55222920
Simulations of the strong-strong beam-beam interaction in hadron colliders
We develop weighted macro-particle tracking and the Perron-Frobenius operator technique for simulating the time evolution of two beams coupled via the beam-beam interaction. The /spl pi/- and /spl sigma/-modes, with and without a sextupole perturbation, are studied based on the Vlasov-Poisson system. Extending the standard averaging formalism to maps with a small collective force, we derive an approximation to the "kick-rotate" model of our simulation. This eliminates the delta function smoothing in the Vlasov equation, common in many theoretical approaches. Action densities are quasi-equilibria, consistent with simulation, and linearization leads to uncoupled Fourier modes and third-kind integral equations. Extensions to 2-d.o.f. and a flexible general purpose code are being developed.
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.
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.
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].
122076282
Deflection of GeV particle beams by channeling in bent crystal planes of constant curvature
121961325
Simulation of b-jet identification in a non-magnetic detector☆
Abstract The simulation of a silicon microstrip detector at the center of the D0 detector at the Fermilab Tevatron collider is described. The efficiency of a silicon vertex detector for identifying b-quark jets in a “non-magnetic” detector such as D0 is investigated. For a position resolution of 10 μm the gluon/b-jet rejection factor is estimated to be 25 for a b-jet efficiency of 25%. The detection of top quarks in the presence of background from high p T W boson production is studied.
122003047
Silicon drift photodiodes
Abstract Low capacitance photodiodes based on the principle of the solid state drift chamber have been constructred and tested. The devices are based on a cellular design with an anode at the centre of each of five cells allowing electrons liberated by ionisation to drift up to 1 mm to the readout strip. Results on the performance of the detectors, including leakage current, capacitance and drift properties, are presented and compared with simulations. A second series drift photodiodes have been processed which incorporate improvements based on results acquired from the first design. They have leakage currents of a few nA and shorter drift times at the periphery of the drift cells. We present measurements showing the performance of the new devices.
120475830
Physics capabilities of the DO upgrade detector
The D0 detector at Fermilab is being upgraded to meet the demands imposed by high luminosity Tevatron running planned to begin in 1998. The central tracking detectors will be replaced with silicon and scintillating fiber tracking systems inside a solenoidal magnetic field and a preshower detector will be added to aid in electron identification. The design and performance of these systems are described and detailed simulations of the physics capabilities of the upgraded detector are presented. In particular the authors focus on the study of electroweak boson properties and top quark physics and briefly describe the b-physics capabilities.
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.
110084127
A silicon drift photodiode
A low-capacitance photodiode based on the principle of the solid-state drift chamber has been constructed and tested. The device is based on a cellular design with an anode at the center of each of five cells, allowing electrons liberated by ionization to drift up to 1 mm to the readout strip. Two designs were produced with p/sup +/ implant widths of 75 mu m and 85 mu m, respectively, using n-type material of 3.5-k Omega -cm resistivity. The opposite surface is a uniform p-type implant, features matching those of the other surface, and is unmetallized to ensure good photosensitivity. Results on the performance of the detector, including leakage current, capacitance, and drift properties, are presented and compared with simulation results. >