Online Model Server for the Jefferson Lab accelerator

A beam physics model server (Art++) has been developed for the Jefferson Lab accelerator. This online model server is a redesign of the ARTEMIS model server. The need arose from an impedance mismatch between the current requirements and ARTEMIS capabilities. The purpose of the model server is to grant access to both static (machine lattice parameters) and dynamic (actual machine settings) data using a single programming interface. A set of useful optics calculations (R-matrix, orbit fit, etc.) has also been implemented and can be invoked by clients via the model interface. Clients may also register their own dynamic models in the server. The server interacts with clients using the CDEV protocol and data integrity is guaranteed by a relational database (Oracle8i) accessed through a persistence layer. By providing a centralized repository for both data and optics calculations, the following benefits were achieved: optimal use of network consumption, software reuse, and ease of maintenance

Tunnelling in quantum superlattices with variable lacunarity

Quantum fractal superlattices are microelectronic devices consisting of a series of thin layers of two semiconductor materials deposited alternately on each other over a substrate following the rules of construction of a fractal set, here, a symmetrical polyadic Cantor fractal. The scattering properties of electrons in these superlattices may be modeled by using that of quantum particles in piecewise constant potential wells. The twist plots representing the reflection coefficient as function of the lacunarity parameter show the appearance of black curves with perfectly transparent tunnelling which may be classified as vertical, arc, and striation nulls. Approximate analytical formulae for these reflection-less curves are derived using the transfer matrix method. Comparison with the numerical results show their good accuracy.Comment: 12 pages, 3 figure

Nonequilibrium Green's function theory for transport and gain properties of quantum cascade structures

The transport and gain properties of quantum cascade (QC) structures are investigated using a nonequilibrium Green's function (NGF) theory which includes quantum effects beyond a Boltzmann transport description. In the NGF theory, we include interface roughness, impurity, and electron-phonon scattering processes within a self-consistent Born approximation, and electron-electron scattering in a mean-field approximation. With this theory we obtain a description of the nonequilibrium stationary state of QC structures under an applied bias, and hence we determine transport properties, such as the current-voltage characteristic of these structures. We define two contributions to the current, one contribution driven by the scattering-free part of the Hamiltonian, and the other driven by the scattering Hamiltonian. We find that the dominant part of the current in these structures, in contrast to simple superlattice structures, is governed mainly by the scattering Hamiltonian. In addition, by considering the linear response of the stationary state of the structure to an applied optical field, we determine the linear susceptibility, and hence the gain or absorption spectra of the structure. A comparison of the spectra obtained from the more rigorous NGF theory with simpler models shows that the spectra tend to be offset to higher values in the simpler theories.Comment: 44 pages, 16 figures, appearing in Physical Review B Dec 200

Simulation Study on JLEIC High Energy Bunched Electron Cooling

In the JLab Electron Ion Collider (JLEIC) project the traditional electron cooling technique is used to reduce the ion beam emittance at the booster ring, and to compensate the intrabeam scattering effect and maintain the ion beam emittance during the collision at the collider ring. Different with other electron coolers using DC electron beam, the proposed electron cooler at the JLEIC ion collider ring uses high energy bunched electron beam, provided by an ERL. In this paper, we report some recent simulation study on how the electron cooling rate will be affected by the bunched electron beam properties, such as the correlation between the longitudinal position and momentum, the bunch size, and the Larmor emittance

Long-Term Simulations of Beam-Beam Dynamics on GPUs

Future machines such as the electron-ion colliders (JLEIC), linac-ring machines (eRHIC) or LHeC are particularly sensitive to beam-beam effects. This is the limiting factor for long-term stability and high luminosity reach. The complexity of the non-linear dynamics makes it challenging to perform such simulations which require millions of turns. Until recently, most of the methods used linear approximations and/or tracking for a limited number of turns. We have developed a framework which exploits a massively parallel Graphical Processing Units (GPU) architecture to allow for tracking millions of turns in a sympletic way up to an arbitrary order and colliding them at each turn. The code is called GHOST for GPU-accelerated High-Order Symplectic Tracking. As of now, there is no other code in existence that can accurately model the single-particle non-linear dynamics and the beam-beam effect at the same time for a large enough number of turns required to verify the long-term stability of a collider. Our approach relies on a matrix-based arbitrary-order symplectic particle tracking for beam transport and the Bassetti-Erskine approximation for the beam-beam interaction

Incidence of angioedema after initiation of angiotensin-converting enzyme inhibitors in adults with heart failure

Background: Angioedema, a potentially life-threatening adverse event associated with angiotensin-converting enzyme inhibitor (ACEI) use, occurs more often among Black patients than non-Black patients. Specific angioedema incidence rates (IRs) among heart failure (HF) patients initiating an ACEI are limited. Objectives: To provide estimates of angioedema incidence among HF patients initiating an ACEI, particularly among Black patients. Methods: We conducted a retrospective cohort study among adult (≥18 years) patients with HF who initiated ACEI use at 5 health care delivery systems within the Cardiovascular Research Network between July 2015 and May 2019. We required patients to have ≥12 months of continuous medical and prescription drug coverage and no ACEI dispensings in the 1 year before treatment initiation. Our primary outcome was serious angioedema, defined as a primary or secondary diagnosis of ICD-9 code 995.1 (‘Angioneurotic edema not elsewhere classified’) or ICD-10 codes in the T78.3 series (‘Angioneurotic edema’) during hospitalization. Our secondary out-come was ‘any angioedema’, which included serious angioedema and non-serious angioedema that was diagnosed in the outpatient setting. We followed patients from ACEI initiation until first angioedema diagnosis or a censoring event (treatment discontinuation, initiation of another renin-angiotensin-aldosterone system blocking agent, disenrollment, death, or end of 365-day follow-up or study). We calculated crude IRs and exact 95% confidence intervals (CI) for angioedema among HF patients initiating an ACEI. Results: We identified 14 ,241 ACEI users, of which 6,156 (43 .2%)were women and 2,105 (15%) were self-reported Black. Mean age was 70 ± 14 years. We observed 6 serious angioedema events overall (IR: 0.8/1,000 person-years (PYs), 95% CI: 0.3-1.7), with 2 events occurring among Black patients (IR: 1.8/1,000 PYs, 95%CI: 0.2-6.5) and 4 events among non-Black patients (IR: 0.6/1,000PYs, 95% CI: 0.2-1.5). We observed 43 angioedema events overall (IR: 5.4/1,000 PYs, 95% CI: 3.9-7.3), with 21 events occurring among Black patients (IR: 19/1,000 PYs, 95% CI: 11.8-29.1) and 22 events among non-Black patients (IR: 3.2/1,000 PYs, 95%CI: 2.0-4.9). Conclusions: Our estimate of angioedema incidence among HF patients who initiated an ACEI (5.4 events/1,000 PYs) is slightly higher than a previously published estimate (3.3/1,000 PYs) among a similarly-defined population identified through administrative claims data. Similar to prior reports, we found a higher incidence of angioedema, both serious and non-serious, among Black ACEI users than among non-black ACEI users

Control of Synchrotron Radiation Effects During Recirculation With Bunch Compression

Studies of beam quality preservation during recirculation * have been extended to generate a design of a compact arc providing bunch compression with positive momentum compaction ** and control of both incoherent and coherent synchrotron radiation (ISR and CSR) effects using the optics balance methods of diMitri et al.***. In addition, the arc/compressor generates very little micro-bunching gain. We detail the beam dynamical basis for the design, discuss the design process, give an example solution, and provide simulations of ISR and CSR effects. Reference will be made to a complete analysis of micro-bunching effects ****

Search for a new gauge boson in the A′A' Experiment (APEX)

We present a search at Jefferson Laboratory for new forces mediated by sub-GeV vector bosons with weak coupling $\alpha'$ to electrons. Such a particle $A'$ can be produced in electron-nucleus fixed-target scattering and then decay to an $e^+e^-$ pair, producing a narrow resonance in the QED trident spectrum. Using APEX test run data, we searched in the mass range 175--250 MeV, found no evidence for an $A'\to e^+e^-$ reaction, and set an upper limit of $\alpha'/\alpha \simeq 10^{-6}$. Our findings demonstrate that fixed-target searches can explore a new, wide, and important range of masses and couplings for sub-GeV forces.Comment: 5 pages, 5 figures, references adde

The E00-110 experiment in Jefferson Lab's Hall A: Deeply Virtual Compton Scattering off the Proton at 6 GeV

We present final results on the photon electroproduction ($\vec{e}p\rightarrow ep\gamma$) cross section in the deeply virtual Compton scattering (DVCS) regime and the valence quark region from Jefferson Lab experiment E00-110. Results from an analysis of a subset of these data were published before, but the analysis has been improved which is described here at length, together with details on the experimental setup. Furthermore, additional data have been analyzed resulting in photon electroproduction cross sections at new kinematic settings, for a total of 588 experimental bins. Results of the $Q^2$- and $x_B$-dependences of both the helicity-dependent and helicity-independent cross sections are discussed. The $Q^2$-dependence illustrates the dominance of the twist-2 handbag amplitude in the kinematics of the experiment, as previously noted. Thanks to the excellent accuracy of this high luminosity experiment, it becomes clear that the unpolarized cross section shows a significant deviation from the Bethe-Heitler process in our kinematics, compatible with a large contribution from the leading twist-2 DVCS$^2$ term to the photon electroproduction cross section. The necessity to include higher-twist corrections in order to fully reproduce the shape of the data is also discussed. The DVCS cross sections in this paper represent the final set of experimental results from E00-110, superseding the previous publication.Comment: 48 pages, 32 figure