Compact storage ring to search for the muon electric dipole moment

We present the concept of a compact storage ring of less than 0.5 m orbit radius to search for the electric dipole moment of the muon ($d_\mu$) by adapting the "frozen spin" method. At existing muon facilities a statistics limited sensitivity of d_\mu \sim 5 \times 10^{-23} \ecm can be achieved within one year of data taking. Reaching this precision would demonstrate the viability of this novel technique to directly search for charged particle EDMs and already test a number of Standard Model extensions. At a future, high-power muon facility a statistical reach of d_\mu \sim 5 \times 10^{-25} \ecm seems realistic with this setup.Comment: improved for submission; minor modification

Beam Dynamics in High Intensity Cyclotrons Including Neighboring Bunch Effects: Model, Implementation and Application

Space charge effects, being one of the most significant collective effects, play an important role in high intensity cyclotrons. However, for cyclotrons with small turn separation, other existing effects are of equal importance. Interactions of radially neighboring bunches are also present, but their combined effects has not yet been investigated in any great detail. In this paper, a new particle in cell based self-consistent numerical simulation model is presented for the first time. The model covers neighboring bunch effects and is implemented in the three-dimensional object-oriented parallel code OPAL-cycl, a flavor of the OPAL framework. We discuss this model together with its implementation and validation. Simulation results are presented from the PSI 590 MeV Ring Cyclotron in the context of the ongoing high intensity upgrade program, which aims to provide a beam power of 1.8 MW (CW) at the target destination

Towards Quantitative Simulations of High Power Proton Cyclotrons

PSI operates a cyclotron based high intensity proton accelerator routinely at an average beam power of 1.3MW. With this power the facility is at the worldwide forefront of high intensity proton accelerators. The beam current is practically limited by losses at extraction and the resulting activation of accelerator components. Further intensity upgrades and new projects aiming at an even higher average beam power, are only possible if the relative losses can be lowered in proportion, thus keeping absolute losses at a constant level. Maintaining beam losses at levels allowing hands-on maintenance is a primary challenge in any high power proton machine design and operation. In consequence, predicting beam halo at these levels is a great challenge and will be addressed in this paper. High power hadron driver have being used in many disciplines of science and, a growing interest in the cyclotron technology for high power hadron drivers are being observed very recently. This report will briefly introduce OPAL, a tool for precise beam dynamics simulations including 3D space charge. One of OPAL's flavors (OPAL-cycl) is dedicated to high power cyclotron modeling and is explained in greater detail. We then explain how to obtain initial conditions for our PSI Ring cyclotron which still delivers the world record in beam power of 1.3 MW continuous wave (cw). Several crucial steps are explained necessary to be able to predict tails at the level of 3\sigma ... 4\sigma in the PSI Ring cyclotron. We compare our results at the extraction with measurements, obtained with a 1.18 MW cw production beam. Based on measurement data, we develop a simple linear model to predict beam sizes of the extracted beam as a function of intensities and confirm the model with simulations.Comment: Corrections and new figur

Large anisotropic uniaxial pressure dependencies of Tc in single crystalline Ba(Fe0.92Co0.08)2As2

Using high-resolution dilatometry, we study the thermodynamic response of the lattice parameters to superconducting order in a self-flux grown Ba(Fe0.92Co0.08)2As2 single crystal. The uniaxial pressure dependencies of the critical temperature of Tc, calculated using our thermal expansion and specific heat data via the Ehrenfest relation, are found to be quite large and very anisotropic (dTc/dpa = 3.1(1) K/GPa and dTc/dpc = - 7.0(2) K/GPa). Our results show that there is a strong coupling of the c/a ratio to superconducting order, which demonstrates that Tc is far from the optimal value. A surprising similarity with the uniaxial pressure effects in several other layered superconductors is discussed.Comment: 11 pages, 4 Figure

Electrical Detection of Spin Accumulation at a Ferromagnet-Semiconductor Interface

We show that the accumulation of spin-polarized electrons at a forward-biased Schottky tunnel barrier between Fe and n-GaAs can be detected electrically. The spin accumulation leads to an additional voltage drop across the barrier that is suppressed by a small transverse magnetic field, which depolarizes the spins in the semiconductor. The dependence of the electrical accumulation signal on magnetic field, bias current, and temperature is in good agreement with the predictions of a drift-diffusion model for spin-polarized transport.Comment: Submitted to Phys. Rev. Let