method. We compare the gauge symmetry breaking mechanism in a string theory which has SU(2) symmetry with the one in an equivalent compactified closed string theory. We also investigate the difference between Hosotani mechanism and Higgs mechanism in closed string theories by calculation of a fourpoint amplitude of 'Higgs' bosons at tree level. (author)

String breaking with Wilson loops?

CERN Document Server

Kratochvila, S; Kratochvila, Slavo; Forcrand, Philippe de

2003-01-01

A convincing, uncontroversial observation of string breaking, when the static potential is extracted from Wilson loops only, is still missing. This failure can be understood if the overlap of the Wilson loop with the broken string is exponentially small. In that case, the broken string ground state will only be seen if the Wilson loop is long enough. Our preliminary results show string breaking in the context of the 3d SU(2) adjoint static potential, using the L\\"uscher-Weisz exponential variance reduction approach. As a by-product, we measure the fundamental SU(2) static potential with improved accuracy and see clear deviations from Casimir scaling.

Architectures and representations for string transduction

NARCIS (Netherlands)

Chrupala, Grzegorz

2015-01-01

String transduction problems are ubiquitous in natural language processing: they include transliteration, grapheme-to-phoneme conversion, text normalization and translation. String transduction can be reduced to the simpler problems of sequence labeling by expressing the target string as a sequence

Introduction to strings and superstrings

International Nuclear Information System (INIS)

Traubenberg, M.R. de.

1988-01-01

We discuss the main features on the formulation of string theory that, in a primitive level, describe the hadronic phenomenon of duality. We also study an extension of the models of closed and strings with spin. Then, by using supersymmetry, it is formulated the theory of superstrings and heterotic strings with the aim of unify the fundamental interactions and matter. (M.W.O.) [pt

Singleton strings

International Nuclear Information System (INIS)

Engquist, J.; Sundell, P.; Tamassia, L.

2007-01-01

The group theoretical structure underlying physics in anti de Sitter (AdS) spacetime is intrinsically different with respect to the flat case, due to the presence of special ultra-short representations, named singletons, that do not admit a flat space limit. The purpose of this collaboration is to exploit this feature in the study of string and brane dynamics in AdS spacetime, in particular while trying to establish a connection between String Theory in AdS backgrounds (in the tensionless limit) and Higher-Spin Gauge Theory. (orig.)

Aspects of some dualities in string theory

Science.gov (United States)

Kim, Bom Soo

AdS/CFT correspondence in string theory has changed landscape of the theoretical physics. Through this celebrated duality between gravity theory and field theory, one can investigate analytically strongly coupled gauge theories such as Quantum Chromodynamics (QCD) in terms of weakly coupled string theory such as supergravity theory and vice versa. In the first part of this thesis we used this duality to construct a new type of nonlocal field theory, called Puff Field Theory, in terms of D3 branes in type IIB string theory with a geometric twist. In addition to the strong-weak duality of AdS/CFT, there also exists a weak-weak duality, called Twistor String Theory. Twistor technique is successfully used to calculate the SYM scattering amplitude in an elegant fashion. Yet, the progress in the string theory side was hindered by a non-unitary conformal gravity. We extend the Twistor string theory by introducing mass terms, in the second part of the thesis. A chiral mass term is identified as a vacuum expectation value of a conformal supergravity field and is tied with the breaking of the conformal symmetry of gravity. As a prime candidate for a quantum theory of gravity, string theory revealed many promising successes such as counting the number of microstates in supersymmetric Black Holes thermodynamics and resolution of timelike and null singularities, to name a few. Yet, the fundamental string and M-theroy formulations are not yet available. Various string theories without gravity, such as Non-Commutative Open String (NCOS) and Open Membrane (OM) theories, are very nice playground to investigate the fundamental structure of string and M-theory without the complication of gravity. In the last part of the thesis, simpler Non-Relativistic String Theories are constructed and investigated. One important motivation for those theories is related to the connection between Non-Relativistic String Theories and Non-critical String Theories through the bosonization of betagamma

Cryogenic system for VECC K500 superconducting cyclotron

CERN Document Server

Pal, G; Bhattacharyya, T K; Bhandari, R K

2009-01-01

VEC Centre, Kolkata in India is at an advanced stage of commissioning a K500 superconducting cyclotron. The superconducting coil of the magnet for cyclotron is cooled by liquid helium. Three liquid helium cooled cryopanels, placed inside the Dees of the radiofrequency system, maintain the vacuum in the acceleration region of the superconducting cyclotron. The cryogenic system for magnet for cyclotron has been tested by cooling the coil and energizing the magnet. The cryogenic system for cryopanels has also been tested. Heater and temperature sensor were placed on the liquid helium cold head for cryopanel. The temperature of the cold head was observed to be below 20 K upto a heat load of 11.7 watt.

String cosmology modern string theory concepts from the cosmic structure

CERN Document Server

2009-01-01

The field of string cosmology has matured considerably over the past few years, attracting many new adherents to this multidisciplinary Field. This book fills a critical gap by bringing together strains of current research into one single volume. The resulting collection of selected articles presents the latest, ongoing results from renowned experts currently working in the field. This offers the possibility for practitioners to become conversant with many different aspects of string cosmology

Semilocal and electroweak strings

NARCIS (Netherlands)

Achucarro, A; Vachaspati, T

We review a class of non-topological defects in the standard electroweak model, and their implications. Starting with the semilocal string, which provides a counterexample to many well-known properties of topological vortices, we discuss electroweak strings and their stability with and without

Twenty-five questions for string theorists

Energy Technology Data Exchange (ETDEWEB)

Binetruy, Pierre; /Orsay, LPT; Kane, G.L.; /Michigan U., MCTP; Lykken, Joseph D.; /Fermilab; Nelson, Brent D.; /Pennsylvania U.

2005-09-01

In an effort to promote communication between the formal and phenomenological branches of the high-energy theory community, we provide a description of some important issues in supersymmetric and string phenomenology. We describe each within the context of string constructions, illustrating them with specific examples where applicable. Each topic culminates in a set of questions that we believe are amenable to direct consideration by string theorists, and whose answers we think could help connect string theory and phenomenology.

Nonrelativistic closed string theory

International Nuclear Information System (INIS)

Gomis, Jaume; Ooguri, Hirosi

2001-01-01

We construct a Galilean invariant nongravitational closed string theory whose excitations satisfy a nonrelativistic dispersion relation. This theory can be obtained by taking a consistent low energy limit of any of the conventional string theories, including the heterotic string. We give a finite first order worldsheet Hamiltonian for this theory and show that this string theory has a sensible perturbative expansion, interesting high energy behavior of scattering amplitudes and a Hagedorn transition of the thermal ensemble. The strong coupling duals of the Galilean superstring theories are considered and are shown to be described by an eleven-dimensional Galilean invariant theory of light membrane fluctuations. A new class of Galilean invariant nongravitational theories of light-brane excitations are obtained. We exhibit dual formulations of the strong coupling limits of these Galilean invariant theories and show that they exhibit many of the conventional dualities of M theory in a nonrelativistic setting

Strings draw theorists together

International Nuclear Information System (INIS)

Green, Michael

2000-01-01

Theorists are confident that they are closer than ever to finding a quantum theory that unites gravity with the three other fundamental forces in nature. Many of the leading figures in the world of string theory met at the California Institute of Technology in January to discuss recent progress in the field and to reflect on the state of the theory. The enthusiastic mood of the gathering was based on the fact that string theory provides an elegant framework for a unified theory of all the forces and particles in nature, and also gives a consistent quantum-mechanical description of general relativity. String theory, and more precisely superstring theory, describes the assortment of elementary particles such as quarks and leptons, and the gauge bosons responsible for mediating forces in a unified manner as different modes of vibration of a single extended string. This version of the theory also embodies supersymmetry a conjectured symmetry that unifies fermions and bosons. Furthermore, the fact that the string has a fundamental length scale - the ''string length'' - apparently cures the short-distance problems of uniting general relativity with quantum theory. The main problem with the early formulations of superstring theory was that they emphasized the ''perturbative'' point of view, an approximation that describes string-like quantum-mechanical particles moving through classical (that is non quantum-mechanical) space-time. However, very general arguments require that any quantum theory of gravity should also describe space-time geometry in a quantum-mechanical manner. The classical geometry of space-time should then emerge as an approximate description at distance scales much larger than the so-called Planck scale of 10 -33 m. This requires an understanding of the theory beyond the perturbative approximation. It is the quest for this more fundamental description of string theory that has provided the main challenge for string theorists over the past decade. Much

Non-linear σ-models and string theories

International Nuclear Information System (INIS)

Sen, A.

1986-10-01

The connection between σ-models and string theories is discussed, as well as how the σ-models can be used as tools to prove various results in string theories. Closed bosonic string theory in the light cone gauge is very briefly introduced. Then, closed bosonic string theory in the presence of massless background fields is discussed. The light cone gauge is used, and it is shown that in order to obtain a Lorentz invariant theory, the string theory in the presence of background fields must be described by a two-dimensional conformally invariant theory. The resulting constraints on the background fields are found to be the equations of motion of the string theory. The analysis is extended to the case of the heterotic string theory and the superstring theory in the presence of the massless background fields. It is then shown how to use these results to obtain nontrivial solutions to the string field equations. Another application of these results is shown, namely to prove that the effective cosmological constant after compactification vanishes as a consequence of the classical equations of motion of the string theory. 34 refs