67811641
ENERGY SPREAD ISSUE IN LASER UNDULATOR BASED XFELs
At the Center for the Exploration of Energy and Matter (CEEM) in Indiana University, we have been developing a new XFEL concept, which is based on inverse Compton scattering and a laser undulator instead of the conventional magnetic undulator. In this paper, we report an estimation of the energy spread growth in the electron storage ring due to the inverse Compton scattering itself and their impacts on the FEL lasing in the laser undulator based XFEL concept.
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.
55217395
DESIGN OF INJECTION AND EXTRACTION BEAMLINES FOR THE ALPHA PROJECT
The ALPHA facility consists of an electron linac and an electron storage ring to provide uniform intense beams for radiation test, and it has a potential to be a future X-Ray source. The ring uses four dipoles from the Cooler Injection Synchrotron (CIS) [1], which was constructed for proton acceleration from 7 MeV to 240 MeV. The circumference of the ALPHA storage ring is 20 m, and its lattice has an adjustible momentum compaction factor by changing the field strength of a pair of gradient damping wigglers [2]. For the proof of working principles, we use a refurbished 20 MeV CLINAC as the injector. The CLINAC will be upgraded to a 50 MeV linac by the end of 2011. Two operation modes (debunching and accumulation modes) [3] are currently planned for the ALPHA facility. For the debunching mode, two magnetic kickers are located at symmetric positions with respect to the Lambertson magnet. When the magnetic kickers are turned at 24 mrad, the closed orbit of the storage ring passes through the Lambertson magnet, and thus the injected beam is extracted in a single pass. In this case, the storage ring can be considered as a big α– magnet for debunching. For the beam accumulation mode, the magnetic kicker’s power supply is designed to have 500 ns decay time (beam revolution time in ring is 66 ns). The closed orbit is gradually moved back to designed orbit during injection so that multi-turn accumulation can be achieved in this way. In this paper, we describe the design concepts of the injection and extraction beamlines to maximize beam transport and to satisfy desired beam properties.
11157984
Growth time of the longitudinal coupled bunch mode beam instability at the Duke FEL facility
To determine the required power of an amplifier for the longitudinal feedback (LFB) system, the growth time of the strongest longitudinal coupled bunch mode instability (CBMI) in the Duke storage ring should be measured in advance. In 2005, we measured strength of the strongest longitudinal beam instability in the Duke storage ring with four and eight symmetrically filled buckets. By analyzing measured data, the growth time of the strongest dipole mode of the longitudinal CBMI in the Duke storage ring can be estimated. At a beam energy of 274 MeV, the growth time is about 0.365 ms for a total stored beam current of 160 mA. From the measured growth time, we estimated the required power of the amplifier for the LFB system. To damp all harmful longitudinal CBMIs with an energy deviation of 0.1 % (rms) within its growth time of 0.365 ms, we have to supply about HOW (rms) to an LFB kicker whose a central frequency is 937.3875 MHz. In this paper, we describe the growth time of the longitudinal CBMI at the Duke storage ring and the estimation of the required power for the LFB system to damp all CBMIs within 0.365 ms.
121093451
Stable operation of a self-amplified spontaneous-emission free-electron laser in the extremely ultraviolet region
121568105
PRECISION ELECTROWEAK PHYSICS
56009963
Single bunch collective effects in PLS storage ring
The single bunch collective effects such as the bunch lengthening due to the potential well distortion and the microwave instability which also increases the energy spread, the transverse head-tail instability, and the transverse strong head-tail instability are investigated in the Pohang Light Source storage ring. The threshold current and the Chao-Gareyte scaling factor of the bunch lengthening, the longitudinal broadband impedance, and the transverse impedance have been measured and compared with the ZAP code results.
117941616
Lorentz Group derivable from Polarization Optics 1
The Lorentz group is the fundamental language for space-time symmetries of relativistic particles. This group can these days be derived from the symmetries observed in other branches of physics. It is shown that this group can be derived from optical filters. The group O(2,1) is appropriate for attenuation filters, while the O(3) group describes phase-shift filters. The combined operation leads to a two-by-two representation of the six-parameter Lorentz group. It is shown also that the bilinear representation of this group is the natural language for the polarization optics. The Lorentz group serves useful purposes in many branches of physics. In this note, we would like to show that the bilinear representation of the six-parameter Lorentz group [1] is the natural language for polarization of light waves. In studying polarized light propagating along the z direction, the traditional approach is to consider the x and y components of the electric fields. Their amplitude ratio and the phase difference determine the degree of polarization. Thus, we can change the polarization either by adjusting the amplitudes, by changing the relative phase shift, or both. For convenience, we call the optical device which changes amplitudes an “attenuator,” and the device which changes the relative phase a “phase shifter.” Let us write the electric field vector as
14379054
Covariant Model of Relativistic Extended Particles based on the Oscillator Representation of the Poincaré Group
While internal space-time symmetries of relativistic particles are dictated by the little groups of the Poincaré group, it is possible to construct representations of the little group for massive particles starting from harmonic oscillator wave functions for the quark model. The resulting oscillator wave functions are covariant and can be Lorentz-boosted. It is thus possible to obtain the parton model by boosting the quark model. A review of Wigner's theory of the little groups is given. It is shown that the covariant oscilla-tor wave functions become squeezed as as the system becomes boosted. It is shown also that the Lorentz-squeezed quark distribution exhibits the peculiarities of Feynman's parton model including the lack of coherence in the calculation of cross sections. A historical review of the concept of covariance is given.
118715122
Physics from Tristan
The TRISTAN e + e − storage ring has delivered a total of about 60 pb−1 to each of the three general purpose solenoidal detectors: AMY, TOPAZ and VENUS. The center-of-mass energy range, between 50 and 64 GeV, is where interference effects between the virtual photon and Z0 mediators of the annihilation process are largest. Experiments at TRISTAN study the electroweak interactions, QCD, and search for new phenomena. Among the reported results are: measurements of R; the observation of forward-backward charge asymmetries for e+e− → lepton pairs, \(e^ + e^ - \to b\bar b\), and \(e^ + e^ - \to q\bar q\); limits on lepton compositeness; determinations of \(\Lambda _{\overline {MS} }\); measurements of various multihadron event properties; evidence for differences between quark and gluon jets; the demonstration of the running of αs and the existence of the triple-gluon coupling; and searches for a variety of new particles. This report describes a few selected results from the AMY experiment.