43997367
New generation digital longitudinal feedback system for Duke FEL and HIγS facilities
To cure harmful longitudinal coupled-bunch mode beam instabilities during high-current and multi-bunch beam operations at the Duke free electron laser (FEL) and high intensity gamma-ray source (HIgammaS) facilities, we have been developing a new generation digital bunch-by-bunch longitudinal feedback (LFB) system which is based on an Integrated gigasample processor (iGp-64F). In this paper, we describe the new generation digital longitudinal feedback system for the Duke FEL and HIgammaS facilities.
125287210
THE ALPHA PROJECT AT IU CEEM
The Advanced eLectron and PHoton fAcility (ALPHA) project at Indiana University Center for Exploration of Energy and Matter includes a 50 MeV linac, 100 MeV electron synchrotron ring of 20 m circumference, and a radiation effect experimental area for the external beam line. The ring can also store beam bunches for inverse Compton X-ray source. INTRODUCTION For radiation effect experiments in testing electronic components, electron beams at 40-50 MeV energy are commonly used as energy deposition. Unfortunately, electron beams from linacs have an intrinsic rf bunch structure, which may make it difficult to differentiate from the electronic signals of the devices. Debunching the rf structure will be desirable. Furthermore, a shorter bunch with high charge deposition would also be useful to understand critical sustainability of electronic devices. We thus design a debuncher ring that can debunch the rf structure in a single pass, and has the ability to store multiple-pulses for high intensity short pulse operation as the bunch compressor. THE RING The accelerator is composed of 4 dipoles, 2 gradient damping wigglers, one Lambertson septum, 2 magnetic kickers, one travelling wave kicker, and rf cavity. The accelerator uses the existing dipoles that were constructed for the Cooler Injector Synchrotron [1]. General Layout of the ring The general lay out is shown in Fig. 1: • Each dipole is 2 m in length • Straight section is 3 m in length • Each gradient damping wiggler is 60 cm in length with B1/B=1.9 m. Figure 1 shows the lattice function for the bending radius of wiggler ρw=0.7 m. • Adjusting ρw, the compaction factor and the damping partition of the horizontal plane provides modification of the ring parameters. Table 1: Parameter of the Ring
36152468
Little groups and Maxwell-type tensors for massive and massless particles
The massive and massless representations of four-vectors and Maxwell-type tensors are constructed as bilinear combinations of SL(2,C)-spinors and are evaluated on a unified description upon adopting the group contraction procedure of O(3)-like little group to E(2)-like little group. Contraction of massive particle representations leads to gauge-dependent vectors as well as the gauge-independent state vectors constructed by Weinberg. It is shown that gauge degrees of freedom associated with the translation-like transformations of the E(2)-like little group can be traced to the spinors that undergo spin flips in the infinite-momentum/zero-mass limit.
119099546
Quark number susceptibility with finite chemical potential in holographic QCD
We study the quark number susceptibility in holographic QCD with a finite chemical potential or under an external magnetic field at finite temperature. We first consider the quark number susceptibility with the chemical potential. We observe that approaching Tc from high temperature regime, χq/T2 develops a peak as we increase the chemical potential, which confirms recent lattice QCD results. We discuss this behavior in connection with the existence of the critical end point in the QCD phase diagram. We also consider the quark number susceptibility under the external magnetic field. We predict that the quark number susceptibility exhibits a blow-up behavior at low temperature as we raise the value of the magnetic field. We finally spell out some limitations of our study.
13722156
Enhancement of the ATLAS trigger system with a hardware tracker finder FTK
The existing three-level ATLAS trigger system is deployed to reduce the event rate from the bunch crossing rate of 40 MHz to ~ 200 Hz for permanent storage at the LHC design luminosity of 1034 cm−2 s−1. When the LHC exceeds the design luminosity, the load on the Level-2 trigger system will significantly increase due both to the need for more sophisticated algorithms to suppress background and the larger event sizes. The Fast Tracker is a proposed upgrade to the current ATLAS trigger system that will operate at the full Level-1 accepted rate of 100 kHz and provide high quality tracks at the beginning of processing in the Level-2 trigger, by performing track reconstruction in hardware with massive parallelism of associative memories. The concept design is being advanced and justified with the performance in important physics areas, b-tagging, τ-tagging and lepton isolation. The prototyping with current technology is underway and R&D with new technologies has been started.
14939249
Coupled Harmonic Oscillators and Feynman's Rest of the Universe
According to Feynman, the universe consists of two parts - the system in which we are interested and the rest of the universe which our measurement process does not reach. Feynman then formulates the density matrix in terms of the observable world and the rest of the universe. It is shown that coupled harmonic oscillators can serve as an illustrative example for Feynman's ``rest of the universe.'' It is pointed out that this simple example has far-reaching consequences in many branches of physics, including statistical mechanics, measurement theory, information theory, thermo-field dynamics, quantum optics, and relativistic quantum mechanics. It is shown that our ignorance of the rest of the universe increases the uncertainty and entropy in the system in which we are interested.
54616116
PRECISION FIELD MAPPING SYSTEM FOR CYCLOTRON MAGNET
This paper presents a Hall-probe mapping system for measuring the cyclotron magnet, which has been fabricated for the 13 MeV cyclotron at the Korea Institute of Radiological and Medical Sciences(KIRAMS). The Hall probe are mounted on the precision x-y stage, and maps the magnetic field in the Cartesian coordinates. To reduce the data-acquisition time, the system uses the “flying” mode field mapping method. The data acquisition time for mapping the whole gap-area of the cyclotron magnet is ~ 60 minutes. The relative random fluctuation error during the entire mapping process is under 0.01 %. The field measurement results after correction have indicated that the total phase excursion is less than ±15°.