17542978
CSR EFFECTS IN A BUNCH COMPRESSOR: INFLUENCE OF THE TRANSVERSE FORCE AND SHIELDING ∗
We studytheinsuenceofcoherentsynchrotronradiation(CSR) on particle bunches traveling on arbitrary planar or-bits betweenparallelconductingplates whichrepresentthevacuum chamber. Our ultimate goal is to follow the timeevolution of the phase space density distribution by solv-ing the 2D Vlasov-Maxwell (VM) system in the time do-main. In contrast to macroparticle methods, the VM ap-proach has no statistical noise and is better suited to thestudy of microbunching. The Þelds excited by the bunchare computed in the lab frame, while the nonlinear Vlasovequation, formulated in interaction picture, is integrated inthe beam frame using the method of local characteristics(Perron-Frobenius (PF) method). The interaction pictureallows a relatively large step using the Euler method. De-tails of our method can be found in [1] and [2]. The majordifÞculty here is the need for a detailed understanding ofthe support of the phase space density. Here we show re-cent numerical results obtained in our Liouville-Maxwellapproximation (LMA) for the benchmark bunch compres-sor at 5 GeV studied in [3]. We analyze the role played bythe transverse force and the effect of shielding and studythe supportof the phase space density.
2396816
Progress on a Vlasov Treatment of Coherent Synchrotron Radiation from Arbitrary Planar Orbits
We report on our progress in the development of a fully self-consistent Vlasov treatment of coherent synchrotron radiation (CSR) effects on particle bunches traveling on arbitrary planar orbits. First we outline our Vlasov approach and the approximation we are currently studying. Then we discuss recent numerical results for a benchmark model studied extensively with codes by several authors.
189808711
Summary of Coherent Theory and Simulations Session
There were two types of talks which we attempt to summarize. Section 2 discusses the analytical talks and Section 3 the simulation talks. We hope that at least our summary will have the flavor of the session and serve as a reasonable pointer to papers in the proceedings and elsewhere. We take this opportunity to thank the participants of this session for making it an interesting one. The major emphasis in this session was on codes and we have tried to give an overview of basic computational strategies in Section 3 before highlighting the talks.
122076282
Deflection of GeV particle beams by channeling in bent crystal planes of constant curvature
55035317
COMPARISON OF 1D AND 2D CSR MODELS WITH APPLICATION TO THE FERMI @ ELETTRA BUNCH COMPRESSORS
We compare our 2D mean field (Vlasov-Maxwell) treatment of coherent synchrotron radiation (CSR) effects with 1D approximations of the CSR force which are commonly implemented in CSR codes. In our model we track particles in 4D phase space and calculate 2D forces [1]. The major cost in our calculation is the computation of the 2D force. To speed up the computation and improve 1D models we also investigate approximations to our exact 2D force. As an application, we present numerical results for the Fermi{at}Elettra first bunch compressor with the configuration described in [1].
15693839
Self-consistent computation of electromagnetic fields and phase space densities for particles on curved planar orbits
We discuss our progress on the self-consistent calculation of the 4D phase space density (PSD) and electromagnetic fields in a Vlasov-Maxwell formulation. We emphasize coherent synchrotron radiation (CSR) from arbitrary curved planar orbits, with shielding from the vacuum chamber, but space charge forces are naturally included. Our focus on the Vlasov equation will provide simulations with lower numerical/statistical noise than standard PIC methods, and will allow the study of issues such as emittance degradation and microbunching due to space charge and CSR in bunch compressors. The fields excited by the bunch are computed in the lab frame from a new double integral formula. The field formula is derived from retarded potentials by changes of variables. It is singularity-free and requires no computation of retarded times. Ultimately, the Vlasov equation will be integrated in beam frame coordinates using our method of local characteristics. As an important intermediate step, we have developed a "self-consistent Monte Carlo algorithm", and a corresponding parallel code. This gives an accurate representation of the source and will help in understanding the PSD support. In addition we have (1) studied carefully a 2D phase space Vlasov analogue and (2) derived an improved expression of the field of a 1D charge/current distribution which accounts for the interference of different bends and other effects usually neglected. Bunch compressors will be emphasized.
126030076
Measurement of B_s Oscillations and CP Violation Results from D0
We present a measurement of the B{sub s}{sup 0} - B{sub s}{sup 0} oscillation frequency, {Delta}m{sub s}, using a combination of semi-leptonic and hadronic B{sub s} decay candidates selected from data collected by the D0 Experiment at the Fermilab Tevatron. We also present several results on CP violation, including an improved measurement of the B{sub s} CP-violating phase from a flavor-tagged analysis of B{sub s}{sup 0} {yields} J/{psi} + {phi} decays.
110541630
Punch-through currents and floating strip potentials in silicon detectors
Punch-through currents flowing between adjacent p/sup +/ strips on the surface of silicon microstrip drift detectors have been observed. Measurements of the floating strip potential have shown that a p/sup +/ strip acquires a voltage such that the punch-through current and the leakage current are equal and opposite. The factors influencing the threshold for the punch-through effect have been compared with a simple computer model, and the predicted variation with the interstrip gap is found to be in reasonable agreement with measured values for a variety of detectors. >
122654690
Silicon microstrip wedge detectors for the DØ silicon tracker
Abstract The silicon tracking system proposed for the DO upgrade is discussed. The design of “wedge” modules for the forward disk section of the tracker is described. The wedge detectors are double-sided with a stereo angle of ± 15° and a strip pitch of 50 μm. Each strip includes an integrated ac-coupling capacitor and polysilicon bias resistor. First results from recently fabricated prototype wedge detectors are presented.
121294791
Background rates in silicon detectors used in uranium calorimeters
Abstract Ion-implanted silicon diode detectors have been used to establish counting rates from radioactive decays of uranium. The measurements allow the estimation of background counting rates in uranium-silicon calorimeters used in high energy physics experiments.
16901067
W Boson Physics at the Fermilab Tevatron
We present electroweak physics results from the D0 and CDF experiments using data from p \bar p collisions at \sqrt s = 1.8 TeV. Measurements of the cross sections times branching ratios for W and Z production, the inclusive width of the W boson and the W boson mass are presented. Direct tests of the WW\gamma and WWZ trilinear gauge boson couplings are also presented based on studies of diboson production.