First Search for Axion-Like Particles in a Storage Ring Using a Polarized Deuteron Beam

Based on the notion that the local dark-matter field of axions or axion-like particles (ALPs) in our Galaxy induces oscillating couplings to the spins of nucleons and nuclei (via the electric dipole moment of the latter and/or the paramagnetic axion-wind effect), we performed the first experiment to search for ALPs using a storage ring. For that purpose, we used an in-plane polarized deuteron beam stored at the Cooler Synchrotron COSY, scanning momenta near 970 MeV/c. This entailed a scan of the spin precession frequency. At resonance between the spin precession frequency of deuterons and the ALP-induced EDM oscillation frequency there will be an accumulation of the polarization component out of the ring plane. Since the axion frequency is unknown, the momentum of the beam and consequently the spin precession frequency were ramped to search for a vertical polarization change that would occur when the resonance is crossed. At COSY, four beam bunches with different polarization directions were used to make sure that no resonance was missed because of the unknown relative phase between the polarization precession and the axion/ALP field. A frequency window of 1.5-kHz width around the spin precession frequency of 121 kHz was scanned. We describe the experimental procedure and a test of the methodology with the help of a radiofrequency Wien filter located on the COSY ring. No ALP resonance was observed. As a consequence an upper limit of the oscillating EDM component of the deuteron as well as its axion coupling constants are provided.Comment: 25 pages, 24 figures, 7 tables, 67 reference

Factors Associated with Revision Surgery after Internal Fixation of Hip Fractures

Background: Femoral neck fractures are associated with high rates of revision surgery after management with internal fixation. Using data from the Fixation using Alternative Implants for the Treatment of Hip fractures (FAITH) trial evaluating methods of internal fixation in patients with femoral neck fractures, we investigated associations between baseline and surgical factors and the need for revision surgery to promote healing, relieve pain, treat infection or improve function over 24 months postsurgery. Additionally, we investigated factors associated with (1) hardware removal and (2) implant exchange from cancellous screws (CS) or sliding hip screw (SHS) to total hip arthroplasty, hemiarthroplasty, or another internal fixation device. Methods: We identified 15 potential factors a priori that may be associated with revision surgery, 7 with hardware removal, and 14 with implant exchange. We used multivariable Cox proportional hazards analyses in our investigation. Results: Factors associated with increased risk of revision surgery included: female sex, [hazard ratio (HR) 1.79, 95% confidence interval (CI) 1.25-2.50; P = 0.001], higher body mass index (fo

Control of stochastic cooling systems

Adjustment of stochastic cooling systems is tedious and time-consuming process, but at the same time it is straightforward and in principle could be made fully automatic. The basic parameters one should consider to set-up a stochastic cooling system are system delay and gain, and optionally a notch-filter’s frequency and attenuation. With proper algorithms the adjustment and control of these parameters could be done to the best accuracy and speed, and proper system layout could allow for maintaining the adjustment during system operation without maintenance stops or beam disturbance. This report presents the developed approach for the automation of control and adjustment of stochastic cooling systems

STOCHASTIC COOLING OF HEAVY IONS IN THE HESR

Due to the Modularized Start Version (MSV) of the FAIR project with the postponed New Experimental Storage Ring (NESR), the High Energy Storage Ring (HESR) became very attractive for experiments with heavy ions. Although the HESR is optimized for the storage of antiprotons it is also well suited for heavy ion beams with slight changes in the optics. Within the MSV only stochastic cooling and no electron cooling will be available, but even the main 2 - 4 GHz stochastic cooling system will be capable to fulfil the beam requirements for heavy ions. Most critical parts of the active elements are the high power amplifiers. The stochastic cooling amplifiers for the HESR will be based on new GaN devices. Nonlinearities of these devices necessitate a dedicated analysis of the use in stochastic cooling systems

Antiproton Acceleration and Deceleration in the HESR

The High Energy Storage Ring (HESR) is a part of the future Facility for Antiproton and Ion Research (FAIR) in Darmstadt. The ring is used for hadron physics experiments with a pellet target and the PANDA detector, and will supply antiprotons of momenta from 1.5 GeV/c to 15 GeV/c. To cover the whole energy range a flexible adjustment of transition energy and the corresponding gamma-t value is foreseen. For Injection and Accumulation of Antiprotons delivered from the CR at a momentum of 3.8 GeV/c (gamma=4.2), the HESR optics will be tuned to gamma-t=6.2. For deceleration down to a momentum of 1.5 GeV/c this optic is suitable as well. Stochastic cooling at an intermediate energy is required to avoid beam losses caused by adiabatic growth of the beam during deceleration. For acceleration to 8 GeV/c (gamma=8.6) the optics will be changed after accumulation of the antiproton beam to gamma-t=14.6. For momenta higher than 8 GeV/c the beam will be debunched at 8 GeV/c, optics will be changed to gamma-t=6.2, and after adiabatic rebunching the beam will be accelerated to 15 GeV/c (gamma=16). Simulations show the feasibility of the described procedures with practically no beam losses