Measurements of Magnetic Field Penetration in Superconducting Materials for SRF Cavities

Superconducting radiofrequency (SRF) cavities used in particle accelerators operate in the Meissner state. To achieve high accelerating gradients, the cavity material should stay in the Meissner state under high RF magnetic field without penetration of vortices through the cavity wall. The field onset of flux penetration into a superconductor is an important parameter of merit of alternative superconducting materials other than Nb which can enhance the performance of SRF cavities. There is a need for a simple and efficient technique to measure the onset of field penetration into a superconductor directly. We have developed a Hall probe experimental setup for the measurement of the flux penetration field through a superconducting sample placed under a small superconducting solenoid magnet which can generate magnetic fields up to 500 mT. The system has been calibrated and used to measure different bulk and thin film superconducting materials. This system can also be used to study SIS multilayer coatings that have been proposed to enhance the vortex penetration field in Nb cavities

Evaluation of Anisotropic Magnetoresistive (AMR) Sensors for a Magnetic Field Scanning System for SRF Cavities

One of the significant causes of residual losses in superconducting radio-frequency (SRF) cavities is trapped magnetic flux. The flux trapping mechanism depends on many factors that include cool-down conditions, surface preparation techniques, and ambient magnetic field orientation. Suitable diagnostic tools are not yet available to quantitatively correlate such factors’ effect on the flux trapping mechanism. A magnetic field scanning system (MFSS) consisting of AMR sensors, fluxgate magnetometers, or Hall probes is recently commissioned to scan the local magnetic field of trapped vortices around 1.3 GHz single-cell SRF cavities. In this contribution, we will present results from sensitivity calibration and the first tests of AMR sensors in the MFSS

EIC Crab Cavity Multipole Analysis

Crab cavities are specialized RF devices designed for colliders targeting high luminosities. It is a straightforward solution to retrieve head-on collision with crossing angle existing to fast separate both beams after collision. The Electron Ion Collider (EIC) has a crossing angle of 25 mrad, and will use local crabbing to minimize the dynamic aperture requirement throughout the rings. The current crab cavity design for the EIC lacks axial symmetry. Therefore, their higher order components of the fundamental deflecting mode have a potential of affecting the long-term beam stability. We present here the multipole analysis and preliminary particle tracking results from the current crab cavity design

Estimates of Damped Equilibrium Energy Spread and Emittance in a Dual Energy Storage Ring

A dual energy storage ring design consists of two loops at markedly different energies. As in a single-energy storage ring, the linear optics in the ring design may be used to determine the damped equilibrium emittance and energy spread. Because the individual radiation events in the two rings are different and independent, we can provide analytical estimates of the damping times in a dual energy storage ring. Using the damping times, the values of damped energy spread, and emittance can be determined for a range of parameters related to lattice design and rings energies. We present analytical calculations along with simulation results to estimate the values of damped energy spread and emittance in a dual energy storage ring. We note that the damping time tends to be dominated by the damping time of the high energy ring in cases where the energy of the high energy rings is significantly greater than that of the low energy ring

Beam Dynamics Study in a Dual Energy Storage Ring for Ion Beam Cooling*

A dual energy storage ring designed for beam cooling consists of two closed rings with significantly different energies: the cooling and damping rings. These two rings are connected by an energy recovering superconducting RF structure that provides the necessary energy difference. In our design, the RF acceleration has a main linac and harmonic cavities both running at crest that at first accelerates the beam from low energy E_{L} to high energy E_{H} and then decelerates the beam from E_{H} to E_{L} in the next pass. The purpose of the harmonic cavities is to extend the bunch length in a dual energy storage ring as such a longer bunch length may be very useful in a cooling application. Besides these cavities, a bunching cavity running on zero-crossing phase is used outside of the common beamline to provide the necessary longitudinal focusing for the system. In this paper, we present a preliminary lattice design along with the fundamental beam dynamics study in such a dual energy storage ring

Nb\u3csub\u3e3\u3c/sub\u3eSn Coating of Twin Axis Cavity for Accelerator Applications

A Superconducting twin axis cavity consisting of two identical beam pipes that can accelerate and decelerate beams within the same structure has been proposed for the Energy Recovery Linac (ERL) applications. There are two niobium twin axis cavities at JLab fabricated with the intention of later Nb₃Sn coating and now we are progressing to coat them using vapor diffusion method. Nb₃Sn is a potential alternate material for replacing Nb in SRF cavities for better performance and reducing operational costs. Because of advanced geometry, larger surface area, increased number of ports and hard to reach areas of the twin axis cavities, the usual coating approach developed for typical elliptical single-axis cavities must be evaluated and requires to be adjusted. In this contribution, we report the first results from the coating of a twin axis cavity and discuss current challenges with an outlook for the future

A Hard X-Ray Compton Source at CBETA

Inverse Compton scattering (ICS) holds the potential for future high flux, narrow bandwidth x-ray sources driven by high quality, high repetition rate electron beams. CBETA, the Cornell-BNL Energy recovery linac (ERL) Test Accelerator, is the world’s first superconducting radiofrequency multi-turn ERL, with a maximum energy of 150 MeV, capable of ICS production of x-rays above 400 keV. We present an update on the bypass design and anticipated parameters of a compact ICS source at CBETA. X-ray parameters from the CBETA ICS are compared to those of leading synchrotron radiation facilities, demonstrating that, above a few hundred keV, photon beams produced by ICS outperform those produced by undulators in term of flux and brilliance

Rhinorrhea, cough and fatigue in patients taking sitagliptin

Sitagliptin is a dipeptidyl peptidase-4 (DPP IV, CD26) inhibitor indicated for treatment of Type II diabetes as a second line therapy after metformin. We report fifteen sitagliptin intolerant patients who developed anterior and posterior rhinorrhea, cough, dyspnea, and fatigue. Symptoms typically developed within 1 to 8 weeks of starting, and resolved within 1 week of stopping the drug. Peak expiratory flow rates increased 34% in 8 patients who stopped sitagliptin. Similar changes were found in 4 out of 5 persons who had confirmatory readministration. Chart review identified 17 patients who tolerated sitagliptin and had no symptomatic changes. The sitagliptin intolerant group had higher rates of clinically diagnosed allergic rhinitis (15/15 vs. 6/18; p = 0.00005), Fisher's Exact test) and angiotensin converting enzyme inhibitor - induced cough (6/13 vs. 1/18; p = 0.012). Nasal and inhaled glucocorticoids may control the underlying allergic inflammation and abrogate this new sitagliptin - induced pharmacological syndrome. Potential mucosal and central nervous system mechanisms include disruption of neuropeptides and/or cytokines that rely on DPP IV for activation or inactivation, and T cell dysfunction

Increased Virulence of an Epidemic Strain of Mycobacterium massiliense in Mice

Chronic pulmonary disease and skin/soft tissue infections due to non-tuberculous mycobacteria (NTM) of the Mycobacterium chelonae-abscessus-massiliense group is an emerging health problem worldwide. Moreover, the cure rate for the infections this group causes is low despite aggressive treatment. Post-surgical outbreaks that reached epidemic proportions in Brazil recently were caused by M. massiliense isolates resistant to high-level disinfection with glutaraldehyde (GTA). Understanding the differences in the virulence and host immune responses induced by NTM differing in their sensitivity to disinfectants, and therefore their relative threat of causing outbreaks in hospitals, is an important issue.We compared the replication and survival inside macrophages of a GTA-susceptible reference Mycobacterium massiliense clinical isolate CIP 108297 and an epidemic strain from Brazil, CRM-0019, and characterized the immune responses of IFNγ knockout mice exposed to a high dose aerosol with these two isolates. CRM-0019 replicated more efficiently than CIP 108297 inside mouse bone marrow macrophages. Moreover, the animals infected with CRM-0019 showed a progressive lung infection characterized by a delayed influx of CD4+ and CD8+ T cells, culminating in extensive lung consolidation and demonstrated increased numbers of pulmonary CD4+ Foxp3+ regulatory T cells compared to those infected with the reference strain. Immunosuppressive activity of regulatory T cells may contribute to the progression and worsening of NTM disease by preventing the induction of specific protective immune responses.These results provide the first direct evidence of the increased virulence in macrophages and mice and pathogenicity in vivo of the Brazilian epidemic isolate and the first observation that NTM infections can be associated with variable levels of regulatory T cells which may impact on their virulence and ability to persist in the host