High-energy Facilities Research Articles

Soft x-ray photoelectron spectroscopy study of type-I clathrates

Extensive soft x-ray photoelectron spectroscopy studies are performed on Ba8Ga16Ge30 (BGG) and Sr8Ga16Ge30 (SGG) single crystals ranging from Fermi to core levels, at a high-energy facility. Valence band x-ray photoelectron spectroscopy (XPS) experiments with theoretical calculations revealed that the valence band is mainly constructed by the Ge/Ga 4s and 4p wave functions with little contribution of the Ba/Sr atomic orbitals. Surprisingly, unexpected features evidencing the different shift for the 2a- and 6d- sites between Ba 4d and Sr 3d are observed. The detailed analyses including theoretical support by first-principles band-structure calculations lead to the conclusion that the component distributions of the larger tetrakaidecahedral cage are different depending on the endohedral atoms, which contrasts with the past consensus that BGG and SGG have the same framework structure. This may give thorough reconsiderations on earlier interpretations of experimental data.

Complementarity of the CERN Large Hadron Collider and the e + e − International Linear Collider

The next-generation high-energy facilities, the CERN Large Hadron Collider (LHC) and the prospective e + e − International Linear Collider (ILC), are expected to unravel new structures of matter and forces from the electroweak scale to the TeV scale. In this report we review the complementary role of LHC and ILC in drawing a comprehensive and high-precision picture of the mechanism breaking the electroweak symmetries and generating mass, and the unification of forces in the frame of supersymmetry.

Effect of Ion Energy on Charge Loss From Floating Gate Memories

Heavy ions typical of the space environment have energies which exceed by orders of magnitude those available at particle accelerators. In this paper we are irradiating state of the art floating gate memories by using both a medium energy (SIRAD) and a high energy (RADEF) facilities. The corruption of stored information decreases when increasing ion energy. The proposed model deals with the broader track found for higher energy ions. Implications for testing procedures and for reliability considerations are discussed.

NOVEL ACCELERATION TECHNIQUES FOR THE PHYSICS OF MASSIVE NEUTRINOS

In the forthcoming decades, the physics of massive neutrinos will pose unprecedented challenges to traditional acceleration techniques. In this talk we revise the main motivations for pursuing neutrino oscillation studies with novel ν sources and, particularly, we consider the opportunities offered by laser-plasma accelerators. The existence of efficient ion acceleration regimes in collective laser-plasma interactions opens up the possibility to develop neutrino and, more generally, high-energy physics facilities in conjunction with projects for inertial confinement nuclear fusion (ICF) and neutron spallation sources. Moreover, parametric amplification techniques allow pulse compression implementations that do not fall in contradiction with current designs for ICF drivers. We discuss the conditions under which these efficient regimes can be put into operation and the perspectives for their empirical verification.

Silicon and Germanium Network Polyhedra viewed from Soft X-ray Spectroscopy

AbstractThe electronic states of Ba8Ga16Ge30 and Sr8Ga16Ge30 are studied by soft x-ray photoelectron spectroscopy (XPS) at a high-energy facility. In Ba8Ga16Ge30, three bands are resolved in the valence band region. Resonance experiments together with theoretical calculations show that the three band structures in the valence band are mainly constructed by the Ge/Ga 4s and 4p wave functions with little contributions of Ba 5s, 5p and 5d. The valence band of Sr8Ga16Ge30 shows a similar feature to that of Ba8Ga16Ge30. It is clearly shown that the atomic orbitals of Ba and Sr make little hybridization with the orbitals made by the framework polyhedra. This provides the understanding of the thermoelectricity in clathrates, and assists the design in high performance thermoelectric materials in this family.

Measurement and simulation of lineal energy distribution at the CERN high energy facility with a tissue equivalent proportional counter

The response of a tissue equivalent proportional counter (TEPC) in a mixed radiation field with a neutron energy distribution similar to the radiation field at commercial flight altitudes has been studied. The measurements have been done at the CERN-EU High-Energy Reference Field (CERF) facility where a well-characterised radiation field is available for intercomparison. The TEPC instrument used by the ARC Seibersdorf Research is filled with pure propane gas at low pressure and can be used to determine the lineal energy distribution of the energy deposition in a mass of gas equivalent to a 2 microm diameter volume of unit density tissue, of similar size to the nuclei of biological cells. The linearity of the detector response was checked both in term of dose and dose rate. The effect of dead-time has been corrected. The influence of the detector exposure location and orientation in the radiation field on the dose distribution was also studied as a function of the total dose. The microdosimetric distribution of the absorbed dose as a function of the lineal energy has been obtained and compared with the same distribution simulated with the FLUKA Monte Carlo transport code. The dose equivalent was calculated by folding this distribution with the quality factor as a function of linear energy transfer. The comparison between the measured and simulated distributions show that they are in good agreement. As a result of this study the detector is well characterised, thanks also to the numerical simulations the instrument response is well understood, and it's currently being used onboard the aircrafts to evaluate the dose to aircraft crew caused by cosmic radiation.

The application of a SRAM chip as a novel neutron detector

High-density, fast digital devices, like field programmable gate arrays (FPGAs), microcontrollers, and static random access memories (SRAMs), can be produced by nanotechnology. New technologies allow the design of fast and powerful devices; however, the decreasing dimensions create new problems. Even at ground level, cosmic ray particles arriving from outer space can affect digital devices and provoke single-event effects (SEEs) due to the smaller sensitive volume (SV). In general, for decreasing feature size of memory cells the expected critical charge decreases and the expected sensitivity to radiation increases. High-density SRAM chips were used to design a fast response, highly sensitive neutron detector. We have conducted experiments with SRAMs at the DESY Research Centre in Hamburg, Germany. Memory contents (number of SEU) were recorded as a function of neutron expose time. The chips were exposed to a neutron field from an americium-beryllium neutron source (241AmBe). The second experiment was accomplished in the 450 MeV electron Linac (Linac II) tunnel. Another batch of SRAMs was irradiated with 60Co gamma rays to a dose of about 60 Gy, and no SEU was registered. This shows that gamma radiation has no substantial effect on the production of SEU in the SRAM. The proposed detector could be ideal for the detection of pulsed neutron radiation produced by high-energy electron linear accelerators and synchrotron facilities, which are currently in operation and planned for the near future.

Benchmark studies of induced radioactivity produced in LHC materials, part II: remanent dose rates

A new method to estimate remanent dose rates, to be used with the Monte Carlo code FLUKA, was benchmarked against measurements from an experiment that was performed at the CERN-EU high-energy reference field facility. An extensive collection of samples of different materials were placed downstream of, and laterally to, a copper target, intercepting a positively charged mixed hadron beam with a momentum of 120 GeV c(-1). Emphasis was put on the reduction of uncertainties by taking measures such as careful monitoring of the irradiation parameters, using different instruments to measure dose rates, adopting detailed elemental analyses of the irradiated materials and making detailed simulations of the irradiation experiment. The measured and calculated dose rates are in good agreement.

Characterisation of radionuclides formed by high-energy neutron irradiation

The physicochemical properties of radionuclides suspended in the air are important parameters in order to evaluate internal doses due to the inhalation of the airborne radionuclides and to develop the air-monitoring system in high-energy proton accelerator facilities. This study focuses on the property of radioactive airborne chlorine (38Cl and 39Cl) and sulphur (38S) produced in Ar gas by irradiation with high-energy neutrons. As a result of the irradiation of a mixture of Ar gas and dry air, 38Cl and 39Cl existed as non-acidic gas and 38S was present as acidic gas. Furthermore, it has been found that in the high-energy neutron irradiation of aerosol containing Ar gas, the higher the amount of radioactive aerosols, the lower will be the amount of radioactive acidic gas.

Benchmark studies of induced radioactivity produced in LHC materials, part I: specific activities

Samples of materials which will be used in the LHC machine for shielding and construction components were irradiated in the stray radiation field of the CERN-EU high-energy reference field facility. After irradiation, the specific activities induced in the various samples were analysed with a high-precision gamma spectrometer at various cooling times, allowing identification of isotopes with a wide range of half-lives. Furthermore, the irradiation experiment was simulated in detail with the FLUKA Monte Carlo code. A comparison of measured and calculated specific activities shows good agreement, supporting the use of FLUKA for estimating the level of induced activity in the LHC.

Vision to Reality: From Robert R. Wilson's Frontier to Leon M. Lederman's Fermilab

This paper examines the roles of vision and leadership in creating and directing Fermi National Accelerator Laboratory from the late 1960s through the 1980s. The story divides into two administrations having different problems and accomplishments, that of Robert R. Wilson (1967-1978), which saw the transformation from cornfield to frontier physics facility, and that of Leon Max Lederman (1979-1989), in which the laboratory evolved into one of the world's major high-energy facilities. Lederman's pragmatic vision of a user-based experimental community helped him to convert the pioneering facility that Wilson had built frugally into a laboratory with a stable scientific, cultural, and funding environment.

Summary of ND2001 Papers (1): Experiments

A summary is given for the papers on experimental area in ND2001. Shifts to intermediate and high-energy regions and various new facilities and experimental methods were impressive. New experiments in intermediate and high-energy region were reported as well as those in low energy region relevant to fission and fusion reactors, although the papers of the latter category decreased markedly.

Ultrasonic monitoring of laser damage in fused silica

The growth of a laser induced, surface damage site in a fused silica window was monitored by the ultrasonic pulse-echo technique. The laser damage was grown using 15 ns pulses of 1.053 μm wavelength light at a fluence of ∼25 J/cm2. The ultrasonic signal amplitude exhibited variations with the damage size which are attributable to the changing subsurface morphology of the damage site. The sensitivity to subsurface morphology makes the ultrasonic methodology a promising tool for monitoring laser damage in fused silica optics. This type of diagnostic capability may facilitate the safe deployment of large, high powered laser systems used in high energy and fusion research facilities.

Charmonium production at neutrino factories

At existing and planned neutrino factories (high energy and high intensity neutrino beam facilities) precision studies of QCD in neutrino-nucleon interactions are a realistic opportunity. We investigate charmonium production in fixed target neutrino experiments. We find that $J/\psi$ production in neutrino-nucleon collision is dominated by the color octet $^3S_1$ NRQCD matrix element in a neutral current process, which is not accessible in photo or leptoproduction. Neutrino experiments at a future Muon Collider will acquire sufficient event rate to accurately measure color octet matrix element contributions. The currently running high energy neutrino experiments, NOMAD and NuTeV could also observe several such events.

Monte Carlo calculations to characterize the source for neutron therapy facilities.

Modern radiation treatment planning for photons includes full 3D modeling of the adsorbed dose distribution, accurate inclusion of the patient anatomy, and consideration of significant changes in material density and composition. Such efforts are founded in an accurate description of the radiation source and the beam delivery system. Modern fast neutron therapy facilities employ highly penetrating beams and isocentric beam delivery. Treatment planning is largely based on analytic models adapted from photon codes and interaction cross sections normalized to macroscopic attenuation. However, the recent PEREGRINE initiative at Lawrence Livermore Laboratory offers the possibility of fully stochastic modeling if the neutron source can be adequately described. In this article we report neutron source modeling of three high energy facilities. Neutron production is based on the intra-nuclear cascade model of the LAHET code while neutron transport through the beam delivery system is managed by MCNP using cross section libraries extended to 100 MeV neutron energy. PEREGRINE is then used to transport the neutron beam through typical phantoms. The resulting neutron sources are in excellent agreement with the limited experimental information and the measured phantom data are well described by the PEREGRINE transport using the LAHET/MCNP determined neutron sources.

An Early Warning System for Bucharest

The discussion of early warning systems (EWS) for natural disasters has intensified toward the end of the IDNDR. The value of EWS for hazards with long warning times such as tsunamis, volcanic activities, and tornadoes is undisputed. There is an obvious lack of regional warning capacity for tsunamis, and by far not all volcanoes threatening urban centers are properly monitored. In the case of earthquakes, warning times are fairly small, ranging from seconds to a maximum of about one minute for Mexico City. However, even this small time window can provide opportunities to trigger measures automatically, such as the shutdown of computers, the rerouting of electrical power, the shutdown of disk drives, the shutdown of high-precision facilities, the shutdown of airport operations, the shutdown of manufacturing facilities, the stoppage of trains, the shutdown of high-energy facilities, the shutdown of gas distribution, the alerting of hospital operating rooms, the opening of...

Control of the Radiation Environment and the Worker in High-Energy Facilities

Control of the Radiation Environment and the Worker in High-Energy Facilities

Geometric Arrangement of Beamlets in Large Laser Fusion Facilities

Geometrical arrangements for locating the large number of beamlets used in high-energy laser fusion facilities around a target chamber, suitable for the 1- to 2-MJ Phebus upgrade facility, are compared. The beamlets are clustered together and enter the target chamber area from two opposite poles. Beamlets from two different amplifier regions are interlaced around four pairs of conical surfaces, so that more symmetrical illumination of indirect drive targets is possible even when only some of the amplifiers are operational. A passive system is proposed to protect the focus lenses from X rays, ion debris, and internal target chamber pollutants. The system includes sacrificial debris shields and a static, [approximately] 2-m length of incondensable gas. A crosswise orientation allows for maximum operational flexibility; an in-line orientation uses three fewer mirrors per beamlet but requires a larger target chamber room and longer laser bays. Neutron protection includes concrete shielding and also an [approximately] 1- to 2-m-thick water shield positioned just inside the periphery of the target chamber room. Selected low-activation materials are used as much as possible inside the water shield to minimize the recovery time after a shot. 7 refs., 2 figs.

The status and prospects of high-energy neutron test facilities for fusion materials development

The status and prospects of high-energy neutron test facilities for fusion materials development

The status and prospects of high-energy neutron test facilities for fusion materials development

The status of progress in the development of facility concepts and the relevant technology is summarized, referring to the recent outcomes from the international collaborative activities on reviewing the technical feasibility and the suitability of candidate facilities for testing fusion reactor materials. The discussion is focussed on the way to reach the goal of an international fusion materials irradiation facility (IFMIF), which is capable of testing materials for DEMO reactors and beyond. Based on the state of knowledge reviewed, a staged approach is suggested in phase with the current world strategy for fusion power development.