Overview of Solid Target Studies for a Neutrino Factory

The UK pro­gramme of high power tar­get de­vel­op­ments for a Neu­tri­no Fac­to­ry is cen­tred on the study of high-Z ma­te­ri­als (tung­sten, tan­ta­lum). A de­scrip­tion of life­time shock tests on can­di­date ma­te­ri­als is given as part of the re­search into a solid tar­get so­lu­tion. A fast high cur­rent pulse is ap­plied to a thin wire of the sam­ple ma­te­ri­al and the life­time mea­sured from the num­ber of puls­es be­fore fail­ure. These mea­sure­ments are made at tem­per­a­tures up to ~2000 K. The stress on the wire is cal­cu­lat­ed using the LS-DY­NA code and com­pared to the stress ex­pect­ed in the real Neu­tri­no Fac­to­ry tar­get. It has been found that tan­ta­lum is too weak to sus­tain pro­longed stress at these tem­per­a­tures but a tung­sten wire has reached over 26 mil­lion puls­es (equiv­a­lent to more than ten years of op­er­a­tion at the Neu­tri­no Fac­to­ry). An ac­count is given of the op­ti­mi­sa­tion of sec­ondary pion pro­duc­tion from the tar­get and the is­sues re­lat­ed to mount­ing the tar­get in the muon cap­ture solenoid and tar­get sta­tion are dis­cussed

Tungsten Behavior at High Temperature and High Stress

Re­cent­ly re­port­ed re­sults on the tung­sten life­time/fa­tigue tests under con­di­tions ex­pect­ed in the Neu­tri­no Fac­to­ry tar­get have strength­ened the case of solid tar­get op­tion for a Neu­tri­no Fac­to­ry. This paper gives de­scrip­tion of the de­tailed mea­sure­ments of the tung­sten prop­er­ties at high tem­per­a­ture and high stress. We have per­formed ex­ten­sive set of mea­sure­ments of the sur­face dis­place­ment and ve­loc­i­ty of the tung­sten wires that were stressed by pass­ing a fast, high cur­rent pulse through a thin sam­ple. Ra­di­al and lon­gi­tu­di­nal os­cil­la­tions of the wire were mea­sured by a Laser Doppler Vi­brom­e­ter. The wire was op­er­at­ed at tem­per­a­tures of 300-2500 K by ad­just­ing the pulse rep­e­ti­tion rate. In doing so we have tried to sim­u­late the con­di­tions (high stress and tem­per­a­ture) ex­pect­ed at the Neu­tri­no Fac­to­ry. Most im­por­tant re­sult of this study is an ex­per­i­men­tal con­fir­ma­tion that strength of tung­sten re­mains high at high tem­per­a­ture and high stress. The ex­per­i­men­tal re­sults have been found to agree very well with LS-DY­NA mod­elling re­sults

The design and performance of an improved target for MICE

The linear motor driving the target for the Muon Ionisation Cooling Experiment has been redesigned to improve its reliability and performance. A new coil-winding technique is described which produces better magnetic alignment and improves heat transport out of the windings. Improved field-mapping has allowed the more precise construction to be demonstrated, and an enhanced controller exploits the full features of the hardware, enabling increased acceleration and precision. The new user interface is described and analysis of performance data to monitor friction is shown to allow quality control of bearings and a measure of the ageing of targets during use

Spin-polaron model: transport properties of EuB6_6

To understand anomalous transport properties of EuB$_6$, we have studied the spin-polaron Hamiltonian incorporating the electron-phonon interaction. Assuming a strong exchange interaction between the carriers and the localized spins, the electrical conductivity is calculated. The temperature and magnetic field dependence of the resistivity of EuB$_6$ are well explained. At low temperature, magnons dominate the conduction process, whereas the lattice contribution becomes significant at very high temperature due to the scattering with the phonons. Large negative magnetoresistance near the ferromagnetic transition is also reproduced as observed in EuB$_6$.Comment: 4 pages, 3 figures, accepted in Phys. Rev.

The design, construction and performance of the MICE target

The pion-production target that serves the MICE Muon Beam consists of a titanium cylinder that is dipped into the halo of the ISIS proton beam. The design and construction of the MICE target system are described along with the quality-assurance procedures, electromagnetic drive and control systems, the readout electronics, and the data-acquisition system. The performance of the target is presented together with the particle rates delivered to the MICE Muon Beam. Finally, the beam loss in ISIS generated by the operation of the target is evaluated as a function of the particle rate, and the operating parameters of the target are derived

Simulating (electro)hydrodynamic effects in colloidal dispersions: smoothed profile method

Previously, we have proposed a direct simulation scheme for colloidal dispersions in a Newtonian solvent [Phys.Rev.E 71,036707 (2005)]. An improved formulation called the ``Smoothed Profile (SP) method'' is presented here in which simultaneous time-marching is used for the host fluid and colloids. The SP method is a direct numerical simulation of particulate flows and provides a coupling scheme between the continuum fluid dynamics and rigid-body dynamics through utilization of a smoothed profile for the colloidal particles. Moreover, the improved formulation includes an extension to incorporate multi-component fluids, allowing systems such as charged colloids in electrolyte solutions to be studied. The dynamics of the colloidal dispersions are solved with the same computational cost as required for solving non-particulate flows. Numerical results which assess the hydrodynamic interactions of colloidal dispersions are presented to validate the SP method. The SP method is not restricted to particular constitutive models of the host fluids and can hence be applied to colloidal dispersions in complex fluids

Key questions in marine mammal bioenergetics

Bioenergetic approaches are increasingly used to understand how marine mammal populations could be affected by a changing and disturbed aquatic environment. There remain considerable gaps in our knowledge of marine mammal bioenergetics, which hinder the application of bioenergetic studies to inform policy decisions. We conducted a priority-setting exercise to identify high-priority unanswered questions in marine mammal bioenergetics, with an emphasis on questions relevant to conservation and management. Electronic communication and a virtual workshop were used to solicit and collate potential research questions from the marine mammal bioenergetic community. From a final list of 39 questions, 11 were identified as ‘key’ questions because they received votes from at least 50% of survey participants. Key questions included those related to energy intake (prey landscapes, exposure to human activities) and expenditure (field metabolic rate, exposure to human activities, lactation, time-activity budgets), energy allocation priorities, metrics of body condition and relationships with survival and reproductive success and extrapolation of data from one species to another. Existing tools to address key questions include labelled water, animal-borne sensors, mark-resight data from long-term research programs, environmental DNA and unmanned vehicles. Further validation of existing approaches and development of new methodologies are needed to comprehensively address some key questions, particularly for cetaceans. The identification of these key questions can provide a guiding framework to set research priorities, which ultimately may yield more accurate information to inform policies and better conserve marine mammal populations

Characterisation of the muon beams for the Muon Ionisation Cooling Experiment

A novel single-particle technique to measure emittance has been developed and used to characterise seventeen different muon beams for the Muon Ionisation Cooling Experiment (MICE). The muon beams, whose mean momenta vary from 171 to 281 MeV/c, have emittances of approximately 1.2–2.3 π mm-rad horizontally and 0.6–1.0 π mm-rad vertically, a horizontal dispersion of 90–190 mm and momentum spreads of about 25 MeV/c. There is reasonable agreement between the measured parameters of the beams and the results of simulations. The beams are found to meet the requirements of MICE

Search for the glueball candidates f0(1500) and fJ(1710) in gamma gamma collisions

Data taken with the ALEPH detector at LEP1 have been used to search for gamma gamma production of the glueball candidates f0(1500) and fJ(1710) via their decay to pi+pi-. No signal is observed and upper limits to the product of gamma gamma width and pi+pi- branching ratio of the f0(1500) and the fJ(1710) have been measured to be Gamma_(gamma gamma -> f0(1500)). BR(f0(1500)->pi+pi-) < 0.31 keV and Gamma_(gamma gamma -> fJ(1710)). BR(fJ(1710)->pi+pi-) < 0.55 keV at 95% confidence level.Comment: 10 pages, 3 figure

Search for supersymmetry with a dominant R-parity violating LQDbar couplings in e+e- collisions at centre-of-mass energies of 130GeV to 172 GeV

A search for pair-production of supersymmetric particles under the assumption that R-parity is violated via a dominant LQDbar coupling has been performed using the data collected by ALEPH at centre-of-mass energies of 130-172 GeV. The observed candidate events in the data are in agreement with the Standard Model expectation. This result is translated into lower limits on the masses of charginos, neutralinos, sleptons, sneutrinos and squarks. For instance, for m_0=500 GeV/c^2 and tan(beta)=sqrt(2) charginos with masses smaller than 81 GeV/c^2 and neutralinos with masses smaller than 29 GeV/c^2 are excluded at the 95% confidence level for any generation structure of the LQDbar coupling.Comment: 32 pages, 30 figure